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1

An introduction to Radar Absorbent Materials (RAM)  

Microsoft Academic Search

The electromagnetic principles of radar absorbent materials are summarized. The fundamental theory of electromagnetic wave propagation in media and at the interfaces between different media is reviewed, and approaches to absorber design are described. The types of materials required and the techniques for measuring their electromagnetic properties and the performance of the finished absorber are outlined. A means of designing

P. G. Lederer

1986-01-01

2

Trends in radar absorbing materials technology  

Microsoft Academic Search

The research in the area of Radar Absorbing Materials (RAMs) has been actively pursued for at least four decades. Although\\u000a resonant RAMs were originally designed by transmission line approach, and the broad band RAMs were obtained by multilayering,\\u000a the quest for ultrawide band performance has led to novel approaches such as chirality and even exploring biochemical products.\\u000a It is observed

K J Vinoy; R M Jha

1995-01-01

3

Experiment research on MM wavelength radar absorbing materials  

Microsoft Academic Search

Experiments to obtain high quality millimeter wavelengths radar absorbing materials are discussed. In order to obtain the best mixing proportion of materials, a great number of materials had been investigated. Several absorbing coating materials achieving this aim are found

Chen ZhiPing; Zhu Qi; Xu Shan-Jia

1999-01-01

4

A simple measuring method of reflectivity for radar absorbing material  

Microsoft Academic Search

The basic principle of measuring reflectivity for radar absorbing material (RAM) is analyzed. And a simple method for measuring reflectivity of radar absorbing material using vector network analyzer HP8722ET and APC-7mm coaxial line is presented. The results indicate that the reflectivity of the radar absorbing material can be measured in 0.05-18 GHz using this method. Under the ordinary laboratory condition,

Feng Yongbao; Qiu Tai; Shen Chunying; Li Xiaoyun

2005-01-01

5

CFRP-based broad-band Radar Absorbing Materials  

Microsoft Academic Search

Strong interest in radar absorbing materials (RAMs) took place with years due to their extensive sectors of application. RAMs are coatings whose electric and magnetic properties allow the absorption of microwave energy over certain frequencies. In particular, RAMs are very effective means of Radar Cross Section (RCS) reduction in the context of stealth technology. RCS reduction requires absorbers with broad-band

C. Mitrano; A. Balzano; M. Bertacca; M. Flaccavento; R. Mancinelli

2008-01-01

6

Properties of Propagation of Electromagnetic Wave in a Multilayer Radar-Absorbing Structure With Plasma and Radar-Absorbing Material  

Microsoft Academic Search

A multilayer radar-absorbing structure with plasma- and radar-absorbing material (RAM) is established to investigate the stealth mechanisms of the multilayer absorber. The method of impedance transformation with multiple dielectrics is used to analyze the propagation of electromagnetic (EM) waves in the multilayer structure. The dependences of EM waves attenuation on the parameters of the plasma and RAMs are provided. The

Cheng-Xun Yuan; Zhong-Xiang Zhou; Jingwen W. Zhang; Xiao-Li Xiang; Yue Feng; Hong-Guo Sun

2011-01-01

7

Radar absorbing materials used for target camouflage  

Microsoft Academic Search

As a result of the developments within signal processing, transmitters and receivers areas radar technology has improved steadily over the past 50 years gaining in the sensor sensitivity, miniaturisation, power consumption, etc which allow to build smaller, more reliable and user friendly radar sensors. The effectiveness of these radar sensors is sufficiently threatening to merit the reduction of radar signature

I. NICOLAESCU

2006-01-01

8

Radar absorbing material (RAM) and shaping on radar cross section reduction of dihedral corners  

Microsoft Academic Search

How far can a radar system detect an object depends the radar cross section (RCS) of the target. Corner reflectors are the major scattering centers in the radar signatures of vehicles. The monostatic return from such structures can be reduced by ensuring that surfaces never meet at right angles and by application of radar absorbing materials (RAM). This paper deals

G. G. Peixoto; A. L. de Paula; L. A. Andrade; C. M. A. Lopes; M. C. Rezende

2005-01-01

9

Application of Impedance Loading to Geometric Transition Radar Absorbent Material  

Microsoft Academic Search

This paper describes a novel, lightweight technique for significantly improving the low-frequency reflectivity performance of conventional geometric transition radar absorbent materials as used typically in anechoic chamber facilities for electromagnetic compatibility testing. The improvement is achieved by the inclusion of impedance-loading elements within the base region of the absorber, and these are implemented in the form of one or more

Kenneth Lee Ford; Barry Chambers

2007-01-01

10

Skin collagen fiber-based radar absorbing materials  

Microsoft Academic Search

By using skin collagen fiber (CF) as raw material, Schiff base structure containing CF (Sa-CF) was synthesized through CF-salicylaldehyde\\u000a reaction. Then a novel radar absorbing material (Fe-Sa-CF) was prepared by chelating reaction between Sa-CF and Fe3+. The coaxial transmission and reflection method was used to analyze the complex permittivity and complex magnetic permeability\\u000a of these CF-based materials, and the radar

YiShan Liu; Xin Huang; PeiPei Guo; XuePin Liao; Bi Shi

2011-01-01

11

Monostatic Reflectivity Measurement of Radar Absorbing Materials at 310 GHz  

Microsoft Academic Search

This paper presents monostatic reflectivity measurements of radar absorbing materials at 310 GHz in a phase-hologram-based compact range. The radar cross-section method was used and the backscattered reflection was measured with horizontal and vertical polarizations in plane-wave conditions. Transmission was also studied. The reflectivity was measured over an incidence angle of 0deg-45deg. The reflectivity of Thomas Keating Terahertz RAM at

Anne Lönnqvist; Aleksi Tamminen; Juha Mallat; Antti V. Räisänen

2006-01-01

12

Radar cross-section analysis of wind turbine blades with radar absorbing materials  

Microsoft Academic Search

Wind turbines interfere with radar systems due to their large radar cross-section (RCS) and the rotation of the blades. Applying radar absorbing materials (RAM) is considered as a possible mitigation measure. This paper will present RCS modeling results of a generic 40 meters blade. The blade is segmented into 4 sections and the monostatic scattering from each section is modeled.

L. S. Rashid; A. K Brown

2011-01-01

13

Electromagnetic behavior of radar absorbing materials based on conducting polymers  

Microsoft Academic Search

The efficiency of recently developed RAM (Radar Absorbing Materials) based on conducting polymers in sheet texture has been investigated by X-band (8 to 12 GHz) scattering measurements and, also by determination of their complex dielectric constant by a waveguide method. This paper presents the experimental methodology used to characterize RAM based on a conducting polymer called polyaniline. The correlation between

M. Franchitto; R. Faez; A. J. F. Orlando; M. C. Rezende; I. M. Martin

2001-01-01

14

Conducting-polymer-based radar-absorbing materials  

Microsoft Academic Search

The controllability of conductivity and the ease of manufacturing\\/coating of conducting polymers enable tailor- made dielectric loss components for radar absorbing materials (RAM). Different polypyrrole (PPy) based RAM, e.g. paint\\/rubber containing PPy powder and PPy coated structural phenolic foams with a gradient of impedance, have been examined. Reflection loss strongly depends on thickness and complex permittivity of the material. For

Van-Tan Truong; Ben D. Turner; Richard F. Muscat; M. S. Russo

1997-01-01

15

The optimizing research about radar absorbent material parameters  

Microsoft Academic Search

From the Physical Optics theory (PO) and Leontovich Impedance Boundary Condition (IBC), We research RCS reduction (RCSR) of\\u000a multilayer dielectric and magnetic medium on different shape conductors such as plate, cuboid and cone by use of Matlab programs.\\u000a Some available RCS data and graph results are given. These show the connection between Radar Absorbent Material (RAM) parameters\\u000a and the number

Zhang Chang-jiang; Lu Shu; Xu Peng-geng

1999-01-01

16

Experimental investigation of impulse radar for mitigation of effects of radar absorbing materials  

Microsoft Academic Search

This article uses experimental methods from the two areas of frequency-domain and time-domain to investigate electromagnetic scattering associated with targets coated with wave absorbent materials. Results clearly show that UWB signals have a 10-12dB advantage coping with targets coated with wave absorbent materials as compared to the narrow band signals of conventional radar. The explanation is that ultra wide waveband

He Jianguo; Lu Zhongliang; Su Yi

1995-01-01

17

Experimental investigation of impulse radar for mitigation of effects of radar absorbing materials  

Microsoft Academic Search

The response of a UWB signal acting on coating radar absorbing material (RAM) targets have been investigated experimentally by the time-domain method and the frequency-domain method. It is shown that the UWB signal is 10-12 dB superior to the narrowband signal of conventional radar for anti-coating RAM targets. It has been clearly indicated that the UWB signal has good capabilities

Jianguo He; Zhongliang Lu; Yi Su

1992-01-01

18

Conducting-polymer-based radar-absorbing materials  

NASA Astrophysics Data System (ADS)

The controllability of conductivity and the ease of manufacturing/coating of conducting polymers enable tailor- made dielectric loss components for radar absorbing materials (RAM). Different polypyrrole (PPy) based RAM, e.g. paint/rubber containing PPy powder and PPy coated structural phenolic foams with a gradient of impedance, have been examined. Reflection loss strongly depends on thickness and complex permittivity of the material. For a single layer material, the optimum values of the real part, (epsilon) ', and imaginary part, (epsilon) ", of the complex permittivity required to achieve a minimum reflectivity at a given sample thickness are found by theoretical calculations. The conductivity of the PPy powder is controlled to obtain RAM with lowest reflectivity according to the calculated optimum values of (epsilon) ' and (epsilon) ". A paint panel containing 2 wt% of the PPy powder with a thickness of 2.5 mm exhibits a reflectivity less than $minus 10 dB over 12 to 18 GHz. Blending and milling in the manufacturing process can destroy the original fibrous shape of PPy aggregates leading to low absorbing performances. PPy can be coated on rigid or flexible open cell foams to provide a lightweight broadband RAM. In particular, a coating technique on phenolic foams (12 - 15 mm thick) with a pore size of micrometer order has been developed to generate a gradient of conductivity across the foam thickness. The PPy coated foams are broadband RAM.

Truong, Vo-Van; Turner, Ben D.; Muscat, Richard F.; Russo, M. S.

1997-11-01

19

Design radar absorbing materials (RAMs) for wide range of angles of incidence  

Microsoft Academic Search

Usually radar absorbing materials (RAMs) for electromagnetic compatibility (EMC) applications absorb radio frequency (RF) energy at a specified rate at nearly normal angles of incidence. However, there are applications where RAM is required to perform at angles greater than 30° from normal incidence where a portion of the RF energy is scattered instead of being absorbed. This scattered energy has

Jose Perini; L. S. Cohen

1991-01-01

20

Simulations of the radar cross section of a generic air-to-air missile coated with radar absorbing materials  

Microsoft Academic Search

Simulations of the radar cross section of a heat- seeking air-to-air missile model were performed using the CADRCS software. In these simulations at a frequency of 10 GHz, the surface of the missile was considered to be a perfect conductor and to be coated with a radar absorbing material (RAM). The comparison of results from the simulations shows how different

Mauro A. Alves; Guilherme G. Peixoto; Mirabel C. Rezende

2007-01-01

21

Radar cross section measurements (8-12 GHz) of flat plates painted with microwave absorbing materials  

Microsoft Academic Search

The aim of the present work is to present radar cross section measurements of flat plates painted with radar absorbing material (RAM) in the range of 8-12 GHz. The measurements were carried out in an anechoic chamber at Centro Tecnico Aeroespacial (CTA)-Ministerio da Defesa facilities, and the RAM coating was manufactured at Divisao de Materiais of Instituto de Aeronautica e

M. C. Rezende; I. M. Martin; M. A. S. Miacci; E. L. Nohara

2001-01-01

22

Computation of RCS from a flat plate covered with radar absorbing material  

Microsoft Academic Search

Since the early 1980s, the electromagnetic stealth technique has been developed for reducing the radar cross section (RCS) of aircraft based on two principal methods. One is to cover the aircraft with a radar absorbing material (RAM), the other is to modify the aircraft shape. The scattering from an arbitrary flat plate of electrically large dimensions and coated with a

Liang Chao Wu; Wen Xun Zhang; Mao Guang Wang

1995-01-01

23

Monostatic Reflectivity and Transmittance of Radar Absorbing Materials at 650 GHz  

Microsoft Academic Search

Transmittance and monostatic reflectivity of different radar absorbing materials at 650 GHz are presented. The reflectivity was measured in plane-wave conditions in a radar cross-section (RCS) range with vertical polarization. The lowest reflectivity level (-70 dB) was achieved with commercial absorbers TK THz RAM and Firam-500 with oblique incidence angles. Floor carpets were also studied, and the reflectivity level of

Aleksi Tamminen; Anne Lonnqvist; Juha Mallat; Antti V. Raisanen

2008-01-01

24

A New Approach to the Design of Low Frequency Radar Absorbent Materials  

Microsoft Academic Search

This paper describes a new approach to improving the low frequency reflectivity performance of geometric transition radar absorbent materials through the use of impedance loading in the form of one or more FSS layers which are incorporated into the absorber base layer. The discussion includes theoretical predictions and measured data on unmodified and modified commercially available RAM which confirm the

K. L. Ford; B. Chambers

2007-01-01

25

RAT SCAT evaluation of commercially available radar absorbing materials, volume 1  

Microsoft Academic Search

This report summarizes performance evaluation tests on a variety of commercially available thin flexible sheet type radar absorber materials, including both resonant and non-resonant types. A corner reflector test technique was used which allowed test and evaluation of the absorber at both normal incidence and grazing angles out to ninety (90) degrees. Fourteen types of RAM were tested at frequencies

W. Ohara

1976-01-01

26

Measurements of the permittivity and permeability of thin radar absorber materials in waveguides  

Microsoft Academic Search

The reflection-transmission (RT) method offers many advantages for measuring the properties of various types of materials. However, for very thin and lossy sheets, there are some practical problems. To overcome some of these problems, we proposed the use of a two-layer structure for the measurement of radar absorber materials (see Williams, T. et al., IEEE Antennas and Propagation Int. Symp.

T. Williams; M. A. Stuchly; P. Saville

2002-01-01

27

A smart radar absorber  

Microsoft Academic Search

This paper proposes a configuration for a smart radar absorber which is capable of both self-tuning and absorb while scan operation. The discussion is complemented by modelled and measured performance data.

Barry Chambers

1999-01-01

28

APPLICATION OF DOUBLE ZERO METAMATERIALS AS RADAR ABSORBING MATERIALS FOR THE RE DUCTION OF RADAR CROSS SECTION  

Microsoft Academic Search

We introduce and investigate the applications of double zero (DZR) metamaterials (having the real parts of permittivity and permeability equal to zero) as radar absorbing materials (RAMs). We consider a perfectly electric conductor (PEC) plate covered by several layers of DZR metamaterial coatings under an oblique plane wave incidence of arbitrary polarization. Several analytical formulas are derived for the realization

H. Oraizi; A. Abdolali; N. Vaseghi

2010-01-01

29

Microwave absorption properties of the carbonyl iron\\/EPDM radar absorbing materials  

Microsoft Academic Search

Employing carbonyl iron powder and Ethylene-Propylene-Diene Monomer (EPDM) as the absorbent and matrix, rubber radar absorbing\\u000a materials (RAM) were prepared. Effects of the carbonyl iron volume fraction and the thickness of the RAM on the microwave\\u000a absorption properties in the frequency range of 2.6–18GHz were studied, and a mathematical analysis was made using the electromagnetic\\u000a theory. The experimental results indicate

Yongbao Feng; Tai Qiu; Xiaoyun Li; Chunying Shen

2007-01-01

30

RCS Reduction of Ridged Waveguide Slot Antenna Array Using EBG Radar Absorbing Material  

Microsoft Academic Search

This letter investigates the application of EBG radar absorbing material (RAM) to asymmetric ridged waveguide slot antenna array to reduce its backward RCS. The EBG RAM is based on the mushroom-like EBG structure loaded with lumped resistances. A ridged waveguide slot antenna array with 4 times 10 slot elements was designed and built, part of the metal ground plane of

You-Quan Li; Hui Zhang; Yun-Qi Fu; Nai-Chang Yuan

2008-01-01

31

On the Design of Radar Absorbing Materials Using Left-Handed Transmission Line  

Microsoft Academic Search

A novel radar absorbing material is designed by combining a high impedance surface and a transitional structure. The high impedance surface consists of a two-dimensional periodic array of unit cells that are implemented using a left-handed transmission line printed on a dielectric substrate with lumped elements. A transition between free space and the vertically placed microstrip line is designed using

Hang Wang; Wei Tang; Zhongxiang Shen

2007-01-01

32

Strong fluctuation theory for effective electromagnetic parameters of fiber fabric radar absorbing materials  

Microsoft Academic Search

A method with the strong fluctuation theory to calculate the effective electromagnetic parameters of fiber fabric radar absorbing materials (RAM) is showed in this paper. The effective electromagnetic parameters are imperative to design RAM of fiber fabric. Considering anisotropic structure, we attain the plural integral equations to get the electromagnetic parameters with the strong fluctuation theory. Finally, we design a

Zhi-Hui Peng; Mao-Sheng Cao; Jie Yuan; Gang Xiao

2004-01-01

33

Design of broad-band radar-absorbing materials for large angles of incidence  

Microsoft Academic Search

A numerical technique, called the (modified) Powell method, is used to design radar-absorbing materials (RAMs) made up of several dielectric layers, usually on top of a conducting (ground) plane. The absorption of RF energy occurs mostly in the last layer. The other layers are used to match the wave impedance of the RAM to that of the medium on which

J. Perini; Lawrence S. Cohen

1993-01-01

34

The use of a vector network analyzer for measuring the performance of radar absorbing materials  

Microsoft Academic Search

Testing the performance of Radar Absorbing Materials (RAM) is often a difficult task and in most cases the manufacturer's specifications are the only source of performance data. This paper presents a method of measuring the normal reflection coefficient of planar RAM using a Hewlett-Packard 8510A Vector Network Analyzer and a small horn antenna. The Vector Network Analyzer is used to

Jeffrey Stanier

1991-01-01

35

Preparation and study on radar absorbing materials of nickel-coated carbon fiber and flake graphite  

Microsoft Academic Search

Radar absorbing materials of nickel-coated carbon fiber (NCF) and nickel-coated flake graphite (NFG) were fabricated by electroless plating. Sufficient activation sites were vital to deposit a continuous and uniform coating layer. The morphology of the CF (FG) and NCF (NFG), Pd element content on the CF surface, the element components and the phases in the coating layer, magnetic properties of

Yuzun Fan; Haibin Yang; Xizhe Liu; Hongyang Zhu; Guangtian Zou

2008-01-01

36

Performance evaluation of conducting polymer paints as radar absorbing materials (RAM)  

Microsoft Academic Search

The efficiency and performance of recently developed RAM (radar absorbing materials) based on conducting polymer paints has been investigated in the range of 8-12 GHz. The used conducting polymer in the paint formulations is the polyaniline doped with two different acids: dodecylbenzene sulfonic acid (DBSA), and camphorsulfonic acid (CSA). In practice, RAM ought to be effective over a range of

R. S. Biscaro; E. L. Nohara; G. G. Peixoto; R. Faez; M. C. Rezende

2003-01-01

37

Electromagnetic and absorption properties of carbonyl iron\\/rubber radar absorbing materials  

Microsoft Academic Search

We measured the effective complex magnetic permeability ?eff* and dielectric permittivity ?eff* spectra in rubber radar absorbing material (RAM) with various carbonyl iron volume fractions by using the transmission\\/reflection method with a vector network analyzer. We studied the effects of carbonyl iron content and rubber thickness on the microwave absorption properties in the frequency range of 2.6 to 18 GHz.

Yong-Bao Feng; Tai Qiu; Chun-Ying Shen; Xiao-Yun Li

2006-01-01

38

Fundamental limit on the performance of radar absorbing materials  

Microsoft Academic Search

There is a fundamental limit on the absorption-bandwidth integral that can be achieved by the use of frequency-dependent materials on a conducting backplane, proportional to the thickness of the structure, and to its magnetic permeability. The limit arises because the materials must be causal and passive. The value of the limit has been obtained by analytic calculation and verified by

C. R. Brewitt-Taylor

1999-01-01

39

Optimization of radar absorbing material with the CAD software TOUCHSTONE  

Microsoft Academic Search

The modeling and optimization of multilayer materials in free space by TOUCHSTONE are described. These materials may be composed of lossy dielectric, resistive sheet, and frequency selective surface. Simulation results are presented for a Dallenbach screen and for a frequency selective surface inserted in a lossy dielectric. The examples presented show that it is possible to simulate and optimize many

E. Marouby; J. P. Gouy; J. R. Levrel; P. Decouvreur

1992-01-01

40

Thin Wideband Radar Absorbers  

Microsoft Academic Search

A procedure for the optimal design of thin wideband radar absorbers is presented. The resulting absorbers are implemented by printing a frequency selective surface on a lossy perforated substrate. A binary hill climbing optimization scheme with random restart is used to find optimal solutions. The method of moments in conjunction with the transmission line method is used to calculate the

Arya Fallahi; Alireza Yahaghi; Hans-Rudolf Benedickter; Habibollah Abiri; Mahmoud Shahabadi; Christian Hafner

2010-01-01

41

The design of broadband radar absorbing surfaces  

Microsoft Academic Search

There has been a growing and widespread interest in radar absorbing material technology. As the name implies, radar absorbing materials or RAM's are coatings whose electric and magnetic properties have been selected to allow the absorption of microwave energy at discrete or broadband frequencies. In military applications low radar cross section (RCS) of a vehicle may be required in order

Go H. Suk

1990-01-01

42

Interaction of Electromagnetic Waves with Two-Dimensional Metal Covered with Radar Absorbing Material and Plasma  

Microsoft Academic Search

A two-dimensional metal model is established to investigate the stealth mechanisms of radar absorbing material (RAM) and plasma when they cover the model together. Using the finite-difference time-domain (FDTD) method, the interaction of electromagnetic (EM) waves with the model can be studied. In this paper, three covering cases are considered: a. RAM or plasma covering the metal solely; b. RAM

Chaohui Lan; Xiwei Hu; Zhonghe Jiang

2008-01-01

43

Radar Absorbing Applications of Metamaterials  

Microsoft Academic Search

Radar absorbing materials (RAM) is used to camouflage or shield highly reflective surfaces such metallic surfaces from incident electromagnetic (EM) waves. In this paper, we explore the applications of metamaterials as conformal RAM coatings for controlling the reflection of EM waves from metal surfaces. Metamaterials are engineered materials with specially designed metallic resonant structures that are much smaller than the

Vasundara V. Varadan

2007-01-01

44

Evaluation of the attenuation provided by a radar absorbing material (RAM) coating on an HF wire rope antenna  

Microsoft Academic Search

A shipboard electromagnetic interference (EMI) problem is considered. The use of radar absorbent material (RAM) to reduce unintentional X-band (8-12 GHz) radar reflections from HF wire rope antennas is analyzed. An exact series solution for a lossy-coated circular cylinder was developed and used to determine the effectiveness of the various RAM coatings

Griffin K. Gothard; Broun Hall

1991-01-01

45

A comparative study of Particle Swarm Optimization and Differential Evolution on Radar Absorbing Materials design for EMC applications  

Microsoft Academic Search

Radar absorbing materials (RAM) design for a desired frequency and angle range is presented. We evaluate the performance of particle swarm optimization (PSO) and differential evolution (DE) regarding their applicability to absorber design. The results show that the DE algorithm outer performs PSO variants.

S. K. Goudos; Z. D. Zaharis; K. B. Baltzis; C. S. Hilas; J. N. Sahalos

2009-01-01

46

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Dynamic Response and Fracture Mechanism of a Novel Structural Radar Absorbing Material  

NASA Astrophysics Data System (ADS)

A novel structural radar absorbing material (SRAM), which gives the normal resin-base composites new function, is prepared. The dynamic compressive tests of SRAM are carried out in both in-plane and normal directions of composites by means of the split Hopkinson pressure bar (SHPB). In the compressive test along in-plane direction, failure occurs at the interface between a fibre and the matrix. A fracture mode and mechanism was proposed to explain these results. The addition of absorbing particles results in the deterioration of the compressive properties. However, there is no obvious decrease on compressive strength of SRAM with the radar absorbing properties.

Cao, Mao-Sheng; Zhou, Wei; Qu, Gui-Min; Rong, Ji-Li

2008-08-01

47

Wideband thin resistive metamaterial radar absorbing screen  

Microsoft Academic Search

It has been demonstrated that two layer metamaterial Hilbert curve array constructed from low conductivity material can act as a thin wideband radar absorbing screen. The advantage of using Hilbert curve over traditional circuit analogue radar absorbing screen is the smaller unit cell size, resulting in reduced coupling to higher order Floquent modes and reduced diffraction effects, which in turn

A. Noor; Zhirun Hu; H. H. Ouslimani; A. Priou

2009-01-01

48

Modelling of magnetic radar absorbing composites  

Microsoft Academic Search

This paper addresses the modelling of radar absorbing composite layers with ferromagnetic inclusions. The radar absorbing properties of these layers are strongly determined by the effective permeability of the composite material. The applicability of mixing formulas is discussed to determine the effective permeability. Furthermore, the RF-frequency behaviour of ferromagnetic inclusions is described. The mixing formulas and the RF-frequency behaviour of

Harmen Schippers; Tomas Lundin; Jaap Heijstek

2010-01-01

49

Development, characterization and optimization of dielectric radar absorbent materials as flexible sheets for use at X-band  

Microsoft Academic Search

This paper presents a study of the dielectric properties of radar absorbent materials (RAMs) for use at X- band. Two different RAMs with different conductivities were prepared from the conducting polymer polyaniline. The RAMs were characterized with respect to their absorption and reflectivity to electromagnetic waves, and electric permittivity. The evaluated materials attenuated the energy of the incident radiation from

Luiza de C. Folgueras; Mauro A. Alves; Mirabel C. Rezende

2007-01-01

50

Interaction of Electromagnetic Waves with Two-Dimensional Metal Covered with Radar Absorbing Material and Plasma  

NASA Astrophysics Data System (ADS)

A two-dimensional metal model is established to investigate the stealth mechanisms of radar absorbing material (RAM) and plasma when they cover the model together. Using the finite-difference time-domain (FDTD) method, the interaction of electromagnetic (EM) waves with the model can be studied. In this paper, three covering cases are considered: a. RAM or plasma covering the metal solely; b. RAM and plasma covering the metal, while plasma is placed outside; c. RAM and plasma covering the metal, while RAM is placed outside. The calculated results show that the covering order has a great influence on the absorption of EM waves. Compared to case a, case b has an advantage in the absorption of relatively high-frequency EM waves (HFWs), whereas case c has an advantage in the absorption of relatively low-frequency EM waves (LFWs). Through the optimization of the parameters of both plasma and RAM, it is hopeful to obtain a broad absorption band by RAM and plasma covering. Near-field attenuation rate and far-field radar cross section (RCS) are employed to compare the different cases.

Lan, Chaohui; Hu, Xiwei; Jiang, Zhonghe

2008-12-01

51

RCS evaluation of complex objects coated with radar absorbing materials using the complex ray method  

Microsoft Academic Search

The strategy and results of an RCS (radar cross section) evaluation of a dihedral corner reflector coated with lossy materials using the complex ray method are described. A computer program based on the analysis presented has been developed to perform effective RCS calculations of dihedral corner reflectors having the inner surfaces coated with or without radar adsorbing materials. One of

Y. Z. Ruan; H. P. Du

1992-01-01

52

Calculation of surface waves on a metallic sphere and cylinder with a multilayer radar-absorbing material  

Microsoft Academic Search

Based on an exact solution to the diffraction problem, expressions are obtained for calculating the components of the amplitude of the scattered EM field of a metallic sphere and cylinder with a multilayer radar-absorbing material. Calculation results are presented on the contribution of surface waves to the effective scattering area of such a metallic sphere and cylinder, as well as

S. M. Nesterov; I. A. Skorodumov

1992-01-01

53

Dependence of microwave absorption properties on ferrite volume fraction in MnZn ferrite\\/rubber radar absorbing materials  

Microsoft Academic Search

We report the analysis of measurements of the complex magnetic permeability (mur) and dielectric permittivity (?r) spectra of a rubber radar absorbing material (RAM) with various MnZn ferrite volume fractions. The transmission\\/reflection measurements were carried out in a vector network analyzer. Optimum conditions for the maximum microwave absorption were determined by substituting the complex permeability and permittivity in the impedance

Adriana M. Gama; Mirabel C. Rezende; Christine C. Dantas

2011-01-01

54

A simple method for optimizing radar absorbent material coatings on HF rope antennas for the increased attenuation of unwanted reflections  

Microsoft Academic Search

The research presented here examines the maximum attenuation available from concentric layers of radar absorbing materials (RAM) surrounding an infinitely long perfect electrically conducting circular cylinder. The electrical phenomenology of normally incident transverse magnetic (TM) and transverse electrical (TE) waves associated with backscattered and bistatic behavior is investigated for a frequency range up to 25 GHz. Some of the more

George W. Jarriel; Lloyd S. Riggs; Michael E. Baginski

1997-01-01

55

Dependence of microwave absorption properties on ferrite volume fraction in MnZn ferrite\\/rubber radar absorbing materials  

Microsoft Academic Search

We report the analysis of measurements of the complex magnetic permeability (?r) and dielectric permittivity (?r) spectra of a rubber radar absorbing material (RAM) with various MnZn ferrite volume fractions. The transmission\\/reflection measurements were carried out in a vector network analyzer. Optimum conditions for the maximum microwave absorption were determined by substituting the complex permeability and permittivity in the impedance

Adriana M. Gama; Mirabel C. Rezende; Christine C. Dantas

2011-01-01

56

Progress in smart radar absorbers  

NASA Astrophysics Data System (ADS)

Conventional (i.e. passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms but such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional 'smart' functionality such as monitoring damage, adaptive control of RCS or target appearance, Identification-Friend-or-Foe (IFF) and Absorb-While-Scan (AWS) This paper outlines the concept and basic properties of a novel type of active radar absorber, the so-called Phase-Switched Screen (PSS). The basic PSS topology is then modified so as to enable it to operate as a smart radar absorber when used together with an external sensor and feedback control loop. The theoretical predictions are confirmed using data measured on transmission-line analogues of the smart PSS structure.

Chambers, Barry; Tennant, Alan

2003-07-01

57

Progress in smart radar absorbers  

Microsoft Academic Search

Conventional (i.e. passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms but such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional 'smart' functionality such as monitoring damage, adaptive control of RCS or target appearance,

Barry Chambers; Alan Tennant

2003-01-01

58

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Dynamic Response and Fracture Mechanism of a Novel Structural Radar Absorbing Material  

Microsoft Academic Search

A novel structural radar absorbing material (SRAM), which gives the normal resin-base composites new function, is prepared. The dynamic compressive tests of SRAM are carried out in both in-plane and normal directions of composites by means of the split Hopkinson pressure bar (SHPB). In the compressive test along in-plane direction, failure occurs at the interface between a fibre and the

Mao-Sheng Cao; Wei Zhou; Gui-Min Qu; Ji-Li Rong

2008-01-01

59

Design and fabrication of narrow band radar absorbing materials at terahertz frequencies R.H. Giles, A.J. Gatesman, A.P. Ferdinand and J. Waldman  

E-print Network

Design and fabrication of narrow band radar absorbing materials at terahertz frequencies R.H. Giles-infrared radiation absorbing material (FIRAM) which may be used to suppress unwanted stray radiation. One type material has been developed at the University of Lowell Research Foundation (ULRF). Low reflection coatings

Massachusetts at Lowell, University of

60

Analysis of impacts of various RAM on RCS of 3-D complex targets using the FEM-FMA [radar absorbing materials  

Microsoft Academic Search

The hybrid vector finite element method and fast multipole algorithm (FEM-FMA) are used to calculate the RCS of 3D complex targets coated with various radar absorbing materials (RAM). For a cone as an example, This work analyzes the impact of four canonical RAM coatings, including lossy isotropic, positive uniaxial anisotropic, negative uniaxial anisotropic and nanometer absorbing materials on the electromagnetic

Wang Pai; Zhou Lezhu; Tan Yanhua; Xia Mingyao

2004-01-01

61

Characterization of radar-absorbing material using time-domain techniques  

Microsoft Academic Search

A new free-space characterization method is proposed to evaluate the performance of absorber material in terms of both its specular reflection and creeping wave performance. A conducting cylinder is chosen as the reference object to generate a creeping wave contribution in the backscattered field. The specular reflection and creeping wave are separated in time due to a path-length difference. This

P. Niemand; J. W. Odendaal

1998-01-01

62

Waveguide characterization of flexible absorbing material  

Microsoft Academic Search

Among the materials with adequate performance to be used as radar absorbing material (RAM), the conducting polymers have been under intensive study due to their excellent potential for application in electromagnetic interference and microwave absorption areas, replacing conventional absorbing materials. The aim of this work is to present electromagnetic characterization of the flexible radar absorbing material at microwave frequency range

L. C. Folgueras; R. Faez; M. C. Rezende

2003-01-01

63

Fabrication of Radar Absorbing Structure and Evaluation of Radar Cross Section: Case Study of Hybrid Shells  

Microsoft Academic Search

Fiber-reinforced composite materials have outstanding mechanical and electrical properties; their applications have been expanded to commercial products as well as military components. Using composite materials, researchers have studied the radar absorbing, or `stealth' technology. In this research, to develop the radar absorbing structure (RAS), hybrid composite materials are fabricated into three-dimensional `C' and `U' shape shells. A series of experiments

Woo-Kyun Jung; Sung-Hoon Ahn; Bierng-Chearl Ahn; Seoung-Bae Park; Myung-Shik Won

2007-01-01

64

Computational method for radar absorbing composite lattice grids  

Microsoft Academic Search

Composite lattice grids reinforced by glass fibers (GFRC) and carbon fibers (CFRC) filled with spongy materials can be designed as lightweight radar absorbing structures (RAS). In the present paper, a computational approach based on periodic moment method (PMM) has been developed to calculate reflection coefficients of radar absorbing composite lattice grids. Total reflection backing (TRB) is considered directly in our

Mingji Chen; Yongmao Pei; Daining Fang

2009-01-01

65

The Theory and Design of Provably Optimal Bandwidth Radar Absorbent Materials (RAM) using Dispersive Structures and\\/or Frequency Selective Surfaces (FSS)  

Microsoft Academic Search

Performance coefficients, design tools and analysis is provided for the synthesis of optimal radar absorbent materials (RAM). The importance of equivalent circuits is emphasised. The basic theory is quite general and valid for metamaterial and frequency selective surfaces (FSS) composites containing piece-wise isotropic layered materials.

A. J. Mackay

2007-01-01

66

Dependence of microwave absorption properties on ferrite volume fraction in MnZn ferrite/rubber radar absorbing materials  

NASA Astrophysics Data System (ADS)

We report the analysis of measurements of the complex magnetic permeability ( ?r) and dielectric permittivity ( ?r) spectra of a rubber radar absorbing material (RAM) with various MnZn ferrite volume fractions. The transmission/reflection measurements were carried out in a vector network analyzer. Optimum conditions for the maximum microwave absorption were determined by substituting the complex permeability and permittivity in the impedance matching equation. Both the MnZn ferrite content and the RAM thickness effects on the microwave absorption properties, in the frequency range of 2-18 GHz, were evaluated. The results show that the complex permeability and permittivity spectra of the RAM increase directly with the ferrite volume fraction. Reflection loss calculations by the impedance matching degree (reflection coefficient) show the dependence of this parameter on both thickness and composition of RAM.

Gama, Adriana M.; Rezende, Mirabel C.; Dantas, Christine C.

2011-11-01

67

Microcellular ceramic foams for radar absorbing structures  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project is to develop a lightweight, semi-structural, radar-absorbing ceramic foam that can be incorporated into aircraft exhaust systems to replace many of the currently used dense ceramic parts and thereby improve the radar cross section. Although the conventional processes for producing ceramic foams have not been able to provide materials that meet the design specifications for high strength at low density, we have developed and demonstrated a novel sol-gel emulsion process for preparing microcellular ceramic foams in which compositional and microstructural control is expected to provide the requisite high-temperature radar-absorption, strength-to-weight ratio, and thermal insulative properties.

Huling, J.; Phillips, D.

1996-09-01

68

FACTORS AFFECTING THE PERFORMANCE OF THE RADAR ABSORBANT TEXTILE MATERIALS OF DIFFERENT TYPES AND STRUCTUS  

Microsoft Academic Search

Abstract—In the military applications, electro-optics and electro- magnetics features of the cloths made of special textile structures and certain fibers play an important role in producing textile characterized with high ability of camouflage. This means,not allowing enemy to precisely determine the moving and mute targets using available radar or any other electro-optics sensors. The aim of this paper is to

A. A. Hebeish; M. A. Elgamel; R. A. Abdelhady; Abdelmonem Abdelaziz Abdelaziz

2008-01-01

69

A versatile software tool for microwave planar radar absorbing materials design using global optimization algorithms  

Microsoft Academic Search

A computer-aided design (CAD) tool for the design of planar multi-layer coatings with high absorption for a desired frequency and angle range is presented. The tool uses deterministic and evolutionary optimization design methods. Both single and multi-objective design algorithms can be used and a single absorber design or the Pareto front can be found accordingly. A novel design technique utilizing

Sotirios K. Goudos

2007-01-01

70

Design and fabrication of narrow band radar absorbing materials at terahertz frequencies  

Microsoft Academic Search

The technique of tailoring the complex refractive index of an artificial dielectric material has been developed at the University of Lowell Research Foundation (ULRF). Low reflection coatings, generally referred to as Dällenbach layers, have been designed for metal substrates using the artificial dielectric. The method of characterizing materials for the purpose of tailoring their dielectric properties at terahertz frequencies will

R. H. Giles; A. J. Gatesman; A. P. Ferdinand; J. Waldman

1990-01-01

71

Performance of radar absorbing materials by waveguide measurements for X- and Ku-band frequencies  

Microsoft Academic Search

In this work, samples consisting of an elastomeric matrix containing different kinds of active materials in particulate form were prepared for reflectivity measurements. The materials individually used in weight contents of 80% in polychloroprene matrix were: carbonyl-iron (CI) and doped ferrite powders. The microwave reflectivity levels were determined from the magnetic and dielectric properties of the elastomeric composites obtained from

Magali Silveira Pinho; Maria Luisa Gregori; Regina Célia Reis Nunes; Bluma Guenther Soares

2002-01-01

72

Employing PML Absorbers in the Design and Simulation of Ground Penetrating Radars  

E-print Network

to simulate an absorbing material inside the FDTD computational domain. T R S R R D S RADAR UNIT AIR GROUNDEmploying PML Absorbers in the Design and Simulation of Ground Penetrating Radars Levent Gurel: Total signals at the receiver when the radar unit is modeled as in Fig. 2b with no absorbers. The depth

Gürel, Levent

73

Complex permeability and permittivity and microwave absorption property of barium ferrite\\/EPDM rubber radar absorbing materials in 2-18GHz  

Microsoft Academic Search

In this paper, the effective complex permeability and permittivity spectra in rubber radar absorbing materials (RAM) with various barium ferrite volume fractions are measured in 2-18GHz using transmission\\/reflection method with HP8722ET vector network analyzer. The effects of the ferrite volume fraction and the thickness of the RAM on the microwave absorption properties in the frequency range of 2-18GHz are studied.

Feng Yongbao; Qiu Tai; Shen Chunying; Li Xiaoyun

2005-01-01

74

Terahertz backscattering behavior of various absorbing materials , A. J. Gatesmana  

E-print Network

, absorbers, scattering, radar 1. INTRODUCTION Absorbing materials are commonly utilized in a wide variety the backscattering behavior of several absorbing materials in a compact radar range at terahertz frequencies. Several different types of structures were characterized including wedged, pyramidal, and bulk absorbers. The 160

Massachusetts at Lowell, University of

75

Electromagnetic analysis of active radar absorbers  

Microsoft Academic Search

The details of an experimental active radar absorber have been presented. The absorber is based on the topology of a Salisbury screen but uses an active impedance layer to provide reflectivity tuning. The active impedance layer is a FSS controlled by semiconductor pin diodes. Measured reflectivity characteristics have been presented and compared to predictions obtained from a simple equivalent circuit

P. N. Kaleeba; A. Tennant; B. Chambers; J. P. Idez

2003-01-01

76

Terahertz backscattering behavior of various absorbing materials  

NASA Astrophysics Data System (ADS)

The Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has investigated the electromagnetic scattering behavior of various broadband absorbers. Several absorbing materials were tested in a compact radar range operating at a center frequency of 160 GHz. The polarimetric radar cross section was measured at elevation angles from 15° to 75°. In addition to the backscattering behavior, the normal incidence transmittance of the materials was evaluated.

Wu, C.; Gatesman, A. J.; DeRoeck, L.; Horgan, T.; Giles, R. H.; Nixon, W. E.

2009-05-01

77

Microcellular ceramic foams for radar absorbing structures  

Microsoft Academic Search

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project is to develop a lightweight, semi-structural, radar-absorbing ceramic foam that can be incorporated into aircraft exhaust systems to replace many of the currently used dense ceramic parts and thereby improve the radar cross section.

J. Huling; D. Phillips

1996-01-01

78

Recent developments in radar absorbing paints and the Zinc oxide tetrapod whisker  

Microsoft Academic Search

Recent advancements in the field of material science have created several novel materials whose electromagnetic (EM) properties make them ideal candidates for use as radar absorbing materials (RAM). The new types of RAM materials can be applied as very thin layers of paints and still maintain their absorption effectiveness making them ideal for radar cross section (RCS) reduction on aircraft,

Byron T. Caudle; George T. Flowers; Michael E. Baginski; Stuart M. Wentworth; Sadasiva M. Rao

2009-01-01

79

Thin Radar Absorber Using an Artificial Magnetic Ground Plane  

Microsoft Academic Search

This paper provides experimental and numerical simulation verification of the radar absorbing properties of an ultra-thin radar absorber. The absorber takes the form of an artificial magnetic conductor with surface mounted resistors. Electromagnetic simulations show the confinement of current distributed across the surface which results as a consequence of plane wave excitation. For the first time it was shown experimentally

S. W. Simms; V. F. Fusco

2006-01-01

80

Optimization of Radar Absorber Structures Using Genetic Algorithms  

Microsoft Academic Search

In this paper, a real-valued genetic algorithm (GA) is implemented to construct Radar Absorbing Materials RAM by searching\\u000a the characteristics (thickness T, permittivity?, permeability? and conductivity ?) which ensure the minimization of the reflectivity\\u000a on a frequency band. The genetic algorithms used the reflectivity in fitness function to direct the research to the best configuration.\\u000a Here in, we dealt with

Nadia Lassouaoui; Habiba Hafdallah Ouslimani; Alain Priou

81

Design of a wideband radar absorbing structure  

Microsoft Academic Search

In this paper, a thin planar electromagnetic absorber consisting of two lossy Frequency Selective Surface (FSS) layers is introduced. The layers are separated by foam material and they are backed by the ground plane. Square rings and crossed dipoles are used in the design of these lossy layers. A wideband absorption characteristic is achieved for zero degrees of incidence angle

Egemen Yildirim; Ozlem Aydin Civi

2011-01-01

82

Study on the electromagnetic properties of a coated radar absorbent  

NASA Astrophysics Data System (ADS)

The sol-gel method is used to fabricate Fe crystalline powders coated with SiO2. By controlling the molar ratio R of diluted water to tetraethoxysilane (TEOS), Fe powders coated with SiO2 with different morphological characteristics are fabricated. The influence of the core diameter on electromagnetic parameters is investigated. The effect of the amount of the coating material SiO2 on electromagnetic parameters is given. Radar wave absorbing properties of Fe coated with SiO2 and TiO2 respectively are compared.

Zhang, Shuan-Qin

2012-06-01

83

A novel method of computation and optimization for multi-layered radar absorbing coatings using open source software  

Microsoft Academic Search

We created a simple software package based on open source software (GNU\\/Linux). This software package combined the electromagnetic parameters database and an optimization engine based on genetic algorithms, by which we can store and manage a large number of electromagnetic parameters towards radar absorbing materials, and can also design multi-layered radar absorbing coatings (RACs) using the materials stored in the

Yuan Jie; Xiao Gang; Cao Mao-Sheng

2006-01-01

84

Hybrid multilayer structures for use as microwave absorbing material  

Microsoft Academic Search

The aim of this study is the in situ processing of flexible multilayer radar absorbing structures materials based on polymeric substrates impregnated with polyaniline conducting polymer. There is a growing interest in the development of low density flexible absorber material for applications that require the reduction of the reflectivity of targets with complex shapes and improvement of the ease of

Luiza de C. Folgueras; Mirabel C. Rezende

2007-01-01

85

Design and implementation of a smart radar absorber  

Microsoft Academic Search

In this paper we have introduced a new topology for a digitally-controlled smart radar absorbing structure based on the phase-switched screen and presented initial experimental data which support the theoretical concept.

B. Chambers; A. Tennant

2003-01-01

86

Fabrication of Radar Absorbing Shells Made of Hybrid Composites and Evaluation of Radar Cross Section  

Microsoft Academic Search

** , Seoung-Bae Park ** and Myung-Shik Won *** ABSTRACT The avoidance of enemy's radar detection is very important issue in the modern electronic weapon system. Researchers have been studied to minimize reflected signals of radar. In this research, two types of radar absorbing structure (RAS), \\

Woo-Kyun Jung; Sung-Hoon Ahn; Bierng-Chearl Ahn

2005-01-01

87

Multi-objective optimization design of radar absorbing sandwich structure  

Microsoft Academic Search

By introducing a dimensionless parameter to couple the two objectives, weight and radar absorbing performance, into a single\\u000a objective function, a multi-objective optimization procedure for the radar absorbing sandwich structure (RASS) with a cellular\\u000a core is proposed. The optimization models considered are one-side clamped sandwich panels with four kinds of cores subject\\u000a to uniformly distributed loads. The average specular reflectivity

Ming-ji Chen; Yong-mao Pei; Dai-ning Fang

2010-01-01

88

RCS Reduction of Array Antennas with Radar Absorbing Structures  

Microsoft Academic Search

This paper introduces a radar absorbing structures (RAS) applied to reduce the in-band radar cross section (RCS) of the array antennas. The structure of the RAS is based on square patch structure loaded with lumped resistances. An array with four patch elements was designed and built, and the RAS was located between two adjacent patch elements. The simulated and measured

F.-W. Wang; S.-X. Gong; S. Zhang; X. Mu; T. Hong

2011-01-01

89

Return loss enhancement of surface resistors loaded microwave radar absorber  

Microsoft Academic Search

In this paper, return loss enhancement of a compact ultra-thin microwave radar absorber is demonstrated, The absorber is designed using textured surface technology comprised of a high impedance surface (HIS) positioned directly behind the anisotropically resistive-elements interconnecting a textured surface of square patches. By the selection of appropriate choice of the required surface resistors based on elementary circuit principles the

Achmad Munir; Vincent Fusco; Chairunnisa

2009-01-01

90

Adaptive radar absorbing structures with active FSS  

Microsoft Academic Search

A brief description of the theory of passive and active absorbers is presented followed by details of an experimental study into a new design of adaptive absorber. The absorber is a single-layer planar structure based upon the topology of a Salisbury screen, but in which the conventional resistive layer is replaced by an active frequency selective surface (FSS) controlled by

Alan Tennant; Barry Chambers

2002-01-01

91

FDTD modelling of active radar absorbers  

Microsoft Academic Search

An active absorber, such as the phase-switched screen (PSS), achieves an apparent reduction in the level of the electromagnetic energy reflected from its surface by using binary phase modulation to redistribute it over a bandwidth which is much wider than that of the receiver [Chambers B. and Tennant A., 2004]. Previous analyses of the PSS have been based on either

B. Chambers; A. Tennant

2007-01-01

92

Thin composite radar absorber operational for all incidence angles  

Microsoft Academic Search

It is shown that thin mushroom layers (high-impedance surfaces realized as regular arrays of small patches at a small distance from a metal surface) can be used as radar absorbing structures whose performance does not change with the incidence angle for TM polarized waves. The key role of the vias connectors between the patches and the ground plane is explained,

Sergei Tretyakov; Stanislav Maslovski

2003-01-01

93

Development of the composite RAS (radar absorbing structure) for the X-band frequency range  

Microsoft Academic Search

Since the EM properties of fiber reinforced polymeric composites can be tailored effectively by adjusting its composition, they are plausible materials for fabricating the radar absorbing structure (RAS) of desired performance. In this study, the composite RAS which has superior load bearing capacity and EM absorption characteristics has been developed by blending the conductive carbon black with the binder matrix

Woo Seok Chin; Dai Gil Lee

2007-01-01

94

Application of the hybrid algorithm combining ant colony optimization algorithm with microgenetic algorithm to the optimization of multilayered radar absorbing coating  

Microsoft Academic Search

A new optimization technique based on the hybrid algorithm combining ant colony optimization algorithm with microgenetic algorithm is presented for the design of multilayered radar absorbing materials. During the optimization procedure the optimization constrained conditions are different in order to meet the practical requirements in the different frequency bands between 2 GHz and 18 GHz, and the multilayered radar absorbing

Kun Chao; Yunlin Liu; Rugui Yang

2008-01-01

95

Fabrication of radar absorbing structure (RAS) using GFR-nano composite and spring-back compensation of hybrid composite RAS shells  

Microsoft Academic Search

The fiber-reinforced composite materials have been advanced to provide excellent mechanical and electromagnetic properties. The radar absorbing structure (RAS) is such an example that satisfies both radar absorbing property and structural characteristics. The absorbing efficiency of RAS can be obtained from selected materials having special absorptive properties and structural characteristics such as multi-layer and stacking sequence.In this research, to develop

Woo-Kyun Jung; Beomkeun Kim; Myung-Shik Won; Sung-Hoon Ahn

2006-01-01

96

Compatibility study of an absorber material and two silicone adhesives  

Microsoft Academic Search

A radar absorbing material, CMS-184, and assemblies bonded with two silicone based structural adhesives, DC-577 and RTV-630, were subjected to limited accelerated aging conditions and then evaluated for degradation of mechanical properties and adhesion, respectively. Aging conditions likely to be equivalent to 150 to 750 years at 72\\/degree\\/F and 100% RH only slightly changed the tensile strength and failure strain

R. J. Martinez; T. R. Guess; K. T. Gillen

1988-01-01

97

Controlling Nanoparticle Aggregation in Colloidal Microwave Absorbers via Interface Chemistry  

E-print Network

Microwave absorbing materials for military applications have been investigated since the advent of radar systems. The majority of these systems, including Salisbury screens, Jaumann absorbers, radar absorbing absorber that utilizes ferromagnetic particles in combination with a dielectric matrix material offers

Stowell, Michael

98

Graphene based tunable fractal Hilbert curve array broadband radar absorbing screen for radar cross section reduction  

NASA Astrophysics Data System (ADS)

This paper proposes a new type of graphene based tunable radar absorbing screen. The absorbing screen consists of Hilbert curve metal strip array and chemical vapour deposition (CVD) graphene sheet. The graphene based screen is not only tunable when the chemical potential of the graphene changes, but also has broadband effective absorption. The absorption bandwidth is from 8.9GHz to 18.1GHz, ie., relative bandwidth of more than 68%, at chemical potential of 0eV, which is significantly wider than that if the graphene sheet had not been employed. As the chemical potential varies from 0 to 0.4eV, the central frequency of the screen can be tuned from 13.5GHz to 19.0GHz. In the proposed structure, Hilbert curve metal strip array was designed to provide multiple narrow band resonances, whereas the graphene sheet directly underneath the metal strip array provides tunability and averagely required surface resistance so to significantly extend the screen operation bandwidth by providing broadband impedance matching and absorption. In addition, the thickness of the screen has been optimized to achieve nearly the minimum thickness limitation for a nonmagnetic absorber. The working principle of this absorbing screen is studied in details, and performance under various incident angles is presented. This work extends applications of graphene into tunable microwave radar cross section (RCS) reduction applications.

Huang, Xianjun; Hu, Zhirun; Liu, Peiguo

2014-11-01

99

Radar surveillance through solid materials  

NASA Astrophysics Data System (ADS)

The Department of Defense (DoD) has funded a dazzling array of 'high tech' solutions for many of the problems facing our military forces. Many of these 'solutions' have been effective for long range mass destruction but have not been applicable for the close-in hand-to-hand combat that we find in the streets. Our goal has been to convert 'high tech' DoD capabilities into cost effective tools to help law enforcement agencies do their jobs better. Surveillance systems presently used by law enforcement officers make extensive use of television, infrared and other line-of- sight surveillance hardware. However, these systems cannot tell what is happening on the other side of a wall, behind bushes, around the corner, in the dark or through a dense fog. A new sensor has been developed, based upon technology developed by the DoD for missile warhead fusing. This small, light weight, low power 'radar' is based upon the phenomena that optimized radio waves can penetrate non-metallic materials. This new surveillance capability can help provide information about what is in a wall, ceiling or floor or on the other side of a door or concrete wall. This paper discusses some applications to show how this radar works and some of the phenomenology which is unique to material penetrating radar systems.

Frazier, Lawrence M.

1997-02-01

100

Damage tolerant light absorbing material  

DOEpatents

A light absorbing article comprised of a composite of carbon-bonded carbon fibers, prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000.degree. C. to form a carbon-bonded carbon fiber light absorbing composite article having a bulk density less than 1 g/cm.sup.3.

Lauf, Robert J. (Oak Ridge, TN); Hamby, Jr., Clyde (Harriman, TN); Akerman, M. Alfred (Knoxville, TN); Seals, Roland D. (Oak Ridge, TN)

1993-01-01

101

Damage tolerant light absorbing material  

DOEpatents

A light absorbing article comprised of a composite of carbon-bonded carbon fibers, is prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000 C to form a carbon-bonded carbon fiber light absorbing composite article having a bulk density less than 1 g/cm[sup 3]. 9 figures.

Lauf, R.J.; Hamby, C. Jr.; Akerman, M.A.; Seals, R.D.

1993-09-07

102

Magnetic field effects on microwave absorbing materials  

NASA Technical Reports Server (NTRS)

The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

1991-01-01

103

A smart radar absorber based on the phase-switched screen  

Microsoft Academic Search

Although conventional (i.e., passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms, such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional smart functionality such as monitoring damage, adaptive control of RCS or target appearance,

Barry Chambers; Alan Tennant

2005-01-01

104

Method based on physical optics for the computation of the radar cross section including diffraction and double effects of metallic and absorbing bodies modeled with parametric surfaces  

Microsoft Academic Search

A method to compute the monostatic radar cross section (RCS) of complex bodies modeled by nonuniform rational B-spline (NURBS) surfaces is presented. The bodies can be covered by any kind of radar absorbing material (RAM) with electric and\\/or magnetic losses. Physical optics (PO) is used to obtain the scattered field of each surface. Fresnel coefficients are included in the stationary

Francisco Saez de Adana; Iván González Diego; Oscar Gutiérrez Blanco; Pablo Lozano; Manuel F. Cátedra

2004-01-01

105

Compatibility study of an absorber material and two silicone adhesives  

SciTech Connect

A radar absorbing material, CMS-184, and assemblies bonded with two silicone based structural adhesives, DC-577 and RTV-630, were subjected to limited accelerated aging conditions and then evaluated for degradation of mechanical properties and adhesion, respectively. Aging conditions likely to be equivalent to 150 to 750 years at 72/degree/F and 100% RH only slightly changed the tensile strength and failure strain of CMS-184 (initial modulus remained unchanged). The RTV-630 adhesive performed better than DC-577 adhesive in butt tensile tests of unaged and aged specimens. Based on the results of these accelerated aging studies, both the CMS-184 absorber material and the RTV-630 adhesive should survive the expected life of current weapon systems. 3 tabs.

Martinez, R.J.; Guess, T.R.; Gillen, K.T.

1988-01-01

106

Design of a Lightweight Magnetic Radar Absorber Embedded With Resistive FSS  

Microsoft Academic Search

In this letter, the design of a lightweight magnetic radar absorber (RA) having broadband bandwidth in frequency range of 1–18 GHz is demonstrated. A 5-mm-thick magnetic RA with weak wave-absorbing performance is obtained on the basis of polyurethane foam filled with flake ferrous microwave absorbent. The use of frequency selective surfaces (FSSs) results in a significant increase of the absorbing

Liangkui Sun; Haifeng Cheng; Yongjiang Zhou; Jun Wang

2012-01-01

107

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers.

Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.

2005-01-01

108

Solar absorber material reflectivity measurements at temperature  

SciTech Connect

Assessment of absorber shell material properties at high operating temperatures is essential to the full understanding of the solar energy absorption process in a solar thermal rocket. A review of these properties, their application and a new experimental methodology to measure them at high temperatures is presented. The direct application for the research is absorber cavity development for a Solar Thermal Upper Stage (STUS). High temperature measurements, greater than 1,000 Kelvin, are difficult to obtain for incident radiation upon a solid surface that forms an absorber cavity in a solar thermal engine. The basic material properties determine the amount of solar energy that is absorbed, transmitted or reflected and are dependent upon the material's temperature. This investigation developed a new approach to evaluate the material properties (i.e., reflectivity, absorptive) of the absorber wall and experimentally determined them for rhenium and niobium sample coupons. The secular reflectivity was measured both at room temperature and at temperatures near 1,000 Kelvin over a range of angles from 0 to 90 degrees. The same experimental measurements were used to calculate the total reflectivity of the sample by integrating the recorded intensities over a hemisphere. The test methodology used the incident solar energy as the heating source while directly measuring the reflected light (an integrated value over all visible wavelengths). Temperature dependence on total reflectivity was found to follow an inverse power function of the material's temperature.

Bonometti, J.A.; Hawk, C.W.

1999-07-01

109

Absorber Materials at Room and Cryogenic Temperatures  

SciTech Connect

We recently reported on investigations of RF absorber materials at cryogenic temperatures conducted at Jefferson Laboratory (JLab). The work was initiated to find a replacement material for the 2 Kelvin low power waveguide Higher Order Mode (HOM) absorbers employed within the original cavity cryomodules of the Continuous Electron Beam Accelerator Facility (CEBAF). This effort eventually led to suitable candidates as reported in this paper. Furthermore, though constrained by small funds for labor and resources, we have analyzed a variety of lossy ceramic materials, several of which could be usable as HOM absorbers for both normal conducting and superconducting RF structures, e.g. as loads in cavity waveguides and beam tubes either at room or cryogenic temperatures and, depending on cooling measures, low to high operational power levels.

F. Marhauser, T.S. Elliott, A.T. Wu, E.P. Chojnacki, E. Savrun

2011-09-01

110

Tech Transfer Webinar: Energy Absorbing Materials  

ScienceCinema

A new material has been designed and manufactured at LLNL that can absorb mechanical energy--a cushion--while also providing protection against sheering. This ordered cellular material is 3D printed using direct ink writing techniques under development at LLNL. It is expected to find utility in application spaces that currently use unordered foams, such as sporting and consumer goods as well as defense and aerospace.

Duoss, Eric

2014-07-15

111

Investigations on Absorber Materials at Cryogenic Temperatures  

SciTech Connect

In the framework of the 12 GeV upgrade project for the Continuous Electron Beam Accelerator Facility (CEBAF) improvements are being made to refurbish cryomodules housing Thomas Jefferson National Accelerator Facility?s (JLab) original 5-cell cavities. Recently we have started to look into a possible simplification of the existing Higher Order Mode (HOM) absorber design combined with the aim to find alternative material candidates. The absorbers are implemented in two HOM-waveguides immersed in the helium bath and operate at 2 K temperature. We have built a cryogenic setup to perform measurements on sample load materials to investigate their lossy characteristics and variations from room temperature down to 2 K. Initial results are presented in this paper.

Frank Marhauser, Thomas Elliott, Robert Rimmer

2009-05-01

112

Modeling of microwave absorbing structure using winning particle optimization applied on electrically conductive nanostructured composite material  

Microsoft Academic Search

This work presents the design and optimization of a Radar Absorbing Material system in the X-band frequency using evolutionary algorithm. Winning Particle Optimization is a new evolutionary algorithm. Due to its elementary evolving mechanism, it recall in mind primordial life form in trying to search the best place to proliferate. It is shown that such method, is quite simple but

Davide Micheli; Carmelo Apollo; Roberto Pastore; Mario Marchetti

2010-01-01

113

Analysis and design of multilayer Jaumann absorbers  

Microsoft Academic Search

In this paper, a transmission line model is constructed to analyze the performance of radar absorbing materials and the reflection characteristic of the resonance frequency. First, the paper introduces some kind of radar absorbing materials. Then, multilayer Jaumann absorbers are also analyzed using Smith Chart. Last, some multilayer Jaumann absorbers can be designed in the paper , which have good

Li Ke; Zhang Xin; Hou Xinyu; Zhang Peng

2011-01-01

114

Energy absorbing hybrid nano-composite materials  

NASA Astrophysics Data System (ADS)

Base Epon 862 resin was enhanced with two types of fillers, graphitized carbon nanofiber (CNF) and silicon dioxide (SiO2) particles. The effect of both filler type and filler loading were investigated with respect to the energy absorbing capacity as well as the thermal stability of the hybrid composite material, measured in terms of the coefficient of thermal expansion (CTE). As well the composites with combinations of the fillers were evaluated for both enhanced damping and thermal stability, making it suitable for structural materials that need multiple functions. The composites were evaluated with dynamic mechanical analysis (DMA) to evaluate viscoelastic response, and using strain gauges to measure thermal strain responses. It has been found that the addition of 3wt% SiO2 along with 3wt% CNF can improve damping loss factors by up to 26% while at the same time improving thermal stability with reductions in CTE of up to 16.5%. Furthermore, these fillers loadings were successfully dispersed as received by mechanical mixing technique, making fabrication more economically suited to engineering applications.

Jang, Jae-Soon; Varischetti, Joshua; Lee, Gyo Woo; Suhr, Jonghwan

2009-03-01

115

Semicylindrical Radar Absorbing Structures using Fiber-reinforced Composites and Conducting Polymers in the X-band  

Microsoft Academic Search

This paper presents a low observable structure with curved surfaces made by fiber-reinforced composites, conducting polymers and shows the possibility of developing stealth platforms for military applications. We propose radar absorbing structures (RAS) based on a circuit analog absorber in order to reduce the radar cross-section (RCS) of an object with curved surfaces. First, semi-cylindrical RAS with a periodic square

Hong-Kyu Jang; Jae-Hwan Shin; Chun-Gon Kim; Sang-Hun Shin; Jin-Bong Kim

2011-01-01

116

Design of radar absorbing structures using glass\\/epoxy composite containing carbon black in X-band frequency ranges  

Microsoft Academic Search

It is an important issue not only for military purposes but also from commercial point of view, whether or not the reflective wave from an incident electromagnetic wave can be nullified. In this research, by blending conductive carbon black with the binder matrix of glass\\/epoxy composite, a radar absorbing structure (RAS) which can support loads and absorb the electromagnetic wave

Jung-Hoon Oh; Kyung-Sub Oh; Chun-Gon Kim; Chang-Sun Hong

2004-01-01

117

Coagulation monitor based on serum migration through absorbent materials  

Microsoft Academic Search

I describe a method to measure blood coagulation prop- erties, based on the hypothesis that the distance the serum component of a clotted plasma sample moves through a suitable absorbent material should be propor- tional to the blood's ability to clot. A simple apparatus was constructed to test this principle, in which an absorbent strip contacts clotted plasma samples. At

Paul E. Wilson

118

Submillimeter Wavelength Modeling of Dielectric Materials in Polarimetric Radar Approaches  

E-print Network

the feasibility of modeling clutter at microwave and millimeter wavelengths. Introduction The concept of usingSubmillimeter Wavelength Modeling of Dielectric Materials in Polarimetric Radar Approaches R made polarimetric study of dielectric materials at submillimeter wavelengths possible. The first

Massachusetts at Lowell, University of

119

Controlling radar signature  

SciTech Connect

Low observable technologies for military and tactical aircraft are reviewed including signature-reduction techniques and signal detection/jamming. Among the applications considered are low-signature sensors and the reduction of radar cross section in conjunction with radar-absorbing structures and materials. Technologies for reducing radar cross section are shown to present significant technological challenges, although they afford enhanced aircraft survivability.

Foulke, K.W. (U.S. Navy, Naval Air Warfare Center, China Lake, CA (United States))

1992-08-01

120

Controlling radar signature  

Microsoft Academic Search

Low observable technologies for military and tactical aircraft are reviewed including signature-reduction techniques and signal detection\\/jamming. Among the applications considered are low-signature sensors and the reduction of radar cross section in conjunction with radar-absorbing structures and materials. Technologies for reducing radar cross section are shown to present significant technological challenges, although they afford enhanced aircraft survivability.

Foulke

1992-01-01

121

Determination of Interrogating Frequencies to Maximize Electromagnetic Backscatter from Objects with Material  

E-print Network

of radar absorbent material is modeled using a finite element method. Based on the radar cross section in the sector of interest. Key words: radar cross section, radar absorbent material, optimization, finite to maximize electromag- netic backscatter from objects with radar absorbent material (RAM) coatings

122

Schlieren photography to study sound interaction with highly absorbing materials.  

PubMed

Strong absorption of sound is often caused by the conversion of sound energy into heat. When this happens, it is not possible to study the interaction of sound with the absorbing material by means of reflected sound characteristics, because there is no reflected sound. Detecting for example the distance that sound travels in a strongly absorbing material, can be done by heat detection systems. However, the presence of temperature detectors in such materials interferes with the sound field and is therefore not really suitable. Infrared measurements are a possible option. Another option is the use of Schlieren photography for simultaneous visualization of sound and heat. This technique is briefly outlined with a 3 MHz sound beam incident on a highly absorbing sponge. PMID:15950023

Declercq, Nico F; Degrieck, Joris; Leroy, Oswald

2005-06-01

123

Ni-Zn nanoferrite for radar-absorbing material  

NASA Astrophysics Data System (ADS)

Nanoparticles of nickel-zinc ferrite have been prepared by using the citrate precursor method. According to scanning electron microscopy (SEM), the particle size is nanometric for the powder calcined at 350 °C/3.5 h. The phase formation has been studied by applying different calcining atmospheres, such as air and argon. Pure Ni-Zn ferrite has been observed when calcined in argon at the temperature of 350 °C. Hysteresis analyses have been done with magnetization of 53.01 emu/g at 350 °C and obtaining 84.62 emu/g at 1100 °C due to an optimization of domains formation at high temperature. Measures of reflectivity of Ni-Zn ferrite/epoxy composite have been obtained below 21% at 350 °C and above 96% at 1100 °C with a coercive field of 26.61 Oe. Low value of coercive field increased the mobilization of domains wall and increased the radiation absorption.

Lima, U. R.; Nasar, M. C.; Nasar, R. S.; Rezende, M. C.; Araújo, J. H.

124

Optimized Design of Radar Absorbing Materials for Complex Targets  

Microsoft Academic Search

Abstract—In this paper, we present a hybrid technique for designing RAM optimally to reduce the RCS of complex targets in a wide-band frequency range. The technique combines a high-frequency method and a genetic algorithm (GA) to obtain an optimal RAM in complex targets. By the virtue of the high-frequency method, such as the physical optics (PO) method and the method,of

H.-S. Park; I.-S. Choi; J.-K. Bang; S.-H. Suk; S.-S. Lee; H.-T. Kim

2004-01-01

125

Ni–Zn nanoferrite for radar-absorbing material  

Microsoft Academic Search

Nanoparticles of nickel–zinc ferrite have been prepared by using the citrate precursor method. According to scanning electron microscopy (SEM), the particle size is nanometric for the powder calcined at 350°C\\/3.5h. The phase formation has been studied by applying different calcining atmospheres, such as air and argon. Pure Ni–Zn ferrite has been observed when calcined in argon at the temperature of

U. R. Lima; M. C. Nasar; R. S. Nasar; M. C. Rezende; J. H. Araújo

2008-01-01

126

Ni Zn nanoferrite for radar-absorbing material  

Microsoft Academic Search

Nanoparticles of nickel zinc ferrite have been prepared by using the citrate precursor method. According to scanning electron microscopy (SEM), the particle size is nanometric for the powder calcined at 350 °C\\/3.5 h. The phase formation has been studied by applying different calcining atmospheres, such as air and argon. Pure Ni Zn ferrite has been observed when calcined in argon

U. R. Lima; M. C. Nasar; R. S. Nasar; M. C. Rezende; J. H. Araújo

2008-01-01

127

Computation of radar absorbing silicon carbide foams and their silica matrix composites  

Microsoft Academic Search

SiC-foams and their composites were studied as novel stealthy materials by numerical simulations. The reflection coefficients of various SiC-foams are found to be strongly dependent on the SiC volume fractions, electric conductivities and frequency. A foaming SiC allows to reach high level of electromagnetic wave absorbing ability when the SiC volume fraction and the conductivity at proper values comparing to

Hongtao Zhang; Jinsong Zhang; Hongyan Zhang

2007-01-01

128

Integrating non-planar metamaterials with magnetic absorbing materials to yield ultra-broadband microwave hybrid absorbers  

NASA Astrophysics Data System (ADS)

Broadening the bandwidth of electromagnetic wave absorbers has greatly challenged material scientists. Here, we propose a two-layer hybrid absorber consisting of a non-planar metamaterial (MM) and a magnetic microwave absorbing material (MAM). The non-planar MM using magnetic MAMs instead of dielectric substrates shows good low frequency absorption and low reflection across a broad spectrum. Benefiting from this and the high frequency strong absorption of the MAM layer, the lightweight hybrid absorber exhibits 90% absorptivity over the whole 2-18 GHz range. Our result reveals a promising and flexible method to greatly extend or control the absorption bandwidth of absorbers.

Li, Wei; Wu, Tianlong; Wang, Wei; Guan, Jianguo; Zhai, Pengcheng

2014-01-01

129

Sound-absorbing slabs and structures based on granular materials (bound and unbound). [energy absorbing efficiency of porous material  

NASA Technical Reports Server (NTRS)

Sound absorbing slabs and structures made up of bound or unbound granular materials are considered and how to manufacture these elements at the building site. The raw material is a single grain powder (sand, expanded blast furnace slag, etc.) that imparts to the end products an apparent porosity of 25-45% and an energy dissipation within the structure leading to absorption coefficients that can be compared with those of mineral wool and urethane.

Petre-Lazar, S.; Popeea, G.

1974-01-01

130

Determination of optical properties of absorbing materials: a generalized scheme.  

PubMed

A generalized reflectance method for determination of optical properties of absorbing materials is developed and compared with other reflectance methods. In the present scheme the specimen is coated with dielectric transparent layer(s) and the reflectance ratios are measured. This novel scheme of specimen preparation and the method of measurement allow the specimen to be free from surface layers and at the same time account for possible effects of surface roughness. It can be applied to a wide variety of materials regardless of their surface conditions and is particularly useful for metals. PMID:18195831

Nagendra, C L; Thutupalli, G K

1983-02-15

131

Terahertz Behavior of Optical Components and Common Materials Andrew J. Gatesman a  

E-print Network

. Keywords: THz, materials, dielectric, absorbers, attenuation 1. INTRODUCTION Since 1981, Expert Radar, radar absorbing materials development, and obscured object detection. ERADS has developed fullyTerahertz Behavior of Optical Components and Common Materials Andrew J. Gatesman a , Andriy

Massachusetts at Lowell, University of

132

Fabrication and optimization of radar absorbing structures composed of glass\\/carbon fibers\\/epoxy laminate composites filled with carbon nanotubes  

Microsoft Academic Search

The radar absorbing structures (RAS), which cannot only load bearing but absorb electromagnetic wave energy by inducing dielectric loss and minimize reflected waves, is a multifunctional composite. Therefore, many researchers have paid attention on the development of RAS. The essence of the RAS was reducing RCS of the object. The composites possess excellent specific stiffness and strength. The electromagnetic wave

Zhengquan Zhang; Tiehu Li; Deqi Jing; Qiang Zhuang

2008-01-01

133

Materials identification synthetic aperture radar: progress toward a realized capability  

NASA Astrophysics Data System (ADS)

Most non-metallic materials have frequency-dependent reflectivity functions, that is, they reflect electromagnetic energy in a manner that depends on frequency. Pulsed-chirped synthetic aperture radar and other multispectral radar systems do not generally take into account the frequency dependence of material reflections in forming scenes or making other inferences. In this report, we introduce a simple mathematical approach to using existing pulsed chirp synthetic aperture systems in a manner which results in a determination of a frequency-dependent reflectivity function for each pixel in a computed scene. Our analysis of collected data suggests that the method may be useful to distinguish disturbed from non-disturbed earth, and to detect chemicals on the surface of the earth. The method we have developed provides the analyst with a vector above each pixel with each vector component referencing a frequency band. This additional information may be useful for considering surface texture, subsurface layering and materials identification.

Albanese, Richard A.; Medina, Richard L.

2013-05-01

134

Adaptive radar absorbing structure with PIN diode controlled active frequency selective surface  

Microsoft Academic Search

A brief description of the theory of passive and active absorbers is presented followed by details of an experimental study of a new design of adaptive absorber. The absorber is a single-layer planar structure based upon the topology of a Salisbury screen, but in which the conventional resistive layer is replaced by an active frequency selective surface (FSS) controlled by

A. Tennant; B. Chambers

2004-01-01

135

Absorvedores de Radiação Eletromagnética Aplicados no Setor Aeronáutico Electromagnetic Radiation Absorbers with Aeronautical Applications  

Microsoft Academic Search

Radar absorbing materials (RAM) are obtained from polymeric matrices added with specific additives or using hybrid structures in composite materials. Nowadays, these materials are widely used in various fields, including space, aircraft, electronics, medical and telecommunications. The purpose of the present work is to show a review of the basic concepts concerning radar absorbing materials, giving information about raw materials

JOSIANE DE CASTRO DIAS; FÁBIO SANTOS DA SILVA

136

Real-time measurement of absorbing material in contrail ice using a counterflow virtual impactor  

Microsoft Academic Search

Near-field in situ measurements of absorbing material contained in contrail ice has been measured using a particle soot\\/absorption photometer connected to a counterflow virtual impactor. Vertical profiles made through exhaust plumes from commercial aircraft show a difference in content of absorbing material between the upper and the lower half of the contrail. In the upper part, average concentrations of absorbing

Johan Ström; Sofia Ohlsson

1998-01-01

137

Alternative materials to cadmium for neutron absorbers in safeguards applications  

SciTech Connect

Cadmium is increasingly difficult to use in safeguards applications because of rising cost and increased safety regulations. This work examines the properties of two materials produced by Ceradyne, inc. that present alternatives to cadmium for neutron shielding. The first is an aluminum metal doped with boron and the second is a boron carbide powder, compressed into a ceramic. Both are enriched in the {sup 10}B isotope. Two sheets of boron doped aluminum (1.1 mm and 5.2mm thick) and one sheet of boron carbide (8.5mm thick) were provided by Ceradyne for testing. An experiment was designed to test the neutron absorption capabilities of these three sheets against two different thicknesses of cadmium (0.6mm and 1.6mm thick). The thinner piece of aluminum boron alloy (1.1mm) performed as well as the cadmium pieces at absorbing neutrons. The thicker aluminum-boron plate provided more shielding than the cadmium sheets and the boron carbide performed best by a relatively large margin. Monte Carlo N-Particle eXtended (MCNPX) transport code modeling of the experiment was performed to provide validaLed computational tools for predicting the behavior of systems in which these materials may be incorporated as alternatives to cadmium. MCNPX calculations predict that approximately 0.17mm of the boron carbide is equivalent to 0.6mm of cadmium. There are drawbacks to these materials that need to be noted when considering using them as replacements for cadmium. Notably, they may need to be thicker than cadmium, and are not malleable, requiring machining to fit any curved forms.

Freeman, Corey R [Los Alamos National Laboratory; Geist, William H [Los Alamos National Laboratory; West, James D [Los Alamos National Laboratory

2009-01-01

138

Design of single layer wave-absorbers based on lefthanded materials  

Microsoft Academic Search

A physical model of microwave-absorber with an air\\/left-handed material\\/metal structure is proposed, the absorbing characteristics of it is theoretically analyzed, the design fundamentals, ensuring that the absorber has a high absorbing performance in a certain frequency band, and the laws of the distributions of the electromagnetic parameters values satisfying the fundamentals are derived. The results of this work may be

Zhen Hui Zhang; Zheng Ping Wang; Shi Ming Qin; Zhen Ming Wang; Yue Kun Wang

2008-01-01

139

Application of linear programming techniques to the design of radar absorbers  

Microsoft Academic Search

The report presents two new methods for solving problems in reducing electromagnetic back-scatter from conducting surfaces. The first method is concerned with optimizing the design of microwave absorbing multilayers for uniform response over wideband and wide angle of incidence subject to the constraint that a certain layer or layers to be included are specified for structural, thermodynamic, or other reasons.

B. S. Thornton

1974-01-01

140

Inertia effects in impact energy absorbing materials and structures  

Microsoft Academic Search

Experimental data and numerical\\/computational models concerning the internal inversion of metal tubes and the dynamic crushing of aluminium honeycombs are presented and discussed as illustrations of impact energy absorbers whose behaviour is strongly influenced by inertial effects.

J. J. Harrigan; S. R. Reid; C. Peng

1999-01-01

141

Numerical predictions for radar absorbing silicon carbide foams using a finite integration technique with a perfect boundary approximation  

Microsoft Academic Search

Modeling and prediction of electromagnetic wave absorbing properties of SiC foams as novel stealth materials in the X-band range of 8.2-12.4 GHz are presented. Appropriate material parameters, including the conductivity, volume fraction, cell size, thickness, and surface modified foam structure, are determined through optimization calculations, where the impedance difference between the SiC foam and free space is minimized. The minimum

Hongtao Zhang; Jinsong Zhang; Hongyan Zhang

2006-01-01

142

On a Class of Planar Absorbers With Periodic Square Resistive Patches  

Microsoft Academic Search

A Pareto genetic algorithm is used to explore the performance of planar absorbers incorporating a sheet of periodic resistive patches embedded in a primary material substrate. The absorbing performance of a single-layer electric radar absorbing material (eRAM) with periodic resistive patches is compared to that of standard dual-layer absorbers made of wax laid on top of eRAM or magnetic radar

Hosung Choo; Hao Ling; Charles S. Liang

2008-01-01

143

Fabrication and design of multi-layered radar absorbing structures of MWNT-filled glass\\/epoxy plain-weave composites  

Microsoft Academic Search

The object of this study is to design radar absorbing structures (RAS) with load-bearing ability in the X-band. Glass\\/epoxy plain-weave composites of excellent specific stiffness and strength, containing multi-walled carbon nanotubes (MWNT) to induce dielectric loss, were fabricated. Observations of the microstructure and the permittivity of the composites confirmed that the fabrics are suitable for use as RASs. A genetic

Sang-Eui Lee; Ji-Ho Kang; Chun-Gon Kim

2006-01-01

144

Negative Refraction in a Uniaxial Absorbent Dielectric Material  

ERIC Educational Resources Information Center

Refraction of light from an isotropic dielectric medium to an anisotropic dielectric material is a complicated phenomenon that can have several different characteristics not usually discussed in electromagnetics textbooks for undergraduate students. With a simple problem wherein the refracting material is uniaxial with its optic axis normal to the…

Jen, Yi-Jun; Lakhtakia, Akhlesh; Yu, Ching-Wei; Lin, Chin-Te

2009-01-01

145

Investigation of the effectiveness of absorbent materials in oil spills clean up  

Microsoft Academic Search

The present study examines the absorption capacity of five different types of materials for oil spills clean up. The absorbents were a commercial cellulosic material from processed wood, a commercial synthetic organic fiber from polypropylene and three commercial types of local expanded perlite from the island of Milos. The absorption capacities of the above materials were evaluated in a wet

Ch. Teas; S. Kalligeros; F. Zanikos; S. Stournas; E. Lois; G. Anastopoulos

2001-01-01

146

Numerical predictions for radar absorbing silicon carbide foams using a finite integration technique with a perfect boundary approximation  

NASA Astrophysics Data System (ADS)

Modeling and prediction of electromagnetic wave absorbing properties of SiC foams as novel stealth materials in the X-band range of 8.2-12.4 GHz are presented. Appropriate material parameters, including the conductivity, volume fraction, cell size, thickness, and surface modified foam structure, are determined through optimization calculations, where the impedance difference between the SiC foam and free space is minimized. The minimum reflection coefficient, reaching -8 dB, is obtained when the SiC conductivity is about 2.27 S m-1, the volume fraction is 28%, and the thickness is 20 mm in the case of SiC foam. For surface modified foam, the reflection can be less than -10 dB throughout the entire band investigated.

Zhang, Hongtao; Zhang, Jinsong; Zhang, Hongyan

2006-06-01

147

Superhydrophobic silanized melamine sponges as high efficiency oil absorbent materials.  

PubMed

Superhydrophobic sponges and sponge-like materials have attracted great attention recently as potential sorbent materials for oil spill cleanup due to their excellent sorption capacity and high selectivity. A major challenge to their broad use is the fabrication of superhydrophobic sponges with superior recyclability, good mechanical strength, low cost, and manufacture scalability. In this study, we demonstrate a facile, cost-effective, and scalable method to fabricate robust, superhydrophobic sponges through the silanization of commercial melamine sponges via a solution-immersion process. The silanization was achieved through secondary amine groups on the surface of the sponge skeletons with alkylsilane compounds, forming self-assembled monolayers on the surface of sponge skeletons. This resulted in our ability to tune the surface properties of the sponges from being hydrophilic to superhydrophobic with a water contact angle of 151.0°. The superhydrophobic silanized melamine sponge exhibited excellent sorption capacity for a wide range of organic solvents and oils, from 82 to 163 times its own weight, depending on the polarity and density of the employed organic solvents and oils, and high selectivity and outstanding recyclability with an absorption capacity retention greater than 90% after 1000 cycles. These findings offer an effective approach for oil spill containment and environmental remediation. PMID:25039789

Pham, Viet Hung; Dickerson, James H

2014-08-27

148

THERMAL EXPANSION COEFFICIENTS OF SOME MATERIALS USED FOR HOM LOAD ABSORBERS  

E-print Network

ERL 07-1 THERMAL EXPANSION COEFFICIENTS OF SOME MATERIALS USED FOR HOM LOAD ABSORBERS Valery, and for brazing ­ TiCuSil foil (4.5 % Ti, 26.7 % Cu, 8.8 % Ag). COEFFICIENTS OF THERMAL EXPANSION Ideally of the mutual shift of bonded materials, measurements of the thermal expansion coefficient were performed at our

149

Review of Optimisation Techniques for Layered Radar Materials Including the Genetic Algorithm.  

National Technical Information Service (NTIS)

The absorption of microwaves by a material depends on the properties of the material and its structure. Broadband absorbers can be fabricated by stacking resistive sheets separated by low dielectric spacers with a thickness of a quarter wavelength. This t...

P. Saville

2004-01-01

150

Absorber Materials for Transition-Edge Sensor X-ray Microcalorimeters  

NASA Technical Reports Server (NTRS)

Arrays of superconducting transition-edge sensors (TES) can provide high spatial and energy resolution necessary for x-ray astronomy. High quantum efficiency and uniformity of response can be achieved with a suitable absorber material, in which absorber x-ray stopping power, heat capacity, and thermal conductivity are relevant parameters. Here we compare these parameters for bismuth and gold. We have fabricated electroplated gold, electroplated gold/electroplated bismuth, and evaporated gold/evaporated bismuth 8x8 absorber arrays and find that a correlation exists between the residual resistance ratio (RRR) and thin film microstructure. This finding indicates that we can tailor absorber material conductivity via microstructure alteration, so as to permit absorber thermalization on timescales suitable for high energy resolution x-ray microcalorimetry. We show that by incorporating absorbers possessing large grain size, including electroplated gold and electroplated gold/electroplated bismuth, into our current Mo/Au TES, devices with tunable heat capacity and energy resolution of 2.3 eV (gold) and 2.1 eV (gold/bismuth) FWHM at 6 keV have been fabricated.

Brown, Ari-David; Bandler, Simon; Brekosky, Regis; Chervenak, James; Figueroa-Feliciano, Enectali; Finkbeiner, Fred; Sadleir, Jack; Iyomoto, Naoko; Kelley, Richard; Kilbourne, Caroline; Porter, F. Scott; Smith, Stephen; Saab, Tarek; Sadleir, Jac,

2007-01-01

151

Computed phase equilibria for burnable neutron absorbing materials for advanced pressurized heavy water reactors  

NASA Astrophysics Data System (ADS)

Burnable neutron absorbing materials are expected to be an integral part of the new fuel design for the Advanced CANDU ®[CANDU is as a registered trademark of Atomic Energy of Canada Limited.] Reactor. The neutron absorbing material is composed of gadolinia and dysprosia dissolved in an inert cubic-fluorite yttria-stabilized zirconia matrix. A thermodynamic model based on Gibbs energy minimization has been created to provide estimated phase equilibria as a function of composition and temperature. This work includes some supporting experimental studies involving X-ray diffraction.

Corcoran, E. C.; Lewis, B. J.; Thompson, W. T.; Hood, J.; Akbari, F.; He, Z.; Reid, P.

2009-03-01

152

Application of Millimeter Wave in Verification of Scale Model Measurement for Radar Cross Section  

Microsoft Academic Search

According to the physical optic approximation, a physical scale factor is suggested for scale model measurement of radar cross section (RCS). By this factor, the models of radar targets can be tested at the same frequency as prototype. This is significant for the lack of experimental equipment required or the problem of frequency dependency of radar absorbing materials on the

Hongwei Liu; Yahia M. M. Antar

1999-01-01

153

Application of Millimeter Wave in Verification of Scale Model Measurement for Radar Cross Section  

Microsoft Academic Search

According to the physical optic approximation, a physical scale factor is suggested for scale model measurement of radar cross section (RCS). By this factor, the models of radar targets can be tested at the same frequency as prototype. This is significant for the lack of experimental equipment required or the problem of frequency dependency of radar absorbing materials on the

Hongwei Liu; Yahia M. M. Antar; Zhendong Shi; Zhengde Wu

1998-01-01

154

Characterization and preparation of p(U-MMA-An) interpenetrating polymer network damping and absorbing material.  

PubMed

P(U-MMA-ANI) interpenetrating polymer network (IPN) damping and absorbing material is successfully synthesized by PANI particles served as an absorbing agent with the microemulsion polymerization and P(U-MMA) foam IPN network structure for substrate materials with foaming way. P(U-MMA-ANI) IPN is characterized by the compression mechanical performance testing, TG-DSC, and DSC. The results verify that the P(U-MMA) IPN foam damping material has a good compressive strength and compaction cycle property, and the optimum content of PMMA was 40% (mass) with which the SEM graphs do not present the phase separation on the macro level between PMMA and PU, while the phase separation was observed on the micro level. The DTG curve indicates that because of the formation of P(U-MMA) IPN, the decomposition temperature of PMMA and the carbamate in PU increases, while that of the polyol segment in PU has almost no change. P(U-MMA-ANI) IPN foam damping and absorbing material is obtained by PANI particles served as absorbing agent in the form of filler, and PMMA in the form of micro area in substrate material. When the content of PANI was up to 2.0% (mass), the dissipation factor of composites increased, and with the increasing of frequency the dissipation factor increased in a straight line. PMID:24738404

Liu, Jun; Li, Qingshan; Zhuo, Yuguo; Hong, Wei; Lv, Wenfeng; Xing, Guangzhong

2014-06-01

155

Enhancing and tuning absorption properties of microwave absorbing materials using metamaterials  

Microsoft Academic Search

We proposed and demonstrated a scheme to enhance and tune absorption properties of conventional microwave absorbing materials (MAMs) by metamaterials (MMs). By covering a MAM, say, carbonyl iron powder coating, with MMs composed of split ring resonators (SRRs) and wires, we show both by experiments and by simulations that the maximum reflection loss (RL) is increased significantly and the frequency

Yanhong Zou; Leyong Jiang; Shuangchun Wen; Weixing Shu; Yongjun Qing; Zhixiang Tang; Hailu Luo; Dianyuan Fan

2008-01-01

156

A One-Layer Ultra-Thin Meta-Surface Absorber Hossein Mosallaei and Kamal Sarabandi  

E-print Network

space is successfully accomplished. 2. A Review of Ultra-Thin Absorbers: In many radar and tracking for reducing the RCS of a structure is to coat it with a lossy material that can absorb the energy absorbers is based on the use of Salisbury screens [1]. This structure consists of a resistive sheet located

Sarabandi, Kamal

157

Realizing thin electromagnetic absorbers for wide incidence angles from commercially available planar circuit materials  

SciTech Connect

In this study, recent work on engineering R-card surface resistivity with printed metallic patterns is extended to the design of thin electromagnetic absorbers. Thin electromagnetic absorbers for wide incidence angles and both polarizations have recently been computationally verified by Luukkonen et al.. These absorbers are analytically modeled high-impedance surfaces with capacitive arrays of square patches implemented with relatively high dielectric constant and high loss substrate. However, the advantages provided by the accurate analytical model are largely negated by the need to obtain high dielectric constant material with accurately engineered loss. Fig. I(c) illustrates full-wave computational results for an absorber without vias engineered as proposed by Luukkonen et al.. Unique values for the dielectric loss are required for different center frequencies. Parameters for the capacitive grid are D=5.0 mm and w=O.l mm for a center frequency of 3.36 GHz. The relative permittivity and thickness is 9.20(1-j0.234) and 1=3.048 mm. Consider a center frequency of5.81 GHz and again 1=3.048 mm, the required parameters for the capacitive grid are D=2.0 mm and w=0.2 mm where the required relative permittivity is now 9.20(1-j0.371) Admittedly, engineered dielectrics are themselves a historically interesting and fruitful research area which benefits today from advances in monolithic fabrication using direct-write of dielectrics with nanometer scale inclusions. However, our objective in the present study is to realize the advantages of the absorber proposed by Luukkonen et al. without resort to engineered lossy dielectrics. Specifically we are restricted to commercially available planer circuit materials without use of in-house direct-write technology or materials engineering capability. The materials considered here are TMM 10 laminate with (35 {mu}lm copper cladding with a complex permittivity 9.20-j0.0022) and Ohmegaply resistor conductor material (maximum 250 {Omega}/sq.). A thin electromagnetic absorber for incidence angles greater than 30deg. but less than 60deg. and both polarizations is computationally demonstrated. This absorber utilizes high-permittivity, low-loss microwave substrate in conjunction with an engineered lossy sheet impedance. The lossy sheet impedance is easily engineered with simple analytical approximations and can be manufactured from commercially available laminate materials on microwave substrate.

Glover, Brian B [Los Alamos National Laboratory; Whites, Kieth W [SDSMT; Radway, Matthew J [CU-BOULDER

2009-01-01

158

Influence of the CNT length on complex permittivity of composite laminates and on radar absorber design in X-band  

Microsoft Academic Search

Due to the high aspect ratio, CNT dispersed in polymer matrix composites makes large electric dipoles bringing about high dielectric constant, as well as dense percolation networks for electric conductivity. The length scale of the CNT has the definite influence on the internal structures of percolation networks, affecting the characteristics complex permittivity of the composites. In a Da?llenbach type radar

Jin Bong Kim; Jun Hyung Byun

2010-01-01

159

Design and fabrication of a microstrip patch antenna with a low radar cross section in the X-band  

Microsoft Academic Search

In this study, the authors developed a radar absorbing method to reduce the antenna radar cross section (RCS) without any loss of antenna performance. The new method was based upon an electromagnetic bandgap (EBG) absorber using conducting polymer (CP). First, a microstrip patch antenna was made by using a copper film and glass\\/epoxy composite materials, which are typically used for

Hong-Kyu Jang; Won-Jun Lee; Chun-Gon Kim

2011-01-01

160

Adaptive energy-absorbing materials using field-responsive fluid-impregnated cellular solids  

Microsoft Academic Search

Adaptive materials with rapidly controllable and switchable energy-absorption and stiffness properties have a number of potential applications. We have developed, characterized and modeled a class of adaptive energy-absorbing systems consisting of nonlinear poroelastic composites wherein a field-responsive fluid, such as a magnetorheological fluid or a shear-thickening fluid, has been used to modulate the mechanical properties of a cellular solid. The

Suraj S. Deshmukh; Gareth H. McKinley

2007-01-01

161

Investigation of MEMS bi-material sensors with metamaterial absorbers for THz imaging  

NASA Astrophysics Data System (ADS)

There has been a continued interest in the terahertz (THz) imaging due to penetration and non-ionizing properties. Realtime imaging in this spectral range has been demonstrated using infrared microbolometer technology with external illumination by quantum cascade lasers (QCL). However, to achieve high sensitivity, it is necessary to develop focal plane arrays using enhanced THz-absorbing materials. One attractive option to achieve real time THz imaging is MEMS bi-material sensor with embedded metamaterial absorbers, consisting of a periodic array of metallic squared elements separated from a homogeneous metallic ground plane by a dielectric layer. We have demonstrated that the metamaterial films can be designed using standard MEMS materials such as silicon oxide (SiOx), silicon oxinitrate (SiOxNy) and aluminum (Al), to achieve nearly 100 % resonant absorption matched to the illumination source, while providing structural support, desired thermomechanical properties and access to external optical readout. The metamaterial structure absorbs the incident THz radiation and transfers the heat to bi-material microcantilevers that are connected to the substrate, which acts as a heat sink, via thermal insulating legs. A temperature gradient builds up in the legs, allowing the overall structure to deform proportionally to the absorbed power. The amount of deformation can be probed by measuring the displacement of a laser beam reflected from the sensor's metallic ground plane. Several sensor configurations have been designed, fabricated and characterized to optimize responsivity, speed of operation and minimize structural residual stress. Measured figures of merit indicate that the THz MEMS sensors have a great potential for real-time imaging.

Alves, Fabio; Grbovic, Dragoslav; Karunasiri, Gamani

2014-06-01

162

Optical response of strongly absorbing inhomogeneous materials: Application to paper degradation  

NASA Astrophysics Data System (ADS)

In this paper, we present a new noninvasive and nondestructive approach to recover scattering and absorption coefficients from reflectance measurements of highly absorbing and optically inhomogeneous media. Our approach is based on the Yang and Miklavcic theoretical model of light propagation through turbid media, which is a generalization of the Kubelka-Munk theory, extended to accommodate optically thick samples. We show its applications to paper, a material primarily composed of a web of fibers of cellulose, whose optical properties are strongly governed by light scattering effects. Samples studied were ancient and industrial paper sheets, aged in different conditions and highly absorbing in the ultraviolet region. The recovered experimental absorptions of cellulose fibers have been compared to theoretical ab initio quantum-mechanical computational simulations carried out within time-dependent density functional theory. In this way, for each sample, we evaluate the absolute concentration of different kinds of oxidized groups formed upon aging and acting as chromophores causing paper discoloration. We found that the relative concentration of different chromophores in cellulose fibers depends on the aging temperature endured by samples. This clearly indicates that the oxidation of cellulose follows temperature-dependent reaction pathways. Our approach has a wide range of applications for cellulose-based materials, like paper, textiles, and other manufactured products of great industrial and cultural interest, and can potentially be extended to other strongly absorbing inhomogeneous materials.

Missori, M.; Pulci, O.; Teodonio, L.; Violante, C.; Kupchak, I.; Bagniuk, J.; ?ojewska, J.; Conte, A. Mosca

2014-02-01

163

Study on metal microparticle content of the material transferred with Absorbing Film Assisted Laser Induced Forward Transfer when using silver absorbing layer  

NASA Astrophysics Data System (ADS)

Absorbing Film Assisted Laser Induced Forward Transfer (AFA-LIFT) is a modified LIFT method where a high absorption coefficient thin film coating of a transparent substrate is used to transform the laser energy into kinetic in order to transfer the "target" material spread on it. This method can be used for the transfer of biomaterials and living cells, which could be damaged by direct irradiation of the laser beam. In previous experiments, ˜50-100 nm thick metal films have been used as absorbing layer. The transferred material can also contain metal microparticles originating from the absorbing thin film and acting as non-desired impurities in some cases. The aim of our work was to study how the properties (number, size and covered area) of metal particles transferred during the AFA-LIFT process depend on film thickness and the applied fluence. Silver thin films with different thickness (50-400 nm) were used as absorbing layers and real experimental conditions were modeled by a 100 ?m thick water layer. The particles transferred without the use of water layer were also studied. The threshold laser fluence for the complete removal of the absorber from the irradiated area was found to strongly increase with increasing film thickness. The deposited micrometer and submicrometer particles were observed with optical microscope and atomic force microscope. Their size ranged from 100 nm to 20 ?m and depended on the laser fluence. The increase in fluence resulted in an increasing number of particles of smaller average size.

Smausz, T.; Hopp, B.; Kecskeméti, G.; Bor, Z.

2006-04-01

164

Dependence of acoustic properties of sound absorbing fibrous materials on their structure  

NASA Astrophysics Data System (ADS)

The performance of sound absorbing structures is characterized by two acoustic parameters: the dimensionless wave impedance (referred to the wave impedance of air) and the propagation constant. Both parameters can be defined as complex quantities whose real and imaginary parts were evaluated for various materials. On the basis of experimental data, semiempirical relations were established describing these parameters as functions of the density and of the fiber thickness, in the case of fibrous materials, as well as their frequency characteristics. The results given in pertain to fiberglass, mineral cotton wool, and nylon fiber.

Voronina, N. N.

1984-07-01

165

DEVELOPMENT OF ABSORBENT POLYMER MATERIALS FOR REDUCING ADHESION AND SKIN FRICTION OF UNDERGROUND STRUCTURES  

NASA Astrophysics Data System (ADS)

Pulling out steel sheet pile often harmfully deforms neighboring ground because of adhesion and skin friction between the pile and the ground. Steel H piles used in soil cement retaining walls could hinder additional construction and therefore should be removed. However, they usually are not removed due to high adhesion. To solve these problems, we developed new paint and sheet absorbent polymer materials for reducing the adhesion and skin friction. The performance of the materials was discussed and the effectiveness was confirmed through a series of laboratory tests and field tests.

Okamoto, Koichi; Umezaki, Takeo; Hattori, Akira

166

Autonomous wireless radar sensor mote integrating a Doppler radar into a sensor mote and its application in surveillance and target material classification  

NASA Astrophysics Data System (ADS)

An autonomous wireless sensor network that consists of different types of sensor modalities is a topic of intense research due to its versatility and portability of applications. Typical autonomous sensor networks commonly include passive sensor nodes such as infrared, acoustic, seismic, and magnetic. However, fusion of another active sensor such as Doppler radar in the integrated sensor network may offer powerful capabilities for many different sensing and classification tasks. In this work, we demonstrate the design and implementation of an autonomous wireless sensor network integrating a Doppler sensor into wireless sensor node with commercial off the shelf components. Then we demonstrate two applications of the newly integrated radar mote in a wireless sensor network environment where other sensor motes are supporting the integrated radar mote for autonomous triggering and data collection. At first we use the integrated system to detect the range and velocity of a toy train effectively to demonstrate its capability as a surveillance tool. Then we classify different types of non-conducting target materials based on their reflected signal response to newly built radar mote. Different types of materials can usually affect the amount of energy reflected back to the source of an electromagnetic wave. For investigating this observation we simulate models for the reflectivity of different homogeneous non-conducting materials using a mathematical model and later classify the types of target materials using real experimental data collected through our autonomous radar-mote sensor network.

Iftekharuddin, Khan; Khan, Muhammad M. R.; McCracken, Ernest; Wang, Lan; Kozma, Robert

2011-09-01

167

Microwave techniques for measurement of radar absorbing materials-a review  

Microsoft Academic Search

Summary form only given. The transmission line approach, used in conjunction with a network analyzer to measure the complex values of ? and ? of homogeneous as well as heterogeneous, but isotropic and thick samples, was described. For biaxial samples, a method that uses a guided-wave structure with a preferential axis, such as coaxial line or a waveguide of rectangular

G. Maze-Merceur; J.-L. Bonnefoy; J. Garat; R. Mittra

1992-01-01

168

Preparation and study on radar-absorbing materials of cupric oxide-nanowire-covered carbon fibers  

NASA Astrophysics Data System (ADS)

This paper firstly reports that cupric oxide nanowires (CNWs) were synthesized by thermal oxidation of copper coated carbon fibers (Cu/CFs). The results of transmission electron microscope images indicate that the nanowires are about 50 nm in diameter and several microns in length. The optimum growth conditions of the nanowires are found when the film of Cu/CFs is annealed at 400 °C for 4 h in air. The results show that the reflectivity of cupric oxide-nanowire-covered carbon fibers (1-1.3 mm in thickness) is less than -4 dB over the range of 8.6-18 GHz. Furthermore, the possible growth mechanism of CNWs is discussed.

Jun, Zeng; Peng, Tao; Sen, Wang; Jincheng, Xu

2009-02-01

169

Save radar absorbing material by coating only around the edges of a target for reduced RCS  

Microsoft Academic Search

UTD (uniform theory of diffraction) analysis for scattering from a wedge with arbitrary two-face impedances was used to formulate the problem of EM scattering from a plate with rim loading for TE and TM polarizations. The corner effects are neglected, and the 2-D to 3-D field conversion is done by Siegel's formula. An attempt is made to estimate the width

Asoke K. Bhattacharyya

1989-01-01

170

Preparation and study on radar-absorbing materials of cupric oxide-nanowire-covered carbon fibers  

Microsoft Academic Search

This paper firstly reports that cupric oxide nanowires (CNWs) were synthesized by thermal oxidation of copper coated carbon fibers (Cu\\/CFs). The results of transmission electron microscope images indicate that the nanowires are about 50nm in diameter and several microns in length. The optimum growth conditions of the nanowires are found when the film of Cu\\/CFs is annealed at 400°C for

Zeng Jun; Tao Peng; Wang Sen; Xu Jincheng

2009-01-01

171

Development of microwave absorbing materials prepared from a polymer binder including Japanese lacquer and epoxy resin  

NASA Astrophysics Data System (ADS)

Microwave absorption composites were synthesized from a poly urushiol epoxy resin (PUE) mixed with one of microwave absorbing materials; Ni-Zn ferrite, Soot, Black lead, and carbon nano tube (CNT) to investigate their microwave absorption properties. PUE binders were specially made from Japanese lacquer and epoxy resin, where Japanese lacquer has been traditionally used for bond and paint because it has excellent beauty. Japanese lacquer solidifies with oxygen contained in air's moisture, which has difficulty in making composite, but we improved Japanese lacquer's solidification properties by use of epoxy resin. We made 10 mm thickness composite samples and cut them into toroidal shape to measure permittivity, permeability, and reflection loss in frequencies ranging from 50 Hz to 20 GHz. Electric magnetic absorber's composites synthesized from a PUE binders mixed either with Soot or CNT showed significantly higher wave absorption over -27 dB than the others at frequencies around 18 GHz, although Japanese lacquer itself doesn’t affect absorption. This means Japanese lacquer can be used as binder materials for microwave absorbers.

Iwamaru, T.; Katsumata, H.; Uekusa, S.; Ooyagi, H.; Ishimura, T.; Miyakoshi, T.

172

How much material do the radar-bright craters at the Mercurian poles contain?  

NASA Astrophysics Data System (ADS)

The depth-to-diameter (d/D) ratios were determined for 12 craters located near the Mercurian north pole that were identified by Harmon et al. (2001, Icarus 149) as having strong depolarized radar echos. We find that the mean d/D value of these radar-bright craters is {2}/{3} the mean d/D value of the general population of non-radar-bright craters in the surrounding north polar region. Previous studies, however, show no difference between d/D values of Mercurian polar and equatorial crater populations, suggesting that no terrain softening which could modify crater structure exists at the Mercurian poles (Barlow et al., 1999, 194, Icarus 141). Thus, the change in d/D is governed by a change in crater depth, probably due to deposition of material inside the crater. The volume of infilling material, including volatiles, in the radar-bright craters is significantly greater than predicted by proposed mechanisms for the emplacement of either water ice or sulfur.

Vilas, Faith; Cobian, Paul S.; Barlow, Nadine G.; Lederer, Susan M.

2005-12-01

173

Aging behavior of polymeric solar absorber materials: Aging on the component level  

SciTech Connect

Within this study, the aging behavior of a PPE + PS absorber material was investigated on the absorber component level. To indicate aging, characteristic mechanical values were determined by indentation tests of specimens taken from components and exposed to laboratory aging (140 C in air, 80 C in water) and service near outdoor aging conditions (stagnation in northern climate). In addition to the mechanical tests, the unaged and aged specimens were also characterized thermo-analytically via differential scanning calorimetry (DSC). The results indicate that reductions in both characteristic mechanical values of the indentation tests, i.e., load of the first transition and ultimate indentation, reflect at least some physical aging although chemical aging may also be of importance based on previous analytical investigations of laboratory aged polymer films. While laboratory aging in air at 140 C and service exposure at a test facility in Oslo (N) under stagnation conditions led to a significant reduction in the mechanical indentation resistance, no influence of laboratory aging in water at 80 C on the mechanical behavior of the absorber sheet was found. Depending on the ultimate failure criterion applied (reduction of characteristic mechanical values to 80% and 50%, respectively), the technical service life found for hot air laboratory and stagnation service conditions was found to be less than 51 and 159 h, respectively. As these durations are significantly below the estimated stagnation conditions accumulated in the desired operation lifetime for such a collector, the PPE + PS type investigated does not seem to be a proper material candidate for solar thermal absorbers. Finally, based on the results obtained, a relation between laboratory aging time in air at 140 C and cumulated irradiation energy during exposure on the test facility in Oslo was established. (author)

Kahlen, S. [Polymer Competence Center Leoben GmbH, Roseggerstrasse 12, A-8700 Leoben (Austria); Wallner, G.M.; Lang, R.W. [Institute for Polymeric Materials and Testing, University of Linz, Altenbergerstrasse 69, A-4040 Linz (Austria); Meir, M.; Rekstad, J. [Department of Physics, University of Oslo, P.O. Box 1048, Blindern, N-0316 Oslo (Norway)

2010-03-15

174

Absorbing properties and structural design of microwave absorbers based on carbonyl iron and barium ferrite  

Microsoft Academic Search

Carbonyl iron and barium ferrite powder (BaZn1.5Co0.5Fe16O27) were prepared in this work. The complex permittivity and permeability spectra for rubber radar absorbing materials employing carbonyl iron and barium ferrite powders were measured. A database describing the frequency dependence of the permittivities and permeabilities of the carbonyl iron and barium ferrite microwave absorbers with various powder percentage compositions in 2 18

Y. B. Feng; T. Qiu; C. Y. Shen

2007-01-01

175

Absorbing properties and structural design of microwave absorbers based on carbonyl iron and barium ferrite  

Microsoft Academic Search

Carbonyl iron and barium ferrite powder (BaZn1.5Co0.5Fe16O27) were prepared in this work. The complex permittivity and permeability spectra for rubber radar absorbing materials employing carbonyl iron and barium ferrite powders were measured. A database describing the frequency dependence of the permittivities and permeabilities of the carbonyl iron and barium ferrite microwave absorbers with various powder percentage compositions in 2–18GHz was

Y. B. Feng; T. Qiu; C. Y. Shen

2007-01-01

176

Aging behavior of polymeric solar absorber materials - Part 2: Commodity plastics  

SciTech Connect

In this series of two papers, various polymeric materials are investigated as to their potential applicability as absorber materials for solar thermal collectors. While Part 1 of this paper series deals with the aging behavior of engineering plastics, including two amorphous polymers (PPE + PS) and (PC) and two semi-crystalline polymers (two types of PA12), the present Part 2 treats the aging behavior of semi-crystalline so-called ''commodity'' plastics (two types of crosslinked polyethylene (PE-X) and two types of polypropylene (PP)). As in Part 1, the focus of the investigation is to study the aging behavior of these materials under maximum operating conditions (80 C in water up to 16,000 h) and stagnation conditions (140 C in air up to 500 h) typical for northern climate. The materials supplied or produced as polymer films were first characterized in the unaged state and then for different states of aging by differential scanning calorimetry (DSC), by size exclusion chromatography (SEC) and by mechanical tensile tests. DSC was applied primarily to obtain information on physical aging phenomena, whereas SEC analysis was used to characterize chemical degradation of the materials. In addition, physical and chemical aging were both analyzed via the small and large strain mechanical behavior. Comparing the two aging conditions in hot air and hot water, a rather stable mechanical performance profile was found for both PP types over the investigated aging time, which was interpreted in terms of competing physical and chemical aging mechanisms. Analogously such competing mechanisms were also inferred for one of the PE-X materials, while the other exhibited substantial degradation in terms of strain-to-break values for both aging conditions. In principle, both PP and PE-X are promising candidates for black absorber applications in northern climates if proper measures against overheating are taken and when adequately modified. (author)

Kahlen, S. [Polymer Competence Center Leoben GmbH, Roseggerstrasse 12, Leoben 8700 (Austria); Wallner, G.M.; Lang, R.W. [Institute for Polymeric Materials and Testing, University of Linz, Altenbergerstrasse 69, Linz 4040 (Austria)

2010-09-15

177

Hazardous material minimization for radar assembly. Final report  

SciTech Connect

The Clean Air Act Amendment, enacted in November 1990, empowered the Environmental Protection Agency (EPA) to completely eliminate the production and usage of chlorofluorocarbons (CFCs) by January 2000. A reduction schedule for methyl chloroform beginning in 1993 with complete elimination by January 2002 was also mandated. In order to meet the mandates, the processes, equipment, and materials used to solder and clean electronic assemblies were investigated. A vapor-containing cleaning system was developed. The system can be used with trichloroethylene or d-Limonene. The solvent can be collected for recycling if desired. Fluxless and no-clean soldering were investigated, and the variables for a laser soldering process were identified.

Biggs, P.M.

1997-03-01

178

Reflection and transmission for layered composite materials  

NASA Technical Reports Server (NTRS)

A layered planar structure consisting of different bianisotropic materials separated by jump-immittance sheets is considered. Reflection and transmission coefficients are determined via a chain-matrix algorithm. Applications are important for radomes and radar-absorbing materials.

Graglia, Roberto D.; Uslenghi, Piergiorgio L. E.

1991-01-01

179

Aging behavior of polymeric solar absorber materials - Part 1: Engineering plastics  

SciTech Connect

In this series of two papers, various polymeric materials are investigated as to their potential applicability as absorber materials for solar thermal collectors. The focus of the investigation is to study the aging behavior of these materials under maximum operating conditions (80 C in water up to 16,000 h) and stagnation conditions (140 C in air up to 500 h) typical for northern climate. The materials supplied or produced as polymer films were first characterized in the unaged state and then for different states of aging by differential scanning calorimetry (DSC), by size exclusion chromatography (SEC) and by mechanical tensile tests. Physical aging phenomena were studied by DSC, SEC analysis provided information on chemical degradation of the materials. In addition, physical and chemical aging were both analyzed via the small and large strain mechanical behavior. While the present Part 1 of this paper series deals with the aging behavior of engineering plastics, including two amorphous polymers (a polyphenylene ether polystyrene blend (PPE + PS) and polycarbonate (PC)) and two semi-crystalline polymers (two types of polyamide 12 (PA12)), the aging behavior of so-called ''commodity'' plastics (PE and PP) is the subject of Part 2. Comparing the two aging conditions, the amorphous materials (PPE + PS and PC) turned out to be more prone to physical and chemical aging at 140 C in air. In contrast, the semi-crystalline PA12 materials were more strongly affected by exposure to water at 80 C, although to different degrees, depending on the modification. (author)

Kahlen, S. [Polymer Competence Center Leoben GmbH, Roseggerstrasse 12, Leoben 8700 (Austria); Wallner, G.M.; Lang, R.W. [Institute for Polymeric Materials and Testing, University of Linz, Altenbergerstrasse 69, Linz 4040 (Austria)

2010-09-15

180

All-GaInNAs ultrafast lasers: Material development for emitters and absorbers  

NASA Astrophysics Data System (ADS)

Defect engineering is a key feature in material development for active and passive laser devices. Active devices such as surface emitting lasers require excellent material quality with low defect concentration and good strain management. In contrast, passive devices such as saturable absorbers benefit from nonradiative recombination via defect states. Different molecular beam epitaxy (MBE) growth conditions and annealing parameters were developed to optimize GaInNAs for both active and passive devices. We have demonstrated for the first time an all-GaInNAs modelocked vertical external-cavity surface-emitting laser (VECSEL) at 1.3 ?m. We combined a GaInNAs VECSEL with a GaInNAs semiconductor saturable absorber mirror (SESAM) in a laser cavity. The VECSEL was optically pumped by an 808 nm semiconductor diode laser. The intracavity GaInNAs SESAM self-starts stable modelocking and generates a pulse duration of 18.7 ps with a pulse repetition rate of 6.1 GHz at 57 mW of average output power at a center wavelength of 1308 nm. In this paper, we briefly review the modelocking result and then focus on the MBE growth and fabrication of both active and passive GaInNAs devices.

Rutz, A.; Liverini, V.; Müller, E.; Schön, S.; Keller, U.

2007-04-01

181

High flux neutron imaging for high-speed radiography, dynamic tomography and strongly absorbing materials  

NASA Astrophysics Data System (ADS)

We present NEUTROGRAPH, a new instrument for high-flux neutron radiography and tomography at the Institut Laue-Langevin in Grenoble, France. It has been operational since October 2002. With a high-intensity thermal neutron beam of about 3×10 9 n cm -2 s -1, NEUTROGRAPH is dedicated to real-time, snapshot and stroboscopic radiography with time resolution down to a few microseconds, as well as dynamic tomography on a sub-minute time scale. The high intensity also allows the visualization of thick and strongly absorbing materials. This allows investigation of larger samples with extremely low contrast, as in some fields of material science and archaeology. Various experiments have been carried out during the last 2 years. We present the large spectrum of applications and we describe the properties of a detector system dedicated to these types of experiments. Furthermore, we describe an algorithm to eliminate the effects of scintillator degradation in intense neutron fluxes.

Hillenbach, A.; Engelhardt, M.; Abele, H.; Gähler, R.

2005-04-01

182

An investigation of using a phase-change material to improve the heat transfer in a small electronic module for an airborne radar application  

SciTech Connect

Finding new and improved means of cooling small electronic packages are of great importance to today's electronic packaging engineer. Thermal absorption through the use of a material which changes phase is an attractive alternative. Taking advantage of the heat capacity of a material's latent heat of fusion is shown to absorb heat away from the electronics, thus decreasing the overall temperature rise of the system. The energy equation is formulated in terms of enthalpy and discretized using a finite-difference method. A FORTRAN program to solve the discretized equations is presented which can be used to analyze heat conduction in a rectangular region undergoing an isothermal phase change. An analysis of heat transfer through a miniature radar electronic module cooled by a phase-change reservoir is presented, illustrating the method's advantages over conventional heat sinks. 41 refs., 11 figs., 2 tabs.

Snyder, K.W.

1990-10-01

183

Neutron-Absorbing Coatings for Safe Storage of Fissile Materials with Enhanced Shielding & Criticality Safety  

SciTech Connect

Neutron-absorbing Fe-based amorphous-metal coatings have been developed that are more corrosion resistant than other criticality-control materials, including Al-B{sub 4}C composites, borated stainless steels, and Ni-Cr-Mo-Gd alloys. The presence of relatively high concentration of boron in these coatings not only enhances its neutron-absorption capability, but also enables these coatings to exist in the amorphous state. Exceptional corrosion resistance has been achieved with these Fe-based amorphous-metal alloys through additions of chromium, molybdenum, and tungsten. The addition of rare earth elements such as yttrium has lowered the critical cooling rate of these materials, thereby rendering them more easily processed. Containers used for the storage of nuclear materials, and protected from corrosion through the application of amorphous metal coatings, would have greatly enhanced service lives, and would therefore provide greater long-term safety. Amorphous alloy powders have been successfully produced in multi-ton quantities with gas atomization, and applied to several half-scale spent fuel storage containers and criticality control structures with the high-velocity oxy-fuel (HVOF) thermal spray process. Salt fog testing and neutron radiography of these prototypes indicates that such an approach is viable for the production of large-scale industrial-scale facilities and containers. The use of these durable neutron-absorbing materials to coat stainless steel containers and storage racks, as well as vaults, hot-cell facilities and glove boxes could substantially reduce the risk of criticality in the event of an accident. These materials are particularly attractive for shielding applications since they are fire proof. Additionally, layers of other cold and thermal sprayed materials that include carbon and/or carbides can be used in conjunction with the high-boron amorphous metal coatings for the purpose of moderation. For example, various carbides, including boron, tungsten, and chromium carbide, as well as graphite particles can be co-deposited with a metallic binder phase with either thermal spray or cold spray technology. These moderator layers would also be fire resistant. By coating the vessels and piping used for spent fuel reprocessing, including slab and pencil tanks, enhanced criticality safety and substantially better corrosion resistance can be achieved simultaneously. Since these alloys are Fe-based, any substitution of these for high-performance Ni-based alloys is expected to result in a cost savings. Ultimately, the cost of these materials should comparable to that of stainless steels.

Choi, J; Farmer, J; Lee, C; Fischer, L; Boussoufi, M; Liu, B; Egbert, H

2007-07-03

184

Measurements of the light-absorbing material inside cloud droplets and its effect on cloud albedo  

NASA Technical Reports Server (NTRS)

Most of the measurements of light-absorbing aerosol particles made previously have been in non-cloudy air and therefore provide no insight into aerosol effects on cloud properties. Here, researchers describe an experiment designed to measure light absorption exclusively due to substances inside cloud droplets, compare the results to related light absorption measurements, and evaluate possible effects on the albedo of clouds. The results of this study validate those of Twomey and Cocks and show that the measured levels of light-absorbing material are negligible for the radiative properties of realistic clouds. For the measured clouds, which appear to have been moderately polluted, the amount of elemental carbon (EC) present was insufficient to affect albedo. Much higher contaminant levels or much larger droplets than those measured would be necessary to significantly alter the radiative properties. The effect of the concentrations of EC actually measured on the albedo of snow, however, would be much more pronounced since, in contrast to clouds, snowpacks are usually optically semi-infinite and have large particle sizes.

Twohy, C. H.; Clarke, A. D.; Warren, Stephen G.; Radke, L. F.; Charleson, R. J.

1990-01-01

185

Thin film stress control of absorber stack materials for EUVL reticles  

Microsoft Academic Search

Extreme ultraviolet lithography (EUVL) is the leading candidate for next generation lithography with the potential for extendibility beyond the 50-nm node. The three-layer absorber stack for EUVL reticles consists of an absorber, repair buffer and etch-stop layers, while a two-layer absorber stack eliminates the etch-stop layer. A portion of the mask pattern distortion can be assigned to the absorber stack's

James R. Wasson; Diana Convey; Pawitter J. Mangat; D. Frank Bazzarre; Lubomir Parobek

2002-01-01

186

Optical limiting threshold in carbon suspensions and reverse saturable absorber materials  

NASA Astrophysics Data System (ADS)

I report on the measurement of threshold energy fluence for optical limiting of nanosecond and microsecond pulses in a high-performance carbon suspension known as Defense Research Establishment Valcartier carbon black suspension (CBS)-100. Thresholds as low as 24-mJ/cm2 (nanosecond regime) and 100-mJ/cm2 (microsecond regime) have been obtained. The measurement technique, based on the f/20 optical system and a small analysis aperture, has been tested by measurement of reverse saturable absorber materials and other carbon suspensions whose properties can be found in the technical literature. A factor of merit has emerged from these measurements that could be used to order by limiting performance the different types of carbon suspensions. In this ordering, CBS-100 appears as the best choice in the set of suspensions tested for short and long pulses.

Vincent, Denis

2001-12-01

187

Optical limiting threshold in carbon suspensions and reverse saturable absorber materials.  

PubMed

I report on the measurement of threshold energy fluence for optical limiting of nanosecond and microsecond pulses in a high-performance carbon suspension known as Defence Research Establishment Valcartier carbon black suspension (CBS)-100. Thresholds as low as 24-mJ/cm(2) (nanosecond regime) and 100-mJ/cm(2) (microsecond regime) have been obtained. The measurement technique, based on an f/20 optical system and a small analysis aperture, has been tested by measurement of reverse saturable absorber materials and other carbon suspensions whose properties can be found in the technical literature. A factor of merit has emerged from these measurements that could be used to order by limiting performance the different types of carbon suspension. In this ordering, CBS-100 appears as the best choice in the set of suspensions tested for short and long pulses. PMID:18364974

Vincent, D

2001-12-20

188

Rain-Mapping Radar  

NASA Technical Reports Server (NTRS)

Orbiting radar system measures rates of rainfall from 0.5 to 60 mm/h. Radar waves scattered and absorbed by rainfall to extents depending on wavelength, polarization, rate of rainfall, and distribution of sizes and shapes of raindrops. Backscattered radar signal as function of length of path through rain used to infer detailed information about rain. Accumulated radar return signals processed into global maps of monthly average rainfall for use in climatological studies.

Im, K. E.; Li, F. K.; Wilson, W. J.; Rosing, D.

1988-01-01

189

Comparison study on the effect of carbon nano materials for single-layer microwave absorbers in X-band  

Microsoft Academic Search

In this paper, we have studied on the microwave absorbers in X-band (8.2–12.4GHz) made of E-glass\\/epoxy composite laminates containing three different types of carbon nano materials such as carbon black (CB), carbon nano fiber (CNF) and multi-wall carbon nano tube (MWNT). We calculated the complex permittivity solutions for single-layer microwave absorbers and checked the effect of the solutions on the

Jin-Bong Kim; Sang-Kwan Lee; Chun-Gon Kim

2008-01-01

190

Perovskite oxides for visible-light-absorbing ferroelectric and photovoltaic materials  

NASA Astrophysics Data System (ADS)

Ferroelectrics have recently attracted attention as a candidate class of materials for use in photovoltaic devices, and for the coupling of light absorption with other functional properties. In these materials, the strong inversion symmetry breaking that is due to spontaneous electric polarization promotes the desirable separation of photo-excited carriers and allows voltages higher than the bandgap, which may enable efficiencies beyond the maximum possible in a conventional p-n junction solar cell. Ferroelectric oxides are also stable in a wide range of mechanical, chemical and thermal conditions and can be fabricated using low-cost methods such as sol-gel thin-film deposition and sputtering. Recent work has shown how a decrease in ferroelectric layer thickness and judicious engineering of domain structures and ferroelectric-electrode interfaces can greatly increase the current harvested from ferroelectric absorber materials, increasing the power conversion efficiency from about 10-4 to about 0.5 per cent. Further improvements in photovoltaic efficiency have been inhibited by the wide bandgaps (2.7-4electronvolts) of ferroelectric oxides, which allow the use of only 8-20 per cent of the solar spectrum. Here we describe a family of single-phase solid oxide solutions made from low-cost and non-toxic elements using conventional solid-state methods: [KNbO3]1-x[BaNi1/2Nb1/2O3-?]x (KBNNO). These oxides exhibit both ferroelectricity and a wide variation of direct bandgaps in the range 1.1-3.8electronvolts. In particular, the x = 0.1 composition is polar at room temperature, has a direct bandgap of 1.39electronvolts and has a photocurrent density approximately 50 times larger than that of the classic ferroelectric (Pb,La)(Zr,Ti)O3 material. The ability of KBNNO to absorb three to six times more solar energy than the current ferroelectric materials suggests a route to viable ferroelectric semiconductor-based cells for solar energy conversion and other applications.

Grinberg, Ilya; West, D. Vincent; Torres, Maria; Gou, Gaoyang; Stein, David M.; Wu, Liyan; Chen, Guannan; Gallo, Eric M.; Akbashev, Andrew R.; Davies, Peter K.; Spanier, Jonathan E.; Rappe, Andrew M.

2013-11-01

191

Surfaces with adaptive radar reflection coefficients  

NASA Astrophysics Data System (ADS)

Conventional (passive) radar-absorbing materials (RAM) have been in use now for over half a century, but it is only with recent advances in conducting polymer composite materials that large-area surfaces having controllable reflection coefficients at radar frequencies have become practicable. Techniques for utilizing these new materials in re-configurable electromagnetic, or `smart', surfaces are reviewed, with due emphasis given to the problem of system integration. The discussion is complemented by modelled and measured performance data on several smart surface configurations.

Chambers, Barry

1997-10-01

192

Modeling Dielectric-constant values of Geologic Materials: An Aid to Ground-Penetrating Radar Data Collection and Interpretation  

Microsoft Academic Search

Ground-penetrating radar (GPR) is a near-surface geophysical imaging technique used for non- intrusive subsurface geologic and engineering investigations. Dielectric constant is a critical parameter for GPR surveys because it controls propagation velocity of electromagnetic waves through material, reflection coefficients across interfaces of different materials, and vertical and horizontal imaging resolution. Dielectric constant in rocks and sediments is primarily a function

Alex Martinez; Alan P. Byrnes

2001-01-01

193

Orbital Radar Response of Near Surface Materials in Southern Egypt and Implications for Cenozoic History  

NASA Astrophysics Data System (ADS)

Although the existence of "trunk" and tributary drainage channels beneath the sand in the northeast Sahara has been known for two decades, data from the SIR-C mission continues to be useful in solving geologic problems and understanding the radar response from specific types of near surface materials. In the Kiseiba Oasis region of southwest Egypt, SIR-C data revealed a complex tributary pattern of varying brightness that indicated the presence of paleodrainage not noted in the field. The orbital imaging radar uniquely specified key areas for detailed field studies that were not apparent in visible wavelengths. Twenty-two trenches up to 3 m deep, hundreds of shallow pits, several auger holes, and ground penetrating radar reveal that this area has had a history of fluctuating climatic conditions responsible for excavation and enlargement of the local depression by fluvial erosion and preservation of relict surfaces by aeolian blanketing of sand sheet deposits. The resulting near-surface stratigraphy is a complex mixture of fluvial pebble lags in the subsurface and on the surface, where aeolian mixing and local transport have modified the original geometry. In L-band (23 cm wavelength) SIR-C data, a hierarchy of returned signal strength and geometric patterns enables us to predict the type of surface and near-surface materials, sequentially from shallow bedrock to subsurface and surficial lags to sand sheet-veneered weathered anhydrite. Integrating the pattern of sedimentary deposits with relict channels and interfluves enables a better understanding of the origin of the Kiseiba-Dungul depression and its Cenozoic history. What was once thought to be a continuous deposit of Eocene limestone from southern Egypt into northern Sudan is cast in doubt as even the most optimistic estimates of scarp retreat don't permit hundred's of kms of retreat to the present position. Instead, the E-W pattern of the depression, the relict hills, and fracture zones all suggest structural control and erosion patterns that started with N-S compression in the latest Cretaceous. A humid climate during the Tertiary aided fluvial dissection of the broken surface, with drainage leading to the north into the present Kharga depression. The drainage patterns of the Quaternary seen now in orbital radar result from remnants of large-scale structural patterns and Tertiary drainage, confused by alternating hyperarid and semiarid climatic cycles that inverted topography, protected former erosion surfaces, and reversed drainage.

Maxwell, T. A.; Grant, J. A.; Johnston, A. K.

2004-05-01

194

Study of electromagnetic wave-absorbing materials made by a melt-dragging process  

Microsoft Academic Search

The advances in information communication have increased the usage of microwaves in the 0.5-5 GHz range because of the demand for the transmission of large amounts of data. Accordingly, the problem of electromagnetic interference has become increasingly serious, and therefore much attention has been paid to microwave absorbers to solve the problem. Thin microwave absorbers are required with high values

H. S. Cho; A. S. Kim; S. M. Kim; J. Namgung; M. C. Kim; G. A. Lee

2004-01-01

195

Radar electronic warfare  

Microsoft Academic Search

An overview of radar and electronic warfare is given. Definitions, common terms, and principles of radar and electronic warfare, and simple analyses of interactions between radar systems and electronic countermeasures (ECM) are presented. Electronic counter-countermeasure and electronic support measures are discussed. Background material in mathematics, electromagnetics, and probability necessary for an understanding of radar and electronic warfare is given and

August Golden Jr.

1987-01-01

196

Incorporation of Integral Fuel Burnable Absorbers Boron and Gadolinium into Zirconium-Alloy Fuel Clad Material  

SciTech Connect

Long-lived fuels require the use of higher enrichments of 235U or other fissile materials. Such high levels of fissile material lead to excessive fuel activity at the beginning of life. To counteract this excessive activity, integral fuel burnable absorbers (IFBA) are added to some rods in the fuel assembly. The two commonly used IFBA elements are gadolinium, which is added as gadolinium-oxide to the UO2 powder, and boron, which is applied as a zirconium-diboride coating on the UO2 pellets using plasma spraying or chemical vapor deposition techniques. The incorporation of IFBA into the fuel has to be performed in a nuclear-regulated facility that is physically separated from the main plant. These operations tend to be very costly because of their small volume and can add from 20 to 30% to the manufacturing cost of the fuel. Other manufacturing issues that impact cost and performance are maintaining the correct levels of dosing, the reduction in fuel melting point due to gadolinium-oxide additions, and parasitic neutron absorption at fuel's end-of-life. The goal of the proposed research is to develop an alternative approach that involves incorporation of boron or gadolinium into the outer surface of the fuel cladding material rather than as an additive to the fuel pellets. This paradigm shift will allow for the introduction of the IFBA in a non-nuclear regulated environment and will obviate the necessity of additional handling and processing of the fuel pellets. This could represent significant cost savings and potentially lead to greater reproducibility and control of the burnable fuel in the early stages of the reactor operation. The surface alloying is being performed using the IBEST (Ion Beam Surface Treatment) process developed at Sandia National Laboratories. IBEST involves the delivery of energetic ion beam pulses onto the surface of a material, near-surface melting, and rapid solidification. The non-equilibrium nature of such processing allows for surface alloying well in excess of the thermodynamically dictated solubility limits, an effect that is particularly relevant to this research due to the negligible solubility of boron and gadolinium in zirconium. University of Wisconsin is performing the near surface materials characterization and analysis, aiding Sandia in process optimization, and promoting educational activities. Westinghouse is performing process manufacturability and scale-up analysis and is performing autoclave testing of the surface treated samples. The duration of this NERI project is 2 years, from 9/2002 to 9/2004.

Sridharan, K.; Renk, T.J.; Lahoda, E.J.; Corradini, M.L

2004-12-14

197

Study of earth abundant tco and absorber materials for photovoltaic applications  

NASA Astrophysics Data System (ADS)

In order to make photovoltaic power generation a sustainable venture, it is necessary to use cost-effective materials in the manufacture of solar cells. In this regard, AZO (Aluminum doped Zinc Oxide) and CZTS (Copper Zinc Tin Sulfide) have been studied for their application in thin film solar cells. While AZO is a transparent conducting oxide, CZTS is a photovoltaic absorber. Both AZO and CZTS consist of earth abundant elements and are non-toxic in nature. Highly transparent and conductive AZO thin films were grown using RF sputtering. The influence of deposition parameters such as working pressure, RF power, substrate temperature and flow rate on the film characteristics was investigated. The as-grown films had a high degree of preferred orientation along the (002) direction which enhanced at lower working pressures, higher RF powers and lower substrate temperatures. Williamson-Hall analysis on the films revealed that as the working pressure was increased, the nature of stress and strain gradually changed from being compressive to tensile. The fall in optical transmission of the films was a consequence of free carrier absorption resulting from enhanced carrier density due to incorporation of Al atoms or oxygen vacancies. The optical and electrical properties of the films were described well by the Burstein-Moss effect. CZTS absorber layers were grown using ultrasonic spray pyrolysis at a deposition temperature of 350 C and subsequently annealed in a sulfurization furnace. Measurements from XRD and Raman spectra confirmed the presence of pure single phase Cu2ZnSnS4. Texture analysis of as-deposited and annealed CZTS films indicated that the (112) plane which is characteristic of the kesterite phase was preferred. The grain size increased from 50 nm to 100 nm on conducting post-deposition annealing. CZTS films with stoichiometric composition yielded a band gap of 1.5 eV, which is optimal for solar energy conversion. The variation of tin in the film changed its resistivity by several orders of magnitude and subsequently the tin free ternary chalcogenide Cu2ZnS2 having very low resistivity was obtained. By carefully optimization of concentrations of tin, zinc and copper, a zinc-rich/tin-rich/copper-poor composition was found to be most suitable for solar cell applications. Etching of CZTS films using KCN solution reduced their resistivity, possibly due to the elimination of binary copper sulfide phases. CZTS solar cells were fabricated both in the substrate and superstrate configurations.

Prabhakar, Tejas

198

Study of the effectiveness of selective absorber coatings and phase change materials in passive solar space heating  

NASA Astrophysics Data System (ADS)

The performance of selective absorber coatings in passive solar heating systems is assessed. The relative performance of thermal storage wall buildings when equipped either with a selective absorber coating or movable night instalation is studied. The advantages a phase change thermal storage wall might have over a conventional system that employs either masonary or water as the thermal storage medium are determined. Phase change material walls were tested with and without a diatomaceous Earth thickening agent that suppresses convection and in both vented and unvented configurations. Results are presented and discussed.

Wray, W. O.; Hyde, I. C.; Bourdeau, L. E.

199

Study of the effectiveness of selective absorber coatings and phase change materials in passive solar space heating  

SciTech Connect

The project reported had two primary objectives. The first objective was to assess the performance of selective absorber coatings in passive solar heating systems. The relative performance of thermal storage wall buildings when equipped either with a selective absorber coating or movable night instulation was studied. The second objective was to determine what advantages, if any, a phase change thermal storage wall might have over a conventional system that employs either masonary or water as the thermal storage medium. Phase change material (PCM) walls were tested with and without a diatomaceous earth thickening agent that suppresses convection and in both vented and unvented configurations. Results are presented and discussed.

Wray, W.O.; Hyde, J.C.; Bourdeau, L.E.

1980-01-01

200

Metamaterial Electromagnetic Absorbers and Plasmonic Structures.  

E-print Network

??In this thesis metamaterial radar absorbers and plasmonic structures have been investigated. Following a brief overview covering metamaterial structures, and their applications in various areas… (more)

Noor, Adnan

2010-01-01

201

[Simultaneous determination of migration amounts of antioxidants and ultraviolet absorbents by high performance liquid chromatography in food contact materials].  

PubMed

An efficient analytical method for the quantitative determination of migration levels of antioxidants and ultraviolet absorbents in food contact materials by high performance liquid chromatography (HPLC) has been developed. The analytical method showed good linearity with the correlation coefficients (r2) > or = 0.999 8 for all the compounds. The limits of detection were between 0.01 mg/L and 0.22 mg/L and the limits of quantification were in the range of 0.03 to 0.85 mg/L for the 23 analytes. According to the European Union Directive No 10/2011, five food simulants were investigated: 30 g/L acetic acid, 10% (v/v) ethanol, 20% (v/v) ethanol, 50% (v/v) ethanol, and fatty food simulant (isooctane). The recoveries were in the range of 92.8%-117.7%, with the relative standard deviations of 0.95%-9.72%. The effects of different experimental conditions on the recoveries of antioxidants and UV absorbents were studied. The results showed that the method is accurate and stable, and can meet the requirements of European Commission Regulation (EU) No 10/2011 and GB 9685-2008 for the specific migration limits (SML) of the antioxidants and ultraviolet absorbents in real food contact plastic materials and article samples. The method has been applied to determine the migration levels of antioxidants and ultraviolet absorbents in different simulants from the migration tests of 30 batches of food contact material samples. PMID:25269260

Li, Chengfa; Li, Ying; Chen, Zhinan; Liang, Feng; Chen, Xuhui; Wu, Shaojing; Li, Yongtao; Sun, Xiaoying

2014-06-01

202

ANNUAL REPORT. MATERIAL PROPERTY ESTIMATION FOR DIRECT DETECTION OF DNAPL USING INTEGRATED GROUND-PENETRATING RADAR VELOCITY, IMAGING, AND ATTRIBUTE ANALYSIS  

EPA Science Inventory

The focus of our work is direct detection of DNAPLs, specifically chlorinated solvents, via material property estimation from surface ground-penetrating radar (GPR) data. We combine sophisticated GPR processing methodology with quantitative attribute analysis and material propert...

203

Nonlinear inversion of borehole-radar tomography data to reconstruct velocity and attenuation distribution in earth materials  

USGS Publications Warehouse

A nonlinear tomographic inversion method that uses first-arrival travel-time and amplitude-spectra information from cross-hole radar measurements was developed to simultaneously reconstruct electromagnetic velocity and attenuation distribution in earth materials. Inversion methods were developed to analyze single cross-hole tomography surveys and differential tomography surveys. Assuming the earth behaves as a linear system, the inversion methods do not require estimation of source radiation pattern, receiver coupling, or geometrical spreading. The data analysis and tomographic inversion algorithm were applied to synthetic test data and to cross-hole radar field data provided by the US Geological Survey (USGS). The cross-hole radar field data were acquired at the USGS fractured-rock field research site at Mirror Lake near Thornton, New Hampshire, before and after injection of a saline tracer, to monitor the transport of electrically conductive fluids in the image plane. Results from the synthetic data test demonstrate the algorithm computational efficiency and indicate that the method robustly can reconstruct electromagnetic (EM) wave velocity and attenuation distribution in earth materials. The field test results outline zones of velocity and attenuation anomalies consistent with the finding of previous investigators; however, the tomograms appear to be quite smooth. Further work is needed to effectively find the optimal smoothness criterion in applying the Tikhonov regularization in the nonlinear inversion algorithms for cross-hole radar tomography. ?? 2001 Elsevier Science B.V. All rights reserved.

Zhou, C.; Liu, L.; Lane, Jr. , J. W.

2001-01-01

204

Preparation and study on microwave absorbing materials of boron nitride coated pyrolytic carbon particles  

NASA Astrophysics Data System (ADS)

Boron nitride coatings were synthesized on pyrolytic carbon (BN-coated PyC) particles via chemical reaction of boric acid and urea in nitrogen. The results of Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FI-IR) and X-ray photoelectron spectroscopy (XPS) show the formation of boron nitride coating. The TGA curves indicate that the oxidation resistance of the PyC particles is improved by incorporating BN coating on the surface. The mass of the BN-coated PyC particles remains over 60% at 1200 °C whereas the PyC particles are oxidized completely at 920 °C. The investigation of microwave absorbing property reveals that compared with the PyC particles, the BN-coated PyC particles have lower permittivity (?', ??) and better absorbing property. The BN-coated PyC particles show a strong absorbing peak at 10.64 GHz, where the lowest reflectivity -21.72 dB is reached. And the reflectivity less than -10 dB is over the range of 9.6-12 GHz.

Zhou, Wei; Xiao, Peng; Li, Yang

2012-09-01

205

Study of electromagnetic wave-absorbing materials made by a melt-dragging process  

NASA Astrophysics Data System (ADS)

The advances in information communication have increased the usage of microwaves in the 0.5-5 GHz range because of the demand for the transmission of large amounts of data. Accordingly, the problem of electromagnetic interference has become increasingly serious, and therefore much attention has been paid to microwave absorbers to solve the problem. Thin microwave absorbers are required with high values of relative complex permeability (r = r + jr) and permittivity (r = r + jr). In this study various permalloy alloys with high permeability were designed, melted in a high-frequency induction furnace in air, melt-dragged into flakes, crushed into powders by a vibration mill, and deformed into ultrathin flakes by an attrition mill. The flake powders were then mixed with silicone rubber and formed into a sheet. When the flakes were mixed with the silicone rubber and formed into a 1 mm thick sheet the complex permeability and complex permittivity were substantially increased and the reflection loss at 0.8 GHz was -2.13 dB. It is possible to make thin and high-performance microwave-absorbing sheets with a flake powder of 79Ni-Fe alloy.

Cho, H. S.; Kim, A. S.; Kim, S. M.; Namgung, J.; Kim, M. C.; Lee, G. A.

2004-06-01

206

Microstructural Characterization of Burnable Absorber Materials Being Evaluated for Application in LEU U-Mo Fuel Plates  

SciTech Connect

The starting microstructure of a fuel plate will impact how it performs during irradiation. As a result, microstructural characterization has been performed on as-fabricated monolithic fuel plates to determine the changes in fuel plate microstructure that may result from changes in fabrication parameters. Particular focus has been given to the fuel plate U-10Mo/Zr and Zr/AA6061 cladding interfaces, since the integrity of these interfaces will play a big role in determining the overall performance of the fuel plate during irradiation. In addition, burnable absorber materials for potential incorporation into monolithic fuel plates have been characterized to identify their as-fabricated microstructures. This information will be important when trying to understand the PIE data from fuel plates with burnable absorbers that are irradiated in future irradiation experiments. This paper will focus on the microstructures observed using optical metallography, X-ray diffraction, and scanning and transmission electron microscopy for monolithic fuel plates exposed to different fabrication parameters and for as-fabricated burnable absorber materials.

J. F. Jue; B. Miller; B. Yao; E. Perez; Y. H. Sohn

2011-03-01

207

Geomorphological significance of Ontario Lacus on Titan: Integrated interpretation of Cassini VIMS, ISS and RADAR data and comparison with the Etosha Pan (Namibia)  

E-print Network

, likely composed of a thick and liquid-saturated coating of photon-absorbing materials in the infrared, ISS and RADAR data and comparison with the Etosha Pan (Namibia) T. Corneta,1 , O. Bourgeoisa , S. Le (ISS) in 2004 and 2005, Visual and Infrared Mapping Spectrometer (VIMS) in 2007 and 2009 and RADAR

Brest, Université de

208

Radar applications  

NASA Astrophysics Data System (ADS)

Papers are presented on air-traffic control radar, surveillance radar, missile guidance radar, and high-performance tactical three-dimensional radar. Also considered are the airborne early warning radar, the Foxhunter airborne intercept radar, and environmental remote sensing. Other topics include spaceborne SARs, the Pioneer Orbiter radar, and a bistatic pulse-Doppler intruder-detection radar.

Skolnik, Merrill I.

209

Radar applications  

Microsoft Academic Search

Papers are presented on air-traffic control radar, surveillance radar, missile guidance radar, and high-performance tactical three-dimensional radar. Also considered are the airborne early warning radar, the Foxhunter airborne intercept radar, and environmental remote sensing. Other topics include spaceborne SARs, the Pioneer Orbiter radar, and a bistatic pulse-Doppler intruder-detection radar.

Merrill I. Skolnik

1988-01-01

210

Radar electronic warfare  

NASA Astrophysics Data System (ADS)

An overview of radar and electronic warfare is given. Definitions, common terms, and principles of radar and electronic warfare, and simple analyses of interactions between radar systems and electronic countermeasures (ECM) are presented. Electronic counter-countermeasure and electronic support measures are discussed. Background material in mathematics, electromagnetics, and probability necessary for an understanding of radar and electronic warfare is given and radar tracking models are examined. The effects of various ECM emissions on radar systems are analyzed, including discussion of active ECM and angle scanning systems, angle measurement in monopulse, and automatic gain control.

Golden, August, Jr.

211

Cold tests of HOM absorber material for the ARIEL eLINAC at TRIUMF  

NASA Astrophysics Data System (ADS)

At TRIUMF development of a 50 MeV electron accelerator is well under way. Five 1.3 GHz, superconducting 9-cell cavities will accelerate 10 mA electrons to a production target to produce rare isotopes. Each cavity will provide 10 MV accelerating voltage. Plans to upgrade the accelerator in the future to a small ring with ERL capabilities requires that the shunt impedance of the dipole higher order modes to be less than 10M? . The design of the accelerator incorporates beam line absorbers to reduce the shunt impedance of potentially dangerous dipole modes.

Kolb, P.; Laxdal, R. E.; Zvyagintsev, V.; Chao, Y. C.; Amini, B.

2014-01-01

212

Lunar radar backscatter studies  

NASA Technical Reports Server (NTRS)

The lunar surface material in the Plato area is characterized using Earth based visual, infrared, and radar signatures. Radar scattering in the lunar regolith with an existing optical scattering computer program is modeled. Mapping with 1 to 2 km resolution of the Moon using a 70 cm Arecibo radar is presented.

Thompson, T. W.

1979-01-01

213

Composition for absorbing hydrogen  

DOEpatents

A hydrogen absorbing composition. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.

Heung, Leung K. (Aiken, SC); Wicks, George G. (Aiken, SC); Enz, Glenn L. (N. Augusta, SC)

1995-01-01

214

Two-photon or higher-order absorbing optical materials for generation of reactive species  

NASA Technical Reports Server (NTRS)

Disclosed are highly efficient multiphoton absorbing compounds and methods of their use. The compounds generally include a bridge of pi-conjugated bonds connecting electron donating groups or electron accepting groups. The bridge may be substituted with a variety of substituents as well. Solubility, lipophilicity, absorption maxima and other characteristics of the compounds may be tailored by changing the electron donating groups or electron accepting groups, the substituents attached to or the length of the pi-conjugated bridge. Numerous photophysical and photochemical methods are enabled by converting these compounds to electronically excited states upon simultaneous absorption of at least two photons of radiation. The compounds have large two-photon or higher-order absorptivities such that upon absorption, one or more Lewis acidic species, Lewis basic species, radical species or ionic species are formed.

Cumpston, Brian (Inventor); Lipson, Matthew (Inventor); Marder, Seth R. (Inventor); Perry, Joseph W. (Inventor)

2003-01-01

215

Two-photon or higher-order absorbing optical materials for generation of reactive species  

NASA Technical Reports Server (NTRS)

Disclosed are highly efficient multiphoton absorbing compounds and methods of their use. The compounds generally include a bridge of pi-conjugated bonds connecting electron donating groups or electron accepting groups. The bridge may be substituted with a variety of substituents as well. Solubility, lipophilicity, absorption maxima and other characteristics of the compounds may be tailored by changing the electron donating groups or electron accepting groups, the substituents attached to or the length of the pi-conjugated bridge. Numerous photophysical and photochemical methods are enabled by converting these compounds to electronically excited states upon simultaneous absorption of at least two photons of radiation. The compounds have large two-photon or higher-order absorptivities such that upon absorption, one or more Lewis acidic species, Lewis basic species, radical species or ionic species are formed.

Cumpston, Brian (Inventor); Lipson, Matthew (Inventor); Marder, Seth R (Inventor); Perry, Joseph W (Inventor)

2007-01-01

216

Material Property Estimation for Direct Detection of DNAPL using Integrated Ground-Penetrating Radar Velocity, Imaging and Attribute Analysis  

SciTech Connect

The focus of this project is direct detection of DNAPL's specifically chlorinated solvents, via material property estimation from multi-fold surface ground-penetrating radar (GPR) data. We combine state-of-the-art GPR processing methodology with quantitative attribute analysis and material property estimation to determine the location and extent of residual and/or pooled DNAPL in both the vadose and saturated zones. An important byproduct of our research is state-of-the-art imaging which allows us to pinpoint attribute anomalies, characterize stratigraphy, identify fracture zones, and locate buried objects.

John H. Bradford; Stephen Holbrook; Scott B. Smithson

2004-12-09

217

Material Property Estimation for Direct Detection of DNAPL using Integrated Ground-Penetrating Radar Velocity, Imaging and Attribute Analysis  

SciTech Connect

The focus of this project is direct detection of DNAPLs, specifically chlorinated solvents, via material property estimation from multi-fold surface ground-penetrating radar (GPR) data. We combine state-of-the-art GPR processing methodology with quantitative attribute analysis and material property estimation to determine the location and extent of residual and/or pooled DNAPL in both the vadose and saturated zones. An important byproduct of our research is state-of-the-art imaging which allows us to pinpoint attribute anomalies, characterize stratigraphy, identify fracture zones, and locate buried objects.

Bradford, John H.; Holbrook, W. Stephen; Smithson, Scott B.

2004-12-31

218

Absorbing properties and structural design of microwave absorbers based on carbonyl iron and barium ferrite  

NASA Astrophysics Data System (ADS)

Carbonyl iron and barium ferrite powder (BaZn 1.5Co 0.5Fe 16O 27) were prepared in this work. The complex permittivity and permeability spectra for rubber radar absorbing materials employing carbonyl iron and barium ferrite powders were measured. A database describing the frequency dependence of the permittivities and permeabilities of the carbonyl iron and barium ferrite microwave absorbers with various powder percentage compositions in 2-18 GHz was created. Based on the database, the single-layer and double-layer absorbers were designed and prepared, and their microwave absorption properties were investigated. The results indicate that the carbonyl iron powder prepared via thermal decomposition of iron pentacarbonyl is single cubic iron and of spherical shape. The barium ferrite powder is single W-type ferrite and a hexagonal flake. The absorption band of the double-layer microwave absorber is obviously more than that of the single-layer absorber. The double-layer microwave absorbers with reflection loss <-13 dB over the range of 6-18 GHz and reflection loss <-8 dB over the range of 2-18 GHz were prepared. The thicknesses of the absorbers are only 3.6 and 3.7 mm, respectively.

Feng, Y. B.; Qiu, T.; Shen, C. Y.

2007-11-01

219

Results of the Workshop on Microwave-Absorbing Materials for Accelerators (MAMA): A Personal View  

Microsoft Academic Search

The first workshop on the properties and uses of special materials for absorption of microwaves in particle accelerators was held at the Continuous Electron Beam Accelerator Facility (CEBAF) in Newport News, February 22-24, 1993. The meeting's purpose was to review the advances of ceramic and materials science and to describe the accelerator projects the success of which strongly depends on

I. E. Campisi

1993-01-01

220

Corrosion resistant neutron absorbing coatings  

DOEpatents

A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

Choi, Jor-Shan (El Cerrito, CA); Farmer, Joseph C. (Tracy, CA); Lee, Chuck K. (Hayward, CA); Walker, Jeffrey (Gaithersburg, MD); Russell, Paige (Las Vegas, NV); Kirkwood, Jon (Saint Leonard, MD); Yang, Nancy (Lafayette, CA); Champagne, Victor (Oxford, PA)

2012-05-29

221

Corrosion resistant neutron absorbing coatings  

DOEpatents

A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

Choi, Jor-Shan; Farmer, Joseph C; Lee, Chuck K; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

2013-11-12

222

Plasmonic materials based on ZnO films and their potential for developing broadband middle-infrared absorbers  

NASA Astrophysics Data System (ADS)

Noble metals such as gold and silver have been extensively used for plasmonic applications due to their ability to support plasmons, yet they suffer from high intrinsic losses. Alternative plasmonic materials that offer low loss and tunability are desired for a new generation of efficient and agile devices. In this paper, atomic layer deposition (ALD) grown ZnO is investigated as a candidate material for plasmonic applications. Optical constants of ZnO are investigated along with figures of merit pertaining to plasmonic waveguides. We show that ZnO can alleviate the trade-off between propagation length and mode confinement width owing to tunable dielectric properties. In order to demonstrate plasmonic resonances, we simulate a grating structure and computationally demonstrate an ultra-wide-band (4-15 ?m) infrared absorber.

Kesim, Yunus E.; Battal, Enes; Okyay, Ali K.

2014-07-01

223

Canyon transfer neutron absorber to fissile material ratio analysis. Revision 1  

SciTech Connect

Waste tank fissile material and non-fissile material estimates are used to evaluate criticality safety for the existing sludge inventory and batches of sludge sent to Extended Sludge Processing (ESP). This report documents the weight ratios of several non-fissile waste constituents to fissile waste constituents from canyon reprocessing waste streams. Weight ratios of Fe, Mn, Al, Mi, and U-238 to fissile material are calculated from monthly loss estimates from the F and H Canyon Low Heat Waste (LHW) and High Heat Waste (HHW) streams. The monthly weight ratios for Fe, Mn and U-238 are then compared to calculated minimum safe weight ratios. Documented minimum safe weight ratios for Al and Ni to fissile material are currently not available. Total mass data for the subject sludge constituents is provided along with scatter plots of the monthly weight ratios for each waste stream.

Clemmons, J.S.

1994-03-04

224

Radar-cross-section reduction of wind turbines. part 1.  

SciTech Connect

In recent years, increasing deployment of large wind-turbine farms has become an issue of growing concern for the radar community. The large radar cross section (RCS) presented by wind turbines interferes with radar operation, and the Doppler shift caused by blade rotation causes problems identifying and tracking moving targets. Each new wind-turbine farm installation must be carefully evaluated for potential disruption of radar operation for air defense, air traffic control, weather sensing, and other applications. Several approaches currently exist to minimize conflict between wind-turbine farms and radar installations, including procedural adjustments, radar upgrades, and proper choice of low-impact wind-farm sites, but each has problems with limited effectiveness or prohibitive cost. An alternative approach, heretofore not technically feasible, is to reduce the RCS of wind turbines to the extent that they can be installed near existing radar installations. This report summarizes efforts to reduce wind-turbine RCS, with a particular emphasis on the blades. The report begins with a survey of the wind-turbine RCS-reduction literature to establish a baseline for comparison. The following topics are then addressed: electromagnetic model development and validation, novel material development, integration into wind-turbine fabrication processes, integrated-absorber design, and wind-turbine RCS modeling. Related topics of interest, including alternative mitigation techniques (procedural, at-the-radar, etc.), an introduction to RCS and electromagnetic scattering, and RCS-reduction modeling techniques, can be found in a previous report.

Brock, Billy C.; Loui, Hung; McDonald, Jacob J.; Paquette, Joshua A.; Calkins, David A.; Miller, William K.; Allen, Steven E.; Clem, Paul Gilbert; Patitz, Ward E.

2012-03-05

225

Comparison of amorphous silicon absorber materials: Light-induced degradation and solar cell efficiency  

NASA Astrophysics Data System (ADS)

Several amorphous silicon (a-Si:H) deposition conditions have been reported to produce films that degrade least under light soaking when incorporated into a-Si:H solar cells. However, a systematic comparison of these a-Si:H materials has never been presented. In the present study, different plasma-enhanced chemical vapor deposition conditions, yielding standard low-pressure VHF a-Si:H, protocrystalline, polymorphous, and high-pressure RF a-Si:H materials, are compared with respect to their optical properties and their behavior when incorporated into single-junction solar cells. A wide deposition parameter space has been explored in the same deposition system varying hydrogen dilution, deposition pressure, temperature, frequency, and power. From the physics of layer growth, to layer properties, to solar cell performance and light-induced degradation, a consistent picture of a-Si:H materials that are currently used for a-Si:H solar cells emerges. The applications of these materials in single-junction, tandem, and triple-junction solar cells are discussed, as well as their deposition compatibility with rough substrates, taking into account aspects of voltage, current, and charge collection. In sum, this contributes to answering the question, "Which material is best for which type of solar cell?"

Stuckelberger, M.; Despeisse, M.; Bugnon, G.; Schüttauf, J.-W.; Haug, F.-J.; Ballif, C.

2013-10-01

226

The physical properties of black carbon and other light-absorbing material emitted from prescribed fires in the United States  

NASA Astrophysics Data System (ADS)

Black carbon (BC) aerosol emitted from fires absorbs light, leading to visibility degradation as well as regional and global climate impacts. Fires also emit a wide range of trace gases and particulates that can interact with emitted BC and alter its optical properties and atmospheric lifetime. Non-BC particulate species emitted by fires can also scatter and absorb light, leading to additional effects on visibility. Recent work has shown that certain organic species can absorb light strongly at shorter wavelengths, giving it a brown or yellow color. This material has been classified as brown carbon, though it is not yet well defined. Land managers must find a balance between the negative impacts of prescribed fire emissions on visibility and air quality and the need to prevent future catastrophic wildfire as well as manage ecosystems for habitat restoration or other purposes. This decision process requires accurate assessments of the visibility impacts of fire emissions, including BC and brown carbon, which in turn depend on their optical properties. We present recent laboratory and aircraft measurements of black carbon and aerosol optical properties emitted from biomass burning. All measurement campaigns included a single particle soot photometer (SP2) instrument capable of providing size-resolved measurements of BC mass and number distributions and mixing state, which are needed to separate the BC and brown carbon contributions to total light absorption. The laboratory experiments also included a three-wavelength photoacoustic spectrometer that provided accurate measurements of aerosol light absorption. The laboratory systems also characterized emissions after they had been treated with a thermal denuder to remove semi-volatile coatings, allowing an assessment of the role of non-BC coatings on bulk aerosol optical properties. Emissions were also aged in an environmental smog chamber to examine the role of secondary aerosol production on aerosol optical properties.

McMeeking, G. R.; Kreidenweis, S. M.; Yokelson, R. J.; Sullivan, A. P.; Lee, T.; Collett, J. L.; Fortner, E.; Onasch, T. B.; Akagi, S. K.; Taylor, J.; Coe, H.

2012-12-01

227

A summary of measurements of permittivities and permeabilities of some microwave absorbing materials  

NASA Astrophysics Data System (ADS)

This report presents results of measurements of permittivities and permeabilities of assorted materials collected by the U.S. Army Office of Low Observables Technology and Applications (LOTA), and by the U.S. Army Materials Technology Laboratory (MTL). The samples fell into the following categories: (1) Pure materials (Teflon, plexiglasses and casting plastic); (2) Metal-coated microspheres; (3) Carbospheres, both uncoated and metal coated; (4) Ferrites; (5) Magnetic metal flake; (6) Ceramic matrix composites; and (7) A standard paint. The data and its limitations and plans for additional testing are presented in the text. The most interesting results were obtained for a Rockwell Ferrite and for a 50/50 ferronickel flake which showed magnetic loss from 2 to 18 GHz.

Spurgeon, W. A.; Elrayess, M.; Dorsey, P.; Vittoria, C.

1990-05-01

228

Electromagnetic power absorber  

NASA Technical Reports Server (NTRS)

A structure is presented with a surface portion of dielectric material which passes electromagnetic radiation and with a portion below the surface which includes material that absorbs the radiation, the face of the structure being formed with numerous steep ridges. The steepness of the dielectric material results in a high proportion of the electromagnetic energy passing through the surface for absorption by the absorbing material under the surface. A backing of aluminum or other highly heat-conductive and reflective material lies under the face and has very steep protuberances supporting the absorbing and dielectric materials.

Iwasaki, R. S. (inventor)

1979-01-01

229

Analysis of SnS2 hyperdoped with V proposed as efficient absorber material  

NASA Astrophysics Data System (ADS)

Intermediate-band materials can improve the photovoltaic efficiency of solar cells through the absorption of two subband-gap photons that allow extra electron-hole pair formations. Previous theoretical and experimental findings support the proposal that the layered SnS2 compound, with a band-gap of around 2 eV, is a candidate for an intermediate-band material when it is doped with a specific transition-metal. In this work we characterize vanadium doped SnS2 using density functional theory at the dilution level experimentally found and including a dispersion correction combined with the site-occupancy-disorder method. In order to analyze the electronic characteristics that depend on geometry, two SnS2 polytypes partially substituted with vanadium in symmetry-adapted non-equivalent configurations were studied. In addition the magnetic configurations of vanadium in a SnS2 2H-polytype and its comparison with a 4H-polytype were also characterized. We demonstrate that a narrow intermediate-band is formed, when these dopant atoms are located in different layers. Our theoretical predictions confirm the recent experimental findings in which a paramagnetic intermediate-band material in a SnS2 2H-polytype with 10% vanadium concentration is obtained.

Seminovski, Yohanna; Palacios, Pablo; Wahnón, Perla

2014-10-01

230

Absorbed Gamma-Ray Doses due to Natural Radionuclides in Building Materials  

NASA Astrophysics Data System (ADS)

This work is devoted to the application of high-resolution gamma-ray spectrometry in the study of the effective dose coming from naturally occurring radionuclides, namely 40K, 232Th and 238U, present in building materials such as sand, cement, and granitic gravel. Four models were applied to estimate the effective dose and the hazard indices. The maximum estimated effective dose coming from the three reference rooms considered is 0.90(45) mSv/yr, and maximum internal hazard index is 0.77(24), both for the compact clay brick reference room. The principal gamma radiation sources are cement, sand and bricks.

Aguiar, Vitor A. P.; Medina, Nilberto H.; Moreira, Ramon H.; Silveira, Marcilei A. G.

2010-05-01

231

Scientists Identify New Family of Iron-Based Absorber Materials for Solar Cells (Fact Sheet), NREL Highlights, Science  

SciTech Connect

Use of Earth-abundant materials in solar absorber films is critical for expanding the reach of photovoltaic (PV) technologies. The use of Earth-abundant and inexpensive Fe in PV was proposed more than 25 years ago in the form of FeS{sub 2} pyrite - fool's gold. Unfortunately, the material has been plagued by performance problems that to this day are both persistent and not well understood. Researchers from the National Renewable Energy Laboratory (NREL) and Oregon State University, working collaboratively in the Center for Inverse Design, an Energy Frontier Research Center, have uncovered several new insights into the problems of FeS{sub 2}. They have used these advances to propose and implement design rules that can be used to identify new Fe-containing materials that can circumvent the limitations of FeS{sub 2} pyrite. The team has identified that it is the unavoidable metallic secondary phases and surface defects coexisting near the FeS{sub 2} thin-film surfaces and grain boundaries that limit its open-circuit voltage, rather than the S vacancies in the bulk, which has long been commonly assumed. The materials Fe{sub 2}SiS{sub 4} and Fe{sub 2}GeS{sub 4} hold considerable promise as PV absorbers. The ternary Si compound is especially attractive, as it contains three of the more abundant low-cost elements available today. The band gap (E{sub g} = 1.5 eV) from both theory and experiment is higher than those of c-Si and FeS{sub 2}, offering better absorption of the solar spectrum and potentially higher solar cell efficiencies. More importantly, these materials do not have metallic secondary phase problems as seen in FeS{sub 2}. High calculated formation energies of donor-type defects are consistent with p-type carriers in thin films and are prospects for high open-circuit voltages in cells.

Not Available

2011-10-01

232

Quantum Storage of Heralded Polarization Qubits in Birefringent and Anisotropically Absorbing Materials  

NASA Astrophysics Data System (ADS)

Storage of quantum information encoded into heralded single photons is an essential constituent of long-distance quantum communication based on quantum repeaters and of optical quantum information processing. The storage of photonic polarization qubits is, however, difficult because many materials are birefringent and have polarization-dependent absorption. Here we present a simple scheme that eliminates these polarization effects, and we demonstrate it by storing heralded polarization qubits into a solid-state quantum memory. The quantum memory is implemented with a biaxial yttrium orthosilicate (Y2SiO5) crystal doped with rare-earth ions. Heralded single photons generated from a filtered spontaneous parametric down-conversion source are stored, and quantum state tomography of the retrieved polarization state reveals an average fidelity of 97.5±0.4%, which is significantly higher than what is achievable with a measure-and-prepare strategy.

Clausen, Christoph; Bussières, Félix; Afzelius, Mikael; Gisin, Nicolas

2012-05-01

233

Surface Modification of Fuel Cladding Materials with Integral Fuel BUrnable Absorber Boron  

SciTech Connect

Integral fuel burnable absorgers (IFBA) are added to some rods in the fuel assembly to counteract excessive reactivity. These IFBA elements (usually boron or gadolinium) are presently incorporated in the U)2 pellets either by mixing in the pellets or as coatings on the pellet surface. In either case, the incorporation of ifba into the fuel has to be performed in a nuclear-regulated facility that is physically separated from the main plant. These operations tend to be costly and can add from 20 to 30% to the manufacturing cost of the fuel. The goal of this NEER research project was to develop an alternative approach that involves incorporation of IFBA element boron at the surface of the fuel cladding material.

Dr. Kumar Sridharan; Dr. Todd Allen; Jesse Gudmundson; Benjamin Maier

2008-11-03

234

The properties of the absorbing and line-emitting material in IGR J16318 - 4848  

NASA Astrophysics Data System (ADS)

We have performed a detailed analysis of the XMM-Newton observation of IGR J16318-4848, to study the properties of the matter responsible for the obscuration and for the emission of Fe and Ni lines. Even if the line-of-sight material has a column density of about 2 × 1024 cm-2, from the Fe K? line EW and Compton Shoulder we argue that the matter should have an average column density of a few ×1023 cm-2, along with a covering factor of about 0.1-0.2. The iron K? line varies on time-scales as short as 1000 s, implying a size of the emitting region smaller than about 3 × 1013 cm. The flux of the line roughly follows the variations of the continuum, but not exactly, suggesting a variation of the geometrical properties of the emitting region on similar time-scales.

Matt, Giorgio; Guainazzi, Matteo

2003-05-01

235

The Properties of the Absorbing and Line Emitting Material in IGR J16318-4848  

NASA Astrophysics Data System (ADS)

We analyzed the 2003 Target of Opportunity XMM-Newton observation of IGR J16318-4848, to derive the properties of the matter responsible for the obscuration and for the emission of Fe and Ni lines. The line of sight material has a column density of about 2×1024 cm-2 but, from the Fe K? line EW and Compton Shoulder, we argue that the average column density is a few ×1023 cm-2, while the covering factor is about 0.1-0.2. The iron K? line varies on time scales as short as 1000 s, implying a size of the emitting region less than 3×1013 cm. An ongoing XMM-Newton/INTEGRAL monitoring campaign is confirming the non-transient nature of the source.

Matt, Giorgio; Guainazzi, M.

2005-06-01

236

Efficiency of ablative loading of material upon the fast-electron transfer of absorbed laser energy  

SciTech Connect

We present the results of experiments on the short-term irradiation of a solid material by a laser beam. The data testify to a rise in efficiency of the energy transfer from the laser pulse to a shock wave due to the fast-electron energy transfer. The experiments were performed with massive aluminium targets on the PALS iodine laser, whose pulse duration (0.4 ns) was much shorter than the time of shock decay and crater formation in the target (50-200 ns). The irradiation experiments were carried out using the fundamental laser harmonic (1.315 {mu}m) with an energy of 360 J. The greater part of the experiments were performed for the radiation intensity exceeding 10{sup 15} W cm{sup -2}, which corresponded to the efficient generation of fast electrons under the conditions where the relatively long-wavelength iodine-laser radiation was employed. The irradiation intensity was varied by varying the laser beam radius for a specified pulse energy. (interaction of laser radiation with matter. laser plasma)

Gus'kov, Sergei Yu [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Kasperczuk, A; Pisarczyk, T; Borodziuk, S [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Kalal, M; Limpouch, J [Czech Technical University, Prague (Czech Republic); Ullschmied, J [Institute of Plasma Physics AS CR, Prague (Czech Republic); Krousky, E; Masek, K; Pfeifer, M; Rohlena, K; Skala, J [Institute of Physics, Czech Academy of Sciences, Prague (Czech Republic); Pisarczyk, P [Warsaw University of Technology, Warsaw (Poland)

2006-05-31

237

Synthesis and characterisation of Copper Zinc Tin Sulphide (CZTS) compound for absorber material in solar-cells  

NASA Astrophysics Data System (ADS)

The development of thin-film semiconductor compounds, such as Copper Indium Gallium Selenide (CIGS), has caused remarkable progress in the field of thin-film photovoltaics. However, the scarcity and the increasing prices of indium impose the hunt for alternative materials. The Copper Zinc Tin Sulphide (CZTS) is one of the promising emerging materials with Kesterite-type crystal structure and favourable material properties like high absorption co-efficient and direct band-gap. Moreover, all the constituent elements of CZTS are non-toxic and aplenty on the earth-crust, making it a potential candidate for the thin-film photovoltaics. Here we report the synthesis of CZTS powder from its constituent elements, viz. copper, zinc, tin and sulphur, in an evacuated Quartz ampoule at 1030 K temperature. The sulphur content in the raw mixture in the ampoule was varied and optimised in order to attain the desired atomic stoichiometry of the compound. The synthesised powder was characterised by X-Ray diffraction technique (XRD), Raman Scattering Spectroscopy, Energy Dispersive Analysis of X-Ray (EDAX) and UV-Visible Absorption Spectra. The XRD Patterns of the synthesised compound show the preferred orientation of (112), (220) and (312) planes, confirming the Kesterite structure of CZTS. The chemical composition of the powder was analysed by EDAX and shows good atomic stoichiometry of the constituent elements in the CZTS compound. The UV-Vis absorption spectra confirm the direct band-gap of about 1.45 eV, which is quite close to the optimum value for the semiconductor material as an absorber in solar-cells.

Kheraj, Vipul; Patel, K. K.; Patel, S. J.; Shah, D. V.

2013-01-01

238

1998 SPIE Smart Structures and Materials Conf. Paper #332919/332742 High bandwidth tunability in a smart vibration absorber  

E-print Network

specific mass load. The magnetoelastic properties of Terfenol­D lead to changes in its elastic modulus of the absorber core's elastic modulus is accomplished by varying the current into the solenoid, which varies tuned. A decrease in the absorber's damping increases vibration attenuation over the bandwidth

Flatau, Alison B.

239

Rhea's Surface: Ice Properties Measured by Radar.  

NASA Astrophysics Data System (ADS)

We obtained echoes from the leading and trailing hemispheres of Rhea in January 2004 using the Arecibo Observatory's 13-cm radar system. The transmitted signal was circularly polarized and strong echoes were received in both the opposite circular (OC) sense to that transmitted and the same circular (SC) sense. Rhea's mean total cross section normalized by projected area is 1.32±0.10 and the mean circular polarization ratio, the ratio of SC echo power to OC echo power, is 1.17±0.12. The reflectivity of the leading hemisphere may be slightly lower than that of the trailing hemisphere by about 10%, although the polarization ratio appears to vary less. The cross section and polarization ratio are similar to those of the icy Galilean satellites and closest to Ganymede's. For these bodies the high radar backscatter cross sections and high polarization ratios are due to an efficient multiple scattering mechanism in the cold, relatively clean water ice surfaces which have very low propagation loss at radio wavelengths. Rhea's surface appears to be exhibiting a similar effect. Rhea's echo spectra are broad, again similar to those of the icy Galilean satellites, and consistent with a multiple scattering mechanism. In contrast, the bright icy hemisphere of Rhea's sibling Iapetus is significantly more radar dark with a radar reflectivity roughly 10% of Rhea's (Black et al., Science, v304, 2004). On Iapetus this great reduction in scattering efficiency is most likely caused by a radar absorber in the ice, possibly ammonia compounds or buried non-ice material from its dark hemisphere. Rhea's surface ice must therefore be relatively free of contaminants, and have a purity similar to Ganymede's. These observations can constrain the concentration of ammonia in the near surface which would be a strong absorber even in amounts of only a few percent. We acknowledge support by NASA's PG&G program.

Black, G.; Campbell, D.

2004-11-01

240

Effect of Salinity on the Dielectric Properties of Geological Materials: Implication for Soil Moisture Detection by Means of Radar Remote Sensing  

Microsoft Academic Search

We consider the exploitation of dielectric properties of saline deposits for the detection and mapping of moisture in arid regions on both Earth and Mars. We present simulated and experimental study in order to assess the effect of salinity on the complex permittivity of geological materials and, therefore, on the radar backscattering coefficient in the [1-7 GHz] frequency range. Laboratory

Yannick Lasne; Philippe Paillou; Anthony Freeman; Tom Farr; Kyle C. McDonald; Gilles Ruffie; Jean-Marie Malezieux; Bruce Chapman; François Demontoux

2008-01-01

241

Tailoring The Microwave Permittivity And Permeability Of Composite Materials  

E-print Network

selective surfaces such as bandpass and lowpass filters as well as radar absorbing materials1 Tailoring The Microwave Permittivity And Permeability Of Composite Materials Kenneth M. Bober/Lowell, Lowell, MA 01854 ABSTRACT The microwave permittivity( r ) and permeability( r ) of composite materials

Massachusetts at Lowell, University of

242

Multiband terahertz metamaterial absorber  

Microsoft Academic Search

This paper reports the design of a multiband metamaterial (MM) absorber in the terahertz region. Theoretical and simulated results show that the absorber has four distinct and strong absorption points at 1.69, 2.76, 3.41 and 5.06 THz, which are consistent with `fingerprints' of some explosive materials. The retrieved material parameters show that the impedance of MM could be tuned to

Chao Gu; Shao-Bo Qu; Zhi-Bin Pei; Zhuo Xu; Jia Liu; Wei Gu

2011-01-01

243

Multiband terahertz metamaterial absorber  

NASA Astrophysics Data System (ADS)

This paper reports the design of a multiband metamaterial (MM) absorber in the terahertz region. Theoretical and simulated results show that the absorber has four distinct and strong absorption points at 1.69, 2.76, 3.41 and 5.06 THz, which are consistent with ‘fingerprints’ of some explosive materials. The retrieved material parameters show that the impedance of MM could be tuned to match approximately the impedance of the free space to minimise the reflectance at absorption frequencies and large power loss exists at absorption frequencies. The distribution of the power loss indicates that the absorber is an excellent electromagnetic wave collector: the wave is first trapped and reinforced in certain specific locations and then consumed. This multiband absorber has applications in the detection of explosives and materials characterisation.

Gu, Chao; Qu, Shao-Bo; Pei, Zhi-Bin; Xu, Zhuo; Liu, Jia; Gu, Wei

2011-01-01

244

Light scattering by dust particles (PROGRA2 experiment): size and structure effects for transparent and absorbing materials  

NASA Astrophysics Data System (ADS)

1- Introduction Cometary and possibly interplanetary dust particles seem to be mainly made of agglomerates of submicron and micron-sized grains. These particles are among the most primitive in our solar system. Regoliths on asteroidal and planetary surfaces seem to be loose materials produced by impinging meteorites on the surface of small bodies. Comparing their physical properties is thus fundamental to understand their evolution. To interpret remote observations of solar light scattered by dust particles and regoliths, it is necessary to use numerical and experimental simulations [1,2,3]. 2- PROGRA2 experiment PROGRA2 instruments are polarimeters; the light sources are two randomly polarized lasers (632.8 nm and 543.5 nm). Levitating particles (in microgravity or lifted by an air-draught) are studied by imaging polarimetry. Details on the instruments can be found in [4,5]. 3- Samples Two kinds of samples are studied: compact particles in the (1-400) micrometer size range and fluffy aggregates in the same size range, made from submicron and micronsized grains. The materials are transparent silica and absorbing carbon. Some deposited particles are huge agglomerates of micron-sized grains produced by random ballistic deposition of single grains [6,7] or produced by evaporation of mixtures in alcohol of fluffy aggregates of submicron-sized grains. Two samples are made of silica spheres coated by a carbonaceous black compound. Cometary analogues are mixtures of silica and amorphous carbon or Mg-Fe silicates mixed with amorphous carbon. 4- Results Phase curves and their main parameters (negative polarization at small phase angles and maximum polarization, Pmax, at 90-100° phase angle) for the different materials will be compared and related to the physical properties. For example, it is well known by numerical simulations and/or by experiments that the maximum polarization decreases when the size (submicrometer range) of the grains increases [2,8,9]. An inverse rule is found for compact grains, larger than the wavelength. Mixtures of fluffy silica and fined grained amorphous carbon or better Mg-Fe silicates with amorphous carbon are excellent cometary particles analogues (as light scattering is concerned) if they are mixed with some compact micron-sized grains [9]. Nevertheless the structure of the aggregates seems to play a major role to obtain the negative branch found on the polarimetric phase curves for comets [10]. 5- Discussion and conclusions The experiments purpose is to help to disentangle the different physical properties of dust particles that can be deduced from remote observations (cometary dust, regoliths). Differences between the main parameters influencing the variations of Pmax and the presence of a negative branch on the polarimetric phase curves for lifted and deposited particles (in huge agglomerates or not) will be discussed. Acknowledgments: Technische Universität Carolo-Wilhelmina, Braunschweig, Deutschland (Pr Blum, Dr Schräpler); University of New Mexico, Albuquerque, USA (Pr Rietmeijer); NASA Goddard Space Flight Center, Maryland, USA (Dr Nuth) References [1] A.C. Levasseur-Regourd, E. Hadamcik, JQSRT 79-80, 903 (2003) [2] J. Lasue, A.C. Levasseur-Regourd, JQSRT 100, 220 (2006) [3] J.-B. Renard et al., ASR 31, 2511 (2003) [4] J.-B. Renard et al., Appl. Opt. 91, 609 (2002) [5] E. Hadamcik et al., JQSRT 106, 74 (2007) [6] J. Blum, R. Schreapler, Phys. Rev Let 93:115031 (2004) [7] J. Blum et al., Astrophys J 652, 1768 (2006) [8] R. West, Appl. Opt. 30, 5216 (1991) [9] E. Hadamcik et al., JQSRT 100, 143 (2006) [10] E. Hadamcik et al., Icarus, in press (2007)

Hadamcik, E.; Renard, J.-B.; Lasue, J.; Levasseur-Regourd, A. C.

2007-08-01

245

Extracting material parameters from x-ray attenuation: a CT feasibility study using kilovoltage synchrotron x-rays incident upon low atomic number absorbers  

Microsoft Academic Search

The work reported here is a feasibility study of the extraction of material parameters from measurements of the linear x-ray attenuation coefficient of low atomic number absorbers. Computed tomography (CT) scans of small samples containing several liquids and solids were carried out with synchrotron radiation at the Australian National Beamline Facility (BL 20B) in Japan. Average values of the x-ray

B J Kirby; J R Davis; J A Grant; M J Morgan

2003-01-01

246

Micropower impulse radar imaging  

SciTech Connect

From designs developed at the Lawrence Livermore National Laboratory (LLNL) in radar and imaging technologies, there exists the potential for a variety of applications in both public and private sectors. Presently tests are being conducted for the detection of buried mines and the analysis of civil structures. These new systems use a patented ultra-wide band (impulse) radar technology known as Micropower Impulse Radar (GPR) imaging systems. LLNL has also developed signal processing software capable of producing 2-D and 3-D images of objects embedded in materials such as soil, wood and concrete. My assignment while at LLNL has focused on the testing of different radar configurations and applications, as well as assisting in the creation of computer algorithms which enable the radar to scan target areas of different geometeries.

Hall, M.S.

1995-11-01

247

Radar illusion via metamaterials  

NASA Astrophysics Data System (ADS)

An optical illusion is an image of a real target perceived by the eye that is deceptive or misleading due to a physiological illusion or a specific visual trick. The recently developed metamaterials provide efficient approaches to generate a perfect optical illusion. However, all existing research on metamaterial illusions has been limited to theory and numerical simulations. Here, we propose the concept of a radar illusion, which can make the electromagnetic (EM) image of a target gathered by radar look like a different target, and we realize a radar illusion device experimentally to change the radar image of a metallic target into a dielectric target with predesigned size and material parameters. It is well known that the radar signatures of metallic and dielectric objects are significantly different. However, when a metallic target is enclosed by the proposed illusion device, its EM scattering characteristics will be identical to that of a predesigned dielectric object under the illumination of radar waves. Such an illusion device will confuse the radar, and hence the real EM properties of the metallic target cannot be perceived. We designed and fabricated the radar illusion device using artificial metamaterials in the microwave frequency, and good illusion performances are observed in the experimental results.

Jiang, Wei Xiang; Cui, Tie Jun

2011-02-01

248

Dependence of Yb-169 absorbed dose energy correction factors on self-attenuation in source material and photon buildup in water  

SciTech Connect

Purpose: Absorbed dose energy correction factors, used to convert the absorbed dose deposited in a LiF thermoluminescent dosimeter (TLD) into the clinically relevant absorbed dose to water, were obtained for both spherical volumetric sources and for the model 4140 HDR Yb-169 source. These correction factors have a strong energy dependence below 200 keV; therefore, spectral changes were quantified as Yb-169 photons traveled through both source material (Yb{sub 2}O{sub 3}) and water with the corresponding absorbed dose energy correction factors, f(r,{theta}), calculated as a function of location in a phantom. Methods: Using the MCNP5 Monte Carlo radiation transport simulation program, the Yb-169 spectrum emerging from spherical Yb{sub 2}O{sub 3} sources (density 6.9 g/cm{sup 3}) with radii between 0.2 and 0.9 mm were analyzed and their behavior compared against those for a point-source. The absorbed dose deposited to both LiF and H{sub 2}O materials was analyzed at phantom depths of 0.1-10 cm for each source radius and the absorbed dose energy correction factor calculated as the ratio of the absorbed dose to water to that of LiF. Absorbed dose energy correction factors for the Model 4140 Yb-169 HDR brachytherapy source similarly were obtained and compared against those calculated for the Model M-19 Ir-192 HDR source. Results: The Yb-169 average spectral energy, emerging from Yb{sub 2}O{sub 3} spherical sources 0.2-0.9 mm in radius, was observed to harden from 7% to 29%; as these photons traveled through the water phantom, the photon average energy softened by as much as 28% at a depth of 10 cm. Spectral softening was dependent on the measurement depth in the phantom. Energy correction factors were found to vary both as a function of source radius and phantom depth by as much as 10% for spherical Yb{sub 2}O{sub 3} sources. The Model 4140 Yb-169 energy correction factors depended on both phantom depth and reference angle and were found to vary by more than 10% between depths of 1 and 10 cm and angles of 0 deg. and 180 deg. This was in contrast to that of the Model M-19 Ir-192 source which exhibited approximately 3.5%-4.4% variation in its energy correction factors from phantom depths of 0.5-10 cm. The absorbed dose energy correction factor for the Ir-192 source, on the other hand, was independent of angle to within 1%. Conclusions: The application of a single energy correction factor for Yb-169 TLD based dosimetry would introduce a high degree of measurement uncertainty that may not be reasonable for the clinical characterization of a brachytherapy source; rather, an absorbed dose energy correction function will need to be developed for these sources. This correction function should be specific to each source model, type of TLD used, and to the experimental setup to obtain accurate and precise dosimetric measurements.

Medich, David C.; Munro, John J. III [Radiation Laboratory, University of Massachusetts Lowell, 1 University Avenue, Lowell, Massachusetts 01854 (United States); Source Production and Equipment Co., Inc., 113 Teal Street, St. Rose, Louisiana 70087 (United States)

2010-05-15

249

Material Property Estimation for Direct Detection of DNAPL using Integrated Ground-Penetrating Radar Velocity, Imaging and Attribute Analysis  

SciTech Connect

The focus of our work is direct detection of DNAPLs, specifically chlorinated solvents, via material property estimation from surface ground-penetrating radar (GPR) data. We combine sophisticated GPR processing methodology with quantitative attribute analysis and material property estimation to determine the location and extent of residual and/or pooled DNAPL in both the vadose and saturated zones. An important byproduct of our research is state-of-the-art imaging which allows us to pinpoint attribute anomalies, characterize stratigraphy, identify fracture zones, and locate buried objects. Implementation and verification of these methodologies will be a significant advance in GPR research and in meeting DOE's need for reliable in-situ characterization of DNAPL contamination. Chlorinated solvents have much lower electric permittivity and conductivity than water. An electrical property contrast is induced when solvents displace water in the sediment column resulting in an anomalous GPR signature. To directly identify zones of DNAPL contamination, we focus on three aspects of reflected wave behavior--propagation velocity, frequency dependent attenuation, and amplitude variation with offset (AVO). Velocity analysis provides a direct estimate of electric permittivity, attenuation analysis provides a measure of conductivity, and AVO behavior is used to estimate the permittivity ratio at a reflecting boundary. Areas of anomalously low electric permittivity and conductivity are identified as potential DNAPL rich zones. Preliminary work illustrated significant potential for quantitative direct detection methodologies in identifying shallow DNAPL source zones. It is now necessary to verify these methodologies in a field setting. To this end, the project is field oriented and has three primary objectives: (1) Develop a suite of methodologies for direct detection of DNAPLs from surface GPR data (2) Controlled field verification at well characterized, contaminated sites (3) Exploratory contaminant detection in a field setting to be verified through direct sampling Field experiments are being conducted at the Savannah River and Hanford sites, and five DOD sites (Dover AFB, DE; McClellan AFB, CA; Port Hueneme, CA; Wurtsmith AFB, MI; Hill AFB, UT).

Bradford, John; Smithson, Scott B.; Holbrook, Stephen

2001-06-01

250

Radar principles  

NASA Technical Reports Server (NTRS)

Discussed here is a kind of radar called atmospheric radar, which has as its target clear air echoes from the earth's atmosphere produced by fluctuations of the atmospheric index of refraction. Topics reviewed include the vertical structure of the atmosphere, the radio refractive index and its fluctuations, the radar equation (a relation between transmitted and received power), radar equations for distributed targets and spectral echoes, near field correction, pulsed waveforms, the Doppler principle, and velocity field measurements.

Sato, Toru

1989-01-01

251

Measurement of the dielectric properties of dispersive materials over a wide frequency range  

Microsoft Academic Search

The propagation of electromagnetic waves through dispersive media forms the basis for a wide variety of applications. Rapid advances in materials have produced new products with tailored responses across frequency bands. Many of these new materials, such as radar absorbing material and photonic crystals, are dispersive in nature. This, in turn, has opened up the possibility for the exploitation of

L. D. Bacon; J. M. Lehr; L. L. Molina; R. A. Salazar

2003-01-01

252

Composite Materials Instructor: Kenneth M. Golden, golden@math.utah.edu  

E-print Network

, concrete, and radar absorbing coatings. Calculating the bulk or effective material properties of compositesComposite Materials Instructor: Kenneth M. Golden, golden@math.utah.edu Professor of Mathematics, JWB 333 Abstract Composite materials appear throughout the sciences and engineering, particularly

Golden, Kenneth M.

253

Sound Absorbers  

NASA Astrophysics Data System (ADS)

Sound absorption indicates the transformation of sound energy into heat. It is, for instance, employed to design the acoustics in rooms. The noise emitted by machinery and plants shall be reduced before arriving at a workplace; auditoria such as lecture rooms or concert halls require a certain reverberation time. Such design goals are realised by installing absorbing components at the walls with well-defined absorption characteristics, which are adjusted for corresponding demands. Sound absorbers also play an important role in acoustic capsules, ducts and screens to avoid sound immission from noise intensive environments into the neighbourhood.

Fuchs, H. V.; Möser, M.

254

Design and realization of one-dimensional double hetero-structure photonic crystals for infrared-radar stealth-compatible materials applications  

NASA Astrophysics Data System (ADS)

In this paper, a new type one-dimensional (1D) double hetero-structure composite photonic crystal (CPC) for infrared-radar stealth-compatible materials applications was proposed and studied numerically and experimentally. First, based on transfer matrix method of thin-film optical theory, the propagation characteristics of the proposed structure comprising a stack of different alternating micrometer-thick layers of germanium and zinc sulfide were investigated numerically. Calculation results exhibit that this 1D single hetero-structure PC could achieve a flat high reflectivity gradually with increasing the number of the alternating media layers in a single broadband range. Then, based on principles of distributed Bragg reflector micro-cavity, a 1D double hetero-structure CPC comprising four PCs with thickness of 0.797 ?m, 0.592 ?m, 1.480 ?m, and 2.114 ?m, respectively, was proposed. Calculation results exhibit that this CPC could achieve a high reflectance of greater than 0.99 in the wavelength ranges of 3-5 ?m and 8-14 ?m and agreed well with experiment. Further experiments exhibit that the infrared emissivity of the proposed CPC is as low as 0.073 and 0.042 in the wavelength ranges of 3-5 ?m and 8-12 ?m, respectively. In addition, the proposed CPC can be used to construct infrared-radar stealth-compatible materials due to its high transmittance in radar wave band.

Wang, Zhixun; Cheng, Yongzhi; Nie, Yan; Wang, Xian; Gong, Rongzhou

2014-08-01

255

Electromagnetic Wave Absorbing Technique Using Periodic Patterns for Low RCS Patch Array Antenna  

NASA Astrophysics Data System (ADS)

This paper presents an electromagnetic wave absorbing technique to reduce a radar cross-section (RCS) of a patch array antenna without compromising their antenna performance. The technique is based on periodic patterns, which is made of resistive materials. The 2×2 patch array antenna with a resonance frequency of 3.0 GHz was designed and fabricated. To reduce the RCS of the patch array antenna, the periodic patterns using a square patch element were proposed and applied to the surface between the four antenna patches. The printed lossy periodic patterns have radar absorbing performance at 12.0 GHz frequency. The measured results show that the lossy periodic patterns have no significant effect on the antenna radiation performance. On the other hand, the RCS is reduced by more than 98% compared to the conventional antenna at the target frequency.

Jang, Hong-Kyu; Lee, Yeon-Gwan; Shin, Jae-Hwan; Kim, Chun-Gon

2013-07-01

256

MOLDING CALCINED GYPSUM-BASED COMPOSITE MATERIAL FOR SOUND-ABSORBING PANELS DESTINED TO REDUCE ENVIRONMENTAL NOISE  

Microsoft Academic Search

The paper introduces a new composite material with molding ? calcined gypsum matrix and EP type polymers reinforcing material (bloated polystyrene) as flakes and granules The bloated polystyrene flakes, granules or powder addition had used in order to improve the heating and sonic properties of the composite material. The technological process of ?-calcined gypsum production has combined with a pneumatic

UNGUR-MARCU ANA PATRICIA; MIHAILA IOAN; POP P. ADRIAN

257

Material Property Estimation for Direct Detections of DNAPL using Integrated Ground-Penetrating Radar Velocity, Imaging and Attribute Analysis  

SciTech Connect

The focus of our work is direct detection of DNAPLs, specifically chlorinated solvents, via material property estimation from surface ground-penetrating radar (GPR) data. We combine sophisticated GPR processing methodology with quantitative attribute analysis and material property estimation to determine the location and extent of residual and/or pooled DNAPL in both the vadose and saturated zones. An important byproduct of our research is state-of-the-art imaging which allows us to pinpoint attribute anomalies, characterize stratigraphy, identify fracture zones, and locate buried objects. Implementation and verification of these methodologies will be a significant advance in GPR research and in meeting DOE's need for reliable in-situ characterization of DNAPL contamination. Chlorinated solvents have much lower electric permittivity and conductivity than water. An electrical property contrast is induced when solvents displace water in the sediment column resulting in an anomalous GPR signature. To directly identify zones of DNAPL contamination, we focus on three aspects of reflected wave behavior--propagation velocity, frequency dependent attenuation, and amplitude variation with offset (AVO). Velocity analysis provides a direct estimate of electric permittivity, attenuation analysis provides a measure of conductivity, and AVO behavior is used to estimate the permittivity ratio at a reflecting boundary. Areas of anomalously low electric permittivity and conductivity are identified as potential DNAPL rich zones. Preliminary work illustrated significant potential for quantitative direct detection methodologies in identifying shallow DNAPL source zones. It is now necessary to verify these methodologies in a field setting. To this end, the project is field oriented and has three primary objectives: (1) Develop a suite of methodologies for direct detection of DNAPLs from surface GPR data (2) Controlled field verification at well characterized, contaminated sites (3) Exploratory contaminant detection in a field setting to be verified through direct sampling Field experiments are being conducted at the Savannah River and Hanford sites, at five DOD sites (Dover AFB, DE; McClellan AFB, CA; Port Hueneme, CA; Wurtsmith AFB, MI; Hill AFB, UT), at a former refinery site near Cincinnati, Ohio, and at a creosote wood preserving site in Fayetville, NC.

Bradford, John; Smithson, Scott B.; Holbrook, W. Stephen

2004-06-14

258

Material Property Estimation for Direct Detection of DNAPL using Integrated Ground-Penetrating Radar Velocity, Imaging and Attribute Analysis  

SciTech Connect

The focus of our work is direct detection of DNAPLs, specifically chlorinated solvents, via material property estimation from surface ground-penetrating radar (GPR) data. We combine sophisticated GPR processing methodology with quantitative attribute analysis and material property estimation to determine the location and extent of residual and/or pooled DNAPL in both the vadose and saturated zones. An important byproduct of our research is state-of-the-art imaging which allows us to pinpoint attribute anomalies, characterize stratigraphy, identify fracture zones, and locate buried objects. Implementation and verification of these methodologies will be a significant advance in GPR research and in meeting DOE's need for reliable in-situ characterization of DNAPL contamination. Chlorinated solvents have much lower electric permittivity and conductivity than water. An electrical property contrast is induced when solvents displace water in the sediment column resulting in an anomalous GPR signature. To directly identify zones of DNAPL contamination, we focus on three aspects of reflected wave behavior--propagation velocity, frequency dependent attenuation, and amplitude variation with offset (AVO). Velocity analysis provides a direct estimate of electric permittivity, attenuation analysis provides a measure of conductivity, and AVO behavior is used to estimate the permittivity ratio at a reflecting boundary. Areas of anomalously low electric permittivity and conductivity are identified as potential DNAPL rich zones. Preliminary work illustrated significant potential for quantitative direct detection methodologies in identifying shallow DNAPL source zones. It is now necessary to verify these methodologies in a field setting. To this end, the project is field oriented and has three primary objectives: (1) Develop a suite of methodologies for direct detection of DNAPLs from surface GPR data (2) Controlled field verification at well characterized, contaminated sites (3) Exploratory contaminant detection in a field setting to be verified through direct sampling Field experiments are being conducted at the Savannah River and Hanford sites, at five DOD sites (Dover AFB, DE; McClellan AFB, CA; Port Hueneme, CA; Wurtsmith AFB, MI; Hill AFB, UT), at a former refinery site near Cincinnati, Ohio, and at a creosote wood preserving site in Fayetville, NC.

Bradford, John; Smithson, Scott B.; Holbrook, W. Stephen

2003-06-01

259

A broadband omnidirectional absorber based on a hetero-structure composed of epsilon-negative material and mu-negative material  

NASA Astrophysics Data System (ADS)

A broadband omnidirectional absorber which is realized by heterostructures containing a collision plasma layer and a zero - n? mirror is theoretically investigated. A collision plasma layer and an appropriate dielectric layer are put on the top of the PC. It is shown to absorb roughly 70% of all available electromagnetic wave in a relative omnidirectional absorption band width 244 MHz. The absorption band edge of the PC is influenced by the range of the reflection band gap. Meanwhile, the absorption range for the transverse magnetic (TM) wave decreases at large incident angle. Compared with some previous designs, our proposed structure has a relative flatter total absorption spectrum over a broad microwave frequency range and using a zero - n? gap as a mirror is insensitive to the incident angle. This kind of heterostructure offers additional opportunities to design novel optoelectronic devices.

Liu, Jian-Dong; Liu, Shao-Bin; Kong, Xiang-Kun; Dai, Yi

2014-06-01

260

Synthesis and characterisation of Copper Zinc Tin Sulphide (CZTS) compound for absorber material in solar-cells  

Microsoft Academic Search

The development of thin-film semiconductor compounds, such as Copper Indium Gallium Selenide (CIGS), has caused remarkable progress in the field of thin-film photovoltaics. However, the scarcity and the increasing prices of indium impose the hunt for alternative materials. The Copper Zinc Tin Sulphide (CZTS) is one of the promising emerging materials with Kesterite-type crystal structure and favourable material properties like

Vipul Kheraj; K. K. Patel; S. J. Patel

2013-01-01

261

Theoretical and experimental study of the diffuse transmission of light through highly concentrated absorbing and scattering materials. Part I: Monte-Carlo simulations  

NASA Astrophysics Data System (ADS)

In many technical materials and commercial products like sunscreen or paint high particle and absorber concentrations are present. An important parameter for slabs of these materials is the diffuse transmission of light, which quantifies the total amount of directly and diffusely transmitted light. Due to the high content of scattering particles not only multiple scattering but also additional dependent scattering occurs. Hence, simple analytical models cannot be applied to calculate the diffuse transmission. In this work a Monte-Carlo program for the calculation of the diffuse transmission of light through dispersions in slab-like geometry containing high concentrations of scattering particles and absorbers is presented and discussed in detail. Mie theory is applied for the calculation of the scattering properties of the samples. Additionally, dependent scattering is considered in two different models, the well-known hard sphere model in the Percus-Yevick approximation (HSPYA) and the Yukawa model in the Mean Spherical Approximation (YMSA). Comparative experiments will show the accurateness of the program as well as its applicability to real samples [1].

Bressel, L.; Reich, O.

2014-10-01

262

Neutron Absorbing Alloys  

DOEpatents

The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

Mizia, Ronald E. (Idaho Falls, ID); Shaber, Eric L. (Idaho Falls, ID); DuPont, John N. (Whitehall, PA); Robino, Charles V. (Albuquerque, NM); Williams, David B. (Bethlehem, PA)

2004-05-04

263

Modeling and observing the effect of aerosols on meteor radar measurements of the atmosphere  

NASA Astrophysics Data System (ADS)

Measurements of the time taken for meteor radar echoes to decay can be used to estimate the ambipolar diffusion coefficient. If it is assumed that the decay of the radar echo is due strictly to the outward diffusion of ionized material in the meteor's trail, then echo decay is determined by temperature and pressure. However, dust particles or small ice crystals may absorb electrons from meteor trails, distorting their evolution and echo decay properties. A numerical method for modeling these processes is presented, with the prediction that absorbing aerosols can both decrease and increase the decay time of meteor radar echoes, depending on meteor, atmospheric, and radar parameters. This prediction is confirmed with observations taken using three 33 MHz and two 55 MHz radars at three locations in Australia and Antarctica, which display strong biases in the decay times of lower power echoes. It is suggested that both the accuracy and precision of atmospheric measurements are improved if only the highest power meteor echoes are used for estimates of the ambipolar diffusion coefficient.

Younger, J. P.; Reid, I. M.; Vincent, R. A.; Holdsworth, D. A.

2008-08-01

264

A major application of these modules--in which the solar absorber can be deposited on virtually any type of material and in any shape--is in the huge building-integrated photo-  

E-print Network

innovati n A major application of these modules--in which the solar absorber can be deposited on virtually any type of material and in any shape--is in the huge building-integrated photo- voltaics (BIPV diselenide (CIGS) material to be deposited directly onto common building materials such as metal, glass

265

Effect of short carbon fibers and MWCNTs on microwave absorbing properties of polyester composites containing nickel-coated carbon fibers  

Microsoft Academic Search

Multiphase composite materials filled with multiwall carbon nanotubes (MWCNTs), short nickel-coated carbon fibers and millimeter-long carbon fibers with various weight fractions and compositions are developed and used for the design of wide-band thin radar-absorbing screens. The effective complex permittivity of several composite samples is measured in the frequency range from 8GHz to 18GHz. The obtained results show that the addition

Igor Maria De Rosa; Adrian Dinescu; Fabrizio Sarasini; Maria Sabrina Sarto; Alessio Tamburrano

2010-01-01

266

Laser radar  

Microsoft Academic Search

The general theory of laser tracking and ranging and the principles governing the design of laser radar systems are examined. Major problems related to optimum reception of laser radar signals and parameter measurement are analyzed from the standpoint of the theory of statistical solutions. Attention is given to methods for processing trajectory measurements and various methods for obtaining noncoordinate information,

I. N. Matveev; V. V. Protopopov; I. N. Troitskii; N. D. Ustinov

1984-01-01

267

CONTROLLABLE ABSORBING STRUCTURE OF METAMATERIAL AT MICROWAVE  

Microsoft Academic Search

Akind of controllable metamaterial absorbing structure is presented in this paper, both transmission coefficient and single radar cross section (RCS) are electrically controlled. This structure is composed from split ring resonators (SRRs) and metallic wire arrays including pin diodes, pin diodes are periodically inserted at these wire arrays discontinuous, and they can be either in an on state or in

Zhanxian Xu; Weigan Lin; Lidu Kong

2007-01-01

268

The Contributions Regarding the Use of Microwave to Obtain Modeling Gypsum for Phonic-Absorbent Construction and Orthopedic Materials  

Microsoft Academic Search

The paper has presented some experiments realized at ``Congips'' Co. Oradea and University of Oradea, regarding of increase machining efficiency and quality for modeling gypsum plaster by using of microwave energy to gypsum ore roast. The elaboration process of microwave energy for modeling gypsum plaster has done on electromagnetic waves properties and specific properties for dielectric materials. Microwaves are radiations

P. A. Pop; P. A. Ungur; A. Caraban; F. Marcu

2009-01-01

269

The Contributions Regarding the Use of Microwave to Obtain Modeling Gypsum for Phonic-Absorbent Construction and Orthopedic Materials  

Microsoft Academic Search

The paper has presented some experiments realized at “Congips” Co. Oradea and University of Oradea, regarding of increase machining efficiency and quality for modeling gypsum plaster by using of microwave energy to gypsum ore roast. The elaboration process of microwave energy for modeling gypsum plaster has done on electromagnetic waves properties and specific properties for dielectric materials. Microwaves are radiations

P. A. Pop; P. A. Ungur; A. Caraban; F. Marcu

2009-01-01

270

Fabrication and electromagnetic characteristics of microwave absorbers containing carbon nanofibers and magnetic metals  

NASA Astrophysics Data System (ADS)

The ultimate aim of this study is the development of microwave absorbers containing both dielectric and magnetic lossy materials. Carbon nanofibers (CNFs) were used as dielectric lossy materials and NiFe particles were used as magnetic lossy materials. Total twelve specimens for the three types such as dielectric, magnetic and mixed radar absorbing materials (RAMs) were fabricated. Their complex permittivities and permeabilities in the range of 2~18 GHz were measured using the transmission line technique. The parametric studies in the X-band (8.2~12.4 GHz) for reflection loss characteristics of each specimen to design the single-layered RAMs were performed. The mixed RAMs generally showed the improved absorbing characteristics with thinner matching thickness. One of the mixed RAMs, S09 with the thickness of 2.00 mm had the 10 dB absorbing bandwidth of 4.0 GHz in the X-band. The experimental results for selected specimens were in very good agreements with simulation ones in terms of the overall reflection loss characteristics and 10 dB absorbing bandwidth.

Park, Ki-Yeon; Han, Jae-Hung; Lee, Sang-Bok; Kim, Jin-Bong; Yi, Jin-Woo; Lee, Sang-Kwan

2008-03-01

271

1560 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 49, NO. 11, NOVEMBER 2001 Modeling of Ground-Penetrating-Radar Antennas  

E-print Network

of Ground-Penetrating-Radar Antennas With Shields and Simulated Absorbers Ugur Oguz and Levent Gürel, Senior is employed to simulate ground-penetrating radars. Conducting shield walls and absorbers are used to reduce), ground- penetrating radar, perfectly matched layers (PMLs). I. INTRODUCTION THE finite-difference time

Gürel, Levent

272

Design of Salisbury screen absorbers using dielectric lossy sheets  

Microsoft Academic Search

In this study, we present design and manufacturing technology for the Salisbury screen type radar absorbing structure (RAS) in Xband. The RAS is composed of a dielectric lossy sheet and an E-glass fabric\\/epoxy composite laminate as the spacer. This RAS has a broader absorbing bandwidth and much thinner spacer than those of the conventional one which uses a 377 ?\\/?

Jinbong Kim

2011-01-01

273

Thin and broadband Salisbury screen absorber using Minkowski fractal structure  

Microsoft Academic Search

Salisbury screen radar absorber with high resistive surface is unconstrained by the restriction of 1\\/4 wavelength thickness of medium. EBG structure is an effective approach to realize it. This paper present a new type of Salisbury screen absorber based on one order Minkowski fractal surface with several symmetric patched resistors. Simulation results show that the total thickness is reduced dramatically

Yang Luo; Yuan Zhuang; Shouzheng Zhu

2009-01-01

274

Electronically tunable liquid crystal based Salisbury screen microwave absorber  

Microsoft Academic Search

In this paper we describe the design, manufacture and performance of an electrically thin (0.15 ¿) dynamically adaptive Salisbury screen absorber. The structure is backed by a high impedance surface which is constructed on a 250 ¿m thick liquid crystal substrate. The shift in the resonant frequency of the radar absorber is obtained by exploiting the voltage dependent anisotropic property

F. Che Seman; R. Cahill; V. F. Fusco

2009-01-01

275

Composite sandwich constructions for absorbing the electromagnetic waves  

Microsoft Academic Search

RAS (radar absorbing structures) is a key component for weapon systems such as aircrafts, warships, and missiles to achieve both the stealth performance by absorbing EM (Electromagnetic) waves incident on and load bearing capability. In this work, the RAS was fabricated as sandwich constructions composed of nanocomposite, carbon fabric\\/epoxy composite, and PVC foam. The nanocomposite composed of E-glass fabric, epoxy

Po Chul Kim; Dai Gil Lee

2009-01-01

276

RADAR POLARIMETRY AND INTERFEROMETRY: Past, Present and Future Trends  

Microsoft Academic Search

Recent developments of wave polarization effects in radar remote sensing are summarized in historical sequence resulting in Radar Polarimetry, Radar Interferometry and Polarimetric SAR Interferometry, which represent the current culmination in airborne and space borne 'Microwave Remote Sensing' technology. Whereas with radar polarimetry the textural fine-structure, target orientation, symmetries and material constituents can be recovered with considerable improvement above that

Wolfgang-Martin Boerner; Shane R. Cloude

277

Extracting material parameters from x-ray attenuation: a CT feasibility study using kilovoltage synchrotron x-rays incident upon low atomic number absorbers.  

PubMed

The work reported here is a feasibility study of the extraction of material parameters from measurements of the linear x-ray attenuation coefficient of low atomic number absorbers. Computed tomography (CT) scans of small samples containing several liquids and solids were carried out with synchrotron radiation at the Australian National Beamline Facility (BL 20B) in Japan. Average values of the x-ray linear attenuation coefficient were extracted for each material for x-ray energies ranging from 11 keV to 20.5 keV. The electron density was estimated by applying results derived from a parametrization of the x-ray linear attenuation coefficient first developed by Jackson and Hawkes and extended for this work. Average estimates for the electron density of triethanolamine and acetic acid were made to within +5.3% of the actual value. Other materials examined included furfuraldehyde, perspex and teflon, for which average estimates of the electron density were less than 10% in excess of the calculated value. PMID:14620065

Kirby, B J; Davis, J R; Grant, J A; Morgan, M J

2003-10-21

278

Characterization of the Mechanical Strength, Resorption Properties, and Histologic Characteristics of a Fully Absorbable Material (Poly-4-hydroxybutyrate--PHASIX Mesh) in a Porcine Model of Hernia Repair  

PubMed Central

Purpose. Poly-4-hydroxybutyrate (P4HB) is a naturally derived, absorbable polymer. P4HB has been manufactured into PHASIX Mesh and P4HB Plug designs for soft tissue repair. The objective of this study was to evaluate mechanical strength, resorption properties, and histologic characteristics in a porcine model. Methods. Bilateral defects were created in the abdominal wall of n = 20 Yucatan minipigs and repaired in a bridged fashion with PHASIX Mesh or P4HB Plug fixated with SorbaFix or permanent suture, respectively. Mechanical strength, resorption properties, and histologic characteristics were evaluated at 6, 12, 26, and 52 weeks (n = 5 each). Results. PHASIX Mesh and P4HB Plug repairs exhibited similar burst strength, stiffness, and molecular weight at all time points, with no significant differences detected between the two devices (P > 0.05). PHASIX Mesh and P4HB Plug repairs also demonstrated significantly greater burst strength and stiffness than native abdominal wall at all time points (P < 0.05), and material resorption increased significantly over time (P < 0.001). Inflammatory infiltrates were mononuclear, and both devices exhibited mild to moderate granulation tissue/vascularization. Conclusions. PHASIX Mesh and P4HB Plug demonstrated significant mechanical strength compared to native abdominal wall, despite significant material resorption over time. Histological assessment revealed a comparable mild inflammatory response and mild to moderate granulation tissue/vascularization. PMID:23781348

Deeken, Corey R.; Matthews, Brent D.

2013-01-01

279

Application of polarimetric synthetic aperture radar interferometry for land cover classification  

Microsoft Academic Search

The development of radar polarimetry and radar interferometry is advancing rapidly. The textural fine structure, target orientation, system metrics and material constituents can be recovered with radar polarimetry; while with radar interferometry, the elevation structure of a target can be explored. Polarimetric synthetic aperture radar interferometric (Pol-InSAR) is interferometry between all possible polarization channels at each end of the baseline.

Yang Zhen; Yang Ruliang

2002-01-01

280

1998 SPIE Smart Structures and Materials Conf. Paper #3329-19/3327-42 High bandwidth tunability in a smart vibration absorber  

E-print Network

. The magnetoelastic properties of Terfenol-D lead to changes in its elastic modulus with magnetic bias, known as the DE effect, in which the modulus can vary by over 160% [9]. Control of the absorber coreÃ?s elastic in the vibration level per input force at the frequency to which the absorber has been tuned. A decrease

Flatau, Alison B.

281

Absorber coatings' degradation  

SciTech Connect

This report is intended to document some of the Los Alamos efforts that have been carried out under the Department of Energy (DOE) Active Heating and Cooling Materials Reliability, Maintainability, and Exposure Testing program. Funding for these activities is obtained directly from DOE although they represent a variety of projects and coordination with other agencies. Major limitations to the use of solar energy are the uncertain reliability and lifetimes of solar systems. This program is aimed at determining material operating limitations, durabilities, and failure modes such that materials improvements can be made and lifetimes can be extended. Although many active and passive materials and systems are being studied at Los Alamos, this paper will concentrate on absorber coatings and degradation of these coatings.

Moore, S.W.

1984-01-01

282

Design, fabrication and characteristic of two-layer microwave absorbers composed of magnetic micropowder-rubber composites in X-band frequency range  

NASA Astrophysics Data System (ADS)

Both experimentally and theoretically, a two-layer microwave absorber exhibits the possibility of meeting the demand for effective radar absorbing materials. The design methodology is based on the modulus of permittivity (permeability) which obeys a logarithmic law of mixtures, and the loss tangent is related through a linear law of mixtures. A linear regression analysis performed on the data points provides constants that can be used to predict the effective parameters at different frequencies, and a program is presented that computes the optimum amount of magnetic micropowder and the required thickness for each layer. A two-step sulfur treatment is then applied to preparation of the two-layer absorber, vulcanized firstly by heating at 165 °C for 15 min and then at 150 °C for 4 h. Finally, tensile strength is experimentally investigated as well as power reflection coefficient. Test results indicate the two-layer absorber has excellent mechanical and microwave attenuation properties for X-band frequency.

He, Yanfei; Gong, Rongzhou; Li, Xiangcheng; Wang, Xian; Hu, Qifa

2007-03-01

283

Absorber for solar power.  

PubMed

A simple, economical absorber utilizing a new principle of operation to achieve very low reradiation losses while generating temperatures limited by material properties of quartz is described. Its performance is analyzed and indicates approximately 90% thermal efficiency and 73% conversion efficiency for an earth based unit with moderately concentrated (~tenfold) sunlight incident. It is consequently compatible with the most economic of concentrator mirrors (stamped) or mirrors deployable in space. Space applications are particularly attractive, as temperatures significantly below 300 K are possible and permit even higher conversion efficiency. PMID:20134700

Powell, W R

1974-10-01

284

Arecibo radar imagery of Mars: The major volcanic provinces  

NASA Astrophysics Data System (ADS)

We present Earth-based radar images of Mars obtained with the upgraded Arecibo S-band (? = 12.6 cm) radar during the 2005-2012 oppositions. The imaging was done using the same long-code delay-Doppler technique as for the earlier (pre-upgrade) imaging but at a much higher resolution (˜3 km) and, for some regions, a more favorable sub-Earth latitude. This has enabled us to make a more detailed and complete mapping of depolarized radar reflectivity (a proxy for small-scale surface roughness) over the major volcanic provinces of Tharsis, Elysium, and Amazonis. We find that vast portions of these regions are covered by radar-bright lava flows exhibiting circular polarization ratios close to unity, a characteristic that is uncommon for terrestrial lavas and that is a likely indicator of multiple scattering from extremely blocky or otherwise highly disrupted flow surfaces. All of the major volcanoes have radar-bright features on their shields, although the brightness distribution on Olympus Mons is very patchy and the summit plateau of Pavonis Mons is entirely radar-dark. The older minor shields (paterae and tholi) are largely or entirely radar-dark, which is consistent with mantling by dust or pyroclastic material. Other prominent radar-dark features include: the "fan-shaped deposits", possibly glacial, associated with the three major Tharsis Montes shields; various units of the Medusae Fossae Formation; a region south and west of Biblis Patera where "Stealth" deposits appear to obscure Tharsis flows; and a number of "dark-halo craters" with radar-absorbing ejecta blankets deposited atop surrounding bright flows. Several major bright features in Tharsis are associated with off-shield lava flows; these include the Olympus Mons basal plains, volcanic fields east and south of Pavonis Mons, the Daedalia Planum flows south of Arsia Mons, and a broad expanse of flows extending east from the Tharsis Montes to Echus Chasma. The radar-bright lava plains in Elysium are concentrated mainly in Cerberus and include the fluvio-volcanic channels of Athabasca Valles, Grjotá Valles, and Marte Valles, as well as an enigmatic region at the southern tip of the Cerberus basin. Some of the Cerberus bright features correspond to the distinctive "platy-ridged" flows identified in orbiter images. The radar-bright terrain in Amazonis Planitia comprises two distinct but contiguous sections: a northern section formed of lavas and sediments debouched from Marte Valles and a southern section whose volcanics may derive, in part, from local sources. This South Amazonis region shows perhaps the most complex radar-bright structure on Mars and includes features that correspond to platy-ridged flows similar to those in Cerberus.

Harmon, John K.; Nolan, Michael C.; Husmann, Diana I.; Campbell, Bruce A.

2012-08-01

285

Perfect Metamaterial Absorber  

Microsoft Academic Search

We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega). Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96%. Unlike conventional

N. I. Landy; S. Sajuyigbe; J. J. Mock; D. R. Smith; W. J. Padilla

2008-01-01

286

Weather Radar Fundamentals  

NSDL National Science Digital Library

This 2-hour module presents the fundamental principles of Doppler weather radar operation and how to interpret common weather phenomena using radar imagery. This is accomplished via conceptual animations and many interactive radar examples in which the user can practice interpreting both radar reflectivity and radar velocity imagery. Although intended as an accelerated introduction to understanding and using basic Doppler weather radar products, the module can also serve as an excellent refresher for more experienced users.

Comet

2012-03-21

287

A Thin and Broadband Absorber Using Double-Square Loops  

Microsoft Academic Search

This letter presents a design of thin and broadband absorbers using a two-dimensional (2-D) periodic array of double-square loops printed on a dielectric substrate. Lumped resistors are inserted into the four sides of the loops to absorb the incident electromagnetic wave. Simulated and measured results for the radar cross-section (RCS) of a finite 2-D array of double-square loops are in

Juan Yang; Zhongxiang Shen

2007-01-01

288

Fabrication and electromagnetic characteristics of electromagnetic wave absorbing sandwich structures  

Microsoft Academic Search

The radar absorbing structures (RAS) having sandwich structures in the X-band (8.2–12.4GHz) frequencies were designed and fabricated. We added conductive fillers such as carbon black and multi-walled carbon nanotube (MWNT) to composite prepregs and polyurethane foams so as to efficiently increase the absorbing capacity of RAS. In order to improve the mechanical stiffness of RAS, we adopted the sandwich structures

Ki-Yeon Park; Sang-Eui Lee; Chun-Gon Kim; Jae-Hung Han

2006-01-01

289

Characterization of concrete properties from dielectric properties using ground penetrating radar  

SciTech Connect

This paper presents the experimental results of a study of the relationships between light-weight (LWAC) and normal aggregate concrete (NAC) properties, as well as radar wave properties that are derived by using ground penetrating radar (GPR). The former (LWAC) refers to compressive strength, apparent porosity and saturated density, while the latter (NAC) refers to real part of dielectric permittivity ({epsilon}' or real permittivity) and wave energy level (E). Throughout the test period of the newly cast concrete cured for 90 days, the above mentioned material properties gradually changed which can be attributed to the effects of cement hydration, different types of aggregates and initial water to binder ratios. A number of plots describing various properties of concrete such as dielectric, strength and porosity perspectives were established. From these plots, we compare the characteristics of how much and how fast free water was turned to absorbed water in LWAC and NAC. The underlying mechanisms and a mechanistic model are then developed.

Lai, W.L.; Kou, S.C. [Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Tsang, W.F. [Department of Building and Real Estate, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Poon, C.S. [Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong)], E-mail: cecspoon@inet.polyu.edu.hk

2009-08-15

290

Polarization insensitive terahertz metamaterial absorber.  

PubMed

We present the simulation, implementation, and measurement of a polarization insensitive resonant metamaterial absorber in the terahertz region. The device consists of a metal/dielectric-spacer/metal structure allowing us to maximize absorption by varying the dielectric material and thickness and, hence, the effective electrical permittivity and magnetic permeability. Experimental absorption of 77% and 65% at 2.12 THz (in the operating frequency range of terahertz quantum cascade lasers) is observed for a spacer of polyimide or silicon dioxide respectively. These metamaterials are promising candidates as absorbing elements for thermally based terahertz imaging. PMID:21499411

Grant, J; Ma, Y; Saha, S; Lok, L B; Khalid, A; Cumming, D R S

2011-04-15

291

Metamaterial electromagnetic wave absorbers.  

PubMed

The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch-the metamaterial perfect absorber (MPA)-has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed. PMID:22627995

Watts, Claire M; Liu, Xianliang; Padilla, Willie J

2012-06-19

292

Radar cross section  

Microsoft Academic Search

The technological evolution in signal processing that has been made in last decades led to improvements in radar performances. Increasing the radar range by improving its sensitivity has been made by the designers of aircraft and other military systems to try to decrease the radar cross section of these types of equipment. The radar cross section is a matter of

L. Nicolaescu; Teofil Oroian

2001-01-01

293

Wind shear radar simulation  

NASA Technical Reports Server (NTRS)

Viewgraphs used in a presentation on wind shear radar simulation are given. Information on a microburst model of radar reflectivity and wind velocity, radar pulse output, the calculation of radar return, microburst power spectrum, and simulation plans are given. A question and answer session is transcribed.

Britt, Charles L.

1988-01-01

294

First radar echoes from cumulus clouds  

SciTech Connect

In attempting to use centimeter-wavelength radars to investigate the early stage of precipitation formation in clouds, 'mantle echoes' are rediscovered and shown to come mostly from scattering by small-scale variations in refractive index, a Bragg kind of scattering mechanism. This limits the usefulness of single-wavelength radar for studies of hydrometeor growth, according to data on summer cumulus clouds in North Dakota, Hawaii, and Florida, to values of reflectivity factor above about 10 dBZe with 10-cm radar, 0 dBZe with 5-cm radar, and -10 dBZe with 3-cm radar. These are limits at or above which the backscattered radar signal from the kinds of clouds observed can be assumed to be almost entirely from hydrometeors or (rarely) other particulate material such as insects. Dual-wavelength radar data can provide the desired information about hydrometeors at very low reflectivity levels if assumptions can be made about the inhomogeneities responsible for the Bragg scattering. The Bragg scattering signal itself probably will be a useful way to probe inhomogeneities one-half the radar wavelength in scale for studying cloud entrainment and mixing processes. However, this use is possible only before scattering from hydrometeors dominates the radar return. 25 refs.

Knight, C.A.; Miller, L.J. (NCAR, Boulder, CO (United States))

1993-02-01

295

First radar echoes from cumulus clouds  

NASA Technical Reports Server (NTRS)

In attempting to use centimeter-wavelength radars to investigate the early stage of precipitation formation in clouds, 'mantle echoes' are rediscovered and shown to come mostly from scattering by small-scale variations in refractive index, a Bragg kind of scattering mechanism. This limits the usefulness of single-wavelength radar for studies of hydrometeor growth, according to data on summer cumulus clouds in North Dakota, Hawaii, and Florida, to values of reflectivity factor above about 10 dBZe with 10-cm radar, 0 dBZe with 5-cm radar, and -10 dBZe with 3-cm radar. These are limits at or above which the backscattered radar signal from the kinds of clouds observed can be assumed to be almost entirely from hydrometeors or (rarely) other particulate material such as insects. Dual-wavelength radar data can provide the desired information about hydrometeors at very low reflectivity levels if assumptions can be made about the inhomogeneities responsible for the Bragg scattering. The Bragg scattering signal itself probably will be a useful way to probe inhomogeneities one-half the radar wavelength in scale for studying cloud entrainment and mixing processes. However, this use is possible only before scattering from hydrometeors dominates the radar return.

Knight, Charles A.; Miller, L. J.

1993-01-01

296

Mechanical testing of absorbable suture anchors  

Microsoft Academic Search

Purpose: Absorbable suture anchors offer great advantages but are made of mechanically weak material. The weakest link in the fixation of soft tissue to bone may therefore be the anchor itself. In this study, several commercially available anchors were mechanically tested in vitro. Type of study: Biomechanical bench study. Methods: Twelve absorbable suture anchor models were implanted into an artificial

Dominik C. Meyer; Sandro F. Fucentese; Kurt Ruffieux; Hilaire A. C. Jacob; Christian Gerber

2003-01-01

297

Perfect metamaterial absorber.  

PubMed

We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega). Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96%. Unlike conventional absorbers, our MM consists solely of metallic elements. The substrate can therefore be optimized for other parameters of interest. We experimentally demonstrate a peak A(omega) greater than 88% at 11.5 GHz. PMID:18518577

Landy, N I; Sajuyigbe, S; Mock, J J; Smith, D R; Padilla, W J

2008-05-23

298

Fibrous absorber solar collector  

SciTech Connect

A lightweight and durable solar collector employing a fibrous absorber is described. Sufficient fiber mass may be used to blanket all radiation. The absorber is disposed between a transparent cover and a heat insulating shield behind which may be a rigid collector container. A reflector disposed between the absorber and the insulation is optional. Air enters the collector passes into a duct near bottom of the absorber and across the width of the absorber, flows parallel to and through the thinnest dimension of the absorber conducting heat from the fiber at the depths of greatest absorption and then exits through a similar duct located near the top of the absorber and out of the collector.

Novinger, H.E.

1981-12-08

299

Ni0.5Zn0.5Fe2O4\\/ bamboo charcoal\\/titania LDPE composites as viable microwave absorbing materials  

Microsoft Academic Search

A combination of bamboo charcoal (BC), titania (TiO2) and Ni0.5Zn0.5Fe2O4 spinel ferrites particles were synthesized by hydrothermal method and introduced into Low Density Polyethylene (LDPE) to be a Microwave Absorber. The structural characterizations and surface morphology of Ni0.5Zn0.5Fe2O4\\/BC\\/Ti composites were investigated by X-ray diffraction (XRD) and scanning electron microscopy respectively. The complex permittivity of composites with polymer to fillers weight

J. P. Gogoi; S. Sarmah; D. Sarmah; N. S. Bhattacharyya

2009-01-01

300

Method for absorbing an ion from a fluid  

DOEpatents

A method for absorbing an ion from a fluid by using dispersing an organic acid into an anion surfactant solution, mixing in a divalent-metal containing compound and a trivalent-metal containing compound and calcining the resulting solid layered double hydroxide product to form an absorbent material and then contacting the absorbent material with an aqueous solution of cations or anions to be absorbed.

Gao, Huizhen (Carlsbad, NM); Wang, Yifeng (Albuquerque, NM); Bryan, Charles R. (Albuquerque, NM)

2007-07-03

301

Energy absorber uses expanded coiled tube  

NASA Technical Reports Server (NTRS)

Mechanical shock mitigating device, based on working material to its failure point, absorbs mechanical energy by bending or twisting tubing. It functions under axial or tangential loading, has no rebound, is area independent, and is easy and inexpensive to build.

Johnson, E. F.

1972-01-01

302

Externally tuned vibration absorber  

DOEpatents

A vibration absorber unit or units are mounted on the exterior housing of a hydraulic drive system of the type that is powered from a pressure wave generated, e.g., by a Stirling engine. The hydraulic drive system employs a piston which is hydraulically driven to oscillate in a direction perpendicular to the axis of the hydraulic drive system. The vibration absorbers each include a spring or other resilient member having one side affixed to the housing and another side to which an absorber mass is affixed. In a preferred embodiment, a pair of vibration absorbers is employed, each absorber being formed of a pair of leaf spring assemblies, between which the absorber mass is suspended.

Vincent, Ronald J. (Latham, NY)

1987-09-22

303

Methods for absorbing neutrons  

DOEpatents

A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

Guillen, Donna P. (Idaho Falls, ID); Longhurst, Glen R. (Idaho Falls, ID); Porter, Douglas L. (Idaho Falls, ID); Parry, James R. (Idaho Falls, ID)

2012-07-24

304

The Radar Image Generation (RIG) model  

NASA Technical Reports Server (NTRS)

RIG is a modeling system which creates synthetic aperture radar (SAR) and inverse SAR images from 3-D faceted data bases. RIG is based on a physical optics model and includes the effects of multiple reflections. Both conducting and dielectric surfaces can be modeled; each surface is labeled with a material code which is an index into a data base of electromagnetic properties. The inputs to the program include the radar processing parameters, the target orientation, the sensor velocity, and (for inverse SAR) the target angle rates. The current version of RIG can be run on any workstation, however, it is not a real-time model. We are considering several approaches to enable the program to generate realtime radar imagery. In addition to its image generation function, RIG can also generate radar cross-section (RCS) plots as well as range and doppler radar return profiles.

Stenger, Anthony J.

1993-01-01

305

Use of radar for nonintrusive subsurface investigations  

SciTech Connect

Finding and mapping buried hazardous waste can be a time-consuming process. However, advances in ground-penetrating radar technology are improving the means by which to detect subsurface features and related contamination. Geophysical Survey Systems, Inc. (North Salem, New Hampshire) has developed an innovative ground-penetrating radar system. The Subsurface Interface Radar (SIR{reg_sign}) system can provide real-time and continuous-profile records that indicate the location and depth of objects within subsurfaces of soil, concrete, rock, water, or other dielectric materials. The SIR{reg_sign} system allows the user to investigate subsurface conditions in a nonintrusive manner; this radar can locate underground storage tanks and buried drums, delineate landfill boundaries and burial trenches, and in some cases, the radar can identify hydrocarbon plums.

NONE

1995-07-01

306

Magneto-Radar Hidden Metal Detector  

DOEpatents

A varying magnetic field excites slight vibrations in an object and a radar sensor detects the vibrations at a harmonic of the excitation frequency. The synergy of the magnetic excitation and radar detection provides increased detection range compared to conventional magnetic metal detectors. The radar rejects background clutter by responding only to reflecting objects that are vibrating at a harmonic excitation field, thereby significantly improving detection reliability. As an exemplary arrangement, an ultra-wideband micropower impulse radar (MIR) is capable of being employed to provide superior materials penetration while providing range information. The magneto-radar may be applied to pre-screening magnetic resonance imaging (MRI) patients, landmine detection and finding hidden treasures.

McEwan, Thomas E. (Las Vegas, NV)

2005-07-05

307

Solar energy absorber panel  

Microsoft Academic Search

Disclosed is a solar energy absorber panel comprising a heat absorbing and conducting sheet and an array of fluid conduits in thermal contact with the sheet. For a given efficiency, the weight of the panel is minimized by providing a sheet thickness of between about 0.001 inch and about 0.006 inch and a conduit density of between about 3 and

Godrick

1976-01-01

308

Multispectral metamaterial absorber.  

PubMed

We present the simulation, implementation, and measurement of a multispectral metamaterial absorber (MSMMA) and show that we can realize a simple absorber structure that operates in the mid-IR and terahertz (THz) bands. By embedding an IR metamaterial absorber layer into a standard THz metamaterial absorber stack, a narrowband resonance is induced at a wavelength of 4.3 ?m. This resonance is in addition to the THz metamaterial absorption resonance at 109 ?m (2.75 THz). We demonstrate the inherent scalability and versatility of our MSMMA by describing a second device whereby the MM-induced IR absorption peak frequency is tuned by varying the IR absorber geometry. Such a MSMMA could be coupled with a suitable sensor and formed into a focal plane array, enabling multispectral imaging. PMID:24690713

Grant, J; McCrindle, I J H; Li, C; Cumming, D R S

2014-03-01

309

Radar Absorbers Based on Frequency Selective Surfaces on Perforated Substrates  

Microsoft Academic Search

A new type of metamaterials is introduced which can be fabricated by printing metal patches on inhomogeneous, periodic substrates. Such structures without periodic substrate are known as Frequency Selective Surfaces (FSS) but they are more promising for EMC shielding than common FSS structures because both the effective dielectric permittivity and loss of the substrate can be controlled. A numerical method

Arya Fallahi; Matthew Mishrikey; Christian Hafner; Rüdiger Vahldieck

310

Ultimate thickness to bandwidth ratio of radar absorbers  

Microsoft Academic Search

Analytic properties of the reflection coefficient of a multilayer metal-backed slab are considered. The result is a new form of the dispersion relationship, which characterizes the integral of the reflectance over wavelength in terms of the total thickness and averaged static permeability of the slab. The relation may be transformed to an inequality, which produces the least thickness to bandwidth

Konstantin N. Rozanov

2000-01-01

311

Radar augmentation device  

NASA Technical Reports Server (NTRS)

The radar augmentation device (RAD) serves to increase the radar response of a target body and thus expedite radar acquisition. The design and development of the RAD are discussed with particular emphasis on technical problems that were encountered and solved. Discussions of the mode of operation of the RAD and the ground test history are also included.

Riedel, J. K.

1972-01-01

312

Micropower impulse radar  

Microsoft Academic Search

Invented and developed at Lawrence Livermore National Laboratory is an inexpensive and highly sensitive, low-power radar system that produces and samples extremely short pulses of energy at the rate of 2 million per second. Called micropower impulse radar (MIR), it can detect objects at a greater variety of distances with greater sensitivity than conventional radar. Its origins in the Laboratory`s

S. Azevedo; T. E. McEwan

1996-01-01

313

Radar hydrology: rainfall estimation  

Microsoft Academic Search

Radar observations of rainfall and their use in hydrologic research provide the focus for the paper. Radar-rainfall products are crucial for input to runoff and flood prediction models, validation of satellite remote sensing algorithms, and for statistical characterization of extreme rainfall frequency. In this context we discuss the issues of radar-rainfall product development, and the theoretical and practical requirements of

W. F. Krajewski; J. A. Smith

2002-01-01

314

Validation and determination of ice water content-radar reflectivity relationships during CRYSTAL-  

E-print Network

scatter and absorb radiation is determined by the microphysical and geometric structure of the cloudValidation and determination of ice water content- radar reflectivity relationships during CRYSTAL with remote sensing data made by the Cloud Radar System instrument in order to derive and validate

315

3-D FDTD Simulations of Ground-Penetrating-Radar Scenarios Levent Grel  

E-print Network

to simulate the physical absorbers mounted inside the GPR unit, around the antenna feed structures, in order3-D FDTD Simulations of Ground-Penetrating-Radar Scenarios Levent Gürel Department of Electrical of assisting the subsequent designs of high-performance Ground- Penetrating-Radar (GPR) hardware and detection

Gürel, Levent

316

Solar sustained plasma/absorber conceptual design  

NASA Technical Reports Server (NTRS)

A space power system concept was evaluated which uses concentrated solar energy to heat a working fluid to temperatures as high as 4000 K. The high temperature working fluid could be used for efficient electric power production in advanced thermal or magnetohydrodynamic conversion cycles. Energy absorber configurations utilizing particles or cesium vapor absorber material were investigaed. Results of detailed radiant heat transfer calculations indicated approximately 86 percent of the incident solar energy could be absorbed within a 12-cm-dia flowing stream of gas borne carbon particles. Calculated total energy absorption in the cesium vapor seeded absorber configuration ranged from 34 percent to 64 percent of the incident solar energy. Solar flux concentration ratios of between approximately 3000 and 10,000 will be required to sustain absorber temperatures in the range from 3000 K to 4000 K.

Rodgers, R. J.; Krascella, N. L.; Kendall, J. S.

1979-01-01

317

Internal absorber solar collector  

DOEpatents

Thin solar collecting panels are described made from arrays of small rod collectors consisting of a refracting dielectric rod lens with an absorber imbedded within it and a reflecting mirror coated on the back side of the dielectric rod. Non-tracking collector panels on vertical walls or roof tops receive approximately 90% of solar radiation within an acceptance zone 60.degree. in elevation angle by 120.degree. or more in the azimuth sectors with a collector concentration ratio of approximately 3.0. Miniaturized construction of the circular dielectric rods with internal absorbers reduces the weight per area of glass, plastic and metal used in the collector panels. No external parts or insulation are needed as heat losses are low due to partial vacuum or low conductivity gas surrounding heated portions of the collector. The miniature internal absorbers are generally made of solid copper with black selective surface and the collected solar heat is extracted at the collector ends by thermal conductivity along the absorber rods. Heat is removed from end fittings by use of liquid circulants. Several alternate constructions are provided for simplifying collector panel fabrication and for preventing the thermal expansion and contraction of the heated absorber or circulant tubes from damaging vacuum seals. In a modified version of the internal absorber collector, oil with temperature dependent viscosity is pumped through a segmented absorber which is now composed of closely spaced insulated metal tubes. In this way the circulant is automatically diverted through heated portions of the absorber giving higher collector concentration ratios than theoretically possible for an unsegmented absorber.

Sletten, Carlyle J. (106 Nagog Hill Rd., Acton, MA 01720); Herskovitz, Sheldon B. (88 Hammond St., Acton, MA 01720); Holt, F. S. (46 Emerson Rd., Winchester, MA 01890); Sletten, E. J. (Chestnut Hill Rd. R.F.D. Rte. #4, Amherst, NH 03031)

1981-01-01

318

Cloud and Precipitation Radar  

NASA Astrophysics Data System (ADS)

Precipitation or weather radar is an essential tool for research, diagnosis, and nowcasting of precipitation events like fronts or thunderstorms. Only with weather radar is it possible to gain insights into the three-dimensional structure of thunderstorms and to investigate processes like hail formation or tornado genesis. A number of different radar products are available to analyze the structure, dynamics and microphysics of precipitation systems. Cloud radars use short wavelengths to enable detection of small ice particles or cloud droplets. Their applications differ from weather radar as they are mostly orientated vertically, where different retrieval techniques can be applied.

Hagen, Martin; Höller, Hartmut; Schmidt, Kersten

319

Lipid-absorbing Polymers  

NASA Technical Reports Server (NTRS)

The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.

Marsh, H. E., Jr.; Wallace, C. J.

1973-01-01

320

Container and method for absorbing and reducing hydrogen concentration  

DOEpatents

A method for absorbing hydrogen from an enclosed environment comprising providing a vessel; providing a hydrogen storage composition in communication with a vessel, the hydrogen storage composition further comprising a matrix defining a pore size which permits the passage of hydrogen gas while blocking the passage of gaseous poisons; placing a material within the vessel, the material evolving hydrogen gas; sealing the vessel; and absorbing the hydrogen gas released into the vessel by the hydrogen storage composition. A container for absorbing evolved hydrogen gas comprising: a vessel having an interior and adapted for receiving materials which release hydrogen gas; a hydrogen absorbing composition in communication with the interior, the composition defining a matrix surrounding a hydrogen absorber, the matrix permitting the passage of hydrogen gas while excluding gaseous poisons; wherein, when the vessel is sealed, hydrogen gas, which is released into the vessel interior, is absorbed by the hydrogen absorbing composition.

Wicks, George G. (Aiken, SC); Lee, Myung W. (North Augusta, SC); Heung, Leung K. (Aiken, SC)

2001-01-01

321

Plasmonic and Metamaterial Structures as Electromagnetic Absorbers  

E-print Network

Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrow band absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, bio-sensing, etc. In other applications such as solar energy harvesting and photonic detection, the bandwidth of light absorbers is required to be quite broad. Under such a background, a variety of mechanisms of broadband/multiband absorption have been proposed, such as mixing multiple resonances together, exciting phase resonances, slowing down light by anisotropic metamaterials, employing high loss materials and so on.

Cui, Yanxia; Jin, Yi; Ding, Fei; Yang, Liu; Ye, Yuqian; Zhong, Shoumin; Lin, Yinyue; He, Sailing

2014-01-01

322

Absorbance modulation optical lithography  

E-print Network

In this thesis, the concept of absorbance-modulation optical lithography (AMOL) is described, and the feasibility experimentally verified. AMOL is an implementation of nodal lithography, which is not bounded by the diffraction ...

Tsai, Hsin-Yu Sidney

2007-01-01

323

2. VIEW SOUTHWEST, prime search radar tower, height finder radar ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. VIEW SOUTHWEST, prime search radar tower, height finder radar towards, height finder radar towers, and radar tower (unknown function) - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

324

Study on preparation and microwave absorption property of the core-nanoshell composite materials doped with La.  

PubMed

Microwave absorbing material plays a great role in electromagnetic pollution controlling, electromagnetic interference shielding and stealth technology, etc. The core-nanoshell composite materials doped with La were prepared by a solid-state reaction method, which is applied to the electromagnetic wave absorption. The core is magnetic fly-ash hollow cenosphere, and the shell is the nanosized ferrite doped with La. The thermal decomposition process of the sample was investigated by thermogravimetry and differential thermal analysis. The morphology and components of the composite materials were investigated by the X-ray diffraction analysis, the microstructure was observed by scanning electron microscope and transmission electron microscope. The results of vibrating sample magnetometer analysis indicated that the exchange-coupling interaction happens between ferrite of magnetic fly-ash hollow cenosphere and nanosized ferrite coating, which caused outstanding magnetic properties. The microwave absorbing property of the sample was measured by reflectivity far field radar cross section of radar microwave absorbing material with vector network analyzer. The results indicated that the exchange-coupling interaction enhanced magnetic loss of composite materials. Therefore, in the frequency of 5 GHz, the reflection coefficient can achieve -24 dB. It is better than single material and is consistent with requirements of the microwave absorbing material at the low-frequency absorption. PMID:25078834

Wei, Liqiu; Che, Ruxin; Jiang, Yijun; Yu, Bing

2013-12-01

325

MIR/NIR/VIS spectrophotometric investigation of absorbing thin-film materials based on error function minimization by the method of conjugated gradients  

NASA Astrophysics Data System (ADS)

A flexible numerical procedure for the calculation of thin film optical constants from specular transmittance and reflectance data is presented. The method is based on the minimization of an error function, which may be adapted to the specifics of the optical behavior of the given sample (or set of samples), and the given wavenumber region. The flexibility in choosing an appropriate form of the error function minimized, in combination with the powerful minimization method of conjugated gradients, allowed us to investigate the optical constants of very different types of novel thin film materials with a complicated absorption behavior. In particular, the results concerning the investigation of single- and two-layer-systems based on the following optical thin film materials are presented: amorphous silicon, phthalocyanine layers, hydrogenated amorphous carbon, and as-deposited (rough) CVD diamond layers.

Stenzel, Olaf; Petrich, Ralf

1994-09-01

326

Cellulose-silver nanoparticle hybrid materials to control spoilage-related microflora in absorbent pads located in trays of fresh-cut melon  

Microsoft Academic Search

The antimicrobial activity of newly developed cellulose-silver nanoparticle hybrid materials was investigated during storage of minimally processed “Piel de Sapo” melon. Silver nanoparticles were produced after in-situ reduction by physical methods of 1% silver nitrate adsorbed on cellulose fibres; they accounted between 5 and 35nm diameter, and were not aggregated. Fresh-cut melon pieces were stored for 10days at 4°C under

Avelina Fernández; Pierre Picouet; Elsa Lloret

2010-01-01

327

Thermal oxidation properties of titanium nitride and titanium–aluminum nitride materials — A perspective for high temperature air-stable solar selective absorber applications  

Microsoft Academic Search

Air-stable high temperature solar selective surfaces have the advantages of simplifying the design, and reducing the cost of solar thermal energy conversion systems. Previous studies on the properties of titanium nitride (TiN) or titanium–aluminum nitride (TiAlN) films suggested that these materials could be a candidate for solar energy applications. In this paper, we report that oxidation occurs at 450 °C, and

Y. Yin; L. Hang; S. Zhang; X. L. Bui

2007-01-01

328

3. VIEW NORTHWEST, height finder radar towers, and radar tower ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. VIEW NORTHWEST, height finder radar towers, and radar tower (unknown function) - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

329

Study of a Planar Spiral Antenna Used in Ground Penetrating Radar System  

Microsoft Academic Search

A planar Archimedean-spiral antenna used in UHF ground penetrating radar system is studied. How to have an effect on frequency property for antenna by changing absorbing structures placed in reflecting cavity is analyzed. According to the analytical result, a new absorbing structure is designed and actual measurement is carried out. Finally, the azimuth pattern and radiation property for antenna is

Zhiwen Xiao; Jianguo He; Peiguo Liu

2008-01-01

330

Application of ICP-OES to the determination of CuIn(1-x)Ga(x)Se2 thin films used as absorber materials in solar cell devices.  

PubMed

CuIn(1-x)Ga(x)Se2 [CIGS; x=Ga/(In+Ga)] thin films are among of the best candidates as absorber materials for solar cell applications. The material quality and main properties of the polycrystalline absorber layer are critically influenced by deviations in the stoichiometry, particularly in the Cu/(In+Ga) atomic ratio. In this work a simple, sensitive and accurate method has been developed for the quantitative determination of these thin films by inductively coupled plasma optical emission spectrometry (ICP-OES). The proposed method involves an acid digestion of the samples to achieve the complete solubilization of CIGS, followed by the analytical determination by ICP-OES. A digestion procedure with 50% HNO3 alone or in the presence of 10% HCl was performed to dissolve those thin films deposited on glass or Mo-coated glass substrates, respectively. Two analytical lines were selected for each element (Cu 324.754 and 327.396 nm, Ga 294.364 and 417.206 nm, In 303.936 and 325.609 nm, Se 196.090 and 203.985 nm, and Mo 202.030 and 379.825 nm) and a study of spectral interferences was performed which showed them to be suitable, since they offered a high sensitivity and no significant inter-element interferences were detected. Detection limits for all elements at the selected lines were found to be appropriate for this kind of application, and the relative standard deviations were lower than 1.5% for all elements with the exception of Se (about 5%). The Cu/(In+Ga) atomic ratios obtained from the application of this method to CIGS thin films were consistent with the study of the structural and morphological properties by X-ray diffraction (XRD) and scanning electron microscopy (SEM). PMID:15702309

Fernández-Martínez, Rodolfo; Caballero, Raquel; Guillén, Cecilia; Gutiérrez, María Teresa; Rucandio, María Isabel

2005-05-01

331

Planetary radar studies  

NASA Technical Reports Server (NTRS)

A catalog of lunar and radar anomalies was generated to provide a base for comparison with Venusian radar signatures. The relationships between lunar radar anomalies and regolith processes were investigated, and a consortium was formed to compare lunar and Venusian radar images of craters. Time was scheduled at the Arecibo Observatory to use the 430 MHz radar to obtain high resolution radar maps of six areas of the lunar suface. Data from 1978 observations of Mare Serenitas and Plato are being analyzed on a PDP 11/70 computer to construct the computer program library necessary for the eventual reduction of the May 1981 and subsequent data acquisitions. Papers accepted for publication are presented.

Thompson, T. W.; Cutts, J. A.

1981-01-01

332

Laser radar in robotics  

SciTech Connect

In this paper the authors describe the basic operating principles of laser radar sensors and the typical algorithms used to process laser radar imagery for robotic applications. The authors review 12 laser radar sensors to illustrate the variety of systems that have been applied to robotic applications wherein information extracted from the laser radar data is used to automatically control a mechanism or process. Next, they describe selected robotic applications in seven areas: autonomous vehicle navigation, walking machine foot placement, automated service vehicles, manufacturing and inspection, automotive, military, and agriculture. They conclude with a discussion of the status of laser radar technology and suggest trends seen in the application of laser radar sensors to robotics. Many new applications are expected as the maturity level progresses and system costs are reduced.

Carmer, D.C.; Peterson, L.M. [Environmental Research Inst. of Michigan, Ann Arbor, MI (United States)

1996-02-01

333

Caribbean Radar Cases  

NSDL National Science Digital Library

This module presents radar case studies taken from events in the Caribbean that highlight radar signatures of severe weather. These cases include examples of deep convection, squall lines, bow echoes, tornadoes, and heavy rain resulting in flooding. Each case study includes a discussion of the conceptual models of each type of event as a review before showing the radar signatures and allowing the learner to analyze each one.

Comet

2013-12-31

334

Mechanical energy absorber  

NASA Technical Reports Server (NTRS)

An energy absorbing system for controlling the force where a moving object engages a stationary stop and where the system utilized telescopic tubular members, energy absorbing diaphragm elements, force regulating disc springs, and a return spring to return the telescoping member to its start position after stroking is presented. The energy absorbing system has frusto-conical diaphragm elements frictionally engaging the shaft and are opposed by a force regulating set of disc springs. In principle, this force feedback mechanism serves to keep the stroking load at a reasonable level even if the friction coefficient increases greatly. This force feedback device also serves to desensitize the singular and combined effects of manufacturing tolerances, sliding surface wear, temperature changes, dynamic effects, and lubricity.

Wesselski, Clarence J. (inventor)

1993-01-01

335

The Invisible Radar Triangle  

NSDL National Science Digital Library

Students learn about radar imaging and its various military and civilian applications that include recognition and detection of human-made targets, and the monitoring of space, deforestation and oil spills. They learn how the concepts of similarity and scaling are used in radar imaging to create three-dimensional models of various targets. Students apply the critical attributes of similar figures to create scale models of a radar imaging scenario using infrared range sensors (to emulate radar functions) and toy airplanes (to emulate targets). They use technology tools to measure angles and distances, and relate the concept of similar figures to real-world applications.

RET-ENET Program, Electrical Engineering Department,

336

Shock Absorbing System  

NASA Technical Reports Server (NTRS)

A lightweight, inexpensive shock-absorbing system, developed by Langley Research Center 20 years ago, is now in service as safety device for an automated railway at Duke University Medical Center. The transportation system travels at about 25 miles per hour, carrying patients, visitors, staff and cargo. At the end of each guideway of the system are "frangible," (breakable) tube "buffers." If a slowing car fails to make a complete stop at the terminal, it would bump and shatter the tubes, absorbing energy that might otherwise jolt the passengers or damage the vehicle.

1982-01-01

337

OSCEE fan exhaust bulk absorber treatment evaluation  

NASA Technical Reports Server (NTRS)

The acoustic suppression capability of bulk absorber material designed for use in the fan exhaust duct walls of the quiet clean short haul experiment engine (OCSEE UTW) was evaluated. The acoustic suppression to the original design for the engine fan duct which consisted of phased single degree-of-freedom wall treatment was tested with a splitter and also with the splitter removed. Peak suppression was about as predicted with the bulk absorber configuration, however, the broadband characteristics were not attained. Post test inspection revealed surface oil contamination on the bulk material which could have caused the loss in bandwidth suppression.

Bloomer, H. E.; Samanich, N. E.

1980-01-01

338

High-Resolution Synthetic Aperture Radar Observations of the Moon  

Microsoft Academic Search

Variations in radar backscatter from planetary surfaces are related to differences in the local slope and the electrical and structural properties of the top surface layer. The top few meters of the surface of the Moon consist of fine-grained unconsolidated rock material containing exposed and buried rocks. Previous Lunar radar measurements have shown a depolarized backscatter component related to the

Nicholas John Sholto Stacy

1993-01-01

339

Synthetic-aperture radar imaging through dispersive media  

Microsoft Academic Search

In this paper we develop a method for synthetic-aperture radar (SAR) imaging through a dispersive medium. We consider the case when the sensor and scatterers are embedded in a known homogeneous dispersive material, the scene to be imaged lies on a known surface and the radar antenna flight path is an arbitrary but known smooth curve. The scattering is modeled

Trond Varslot; J. Héctor Morales; Margaret Cheney

2010-01-01

340

Solar energy absorbing panel  

Microsoft Academic Search

A solar energy absorbing panel is provided which may be integrally incorporated into a conventional building structure so that it does not protrude from the normal contour of the building , and which utilizes components of the building structure as a part of the collecting apparatus to thereby minimize the cost thereof. The panel is composed of a plurality of

McArthur

1981-01-01

341

Effects of magnetite on high-frequency ground-penetrating radar Remke L. Van Dam1  

E-print Network

Effects of magnetite on high-frequency ground-penetrating radar Remke L. Van Dam1 , Jan M. H to understand the effects of magnetite for ground-penetrating radar (GPR) characterization of the shallow of ferrimagnetic material on ground-penetrating radar (GPR) signal performance. This interest has been driven

Borchers, Brian

342

Noncooperative rendezvous radar system  

NASA Technical Reports Server (NTRS)

A fire control radar system was developed, assembled, and modified. The baseline system and modified angle tracking system are described along with the performance characteristics of the baseline and modified systems. Proposed changes to provide additional techniques for radar evaluation are presented along with flight test data.

1974-01-01

343

Micropower impulse radar  

Microsoft Academic Search

Invented and developed at LLNL (Lawrence Livermore National Laboratory), this inexpensive and highly sensitive radar system produces and samples extremely short pulses of energy. This novel technology is finding dozens of new uses in Laboratory programs and in sensor devices for homes, automobiles, factories, and hospitals. We have invented and patented a fundamentally different type of compact, low-power radar system

S. Azevedo; T. E. McEwan

1997-01-01

344

Java Radar Analysis Tool  

NASA Technical Reports Server (NTRS)

Java Radar Analysis Tool (JRAT) is a computer program for analyzing two-dimensional (2D) scatter plots derived from radar returns showing pieces of the disintegrating Space Shuttle Columbia. JRAT can also be applied to similar plots representing radar returns showing aviation accidents, and to scatter plots in general. The 2D scatter plots include overhead map views and side altitude views. The superposition of points in these views makes searching difficult. JRAT enables three-dimensional (3D) viewing: by use of a mouse and keyboard, the user can rotate to any desired viewing angle. The 3D view can include overlaid trajectories and search footprints to enhance situational awareness in searching for pieces. JRAT also enables playback: time-tagged radar-return data can be displayed in time order and an animated 3D model can be moved through the scene to show the locations of the Columbia (or other vehicle) at the times of the corresponding radar events. The combination of overlays and playback enables the user to correlate a radar return with a position of the vehicle to determine whether the return is valid. JRAT can optionally filter single radar returns, enabling the user to selectively hide or highlight a desired radar return.

Zaczek, Mariusz P.

2005-01-01

345

Radar Location Equipment Development Program: Phase I  

SciTech Connect

The work described in this report represents the first phase of a planned three-phase project designed to develop a radar system for monitoring waste canisters stored in a thick layer of bedded salt at the Waste Isolation Pilot Plant near Carlsbad, New Mexico. The canisters will be contained in holes drilled into the floor of the underground waste storage facility. It is hoped that these measurements can be made to accuracies of +-5 cm and +-2/sup 0/, respectively. The initial phase of this project was primarily a feasibility study. Its principal objective was to evaluate the potential effectiveness of the radar method in the planned canister monitoring application. Its scope included an investigation of the characteristics of radar signals backscattered from waste canisters, a test of preliminary data analysis methods, an assessment of the effects of salt and bentonite (a proposed backfill material) on the propagation of the radar signals, and a review of current ground-penetrating radar technology. A laboratory experiment was performed in which radar signals were backscattered from simulated waste canisters. The radar data were recorded by a digital data acquisition system and were subsequently analyzed by three different computer-based methods to extract estimates of canister location and tilt. Each of these methods yielded results that were accurate within a few centimeters in canister location and within 1/sup 0/ in canister tilt. Measurements were also made to determine the signal propagation velocities in salt and bentonite (actually a bentonite/sand mixture) and to estimate the signal attenuation rate in the bentonite. Finally, a product survey and a literature search were made to identify available ground-penetrating radar systems and alternative antenna designs that may be particularly suitable for this unique application. 10 refs., 21 figs., 4 tabs.

Sandness, G.A.; Davis, K.C.

1985-06-01

346

Equatorial MU Radar project  

NASA Astrophysics Data System (ADS)

Research Institute for Sustainable Humanosphere, Kyoto University (RISH) has been studying the atmosphere by using radars. The first big facility was the MU (Middle and Upper atmosphere) radar installed in Shiga, Japan in 1984. This is one of the most powerful and multi-functional radar, and is successful of revealing importance of atmospheric waves for the dynamical vertical coupling processes. The next big radar was the Equatorial Atmosphere Radar (EAR) installed at Kototabang, West Sumatra, Indonesia in 2001. The EAR was operated under close collaboration with LAPAN (Indonesia National Institute for Aeronautics and Space), and conducted the long-term continuous observations of the equatorial atmosphere/ionosphere for more than 10 years. The MU radar and the EAR are both utilized for inter-university and international collaborative research program for long time. National Institute for Polar Research (NIPR) joined EISCAT Scientific Association together with Nagoya University, and developed the PANSY radar at Syowa base in Antarctica as a joint project with University of Tokyo. These are the efforts of radar study of the atmosphere/ionosphere in the polar region. Now we can find that Japan holds a global network of big atmospheric/ionospheric radars. The EAR has the limitation of lower sensitivity compared with the other big radars shown above. RISH now proposes a plan of Equatorial MU Radar (EMU) that is to establish the MU-radar class radar next to the EAR. The EMU will have an active phased array antenna with the 163m diameter and 1055 cross-element Yagis. Total output power of the EMU will be more than 500kW. The EMU can detect turbulent echoes from the mesosphere (60-80km). In the ionosphere incoherent-scatter observations of plasma density, drift, and temperature would be possible. Multi-channel receivers will realize radar-imaging observations. The EMU is one of the key facilities in the project "Study of coupling processes in the solar-terrestrial system" for Master Plan 2014 of the Science Council of Japan (SCJ). We show the EMU project and its science in the presentation.

Yamamoto, Mamoru; Hashiguchi, H.; Tsuda, Toshitaka; Yamamoto, Masayuki

347

Spaceborne weather radar  

NASA Technical Reports Server (NTRS)

The present work on the development status of spaceborne weather radar systems and services discusses radar instrument complementarities, the current forms of equations for the characterization of such aspects of weather radar performance as surface and mirror-image returns, polarimetry, and Doppler considerations, and such essential factors in spaceborne weather radar design as frequency selection, scanning modes, and the application of SAR to rain detection. Attention is then given to radar signal absorption by the various atmospheric gases, rain drop size distribution and wind velocity determinations, and the characteristics of clouds, as well as the range of available estimation methods for backscattering, single- and dual-wavelength attenuation, and polarimetric and climatological characteristics.

Meneghini, Robert; Kozu, Toshiaki

1990-01-01

348

Laser radar improvements  

NASA Astrophysics Data System (ADS)

A short history of the uses of various laser radars is presented, and appropriate applications of laser and microwave radars are discussed. CO2 laser radar, operating at 10.6 microns, is considered for use in aircraft navigation systems, fire-control systems for armored vehicle and aircraft, missile guidance, severe storm research, line-of-sight command of missiles, wind turbine site surveys, clear-air turbulence monitors for aircraft, and satellite tracking. Microwave radar is all-weather, but is subject to multipath inaccuracies, countermeasures, and angular resolution limitations, so hybrid laser microwave systems look promising for microwave target acquisition and laser tracking. Advantages and disadvantages of the use of ruby, YAG, and CO2 lasers in varying atmospheric conditions are discussed. Development of a laser radar pod for obstacle detection, Doppler navigation, automatic terrain following, hover control, weapon delivery, and precision searching is noted.

Jelalian, A. V.

1981-11-01

349

4. VIEW NORTHEAST, radar tower (unknown function), prime search radar ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. VIEW NORTHEAST, radar tower (unknown function), prime search radar tower, emergency power building, and height finder radar tower - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

350

5. VIEW EAST, height finder radar towers, radar tower (unknown ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. VIEW EAST, height finder radar towers, radar tower (unknown function), prime search radar tower, operations building, and central heating plant - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

351

Fully compact anechoic chamber using the pyramidal ferrite absorber for immunity test  

Microsoft Academic Search

A new generation of electromagnetic wave absorber, which has a pyramidal shape and 10 cm in height and excellent absorbing characteristics, was developed to satisfy the required characteristics of a fully compact anechoic chamber in the wide frequency range. The material of the new absorber is composed of a ferrite powder and polypropylene. When the new absorber was cascaded on

Kazuo Shimada; Toshikatsu Hayashi; Masamitsu Tokuda

2000-01-01

352

Perfect terahertz absorber using fishnet based metafilm  

SciTech Connect

We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials with desired values. Although the initial idea of metamaterials was to obtain a negative index medium, however, the evolution of metamaterials (MMs) offers a variety of practically applicable devices for controlling electromagnetic wave such as tunable filters, modulators, phase shifters, compact antenna, absorbers, etc. Terahertz regime, a crucial domain of the electromagnetic wave, is suffering from the scarcity of the efficient devices and might take the advantage of metamaterials. Here, we demonstrate design, fabrication, and characterization of a terahertz absorber based on a simple fishnet metallic film separated from a ground mirror plane by a dielectric spacer. Such absorbers are in particular important for bolometric terahertz detectors, high sensitivity imaging, and terahertz anechoic chambers. Recently, split-ring-resonators (SRR) have been employed for metamaterial-based absorbers at microwave and THz frequencies. The experimental demonstration reveals that such absorbers have absorptivity close to unity at resonance frequencies. However, the downside of these designs is that they all employ resonators of rather complicated shape with many fine parts and so they are not easy to fabricate and are sensitive to distortions.

Azad, Abul Kalam [Los Alamos National Laboratory; Shchegolkov, Dmitry Yu [Los Alamos National Laboratory; Chen, Houtong [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; Smirnova, E I [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory

2009-01-01

353

Development of structural materials exhibiting dielectric and magnetic loss at radio frequencies  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The reduction of radio frequency (RF) return from military assets has been of critical interest for the last twenty years. New materials are required that not only provide a reduction in specular and travelling wave RF energy, but also function mechanically in primary structural applications. Typical radar attenuating material (RAM) is structurally parasitic and its utilization decreases the vehicle range by adding significant weight. New conducting and semiconducting polymers have demonstrated potential for RF absorption and can be incorporated into newly developed isotropic structural foams developed from laser target technology at LANL to absorb RF energy. Successful implementation of this technology will lead to broad-band absorbers, light-weight absorbers and radar-absorbing structures (RAS) that can be applied to existing aircraft or integrated into new designs. These new materials also show a high potential to be developed into {open_quotes}smart{close_quotes} structures, i.e., structures that adapt to the threat environment and optimize their absorption.

Duke, J.R. Jr.; Apen, P.G.; Hoisington, M.

1996-10-01

354

Miniature radar packaging  

NASA Astrophysics Data System (ADS)

Several concepts of interconnections between coaxial cables and RF HMCs were evaluated resulting in two approaches that function well electrically and mechanically and that are easily processed. Methods of attaching various configurations of large ceramic substrates into assemblies were investigated, yielding a better understanding of why breakage occurs, and to find ways to reduce the occurrence of breakage. An evaluation of several materials for use as gaskets to shield against RF interference between RF circuit compartments resulted in two suitable possibilities. Resistive film and microwave absorber liners were evaluated on the inside of RF circuit compartment covers, with favorable results obtained from one that reduced the effect of the lid proximity on the circuit performance.

Andrews, G. W.

1985-06-01

355

Ionized Absorbers in AGN  

NASA Technical Reports Server (NTRS)

As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".

Mathur, S.

1999-01-01

356

Spaceborne meteorological radar studies  

NASA Technical Reports Server (NTRS)

Various radar designs and methods are studied for the estimation of rainfall parameters from space. An immediate goal is to support the development of the spaceborne radar that has been proposed for the Tropical Rain Measuring Mission (TRMM). The effort is divided into two activities: a cooperative airborne rain measuring experiment with the Radio Research Laboratory of Japan (RRL), and the modelling of spaceborne weather radars. An airborne rain measuring experiment was conducted at Wallops Flight Facility in 1985 to 1986 using the dual-wavelength radar/radiometer developed by RRL. The data are presently being used to test a number of methods that are relevant to spaceborne weather radars. An example is shown of path-averaged rain rates as estimated from three methods: the standard reflectivity rain rate method (Z-R), a dual-wavelength method, and a surface reference method. The results from the experiment shows for the first time the feasibility of using attenuation methods from space. The purposes of the modelling are twofold: to understand in a quantitative manner the relationships between a particular radar design and its capability for estimating precipitation parameters and to help devise and test new methods. The models are being used to study the impact of various TRMM radar designs on the accuracy of rain rate estimation as well as to test the performance of range-profiling algorithms, the mirror-image method, and some recently devised graphical methods for the estimation of the drop size distribution.

Meneghini, R.

1988-01-01

357

Planetary Radar Astronomy  

NASA Technical Reports Server (NTRS)

Radar is a powerful technique that has furnished otherwise unavailable information about solar system bodies for three decades. The advantages of radar in planetary astronomy result from: (1) the observer's control of all the attributes of the coherent signal used to illuminate the target, especially the wave form's time/frequency modulation and polarization; (2) the ability of radar to resolve objects spatially via measurements of the distribution of echo power in time delay and Doppler frequency; (3) the pronounced degree to which delay-Doppler measurements constrain orbits and spin vectors; and (4) centimeter-to-meter wavelengths, which easily penetrate optically opaque planetary clouds and cometary comae, permit investigation of near-surface macrostructure and bulk density, and are sensitive to high concentrations of metal or, in certain situations, ice. Planetary radar astronomy has primarily involved observations with Earth-based radar telescopes, but also includes some experiments with a spaceborne transmitter or receiver. In addition to providing a wealth of information about the geological and dynamical properties of asteroids, comets, the inner planets, and natural satellites, radar experiments have established the scale of the solar system, have contributed significantly to the accuracy of planetary ephemerides, and have helped to constrain theories of gravitation. This review outlines radar astronomical techniques and describes principal observational results.

Ostro, Steven J.

1993-01-01

358

Perfect terahertz absorber using fishnet based metafilm  

Microsoft Academic Search

We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials

Abul Kalam Azad; Dmitry Yu Shchegolkov; Houtong Chen; Antoinette Taylor; E I Smirnova; John F O Hara

2009-01-01

359

Anisotropic Layered Absorbers on Cylindrical Structures  

Microsoft Academic Search

A curved structure consisting of an imperfectly conducting circular cylinder coated by any number of coaxial thin anisotropic layers separated by isotroplc regions of different materials is considered. Each thin anisotroplc layer is represented by a sheet with an anisotropic Jump Impedance. Thus, the structure is a generalization to the anisotropic case of Jaumann absorbers on curved surfaces. For a

R. D. Graglia; P. L. E. Uslenghi

1987-01-01

360

Composition for absorbing hydrogen from gas mixtures  

DOEpatents

A hydrogen storage composition is provided which defines a physical sol-gel matrix having an average pore size of less than 3.5 angstroms which effectively excludes gaseous metal hydride poisons while permitting hydrogen gas to enter. The composition is useful for separating hydrogen gas from diverse gas streams which may have contaminants that would otherwise render the hydrogen absorbing material inactive.

Heung, Leung K. (Aiken, SC); Wicks, George G. (Aiken, SC); Lee, Myung W. (Aiken, SC)

1999-01-01

361

Space object observation with radar  

NASA Astrophysics Data System (ADS)

FGAN developed a High Power Radar System, able to track and image low Earth orbiting objects, for experimental radar research. The system is unique in Germany; it consists of a narrow band tracking radar and a high resolution imaging radar. The radars are supported from one 34-m parabolic dish antenna. They operate simultaneously on the object of interest. All information which a radar can gain about physical characteristics of targets have to be extracted from the backscattered electromagnetic field of transmitted pulses. L-band tracking data provide information on range, range rate, angular direction, and radar cross-section. From high resolution polarimetric Ku-band radar data projections of the 1- and 2-dimensional scatter centre distributions are computed. This paper gives a brief description of the FGAN radar and summarizes some radar based methods for orbit analysis, orbital lifetime prediction, reconstruction of object images, assessment of object dimensions, shape, attitude, and mass.

Mehrholz, D.

1993-08-01

362

Radar applications overview  

NASA Astrophysics Data System (ADS)

During the fifty years since its initial development as a means of providing early warning of airborne attacks against allied countries during World War II, radar systems have developed to the point of being highly mobile and versatile systems capable of supporting a wide variety of remote sensing applications. Instead of being tied to stationary land-based sites, radar systems have found their way into highly mobile land vehicles as well as into aircraft, missiles, and ships of all sizes. Of all these applications, however, the most exciting revolution has occurred in the airborne platform arena where advanced technology radars can be found in all shapes and sizes...ranging from the large AWACS and Joint STARS long range surveillance and targeting systems to small millimeter wave multi-spectral sensors on smart weapons that can detect and identify their targets through the use of highly sophisticated digital signal processing hardware and software. This paper presents an overview of these radar applications with the emphasis on modern airborne sensors that span the RF spectrum. It will identify and describe the factors that influence the parameters of low frequency and ultra wide band radars designed to penetrate ground and dense foliage environments and locate within them buried mines, enemy armor, and other concealed or camouflaged weapons of war. It will similarly examine the factors that lead to the development of airborne radar systems that support long range extended endurance airborne surveillance platforms designed to detect and precision-located both small high speed airborne threats as well as highly mobile time critical moving and stationary surface vehicles. The mission needs and associated radar design impacts will be contrasted with those of radar systems designed for high maneuverability rapid acquisition tactical strike warfare platforms, and shorter range cued air-to-surface weapons with integral smart radar sensors.

Greenspan, Marshall

1996-06-01

363

Durability of Polymeric Glazing and Absorber Materials  

Microsoft Academic Search

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes.

G. J. Jorgensen; K. M. Terwilliger; C. E. Bingham; M. Milbourne

2005-01-01

364

Electrochemical Corrosion Testing of Neutron Absorber Materials  

SciTech Connect

This report summarizes the results of crevice-corrosion tests for six alloys in solutions representative of ionic compositions inside the Yucca Mountain waste package should a breech occur. The alloys in these tests are Neutronit A978a (ingot metallurgy, hot rolled), Neutrosorb Plus 304B4 Grade Ab (powder metallurgy, hot rolled), Neutrosorb Plus 304B5 Grade Ab (powder metallurgy, hot rolled), Neutrosorb Plus 304B6 Grade Ab (powder metallurgy, hot rolled), Ni-Cr-Mo-Gd alloy2 (ingot metallurgy, hot rolled), and Alloy 22 (ingot metallurgy, hot rolled).

Tedd Lister; Ron Mizia; Arnold Erickson; Tammy Trowbridge

2007-05-01

365

A history of laser radar in the United States  

NASA Astrophysics Data System (ADS)

This paper relates a short history of laser radar development in the United States. It starts in the 60's, shortly after the invention of the laser. Initially laser radars used various lasers, until CO2 became the popular choice for coherent laser radar and NdYag for laser range finders and designators. CO2 reigned as the coherent laser radar of choice from the early 70's until the 80's or 90's. Most CO2 laser radars were at a wavelength of 10.6 ?m, although to avoid atmospheric CO2 absorption some CO2 laser radars used different isotopes of CO2 to avoid 10.6 ?m operation. The exception to the early laser radar development being CO2 were laser designators, which can be considered a form of bi-static laser radar, and laser range finders. NdYag, at 1.064 ?m wavelength, was the laser of choice for laser designators and range finders. Laser designators started in the late 60's. In the 80's to 90's solid state lasers came more into their own for laser radar application, including coherent solid state laser radars. The main development was the ability to eliminate heat from solid state material, thus allowing higher power operation. Laser diodes also became prominent, allowing a reliable and efficient method of pumping. Wind sensing, navigation, terrain following, 2D, and 3D imaging, and velocity detection are some of the other laser radar uses that have been pursued. CO2 based navigation laser radar was deployed, but with the advent of GPS has become less popular.

McManamon, Paul F.; Kamerman, Gary; Huffaker, Milton

2010-04-01

366

Holographic surveillance radar  

NASA Astrophysics Data System (ADS)

Since the 1940s, radar development has focused on narrow-beam, scanning sensors. A wide field of view has advantages in terms of extended acquisition time for any target, and when combined with a high Doppler sampling frequency can yield high-resolution Doppler spectra. Unambiguous range and Doppler can be achieved under certain circumstances, resulting in enhanced ability to evaluate the characteristics of targets and clutter. Holographic radar has a range of applications in which the ability to discriminate targets among clutter is key. An example of such an application is in mitigation of wind farm interference with Air Traffic Control radar.

Oswald, Gordon K. A.

2009-05-01

367

Micropower impulse radar  

SciTech Connect

Invented and developed at Lawrence Livermore National Laboratory is an inexpensive and highly sensitive, low-power radar system that produces and samples extremely short pulses of energy at the rate of 2 million per second. Called micropower impulse radar (MIR), it can detect objects at a greater variety of distances with greater sensitivity than conventional radar. Its origins in the Laboratory`s Laser Directorate stem from Nova`s transient digitizer. The MIR`s extraordinary range of applications include security, search and rescue, life support, nondestructive evaluation, and transportation.

Azevedo, S.; McEwan, T.E.

1996-01-01

368

Design optimization of nanostrip metamaterial perfect absorbers  

NASA Astrophysics Data System (ADS)

Metamaterial perfect absorber (MPA) promises many applications due to its capability of complete suppression of transmission or/and reflection. The complete dissipation of the incident electromagnetic energy by the absorptive meta-atoms makes it a unique candidate in many photonic and optoelectronic devices. An ultrathin metamaterial absorber that consists of a periodic nanostrip metal on top of a planar dielectric slab backed by a conducting metal plate is presented. The spectral absorptivity of MPA is investigated by the finite difference time domain method from visible to near-infrared. The various geometrical and material parameters of MPA are optimized for maximum absorption.

El-Aasser, Mostafa A.

2014-01-01

369

FREQUENCY DEPENDENT ATTENUATION ANALYSIS OF GROUND-PENETRATING RADAR DATA  

E-print Network

FREQUENCY DEPENDENT ATTENUATION ANALYSIS OF GROUND- PENETRATING RADAR DATA John H. Bradford, CGISS, Boise State University, Boise, ID Abstract I investigate the frequency dependence of attenuation materials attenuation is approximately linear with frequency over the bandwidth of the GPR signal

Barrash, Warren

370

Sensor-Friendly Freeways: Investigation of Progressive Roadway Changes to Facilitate Deployment of AHS  

E-print Network

life-cycle cost radar absorbing materials to suppress high1. In making Radar Absorbing Materials (RAM) highly magneticmaterial that meets current reflectivity requirements and can incorporate a radar absorbing

Misener, James A.; Griffiths, Paul; Johnson, Lee; Segal, Andy

2001-01-01

371

Cassini radar : system concept and simulation results  

NASA Astrophysics Data System (ADS)

The Cassini mission is an international venture, involving NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI), for the investigation of the Saturn system and, in particular, Titan. The Cassini radar will be able to see through Titan's thick, optically opaque atmosphere, allowing us to better understand the composition and the morphology of its surface, but the interpretation of the results, due to the complex interplay of many different factors determining the radar echo, will not be possible without an extensive modellization of the radar system functioning and of the surface reflectivity. In this paper, a simulator of the multimode Cassini radar will be described, after a brief review of our current knowledge of Titan and a discussion of the contribution of the Cassini radar in answering to currently open questions. Finally, the results of the simulator will be discussed. The simulator has been implemented on a RISC 6000 computer by considering only the active modes of operation, that is altimeter and synthetic aperture radar. In the instrument simulation, strict reference has been made to the present planned sequence of observations and to the radar settings, including burst and single pulse duration, pulse bandwidth, pulse repetition frequency and all other parameters which may be changed, and possibly optimized, according to the operative mode. The observed surfaces are simulated by a facet model, allowing the generation of surfaces with Gaussian or non-Gaussian roughness statistic, together with the possibility of assigning to the surface an average behaviour which can represent, for instance, a flat surface or a crater. The results of the simulation will be discussed, in order to check the analytical evaluations of the models of the average received echoes and of the attainable performances. In conclusion, the simulation results should allow the validation of the theoretical evaluations of the capabilities of microwave instruments, when considering topics like the surface topography, stratigraphy and identification of different materials.

Melacci, P. T.; Orosei, R.; Picardi, G.; Seu, R.

1998-10-01

372

Caribbean Radar Products  

NSDL National Science Digital Library

This module provides examples of radar imagery from various locations in the Caribbean to demonstrate the different types of images available. Also, examples of different meteorological and non meteorological features are presented to show features seen in island locations.

Comet

2013-12-31

373

Radar Calibration Test Satellite  

Microsoft Academic Search

A satellite has been designed for application to radar calibration. Electromagnetic and mechanical characteristics of the satellite and their influence on the selection of shape and other parameters are discussed. Theoretical and experimental scattering data are included.

L. J. Kaplan; J. F. A. Ormsby; EVERT N. FOWLE; KENT R. JOHNSON; Richard T. Bates; S. H. Bickel

1969-01-01

374

Laser Radar Animation  

NASA Video Gallery

Laser and radar instruments aboard NASA aircraft provide measurements of the snow and ice surface and down to the bedrock under the ice. Lasers, with a shorter wavelength, measure the surface eleva...

375

Underwater acoustic omnidirectional absorber  

NASA Astrophysics Data System (ADS)

Gradient index media, which are designed by varying local element properties in given geometry, have been utilized to manipulate acoustic waves for a variety of devices. This study presents a cylindrical, two-dimensional acoustic "black hole" design that functions as an omnidirectional absorber for underwater applications. The design features a metamaterial shell that focuses acoustic energy into the shell's core. Multiple scattering theory was used to design layers of rubber cylinders with varying filling fractions to produce a linearly graded sound speed profile through the structure. Measured pressure intensity agreed with predicted results over a range of frequencies within the homogenization limit.

Naify, Christina J.; Martin, Theodore P.; Layman, Christopher N.; Nicholas, Michael; Thangawng, Abel L.; Calvo, David C.; Orris, Gregory J.

2014-02-01

376

The Comet Radar Explorer Mission  

NASA Astrophysics Data System (ADS)

Missions to cometary nuclei have revealed major geological surprises: (1) Global scale layers – do these persist through to the interior? Are they a record of primary accretion? (2) Smooth regions – are they landslides originating on the surface? Are they cryovolcanic? (3) Pits – are they impact craters or sublimation pits, or rooted in the interior? Unambiguous answers to these and other questions can be obtained by high definition 3D radar reflection imaging (RRI) of internal structure. RRI can answer many of the great unknowns in planetary science: How do primitive bodies accrete? Are cometary nuclei mostly ice? What drives their spectacular activity and evolution? The Comet Radar Explorer (CORE) mission will image the detailed internal structure of the nucleus of 10P/Tempel 2. This ~16 x 8 x 7 km Jupiter Family Comet (JFC), or its parent body, originated in the outer planets region possibly millions of years before planet formation. CORE arrives post-perihelion and observes the comet’s waning activity from safe distance. Once the nucleus is largely dormant, the spacecraft enters a ~20-km dedicated Radar Mapping Orbit (RMO). The exacting design of the RRI experiment and the precise navigation of RMO will achieve a highly focused 3D radar reflection image of internal structure, to tens of meters resolution, and tomographic images of velocity and attenuation to hundreds of meters resolution, tied to the gravity model and shape. Visible imagers will produce maps of the surface morphology, albedo, color, texture, and photometric response, and images for navigation and shape determination. The cameras will also monitor the structure and dynamics of the coma, and its dusty jets, allowing their correlation in 3D with deep interior structures and surface features. Repeated global high-resolution thermal images will probe the near-surface layers heated by the Sun. Derived maps of thermal inertia will be correlated with the radar boundary response, and photometry and texture, probing surface materials attainable by future robotic excavation missions. Thermal images will reveal areas of sublimation cooling around vents and pits, and the secular response of the outer meters as the nucleus moves farther from the Sun.

Asphaug, Erik; Belton, Mike; Bockelee-Morvan, Dominique; Chesley, Steve; Delbo, Marco; Farnham, Tony; Gim, Yonggyu; Grimm, Robert; Herique, Alain; Kofman, Wlodek; Oberst, Juergen; Orosei, Roberto; Piqueux, Sylvain; Plaut, Jeff; Robinson, Mark; Sava, Paul; Heggy, Essam; Kurth, William; Scheeres, Dan; Denevi, Brett; Turtle, Elizabeth; Weissman, Paul

2014-11-01

377

Phased-array radars  

NASA Astrophysics Data System (ADS)

The operating principles, technology, and applications of phased-array radars are reviewed and illustrated with diagrams and photographs. Consideration is given to the antenna elements, circuitry for time delays, phase shifters, pulse coding and compression, and hybrid radars combining phased arrays with lenses to alter the beam characteristics. The capabilities and typical hardware of phased arrays are shown using the US military systems COBRA DANE and PAVE PAWS as examples.

Brookner, E.

1985-02-01

378

Downhole pulse radar  

DOEpatents

A borehole logging tool generates a fast rise-time, short duration, high peak-power radar pulse having broad energy distribution between 30 MHz and 300 MHz through a directional transmitting and receiving antennas having barium titanate in the electromagnetically active region to reduce the wavelength to within an order of magnitude of the diameter of the antenna. Radar returns from geological discontinuities are sampled for transmission uphole. 7 figs.

Chang, Hsi-Tien

1987-09-28

379

Downhole pulse radar  

DOEpatents

A borehole logging tool generates a fast rise-time, short duration, high peak-power radar pulse having broad energy distribution between 30 MHz and 300 MHz through a directional transmitting and receiving antennas having barium titanate in the electromagnetically active region to reduce the wavelength to within an order of magnitude of the diameter of the antenna. Radar returns from geological discontinuities are sampled for transmission uphole.

Chang, Hsi-Tien (Albuquerque, NM)

1989-01-01

380

Dielectric properties of a novel high absorbing onion-like-carbon based polymer composite  

E-print Network

Dielectric properties of a novel high absorbing onion-like-carbon based polymer composite J resonance devices, for targeting radars and vehicle speed detection, for intelligent transportation systems properties and unique electronic structure [12], being incorporated into the polymer matrix, demonstrate

Mayer, Alexandre

381

On wave radar measurement  

NASA Astrophysics Data System (ADS)

The SAAB REX WaveRadar sensor is widely used for platform-based wave measurement systems by the offshore oil and gas industry. It offers in situ surface elevation wave measurements at relatively low operational costs. Furthermore, there is adequate flexibility in sampling rates, allowing in principle sampling frequencies from 1 to 10 Hz, but with an angular microwave beam width of 10° and an implied ocean surface footprint in the order of metres, significant limitations on the spatial and temporal resolution might be expected. Indeed there are reports that the accuracy of the measurements from wave radars may not be as good as expected. We review the functionality of a WaveRadar using numerical simulations to better understand how WaveRadar estimates compare with known surface elevations. In addition, we review recent field measurements made with a WaveRadar set at the maximum sampling frequency, in the light of the expected functionality and the numerical simulations, and we include inter-comparisons between SAAB radars and buoy measurements for locations in the North Sea.

Ewans, Kevin; Feld, Graham; Jonathan, Philip

2014-09-01

382

Metamaterial absorber with wide angular and frequency bandwidth  

Microsoft Academic Search

The absorbers usually employed in everyday applications and the ultimate layouts recently proposed in the literature and based on unconventional material loading, are usually backed by a metallic plate. The metallic backing plays two main roles. On one hand, it is used to avoid power transmission on the other side of the absorber. On the other hand, it enables a

Alessandro Toscano; Lucio Vegni

2009-01-01

383

Comparison of two-dimensional periodic and finite absorber structures  

Microsoft Academic Search

The study of absorber structures and shielding screens remains an important topic in EMC. A general two-dimensional boundary integral equation (BIE) technique has been implemented to handle both finite and periodic absorber structures. The generality of the method is twofold: the geometry of the structure may be chosen arbitrary finite or one-dimensional periodic, and the materials being used are uniaxial

B. Baekelandt; F. Olyslager; D. De Zutter

1995-01-01

384

Metamaterial saturable absorber mirror.  

PubMed

We propose a metamaterial saturable absorber mirror at midinfrared wavelengths that can show a saturation of absorption with intensity of incident light and switch to a reflecting state. The design consists of an array of circular metallic disks separated by a thin film of vanadium dioxide (VO(2)) from a continuous metallic film. The heating due to the absorption in the absorptive state causes the VO(2) to transit to a metallic phase from the low temperature insulating phase. The metamaterial switches from an absorptive state (R?0.1%) to a reflective state (R>95%) for a specific threshold intensity of the incident radiation corresponding to the phase transition of VO(2), resulting in the saturation of absorption in the metamaterial. The computer simulations show over 99.9% peak absorbance, a resonant bandwidth of about 0.8 ?m at 10.22 ?m wavelengths, and saturation intensity of 140 mW cm(-2) for undoped VO(2) at room temperature. We also carried out numerical simulations to investigate the effects of localized heating and temperature distribution by solving the heat diffusion problem. PMID:23381408

Dayal, Govind; Ramakrishna, S Anantha

2013-02-01

385

Technical evaluation of Russian aircraft stealth coating and structural materials  

SciTech Connect

Treating aircraft, missiles, and ships with materials that absorb electromagnetic energy continues to be an important technique for reducing a vehicle`s radar cross section (RCS) and improving tis combat effectiveness and survivability. Work at the Russian Scientific Center for Applied Problems in Electrodynamics (SCAPE) has produced and experimentally validated an accurate predictor of the interaction of electromagnetic radiation with discontinuous composite materials consisting of magnetic and/or dielectric particles dispersed in a non-conductive matrix (i.e. percolation systems). The primary purpose of this project was to analyze rf-absorbing coatings and validate manufacturing processes associated with the Russian percolation system designs. An additional objective was to apply the percolation methodology toward a variety of civilian applications by transferring the technology to US industry.

Gac, F.D.; Young, A.T. Jr.; Migliori, A.

1996-10-01

386

Sensing with THz metamaterial absorbers  

E-print Network

Metamaterial perfect absorbers from microwaves to optical part of the electromagnetic spectrum has been intensely studied for its ability to absorb electromagnetic radiation. Perfect absorption of light by metamaterials have opened up new opportunities for application oriented functionalities such as efficient sensors and emitters. We present an absorber based sensing scheme at the terahertz frequencies and discuss optimized designs to achieve high frequency and amplitude sensitivities. The major advantage of a perfect metamaterial absorber as a sensor is the sensitive shift in the absorber resonance frequency along with the sharp change in the amplitude of the resonance due to strong interaction of the analyte with the electric and the magnetic fields at resonant perfect absorption frequency. We compare the sensing performance of the perfect metamaterial absorber with its complementary structural design and planar metasurface with identical structure. The best FoM values obtained for the absorber sensor here...

Cong, Longqing

2014-01-01

387

Coherent backscatter and the radar characteristics of outer planet satellites  

Microsoft Academic Search

It is presently suggested that the diffuse component-dominated high radar reflectivities and large polarization of Europa, Ganymede, and Callisto could be due to the illumination by a collimated source of a weakly absorbing particulate medium in which wavelength-scaled scatterers are separated by distances somewhat larger than the wavelength. A plausible medium could be a regolith composed of voids and\\/or silicate

Bruce Hapke

1990-01-01

388

Microwave emissions from police radar  

E-print Network

The purpose of this study was to evaluate police officers exposures to microwaves emitted by traffic radar units at the ocular and testicular level. Additionally, comparisons were made of the radar manufacturers published maximum power density...

Fink, John Michael

2012-06-07

389

Venus wind-altitude radar  

NASA Technical Reports Server (NTRS)

A design study on adding a radar altimeter to the Pioneer Venus small probe is review. Block and timing diagrams are provided. The inherent and interface ambiguities, resolution, and data handling logic for radar altimeters are described.

Levanon, N.

1974-01-01

390

Phase modulating the Urbana radar  

NASA Technical Reports Server (NTRS)

The design and operation of a switched phase modulation system for the Urbana Radar System are discussed. The system is implemented and demonstrated using a simple procedure. The radar system and circuits are described and analyzed.

Herrington, L. J., Jr.; Bowhill, S. A.

1983-01-01

391

Special applications of radar systems  

Microsoft Academic Search

Developments at Dornier in radar equipment are discussed. Characteristics of the Tasyll-1 scoring system for air target simulation are examined with emphasis on the Doppler radar principle for missile location. The RADOBS-R (Radar-object shield panorama sensor) system creates a ring-shaped alarm zone around an object for protection and has an operating frequency around 14 GHz. A Synthetic Aperture Radar and

U. Knepper; R. Kremer; H. Lamprecht; R. Schotter

1980-01-01

392

Radar data smoothing filter study  

NASA Technical Reports Server (NTRS)

The accuracy of the current Wallops Flight Facility (WFF) data smoothing techniques for a variety of radars and payloads is examined. Alternative data reduction techniques are given and recommendations are made for improving radar data processing at WFF. A data adaptive algorithm, based on Kalman filtering and smoothing techniques, is also developed for estimating payload trajectories above the atmosphere from noisy time varying radar data. This algorithm is tested and verified using radar tracking data from WFF.

White, J. V.

1984-01-01

393

Characteristics of Sunset radar  

NASA Technical Reports Server (NTRS)

Located in a narrow canyon 15 km west of Boulder, Colorado, the Sunset pulsed Doppler radar was the first radar designed and constructed specifically as a VHF ST radar. The antenna system is a phased array of coaxial-colinear dopoles with computer-controlled phase shifters for each line of dipoles. It operates at a frequency of 40.475 MHz and a wavelength of 7.41M. Peak transmitter power is 100 kW. Aperture efficiency is 0.58 and resistive loss is 0.30 for its 3600 sq m area. The practical steering rate is 1 record/minute/position to any arbitrary antenna beam position. The first clear-air turbulence echoes and wind velocity measurements were obtained in 1974. Significant accomplishments are listed.

Green, J. L.

1983-01-01

394

Radar sector blanker  

NASA Astrophysics Data System (ADS)

A radar sector blanker comprises in analog-to-digital converter and a sector controller unit. The analog-to-digital converter receives the analog synchro voltages describing the positioning of a radar antenna and changes these voltages into binary-coded decimal (BCD) information. The sector controller unit comprises a portable housing, a controller system, and a power supply. The controller system includes an OFF comparator circuit, an ON comparator circuit, an S-R latch, and a solid-state switch. Each comparator circuit comprises three cascaded transistor-transistor logic (TTL) integrated chips. The power supply gives a direct-current voltage to the solid-state switch and the TTL chips. The sector blanker blocks transmission for a predetermined rotational region or sector of a radar system.

Hall, Roger B.

1994-03-01

395

Wedge absorber design and simulation for MICE Step IV  

SciTech Connect

In the Muon Ionization Cooling Experiment (MICE), muons are cooled by passing through material, then through RF cavities to compensate for the energy loss; which reduces the transverse emittance. It is planned to demonstrate longitudinal emittance reduction via emittance exchange in MICE by using a solid wedge absorber in Step IV. Based on the outcome of previous studies, the shape and material of the wedge were chosen. We address here further simulation efforts for the absorber of choice as well as engineering considerations in connection with the absorber support design.

Rogers, C.T.; /Rutherford; Snopok, P.; /IIT, Chicago /Fermilab; Coney, L.; Hanson, G.; /UC, Riverside

2011-03-01

396

HDPE/MWCNT composite as microwave absorber  

NASA Astrophysics Data System (ADS)

A HDPE/CNT composite has been fabricated based on a commercial polyethylene loaded with a high concentration of CVD grown multiwalled carbon nanotubes with a high aspect ratio. Exploiting the resulting high conductivity of this composite material, we tested the possibility to use it as absorber of electromagnetic waves at microwave frequencies up to 25 GHz. For this purpose the device under test was placed as substrate of a microstrip transmission line. Measurements of the scattering parameters, done with a vectorial network analyzer, have been used in order to obtain the power absorption at different frequencies. Special attention was paid to the optimization of the microstrip geometry. A comparison of the microwave power absorption spectrum with those of commercial cavity absorbers showed encouraging results, regarding the microwave absorption capability of the HDPE/CNT composite material.

Di Giacomo, R.; Neitzert, H. C.

2014-05-01

397

Side looking radar calibration study  

NASA Technical Reports Server (NTRS)

Calibration of an airborne sidelooking radar is accomplished by the use of a model that relates the radar parameters to the physical mapping situation. Topics discussed include: characteristics of the transmitters; the antennas; target absorption and reradiation; the receiver and map making or radar data processing; and the calibration process.

Edwards, W. D.

1975-01-01

398

HF radar ionospheric clutter  

NASA Astrophysics Data System (ADS)

The characteristics of HF radar echoes reflected from ionization irregularities aligned along the lines of force of the Earth's magnetic field are presented. Utilizing experimental radar-ionospheric clutter data acquired at frequencies between HF and UHF, an analysis is made of the amplitude, the cross-sectional area and the angular extent statistics of HF field-aligned echoes. The Doppler frequency variation, the frequency of occurrence and the diurnal and seasonal variation of HF ionospheric backscatter echoes and their correlation with solar-geophysical conditions are also discussed.

Millman, G. H.

1982-08-01

399

Polarization diversity in radars  

NASA Astrophysics Data System (ADS)

Many polarization techniques, which have been proposed and analyzed to enhance radar performance, are reviewed in this paper in order to assess the possible improvement they can provide in the signal-to-disturbance ratio, target detectability, target discrimination and resolution, and target classification and identification. Some recent experimentally-based results relating to these applications are also presented. Those techniques are emphasized for which polarization-based capabilities appear sufficiently assessed, such as adaptive polarization cancellation of clutter, chaff, and jamming. Polarization Doppler processing of dual-polarization radar signals, meteorologic applications, and polarization adaptation for target detection in the clear (in free space) are also examined.

Giuli, D.

1986-02-01

400

Spaceborne Imaging Radar Symposium  

NASA Technical Reports Server (NTRS)

An overview of the present state of the art in the different scientific and technological fields related to spaceborne imaging radars was presented. The data acquired with the SEASAT SAR (1978) and Shuttle Imaging Radar, SIR-A (1981) clearly demonstrated the important emphasis in the 80's is going to be on in-depth research investigations conducted with the more flexible and sophisticated SIR series instruments and on long term monitoring of geophysical phenomena conducted from free-flying platforms such as ERS-1 and RADARSAT.

Elachi, C.

1983-01-01

401

Space Radar Image of Raco Biomass Map  

NASA Technical Reports Server (NTRS)

This biomass map of the Raco, Michigan, area was produced from data acquired by the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard space shuttle Endeavour. Biomass is the amount of plant material on an area of Earth's surface. Radar can directly sense the quantity and organizational structure of the woody biomass in the forest. Science team members at the University of Michigan used the radar data to estimate the standing biomass for this Raco site in the Upper Peninsula of Michigan. Detailed surveys of 70 forest stands will be used to assess the accuracy of these techniques. The seasonal growth of terrestrial plants, and forests in particular, leads to the temporary storage of large amounts of carbon, which could directly affect changes in global climate. In order to accurately predict future global change, scientists need detailed information about current distribution of vegetation types and the amount of biomass present around the globe. Optical techniques to determine net biomass are frustrated by chronic cloud-cover. Imaging radar can penetrate through cloud-cover with negligible signal losses. Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v. (DLR), the major partner in science, operations and data processing of X-SAR.

1999-01-01

402

Space Radar Image of Rocky Mountains, Montana  

NASA Technical Reports Server (NTRS)

This is a three-dimensional perspective of the eastern front range of the Rocky Mountains, about 120 kilometers (75 miles) west of Great Falls, Montana. The image was created by combining two spaceborne radar images using a technique known as interferometry. Visualizations like this are useful to scientists because they show the shapes of the topographic features such as mountains and valleys. This technique helps to clarify the relationships of the different types of materials on the surface detected by the radar. The view is looking south-southeast. Along the right edge of the image is the valley of the north fork of the Sun River. The western edge of the Great Plains appears on the left side. The valleys in the lower center, running off into the plains on the left, are branches of the Teton River. The highest mountains are at elevations of 2,860 meters (9,390 feet), and the plains are about 1,400 meters (4,500 feet) above sea level. The dark brown areas are grasslands, bright green areas are farms, light brown, orange and purple areas are scrub and forest, and bright white and blue areas are steep rocky slopes. The two radar images were taken on successive days by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on board the space shuttle Endeavour in October 1994. The digital elevation map was produced using radar interferometry, a process in which radar data are acquired on different passes of the space shuttle. The two data passes are compared to obtain elevation information. Radar image data are draped over the topography to provide the color with the following assignments: red is L-band vertically transmitted, vertically received; green is C-band vertically transmitted, vertically received; and blue are the differences seen in the L-band data between the two days. This image is centered near 47.7 degrees north latitude and 112.7 degrees west longitude. No vertical exaggeration factor has been applied to the data. SIR-C/X-SAR, a joint mission of the German, Italian and United States space agencies, is part of NASA's program entitled Mission to Planet Earth.

1994-01-01

403

Metal-shearing energy absorber  

NASA Technical Reports Server (NTRS)

Device, consisting of tongue of thin aluminum alloy strip, pull tab, slotted steel plate which serves as cutter, and steel buckle, absorbs mechanical energy when its ends are subjected to tensile loading. Device is applicable as auxiliary shock absorbing anchor for automobile and airplane safety belts.

Fay, R. J.; Wittrock, E. P.

1971-01-01

404

Synthesis and absorbing mechanism of two-layer microwave absorbers containing polycrystalline iron fibers and carbonyl iron  

NASA Astrophysics Data System (ADS)

Polycrystalline iron fibers were fabricated by ?-FeOOH fiber precursors. Two-layer microwave absorber had been prepared by as-prepared polycrystalline iron fibers and carbonyl iron. The structure, morphology and properties of the composites were characterized with X-ray diffraction, scanning electron microscope and Network Analyzer. The complex permittivity and reflection loss (dB) of the composites were measured employing vector network analyzer model PNA 3629D vector in the frequency range between 30 and 6000 MHz. The thickness effect of the carbonyl iron layer on the microwave loss properties of the composites was investigated. A possible microwave-absorbing mechanism of polycrystalline iron fibers/carbonyl iron composite was proposed. The polycrystalline iron fibers/carbonyl iron composite can find applications in suppression of electromagnetic interference, and reduction of radar signature.

Ding, Qingwei; Zhang, Mingang; Zhang, Cunrui; Qian, Tianwei

2013-04-01

405

Leaf absorbance and photosynthesis  

NASA Technical Reports Server (NTRS)

The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

Schurer, Kees

1994-01-01

406

Spaceborne precipitation radar  

NASA Technical Reports Server (NTRS)

The performances and characteristics of a satelliteborne radar operating in the millimeter wavelength region of the spectrum with emphasis placed on the 35 and 94 GH3 frequency bands are discussed. It is concluded that millimetric wavelengths provide an acceptable solution for the design of satelliteborne active microwave equipment.

Eckerman, J.; Meneghini, R.

1981-01-01

407

The Newcastle meteor radar  

NASA Technical Reports Server (NTRS)

A brief history and development of the Newcastle Meteor Radar system is given. Also described are its geographical coordinates and its method of operation. The initial objective when the project was commenced was to develop an entirely digital analyzer capable of recognizing meteor echo signals and recording as many of their parameters as possible. This objective was achieved.

Keay, Colin

1987-01-01

408

RADAR “SAIL” satellite concept  

Microsoft Academic Search

The Radar SAIL concept is based on the use of a rectangular antenna lying in the dawn-dusk orbital plane with the length (along speed vector) smaller than the height. Such geometry makes it possible to place the solar cells on the back of the antenna, to use gravity gradient stabilisation, and to implement multipath-free GPS interferometric measurement of the antenna

Jean Paul Aguttes; Jacques Sombrin; Eric Conde

1996-01-01

409

Device for absorbing mechanical shock  

DOEpatents

This invention is a comparatively inexpensive but efficient shock-absorbing device having special application to the protection of shipping and storage cylinders. In a typical application, two of the devices are strapped to a cylinder to serve as saddle-type supports for the cylinder during storage and to protect the cylinder in the event it is dropped during lifting or lowering operations. In its preferred form, the invention includes a hardwood plank whose grain runs in the longitudinal direction. The basal portion of the plank is of solid cross-section, whereas the upper face of the plank is cut away to form a concave surface fittable against the sidewall of a storage cylinder. The concave surface is divided into a series of segments by transversely extending, throughgoing relief slots. A layer of elastomeric material is positioned on the concave face, the elastomer being extrudable into slots when pressed against the segments by a preselected pressure characteristic of a high-energy impact. The compressive, tensile, and shear properties of the hardwood and the elastomer are utilized in combination to provide a surprisingly high energy-absorption capability.

Newlon, Charles E. (Knoxville, TN)

1980-01-01

410

Multilayer metamaterial absorbers inspired by perfectly matched layers  

E-print Network

We derive periodic multilayer absorbers with effective uniaxial properties similar to perfectly matched layers (PML). This approximate representation of PML is based on the effective medium theory and we call it an effective medium PML (EM-PML). We compare the spatial reflection spectrum of the layered absorbers to that of a PML material and demonstrate that after neglecting gain and magnetic properties, the absorber remains functional. This opens a route to create electromagnetic absorbers for real and not only numerical applications and as an example we introduce a layered absorber for the wavelength of $8$~$\\mu$m made of SiO$_2$ and NaCl. We also show that similar cylindrical core-shell nanostructures derived from flat multilayers also exhibit very good absorptive and reflective properties despite the different geometry.

Pastuszczak, Anna; Antosiewicz, Tomasz J; Kotynski, Rafal

2014-01-01

411

Landmine detection and imaging using Micropower Impulse Radar (MIR)  

SciTech Connect

The Lawrence Livermore National Laboratory (LLNL) has developed radar and imaging technologies with potential applications in mine detection by the armed forces and other agencies involved in determining efforts. These new technologies use a patented ultra-wideband (impulse) radar technology that is compact, low-cost, and low power. Designated as Micropower hnpulse Radar, these compact, self-contained radars can easily be assembled into arrays to form complete ground penetrating radar imaging systems. LLNL has also developed tomographic reconstruction and signal processing software capable of producing high-resolution 2-D and 3-D images of objects buried in materials like soil or concrete from radar data. Preliminary test results have shown that a radar imaging system using these technologies has the ability to image both metallic and plastic land mine surrogate targets buried in 5 to 10 cm of moist soil. In dry soil, the system can detect buried objects to a depth of 30 cm and more. This report describes our initial test results and plans for future work.

Azevedo, S.G.; Gravel, D.T.; Mast, J.E.; Warhus, J.P.

1995-08-07

412

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging  

NASA Technical Reports Server (NTRS)

Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observatory radar system transmits a single sense of circular polarization, and both senses of circular polarization are received, which allows for the construction of the Stokes polarization vector. From the Stokes vector, daughter products such as the circular polarization ratio, the degree of linear polarization, and linear polarization angle are obtained. Recent polarimetric imaging using Arecibo has included Venus and the Moon. These observations can be compared to radar data for terrestrial surfaces to better understand surface physical properties and regional geologic evolution. For example, polarimetric radar studies of volcanic settings on Venus, the Moon and Earth display some similarities, but also illustrate a variety of different emplacement and erosion mechanisms. Polarimetric radar data provides important information about surface properties beyond what can be obtained from single-polarization radar. Future observations using polarimetric synthetic aperture radar will provide information on roughness, composition and stratigraphy that will support a broader interpretation of surface evolution.

Carter, Lynn M.; Campbell, Donald B.; Campbell, Bruce A.

2010-01-01

413

thin films as absorber  

NASA Astrophysics Data System (ADS)

Photovoltaic structures were prepared using AgSb(S x Se1- x )2 as absorber and CdS as window layer at various conditions via a hybrid technique of chemical bath deposition and thermal evaporation followed by heat treatments. Silver antimony sulfo selenide thin films [AgSb(S x Se1- x )2] were prepared by heating multilayers of sequentially deposited Sb2S3/Ag dipped in Na2SeSO3 solution, glass/Sb2S3/Ag/Se. For this, Sb2S3 thin films were deposited from a chemical bath containing SbCl3 and Na2S2O3. Then, Ag thin films were thermally evaporated on glass/Sb2S3, followed by selenization by dipping in an acidic solution of Na2SeSO3. The duration of dipping was varied as 3, 4 and 5 h. Two different heat treatments, one at 350 °C for 20 min in vacuum followed by a post-heat treatment at 325 °C for 2 h in Ar, and the other at 350 °C for 1 h in Ar, were applied to the multilayers of different configurations. X-ray diffraction results showed the formation of AgSb(S x Se1- x )2 thin films as the primary phase and AgSb(S,Se)2 and Sb2S3 as secondary phases. Morphology and elemental detection were done by scanning electron microscopy and energy dispersive X-ray analysis. X-ray photoelectron spectroscopic studies showed the depthwise composition of the films. Optical properties were determined by UV-vis-IR transmittance and reflection spectral analysis. AgSb(S x Se1- x )2 formed at different conditions was incorporated in PV structures glass/FTO/CdS/AgSb(S x Se1- x )2/C/Ag. Chemically deposited post-annealed CdS thin films of various thicknesses were used as window layer. J- V characteristics of the cells were measured under dark and AM1.5 illumination. Analysis of the J- V characteristics resulted in the best solar cell parameters of V oc = 520 mV, J sc = 9.70 mA cm-2, FF = 0.50 and ? = 2.7 %.

González, J. O.; Shaji, S.; Avellaneda, D.; Castillo, G. A.; Das Roy, T. K.; Krishnan, B.

2014-09-01

414

Freon change in ASR-8 radar <  

NSF Publications Database

The purpose of the activity is to replace existing pressurization agent from Freon-12 to Sulfur Hexafluoride in the ASR-8 Radar.The activity will consist of removing Freon-12 bottle and regulator and installing a bottle of Sulfur Hexafluoride and a new regulator in the existing space occupied by the Freon-12 system. (1) The impact of removing the Freon-12 system, a known ozone depleting material, with Sulfur Hexafluoride can only be beneficial to the environment.

415

Material  

E-print Network

This edition of MaterialEASE focuses on materials selection in general while paying particular attention to the increasing use of the computer in the selection process. Many of the commercial products associated with computer-aided materials selection are evaluated along with an analysis of the development trends. MaterialEASE is also available at AMPTIAC’s Web stie … www.rome.iitri.com/amptiac.

unknown authors

416

Unglazed transpired solar collector having a low thermal-conductance absorber  

DOEpatents

An unglazed transpired solar collector using solar radiation to heat incoming air for distribution, comprises an unglazed absorber formed of low thermal-conductance material having a front surface for receiving the solar radiation and openings in the unglazed absorber for passage of the incoming air such that the incoming air is heated as it passes towards the front surface of the absorber and the heated air passes through the openings in the absorber for distribution. 3 figs.

Christensen, C.B.; Kutscher, C.F.; Gawlik, K.M.

1997-12-02

417

Unglazed transpired solar collector having a low thermal-conductance absorber  

DOEpatents

An unglazed transpired solar collector using solar radiation to heat incoming air for distribution, comprising an unglazed absorber formed of low thermal-conductance material having a front surface for receiving the solar radiation and openings in the unglazed absorber for passage of the incoming air such that the incoming air is heated as it passes towards the front surface of the absorber and the heated air passes through the openings in the absorber for distribution.

Christensen, Craig B. (Boulder, CO); Kutscher, Charles F. (Golden, CO); Gawlik, Keith M. (Boulder, CO)

1997-01-01

418

Impedance matched thin metamaterials make metals absorbing.  

PubMed

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others. PMID:24220284

Mattiucci, N; Bloemer, M J; Aközbek, N; D'Aguanno, G

2013-01-01

419

Impedance matched thin metamaterials make metals absorbing  

NASA Astrophysics Data System (ADS)

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others.

Mattiucci, N.; Bloemer, M. J.; Aközbek, N.; D'Aguanno, G.

2013-11-01

420

Impedance matched thin metamaterials make metals absorbing  

PubMed Central

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others. PMID:24220284

Mattiucci, N.; Bloemer, M. J.; Akozbek, N.; D'Aguanno, G.

2013-01-01

421

41. Perimeter acquisition radar building radar element and coaxial display, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

41. Perimeter acquisition radar building radar element and coaxial display, with drawing of typical antenna section. Drawing, from left to right, shows element, aluminum ground plane, cable connectors and hardware, cable, and back-up ring. Grey area is the concrete wall - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

422

Tunable wide-angle plasmonic perfect absorber at visible frequencies  

NASA Astrophysics Data System (ADS)

We report a perfect absorber metallic hole array with wide-angle near unity absorbance in the visible regime. The periodicity of the structure enables excitation of surface-plasmon polaritons and results in a splitting of the absorbing peaks. An analytical formalism based on perturbation theory provides results in good agreement with experimental data and shows how the absorption peak can be tuned with hole geometry, periodicity, and material parameters. Being extendable to more complex hybrid structures, our result is important for the development of photon harvesting devices and thermal emitters.

Fang, Zheyu; Zhen, Yu-Rong; Fan, Linran; Zhu, Xing; Nordlander, Peter

2012-06-01

423

Optimization of the acoustic absorption coefficients of certain functional absorbents  

NASA Technical Reports Server (NTRS)

The sound absorption coefficients of some functional absorbents (mineral wool plates) are determined by the reverberation chamber method. The influence of the angle of inclination of the sound absorbing material with respect to the surface to be treated is analyzed as well as the influence of the covering index, defined as the ratio of the designed area of a plate and the area of the treated surface belonging to another plate. As compared with the conventional method of applying sound-absorbing plates, the analyzed structures have a higher technological and economical efficiency. The optimum structure corresponds to an angle of inclination of 15 deg and a covering index of 0.8.

Pocsa, V.; Biborosch, L.; Veres, A.; Halpert, E.; Lorian, R.; Botos, T.

1974-01-01

424

Ultrathin multiband gigahertz metamaterial absorbers  

NASA Astrophysics Data System (ADS)

We propose ultrathin multiband metamaterial absorbers in the microwave frequencies in which the design, analysis, fabrication, and measurement of the absorbers working in multiple bands are presented. The metamaterial absorbers consist of a periodic arrangement of different scales of electric-field-coupled-LC (ELC) resonators and a metallic background plane, separated by only 1 mm dielectric spacer. By tuning the scale factor of the ELC unit cells, we achieve independently multiple absorptions at different customized frequencies. Experiments demonstrate excellent absorption rates in the designed frequency bands over wide angles of incident waves for both transverse electric and magnetic polarizations. The explanation to the physical mechanism of the multiband metamaterial absorber is presented and verified.

Li, Hui; Yuan, Li Hua; Zhou, Bin; Shen, Xiao Peng; Cheng, Qiang; Cui, Tie Jun

2011-07-01

425

Acoustical model of a Shoddy fibre absorber  

NASA Astrophysics Data System (ADS)

Shoddy fibres or "Shoddies" are a mixture of post-consumer and post-industrial fibres diverted from textile waste streams and recycled into their raw fibre form. They have found widespread use as a raw material for manufacturing sound absorbers that include, but are not limited to: automotive, architectural and home appliance applications. The purpose of this project is to develop a simple acoustic model to describe the acoustic behaviour of sound absorbers composed primarily of Shoddy fibres. The model requires knowledge of the material's bulk density only. To date, these materials have not been the focus of much published research and acoustical designers must rely on models that were developed for other materials or are overly complex. For modelling purposes, an equivalent fluid approach is chosen to balance complexity and accuracy. In deriving the proposed model, several popular equivalent fluid models are selected and the required input parameters for each model identified. The models are: the model of Delaney and Bazley, two models by Miki, the model of Johnson in conjunction with the model of Champoux and Allard and the model of Johnson in conjunction with the model of Lafarge. Characterization testing is carried out on sets of Shoddy absorbers produced using three different manufacturing methods. The measured properties are open porosity, tortuosity, airflow resistivity, the viscous and thermal characteristic lengths and the static thermal permeability. Empirical relationships between model parameters and bulk density are then derived and used to populate the selected models. This yields several 'simplified' models with bulk density as the only parameter. The most accurate model is then selected by comparing each model's prediction to the results of normal incidence sound absorption tests. The model of Johnson-Lafarge populated with the empirical relations is the most accurate model over the range of frequencies considered (approx. 300 Hz - 4000 Hz) Characterization testing yields specific values for intrinsic material parameters that allow for comparison to other porous materials. Individual parameter relations allow users to substitute measured or theoretical values as needed. A new empirical acoustical model is proposed to describe the behaviour of Shoddy-based fibre absorbers. The model requires knowledge of the bulk density only. This parameter is easily measured making application of the model elementary. Mots-clés : Shoddy, porous, fibre, recycled, absorption, model, acoustic.

Manning, John Peter

426

RADAR Reveals Titan Topography  

NASA Technical Reports Server (NTRS)

The Cassini Titan RADAR Mapper is a K(sub u)-band (13.78 GHz, lambda = 2.17 cm) linear polarized RADAR instrument capable of operating in synthetic aperture (SAR), scatterometer, altimeter and radiometer modes. During the first targeted flyby of Titan on 26 October, 2004 (referred to as Ta) observations were made in all modes. Evidence for topographic relief based on the Ta altimetry and SAR data are presented here. Additional SAR and altimetry observations are planned for the T3 encounter on 15 February, 2005, but have not been carried out at this writing. Results from the T3 encounter relevant to topography will be included in our presentation. Data obtained in the Ta encounter include a SAR image swath

Kirk, R. L.; Callahan, P.; Seu, R.; Lorenz, R. D.; Paganelli, F.; Lopes, R.; Elachi, C.

2005-01-01

427

Floor-plan radar  

NASA Astrophysics Data System (ADS)

Urban-warfare specialists, law-enforcement officers, counter-drug agents, and counter-terrorism experts encounter operational situations where they must assault a target building and capture or rescue its occupants. To minimize potential casualties, the assault team needs a picture of the building's interior and a copy of its floor plan. With this need in mind, we constructed a scale model of a single- story house and imaged its interior using synthetic-aperture techniques. The interior and exterior walls nearest the radar set were imaged with good fidelity, but the distal ones appear poorly defined and surrounded by ghosts and artifacts. The latter defects are traceable to beam attenuation, wavefront distortion, multiple scattering, traveling waves, resonance phenomena, and other effects not accounted for in the traditional (noninteracting, isotropic point scatterer) model for radar imaging.

Falconer, David G.; Ueberschaer, Ronald M.

2000-07-01

428

Advanced ground penetrating radar  

SciTech Connect

An advanced Ground Penetrating Radar (GPR) system has the potential for efficiently and reliably providing high resolution images for inspecting concrete civil structures for defects and damage assessment. To achieve the required performance, improvements in radar hardware, and development and adaptation of advanced 2- and 3-dimensional synthetic aperture imaging techniques are needed. Recent and continuing advancement in computer and computer-related technology areas have made it possible to consider more complex and capable systems for a variety of imaging applications not previously conceived. The authors developed conceptual designs, analyzed system requirements, and performed experiments, modeling, and image reconstructions to study the feasibility of improving GPR technology for non-destructive evaluation of bridge decks and other high-value concrete structures. An overview and summary of practical system concepts and requirements, are presented.

Warhus, J.P.; Mast, J.E.; Johansson, E.M.; Nelson, S.D. [Lawrence Livermore National Lab., CA (United States). Electronics Engineering Dept.

1994-07-26

429

New weather radar coming  

NASA Astrophysics Data System (ADS)

What would you call the next generation of radar for severe weather prediction? NEXRAD, of course. A prototype for the new system was recently completed in Norman, Okla., and by the early 1990s up to 195 stations around the United States will be tracking dangerous weather and sending faster, more accurate, and more detailed warnings to the public.NEXRAD is being built for the Departments of Commerce, Transportation, and Defense by the Unisys Corporation under a $450 million contract signed in December 1987. Th e system will be used by the National Weather Service, the Federal Aviation Administration (FAA), and the U.S. Air Force and Navy. The NEXRAD radar tower in Norman is expected to be operational in October.

Maggs, William Ward

430

Countercurrent flow absorber and desorber  

DOEpatents

Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system. 9 figs.

Wilkinson, W.H.

1984-10-16

431

Packed Alumina Absorbs Hypergolic Vapors  

NASA Technical Reports Server (NTRS)

Beds of activated alumina effective as filters to remove hypergolic vapors from gas streams. Beds absorb such substances as nitrogen oxides and hydrazines and may also absorb acetylene, ethylene, hydrogen sulfide, benzene, butadiene, butene, styrene, toluene, and xoylene. Bed has no moving parts such as pumps, blowers and mixers. Reliable and energy-conservative. Bed readily adapted to any size from small portable units for use where little vapor release is expected to large stationary units for extensive transfer operations.

Thomas, J. J.; Mauro, D. M.

1984-01-01

432

Countercurrent flow absorber and desorber  

DOEpatents

Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system.

Wilkinson, William H. (Columbus, OH)

1984-01-01

433

Radar signal processing  

NASA Astrophysics Data System (ADS)

The role of clutter in radar signal processing is considered with particular reference to an air-traffic environment. The characteristics of clutter are described, and the use of conventional moving-target indication filters to reduce the effects of clutter is considered. Adaptive clutter suppression schemes are addressed, and the adaptive detection of a moving target in the presence of clutter of unknown statistics is discussed. The use of a parametric spectrum estimation procedure as the basis of clutter classification is described.

Haykin, S.

1985-04-01

434

Airborne bistatic radar applications  

Microsoft Academic Search

Applications of bistatic radar when one or both of the units are airborne are discussed. Scenarios that merit deeper consideration are covert strike and head-on SAR using a stand-off illuminator, either airborne or space-based; area air defense with passive ground-based receivers and stand-off illuminators; an airborne picket line to detect stealth aircraft and missiles; AWACS aircraft providing mutual support in

James A. Foster

1987-01-01

435

Imaging synthetic aperture radar  

DOEpatents

A linear-FM SAR imaging radar method and apparatus to produce a real-time image by first arranging the returned signals into a plurality of subaperture arrays, the columns of each subaperture array having samples of dechirped baseband pulses, and further including a processing of each subaperture array to obtain coarse-resolution in azimuth, then fine-resolution in range, and lastly, to combine the processed subapertures to obtain the final fine-resolution in azimuth. Greater efficiency is achieved because both the transmitted signal and a local oscillator signal mixed with the returned signal can be varied on a pulse-to-pulse basis as a function of radar motion. Moreover, a novel circuit can adjust the sampling location and the A/D sample rate of the combined dechirped baseband signal which greatly reduces processing time and hardware. The processing steps include implementing a window function, stabilizing either a central reference point and/or all other points of a subaperture with respect to doppler frequency and/or range as a function of radar motion, sorting and compressing the signals using a standard fourier transforms. The stabilization of each processing part is accomplished with vector multiplication using waveforms generated as a function of radar motion wherein these waveforms may be synthesized in integrated circuits. Stabilization of range migration as a function of doppler frequency by simple vector multiplication is a particularly useful feature of the invention; as is stabilization of azimuth migration by correcting for spatially varying phase errors prior to the application of an autofocus process.

Burns, Bryan L. (Tijeras, NM); Cordaro, J. Thomas (Albuquerque, NM)

1997-01-01

436

Radar response to vegetation  

Microsoft Academic Search

Active microwave measurements of vegetation backscatter were conducted to determine the utility of radar in 1) mapping soil moisture through vegetation and 2) mapping crop types. Using a truck-mounted boom, spectral response data were obtained for four crop types (corn, milo, soybeans, and alfalfa) over the 4-8 GHz frequency band, at incidence angles of0deg-70degin10degsteps, and for all four linear polarization

F. Ulaby

1975-01-01

437

A novel composite sound absorber with recycled rubber particles  

NASA Astrophysics Data System (ADS)

A new kind of composite sound absorber has been fabricated, using recycled rubber particles with good attenuation property as sound energy attenuation layer, low characteristic impedance materials such as polymer porous foam or perforated panel as matching layer. Its' attractive characteristics include: low-cost, broad-band sound absorption, thin in thickness and relatively simple processing. An acoustic transmission analytical model is developed and successfully applied to evaluate the sound absorption of the composite absorber.

Hong, Zhou; Bo, Li; Guangsu, Huang; Jia, He

2007-07-01

438

A review of array radars  

NASA Astrophysics Data System (ADS)

Achievements in the area of array radars are illustrated by such activities as the operational deployment of the large high-power, high-range-resolution Cobra Dane; the operational deployment of two all-solid-state high-power, large UHF Pave Paws radars; and the development of the SAM multifunction Patriot radar. This paper reviews the following topics: array radars steered in azimuth and elevation by phase shifting (phase-phase steered arrays); arrays steered + or - 60 deg, limited scan arrays, hemispherical coverage, and omnidirectional coverage arrays; array radars steering electronically in only one dimension, either by frequency or by phase steering; and array radar antennas which use no electronic scanning but instead use array antennas for achieving low antenna sidelobes.

Brookner, E.

1981-10-01

439

Cognitive processing for nonlinear radar  

NASA Astrophysics Data System (ADS)

An increasingly cluttered electromagnetic environment (EME) is a growing problem for radar systems. This problem is becoming critical as the available frequency spectrum shrinks due to growing wireless communication device usage and changing regulations. A possible solution to these problems is cognitive radar, where the cognitive radar learns from the environment and intelligently modifies the transmit waveform. In this paper, a cognitive nonlinear radar processing framework is introduced where the main components of this framework consist of spectrum sensing processing, target detection and classification, and decision making. The emphasis of this paper is to introduce a spectrum sensing processing technique that identifies a transmit-receive frequency pair for nonlinear radar. It will be shown that the proposed technique successfully identifies a transmit-receive frequency pair for nonlinear radar from data collected from the EME.

Martone, Anthony; Ranney, Kenneth; Hedden, Abigail; Mazzaro, Gregory; McNamara, David

2013-05-01

440

Perfect selective metamaterial solar absorbers.  

PubMed

In this work, we numerically investigate the radiative properties of metamaterial nanostructures made of two-dimensional tungsten gratings on a thin dielectric spacer and an opaque tungsten film from UV to mid-infrared region as potential selective solar absorbers. The metamaterial absorber with single-sized tungsten patches exhibits high absorptance in the visible and near-infrared region due to several mechanisms such as surface plasmon polaritons, magnetic polaritons, and intrinsic bandgap absorption of tungsten. Geometric effects on the resonance wavelengths and the absorptance spectra are studied, and the physical mechanisms are elucidated in detail. The absorptance could be further enhanced in a broader spectral range with double-sized metamaterial absorbers. The total solar absorptance of the optimized metamaterial absorbers at normal incidence could be more than 88%, while the total emittance is less than 3% at 100°C, resulting in total photon-to-heat conversion efficiency of 86% without any optical concentration. Moreover, the metamaterial solar absorbers exhibit quasi-diffuse behaviors as well as polarization independence. The results here will facilitate the design of novel highly efficient solar absorbers to enhance the performance of various solar energy conversion systems. PMID:24514927

Wang, Hao; Wang, Liping

2013-11-01

441

Radar gun hazards  

SciTech Connect

Radar guns - hand-held units used by the law to nail speeders - have been in use since the early '60s. Now they've been accused of causing cancer. Police officers in several states have so far filed eight suits against the manufacturer, claiming that they have contracted rare forms of cancer, such as of the eyelid and the testicle, from frequent proximity to the devices. Spurred by concerns expressed by police groups, researchers at the Rochester Institute of Technology are conducting what they believe to be the first research of its kind in the nation. Last month psychologist John Violanti, an expert in policy psychology and health, sent out a one-page survey to 6,000 active and retired police officers in New York State, asking them about their health and their use of radar guns. Violanti says melanoma, leukemia, and lymph node cancer may be linked to these as well as other electromagnetic devices. The Food and Drug Administration earlier this year issued a warning about radar guns, telling users not to operate them closer than 6 inches from the body. But this may not be a sufficient safeguard since the instruments can give off crisscrossing wave emissions within a police vehicle. The survey will be used to help determine if it would be safer to mount the guns, which are currently either hand-held or mounted on dashboards, outside troopers' cars.

Not Available

1991-12-20

442

Spaceborne Imaging Radar Project  

NASA Technical Reports Server (NTRS)

In June of 1985 the Project Initiation Agreement was signed by the Jet Propulsion Laboratory and the NASA Office of Space Science and Applications for the Spaceborne Imaging Radar Project (SIR). The thrust of the Spaceborne Imaging Radar Project is to continue the evolution of synthetic aperture radar (SAR) science and technology developed during SEASAT, SIR-A and SIR-B missions to meet the needs of the Earth Observing System (EOS) in the mid 1990's. As originally formulated, the Project plans were for a reflight of the SIR-B in 1987, the development of a new SAR, SIR-C, for missions in mid 1989 and early 1990, and the upgrade of SIR-C to EOS configuration with a qualification flight aboard the shuttle in the 1993 time frame (SIR-D). However, the loss of the shuttle Challenger has delayed the first manifest for SIR to early 1990. This delay prompted the decision to drop SIR-B reflight plans and move ahead with SIR-C to more effectively utilize this first mission opportunity. The planning for this project is discussed.

Herman, Neil

1986-01-01

443

Materials  

Microsoft Academic Search

Materials play an important role in manufactured goods. Materials must possess both acceptable properties for their intended\\u000a applications and a suitable ability to be manufactured. These criteria hold true for micromanufacturing, in which parts have\\u000a overall dimensions of less than 1 mm. This chapter begins by reviewing materials usage in Asian and European research in micromanufacturing,\\u000a categorized by manufacturing process.

David Bourell; Kamlakar Rajurkar

444

Radar studies of bird migration  

NASA Technical Reports Server (NTRS)

Observations of bird migration with NASA radars were made at Wallops Island, Va. Simultaneous observations were made at a number of radar sites in the North Atlantic Ocean in an effort to discover what happened to those birds that were observed leaving the coast of North America headed toward Bermuda, the Caribbean and South America. Transatlantic migration, utilizing observations from a large number of radars is discussed. Detailed studies of bird movements at Wallops Island are presented.

Williams, T. C.; Williams, J. M.

1974-01-01

445

Output Tube Emission Characteristics of Operational Radars.  

National Technical Information Service (NTIS)

This report contains the emission spectra of 19 different types of radars, selected to show the different emission spectrum characteristics produced by a variety of radar output tube technologies. The radars include examples of ground-based search, airpor...

R. J. Matheson, J. D. Smilley, G. D. Falcon, V. S. Lawrence

1982-01-01

446

Neural-network laser radar.  

PubMed

A laser radar whose resolution is greater than 1 µm is reported. We present the radar results when they are used for such purposes as determining the size of a void inside a silicon wafer, profiling a cross-sectional pattern of an optical fiber, studying the birefringence of a lithium-niobate crystal, or finding a fault in an optical guide in an optical integrated-circuit wafer. Neural-network theory was used in processing the radar signal. Radar processing based on neural-network theory gave significantly superior resolution compared with Fourier-transform-based processing. PMID:20885600

Lizuka, K; Fujii, S

1994-05-01

447

Radar data processing and analysis  

NASA Technical Reports Server (NTRS)

Digitized four-channel radar images corresponding to particular areas from the Phoenix and Huntington test sites were generated in conjunction with prior experiments performed to collect X- and L-band synthetic aperture radar imagery of these two areas. The methods for generating this imagery are documented. A secondary objective was the investigation of digital processing techniques for extraction of information from the multiband radar image data. Following the digitization, the remaining resources permitted a preliminary machine analysis to be performed on portions of the radar image data. The results, although necessarily limited, are reported.

Ausherman, D.; Larson, R.; Liskow, C.

1976-01-01

448

Millimeter Wave Cloud Radar (MMCR) Handbook  

SciTech Connect

The millimeter cloud radar (MMCR) systems probe the extent and composition of clouds at millimeter wavelengths. The MMCR is a zenith-pointing radar that operates at a frequency of 35 GHz. The main purpose of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops). This radar will also report radar reflectivity (dBZ) of the atmosphere up to 20 km. The radar possesses a doppler capability that will allow the measurement of cloud constituent vertical velocities.

KB Widener; K Johnson

2005-01-30

449

Real-time modeling of a radar sensor for enhanced vision  

NASA Astrophysics Data System (ADS)

Millimetric radar imaging systems have been used to improve situational awareness for flight crew in low visibility approaches. The image from the sensor is projected in a Head-Up Display (HUD) and, for aircraft without Cat-III auto-land facilities, can provide sufficient cues to continue a manual approach past the normal decision height. However, these images may be cluttered, features are often difficult to detect and there is no direct indication of system integrity. Guidance cues can be displayed in the HUD by tracking runway features in the radar image and the use of sensor fusion methods to detect variation in the size and shape of the runway can provide integrity monitoring, for timely warning of system malfunction. In order to develop real-time tracking algorithms, it is necessary to generate synthetic radar images, which exhibit the properties of actual millimetric radar sensors. This paper outlines the model of a radar sensor used to generate real-time radar images incorporating appropriate attenuation and clutter properties. These images are derived from standard 3D visual databases and have been integrated in a flight simulator using a commercial image generation system. The radar model incorporates the effects of material properties of objects, the sensor range and grazing angles and includes atmospheric attenuation. Examples of the radar images are presented in the paper together with a summary of the real-time performance of the radar model to simulate millimeter wave radar images using a proprietary workstation.

Allerton, David J.; Clare, Anthony J.

2003-09-01

450

Planetary radar studies. [radar mapping of the Moon and radar signatures of lunar and Venus craters  

NASA Technical Reports Server (NTRS)

Progress made in studying the evolution of Venusian craters and the evolution of infrared and radar signatures of lunar crater interiors is reported. Comparison of radar images of craters on Venus and the Moon present evidence for a steady state Venus crater population. Successful observations at the Arecibo Observatory yielded good data on five nights when data for a mix of inner and limb areas were acquired. Lunar craters with radar bright ejects are discussed. An overview of infrared radar crater catalogs in the data base is included.

Thompson, T. W.; Cutts, J. A.

1981-01-01

451

Cross-hole radar scanning of two vertical, permeable, reactive-iron walls at the Massachusetts Military Reservation, Cape Cod, Massachusetts  

USGS Publications Warehouse

A pilot-scale study was conducted by the U.S. Army National Guard (USANG) at the Massachusetts Military Reservation (MMR) on Cape Cod, Massachusetts, to assess the use of a hydraulic-fracturing method to create vertical, permeable walls of zero-valent iron to passively remediate ground water contaminated with chlorinated solvents. The study was conducted near the source area of the Chemical Spill-10 (CS-10) plume, a plume containing chlorinated solvents that underlies the MMR. Ground-water contamination near the source area extends from about 24 m (meters) to 35 m below land surface. The USANG designed two reactive-iron walls to be 12 m long and positioned 24 to 37 m below land surface to intersect and remediate part of the CS-10 plume.Because iron, as an electrical conductor, absorbs electromagnetic energy, the US Geological Survey used a cross-hole common-depth, radar scanning method to assess the continuity and to estimate the lateral and vertical extent of the two reactive-iron walls. The cross-hole radar surveys were conducted in boreholes on opposite sides of the iron injection zones using electric-dipole antennas with dominant center frequencies of 100 and 250 MHz. Significant decreases in the radar-pulse amplitudes observed in scans that traversed the injection zones were interpreted by comparing field data to results of two-dimensional finite-difference time-domain numerical models and laboratory-scale physical models.The numerical and physical models simulate a wall of perfectly conducting material embedded in saturated sand. Results from the numerical and physical models show that the amplitude of the radar pulse transmitted across the edge of a conductive wall is about 43 percent of the amplitude of a radar pulse transmitted across background material. The amplitude of a radar pulse transmitted through a hole in a conductive wall increases as the aperture of the hole increases. The modeling results indicate that holes with an aperture of less than 40 percent of the dominant wavelength of the radar pulse are not likely to be detected.Based on the results of the numerical and physical modeling, the decreases in radar-pulse amplitudes observed in scans traversing the injection zones are interpreted as electrically conductive zones that outline the distribution of iron. The area interpreted as iron in the northern A-wall contains two zones -- an upper zone about 10 m wide, extending from about 25 to 31 m below land surface, and a lower zone about 8 m wide, extending from 31.5 to 34.5 m below land surface. The area interpreted as iron in the southern B-wall is about 9 m wide, extending from about 27 to 34.5 m below land surface. No discrete holes were interpreted in either the A- or B-wall zones.The interpretation of the field data suggests that (1) the hydraulic-fracturing method introduced iron into the subsurface, but not in the dimensions originally proposed; (2) the iron within the treatment zones is distributed in a generally continuous manner; and (3) excluding the discontinuity in the A-wall, holes within the iron treatment zone, if any, exist at scales smaller than about 10 cm, the resolution limit of the radar antennas and acquisition geometry used for this study. The cross-hole radar method appears to have been an effective method for delineating the distribution of iron in the two walls; however, the veracity of the results cannot be ascertained without excavation or drilling into the treatment zone.

Lane, J.W., Jr.; Joesten, P.K.; Savoie, J.G.

2001-01-01

452

Simulation, fabrication and characterization of THz metamaterial absorbers.  

PubMed

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical(1) and experimental demonstration(2) of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical(3), near IR(4), mid IR(5) , THz(6) , mm-wave(7) , microwave(8) and radio(9) bands. Applications include perfect lenses(10), sensors(11), telecommunications(12), invisibility cloaks(13) and filters(14,15). We have recently developed single band(16), dual band(17) and broadband(18) THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers(19). In our MM absorber the THz radiation is absorbed in a thickness of ~ ?/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems. PMID:23299442

Grant, James P; McCrindle, Iain J H; Cumming, David R S

2012-01-01

453

Experimental verification of metamaterial based subwavelength microwave absorbers  

NASA Astrophysics Data System (ADS)

We designed, implemented, and experimentally characterized electrically thin microwave absorbers by using the metamaterial concept. The absorbers consist of (i) a metal back plate and an artificial magnetic material layer; (ii) metamaterial back plate and a resistive sheet layer. We investigated absorber performance in terms of absorbance, fractional bandwidth, and electrical thickness, all of which depend on the dimensions of the metamaterial unit cell and the distance between the back plate and metamaterial layer. As a proof of concept, we demonstrated a ? /4.7 thick absorber of type I, with a 99.8% absorption peak along with a 8% fractional bandwidth. We have shown that as the electrical size of the metamaterial unit cell decreases, the absorber electrical thickness can further be reduced. We investigated this concept by using two different magnetic metamaterial inclusions: the split-ring resonator (SRR) and multiple SSR (MSRR). We have also demonstrated experimentally a ? /4.7 and a ? /4.2 thick absorbers of type II, based on SRR and MSRR magnetic metamaterial back plates, respectively. The absorption peak of the SRR layout is 97.4%, while for the MSRR one the absorption peak is 98.4%. The 10 dB bandwidths were 9.9% and 9.6% for the SRR and MSRR cases, respectively.

Alici, Kamil Boratay; Bilotti, Filiberto; Vegni, Lucio; Ozbay, Ekmel

2010-10-01

454

Millimeter radar improves target identification  

NASA Astrophysics Data System (ADS)

Recently developed millimeter wave radar has advantages for target identification over conventional microwave radar which typically use lower frequencies. We describe the pertinent features involved in the construction of the new millimeter wave radar, the pseudo-optical cavity source and the quasi-optical duplexer. The long wavelength relative to light allows the radar beam to penetrate through most weather because the wavelength is larger than the particle size for dust, drizzle rain, fog. Further the mm wave beam passes through an atmospheric transmission window that provides a dip in attenuation. The higher frequency than conventional radar provides higher Doppler frequencies, for example, than X-band radar. We show by simulation that small characteristic vibrations and slow turns of an aircraft become visible so that the Doppler signature improves identification. The higher frequency also reduces beam width, which increases transmit and receive antenna gains. For the same power the transmit beam extends to farther range and the increase in receive antenna gain increases signal to noise ratio for improved detection and identification. The narrower beam can also reduce clutter and reject other noise more readily. We show by simulation that the radar can be used at lower elevations over the sea than conventional radar.

McAulay, Alastair D.

2011-06-01

455

Imaging Radar for Ecosystem Studies  

NASA Technical Reports Server (NTRS)

Recently a number of satellites have been launched with radar sensors, thus expanding opportunities for global assessment. In this article we focus on the applications of imaging radar, which is a type of sensor that actively generates pulses of microwaves and, in the interval between sending pulses, records the returning signals reflected back to an antenna.

Waring, Richard H.; Way, JoBea; Hunt, E. Raymond J.; Morrissey, Leslie; Ranson, K. Jon; Weishampel, John F.; Oren, Ram; Franklin, Steven E.

1996-01-01

456

Landform Identification on Radar Images  

NASA Technical Reports Server (NTRS)

Polarized radar echo images of the Moon acquired using 3.8 and 70 cm wavelengths were examined to learn more about (1) the relationships between theoretical resolutions of the radars and the sizes of landforms that can be identified and (2) the factors that effect landform identification.

Moore, H. J.; Thompson, T. W.

1985-01-01

457

4, 695729, 2004 Radar observations  

E-print Network

ACPD 4, 695­729, 2004 Radar observations of meteor trails W. G. Elford Title Page Abstract Discussion © EGU 2004 Atmos. Chem. Phys. Discuss., 4, 695­729, 2004 www.atmos-chem-phys.org/acpd/4/695/ SRef Discussions Radar observations of meteor trails, and their interpretation using Fresnel holography: a new tool

Paris-Sud XI, Université de

458

New Radar and Navigation Systems  

Microsoft Academic Search

It is not the intention of this paper to give a complete coverage of all new radar and navigation systems, but to concentrate rather more on specific areas and examples where microwaves are used. Also, general coverage of the radar area is felt to be unnecessary following the invited paper given by R. Voles at Microwave 74, however recent advances

K L Fuller

1975-01-01

459

CO2 laser radar  

NASA Astrophysics Data System (ADS)

CO2 laser-based radars operating at 10 microns are both highly energy-efficient and eye-safe, as well as compact and rugged; they also furnish covertness-enhancing fine pointing accuracy, and are difficult to jam or otherwise confuse. Two modes of operation are generally employed: incoherent, in which the laser is simply used as a high power illumination source, and in the presently elaborated coherent or heterodyne mode. Applications encompass terrain-following and obstacle avoidance, Doppler discrimination of missile and aircraft targets, pollutant gas detection, wind measurement for weapons-aiming, and global wind field monitoring.

Brown, D.; Callan, R.; Constant, G.; Davies, P. H.; Foord, R.

460

Anomalous Diffusion with Absorbing Boundary  

E-print Network

In a very long Gaussian polymer on time scales shorter that the maximal relaxation time, the mean squared distance travelled by a tagged monomer grows as ~t^{1/2}. We analyze such sub-diffusive behavior in the presence of one or two absorbing boundaries and demonstrate the differences between this process and the sub-diffusion described by the fractional Fokker-Planck equation. In particular, we show that the mean absorption time of diffuser between two absorbing boundaries is finite. Our results restrict the form of the effective dispersion equation that may describe such sub-diffusive processes.

Yacov Kantor; Mehran Kardar

2007-10-31

461

Radar image registration and rectification  

NASA Technical Reports Server (NTRS)

Two techniques for radar image registration and rectification are presented. In the registration method, a general 2-D polynomial transform is defined to accomplish the geometric mapping from one image into the other. The degree and coefficients of the polynomial are obtained using an a priori found tiepoint data set. In the second part of the paper, a rectification procedure is developed that models the distortion present in the radar image in terms of the radar sensor's platform parameters and the topographic variations of the imaged scene. This model, the ephemeris data and the digital topographic data are then used in rectifying the radar image. The two techniques are then used in registering and rectifying two examples of radar imagery. Each method is discussed as to its benefits, shortcomings and registration accuracy.

Naraghi, M.; Stromberg, W. D.

1983-01-01

462

A radar image time series  

NASA Technical Reports Server (NTRS)

A set of ten side-looking radar images of a mining area in Arizona that were aquired over a period of 14 yr are studied to demonstrate the photogrammetric differential-rectification technique applied to radar images and to examine changes that occurred in the area over time. Five of the images are rectified by using ground control points and a digital height model taken from a map. Residual coordinate errors in ground control are reduced from several hundred meters in all cases to + or - 19 to 70 m. The contents of the radar images are compared with a Landsat image and with aerial photographs. Effects of radar system parameters on radar images are briefly reviewed.

Leberl, F.; Fuchs, H.; Ford, J. P.

1981-01-01

463

An omnidirectional electromagnetic absorber made of metamaterials  

Microsoft Academic Search

In a recent theoretical work by Narimanov and Kildishev (2009 Appl. Phys. Lett. 95 041106) an optical omnidirectional light absorber based on metamaterials was proposed, in which theoretical analysis and numerical simulations showed that all optical waves hitting the absorber are trapped and absorbed. Here we report the first experimental demonstration of an omnidirectional electromagnetic absorber in the microwave frequency.

Qiang Cheng; Tie Jun Cui; Wei Xiang Jiang; Ben Geng Cai

2010-01-01

464

An omnidirectional electromagnetic absorber made of metamaterials  

Microsoft Academic Search

In a recent theoretical work by Narimanov and Kildishev (2009 Appl. Phys. Lett.95 041106) an optical omnidirectional light absorber based on metamaterials was proposed, in which theoretical analysis and numerical simulations showed that all optical waves hitting the absorber are trapped and absorbed. Here we report the first experimental demonstration of an omnidirectional electromagnetic absorber in the microwave frequency. The

Qiang Cheng; Tie Jun Cui; Wei Xiang Jiang; Ben Geng Cai

2010-01-01

465

Parallel-Plate Acoustic Absorbers For Hot Environments  

NASA Technical Reports Server (NTRS)

Stacking patterns and materials chosen to suppress noise. Acoustic liners incorporating parallel-plate absorbing elements proposed for use in suppressing broadband aerodynamic noise originating in flows of hot gases in ducts. One potential application lies in suppressing noise generated in exhaust-jet mixer/ejectors in propulsion system of proposed High-Speed Civil Transport. In addition, such absorbers useful in any situation in which high temperature limits use of such conventional resonant acoustic-liner materials as perforated face sheets bonded to honey-comb-core panels.

Doychak, Joseph; Parrot, Tony L.

1995-01-01

466

Oil and fat absorbing polymers  

NASA Technical Reports Server (NTRS)

A method is described for forming a solid network polymer having a minimal amount of crosslinking for use in absorbing fats and oils. The polymer remains solid at a swelling ratio in oil or fat of at least ten and provides an oil absorption greater than 900 weight percent.

Marsh, H. E., Jr. (inventor)

1977-01-01

467

Abbe's law, 210 absorbing media  

E-print Network

Index Abbe's law, 210 absorbing media apparent lack of energy conservation, 197--198 exceptions to reciprocity, 194--199 non­reversibility of optical paths, 196--197 reciprocity principle for, 198 for refraction, 145--146 adjoint, 147--148 angular form, 172 modified, 152 reciprocity principle for, 180

Stanford University

468

Reactive absorbers Absorption around resonance  

E-print Network

1 Reactive absorbers · Absorption around resonance = 2 m" (-res) +..... ( m"- c 2/l)=(-res) d d [ m silencers ­ Expansion chamber ­ Branch resonator #12;3 Silencers Source ZS Duct 1 Z1 Duct 2 Z2 Receiver ZR

Berlin,Technische Universität

469

An investigation of precipitation attenuation and its application in a dual-frequency radar morphology of subtropical precipitation  

E-print Network

, information about the internal structure of the rain cloud may be inferred. Ob 'ective and Sco e of Stud The dual-frequency radar system in the Department of Oceanography and Meteorology at Texas A&M University provides an opportunity to observe... of their individual molecular structures which behave like dipoles under electromagnetic stresses. Absor tion b Ox en. The oxygen molecule is paramagnetic, i. e. , it has a permanent magnetic moment and thus can absorb microwave energy. The molecule absorbs a...

Greene, Douglas Richard

2012-06-07

470

Antarctic Mapping Project ACTIVE RADAR CALIBRATOR  

E-print Network

and Space Administration and National Science Foundation sponsored second mapping of Antarctica using satellite radar. The ARC is required in the calibration of these radar image data. This active radar. The first radar mapping of Antarctica was completed in 1997. The second mapping will also be accomplished

Howat, Ian M.

471

A new algorithm for radar emitter recognition  

Microsoft Academic Search

A radar electronic support measures (ESM) system performs the functions of threat detection and area surveillance. The received radar pulses are sorted and segregated by the deinterleaver into a number of radar cells depending on the measured parameters of the received pulses. These radar cells will be submitted to the threat library and compared with the stored parameters of known

H. E. Hassan

2003-01-01

472

Joint deinterleaving\\/recognition of radar pulses  

Microsoft Academic Search

A radar electronic support measures (ESM) system performs the functions of threat detection and area surveillance to determine the bearing and the identity of the surrounding radar emitters. The received pulses arc sorted and segregated into a number of deinterleaved radar cells depending on their measured parameters. The parameters of the deinterleaved radar cells will be submitted to the threat

H. E. Hassan

2003-01-01

473

Radar, Insect Population Ecology, and Pest Management  

NASA Technical Reports Server (NTRS)

Discussions included: (1) the potential role of radar in insect ecology studies and pest management; (2) the potential role of radar in correlating atmospheric phenomena with insect movement; (3) the present and future radar systems; (4) program objectives required to adapt radar to insect ecology studies and pest management; and (5) the specific action items to achieve the objectives.

Vaughn, C. R. (editor); Wolf, W. (editor); Klassen, W. (editor)

1979-01-01

474

Course Syllabus Course name: Radar Meteorology  

E-print Network

Course Syllabus Course name: Radar Meteorology Course number: AT741 Instructor: Prof. Steven652, or permission of instructor Course goals and Objectives: AT741 is designed to provide principles, polarimetric radar, dual-wavelength radar, mm-wave radars with applications. The course also

475

Mapping small elevation changes over large areas - Differential radar interferometry  

NASA Technical Reports Server (NTRS)

A technique is described, based on synthetic aperture radar (SAR) interferometry, which uses SAR images for measuring very small (1 cm or less) surface motions with good resolution (10 m) over swaths of up to 50 km. The method was applied to a Seasat data set of an imaging site in Imperial Valley, California, where motion effects were observed that were identified with movements due to the expansion of water-absorbing clays. The technique can be used for accurate measurements of many geophysical phenomena, including swelling and buckling in fault zones, residual displacements from seismic events, and prevolcanic swelling.

Gabriel, Andrew K.; Goldstein, Richard M.; Zebker, Howard A.

1989-01-01

476

Radar determination of the spatial structure of hydraulic conductivity.  

PubMed

Spatial variability of hydraulic conductivity exerts a predominant control on the flow of fluid through porous media. Heterogeneities influence advective pathways, hydrodynamic dispersion, and density-dependent dispersion; they are, therefore, a key concern for studies of ground water resource development, contaminant transport, and reservoir engineering. Ground-penetrating radar contributes to the remote, geophysical characterization of the macroscale variability of natural porous media. On a controlled excavation of a glacial-fluvial sand and gravel deposit in the Fanshawe Delta area (Ontario, Canada), the hydraulic conductivity field of a 45 x 3 m vertical exposure was characterized using constant-head permeameter measurements performed on undisturbed horizontal sediment cores. Ground-penetrating radar data were collected along the excavation face in the form of both reflection and common midpoint surveys. Comparison of geostatistical analyses of the permeameter measurements and the radar data suggests thatthe horizontal correlation structure of radar stack velocity can be used to directly infer the horizontal correlation structure of hydraulic conductivity. The