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1

Radar Absorbing Material Design.  

National Technical Information Service (NTIS)

Low observable platforms have extremely low radar cross section specifications that cannot be achieved by shaping alone. The application of radar absorbing material is necessary, in which case the appropriate constitutive parameters and thickness must be ...

C. K. Yuzcelik

2003-01-01

2

Review of Radar Absorbing Materials.  

National Technical Information Service (NTIS)

Radar is a sensitive detection tool and since its development, methods for reducing microwave reflections have been explored. Radar absorbers can be classified as impedance matching or resonant absorbers. Radar absorbing materials are made from resistive ...

P. Saville

2005-01-01

3

Radar Absorbing Materials: Mechanisms and Materials.  

National Technical Information Service (NTIS)

An introduction is given to the theoretical basis for the design of radar absorbing materials (RAM) with emphasis given on techniques for modifying material properties to give the desired performance. These techniques include additives in the form of scat...

K. Gaylor

1989-01-01

4

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

5

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

6

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

7

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

8

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

9

RAT SCAT Evaluation of Commercially Available Radar Absorbing Materials.  

National Technical Information Service (NTIS)

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...

W. O'Hara

1976-01-01

10

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

11

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

12

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

13

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

14

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

15

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

16

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

17

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

18

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

19

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

20

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

21

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

22

Styrbara Material: Ledande Polymerer i Radarabsorberande Kompositer (Controllable Materials: Conducting Polymers in Radar Absorbing Composites).  

National Technical Information Service (NTIS)

The conductivity of some polymers can be varied with the concentration of doping molecules. This makes it possible to develop dynamically adaptive radar absorbing materials. In the literature (UK, USA) results have been published which indicate that this ...

O. Dickman F. Larsson K. Lindersson J. O. Ousbaeck L. D. Wernlund

1996-01-01

23

Partial treatment of wind turbine blades with radar absorbing materials (RAM) for RCS reduction  

Microsoft Academic Search

The application of radar absorbing materials (RAM) in order to reduce the interference of wind farms with radar systems is considered as a possible mitigation solution. This paper will address the key challenges when trying to efficiently apply RAM to certain parts of the wind turbine blades to significantly reduce the scattering of radar signals. Modeling of the radar cross-section

Laith Rashid; Anthony Brown

2010-01-01

24

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

25

Effects of Radar Absorbing Material (RAM) on the Radiated Power of Monopoles with Finite Ground Plane.  

National Technical Information Service (NTIS)

The effects of Radar Absorbing Material (RAM) on the radiation pattern of a monopole over finite ground plane are presented. The transmitted power of the monopole antenna was measured while varying the separation distances between the ground plane and the...

C. E. Maragoudakis V. Kopsa

2009-01-01

26

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

27

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

28

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

29

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

30

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

31

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

32

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

33

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

34

Monostatic Reflectivity and Transmittance of Radar Absorbing Materials at 650 GHz  

NASA Astrophysics Data System (ADS)

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 those was found to be sufficiently low (from -50 to -60 dB) for use in antenna test ranges. Results agree with earlier studies and indicate the applicability of the RCS method in reflectivity measurements also at 650 GHz.

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

2008-03-01

35

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

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

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

39

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

40

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

41

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

42

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

43

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

44

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

45

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

46

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

47

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

48

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

49

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

50

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

51

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

52

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

53

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

54

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

55

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

56

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

57

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

58

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

59

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

60

Reduction of the radar cross section of a wind turbine using a microwave absorbing material  

Microsoft Academic Search

Wind turbines are devices which usually have a large surface area. The combination of effects related to the large surface area and properties of the materials used in their construction can make a wind turbine an important reflector of radar waves, which may interfere with the proper operation of civilian and military radars. There are several possible methods to reduce

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

2011-01-01

61

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

62

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

63

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

64

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

65

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

66

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

67

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

68

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

69

A Novel, Real-Valued Genetic Algorithm for Optimizing Radar Absorbing Materials  

NASA Technical Reports Server (NTRS)

A novel, real-valued Genetic Algorithm (GA) was designed and implemented to minimize the reflectivity and/or transmissivity of an arbitrary number of homogeneous, lossy dielectric or magnetic layers of arbitrary thickness positioned at either the center of an infinitely long rectangular waveguide, or adjacent to the perfectly conducting backplate of a semi-infinite, shorted-out rectangular waveguide. Evolutionary processes extract the optimal physioelectric constants falling within specified constraints which minimize reflection and/or transmission over the frequency band of interest. This GA extracted the unphysical dielectric and magnetic constants of three layers of fictitious material placed adjacent to the conducting backplate of a shorted-out waveguide such that the reflectivity of the configuration was 55 dB or less over the entire X-band. Examples of the optimization of realistic multi-layer absorbers are also presented. Although typical Genetic Algorithms require populations of many thousands in order to function properly and obtain correct results, verified correct results were obtained for all test cases using this GA with a population of only four.

Hall, John Michael

2004-01-01

70

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

71

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

72

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

73

Terahertz backscattering behavior of various absorbing materials  

Microsoft Academic Search

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

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

2009-01-01

74

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

75

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

76

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

77

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

78

Advanced neutron absorber materials  

DOEpatents

A neutron absorbing material and method utilizing rare earth elements such as gadolinium, europium and samarium to form metallic glasses and/or noble base nano/microcrystalline materials, the neutron absorbing material having a combination of superior neutron capture cross sections coupled with enhanced resistance to corrosion, oxidation and leaching.

Branagan, Daniel J. (Idaho Falls, ID); Smolik, Galen R. (Idaho Falls, ID)

2000-01-01

79

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

80

Radar Cross Section Reduction by Absorber Covering  

Microsoft Academic Search

Radar cross section (RCS) reduction by absorber covering is experimentally studied by employing microwave diversity imaging. Experimental results show that broadband absorber covering is not effective at reducing the co-polarized (the transmitting andreceiving antennas have opposite sense of circular polarization) RCS of a plate when the incident wave approximates the edge-on direction but is effective at reducing the cross-polarized (both

H. J. Li; N. H. Farhat; Y. Shen

1989-01-01

81

Radar cross section reduction by absorber covering  

Microsoft Academic Search

Radar cross section (RCS) reduction by absorber covering is experimentally studied by employing microwave diversity imaging. Experimental results show that broadband absorber covering is not effective at reducing the co-polarized (the transmitting and receiving antennas have opposite sense of circular polarization) RCS of a plate when the incident wave approximates the edge-on direction but is effective at reducing the cross-polarized

H. J. Li; N. H. Farhat; Y. Shen

1989-01-01

82

Radar cross section reduction by absorber covering  

NASA Technical Reports Server (NTRS)

Radar cross section (RCS) reduction by absorber covering is experimentally studied by employing microwave diversity imaging. Experimental results show that broadband absorber covering is not effective at reducing the co-polarized (the transmitting and receiving antennas have opposite sense of circular polarization) RCS of a plate when the incident wave approximates the edge-on direction but is effective at reducing the cross-polarized (both the transmitting and receiving antennas have the same sense of circular polarization) RCS for all incident directions. The surface current absorber covering is effective at reducing the nonspecular energy and multiple bounces regardless of the polarization status of the measurement.

Li, H. J.; Farhat, N. H.; Shen, Y.

1989-01-01

83

Projekt Avancerade Radarabsorbenter Slutrapport (Project Advanced Radar Absorbers, Final Report).  

National Technical Information Service (NTIS)

The report presents results and activities obtained in the project Advanced radar absorbers during the years 2001-2003. The goal of the project has been to develop and characterize materials and structures for signature control (low observables), in the m...

J. O. Ousbaeck

2003-01-01

84

Development of radar absorbing nano crystals by microwave irradiation  

Microsoft Academic Search

Single phase M-type barium hexaferrite nano crystals of radar absorbing material i.e., BaFe12O19 were synthesized by a modified flux method under cyclic microwave irradiation. Uniform and ultrafast morphological transformation from spherical to pyramidal-faced nano crystals were noticed in field emission electron microscopy during the cyclic microwave irradiation power for constant time. The reflection loss of nano crystals in Ku band

Rahul Sharma; R. C. Agarwala; Vijaya Agarwala

2008-01-01

85

Radarabsorberande Multilagerskikt Baserat pa Magnetiska Keramer; Karakterisering av Foerlustmaterial, Optimering och Verifiering (Radarabsorbing Multilayer Coating Based on Ferrites. Characterization of Radar Absorbing Materials, Optimization and Verification).  

National Technical Information Service (NTIS)

A radar absorbing multilayer coating optimized for the 2 - 12 GHz frequency range was manufactured and characterized with respect to reflection. The coating was made of three layers; magnetite/epoxy composite, NiZn-ferrite/epoxy composite, and epoxy. Comp...

O. Olsson P. O. Olsson J. Westlund N. Gustafsson

1997-01-01

86

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

87

Compatibility Study of an Absorber Material and Two Silicone Adhesives.  

National Technical Information Service (NTIS)

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, r...

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

1988-01-01

88

Chiral absorbing material  

Microsoft Academic Search

The paper presents the analysis for plane wave scattering from a grounded chiral substrate that is loaded by an array of square patches for the sake of minimizing the radar cross section (RCS) for the equipment covered by them. The analysis includes a chiral substrate with different electromagnetic parameters. It shows moderate frequency bands of good absorption for the structures

A. M. M. Allam

2000-01-01

89

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

90

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

91

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

92

Solar Radiation Absorbing Material.  

National Technical Information Service (NTIS)

Solar energy absorbing means in solar collectors are provided by a solar selective carbon surface. A solar selective carbon surface is a microporous carbon surface having pores within the range of 0.2 to 2 micrometers. Such a surface is provided in a micr...

J. M. Googin C. R. Schmitt J. M. Schreyer H. D. Whitehead

1976-01-01

93

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

94

Review in Sound Absorbing Materials  

Microsoft Academic Search

This article is a bibliographical revision concerning acoustic absorbing materials, also known as poroelastics. These absorbing\\u000a materials are a passive medium use extensively in the industry to reduce noise. This review presents the fundamental parameters\\u000a that define each of the parts comprising these materials, as well as current experimental methods used to measure said parameters.\\u000a Further along, we will analyze

X. Sagartzazu; L. Hervella-Nieto; J. M. Pagalday

2007-01-01

95

Porcelain enamel neutron absorbing material  

DOEpatents

A porcelain enamel composition as a neutron absorbing material can be prepared of a major proportion by weight of a cadmium compound and a minor proportion of compounds of boron, lithium and silicon. These compounds in the form of a porcelain enamel coating or layer on several alloys has been found to be particularly effective in enhancing the nuclear safety of equipment for use in the processing and storage of fissile material. The composition of the porcelain enamel coating can be tailored to match the coefficient of thermal expansion of the equipment to be coated and excellent coating adhesion can be achieved.

Iverson, Daniel C. (Aiken, SC)

1990-01-01

96

Porcelain enamel neutron absorbing material  

DOEpatents

A porcelain enamel composition as a neutron absorbing material can be prepared of a major proportion by weight of a cadmium compound and a minor proportion of compound of boron, lithium and silicon. These compounds in the form of a porcelain enamel coating or layer on several alloys has been found to be particularly effective in enhancing the nuclear safety of equipment for use in the processing and storage of fissile material. The composition of the porcelain enamel coating can be tailored to match the coefficient of thermal expansion of the equipment to be coated and excellent coating adhesion can be achieved. 2 figs.

Iverson, D.C.

1987-11-20

97

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

98

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

99

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

100

Target material characterization using high-order signal processing of ultra-wideband radar data  

Microsoft Academic Search

Results obtained by two high-order signal processing methods applied to ultrawideband (UWB) radar data in the UHF band are described. The UWB radar data were collected in a specially designed bistatic test range. Four types of UWB signals were used to test a metal (reference) plate, five different commercially available radar absorbing material samples with metal backing, and five natural

Vasilis Z. Marmarelis; David Sheby; Elizabeth C. Kisenwether; Todd A. Erdley

1992-01-01

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

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

103

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

104

3-d simulations for radar cross-section reduction using plasma absorbers  

Microsoft Academic Search

Summary form only given. Radar cross section (RCS) is the measure of a target's ability to reflect radar signals in the direction of the radar receiver. A collisional unmagnetized plasma, surrounding the target, acts as a good absorber of electromagnetic waves over a wide frequency range, reducing its RCS. This has given rise to world wide interest in plasma stealth

B. Chaudhury; S. Chaturvedi

2006-01-01

105

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

106

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

107

Design and Manufacture of Energy Absorbing Materials  

ScienceCinema

Learn about an ordered cellular material that has been designed and manufactured using direct ink writing (DIW), a 3-D printing technology being developed at LLNL. The new material is a patterned cellular material that can absorb mechanical energy-a cushion-while also providing protection against sheering. This material 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

2014-05-30

108

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

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

Determination of absorbed beta dose in materials  

SciTech Connect

It is necessary during construction and subsequent operation of a commercial nuclear power reactor to evaluate the impact of the absorbed dose on the useful life of equipment and components. Routinely, the gamma contribution to this absorbed dose is evaluated, and major vendors provide information pertaining to equipment qualification for use in a radiation environment. When evaluating the absorbed beta dose to facility equipment, the source term is readily available during construction from the vendor's radiation design guide. This source term may be used to project potential post-loss of coolant accident (LOCA) equipment dose. After rector startup, the actual source term may be determined by laboratory analysis of the affected system components. This article clarifies existing practices and calculational methods, and provides a straight-forward method for evaluating the absorbed beta dose in materials.

Brown, D.D. (Chem-Nuclear Geotech, Inc. (US))

1992-07-01

111

Energy absorbing hybrid nano-composite materials  

Microsoft Academic Search

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

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

2009-01-01

112

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

113

Modeling of ground-penetrating-radar antennas with shields and simulated absorbers  

Microsoft Academic Search

A three-dimensional (3-D) finite-difference time-domain (FDTD) scheme is employed to simulate ground-penetrating radars. Conducting shield walls and absorbers are used to reduce the direct coupling to the receiver. Perfectly matched layer (PML) absorbing boundary conditions are used for matching the multilayered media and simulating physical absorbers inside the FDTD computational domain. Targets are modeled by rectangular prisms of arbitrary permittivity

U. Oguz; L. Gurel

2001-01-01

114

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

115

Method of designing layered sound absorbing materials  

NASA Astrophysics Data System (ADS)

A widely used model for describing sound propagation in porous materials is the Johnson-Champoux-Allard model. This rigid frame model is based on five geometrical properties of the porous medium: resistivity, porosity, tortuosity, and viscous and thermal characteristic lengths. Using this model and with the knowledge of such properties for different absorbing materials, the design of a multiple layered system can be optimized efficiently and rapidly. The overall impedance of the layered systems can be calculated by the repeated application of single layer impedance equation. The knowledge of the properties of the materials involved in the layered system and their physical meaning, allows to perform by computer a systematic evaluation of potential layer combinations rather than do it experimentally which is time consuming and always not efficient. The final design of layered materials can then be confirmed by suitable measurements. A method of designing the overall acoustic absorption of multiple layered porous materials is presented. Some aspects based on the material properties, for designing a flat layered absorbing system are considered. Good agreement between measured and computed sound absorption coefficients has been obtained for the studied configurations. [Work supported by N.S.E.R.C. Canada, F.C.A.R. Quebec, and Bombardier Aerospace.

Atalla, Youssef; Panneton, Raymond

2002-11-01

116

Measurement of electromagnetic properties of absorbing materials in the aerospace industry: issues and (some) answers  

Microsoft Academic Search

Summary form only given. Electromagnetic measurement problems that arise in connection with the use of radar absorbing material in aerospace design and production were reviewed. Some of the most successful and most promising measurement techniques were discussed. These include resonant stripline, waveguide, free space insertion loss, impedance measurement in a capacitive fixture, and Q-spoiling of a cavity. In many cases,

D. A. Luippold; K. M. Mitzner; D. S. Hunzeker; W. Hant; F. J. Murray; S. S. Locus

1992-01-01

117

Framstaellning av Poroesa Keramkiska Radaradsorptionsmaterial foer Hoegtemperaturtillaempningar (Preparation of Radar Absorption Material for High Temperature Application).  

National Technical Information Service (NTIS)

A method for producing porous material presented by Woods et al. Has been studied with the intention to obtain a porous radar absorbing material. The porous body is made by reacting water with a mixture of the desired material and a gas forming substance ...

P. O. Olsson K. Lindersson J. Ruokolahti

1999-01-01

118

Design of an Ultra-Thin Magnetic-Type Radar Absorber Embedded With FSS  

Microsoft Academic Search

In this letter, the design of an ultra-thin magnetic-type radar absorber (RA) having good absorbing performance at low frequency is demonstrated. A 2-mm-thick RA with an operating bandwidth of 1.5-2.2 GHz is obtained on the basis of polymer composites filled with carbonyl iron and Co2Z ferrite. The use of frequency selective surfaces (FSSs) results in a significant increase of operating

Hai-Yan Chen; Hui-Bin Zhang; Long-Jiang Deng

2010-01-01

119

Decontamination of the skin with absorbing materials.  

PubMed

Stimulation of the penetration of topically applied substances into the skin is a topic of intensive dermatological and pharmacological research. Next to intercellular penetration, i.e. a penetration inside the lipid layers around the corneocytes, follicular penetration also represents an efficient penetration pathway. The hair follicles act as a long-term reservoir for topically applied substances. They are surrounded by or contain several important target structures, such as blood capillaries, stem cells and dendritic cells. Therefore, the hair follicles have to be well protected from hazardous substances coming into contact with the skin. The traditional method of decontamination of the skin involves an intensive washing procedure. However, this process represents a massage, which pushes the hazardous substances even deeper into the hair follicles. In the present study, the application of absorbing materials for decontamination of the skin was investigated after the application of a model substance utilizing the tape-stripping procedure. It was found that absorbing materials are better suited than the washing process for decontamination of the skin. PMID:21116121

Lademann, J; Patzelt, A; Schanzer, S; Richter, H; Gross, I; Menting, K H; Frazier, L; Sterry, W; Antoniou, C

2011-01-01

120

Corrosion resistant zirconium alloy absorber material  

SciTech Connect

A method is described of making a zirconium alloy absorber material comprising the steps of: providing a zirconium alloy having iron in a range from about 0.2 to about 0.5 wt. %; about 50 to 120 ppm silicon; about 1,000 to 2,000 ppm oxygen; one or more additional alloying metals selected from the group consisting of tin in a range of from a measurable amount up to about 1.4 wt. chromium in a range from about 0.07 to about 0.25 wt. niobium in a range from a measurable amount up to about 0.6 wt. %, and vanadium in a range of from a measurable amount up to about 0.5 wt. %; and a balance of zirconium; and adding erbium in a range of from about 0.05 to 2.0 wt. % selected from the group consisting of a naturally occurring distribution of erbium isotopes, isotopically enriched erbium- 167, and a combination thereof to act as a burnable absorber.

Pati, S.R.; Corsetti, L.V.

1993-08-31

121

High power ultra wideband radar exotic material response  

Microsoft Academic Search

This paper is the first of two that present analytical and numerical analysis of high power and ultra wide band radars interacting with EMI and radar suppression materials. Magnetic materials are often used in isolators, thin film EMI materials and\\/or appliques. Such magnetic composites may be exposed to wide band and\\/or high power signals in operational radar systems. We describe

Rick L. Moore; John Meadors; Robert Rice

2008-01-01

122

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

123

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

124

Flexor Tenorrhaphy Using Absorbable Suture Materials  

PubMed Central

Background Nonabsorbable sutures are favorable for repairing flexor tendons. However, absorbable sutures have performed favorably in an animal model. Methods Two-strand sutures using the interlocking modified Kessler method with polydioxanone absorbable sutures 4-0 were used to repair completely ruptured flexor tendons in 55 fingers from 41 consecutive patients. The medical records of average 42 follow up weeks were analyzed retrospectively. The data analyzed using the chi-squared test, and Fisher's exact test was used for postoperative complications. The results were compared with those of other studies. Results Among the index, middle, ring, and little fingers were injured in 9, 17, 16, and 13 fingers, respectively. The injury levels varied from zone 1 to 5. Of the 55 digits in our study, there were 26 (47%) isolated flexor digitorum profundus (FDP) injuries and 29 (53%) combined FDP and with flexor digitorum superficialis injuries. Pulley repair was also conducted. Concomitant injuries of blood vessels and nerves were found in 17 patients (23 fingers); nerve injuries occurred in 5 patients (10 fingers). Two patients had ruptures (3.6%), and one patient had two adhesions (3.6%). Using the original Strickland criteria, all the patients were assessed to be excellent or good. Also, fibrosis and long-term foreign body tissue reactions such as stitch granuloma were less likely occurred in our study. Compared to the Cullen's report that used nonabsorbable sutures, there was no significant difference in the rupture or adhesion rates. Conclusions Therefore, this study suggests that appropriate absorbable core sutures can be used safely for flexor tendon repairs.

Kang, Hyung Joo; Kim, Jin Soo; Ki, Sae Hwi; Roh, Si Young; Yang, Jae Won

2012-01-01

125

Radar cross-section study of cylindrical cavity-backed apertures with outer or inner material coating: the case of H-polarization  

Microsoft Academic Search

A dual-series-based solution is obtained for the scattering of an H-polarized plane wave from a slitted infinite circular cylinder coated with absorbing material from inside or outside. For both cases, numerical results are presented for the radar cross section and comparisons are given for two different realistic absorbing materials. The radar cross-section dependencies are also given for the aspect angle

Dilek Colak; Alexander I. Nosich; Ayhan Altintas

1995-01-01

126

Absorption enhancement of fractal frequency selective surface absorbers by using microwave absorbing material based substrates  

NASA Astrophysics Data System (ADS)

In this paper, the effect of microwave absorbing material-based (MAM) substrate on the absorption properties of fractal frequency selective surface (FSS) absorbers was investigated in detail. The fractal shapes were proposed to construct the schematic diagrams of the FSS unit cell. The absorption properties of the absorber samples containing different substrates, including FR-4dielectric substrate and MAM-based substrate, were exhibited via the Naval Research Laboratory (NRL)-arch method, respectively. Then the power loss density distributions of the absorbers were illustrated by the finite integration technology (FIT) method to obtain an insight of the physical picture into the absorption properties. The results indicate that with the increase of the substrate thicknesses, the FR-4-based FSS absorbers could achieve the strongest absorbing performance at a certain thickness. However, employing the MAM-based substrate to replace the FR-4 substrate with the same substrate thickness enhances the absorbing properties greatly, including the peak values and the bandwidths. As a result, the way of introducing the MAM-based substrates instead of the traditional dielectric substrates provides a potential practical application in device miniaturization.

Liao, Zhangqi; Gong, Rongzhou; Nie, Yan; Wang, Tao; Wang, Xian

2011-07-01

127

New Solutions for Energy Absorbing Materials.  

National Technical Information Service (NTIS)

The objective of this project was to understand, design, and evaluate composite materials containing engineered microstructures that display negative stiffness (NS) and negative Poisson s ratio (auxetic) behavior. The ultimate aim for understanding such m...

A. Alderson C. C. Seepersad K. Alderson M. R. Haberman P. S. Wilson

2012-01-01

128

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

129

Radar observables  

NASA Astrophysics Data System (ADS)

A comprehensive account is given of missile design considerations relevant to the prediction, control, and measurement of airframe radar cross sections (RCSs), with a view to the minimization of missile observability. RCS reduction may proceed through airframe shaping to deflect incident radar emissions, as well as through the use of radar-absorbing surface materials and the devision of active radar signal-cancellation methods; some combination of these is often required, due to the deficiencies of any one method. The interaction of all RCS-reduction methods with airframe aerodynamic-design criteria are stressed.

Knott, Eugene F.

130

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

131

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.

132

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

133

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

134

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

135

Observation of beta-ray spectra after penetrating absorbing materials.  

PubMed

beta-Ray spectra after penetrating absorbing materials of various thicknesses were observed by the use of a scintillation-type beta-ray spectrometer equipped with a flat NE-102 plastic scintillator of 5mm thickness for sources of (60)Co, (90)Sr-(90)Y, (137)Cs, (147)Pm and (204)Tl. Although the spectra changed rapidly with increasing absorber thickness, the average beta-ray energy was kept nearly constant for a wider range. These results are consistent in that the beta-ray absorption curve becomes quasi-linear in a semi-logarithmic plot. Spectra including scattered beta-rays from several materials placed behind the source were also measured for (137)Cs and (204)Tl. It may be concluded that mean energy measurements by the use of beta-ray spectrometer of this kind is useful for the identification of nuclides in radiation protection purposes even in worse source-conditions. PMID:18387807

Kawada, Y; Yamada, T; Itoh, J; Sato, Y; Yunoki, A; Hino, Y

2008-01-01

136

A new neutron absorber material for criticality control  

SciTech Connect

A new neutron absorber material based on a nickel metal matrix composite has been developed for applications such as the Transport, Aging, and Disposal (TAD) canister for the Yucca Mountain Project. This new material offers superior corrosion resistance to withstand the more demanding geochemical environments found in a 300,000 year to a million year repository. The lifetime of the TAD canister is currently limited to 10,000 years, reflecting the focus of current regulations embodied in 10 CFR 63. The use of DOE-owned nickel stocks from decommissioned enrichment facilities could reduce the cost compared to stainless steel/boron alloy. The metal matrix composite allows the inclusion of more than one neutron absorber compound, so that the exact composition may be adjusted as needed. The new neutron absorber material may also be used for supplementary criticality control of stored or transported PWR spent fuel by forming it into cylindrical pellets that can be inserted into a surrogate control rod. (authors)

Wells, Alan H. [PhD Consultant, 2846 Peachtree Walk, Duluth, GA 30096 (United States)

2007-07-01

137

Thermal imaging of subsurface microwave absorbers in dielectric materials  

NASA Astrophysics Data System (ADS)

The use of microwaves as a heating source in time-resolved IR radiometry provides the ability to heat surface and subsurface microwave-absorbing regions of a specimen directly. This can improve the contrast and spatial resolution of such regions and enhance their detectibility when compared with conventional laser or flashlamp sources. The experiments reported here use microwave heating with IR detection. Results on plexiglass-water-Teflon test specimens with absorbers at different depths in the sample are described by a 1D analytical model. Measurements using microwave and optical heating on epoxy-coated steel pipes are compared and demonstrate the ability of microwave heating to detect subsurface water voids very efficiently. Other applications of the method to microwave imaging, field mapping and imaging of defects in composite materials are discussed.

Osiander, Robert; Spicer, Jane W.; Murphy, John C.

1994-03-01

138

Material Model Evaluation of a Composite Honeycomb Energy Absorber  

NASA Technical Reports Server (NTRS)

A study was conducted to evaluate four different material models in predicting the dynamic crushing response of solid-element-based models of a composite honeycomb energy absorber, designated the Deployable Energy Absorber (DEA). Dynamic crush tests of three DEA components were simulated using the nonlinear, explicit transient dynamic code, LS-DYNA . In addition, a full-scale crash test of an MD-500 helicopter, retrofitted with DEA blocks, was simulated. The four material models used to represent the DEA included: *MAT_CRUSHABLE_FOAM (Mat 63), *MAT_HONEYCOMB (Mat 26), *MAT_SIMPLIFIED_RUBBER/FOAM (Mat 181), and *MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM (Mat 142). Test-analysis calibration metrics included simple percentage error comparisons of initial peak acceleration, sustained crush stress, and peak compaction acceleration of the DEA components. In addition, the Roadside Safety Verification and Validation Program (RSVVP) was used to assess similarities and differences between the experimental and analytical curves for the full-scale crash test.

Jackson, Karen E.; Annett, Martin S.; Fasanella, Edwin L.; Polanco, Michael A.

2012-01-01

139

Boron-copper neutron absorbing material and method of preparation  

DOEpatents

A composite, copper clad neutron absorbing material is comprised of copper powder and boron powder enriched with boron 10. The boron 10 content can reach over 30 percent by volume, permitting a very high level of neutron absorption. The copper clad product is also capable of being reduced to a thickness of 0.05 to 0.06 inches and curved to a radius of 2 to 3 inches, and can resist temperatures of 900.degree. C. A method of preparing the material includes the steps of compacting a boron-copper powder mixture and placing it in a copper cladding, restraining the clad assembly in a steel frame while it is hot rolled at 900.degree. C. with cross rolling, and removing the steel frame and further rolling the clad assembly at 650.degree. C. An additional sheet of copper can be soldered onto the clad assembly so that the finished sheet can be cold formed into curved shapes.

Wiencek, Thomas C. (Bolingbrook, IL); Domagala, Robert F. (Indian Head Park, IL); Thresh, Henry (Palos Hts., IL)

1991-01-01

140

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

141

Radar Cross Section Target Supports, Plastic Materials.  

National Technical Information Service (NTIS)

The results of studies into the scattering properties of cellular plastic materials are presented. A mathematical model for scattering from cellular plastics, developed to provide a method of determining the optimum low cross section target support for a ...

C. H. Smith C. C. Freeny E. F. Knott T. B. A. Senior

1964-01-01

142

An Automated Dual Horn-Reflector Microwave Absorber Measurement System. Volume I.  

National Technical Information Service (NTIS)

In recent years, extreme interest has been shown in materials which absorb electromagnetic energy in the microwave and millimeter frequency bands. One of the primary methods of evaluating Radar Absorbing Materials (RAM) is to obtain the electrical and mag...

B. Kent

1982-01-01

143

Broadband transmission noise reduction of smart panels featuring piezoelectric shunt circuits and sound-absorbing material  

Microsoft Academic Search

The possibility of a broadband noise reduction of piezoelectric smart panels is experimentally studied. A piezoelectric smart panel is basically a plate structure on which piezoelectric patches with electrical shunt circuits are mounted and sound-absorbing material is bonded on the surface of the structure. Sound-absorbing material can absorb the sound transmitted at the midfrequency region effectively while the use of

Jaehwan Kim; Joong-Kuen Lee

2002-01-01

144

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

145

Resolution function of nonsinusoidal radar signals. I. Range-velocity resolution with rectangular pulses  

Microsoft Academic Search

A generalization of a previously published ambiguity function that applies to radar known as large-relative-bandwidth radar, carrier-free radar, impulse radar, or nonsinusoidal radar is discussed. This radar has attracted attention because of its ability to penetrate absorbing materials used in the stealth technology. Another good application is the detection of moving targets with a small radar cross section by a

N. J. Mohamed

1990-01-01

146

Resolution function of nonsinusoidal radar signals. I - Range-velocity resolution with rectangular pulses  

Microsoft Academic Search

A generalization of a previously published ambiguity function that applies to radar known as large-relative-bandwidth radar, carrier-free radar, impulse radar, or nonsinusoidal radar is discussed. This radar has recently attracted attention because of its ability to penetrate absorbing materials used in the stealth technology. Another good application is the detection of moving targets with a small radar cross section by

Nasser J. Mohamed

1990-01-01

147

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

148

Microwave absorption properties of fabric coated absorbing material using modified carbonyl iron power  

Microsoft Academic Search

The modified absorbing agent was prepared by depositing copper particles on carbonyl iron power (CIP) using a ultrasonic electroless copper plating method. Subsequently, a fabric coated absorbing material was fabricated on non-woven fabric coated absorbing dope containing 85wt% modified CIP. Scanning electron microscope (SEM) and energy dispersion spectrum (EDS) were used to analyze the microstructure and components of modified CIP.

Wei-ping Li; Li-qun Zhu; Jing Gu; Hui-cong Liu

2011-01-01

149

Generalized material-independent PML absorbers for the FDTD simulation of electromagnetic waves in arbitrary anisotropic dielectric and magnetic media  

Microsoft Academic Search

To simply and effectively absorb waves propagating in anisotropic materials consisting of both arbitrary permittivity and permeability tensors, generalized material-independent perfectly matched layer (GMIPML) absorbers are proposed. Within the GMIPML absorbers, electric displacement D and flux density B are directly absorbed, whereas electric field E and magnetic field H are simultaneously absorbed through the relations between E and D as

An Ping Zhao; Jaakko Juntunen; A. V. Raisanen

1998-01-01

150

Solar absorber material stability under high solar flux  

NASA Astrophysics Data System (ADS)

Solar absorbing Black Chrome coatings have been exposed to high temperatures (350-400 C) under high solar fluxes (0.4 to 2.0 MW/sq m) to test for their stability under actual operating conditions. Field tests at the White Sands Solar Furnace have shown higher stability than expected from oven tested samples. Laboratory studies utilizing spectrally selective concentrated solar simulated radiation have indicated that the cause of the higher stability under solar irradiation is photo-stimulated desorption of oxygen bearing species at the absorber surface and resultant reduced oxidation of the absorber.

Ignatiev, A.; Zajac, G.; Smith, G. B.

151

Radar cross-section calculation method for antenna of P-18 radar station  

Microsoft Academic Search

The scattered electromagnetic field calculation method for finite cylinder with resonant cross-section is considered. The method is used for calculation of radar cross-section for antenna of P-18 radar station. Also radar cross-sections for perfectly conducting antenna and antenna partially made of perfectly absorbing materials (Macdonald model) are compared.

O. Sukharevsky; Y. Belevshchuk; V. Vasilets; S. Nechitaylo

2010-01-01

152

Levelized Cost of Coating (LCOC) for Selective Absorber Materials.  

National Technical Information Service (NTIS)

A new metric has been developed to evaluate and compare selective absorber coatings for concentrating solar power applications. Previous metrics have typically considered the performance of the selective coating (i.e., solar absorptance and thermal emitta...

C. K. Ho J. E. Pacheco

2013-01-01

153

Improving Impact Resistance of Ceramic Materials by Energy Absorbing Surface Layers.  

National Technical Information Service (NTIS)

Energy absorbing surface layers were used to improve the impact resistance of silicon nitride and silicon carbide ceramics. Low elastic modulus materials were used. In some cases, the low elastic modulus was achieved using materials that form localized mi...

H. P. Kirchner J. Seretsky

1974-01-01

154

Thermal imaging of subsurface microwave absorbers in dielectric materials  

Microsoft Academic Search

The use of microwaves as a heating source in time-resolved IR radiometry provides the ability to heat surface and subsurface microwave-absorbing regions of a specimen directly. This can improve the contrast and spatial resolution of such regions and enhance their detectibility when compared with conventional laser or flashlamp sources. The experiments reported here use microwave heating with IR detection. Results

Robert Osiander; Jane W. Spicer; John C. Murphy

1994-01-01

155

Radar cross-section study of cylindrical cavity-backed apertures with outer or inner material coating: the case of E-polarization  

Microsoft Academic Search

A dual-series-based solution is obtained for the scattering of an E-polarized plane wave from a cavity-backed aperture which is formed by a slitted infinite circular cylinder coated with absorbing material. The material coating can be done on the inner or outer surface of the cylinder. For both cases, numerical results are presented for the radar cross section and comparisons are

Dilek Colak; Alexander I. Nosich; Ayhan AltintaS

1993-01-01

156

Radar  

Microsoft Academic Search

Over 1,000,000 km2 of the equatorial surface of Mars west of the Arsia Mons volcano displays no 3.5-cm radar echo to the very low level of the radar system noise for the Very Large Array; the area displaying this unique property has been terms \\

James R. Zimbelman; Kenneth S. Edgett

1994-01-01

157

Characterization of porous construction materials using electromagnetic radar wave  

NASA Astrophysics Data System (ADS)

This thesis reports the effort of characterizing three porous construction materials (i.e. concrete, asphalt and soils) and the establishment and formulation of novel unified constitutive models by utilizing electromagnetic (EM) radar wave. An important outcome of this research is that the studied materials were assigned successfully into their rightful positions corresponding to the different regimes governed by three EM wave properties and two engineering/geological properties of the materials. The former refers to the real part of complex dielectric permittivity (epsilon'), energy attenuation and peak-frequency drift. The latter refers to porosity and permeability determined with forward models or conventional testing techniques. In soil and asphalt, the material characterization was achieved by a novel inhouse developed method called Cyclic Moisture Variation Technique (CMVT). The technique is termed cyclic because the porous materials were subjected to change from partially saturated states to fully saturated state (i.e. permeation), and vice versa (i.e. de-watering). With CMVT, water was used as an enhancer or a tracer to differentiate the studied materials which are otherwise difficult when they are dry. Soils and asphalt with different textures were characterized by different curve families exhibited in the relationship between epsilon' and degrees of water saturation (SW). In particular, these curve families were divided into three regions: slow-climbing region in very low SW, fast-climbing region in intermediate SW and another slow-climbing region at high S W. When data obtained from the permeation and de-watering cycles was compared, dielectric hysteresis was observed, but rarely reported in the field of ground penetrating radar (GPR). Different curing histories affect both porosity and pore size distribution within mature concrete. By injecting pressurized water into concrete specimens, different concrete curing histories was back-tracked through the curves in the plots between epsilon' and SW. In particular, the curves for air-cured concrete were very similar to those of soils, which implies that the pore systems between these two materials are rather similar. The presence of water has usually been considered undesirable in most GPR studies because it attenuates EM wave significantly. However, this research turned this drawback into a useful characterization technique of the porous construction materials.

Lai, Wallace Wai Lok

158

Non-self-absorbing materials for Luminescent Solar Concentrators (LSC)  

NASA Astrophysics Data System (ADS)

The diheptyl-bipyridyl-diol, as a non-self-absorbing fluorescent compound characterized by a large separation between absorption and fluorescence bands, has been incorporated in polyvinyl-butyral film. Steady state luminescence and lifetime were measured. An increase of luminescence intensity by about 34% in the presence of silver nanoparticles was observed. No appreciable changes were found in the corresponding lifetimes. The system is proposed as a potential candidate for increasing the LSC efficiency.

Saraidarov, T.; Levchenko, V.; Grabowska, A.; Borowicz, P.; Reisfeld, R.

2010-05-01

159

Solar absorber material stability under high solar flux  

Microsoft Academic Search

Solar absorbing Black Chrome coatings have been exposed to high temperatures (350-400 C) under high solar fluxes (0.4 to 2.0 MW\\/sq m) to test for their stability under actual operating conditions. Field tests at the White Sands Solar Furnace have shown higher stability than expected from oven tested samples. Laboratory studies utilizing spectrally selective concentrated solar simulated radiation have indicated

A. Ignatiev; G. Zajac; G. B. Smith

1982-01-01

160

Evaluation of the Sensitivity of Radar Cross Section Predictions to Uncertainties in Material Characteristics.  

National Technical Information Service (NTIS)

The purpose of this study was to evaluate the effects of material characteristics uncertainties on Radar Cross Section (RCS) predictions. Many methods have been developed to predict the RCS of metal objects, but for material coated objects, these methods ...

G. A. Barnhart

1995-01-01

161

A preliminary investigation into the nature of shock absorbency in synthetic sports materials.  

PubMed

Tests were conducted on three athletic shoe midsole materials and on three synthetic sports surfaces. All specimens were found to absorb energy when loaded. For a specific maximum load the amount of energy absorbed by each material was found to decrease as the load application rate increased. The materials exhibited different capacities to dissipate energy under the application of the same impulse. This may be a consideration for the injury protection afforded. The development of rheological models from the results of the tests aided an explanation of how force is resisted and energy absorbed by synthetic sports materials. Their shock absorbing properties were associated with the rheological elements of elasticity and viscosity. PMID:4094021

McCullagh, P J; Graham, I D

1985-01-01

162

RADAR REFLECTIVE MATERIAL FOR LOW OBSERVABILITY AND CAMOUFLAGE  

Microsoft Academic Search

In a modern battlefield, Radar has emerged as an important sensor for the detection and targeting of enemy military assets. In order to survive and maintain military effectiveness over a sustained period, it is crucial to ensure low-observability and camouflage of own war fighting resources. The frequency band of operation for most of the present day radar sensors is 8

Muhammad Tayyab Janjua; Jahangir Khan Kayani

163

On the usefulness of water absorbent materials in museum walls  

Microsoft Academic Search

Hygroscopic walls and ceilings give substantial stability to the indoor relative humidity (RH) in rooms which are ventilated at less than about one air change per hour. A few centimetres of material are sufficient to buffer the daily RH cycle, about 40 cm of wall will buffer the annual cycle of RH in a room with about 0.1 air changes

Tim Padfield

164

Absorber Materials for Transition-Edge Sensor X-ray Microcalorimeters  

Microsoft Academic Search

Arrays of superconducting transition-edge sensors (TES) can provide high spatial and energy resolution necessary for X-ray\\u000a astronomy. High quantum efficiency and uniformity of response can be achieved with a suitable absorber material, in which\\u000a absorber X-ray stopping power, heat capacity, and thermal conductivity are relevant parameters. Here we compare these parameters\\u000a for bismuth and gold. We have fabricated electroplated gold,

A.-D. Brown; S. R. Bandler; R. Brekosky; J. A. Chervenak; E. Figueroa-Feliciano; F. Finkbeiner; N. Iyomoto; R. L. Kelley; C. A. Kilbourne; F. S. Porter; S. Smith; T. Saab; J. Sadleir

2008-01-01

165

A new CMC-AA resin\\/inorganic-gel super absorbent material  

Microsoft Academic Search

A super absorbent material was prepared with the super absorbent resin (SAR) and inorganic gel. The SAR of the carboxymethyl\\u000a cellulose grafting acrylic acid (CMC-AA) was copolymer synthesized using the method of inversephase suspension polymerization.\\u000a The influences of the monomer concentration, neutralization degree, the initiator, dispersion agent, cross-linking agent,\\u000a reaction and drying temperature on the grafting copolymer properties were examined.

Wang Yong; Toshinori Kojima; Li Ming; Liu Jie

2006-01-01

166

Determining the Absorbance Spectra of Photochromic Materials From Measured Spectrophotometer Data  

NASA Technical Reports Server (NTRS)

If a two-state photochromic material is optically bleached, the absorbance spectrum data measured by a spectrophotometer is in general comprised of components from both the ground state and the upper state. Under general conditions, it may be difficult to extract the actual upper state spectrum from the spectrum of the bleached material. A simple algorithm is presented here for the recovery of the pure absorbance spectra of the upper state of a material such as bacteriorhodopsin, given single wavelength bleaching illumination, steady-state conditions, and accurate knowledge of phototransition rates and thermal decay rates.

Downie, John D.

1998-01-01

167

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

168

Development of a Weldable Neutron Absorbing Structural Material  

SciTech Connect

The National Spent Nuclear Fuel Program, located at the Idaho National Laboratory, coordinates and integrates national efforts in management and disposal of U.S. Department of Energy (DOE)-owned spent nuclear fuel. These management functions include development of standardized systems for packaging, storage, treatment, transport, and long-term disposal in the proposed Yucca Mountain Repository. Nuclear criticality control measures are needed in these systems to avoid restrictive fissile loading limits because of the enrichment and total quantity of fissile material in some types of the DOE spent nuclear fuel. This paper will outline the results to date of a metallurgical development program that is investigating the alloying of gadolinium into a nickel-chromium-molybdenum alloy matrix. Gadolinium has been chosen as the neutron absorption alloying element due to its high thermal neutron absorption cross section and low solubility in the expected repository environment. The nickel-chromium-molybdenum alloy family was chosen for its known corrosion performance, mechanical properties, and weldability. The workflow of this program includes chemical composition definition, primary melting and secondary refining studies, ingot conversion process evaluations, mechanical/physical properties and corrosion testing, welding studies, and national consensus codes, and standards work.

R. E. Mizia; W. L. Hurt; C. V. Robino; J. N. DuPont

2006-04-01

169

A ganglion cyst generated by non-absorbable meniscal repair suture material.  

PubMed

Arthroscopic meniscal repair has been a common procedure for the treatment of a torn meniscus, since the importance of meniscal preservation is widely understood. Over the years, the complications associated with suture material have been reported. Meniscal cyst is also one of those things. But ganglion cyst triggered by non-absorbable suture material was not documented in the literature. We report the case of a 19-year-old boy who underwent arthroscopic ACL reconstruction and repair of the medial meniscus by inside-out technique using 2-0 non-absorbable polyester sutures. The patient returned to our clinic at 4-year F/U with right knee pain due to medial meniscus tear and ganglion cyst. We suspect non-absorbable suture materials itself might have caused soft tissue irritation with repetitive trauma that lead to mucoid degeneration which results in ganglion cyst formation in the end. PMID:22858108

Kang, H J; Chun, C H; Kim, S H; Kim, K M

2012-09-01

170

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

171

Identification of Potential Photovoltaic Absorbers Based on First-Principles Spectroscopic Screening of Materials  

SciTech Connect

There are numerous inorganic materials that may qualify as good photovoltaic (PV) absorbers, except that the currently available selection principle - focusing on materials with a direct band gap of {approx}1.3 eV (the Shockley-Queisser criteria) - does not provide compelling design principles even for the initial material screening. Here we offer a calculable selection metric of 'spectroscopic limited maximum efficiency (SLME)' that can be used for initial screening based on intrinsic properties alone. It takes into account the band gap, the shape of absorption spectra, and the material-dependent nonradiative recombination losses. This is illustrated here via high-throughput first-principles quasiparticle calculations of SLME for {approx}260 generalized I{sub p}III{sub q}VI{sub r} chalcopyrite materials. It identifies over 20 high-SLME materials, including the best known as well as previously unrecognized PV absorbers.

Yu, L.; Zunger, A.

2012-02-10

172

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

173

Water Level Detection in Silty Materials Using Ground Penetrating Radar  

Microsoft Academic Search

Detection of water level in silty soils can be complicated because of capillary action. In this study, the water level in a silty soil sample was detected using Ground Penetrating Radar (GPR) technique in the laboratory. The soil sample has dimensions of 62 cm × 48 cm × 46 cm and was kept in a clear Plexiglas container which facilitated

Udaya B. Halabe; Hema J. Siriwardane; Sandeep Pyakurel; Ricardo Kiriakidis; Ronald Ingram

2007-01-01

174

Absorbent Material  

NASA Technical Reports Server (NTRS)

A superabsorbent fabric developed by Johnson Space Center and described in Tech Briefs was adapted by Honeywell and fabricated into special containment devices used on Navy "smart" torpedos. The superabsorbent fabric can sequester up to 400 times its own weight in water and protects the torpedo electronic controls from possible short circuiting by deepwater hull seepage.

1985-01-01

175

Evaluation of Frequency Characteristics of Absorbing Materials Using Time-Domain Single Antenna Method at Standard Site  

Microsoft Academic Search

Frequency characteristics of absorbing materials are evaluated in single-antenna calibration technique using a log- periodic antenna on a standard ground plane. The technique is applied to the data both in frequency- and time-domains, to evaluate the frequency characteristics of absorbing materials on the ground plane. Time-domain subtraction enables us to separate the wave reflected from absorbing materials. As a result,

Satoru Kurokawa; Masanobu Hirose; Koji Komiyama

2007-01-01

176

Site attenuation characteristics of anechoic chamber using foamed ferrite as new absorbing material  

Microsoft Academic Search

The anechoic chamber built in the Kyushu Institute of Technology in 1998 can be configured as a semi-anechoic chamber as well as a fully anechoic one in the frequency range of from 30 MHz to 10 GHz, having a thickness of about 10 cm by using a foamed ferrite as the new absorbing material. The normalized site attenuation (NSA) of

M. Tokuda; K. Simada; H. Ishii

1999-01-01

177

Numerical investigation of energy absorbers in composite materials for automotive applications  

Microsoft Academic Search

Nowadays, there is increasing interest in lightweight automotive structures capable of absorbing large quantities of energy in case of a crash phenomenon. These requirements are satisfied by composite devices, provided they are properly designed. The aim of the present paper is the investigation of the crashworthy behaviour of composite material tubes with woven laminae subjected to dynamic axial compression. The

Simonetta Boria; Giovanni Belingardi

2012-01-01

178

Test Methodologies for Determining Energy Absorbing Mechanisms of Automotive Composite Material Systems  

Microsoft Academic Search

To identify and quantify the energy absorbing mechanisms in automotive composite material systems, test methodologies were developed for conducting progressive crush tests on composite specimens that have simplified test geometries. The test method development focused on isolating the damage modes associated with the frond formation that occurs in dynamic testing of composite tubes. A new test fixture was designed to

J. Michael Starbuck; Srdan Simunovic; George Chennakattu Jacob

179

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

180

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

181

Design and measurement of a thin and light absorbing material for space applications  

NASA Astrophysics Data System (ADS)

This paper presents the design, realization and measurement of a thin lightweight absorbing material for space applications. Absorber design is based on high impedance surfaces loaded with resistors and known as a resistive high impedance surface (RHIS). The behavior of RHIS is analyzed at normal and oblique incidences for TE and TM polarizations. Prototypes have been realized and measured. Final design has a reflection coefficient less than 15 dB in S-Band (2-2.3 GHz) at normal incidence and till an angular dispersion of 40 for waves in TE polarization, and 35 for waves in TM polarization. Simulation results are validated by measurement.

Pinto, Yenny; Sarrazin, Julien; Lepage, Anne Claire; Begaud, Xavier; Capet, Nicolas

2014-05-01

182

Optimal estimation in an inverse problem arising in absorbance spectroscopy of geological materials  

NASA Astrophysics Data System (ADS)

We address the problem of unpolarised light spectroscopy of geological materials. Using infrared radiation, the aim of this technique is to learn about the absorbing species, such as hydroxl. The use of unoriented samples leads to the need for a proper statistical analysis to be performed, in order that the three principle absorbances of the crystal can be retrieved. We present here such an analysis based on a rigorous derivation of the probability density function for a single random measurement. Previous methods for retrieval of the absorbances are shown to be flawed, producing results that are either inconsistent (e.g. negative estimates for an inherently positive quantity) or biased. We show how this problem is rather subtle, in that it disallows the use of maximum likelihood as an estimation procedure. Instead we compare the empirical and theoretical cumulative density functions and optimise for the three required parameters. This leads to good parameter retrieval on either synthetic or real data sets.

Jackson, A.; Parker, R. L.; Sambridge, M.; Constable, C.

2013-12-01

183

Broadband transmission noise reduction of smart panels featuring piezoelectric shunt circuits and sound-absorbing material.  

PubMed

The possibility of a broadband noise reduction of piezoelectric smart panels is experimentally studied. A piezoelectric smart panel is basically a plate structure on which piezoelectric patches with electrical shunt circuits are mounted and sound-absorbing material is bonded on the surface of the structure. Sound-absorbing material can absorb the sound transmitted at the midfrequency region effectively while the use of piezoelectric shunt damping can reduce the transmission at resonance frequencies of the panel structure. To be able to reduce the sound transmission at low panel resonance frequencies, piezoelectric damping using the measured electrical impedance model is adopted. A resonant shunt circuit for piezoelectric shunt damping is composed of resistor and inductor in series, and they are determined by maximizing the dissipated energy through the circuit. The transmitted noise-reduction performance of smart panels is tested in an acoustic tunnel. The tunnel is a square cross-sectional tube and a loudspeaker is mounted at one side of the tube as a sound source. Panels are mounted in the middle of the tunnel and the transmitted sound pressure across panels is measured. When an absorbing material is bonded on a single plate, a remarkable transmitted noise reduction in the midfrequency region is observed except for the fundamental resonance frequency of the plate. By enabling the piezoelectric shunt damping, noise reduction is achieved at the resonance frequency as well. Piezoelectric smart panels incorporating passive absorbing material and piezoelectric shunt damping is a promising technology for noise reduction over a broadband of frequencies. PMID:12243188

Kim, Jaehwan; Lee, Joong-Kuen

2002-09-01

184

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

NASA Astrophysics Data System (ADS)

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 mechanical properties and energy-absorbing capabilities of the composite are studied for variations in design parameters including imposed field strength, volume fraction of the field-responsive fluid within the composite and impact strain rates. The total energy absorbed by these materials can be modulated by a factor of 1- to 50-fold for small volume fractions of the fluid (~15%) using moderate magnetic fields varying from 0 to 0.2 T. A scaling model is also proposed for the fluid-solid composite mechanical behavior that collapses experimental data onto a single master curve. The model allows optimization of the composite properties in tune with the application requirements. Potential application areas are discussed with emphasis on applicability in impact-absorbing headrests and cushioned assemblies for energy management.

Deshmukh, Suraj S.; McKinley, Gareth H.

2007-02-01

185

Surface wave sensors based on nanometric layers of strongly absorbing materials.  

PubMed

We demonstrate the excitation of guided modes in thin layers of strongly absorbing chalcogenide glasses. These modes are similar to surface plasmon polaritons in terms of resonance width and shift with changes in the permittivity of the surrounding medium. We exploit these characteristics to demonstrate a high sensitivity chalcogenide glass refractive index sensor that outperforms gold surface plasmon resonance sensors at short wavelengths in the visible. This demonstration opens a new range of possibilities for sensing using different materials. PMID:22535033

Zhang, Yichen; Arnold, Christophe; Offermans, Peter; Gómez Rivas, Jaime

2012-04-23

186

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

187

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

188

Measurement of the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field.  

PubMed

This letter proposes an experimental method to estimate the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field in free-field conditions. Comparisons are made between experiments conducted with this approach, the standard reverberant room method, and numerical simulations using the transfer matrix method. With a simple experimental setup and smaller samples than those required by standards, the results obtained with the proposed approach do not exhibit non-physical trends of the reverberant room method and provide absorption coefficients in good agreement with those obtained by simulations for a laterally infinite material. PMID:24993232

Robin, Olivier; Berry, Alain; Doutres, Olivier; Atalla, Noureddine

2014-07-01

189

Effects of excited-state absorption on two-photon absorbing materials  

SciTech Connect

Many chromophores with a large two-photon absorptive cross section are hybrid materials where the two-photon absorption (TPA) is coupled to an excited-state absorption (ESA). We develop a numerical technique to investigate hybrid two-photon processes in nonlinear absorbers. Our numerical method compares well with published results. In addition to customary calculation of the transmission curve, we demonstrate the importance of the ESA following the TPA, which may cause significant temporal and radial distortion. We also show that improvements in the transmission can result in significant radial and temporal pulse distortion, which may actually reduce the material effect.

Gao Yongwang; Potasek, Mary J

2006-04-10

190

Experimental investigation on ultra-wideband radar characteristics of coating RAM's targets  

NASA Astrophysics Data System (ADS)

A system of impulse radar is introduced, and results of an experimental investigation of a radar absorbing material (RAM) coating on the surface of metallic targets are presented. Their echo signal data are recorded, the impulse response of the targets is evaluated, and the energy of the scattering echo and the power spectral density are computed. It is shown that the ultrawideband radar is more capable than narrowband radars of mitigating the effects of RAM.

He, Jianguo; Lu, Zhongliang; Su, Yi

191

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.

192

Evaluation of polypropylene and poly (butylmethacrylate-co-hydroxyethylmethacrylate) nonwoven material as oil absorbent.  

PubMed

Polypropylene (PP) and poly(butylmethacrylate-co-hydroxyethylmethacrylate) (PBMA-co-HEMA) nonwoven materials as oil absorbents have been fabricated for the first time via melt blown method. As-prepared nonwovens were investigated in terms of mass per unit area, density, air permeability, contact angle, and morphology observations for fiber diameter distribution and single fiber surface by a field emission scanning electron microscope. The nonwovens are demonstrated as fast and efficient absorbents for various kinds of oils with oil absorbency up to seven to ten times their own weight. The nonwovens show excellent water repulsion but superoleophilic properties. The measured contact angles for water and toluene are more than 127° and ca. 0°, respectively. The addition of PBMA-co-HEMA makes the nonwoven surface more hydrophobic while conserving superoleophilicity. Compared with PP nonwoven, broad diameter distribution of the blend nonwoven is attributed to poor melt fluidity of PBMA-co-HEMA. In terms of single fiber, coarse surface and the presence of point-like convexities lead to the fibers being more readily wetted by oil. More interesting, oil-water separation and oil recovery can be easily carried out by filter and absorption-desorption process, the recovered materials contained hardly any oil droplet and could be reused for next cycles. PMID:23238599

Zhao, Jian; Xiao, Changfa; Xu, Naiku

2013-06-01

193

Materials for nonlinear optics: Semicontinuous gold films and fast saturable absorbers  

NASA Astrophysics Data System (ADS)

In this thesis I have investigated two types of materials that have the potentiality, in different ways, to contribute to practical applications of nonlinear optics: semicontinuous gold films and fast saturable absorbers. Metals have extremely high values of the third-order nonlinear optical susceptibility (they are approximately 106 times more nonlinear than silica) and a very fast response time (on the order of 2 ps); this high nonlinearity makes them attractive candidates for applications such as all-optical switching. On the other hand, as everyday experience teaches, they do not let light pass through. One way to make light penetrate more deeply into metals is mixing them with dielectrics. In particular in my thesis I have studied the nonlinear properties of collection of gold nanoparticles embedded into silica or deposited onto it. These nanoparticle systems possess special resonances, the "plasmon resonances", that are absent from either bulk metal or bulk dielectric but only arise when the two are combined at the nanoscale. In the linear optical response these resonances produce extinction bands that for gold in silica are situated in the visible. At the resonance wavelength the electric field is concentrated inside the nanoparticles, and this field concentration produces an enhanced nonlinear optical response. In my work I have experimentally characterized the nonlinear absorption in these kind of samples over a wide range of composition and wavelength, and have proposed an explanation for the fact that under certain conditions these materials are saturable absorbers while gold itself is an optical limiter. A separate part of my work has examined the use of fast saturable absorbers to slow down light using the mechanism of coherent population oscillations. Using quantum dots as saturable absorbers I have demonstrated the slow propagation of pulses of ? 30 Ps duration.

Piredda, Giovanni

194

Method and apparatus for determining the content and distribution of a thermal neutron absorbing material in an object  

DOEpatents

The disclosure is directed to an apparatus and method for determining the content and distribution of a thermal neutron absorbing material within an object. Neutrons having an energy higher than thermal neutrons are generated and thermalized. The thermal neutrons are detected and counted. The object is placed between the neutron generator and the neutron detector. The reduction in the neutron flux corresponds to the amount of thermal neutron absorbing material in the object. The object is advanced past the neutron generator and neutron detector to obtain neutron flux data for each segment of the object. The object may comprise a space reactor heat pipe and the thermal neutron absorbing material may comprise lithium.

Crane, Thomas W. (Los Alamos, NM) [Los Alamos, NM

1986-01-01

195

Method and apparatus for determining the content and distribution of a thermal neutron absorbing material in an object  

DOEpatents

The disclosure is directed to an apparatus and method for determining the content and distribution of a thermal neutron absorbing material within an object. Neutrons having an energy higher than thermal neutrons are generated and thermalized. The thermal neutrons are detected and counted. The object is placed between the neutron generator and the neutron detector. The reduction in the neutron flux corresponds to the amount of thermal neutron absorbing material in the object. The object is advanced past the neutron generator and neutron detector to obtain neutron flux data for each segment of the object. The object may comprise a space reactor heat pipe and the thermal neutron absorbing material may comprise lithium.

Crane, T.W.

1983-12-21

196

Absorb & Repel  

NSDL National Science Digital Library

In this activity, learners investigate how different materials repel or absorb water. Learners use spray bottles to explore how everyday items like sponges, cardboard, feathers, etc. respond to water differently. This activity also introduces learners to the scientific method as learners make predictions about which materials will absorb or repel water.

Museum, Kohl C.

2012-01-01

197

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

198

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

199

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

200

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

201

Mars: electric properties of clay materials in martian-like conditions to refine radar investigation.  

NASA Astrophysics Data System (ADS)

The orbital radar instruments are giving new opportunities for planetary geological investigation regarding subsurface layering and geometry. Sedimentary deposits of paleolacustrine environments on Mars have shown the presence of various clay minerals . These clay deposits are very important in planetary exploration because they are strictly linked to the presence of water and to the capability of the analyzed environment to develop life and, as a consequence, to preserve fossilized life marker. The subsurface stratigraphy and geometry of sedimentary deposits on Mars are investigated by two orbiting radar instruments (SHARAD and MARSIS) and in the next future another radar instrument, a landing one, will be send on Mars (WISDOM). For small grain size sediments, like clay minerals, the dielectric properties have a strong impact on the penetration depth of the radar signal. We studied the correct evaluation of these properties and their correlation with chemical and mineralogical phases. The focus of this research is on the dielectric properties of natural clayey materials at different frequencies and temperature, evaluating the correlation among water content , temperature and electric properties. Several natural clayey material samples, considered as analogues to the Martian ones, have been collected from different geological settings in Italy and we analyzed their water content, mineralogical assemblage and chemical content and the correlation with the permittivity at different frequencies and temperatures using the Network Analyzer technique. We also changed the water content of the samples, and using the SHARAD, MARSIS and WISDOM operating frequencies, we measured the variation of permittivity and electric properties in the thermal range of 180 K to 298 K. The goal of the study is to refine the sounding depths of the radar investigation on Mars, exploring the possibility to identify clayey sedimentary layers analyzing the differences between the electric properties of these loose materials and the surrounding rock ones.

Colantuono, Luca; Baliva, Antonio; Lauro, Sebastian; Mattei, Elisabetta; Marinangeli, Lucia; Pettinelli, Elena; Seu, Roberto

2014-05-01

202

Generalized-material-independent PML absorbers used for the FDTD simulation of electromagnetic waves in 3-D arbitrary anisotropic dielectric and magnetic media  

Microsoft Academic Search

By introducing the material-independent quantities (electric displacement D and flux density B) into the finite-difference time-domain (FDTD) model, a generalized-material-independent perfectly matched layer (GMIPML) absorber used to absorb electromagnetic waves propagating in three-dimensional (3-D) general anisotropic dielectric and magnetic media is proposed. Within the proposed GMIPML absorber, D and B are directly absorbed, whereas E and H are simultaneously absorbed

An Ping Zhao

1998-01-01

203

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

204

A Doppler Radar for Measuring Irregularities in Rolled Sheet Material  

Microsoft Academic Search

This 9-Gc system used a microwave signal reflected from the surface of a rotating roll of paper or plastic film to detect irregularities in the outer layers of the rolled material. The microwave package comprised a klystron oscillator, silicon dector crystal, and flared wave-guide horn antenna. A standard laboratory oscilloscope was used as the ``receiver'' and display system. Examples of

Frank G. Alexander

1963-01-01

205

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

206

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

207

Simulation on photoacoustic conversion efficiency of optical fiber-based ultrasound generator using different absorbing film materials  

NASA Astrophysics Data System (ADS)

The low energy-conversion efficiency in photoacoustic generation is the most critical hurdle preventing its wide applications. In recent studies, it was found that the selection of the energy-absorbing layer material and design of the acoustic generator structure both determine the photoacoustic conversion efficiency. The selection of the absorbing material is based on its optical, thermal, and mechanical properties. In this research, we calculated and compared the conversion efficiencies of six different absorbing film materials: bulk aluminum, bulk gold, graphite foil, graphite powder-resin mixture, gold nanospheres, and gold nanorods. The calculations were carried out by a finite element modeling (FEM) software, COMSOL Multiphysics. A 2D-axisymmetric model in COMSOL was built up to simulate a 3-layer structure: optical fiber tip, light absorbing film, and surrounding water. Three equations governed the thermo-elastic generation of ultrasonic waves: the heat conduction, thermal expansion and acoustic wave equations. In "thick-film" generation regime, majority of the laser energy is absorbed by the film and converted to high-frequency film vibration, and the vibration excites the ultrasound wave in the adjacent water, while the water would not be heated directly by the laser. From the results of this FEM simulation, the acoustic signal generated by gold nanosphere (or nanorod) film is over two times stronger than that generated by graphite powder-resin film of the same thickness. This simulation provides a strong support to the absorbing material selection for our proposed fiber ultrasound generator.

Sun, Kai; Wu, Nan; Tian, Ye; Wang, Xingwei

2011-03-01

208

Evaluation of tensile strength of surgical synthetic absorbable suture materials: an in vitro study  

PubMed Central

Purpose The purpose of this study was to evaluate the tensile strength of surgical synthetic absorbable sutures over a period of 14 days under simulated oral conditions. Methods Three suture materials (polyglycolic acid [PGA], polyglactin [PG] 910, and poly (glycolide-co-?-caprolactone) [PGC]) were used in 4-0 and 5-0 gauges. 210 suture samples (35 of each material and gauge) were used. All of the samples were tested preimmersion and 1 hour and 1, 3, 7, 10, and 14 days postimmersion. The tensile strength of each suture material and gauge was assessed. The point of breakage and the resorption pattern of the sutures were also assessed. Results During the first 24 hours of immersion, all 4-0 and 5-0 samples of PGA, PG 910, and PGC maintained their initial tensile strength. At baseline (preimmersion), there was a statistically significant (P<0.001) difference in the tensile strengths between the 4-0 and 5-0 gauge of PGA, PG 910, and PGC. PGA 4-0 showed the highest tensile strength until day 10. At 7 days, all the 4-0 sutures of the three materials had maintained their tensile strength with PGA 4-0 having significantly greater (P=0.003) tensile strength compared to PG. Conclusions 4-0 sutures are stronger and have greater tensile strength than 5-0 sutures. The PGA 4-0 suture showed the highest tensile strength at the end of day 10.

Ranganath, V.; Nichani, Ashish Sham

2013-01-01

209

Radioabsorbing Material Optimal Using in the Reduction of Aircraft Radar Cross-Section.  

National Technical Information Service (NTIS)

Local scattering parts on a smooth convex object elements make the most important contribution to reflected signal energy. So these surface parts of complex shape objects are coated by radio-absorbing materials (RM) in camouflage purpose. As a rule, the r...

V. A. Vasilets S. A. Gorelyshev K. I. Tkachuk

2002-01-01

210

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

211

Radar target signature program performance specification  

NASA Astrophysics Data System (ADS)

This report is a Program Performance Specification (PPS) for a digital computer program that calculates the radar signatures of ships. The PPS will be used to guide the program through three development phases and acceptance testing. The primary objectives of the program are accuracy, flexibility of application, ease of modeling, and portability. The ship is modeled by identifying and defining all the geometrical shapes which cause radar scattering and coherently adding the signals from all the appropriate ones. The program will handle far-field, near-field, and bistatic geometries, antenna patterns, radar absorbing material, and high range resolution effects.

Toothman, H. L.

1981-06-01

212

Electromagnetic Design and Realization of Innovative Fiber-Reinforced Broad-Band Absorbing Screens  

Microsoft Academic Search

This paper presents the design and the realization process for radar absorbing panels made of composite materials. It is demonstrated that the proper selection of the carbon fiber length and volume fraction allows reducing sensibly the overall thickness of the screen compared to a standard absorber, and obtaining at the same time broad-band absorption response in the X- and Ku-bands.

Igor Maria De Rosa; Riccardo Mancinelli; Fabrizio Sarasini; Maria Sabrina Sarto; Alessio Tamburrano

2009-01-01

213

Analysis of the efficiency of radiation absorbing material at X-band by measurement of RCS of planes and cylinder in open field  

Microsoft Academic Search

This paper presents an analysis of the measurements of the electromagnetic scattering in open field at the frequency of 8.76 GHz through the radar cross section (RCS) in the bi-static condition. Three structures have been investigated: a plane plate, a dihedral angle of 95°, and a metallic massive cylinder, in all cases before and after application of the multilayer absorbing

S. M. L. da Silva; A. J. de Faro Orlando; M. C. Rezende

2005-01-01

214

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

215

Experimental investigation on ultra-wideband radar characteristics of coating RAM's targets  

Microsoft Academic Search

A system of impulse radar is introduced, and results of an experimental investigation of a radar absorbing material (RAM) coating on the surface of metallic targets are presented. Their echo signal data are recorded, the impulse response of the targets is evaluated, and the energy of the scattering echo and the power spectral density are computed. It is shown that

Jianguo He; Zhongliang Lu; Yi Su

1992-01-01

216

Radar cross section reduction of a flat plate by ram coating  

Microsoft Academic Search

The problem of reduction of radar cross section (RCS) of a flat plate coated with a radar absorbing material has been examined using the uniform asymptotic theory of diffraction. The variation and reduction of RCS with different parameters have been studied and theoretical results have been compared with the experiment and the spectral Galerkin method.

Asoke K. Bhattacharyya

1990-01-01

217

Comparison of absorbed dose in bone substitute material and water using ionization measurements  

Microsoft Academic Search

Absorbed dose in a liquid substitute for bone has been compared with absorbed dose in water for 9-, 12-, and 15-MeV electron beams using ionization chamber measurements. The ionization readings were converted to dose using collisional mass stopping power ratios. The collisional mass stopping powers for the liquid substitute of bone were calculated using the Monte Carlo Code PEGS4. The

Satish C. Prasad; D. A. Bassano

1989-01-01

218

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

219

Long-lived platinum(II) diimine complexes with broadband excited-state absorption: efficient nonlinear absorbing materials.  

PubMed

Platinum(II) diimine complexes with naphthalimide substituted fluorenylacetylide ligands are synthesized and characterized. The complexes exhibit long-lived (3)ILCT or (3)ILCT/(3)MLCT/(3)LLCT excited states (? = ~20-30 ?s) and broadband triplet transient absorption in the visible-NIR region. Nonlinear transmission experiments at 532 nm demonstrate that these complexes are efficient nonlinear absorbing materials. PMID:22972235

Liu, Rui; Azenkeng, Alexander; Li, Yuhao; Sun, Wenfang

2012-10-28

220

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

221

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

222

Development of Shock Absorbing Barrier Materials for High Performance Magazine Construction.  

National Technical Information Service (NTIS)

To prevent sympathetic detonation in a high performance magazine, barriers between stacks of munitions absorb donor fragments. Acceptor munitions may still initiate on impact of barrier debris or on being thrown into the walls of the magazine itself. Thes...

C. Herzfeld S. Wise

1994-01-01

223

Resolution function of nonsinusoidal radar signals. I - Range-velocity resolution with rectangular pulses  

NASA Astrophysics Data System (ADS)

A generalization of a previously published ambiguity function that applies to radar known as large-relative-bandwidth radar, carrier-free radar, impulse radar, or nonsinusoidal radar is discussed. This radar has recently attracted attention because of its ability to penetrate absorbing materials used in the stealth technology. Another good application is the detection of moving targets with a small radar cross section by a look-down radar, which calls for a thumbtack ambiguity function. Since a small radar cross section in this application is typically due to the small size of the target that is coated with absorbing material, the antistealth feature of the nonsinusoidal radar is implicitly being used. The principle is presented of a resolution function (tentatively called the range-velocity or the range-Doppler resolution function) based on processing a nonsinusoidal signal consisting of N characters with a time separation TD and each character consisting of a sequence of L binary pulses of duration T. It is shown that range-velocity resolution functions approaching the ideal thumbtack function are easy to obtain. The blind speeds of the pulse-Doppler radar with sinusoidal carrier do not inherently occur, and all velocities are observed as true velocities rather than as velocities modulo the first blind speed (velocity ambiguity).

Mohamed, Nasser J.

1990-05-01

224

HIGH IMPEDANCE GROUND PLANE (HIGP) INCORPORATED WITH RESISTANCE FOR RADAR CROSS SECTION (RCS) REDUCTION OF ANTENNA  

Microsoft Academic Search

In this paper a novel ultra-thin radar absorbent material (RAM) using HIGP is presented and investigated. Owing to the high impedance property of the HIGP, the thickness of the RAM is about several tenths of the centre wavelengthof the absorption band, considerably thinner than conventional absorbers. The absorption band of the RAM is about several hundred megahertz. In the new

Qiu-Rong Zheng; You-Ming Yan; Xiang-Yu Cao; Nai-Chang Yuan

2008-01-01

225

Updating 3D acoustic models with the constitutive relation error method: A two-stage approach for absorbing material characterization  

NASA Astrophysics Data System (ADS)

In the global framework of improving vibro-acoustic numerical simulations together with the need to decrease the number of prototyping stages, improving the quality for acoustic models becomes increasingly important for many industries such as automotive companies, for instance. This paper focuses on achieving greater accuracy for acoustic numerical simulations by making use of a parametric updating technique, which enables tuning the model parameters inside physically meaningful boundaries. The improved model is used for the next prototyping stages, allowing more accurate results within reduced simulation times. The updating technique used in this paper is based on recent works dealing with the constitutive relation error (CRE) method applied to acoustics. The updating process focuses on improving the acoustic damping matrix related to the absorbing properties of the materials covering the borders of the acoustic domain. The present study proposes a 2-stage optimization process, which exhibits many advantages. Indeed, the computational time decreases, the frequency interpolation of the material absorbing properties outside the studied frequency range is easily performed, and comparing the correlation of several material absorbing constitutive equations with experimental records is fast. Additional originality of the work comes with the application of the CRE updating method to a concrete real-life device, while previous works addressed purely numerical setups without experimental data. The test-case is the TRICARMO setup engineered by LMS International in Leuven, Belgium. The TRICARMO setup is a simplified car cabin with rigid walls and car seats inside. Thanks to the 2-stage approach, the material property characterization of the seat is improved by running the updating simulation process using a physical absorbing material model.

Decouvreur, V.; Ladevèze, P.; Bouillard, Ph.

2008-03-01

226

YPMA-01 non-contacting radar level meter for hydrocarbon materials and products of their processing stored in tanks  

Microsoft Academic Search

According to the order from OAO Gazprom, a radar level meter was developed for hydrocarbon materials and commercial products in tanks of a height up to 20 meters with a fixed roof or a floating cover. As a level meter YPMA-01 is designed for operation within control and data acquisition systems using an RS-485 interface. Site tests are at the

Yu. I. Orekhov; A. A. Rybalchenko; S. V. Katin; G. G. Bakhirev; V. S. Tensin; N. B. Remizov

2001-01-01

227

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

228

Effective-medium model dependence of the radar reflectivity of conducting particle films  

Microsoft Academic Search

We present a numerical study of the frequency dependent, complex effective permittivity ? for a composite material which consists of lossy graphite-type microsphere inclusions randomly imbedded in a dielectric matrix, with a view towards assessing the suitability of such a composite for its use as a radar absorbing material (RAM). This suitability is determined by the material possessing a large

Aleksandr J. Stoyanov; Barbara F. Howell; Eugene C. Fischer; Herbert Überall; Khalid Chouffani

1999-01-01

229

Effective-medium model dependence of the radar reflectivity of conducting particle films  

Microsoft Academic Search

We present a numerical study of the frequency dependent, complex effective permittivity &egr; for a composite material which consists of lossy graphite-type microsphere inclusions randomly imbedded in a dielectric matrix, with a view towards assessing the suitability of such a composite for its use as a radar absorbing material (RAM). This suitability is determined by the material possessing a large

Aleksandr J. Stoyanov; Barbara F. Howell; Eugene C. Fischer; Khalid Chouffani

1999-01-01

230

Titan's surface inventory of organic materials estimated from Cassini RADAR observations  

NASA Astrophysics Data System (ADS)

Cassini RADAR observations now permit an initial assessment of the inventory of two classes, presumed to be organic, of Titan surface materials: polar lake liquids and equatorial dune sands. Several hundred lakes or seas have been observed, of which dozens are each estimated to contain more hydrocarbon liquid than the entire known oil and gas reserves on Earth. Dark dunes cover some 20% of Titan's surface, and comprise a volume of material several hundred times larger than Earth's coal reserves. Overall, however, the identified surface inventories (> 3 × 104 km3 of liquid, and >2 × 105 km3 of dune sands) are small compared with estimated photochemical production on Titan over the age of the Solar System. The sand volume is too large to be accounted for simply by erosion in observed river channels or ejecta from observed impact craters. The lakes are adequate in extent to buffer atmospheric methane against photolysis in the short term, but do not contain enough methane to sustain the atmosphere over geologic time. Thus, unless frequent resupply from the interior buffers this greenhouse gas at exactly the right rate, dramatic climate change on Titan is likely in its past, present and future.

Lorenz, Ralph D.

2008-10-01

231

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

232

Comparison Study of the Use of Absorbable and Nonabsorbable Materials as Internal Splints after Closed Reduction for Nasal Bone Fracture  

PubMed Central

Background The authors sought to compare the use of the nonabsorbable polyvinyl alcohol sponge (PVA, Merocel) and absorbable synthetic polyurethane foam (SPF, Nasopore Forte plus) as intranasal splints after closed reduction of fractured nasal bones during the hospitalization period. Methods The medical records of 111 patients who underwent closed reduction for nasal bone fracture at Sanggye Paik Hospital, Inje University College of Medicine, from 2012 to 2013 were reviewed retrospectively. PVA (group A) or SPF (group B) was packed as an internal splint after closed reduction. The efficacy of the materials was compared and statistically analyzed. Results PVA was used in 82 patients, and SPF was used in 29 patients. The patients in group B complained significantly more of nasal pain on the first day after operation than the patients in group A. Headaches on the operation day were significantly more painful in group B than in group A. Bleeding on the fourth postoperative day was significantly reduced in group B as compared to group A. The patients in group B exhibited significantly more intensive nasal obstruction on the operation day and the following day than the patients in group A. However, on the third and fourth postoperative days, the nasal obstruction in group B was less than that in group A. The pain and bleeding related to the packing material was significantly reduced in group B as compared to group A. Conclusions The use of SPF as an absorbable packing material is a reasonable substitute for the traditional nonabsorbable material.

Yi, Chang Ryul; Kim, Hoon; Nam, Sang Hyun; Choi, Young Woong

2014-01-01

233

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

Microsoft Academic Search

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

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

2007-01-01

234

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

235

New Visible Light Absorbing Materials for Solar Fuels, Ga(Sbx )N1-x.  

PubMed

A novel visible-light-absorbing dilute alloy, Ga(Sbx )N1-x is synthesized by metal organic chemical vapor deposition (MOCVD) for solar hydrogen production. Significant bandgap reduction of GaN, from 3.4 eV to 1.8 eV, is observed, with a low (2%) incorporation of antimonide, and the lattice expansion is in agreement with our first-principles calculations. The band edges of Ga(Sbx )N1-x are found to straddle the water redox potentials showing excellent suitability for solar water splitting. PMID:24536005

Sunkara, Swathi; Vendra, Venkat Kalyan; Jasinski, Jacek Bogdan; Deutsch, Todd; Andriotis, Antonis N; Rajan, Krishna; Menon, Madhu; Sunkara, Mahendra

2014-05-01

236

Cr4+-doped garnets: their properties as laser materials and nonlinear absorbers  

NASA Astrophysics Data System (ADS)

A comparative research into the use of Cr4+-doped YAG, YSGG, and LuAG (Lu3Al5O12) as saturable absorbers for the 1.06 micrometer emission of Nd:YAG laser has been conducted. Q-switched pulses with temporal duration ranging from 52 to 23 nsec (FWHM) were observed for the different garnets under investigation. Cross-sections for ground state and excited state absorption were evaluated by fitting our saturation data to Frantz-Nodvik equation. A brief discussion on the use of Cr4+ as a tunable mid-IR laser also is presented.

Kalisky, Yehoshua Y.; Ben-Amar Baranga, Andrei; Shimony, Yehoshua; Burshtein, Zeev; Pollack, S. A.; Kokta, Milan R.

1996-03-01

237

Open Reduction of Proximal Interphalangeal Fracture-Dislocation through a Midlateral Incision Using Absorbable Suture Materials  

PubMed Central

Background Fracture-dislocation of the proximal interphalangeal (PIP) joint is a relatively common injury. Various treatments for fracture-dislocation of the PIP joint have been reported. In the present study, we performed open reduction through a midlateral incision using absorbable sutures to reduce the small bone fragments and performed volar plate repair. Methods We treated nine patients with fracture-dislocation of the PIP joint with small fractured bone fragments too small for pinning or screw fixation. Patients with volar plate injury were treated with open reduction and volar plate repair at the periosteum of the middle phalangeal bone base by the modified Kessler method using absorbable sutures. All patients were placed in a dorsal aluminum extension block splint, which maintained the PIP joint in approximately 30 degrees of flexion to avoid excessive tension on the sutured volar plate. Results At a mean final follow-up of postoperative 9 months, all patients were evaluated radiographically and had adequate alignment of the PIP joint and reduction of the displaced bone fragments. Range of motion was improved and there were no complications. Conclusions This technique is an excellent alternative to the current method of treating patients with fracture-dislocations that include small fragments that are too small for pinning or screw fixation. It is a less invasive surgical method and enables stable reduction and early exercise without noticeable complications.

Lee, Jae Jun; Choi, Hyun Gon; Shin, Dong Hyeok; Uhm, Ki Il

2013-01-01

238

Development of High Band Gap Absorber and Buffer Materials for Thin Film Solar Cell Applications  

NASA Astrophysics Data System (ADS)

CuInGaSe2 (CIGS) device efficiencies are the highest of the thin film absorber materials (vs. CdTe, alpha-Si, CuInSe2). However, the band gap of the highest efficiency CIGS cells deviates from the expected ideal value predicted by models [1]. Widening the band gap to the theoretically ideal value is one way to increase cell efficiencies. Widening the band gap can be accomplished in two ways; by finding a solution to the Ga-related defects which limit the open circuit voltage at high Ga ratios, or by utilizing different elemental combinations to form an alternative high band gap photoactive Cu-chalcopyrite (which includes any combination of the cations Cu, Al, Ga, and In along with the anions S, Se, and Te). This thesis focuses on the second option, substituting aluminum for gallium in the chalcopyrite lattice to form a CuInAlSe2 (CIAS) film using a sputtering and selenization approach. Both sequential and co-sputtering of metal precursors is performed. Indium was found to be very mobile during both sputtering processes, with a tendency to diffuse to the film surface even when deposited as the base layer in a sequential sputtering process. Elemental diffusion was controlled to a degree using thicker Cu top layer in co-sputtering. The greater thermal conductivity of stainless steel foil (16 W/mK) vs. glass (0.9-1.3 W/mK) can also be used to limit indium diffusion, by keeping the substrate cooler during sputtering. In both sputtering methods aluminum is deposited oxygen-free by capping the film with a Cu capping layer in combination with controlling the indium diffusion. Selenization of metal precursor films is completed using two different techniques. The first is a thermal evaporation approach from a heated box source (method 1 -- reactive thermal evaporation (RTE-Se)). The second is batch selenization using a heated tube furnace (method 2 -- batch selenization). Some batch selenized precursors were capped with ˜ 1mum of selenium. In both selenization methods elemental selenium is used at the selenium source. In method 1 films selenized above 500°C showed low Al incorporation and phase separation. Films selenized with a Se depositional rate of 12 A/s showed poor adhesion compared to samples selenized at 4 A/s. Segregation of aluminum towards the back contact as well as oxygen incorporation appears to cause adhesion loss in extreme cases, and poor interface electrical characteristics in others. The maximum device efficiency measured for method 1 was 5.2% under AM1.5 for a device with ˜ 2 at. % aluminum. For method 2, samples deposited on glass demonstrated poor adhesion and similar attributes to the RTE-Se samples. No improvements were seen with the additional Se capping layer on the film. Metal foil samples show improved adhesion vs. glass samples deposited under the same conditions. Samples still showed oxidation of aluminum at the Mo interface. Increasing the temperature to 550°C resulted in the loss of Mo adhesion due to excessive MoSe 2 formation. Samples selenized for 90 minutes at 520°C showed decreased adhesion compared to those selenized for 40 minutes. Again excess MoSe 2 growth was seen, though not to the extent of the samples selenized at 550°C. The effective heat of formation model suggests the low Al incorporation found in all films is due the favorable formation of InSe vs. In2Se3. It predicts InSe will form first at the growing film interface, and this phase is then consumed in the formation of CuInSe2 at temperatures above 220°C. This results in the consumption of In before the (Al,In)2Se 3 phase can form, and therefore minimal formation of the CuInAlSe 2 chalcopyrite phase. Due to minimal (Al,In)2Se3 formation, free Al is able to react with H2O or form Al2Se 3 which is also able to react with H2O. Both reactions result in the formation of Al2O3 and H2Se. This Al2O3 forms a resistive barrier at the back contact, which results in loss of adhesion in high Al films, and an I-V "roll-over" effect in low Al devices. In addition to CIAS studies, a study of alternative buffer layers to chemical b

Dwyer, Dan

239

Composition for absorbing hydrogen  

DOEpatents

A hydrogen absorbing composition is described. 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, L.K.; Wicks, G.G.; Enz, G.L.

1995-05-02

240

Ground penetrating radar antenna system analysis for prediction of earth material properties  

USGS Publications Warehouse

The electrical properties of the ground directly beneath a ground penetrating radar (GPR) antenna very close to the earth's surface (ground-coupled) must be known in order to predict the antenna response. In order to investigate changing antenna response with varying ground properties, a series of finite difference time domain (FDTD) simulations were made for a bi-static (fixed horizontal offset between transmitting and receiving antennas) antenna array over a homogeneous ground. We examine the viability of using an inversion algorithm based on the simulated received waveforms to estimate the material properties of the earth near the antennas. Our analysis shows that, for a constant antenna height above the earth, the amplitude of certain frequencies in the received signal can be used to invert for the permittivity and conductivity of the ground. Once the antenna response is known, then the wave field near the antenna can be determined and sharper images of the subsurface near the antenna can be made. ?? 2005 IEEE.

Oden, C. P.; Wright, D. L.; Powers, M. H.; Olhoeft, G.

2005-01-01

241

Superabsorbent Multilayer Fabric: Material contains gel-forming polymer and copolymer that absorb from 70 to 200 times their weight of liquid.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. Solving the problem of waste disposal for astronauts has led to work on a superabsorbent multilayer fabric. The fabric contains gel-forming materials that absorb man...

1982-01-01

242

The Interaction Between a Beam and a Layer of Microwave-Absorbing Material  

NASA Astrophysics Data System (ADS)

A phased luminosity upgrade of the CESR electron -positron storage ring is in progress. The upgrade program calls for the installation of superconducting radio-frequency (RF) cavities with strongly damped higher-order modes (HOMs). The cavity is designed to allow all HOMs to propagate into the beam pipe, where they are damped by a layer of microwave -absorbing ferrite. RF measurements with a copper cavity and loads made of a nickel-zinc ferrite indicate that the design gives adequate HOM damping. Because the absorbing layer is on the beam pipe, there is a direct parasitic interaction with the beam. To quantify this parasitic interaction, the complex permeability and complex permittivity of the ferrite were measured as a function of frequency. These results were used to predict the beam coupling impedance of the ferrite loads via numerical and analytic techniques. The predictive methods were checked using the pulse-on-a-wire method for measuring the coupling impedance. Beam stability predictions based on the calculated impedance indicate that there should be no beam instabilities due to the direct interaction between the beam and the ferrite layer for a 183-bunch beam with a total current of 2 A per beam. The average power dissipation in the ferrite, including both direct and indirect power transfer from the beam, is predicted to be 82 W/cm^2 with 2 A per beam. To test the predictions, beam measurements were done in CESR on a ferrite load of magnified coupling impedance. The beam-induced power dissipation in the ferrite layer was within a factor of 2 of the predicted value. It was difficult to see an effect on the beam due to the presence of the ferrite, a result that is consistent with our present understanding.

Hartung, Walter H.

243

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

Microsoft Academic Search

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

Chaoguang Zhou; Lanbo Liu

2001-01-01

244

The Effect of Temperature on the Dynamic Impact Characteristics of Energy Absorbing Materials  

Microsoft Academic Search

A variety of different materials have been considered and implemented for occupant protection in automotive head impact countermeasures since the beginning of the five-year phase of FMVSS 201 (Upper) on September 1, 1998. Polyurethane foam has been the material of choice because of its good performance, ability to maintain properties across a wide range of temperature conditions, reasonable cost, and

David J. Lovell; Michael L. Kerman; Richard C. Allen; John W. Liddle

2004-01-01

245

Evaluation of Effective Diffusion Coefficient in Various Building Materials and Absorbents by Mercury Intrusion Porosimetry  

Microsoft Academic Search

An effective diffusion coefficient plays an important role in the numerical analysis model to predict the emission rate of VOCs from building materials. This research evaluates the effective diffusion coefficient of VOCs (toluene, formaldehyde, etc.) in building materials (gypsum boards, medium density fiberboard, etc.) and adsorbents (activated carbon, charcoal, etc.) using the mercury intrusion porosimetry (MIP) test. The MIP test

J Seo; S Kato; Y Ataka; Q Zhu

2005-01-01

246

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

247

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

Microsoft Academic Search

The electromagnetic backscattering of a crosscut of a cruise missile coated by a thin ho- mogeneous layer made of radar absorbent material is modeled using a nite element method. Based on the radar cross section and a reection coecien t, optimization problems are for- mulated for evaders and interrogators leading to optimal material parameters for the coating and optimal monostatic

K. Ito; J. Toivanen

248

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

249

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

250

Optimisation of the electromagnetic matching of manganese dioxide/multi-wall carbon nanotube composites as dielectric microwave-absorbing materials  

NASA Astrophysics Data System (ADS)

An optimised composite sample was prepared using two dielectric materials manganese dioxide (MnO2) and multi-wall carbon nanotubes (MWNTs) in an epoxy-resin matrix. Structural characterisations of both the synthesised manganese dioxide (MnO2) and the multi-wall carbon nanotubes (MWNTs) were performed by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microwave absorption properties of dielectric composites with different weight fractions of MnO2 were investigated by measuring the complex permittivity, the complex permeability and the reflection loss in the 2-18 and 18-40 GHz microwave frequency ranges using the free space method. The complex permittivity varied with the MnO2 content, and the results show that a high concentration of fillers increased the dielectric constant. Therefore, the appropriate combination of components and experimental conditions can produce materials with specific characteristic for use as wide-band microwave absorbers.

Ting, Tzu-Hao; Chiang, Chih-Chia; Lin, Po-Chuan; Lin, Chia-Huei

2013-08-01

251

Cr 4+ doped garnets: novel laser materials and non-linear saturable absorbers  

NASA Astrophysics Data System (ADS)

The use of the spectral properties of Cr 4+-doped garnets as passive Q-switches for 1.06 ?m laser for both pulsed and CW operating modes is addressed. A comparative research into the use of Cr 4+-doped YAG, YSGG, and LuAG (Lu 3Al 5O 12) as saturable absorbers for the 1.06 ?m emission of Nd:YAG laser has been conducted. Q-switched pulses with temporal duration ranging from 52 to 23 ns (FWHM) were observed for the different garnets under investigation. Cross-sections for ground state and excited state absorptions were evaluated by fitting our saturation data to Frantz-Nodvik equation. A complete analysis of the saturation transmission curves will be presented. The laser performance of Cr 4+: YAG and Cr 4+:LuAG (Lu 3Al 5O 12) lasing in the mid-IR (1.35-1.55 ?m) pumped by the 1064 nm of Nd:YAG will also be reported.

Kalisky, Y.; Ben-Amar Baranga, A.; Shimony, Y.; Kokta, M. R.

1997-07-01

252

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

253

Identification of Superior Energy-Absorbing Materials for School Bus Interiors. Volume II: Technical Report.  

National Technical Information Service (NTIS)

The report documents a study in school bus crashworthiness and is concerned primarily with the design of interior crash padding systems and the identification and selection of outstanding padding materials for this design application.

L. S. Pauls

1980-01-01

254

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

255

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

256

INVERSE ESTIMATION OF NON ACOUSTICAL PARAMETERS OF ABSORBING MATERIALS USING GENETIC ALGORITHMS  

Microsoft Academic Search

Models describing acoustic properties of porous materials involve quantities, such us characteristic impedance Zc and complex wave number kc, that in turn involve physical parameters (i. e. flow resistivity, tortuosity and porosity). These parameters should be either measured or estimated from measures of acoustic quantities such as the normal incidence absorption coefficient. Unfortunately, direct measurements of theses parameters are often

M. Garoum; M. Rhachi; F. Simón; A. Moreno

257

The efficiency of application of magnetic polymer composites as radio-absorbing materials  

Microsoft Academic Search

The results of investigation of the complex permittivity and permeability of polymer composite materials with different magnetic\\u000a fillers in the frequency range of 1 MHz to 10 GHz are presented. The possibility of controlling the frequency characteristics\\u000a of permeability and permittivity and the absolute values of these parameters via the formation of hybrid composites with multicomponent\\u000a magnetic filler is shown.

A. V. Lopatin; N. E. Kazantseva; Yu. N. Kazantsev; O. A. D’yakonova; J. Vil?áková; P. Sáha

2008-01-01

258

Reaction behavior of B sub 4 C absorber material with stainless steel and Zircaloy in severe light water reactor accidents  

SciTech Connect

The chemical reaction behavior of B{sub 4}C absorber material with stainless steel 1.4919 (type 316) and Zircaloy-4 is studied in the 800 to 1600{degrees}C temeprature range. The reaction kinetics for both systems can be described by parabolic rate laws. Above 100{degrees}C, the reaction zone growth rates in the B{sub 4}C/stainless steel system are about two orders of magnitude higher than those in the B{sub 4}C/Zircaloy-4 system. The compatibility specimens are quickly and completely liquefied at temperatures {ge}1250{degrees}C for the B{sub 4}C/stainless steel reaction couples and temperatures {ge}1650{degrees}C for the B{sub 4}C/Zircaloy-4 reaction couples. In both reaction systems, liquefaction occurs below the melting points of the components.

Hofmann, P. (Kernforschungszentrum Karlsruhe GmbH (Germany, F.R.). Inst. fuer Material- und Festkoerperforschung); Markiewicz, M.E.; Spino, J.L. (Comision Nacional de Energia Atomica, Av. de Libertador 8250, 1429 Buenos Aires (AR))

1990-05-01

259

Determination of Bitter Orange alkaloids in dietary supplements standard reference materials by liquid chromatography with ultraviolet absorbance and fluorescence detection.  

PubMed

Four adrenergic amines [synephrine, octopamine, tyramine, and n-methyltyramine] were determined in a variety of Bitter Orange containing dietary supplements. Two extraction techniques were evaluated in detail: Soxhlet extraction and sonication extraction. A liquid chromatographic separation using a reversed-phase C(18) stationary phase and the ion-pairing reagent sodium dodecyl sulfate was developed to separate the Bitter Orange alkaloids. Ultraviolet absorbance detection at 220 nm and fluorescence detection with excitation at 273 nm and emission at 304 nm were used for the alkaloid detection. The method described was used for the assignment of the levels of the predominant alkaloids in three candidate standard reference materials containing Bitter Orange. PMID:17524413

Putzbach, Karsten; Rimmer, Catherine A; Sharpless, Katherine E; Sander, Lane C

2007-07-13

260

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

261

Syracuse Research Corporation (SRC) ultrawide-bandwidth measurements radar  

NASA Astrophysics Data System (ADS)

In recent years, Syracuse Research Corporation has implemented bandwidth expansion and extended coherent processing techniques to improve scatterer resolution of images derived from existing data. The algorithms can produce extraneous responses, however, which is not the case if the data is collected using an ultrawide bandwidth radar. The long and continuous effort in radar imaging at SRC and the limited number and availability of wideband sensors justified the development of an in-house imaging facility that would be available on demand. As a result, the SRC Ultrawide Bandwidth Measurements Radar was assembled to perform the required measurements of the radar cross section (RCS) of isolated scatterers and to determine their relative location on a wide variety of target types. Along with the use of radar images for target analysis has been the development of target modeling algorithms and software that accurately predict the electromagnetic scattering from complex objects. A few years ago, the software was expanded to model objects as viewed in wide angle bistatic configurations. The SRC radar was utilized to validate these modeling algorithms in several radar bands at large bistatic angles. The system has subsequently been employed to measure a variety of target models and complex shapes and to evaluate the effects of radar absorbing materials (RAMs).

Rankin, Peter M.; Wallenberg, Robert F.

1993-05-01

262

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

263

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

NASA Astrophysics Data System (ADS)

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 load-bearing structures, such as aircraft and other vehicles. Then, CP EBG patterns were also designed that had a 90% electromagnetic (EM) wave absorbing performance within the X-band (8.2-12.4 GHz). Finally, the CP EBG patterns were printed on the top surface of the microstrip patch antenna. The measured radar absorbing performance of the fabricated patch antenna showed that the frontal RCS of the antenna declined by nearly 95% at 10 GHz frequency while the CP EBG patterns had almost no effect on the antenna's performance.

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

2011-01-01

264

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

265

Radar principles  

Microsoft Academic Search

The basic operating principles, design, and applications of radars are discussed in an introductory text intended for first-year graduate students. Topics addressed include radar measurements, radar target cross sections, radar detection, ground effects, matched filters, ambiguity functions, coded radar signals, and radar measurement accuracy. Consideration is given to processing coherent pulse trains, moving-target indicators, CFAR, SAR, and monopulse antenna tracking.

Nadav Levanon

1988-01-01

266

Design of Optimum Systems of Viscoelastic Vibration Absorbers for a Given Material Based on the Fractional Calculus Model  

Microsoft Academic Search

The so often called vibration absorbers, which more appropriately should be called vibration neutralizers, are mechanical devices to be attached to another mechanical system, or structure, called the primary system, with the purpose of controlling, or reducing vibration and sound radiation from machines, structural surfaces and panels. The cheapest and easiest way to construct a vibration absorber is by incorporating

José João de Espíndola; Carlos Alberto Bavastri; Eduardo Márcio de Oliveira Lopes

2008-01-01

267

Comparison of three measurement techniques for the normal absorption coefficient of sound absorbing materials in the free field.  

PubMed

Three different techniques for evaluating the absorption coefficient of sound absorbing materials in free field conditions are discussed. One technique measures the acoustic impedance at one point nearby a specimen, the other two techniques evaluate the impedance from the transfer function of two sound pressures and two particle velocities at two points. These are called "PU-method," "PP-method," and "UU-method," respectively. An iterative algorithm to estimate the acoustic impedance of the locally reactive specimen in the spherical wave field is also applied. First, the effect of receiver positions, specimen areas, and source heights to the measured normal absorption coefficient is investigated by the boundary element method. According to these investigations, the PU-method is most stable against the effect of specimen area, and the UU-method is easily affected by that effect. Closer source to the specimen distance is advantageous for the signal to noise ratio of these measurement techniques, but correction for the effect of the spherical wave field has to be applied. As a finding, the iterative algorithm works for all of three techniques. Finally, the PU-method is applied experimentally with a pressure-velocity sensor and a loudspeaker in a hemi-anechoic room. As a result, the calculated results have been verified. PMID:20000915

Hirosawa, Kunikazu; Takashima, Kazuhiro; Nakagawa, Hiroshi; Kon, Makoto; Yamamoto, Aki; Lauriks, Walter

2009-12-01

268

Radar Background Signal Reduction Study.  

National Technical Information Service (NTIS)

This report summarizes a study whose objective was to identify materials and/or techniques to reduce radar background signals for ground plane radar cross section (RCS) ranges. Background signal reduction is essential for improving the accuracy of RCS mea...

E. F. Knott C. J. Ray M. S. West R. J. Wohlers

1980-01-01

269

Understanding the Radar Properties of Cometary Analog Materials: Experimental Approach in Support of the CONSERT experiment onboard the ROSETTA mission  

NASA Astrophysics Data System (ADS)

In 2014, the CONSERT experiment (COmet Nucleus Sounding Experiment by Radiowave Transmission) on board the ROSETTA mission (2004-2014) will perform a radar tomography of the Comet C67 in an attempt to explore its inner structure. In order to quantitavely invert the upcoming data to access the lithological, mechanical and dust enrichment of comet 67P/Churyumov-Gerasimenko, a good knowledge of the geoelectrical properties of cometary analog material is crucial. In this work, we present laboratory measurements conducted on several types of meteoritic materials and their water ice mixtures that are inferred to be close analogs to cometary and asteroids materials. The measurements are performed in relevant temperatures and pressures in cometary environments. The electromagnetic properties of these materials will be presented as a function of porosity, temperature, frequency and mass percentage of dust contamination in the ice. This resulted in a full parametric space associated with the variation of the geoelectrical properties of cometary analog materials. Our preliminary results suggest that the geoelectrical properties of cometary material are mainly driven by the dust contamination in the ice matrix and by the mineralogical composition of the meteoritic dust inclusion. In particular we observe dielectric constants ranging from 2.8 to 4.4 and loss tangents from ˜0.001 to 0.02 for a chondritic H5 meteoritic dust contamination in the ice ranging from 0 to 75%. The implication of those results in constraining the current geological models of cometary interior will be discussed.

Heggy, E.; Kofman, W.; Clifford, S. M.; Herique, A.; Righter, K.; Levasseur-Regourd, A. C.; Carley, R. A.; Williams, I. P.

2007-08-01

270

A study of Radar Cross Section (RCS) characteristics and their application in future weapon systems  

NASA Astrophysics Data System (ADS)

The sum of components technique was used to calculate the radar cross section (RCS) of a Canberra B2 aircraft. The theoretical result obtained by using simple shapes to model the aircraft were compared with practical results. It is found that this technique can be used to give a quick order of magnitude estimation of a target's RCS. However, the major drawback of this technique is that it cannot predict the rapid changes in RCS which result from a small change in aspect angle. Trends in radar guided weapons, the effects of aircraft shape on the overall RCS of a weapons platform, and reduction of aircraft RCS by appropriate shaping are discussed. Methods, including radar absorption, radar absorbing materials, impedance loading, and active cancellation, which can be used to reduce an aircraft's radar signature and the associated penalties are reviewed.

McCluggage, W. A.

271

Radar cross section: Its prediction measurement and reduction  

Microsoft Academic Search

An introduction to the echo characteristics of radar targets is presented. An overview is first given of radar fundamentals and electromagnetic scattering. Exact prediction techniques, including those pertaining to high-frequency radar cross section (RCS), are addressed. Examples of RCS behavior for simple and complex bodies are shown and discussed. Radar cross section reduction methods and techniques for measuring absorber properties

E. F. Knott; J. F. Shaeffer; M. T. Tuley

1985-01-01

272

Study of the Use of Oxygen-Absorbing Packaging Material to Prolong Shelf-Life of Rations.  

National Technical Information Service (NTIS)

The effectiveness of a new oxygen absorbing packaging technology in modifying the inner atmosphere to very low residual oxygen retarding the growth of spoilage bacteria and mold, biochemical and enzymatic degradation, while minimizing the need for butylat...

E. Castell H. Sue

2010-01-01

273

A new material for prevention of peritendinous fibrotic adhesions after tendon repair: oxidised regenerated cellulose (Interceed), an absorbable adhesion barrier  

Microsoft Academic Search

In this experimental study, we aimed to examine the ability of absorbable oxidised regenerated cellulose (Interceed, TC-7,\\u000a Johnson & Johnson, USA) to inhibit the formation of peritendinous fibrotic adhesions after tendon repair in rats. Both Achilles\\u000a tendons of 23 female Wistar-Albino rats weighing between 350 and 450 grams were cut and repaired. On the right side, Interceed\\u000a absorbable adhesion barriers were

A. Temiz; C. Ozturk; A. Bakunov; K. Kara; T. Kaleli

2008-01-01

274

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

275

Radar principles  

NASA Astrophysics Data System (ADS)

The basic operating principles, design, and applications of radars are discussed in an introductory text intended for first-year graduate students. Topics addressed include radar measurements, radar target cross sections, radar detection, ground effects, matched filters, ambiguity functions, coded radar signals, and radar measurement accuracy. Consideration is given to processing coherent pulse trains, moving-target indicators, CFAR, SAR, and monopulse antenna tracking. Extensive diagrams and graphs are provided.

Levanon, Nadav

276

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

277

A broad-line NMR investigation of water absorbed by cured epoxy resin graphite-fiber composite materials  

Microsoft Academic Search

The effect of water absorption on the mechanical properties of epoxy resin-graphite fiber composites was investigated. Data collected from nuclear magnetic resonance spectra were used to determine three things: (1) the state of the water in the bulk resin and how tightly the water is bound (2) if the water in the composite is being absorbed primarily in the matrix

Fuller

1980-01-01

278

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

279

Determination of Bitter Orange alkaloids in dietary supplements standard reference materials by liquid chromatography with ultraviolet absorbance and fluorescence detection  

Microsoft Academic Search

Four adrenergic amines [synephrine, octopamine, tyramine, and n-methyltyramine] were determined in a variety of Bitter Orange containing dietary supplements. Two extraction techniques were evaluated in detail: Soxhlet extraction and sonication extraction. A liquid chromatographic separation using a reversed-phase C18 stationary phase and the ion-pairing reagent sodium dodecyl sulfate was developed to separate the Bitter Orange alkaloids. Ultraviolet absorbance detection at

Karsten Putzbach; Catherine A. Rimmer; Katherine E. Sharpless

2007-01-01

280

Characterization of CuInSe2 material and devices: comparison of thermal and electrochemically prepared absorber layers  

NASA Astrophysics Data System (ADS)

CuInSe2-based absorber layers for photovoltaic devices have been fabricated using two different scalable processes, electrodeposition and sputtering, both followed by thermal annealing. The structural properties of the absorber layers were studied by SEM, XRD and MiniSIMS. Sputtered absorber layers exhibit larger grain sizes than electrodeposited layers, but both types of film consist of randomly orientated crystallites. Electrodeposited layers appear to have a uniform composition with evidence of a MoSe2 layer at the back contact, whilst sputtered layers show no evidence for a MoSe2 layer. The external quantum efficiency spectrum of films and completed devices was measured, and the band gap and broadening parameters were obtained using electroreflectance spectroscopy. A device based on electrodeposited CuInSe2 achieved an AM 1.5 efficiency of 6.6%, whilst a device based on sputtered CuInSe2 had an efficiency of 8.3%. Impedance measurements were used to calculate doping densities of 2 × 1016 and 4 × 1015 cm-3 for the electrodeposited and sputtered devices, respectively.

Dale, P. J.; Samantilleke, A. P.; Zoppi, G.; Forbes, I.; Peter, L. M.

2008-04-01

281

A two-layer dielectric absorber covering a wide frequency range  

Microsoft Academic Search

A two-layer dielectric absorber for use as high temperature radar wave-absorbing material was developed by hot-pressing nanometer SiC and LAS glass-ceramic. The complex permittivity of the hot-pressed LAS glass-ceramic and SiC\\/LAS composite was investigated at 8.2–12.4GHz. Results show that the real and imaginary parts of the permittivities of the SiC\\/LAS composites greatly increase as the content of the nanometer SiC

Fa Luo; Dong-mei Zhu; Wan-cheng Zhou

2007-01-01

282

The feasibility of searching for contraband materials using a gamma-ray 'radar' system  

Microsoft Academic Search

A technique for searching for contraband materials that may be hidden behind a barrier is described. This imaging technique is based on the detection of one of the two annihilation photons produced by a positron-emitter that has scattered in the target, in coincidence with the detection of the second photon in a position-sensitive scintillation counter. The results of a feasibility

C. Ferguson; D. Ramsden

2004-01-01

283

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

284

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

285

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

286

Structural and electronic properties of CuSbS2 and CuBiS2: potential absorber materials for thin-film solar cells.  

PubMed

As the demand for photovoltaics rapidly increases, there is a pressing need for the identification of new visible light absorbing materials for thin-film solar cells that offer similar performance to the current technologies based on CdTe and Cu(In,Ga)Se(2). Metal sulphides are the ideal candidate materials, but their band gaps are usually too large to absorb significant fractions of visible light. However, by combining Cu(+) (low binding energy d(10) band) and Sb(3+)/Bi(3+) (low binding energy s(2) band), the ternary sulphides CuSbS(2) and CuBiS(2) are formed, which have been gathering recent interest for solar cell applications. Using a hybrid density functional theory approach, we calculate the structural and electronic properties of these two materials. Our results highlight the stereochemical activity of the Sb and Bi lone pair electrons, and predict that the formation of hole carriers will occur in the Cu d(10) band and hence will involve oxidation of Cu(I). PMID:22514020

Dufton, Jesse T R; Walsh, Aron; Panchmatia, Pooja M; Peter, Laurie M; Colombara, Diego; Islam, M Saiful

2012-05-28

287

Performances of the Partition of Unity Finite Element Method for the analysis of two-dimensional interior sound fields with absorbing materials  

NASA Astrophysics Data System (ADS)

The paper deals with the numerical simulation of the acoustic field in two-dimensional cavities in which absorbing materials are present. Though Finite Element Method (FEM) could be employed for this purpose, the discretization level required for achieving reasonable accuracy renders the method impractical in the mid-frequency range. To alleviate this limitation, the Partition of Unity Finite Element Method (PUFEM) using plane wave functions has been shown to be very effective for solving short wave Helmholtz problems. In the present work, the method is extended to the computation of the pressure wave field within the absorbing media which is modeled as a bulk-reacting material characterized by a complex-valued and frequency dependent mean density and dynamic compressibility. Lagrange multipliers are used to enforce the transmission conditions at the air-material interface. Performances of the PUFEM are compared with a standard FEM in several examples of practical interests. It is shown that the technique is a good candidate for solving noise control problems at high frequency.

Chazot, J.-D.; Nennig, B.; Perrey-Debain, E.

2013-04-01

288

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

289

A new material for prevention of peritendinous fibrotic adhesions after tendon repair: oxidised regenerated cellulose (Interceed), an absorbable adhesion barrier  

PubMed Central

In this experimental study, we aimed to examine the ability of absorbable oxidised regenerated cellulose (Interceed, TC-7, Johnson & Johnson, USA) to inhibit the formation of peritendinous fibrotic adhesions after tendon repair in rats. Both Achilles tendons of 23 female Wistar-Albino rats weighing between 350 and 450 grams were cut and repaired. On the right side, Interceed absorbable adhesion barriers were wrapped around the repaired tendon (group I). On the left, the same procedures were applied except for the Interceed wrapping and these were grouped as control (group II). Animals were sacrificed at postoperative day 28 and macroscopic and histological examination was performed. All the animals survived and no tendon rupture was observed. No wound dehiscence, wound infection or exposure of repaired tendons occurred. Macroscopically, there were three (13.1%) tendons without adhesion formation and 20 (86.9%) tendons with inferior adhesion formation in group I; on the other hand, there were 16 tendons (69.5%) with medium grade adhesion formation and seven tendons (30.5%) with severe peritendinous adhesion formation in group II (control group) (p?absorbable oxidised regenerated cellulose merits further evaluation as a potential treatment to inhibit the formation of peritendinous adhesions. Rigorous and extensive controlled trials should be undertaken on patients undergoing tendon repair with or without this barrier.

Temiz, A.; Bakunov, A.; Kara, K.; Kaleli, T.

2007-01-01

290

Radar Entomology  

NSDL National Science Digital Library

Radar tracking used to profile insect migration, mating and flight patterns. Many links to various pages include current workers in radar entomology, historical uses of the technology, and many images.

0002-11-30

291

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

292

Annular burnable absorber rod  

SciTech Connect

This patent describes a neutron irradiation environment of a water cooled and moderated reactor core a fuel assembly having a discrete annular burnable absorber rod, the rod being free of nuclear fuel material the rod comprising a first elongated hollow tube having opposed ends, a second elongated hollow tube having opposed ends. The first and second tubes are constructed of a zirconium material, the first and second tubes concentrically arranged about a common axis to provide a coextensive annular space therebetween and a path for the water through the first tube along the common axis. A sealing means seals the annular space at common opposed ends of the first and second tube and a hollow niobium tubular support is arranged within the annular space. The tubular support has an inner and outer surface, a layer of burnable neutron absorber material provided on at least a portion of one of the surfaces of the support the layer of the burnable neutron absorber material selected from the group of boron compounds consisting of boron carbide, boron nitride and zirconium diboride; and the layer of the burnable neutron absorber material having a thickness between 0.002 to 0.010 inches.

Chubb, W.

1986-12-02

293

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

294

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

295

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

296

Apollo couch energy absorbers  

NASA Technical Reports Server (NTRS)

Load attenuators for the Apollo spacecraft crew couch and its potential applications are described. Energy absorption is achieved through friction and cyclic deformation of material. In one concept, energy absorption is accomplished by rolling a compressed ring of metal between two surfaces. In another concept, energy is absorbed by forcing a plastically deformed washer along a rod. Among the design problems that had to be solved were material selection, fatigue life, ring slippage, lubrication, and friction loading.

Wesselski, C. J.; Drexel, R. E.

1972-01-01

297

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

298

Technical evaluation of Russian aircraft stealth coating and structural materials  

Microsoft Academic Search

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

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

1996-01-01

299

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

2008-05-01

300

Investigations toward tunability of mechanical, thermal, and impact properties of thiol-ene networks for novel high energy absorbing materials  

NASA Astrophysics Data System (ADS)

The UV polymerization of thiols with electron rich alkenes is a highly resourceful reaction that has been utilized by scientists within various disciplines to produce an even more versatile display of applications. This dissertation focuses on a newer application, thiol-ene network (TEN) materials for energy absorption devices. TEN networks display a host of positive polymer properties such as low stress, high optical clarity and uniformity, but they also suffer from unfavorable mechanical properties such as low toughness and elongation at break. The poor mechanical properties demonstrated by TENs prohibit them as choice materials for applications requiring thicker material forms, including energy damping devices. The chapters in this dissertation focus on enhancing the toughness of TENs via urethane or thiourethane incorporation wherein toughness is enhanced by either hydrogen bonding or underlying network morphologies. Impact behaviors of base systems were investigated and correlated to polymer glass transition temperature. The tunability of the temperature associated with viscoelastic relaxation was also investigated by developing hybrid networks containing two thiol components. The relevance of the works performed is highlighted by the major contributions realized by understanding structure-property relationships and network morphology on underlying principles of energy absorption.

McNair, Olivia Devon

301

Effect of zeolite nano-materials and artichoke (Cynara scolymus L.) leaf extract on increase in urinary clearance of systematically absorbed nicotine.  

PubMed

Nicotine, the main pharmacologically active component in tobacco and cigarette, has some toxic effects and also high potential for addiction. In this study, the effect of artichoke (Cynara scolymus L.) and zeolite nano-materials on urinary excretion of nicotine and consequently elimination of systematically absorbed nicotine was investigated. A simple, valid and highly sensitive high performance liquid chromatography method has been developed for determination of nicotine in rat urine according to guidelines for bioanalysis.It was found that nano-zeolites can cause increase in urinary concentration of nicotine due to its high surface adsorption. Artichoke leaf extract can cause increase in urinary excretion of nicotine in longer post administration times. It was observed that co-administration of nanozeolites and the leaf extract has the synergetic effect on increasing the urinary excretion of nicotine. PMID:23196970

Malekshah, R E; Mahjub, R; Rastgarpanah, M; Ghorbani, M; Partoazar, A R; Mehr, S E; Dehpour, A R; Dorkoosh, F A

2012-12-01

302

Radar - Principles, technology, applications  

NASA Astrophysics Data System (ADS)

An overview of modern radar is presented. The topics addressed include: functions and parameters of the radar system, the radar equation, targets and interfering signals, target echo information extraction, tracking radar, radar transmitters and microwave components, radar antennas, receivers and displays, radar signal processing, high resolution radar.

Edde, Byron

303

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

304

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

305

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

NASA Astrophysics Data System (ADS)

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 of electromagnetic waveform nature, determine by pulsations of electrical-E) and magnetically-H components of electromagnetic wave in interdependence with Maxwell equations. The gypsum ore is calcium sulphate dehydrate (CaSO4.2H2O) using at modeling gypsum plaster fabrication, which is calcium sulphate hemihydrate (CaSO4.1/2H2O), that has behavior of dielectric with losses. The gypsum ore getting in microwave field, in conditions of predictable pressure and temperature has transformed in modeling gypsum plaster, by quick lost of a part from crystallization water. The processing time is very short, which due to a great productivity and machining efficiency, finally of low process cost. All of these recommend continuing the research at pilot station level.

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

2009-11-01

306

Radar Astronomy.  

National Technical Information Service (NTIS)

A general review of radar astronomy is given. Typical radar systems are described and results cited. Methods of determining elements of orbits and rotation rates of planets are discussed. A proposed test of the Einstein theory of general relativity is des...

G. H. Pettengill I. I. Shapiro

1965-01-01

307

Radar astronomy  

Microsoft Academic Search

Radar Astronomy is a new and growing branch of Astronomy. Although it seems that radio echo studies must be confined to the solar system, they can play an important part in developing our understanding of the Sun and the planets. At the present time these objects are barely detectable by radar techniques and much of the work has been concerned

J. V. Evans

1960-01-01

308

Structural investigation and microwave characteristics of (Ba0.2La0.8)Fe0.2Mn0.4Ti0.4O3 absorbing materials  

NASA Astrophysics Data System (ADS)

Synthesis and characterization of (Ba0.2La0.8)Fe0.2Mn0.4Ti0.4O3 absorbing material by mechanical alloying process has been performed. The absorbing material was prepared by oxide materials, namely BaCO3, La2O3, TiO2, Fe2O3, and MnCO3. The mixture was milled for 10 h and then sintered at a temperature of 1000 ° C for 10 h. The refinement results of x-ray diffraction pattern of lanthanum manganite substituted with barium showed that the sample consisted of two phases, namely, La0.9125MnO3 phase which has a structure monoclinic (I12/a1) with lattice parameters a = 5.527(1) Å, b = 5.572(1) Å and c = 7.810(1) Å, ? = ? = 90° and ? = 89.88(5)°, the unit cell volume of V = 240.57(8) Å3, and the atomic density of ? = 6.238 gr.cm-3. The microstructure analyses showed that the particle shapes was polygonal with the varied particle sizes of 1 ˜ 3 ?m distributed homogeneously on the surface of the samples. The results of the electromagnetic wave absorption curve analysis by using a vector network analyzer (VNA) showed that the sample can absorb microwaves in the frequency range of 8-15 GHz with a very wide absorption bandwidth. It indicates that the as prepared absorber presents potential absorbing property in X and Ku-band. We concluded that the (Ba0.2La0.8)Fe0.2Mn0.4Ti0.4O3 material can be applied as a candidate absorber material of microwaves or electromagnetic wave.

Manaf, Azwar; Adi, Wisnu Ari

2014-03-01

309

Absorber pin development in Europe  

Microsoft Academic Search

The neutron absorbing material chosen for the absorber elements of the European fast reactor (EFR) is boron carbide. Various pin designs are studied in Europe: (1) vented helium-bonded pins chosen for prototype fast reactor (PFR) control rods, (2) vented sodium-bonded pins chosen for the Phenix and Superphenix control rods, (3) vented shrouded sodium-bonded pins chosen for future loads of Superphenix

A. Languille; J. Escleine; B. Kryger; B. Munroe; B. Steinmetz

1992-01-01

310

Polymer saturable absorber materials in the 1.5 mum band using poly-methyl-methacrylate and polystyrene with single-wall carbon nanotubes and their application to a femtosecond laser  

Microsoft Academic Search

We report saturable absorber materials in the 1.5 mum band that consist of poly-methyl-methacrylate (PMMA) and polystyrene (PS) polymers with single-wall carbon nanotubes (SWNTs). A very uniform dispersion of SWNT in PMMA and PS polymers has been realized by using chlorobenzene or tetrahydrofuran as a dispersion solvent. These materials, which are as thick as 1 mm, are easily optically polished

Masataka Nakazawa; Seiji Nakahara; Toshihiko Hirooka; Masato Yoshida; Toshikuni Kaino; Kyoji Komatsu

2006-01-01

311

Absorbent product to absorb fluids. [for collection of human wastes  

NASA Technical Reports Server (NTRS)

A multi-layer absorbent product for use in contact with the skin to absorb fluids is discussed. The product utilizes a water pervious facing layer for contacting the skin, overlayed by a first fibrous wicking layer, the wicking layer preferably being of the one-way variety in which fluid or liquid is moved away from the facing layer. The product further includes a first container section defined by inner and outer layer of a water pervious wicking material between which is disposed a first absorbent mass. A second container section defined by inner and outer layers between which is disposed a second absorbent mass and a liquid impermeable/gas permeable layer. Spacesuit applications are discussed.

Dawn, F. S.; Correale, J. V. (inventors)

1982-01-01

312

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

313

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

314

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

315

A perfectly matched anisotropic absorber for use as an absorbing boundary condition  

Microsoft Academic Search

An alternative formulation of the “perfectly matched layer” mesh truncation scheme is introduced. The present scheme is based on using a layer of diagonally anisotropic material to absorb outgoing waves from the computation domain. The material properties can be chosen such that the interface between the absorbing material and free space is reflection-less for all frequencies, polarizations, and angles of

Zachary S. Sacks; David M. Kingsland; Robert Lee; Jin-Fa Lee

1995-01-01

316

Radar Antenna.  

National Technical Information Service (NTIS)

An antenna is described for range-gated, pulse doppler, radar systems. The antenna includes first and second, shortened, half-wave dipoles and first and second reflecting screens. One dipole is fed through a fixed 22 1/2 degree phase-shift network while t...

O. E. Rittenback

1978-01-01

317

Radar Roadmap.  

National Technical Information Service (NTIS)

Instrumentation radar has played a very significant role in testing and training for more than 50 years. Along with optics, it has been a major supplier of time space position information (TSPI). With the advent of the Global Positioning System (GPS), the...

1998-01-01

318

Radar nomenclature  

Microsoft Academic Search

Like much of the equipment used by the armed forces, both civil and military radar systems may be allocated an identification resolved from a synonym, mnemonic, project name, number, application notation, or specialised nomenclature and sometimes may even be based upon the whims of an intelligence reporting service. Of these, mnemonics are very popular; whilst of designation systems used by

J. C. Wise

2004-01-01

319

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

320

Absorbent product and articles made therefrom  

NASA Technical Reports Server (NTRS)

A multilayer absorbent product for use in contact with the skin to absorb fluids is described. The product has a water pervious facing layer for contacting the skin, and a first fibrous wicking layer overlaying the water pervious layer. A first container section is defined by inner and outer layers of a water pervious wicking material in between a first absorbent mass and a second container section defined by inner and outer layers of a water pervious wicking material between what is disposed a second absorbent mass, and a liquid impermeable/gas permeable layer overlaying the second fibrous wicking layer.

Dawn, F. S.; Correale, J. V. (inventors)

1982-01-01

321

Low temperature selective absorber research  

NASA Astrophysics Data System (ADS)

Research carried out since 1979 on selective absorbers is surveyed, with particular attention given to the low-temperature coatings seen as promising for flat plate and evacuated tube applications. The most thoroughly investigated absorber is black chrome, which is highly selective and is the most durable low-temperature absorber. It is believed that other materials, because of their low cost and lower content of strategic materials, may eventually supplant black chrome. Among these candidates are chemically converted black nickel; anodically oxidized nickel, zinc, and copper composites; and nickel or other low-cost multilayer coatings. In reviewing medium and high-temperature research, black chrome, multilayer coatings and black cobalt are seen as best medium-temperature candidates. For high temperatures, an Al2O3/Pt-Al203 multilayer composite or the zirconium diboride coating is preferred.

Herzenberg, S. A.; Silberglitt, R.

322

Radar technology in ITT  

Microsoft Academic Search

With the introduction in the late 1980s and 1990s of such technologies as VLSI, GaAs monolithic circuits, integrated electrooptics, coherent fiber optics, high-power solid-state millimeter-wave sources, and specialized materials, the performance, packaging, and cost of radar systems will undergo radical changes. It is noted by way of example that low-cost GaAs monolithic transmitter\\/receivers (employing integrated optics technology) coherently fed by

R. Palmer

1982-01-01

323

Effect of inelastic shear stress at the interfaces in the material with a unidirectional fibrous structure on the SIF for a crack in the fiber and the energy absorbed at fiber fracture.  

PubMed

The paper suggests considering the presence of inelastic shear mechanisms in the direction of the maximum tensile stress and the absence of these mechanisms in the other directions as the main feature of a structural material of biological origin. A "cracked fiber in tube" model is used for the study of the effect of interface cohesive strength on the stress intensity factor (SIF) for a crack in the fiber and on the energy absorbed under inelastic shear at the interface of fibers at their fracture. The values of the cohesive strength of the interface between the fibers and the distance between the cracks in the fiber at which the maximum energy is absorbed at material fracture at the stage of the crack growth in the fibers are obtained. This stage precedes the pullout process of the completely fractured fibers. PMID:24566378

Borovik, Alexandra V; Borovik, Valery G

2014-06-01

324

Equatorial radar system  

Microsoft Academic Search

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar, called the Equatorial Radar, will be built in Pontianak, Kalimantan Island, Indonesia (0.03 N, 109.3 E). The system is a 47 MHz monostatic Doppler radar with an active

S. Rukao; T. Tsuda; T. Sato; S. Kato

1989-01-01

325

Radars in space  

NASA Technical Reports Server (NTRS)

The capabilities of active microwave devices operating from space (typically, radar, scatterometers, interferometers, and altimeters) are discussed. General radar parameters and basic radar principles are explained. Applications of these parameters and principles are also explained. Trends in space radar technology, and where space radars and active microwave sensors in orbit are going are discussed.

Delnore, Victor E.

1990-01-01

326

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

327

TRMM radar  

NASA Astrophysics Data System (ADS)

The results of a conceptual design study and the performance of key components of the Bread Board Model (BBM) of the Tropical Rainfall Measuring Mission (TRMM) radar are presented. The radar, which operates at 13.8 GHz and is designed to meet TRMM mission objectives, has a minimum measurable rain rate of 0.5 mm/h with a range resolution of 250 m, a horizontal resolution of about 4 km, and a swath width of 220 km. A 128-element active phased array system is adopted to achieve contiguous scanning within the swath. The basic characteristics of BBM were confirmed by experiments. The development of EM started with the cooperation of NASDA and CRL.

Okamoto, Kenichi

1993-05-01

328

TRMM radar  

NASA Technical Reports Server (NTRS)

The results of a conceptual design study and the performance of key components of the Bread Board Model (BBM) of the Tropical Rainfall Measuring Mission (TRMM) radar are presented. The radar, which operates at 13.8 GHz and is designed to meet TRMM mission objectives, has a minimum measurable rain rate of 0.5 mm/h with a range resolution of 250 m, a horizontal resolution of about 4 km, and a swath width of 220 km. A 128-element active phased array system is adopted to achieve contiguous scanning within the swath. The basic characteristics of BBM were confirmed by experiments. The development of EM started with the cooperation of NASDA and CRL.

Okamoto, Kenichi

1993-01-01

329

Platelike Dynamic Vibration Absorber.  

National Technical Information Service (NTIS)

The patent application describes platelike dynamic vibration absorbers for providing vibration suppression. Optimum values of their tuning and damping are specified. The dynamic absorbers are comprised either of a circular or an annular damped plate that ...

J. C. Snowdon

1975-01-01

330

Infrared Saturable Absorber Devices.  

National Technical Information Service (NTIS)

Gaseous saturable absorbers are studied. These absorbers are used for mode-locking of infrared lasers, particularly CO2. Nonlinear-optical coefficients and transition moments were measured. Detectors for infrared radiation were also studied. Mechanisms of...

S. E. Schwarz

1975-01-01

331

Bend-absorbing clamp  

NASA Technical Reports Server (NTRS)

Compact, inexpensive clamp for flexible cables or rigid tubes absorbs vibrations and other motion. It accomodates wide range of dimensions, and saves space by eliminating pigtails or bellows commonly used to absorb linear movement or vibrations

Abbott, J. R.; Valencia, B., Jr.

1979-01-01

332

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

333

Planetary Radar Studies.  

National Technical Information Service (NTIS)

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 an...

T. W. Thompson J. A. Cutts

1981-01-01

334

Shock absorbing subassembly  

SciTech Connect

A shock absorbing subassembly, for use in an oil well drilling string above a drilling bit to absorb and reduce bit induced vibration and impact loads, wherein a shock absorber element is provided which includes at least one set of ring springs. The ring springs comprise alternating closed outer rings and closed inner rings with tapered contact surfaces on the outer and inner rings.

Zabcik, C.J.

1981-01-27

335

Downhole pulse radar  

SciTech Connect

This patent describes a downhole radar tool for use with a system for detecting and locating fractures in a geological formation near a borehole. The tool comprises: a generally cylindrical housing; transmitter means; transmitting antenna means; receiving antenna means; isolator means; signal processing means; wherein each of the transmitting and receiving antenna means is a directional antenna comprising: a reflector antenna; a cylindrical pipe; dielectric material filling the electromagnetically active region, the material having a dielectric constant within the range of 20 to 150.

Chang, H.T.

1989-03-21

336

Phenolic laminate solar absorber panel and method of making  

Microsoft Academic Search

A solar flat plate absorber panel is molded from a laminate consisting of a suitable web material impregnated with a thermosetting phenolic resin. The absorber plate is pressure formed from superimposed layers of material and mold-cured to produce a unitary structure having a first or solar radiation absorbing surface on one side and an integral closed hollow lattice work of

Severson

1979-01-01

337

SILVER-CADMIUM-INDIUM ABSORBER DEVELOPMENT  

Microsoft Academic Search

Development of an Ag--Cd--In alternate absorber section is described for ; Army Type SM reactors. The absorber material composition and the geometric ; configuration are described, and the nuclear and thermal analyses supporting this ; configuration are given. A detailed description of the manufacturing practice ; employed in fabricating the final design component is also included. (auth);

R. A. Shaw; R. L. Harris

1962-01-01

338

Metallic tube type energy absorbers: A synopsis  

Microsoft Academic Search

This paper presents an overview of energy absorbers in the form of tubes in which the material used is predominantly mild steel and\\/or aluminium. A brief summary is also given of frusta type energy absorbers. The common modes of deformation such as lateral and axial compression, indentation and inversion are reviewed. Theoretical, numerical and experimental methods which help to understand

A. G. Olabi; Edmund Morris; M. S. J. Hashmi

2007-01-01

339

Highly efficient special sound absorbing solutions  

NASA Technical Reports Server (NTRS)

Highly efficient special sound absorbing structures with the following criteria are considered: (1) A distribution surface of the sound absorbing material greater than that of the building element on which the structure is placed; (2) The highest possible absorption coefficient in the widest possible frequency band; and (3) adaptability to different construction and aesthetic conditions.

Ionescu, M.; Petre-Lazar, S.

1974-01-01

340

Nonventing, Regenerable, Lightweight Heat Absorber  

NASA Technical Reports Server (NTRS)

A lightweight, regenerable heat absorber (RHA), developed for rejecting metabolic heat from a space suit, may also be useful on Earth for short-term cooling of heavy protective garments. Unlike prior space-suit-cooling systems, a system that includes this RHA does not vent water. The closed system contains water reservoirs, tubes through which water is circulated to absorb heat, an evaporator, and an absorber/radiator. The radiator includes a solution of LiCl contained in a porous material in titanium tubes. The evaporator cools water that circulates through a liquid-cooled garment. Water vapor produced in the evaporator enters the radiator tubes where it is absorbed into the LiCl solution, releasing heat. Much of the heat of absorption is rejected to the environment via the radiator. After use, the RHA is regenerated by heating it to a temperature of 100 C for about 2 hours to drive the absorbed water back to the evaporator. A system including a prototype of the RHA was found to be capable of maintaining a temperature of 20 C while removing heat at a rate of 200 W for 6 hours.

Izenson, Michael G.; Chen, Weibo

2008-01-01

341

Effect of imperfectly conducting surface of scatter on its radar cross section  

NASA Astrophysics Data System (ADS)

The scale-down model testing of radar cross sections (RCSs) for imperfectly conducting bodies requires physical similarity between models and prototype. It is often impossible to satisfy all the requirements at the same time, so it is necessary to study the effect of imperfectly conducting surface of scatter on its RCS. Dimensional analysis and theory of the model are used. As a result the relationship between sigma/lambda squared and eta sub s is obtained, and the comparison between theoretical and experimental values for a cylinder coated with absorbent materials is given.

Shi, Zhendong; Ding, Chunsheng

1992-06-01

342

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

343

Microwave-absorbing properties of Ni 0.50-xZn 0.50-xMe 2xFe 2O 4 (Me=Cu, Mn, Mg) ferrite-wax composite in X-band frequencies  

NASA Astrophysics Data System (ADS)

Ni 0.5-xZn 0.5-xMe 2xFe 2O 4 (Me=Cu, Mg, Mn; x=0.00 and 0.10) ferrite powders were prepared by the nitrate-citrate precursor method and investigated as a radar absorbing material (RAM) in a frequency range of 8-12 GHz (X-band). The effects of Cu 2+, Mn 2+ and Mg 2+ substitution on the microwave-absorbing feature, the complex permeability ( ?r*) and the complex permittivity ( ?r*) were investigated. The microwave-absorbing properties were studied as a function of frequency, Me 2+ content, and thickness of absorber. The adoption of Cu 2+ and Mn 2+ substitution was found to improve the microwave absorption and bandwidth, while the substitution of Mg 2+ was found to reduce the microwave absorption in relation to non-substituted NiZn ferrite.

Bueno, Alexandre R.; Gregori, Maria L.; Nóbrega, Maria C. S.

344

Far-field measurements and maximum entropy analysis of lossy material on a conducting plate  

Microsoft Academic Search

The relationships between Fourier techniques and maximum entropy techniques for the case of scattering measurements from metal-plate-backed lossy dielectric material are described. A set of experimental measurements were made in the frequency and aspect-angle domains on square panels of a multilayer radar absorbing material (RAM) backed by a conducting plate (approximately 30 x 30 cm). Interpretations of the results with

Eric K. Walton

1989-01-01

345

Radar detection of Iapetus  

NASA Astrophysics Data System (ADS)

We have obtained echoes from the bright, trailing hemisphere of Iapetus using the Arecibo Observatory's 13-cm radar system on three dates in January 2002. A circularly polarized signal was transmitted and an echo in the opposite circular (OC) sense to that transmitted was clearly received along with a much weaker detection of echo power in the same circular (SC) sense. Prior to this experiment, one expectation may have been that the radar scattering properties of Iapetus may behave like the similar atmosphere-less, icy surfaces of the Galilean satellites which, due to an efficient multiple scattering mechanism, are strong backscatterers with SC reflections stronger than their OC reflections. Instead we find that Iapetus' radar cross section and polarization properties are very different from those of the icy Galilean satellites, and more reminiscent of less efficient and less exotic scattering mechanisms such as dominate the echoes from inner Solar System targets. Thus these observations indicate that there is a significant difference between the surface properties of Iapetus and the icy Galileans despite their overall classification as low temperature, water ice surfaces. A plausible explanation for Iapetus' inefficient scattering is that contaminants in the water ice increase the absorption of the signal and suppress any multiple scattering. Likely contaminants on Iapetus are ammonia and the dark material from Cassini Regio embedded below the surface. Proposed observations will seek to measure Iapetus' radar scattering law and to detect the dark, leading side which was not targeted during this observing session. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation.

Black, G. J.; Campbell, D. B.; Carter, L. M.; Ostro, S. J.

2002-09-01

346

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

347

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

348

Equatorial Radar System.  

National Technical Information Service (NTIS)

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar, called the Equatorial Radar, will be built in Pontianak, Kalimantan...

S. Rukao T. Tsuda T. Sato S. Kato

1989-01-01

349

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

350

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

351

Topics for a statistical description of radar cross section  

NASA Astrophysics Data System (ADS)

A comprehensive guide to the statistical description of radar cross section (RCS) is presented. The topics discussed include: definition of field quantities and Maxwell's equations, constitutive relations, boundary conditions and surface currents, Green's functions, diffraction of a plane wave by a perfectly absorbing half-plane, asymptotic approximation methods, and diffraction approximation methods. Also considered are: numerical approximations and numerical methods, RCS measurements, RCS of simple and complex shapes, new method for comparing experimental and theoretical data, elements of detection theory, impedance boundary condition, reflection and transmission, stratified media, gyroelectromagnetic layers, and the inverse problem for biaxial materials. As examples, the 727 at 0.94 GHz and the Firebee at 9.0 GHz are examined.

Maffett, Andrew Lewis

352

High resolution polarimetric FMCW radar  

Microsoft Academic Search

The Monash FMCW radar has been successful in detecting and locating defects in natural and man-made dielectrics (eg. defects in sawmill wood), with a range resolution, of 2 cm in wood. The authors show how to improve this resolution and provide polarimetric capability, which is important in anisotropic and optically active materials. The large bandwidth requirement has required a redefinition

A. Z. Tirkel; C. F. Osborne

1993-01-01

353

Absorbing Outflows in AGN  

NASA Technical Reports Server (NTRS)

The goal of this program was a comprehensive multiwavelength study of absorption phenomena in active galactic nuclei (AGN). These include a variety of associated absorption systems: X-ray warm absorbers, X-ray cold absorbers. UV absorbers with high ionization lines, MgII absorbers, red quasars and BALQSOs. The aim is to determine the physical conditions in the absorbing outflows, study their inter-relations and their role in AGN. We designed several observing programs to achieve this goal: X-ray spectroscopy, UV spectroscopy, FLAY spectroscopy and X-ray imaging. We were very successful towards achieving the goal over the five year period as shown through following observing programs and papers. Copies of a few papers are attached with this report.

Mathur, Smita

2002-01-01

354

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

355

Comet radar explorer  

NASA Astrophysics Data System (ADS)

The Comet Radar Explorer (CORE) is designed to perform a comprehensive and detailed exploration of the interior, surface, and inner coma structures of a scientifically impor-tant Jupiter family comet. These structures will be used to investigate the origins of cometary nuclei, their physical and geological evolution, and the mechanisms driving their spectacular activity. CORE is a high heritage spacecraft, injected by solar electric propulsion into orbit around a comet. It is capable of coherent deep radar imaging at decameter wavelengths, high resolution stereo color imaging, and near-IR imaging spectroscopy. Its primary objective is to obtain a high-resolution map of the interior structure of a comet nucleus at a resolution of ¿100 elements across the diameter. This structure shall be related to the surface geology and morphology, and to the structural details of the coma proximal to the nucleus. This is an ideal complement to the science from recent comet missions, providing insight into how comets work. Knowing the structure of the interior of a comet-what's inside-and how cometary activity works, is required before we can understand the requirements for a cryogenic sample return mission. But more than that, CORE is fundamental to understanding the origin of comets and their evolution in time. The mission is made feasible at low cost by the use of now-standard MARSIS-SHARAD reflec-tion radar imaging hardware and data processing, together with proven flight heritage of solar electric propulsion. Radar flight heritage has been demonstrated by the MARSIS radar on Mars Express (Picardi et al., Science 2005; Plaut et al., Science 2007), the SHARAD radar onboard the Mars Reconnaissance Orbiter (Seu et al., JGR 2007), and the LRS radar onboard Kaguya (Ono et al, EPS 2007). These instruments have discovered detailed subsurface structure to depths of several kilometers in a variety of terrains on Mars and the Moon. A reflection radar deployed in orbit about a comet will enjoy significant simplifying benefits compared to using the same instrument for Mars or lunar radar science: (1) The proximity of operations leads to a much higher signal to noise, as much as +30 dB. (2) The lack of an ionosphere simplifies data modeling and analysis. (3) The body is globally illuminated during every data acquisition, minimizing ambiguity or 'clutter' and allowing for tomographic reconstruction. What is novel is the data processing, where instead of a planar radargram approach we coherently process the data into an image of the deep interior. CORE thus uses a MARSIS-SHARAD heritage radar to make coherent reflection sounding measurements, a 'CAT SCAN' of a comet nucleus. What is unique about this mission compared to the Mars radars mentioned above, is that the target is a finite mass of dirty ice in free space, rather than a sheet of dirty ice draped on a planet surface. The depth of penetration (kilometers), attainable resolution (decameters), and the target materials, are more or less the same. This means that the science story is robust, and the radar implementation is robust. The target is comet 10P/Tempel 2, discovered by Wilhelm Tempel in 1873 and observed on most apparitions since. It has been extensively studied, in part because of interest as a CRAF target in the mid-1980s, and much is known about it. Tempel 2 is one of the largest known comet nuclei, 16×8×8 km (about the same size as Halley) [1] and has rotation period 8.9 hours [3,5,6,7,9]. The spin state is evolving with time, spinning up by ˜10 sec per perihelion pass [5,7]. The comet is active, but not exceedingly so, especially given its size. The water production is measured at ˜ 4 × 1028 mol/sec at its peak [2], a factor of 25 lower than comet Halley, and it is active over only ˜2% of its surface. The dust environment is well known, producing a factor of ˜100 less dust than Halley. Comet References: [1] A'Hearn et al., ApJ 347, 1155, 1989 [2] Feldman and Festou, ACM 1991, p. 171, 1992 [3] Jewitt and Luu, AJ 97, 1766, 1989 [4] Lamy et al., Comets II p 223. 2009 [5] Muel

Farnham, Tony; Asphaug, Erik; Barucci, Antonella; Belton, Mike; Bockelee-Morvan, Dominique; Brownlee, Donald; Capria, Maria Teresa; Carter, Lynn; Chesley, Steve; Farnham, Tony; Gaskell, Robert; Gim, Young; Heggy, Essam; Herique, Alain; Klaasen, Ken; Kofman, Wlodek; Kreslavsky, Misha; Lisse, Casey; Orosei, Roberto; Plaut, Jeff; Scheeres, Dan

356

Modified Berenger PML absorbing boundary condition for FDTD meshes  

Microsoft Academic Search

A new modified, perfectly matched layer absorbing boundary condition (MPML ABC) is presented. In the MPML, the introducing of extra degrees of freedom provides the possibility of adjusting the parameters of nonphysical material absorber (PML) for the purpose of enhancing the attenuation rate of the evanescent modes. Compared to Berenger PML, the MPML is more efficient in absorbing the evanescent

B. Chen; D. G. Fang; B. H. Zhou

1995-01-01

357

Porous metal absorbers for underwater sound.  

PubMed

Rubber has traditionally been used for underwater sound absorption. Porous metal is a relatively lightweight material and also has higher strength than rubber. However, exactly how porous metals can be used as effective underwater sound absorbers remains unclear. This paper shows how to use porous metal absorbers so that they work well under water, even under fairly constrained conditions. A method of nondimensional analysis is proposed that allows identification of vital characteristics. This means that such characteristics can be varied and the absorbers themselves filled with different types of viscous fluids. Such analysis suggests that the sound absorption coefficient of porous metals does not always increase when there are either increases in porosity or decreases in average pore size. The same method of analysis can show how, by choice of the right characteristics to choose a suitable viscous fluid, a porous metal absorber can be built that takes up little space but still effectively absorbs underwater sounds at low frequencies. PMID:18189554

Wang, Xiaolin

2007-11-01

358

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

359

Fifty years of radar  

NASA Astrophysics Data System (ADS)

A development history of radar technology is presented, with attention to the driving of radar system design advances by the emergence of such weapon systems as long range aircraft and cruise missiles in World War II and the range of current applications for state-of-the-art radar techniques. The applications noted encompass over-the-horizon backscatter radars for aircraft detection at 500-1800 nmi ranges, ultralow sidelobe antenna military radars, a long range, frequency scanning three-dimensional S-band radar, a shipborne phased array radar for the collection of exoatmospheric and endoatmospheric data on ballistic missile reentry vehicles, multimission/multimode X-band fighter aircraft radars, and phased array air defense radars.

Skolnik, M. I.

1985-02-01

360

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

361

Two-Iris Method for the Electromagnetic Characterization of Conductor-Backed Absorbing Materials Using an Open-Ended Waveguide Probe  

Microsoft Academic Search

A two-iris waveguide-probe technique is introduced for measuring the electromagnetic properties of a lossy conductor-backed material layer. A flanged open-ended rectangular waveguide is applied to the material under test, and the reflected signal is measured under two conditions. The reflection is first measured when the aperture of the waveguide is unobstructed; then, the reflection is measured with an iris placed

Gary D. Dester; Edward J. Rothwell; Michael J. Havrilla

2012-01-01

362

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

363

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

364

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

365

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

366

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

367

Wide bandwidth pyramidal absorbers of granular ferrite and carbonyl iron powders  

Microsoft Academic Search

Pyramidal absorbers with wide bandwidth in the GHz region are designed with magnetic materials of broad loss spectrum for application to small or semi-anechoic chambers. Microwave absorbing properties of pyramidal cone absorbers are analyzed by the transmission line approximation which provides the reflection loss as a function of material parameters and absorber height. It has been found that the magnetic

Myung-Jun Park; Jaeho Choi; Sung-Soo Kim

2000-01-01

368

Low Frequency Vibration Absorber.  

National Technical Information Service (NTIS)

This patent application discloses a mounting assembly for absorbing low frequency vibrational energy as produced by a source and isolating a base member therefrom. The mounting assembly includes a central metallic ring, non-metallic foam rings located on ...

N. J. Dubois B. G. Gauthier

1990-01-01

369

Radar, Target and Ranging.  

National Technical Information Service (NTIS)

This Test Operations Procedure (TOP) provides conventional test methods employing conventional test instrumentation for testing conventional radars. Single tests and subtests designed to test radar components, transmitters, receivers, antennas, etc., and ...

1984-01-01

370

The MST radar technique  

NASA Technical Reports Server (NTRS)

The coherent radar technique is reviewed with special emphasis to mesosphere-stratosphere-troposphere (MST) radars operating in the VHF band. Some basic introduction to Doppler radar measurements and the radar equation is followed by an outline of the characteristics of atmospheric turbulence, viewed from the scattering and reflection processes of radar signals. Radar signal acquisition and preprocessing, namely coherent detection, digital sampling, pre-integration and coding, is briefly discussed. The data analysis is represented in terms of the correlation and spectrum analysis, yielding the essential parameters: power, signal-to-noise ratio, average and fluctuating velocity and persistency. The techniques to measure wind velocities, viz. the different modes of the Doppler method as well as the space antenna method are surveyed and the feasibilities of the MST radar interferometer technique are elucidated. A general view on the criteria to design phased array antennas is given. An outline of the hardware of a typical MST radar system is presented.

Roettger, J.

1984-01-01

371

Sensor and method for indicating the presence of a low magnetic field using high critical temperature superconductor ceramic material to absorb electromagnetic energy  

Microsoft Academic Search

This patent describes a sensor for use with a source of electromagnetic energy for indicating the presence of a low magnetic field with a sensitivity of at least 10{sup - 10} tesla. It comprises: a sensing element consisting essentially of a high critical temperature superconductor ceramic oxide material without the need for further processing, said critical temperature being above 77°;

Tyagi

1990-01-01

372

Equatorial radar system  

Microsoft Academic Search

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar will be built in Pontianak, West Kalimantan, Indonesia (0.03 deg N, 109.29 deg E). The system is a 47-MHz monostatic Doppler radar with an active phased array configuration

Shoichiro Fukao; Toshitaka Tsuda; Toru Sato; Susumu Kato

1990-01-01

373

Radar observations of asteroids  

NASA Technical Reports Server (NTRS)

The type of information that can be obtained from radar observations of asteroids includes sizes, shapes, spin vectors, and such surface characteristics as the decimeter-scale morphology, topographic relief, regolith porosity, and metal concentration. This paper describes the two radar facilities active in asteroid studies (the Arecibo Observatory in Puerto Rico and the Goldstone Radar in California) and techniques used in radar observations of asteroids. Results available for main-belt and near-earth asteroids are discussed.

Ostro, Steven J.

1989-01-01

374

Fifty years of radar  

Microsoft Academic Search

A development history of radar technology is presented, with attention to the driving of radar system design advances by the emergence of such weapon systems as long range aircraft and cruise missiles in World War II and the range of current applications for state-of-the-art radar techniques. The applications noted encompass over-the-horizon backscatter radars for aircraft detection at 500-1800 nmi ranges,

M. I. Skolnik

1985-01-01

375

Harmonic Radar Literature Harmonisk Radar - en Litteraturstudie.  

National Technical Information Service (NTIS)

A harmonic radar sends on a given frequency f sub o and receives on another frequency usually 3 f sub o. The overtone is generated on joints between the metal parts of the radar target. The generated high harmonic frequency is very weak, which is why this...

B. Jansson

1980-01-01

376

Harmonic radar literature  

Microsoft Academic Search

A harmonic radar sends on a given frequency f sub o and receives on another frequency usually 3 f sub o. The overtone is generated on joints between the metal parts of the radar target. The generated high harmonic frequency is very weak, which is why this radar has an extremely low range of detection. Natural objects in the target

B. Jansson

1980-01-01

377

Radar cross section measurements  

Microsoft Academic Search

The present status of radar cross section (RCS) measurements is addressed. The fundamental considerations and definitions associated with RCS measurements are reviewed, including radar waveform, polarization requirements, far-field requirements, and target dimensional scaling. Different types of measurement facilities are examined, including their range geometries, target support systems, calibration standards, and facility evaluation. Instrumentation radar requirements and designs are reviewed, and

Robert B. Dybdal

1987-01-01

378

Automatic Radar Waveform Recognition  

Microsoft Academic Search

In this paper, a system for automatically recognizing radar waveforms is introduced. This type of techniques are needed in various spectrum management, surveillance and cognitive radio or radar applications. The intercepted radar signal is classified to eight classes based on the pulse compression waveform: linear frequency modulation (LFM), discrete frequency codes (Costas codes), binary phase, and Frank, P1, P2, P3,

Jarmo Lundn; Visa Koivunen

2007-01-01

379

Radar Meteorology Tutorial  

NSDL National Science Digital Library

Brian McNoldy at Multi-community Environmental Storm Observatory (MESO) educates the public about the use of radar in meteorology in this pdf document. After reading about the history of radar, visitors can find out how radar can detect storms by transmitting a high-power beam of radiation. Students can learn how scatter, absorption, frequencies, scan angles, and moments impact the radar display. With the help of many example images, the author also discusses how to interpret the images collected. At the end of the online document, visitors can learn about the characteristics and capabilities of NEXRAD WSR-88D, the radar used throughout the United States.

Mcnoldy, Brian

2007-08-16

380

A hybrid mesoporous material functionalized by 1,8-naphthalimide-base receptor and the application as chemosensor and absorbent for Hg2+ in water.  

PubMed

A novel hybrid material (SBA-P1) is prepared through the functionalization of mesoporous silica (SBA-15) with a 1,8-naphthalimide-based dye by sol-gel reaction. The characterization results of elemental analysis (EA), X-ray powder diffractometer (XRD) and spectroscopic methods demonstrate the fluorescence dye P1 is successfully grafted onto the inner surface of SBA-15 and the organized structure is preserved. SBA-P1 can detect Hg(2+) with high selectivity to Cu(2+), Zn(2+), Cd(2+), Pb(2+), Mn(2+), Ni(2+), Co(2+), Ag(+), Cr(3+), and Mg(2+), Ca(2+), Li(+), Na(+), K(+) in water and sensitivity to environmentally relevant mercury in complex natural samples. The quenching fluorescence detection is also reversible by treating with EDTA/base. Furthermore, its fluorescence intensity keeps stable in the physiologically relevant pH range. The extraction ability of SBA-P1 is also estimated by inductively coupled plasma source mass spectrometer (ICP), showing that approximately 90% of the Hg(2+) ion is extracted. These results imply that the hybrid material has potential application for sensing and removing of Hg(2+) ions in waste water and working as toxicide for acute mercury poisoning. PMID:21315897

Meng, Qingtao; Zhang, Xiaolin; He, Cheng; Zhou, Peng; Su, Weiping; Duan, Chunying

2011-03-15

381

Multidimensional radar picture  

NASA Astrophysics Data System (ADS)

In marine navigation systems, the three-dimensional (3D) visualization is often and often used. Echosonders and sonars working in hydroacustic systems can present pictures in three dimensions. Currently, vector maps also offer 3D presentation. This presentation is used in aviation and underwater navigation. In the nearest future three-dimensional presentation may be obligatory presentation in displays of navigation systems. A part of these systems work with radar and communicates with it transmitting data in a digital form. 3D presentation of radar picture require a new technology to develop. In the first step it is necessary to compile digital form of radar signal. The modern navigation radar do not present data in three-dimensional form. Progress in technology of digital signal processing make it possible to create multidimensional radar pictures. For instance, the RSC (Radar Scan Converter) - digital radar picture recording and transforming tool can be used to create new picture online. Using RSC and techniques of modern computer graphics multidimensional radar pictures can be generated. The radar pictures mentioned should be readable for ECDIS. The paper presents a method for generating multidimensional radar picture from original signal coming from radar receiver.

Waz, Mariusz

2010-05-01

382

Radar attenuation in desert soil  

NASA Astrophysics Data System (ADS)

Soil properties make a significant impact in the observed responses of various sensors for subsurface target detection. Ground penetrating radars (GPRs) have been extensively researched as a tool for subsurface target detection. A key soil parameter of interest for evaluating GPR performance is the soil attenuation rate. The information about the soil attenuation rate coupled with target properties (size, shape, material properties and depth of burial) can be used to estimate the effectiveness of radar sensors in a particular soil environment. Radar attenuation in desert soil is of interest in today's political and military climate. Laboratory measurements of desert soil attenuation were conducted using samples collected from a desert in Southwestern United States and in Iraq. These measurements were made in a coaxial waveguide over the frequency ranging from 250 MHz to 4 GHz. The soil grain size distribution, mineralogy, moisture and salinity were also measured. This report describes the experimental procedure and presents the radar attenuation rates observed in desert soils. The results show that the soluble salt content is an important parameter affecting the attenuation behavior of desert soils.

Koh, Gary

2008-05-01

383

Shock absorber servicing tool  

NASA Technical Reports Server (NTRS)

A tool to assist in the servicing of a shock absorber wherein the shock absorber is constructed of a pair of aligned gas and liquid filled chambers. Each of the chambers is separated by a movable separator member. Maximum efficiency of the shock absorber is achieved in the locating of a precise volume of gas within the gas chamber and a precise volume of liquid within the liquid chamber. The servicing tool of this invention employs a rod which is to connect with the separator and by observation of the position of the rod with respect to the gauge body, the location of the separator is ascertained even though it is not directly observable.

Koepler, Jack L. (Inventor); Hill, Robert L. (Inventor)

1981-01-01

384

A practical millimeter-wave radar calibration target  

Microsoft Academic Search

A simple rectangular-plate millimeter-wave radar calibration target gives RCS values ranging from hundreds to thousands of square meters. This enable tests over extended ranges and with equipment having modest output power. Precise mechanical alignment mechanisms and an optical sight are mandatory, due to the narrow beamwidth. Absorber collars provide an easy way of adjusting the actual RCS according to specific

J. Ruoskanen; P. Eskeffnen; H. Heikkila; P. Kuosmanen; T. Kiuru

2004-01-01

385

Topics for a statistical description of radar cross section  

Microsoft Academic Search

A comprehensive guide to the statistical description of radar cross section (RCS) is presented. The topics discussed include: definition of field quantities and Maxwell's equations, constitutive relations, boundary conditions and surface currents, Green's functions, diffraction of a plane wave by a perfectly absorbing half-plane, asymptotic approximation methods, and diffraction approximation methods. Also considered are: numerical approximations and numerical methods, RCS

Andrew Lewis Maffett

1989-01-01

386

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Efficiency of ablative loading of material upon the fast-electron transfer of absorbed laser energy  

NASA Astrophysics Data System (ADS)

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 ?m) with an energy of 360 J. The greater part of the experiments were performed for the radiation intensity exceeding 1015 W cm-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.

Gus'kov, Sergei Yu; Kasperczuk, A.; Pisarczyk, T.; Borodziuk, S.; Kalal, M.; Limpouch, J.; Ullschmied, J.; Krousky, E.; Masek, K.; Pfeifer, M.; Rohlena, K.; Skala, J.; Pisarczyk, P.

2006-05-01

387

Absorbed dose water calorimeter  

Microsoft Academic Search

An absorbed dose water calorimeter that takes advantage of the low thermal diffusivity of water and the water-imperviousness of polyethylene film. An ultra-small bead thermistor is sandwiched between two thin polyethylene films stretched between insulative supports in a water bath. The polyethylene films insulate the thermistor and its leads, the leads being run out from between the films in insulated

Domen

1982-01-01

388

Burnable neutron absorbers  

Microsoft Academic Search

Method of making a burnable neutron absorber of boron carbide in a matrix of aluminum oxide. In the practice of this method, boron-carbide particles are coated with a pore former and then they are mixed in a slurry with aluminum oxide powder. When the slurry is subsequently dried and sintered, the pore former is burned out and a body is

B. M. Argall; P. J. Kuchirka; K. C. Radford

1985-01-01

389

A Shock Absorber.  

National Technical Information Service (NTIS)

The invention involves a shock absorber consisting of a cylindrical housing (containing a coaxially placed guide cylinder forming a working space equipped with by-pass apertures), a chamber (formed by the housing and the floating piston), and a working pi...

N. N. Rakhmanov

1969-01-01

390

Lifetimes of Saturable Absorbers  

Microsoft Academic Search

THE use of saturable absorbers such as aluminium phthalocyanine for the passive Q-switching of ruby lasers1 raises the question of the lifetime of the active molecule. We have measured the lifetime of that state of aluminium phthalocyanine which corresponds to absorption at or near 6943 Å. Similar data for magnesium phthalocyanine have been obtained, for comparison with literature values.

P. W. A. Bowe; W. E. K. Gibbs; J. Tregellas-Williams

1966-01-01

391

Apollo experience report: Lunar module landing radar and rendezvous radar  

NASA Technical Reports Server (NTRS)

A developmental history of the Apollo lunar module landing and rendezvous radar subsystems is presented. The Apollo radar subsystems are discussed from initial concept planning to flight configuration testing. The major radar subsystem accomplishments and problems are discussed.

Rozas, P.; Cunningham, A. R.

1972-01-01

392

Analysis of Old Copper Synchrotron Light Absorbers from the Stanford Positron Electron Accelerating Ring  

Microsoft Academic Search

Synchrotron light absorbers intercept synchrotron radiation to protect chamber walls from excessive heat. When subjected to the high temperature of the beam, these absorbers undergo thermal stress. If the stress is too great or fatigues the material, the absorbers may fail. These absorbers are designed to last the lifetime of the machine. Any premature cracking could result in a leak

S. R. Marshall; B. Scott

2005-01-01

393

Translatory shock absorber for attitude sensors  

NASA Technical Reports Server (NTRS)

A translatory shock absorber is provided for mounting an attitude sensor thereon for isolating a sensor from translatory vibrations. The translatory shock absorber includes a hollow block structure formed as one piece to form a parallelogram. The absorber block structure includes a movable top plate for supporting the attitude sensor and a fixed base plate with opposed side plates interposed between. At the junctions of the side plates, and the base and top plates, there are provided grooves which act as flexible hinges for attenuating translatory vibrations. A damping material is supported on a pedestal which is carried on the base plate between the side plates thereof. The top of the damping material rests against the bottom surface of the top plate for eliminating the resonant peaks of vibration.

Vonpragenau, G. L.; Morgan, I. T., Jr.; Kirby, C. A. (inventors)

1976-01-01

394

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

395

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

396

RCS analysis of canonical, two-dimensional material-loaded cavities with rectangular and circular cross sections  

Microsoft Academic Search

A rigorous radar cross section (rcs) analysis of canonical, two-dimensional material-loaded cavities with rectangular and\\u000a circular cross sections is carried out using the Wiener-Hopf technique and the Riemann-Hilbert problem technique, respectively.\\u000a Both E and H polarizations are treated. It is shown via numerical examples that the absorbing layer loading inside the cavities\\u000a gives rise to the significant rcs reduction. The

Kazuya Kobayashi; Alexander I. Nosich

1995-01-01

397

Multifunction laser radar: II  

NASA Astrophysics Data System (ADS)

Laser radar systems are required for various military applications including obstacle detection, target recognition, and terrain mapping. Each application requires different system parameters such as pulse energy, repetition rate, and field of view. This paper is the second in a series of papers describing the progress toward a multifunction laser radar system under construction for the Cooperative Eyesafe Laser Radar Program (CELRAP) of the U.S. Army CECOM Night Vision and Electronic Sensors Directorate.

Hutchinson, James A.; Trussell, Charlie W.; Allik, Toomas H.; Hamlin, Scott J.; McCarthy, John C.; Jack, Michael D.

2000-09-01

398

Radar Imaging and Feature Extraction.  

National Technical Information Service (NTIS)

Advanced spectral estimation methods are presented for radar imaging and target feature extraction. We study problems involved in inverse synthetic aperture radar (ISAR) autofocus and imaging, synthetic aperture radar (SAR) autofocus and motion compensati...

J. Li

1999-01-01

399

Stepped Frequency Imaging Radar Simulation.  

National Technical Information Service (NTIS)

In this thesis, a technique involving Stepped Frequency and Inverse Synthetic Aperture Radar (ISAR) processing have been employed to develop two- dimensional radar images of an aircraft target. Radar returns from prominent scatterers of various parts of t...

K. L. Mun

2000-01-01

400

Landform Identification: Lunar Radar Images.  

National Technical Information Service (NTIS)

Three sets of polarized radar-echo images of the Moon were examined to establish the relation between radar resolution and landform-identification resolution. After comparison with lunar maps and photographs, real and apparent landforms on the radar image...

H. J. Moore T. W. Thompson

1987-01-01

401

Equatorial radar system  

NASA Astrophysics Data System (ADS)

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar, called the Equatorial Radar, will be built in Pontianak, Kalimantan Island, Indonesia (0.03 N, 109.3 E). The system is a 47 MHz monostatic Doppler radar with an active phased array configuration similar to that of the MU radar in Japan, which has been in successful operation since 1983. It will have a PA product of more than 5 x 10(9) sq. Wm (P = average transmitter power, A = effective antenna aperture) with sensitivity more than 10 times that of the MU radar. This system configuration enables pulse-to-pulse beam steering within 25 deg from the zenith. As is the case of the MU radar, a variety of sophisticated operations will be made feasible under the supervision of the radar controller. A brief description of the system configuration is presented.

Rukao, S.; Tsuda, T.; Sato, T.; Kato, S.

1989-04-01

402

Equatorial radar system  

NASA Technical Reports Server (NTRS)

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar, called the Equatorial Radar, will be built in Pontianak, Kalimantan Island, Indonesia (0.03 N, 109.3 E). The system is a 47 MHz monostatic Doppler radar with an active phased array configuration similar to that of the MU radar in Japan, which has been in successful operation since 1983. It will have a PA product of more than 5 x 10(9) sq. Wm (P = average transmitter power, A = effective antenna aperture) with sensitivity more than 10 times that of the MU radar. This system configuration enables pulse-to-pulse beam steering within 25 deg from the zenith. As is the case of the MU radar, a variety of sophisticated operations will be made feasible under the supervision of the radar controller. A brief description of the system configuration is presented.

Rukao, S.; Tsuda, T.; Sato, T.; Kato, S.

1989-01-01

403

Harmonic radar literature  

NASA Astrophysics Data System (ADS)

A harmonic radar sends on a given frequency f sub o and receives on another frequency usually 3 f sub o. The overtone is generated on joints between the metal parts of the radar target. The generated high harmonic frequency is very weak, which is why this radar has an extremely low range of detection. Natural objects in the target area do not disturb the high frequency harmonics. The radar becomes clutter free. The principals of generating high frequency harmonics cover tunneling, semiconductor and microwave effects. Signal generation is most powerful when f sub o is between 100 and 1000 MHz.

Jansson, B.

1980-07-01

404

Electronic Materials Based on Co0.5Zn0.5Fe2O4/Pb(Zr0.52Ti0.48)O3 Nanocomposites  

NASA Astrophysics Data System (ADS)

The reduction of the radar cross-sectional area achieved in stealth technology has been a major challenge since the Second World War, being accomplished by covering the metallic surfaces of aircraft, ships, tanks, etc. with radar-absorbing materials. Nowadays, the development of lightweight microwave-absorbing materials with reduced thickness has a greater impact due to their excellent microwave-absorbing properties. In this study, the microwave-absorbing properties of nanocomposites based on Zn-substituted cobalt ferrite and lead zirconium titanate have been investigated in the X-band (8.2 GHz to 12.4 GHz) region. Zn-substituted cobalt ferrite (CZF) and lead zirconium titanate (PZT) nanoparticles were prepared by the coprecipitation and homogeneous precipitation method, respectively. Nanocomposites were developed by dispersing these nanoparticles with different compositions into an epoxy resin matrix. All the composite materials showed more than 90% microwave absorption in the X-band region. The nanocomposite containing CZF/PZT (3:1) with 2 mm thickness displayed maximum return loss of -47.87 dB at 12.23 GHz. The microwave absorbers based on epoxy resin polymeric matrix exhibited better absorbing properties when the dielectric contribution matched the magnetic contribution, and the loss mechanisms were mainly due to the dielectric loss.

Mandal, Avinandan; Das, Chapal Kumar

2013-01-01

405

Shock absorbing mount for electrical components  

NASA Technical Reports Server (NTRS)

A shock mount for installing electrical components on circuit boards is described. The shock absorber is made of viscoelastic material which interconnects the electrical components. With this system, shocks imposed on one component of the circuit are not transmitted to other components. A diagram of a typical circuit is provided.

Dillon, R. F., Jr.; Mayne, R. C. (inventors)

1975-01-01

406

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

407

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

408

Shock absorber in Ignalina NPP.  

National Technical Information Service (NTIS)

Theoretical calculation and experimental analysis of models of shock absorber in Ignalina NPP is presented. The results obtained from the investigation with model of shock absorber coincide with the theoretical calculation. (author). 2 figs., 3 refs. (Ato...

A. Bulavas J. Muralis

1996-01-01

409

Broad-band characterization of the complex permittivity and permeability of materials  

SciTech Connect

By employment of state-of-the-art Vector Network Analyzers, and other wide-band measurement equipment and techniques, the authors have the capability of measuring the complex permittivity and permeability of materials, for frequencies ranging from several tens of Kilohertz up to several Gigahertz. Measurement methods and equations for numerical determination are based on recommendations by the National Institute of Standards and Technology (NIST). Types of materials which can be analyzed are dielectric or magnetic RF and radar absorbers; thin sheets, paints, coatings; castable resins; foams and low density materials; ceramics and ferrites; carbonized fabrics; and composites.

Avalle, C.A. [Lawrence Livermore National Lab., CA (United States). Electromagnetics and Diagnostics Group

1994-11-01

410

SELECTIVE ABSORBER COATED FOILS FOR SOLAR COLLECTORS  

SciTech Connect

Solar absorber metal foils are discussed in terms of materials and basic processing science. Also included is the use of finished heavy sheet stock for direct fabrication of solar collector panels. Both the adhesives and bonding methods for foils and sheet are surveyed. Developmental and representative commercial foils are used as illustrative examples. As a result it was found that foils can compete economically with batch plating but are limited by adhesive temperature stability. Also absorber foils are very versatile and direct collector fabrication from heavy foils appears very promising.

Lampert, Carl M.

1980-04-01

411

Active radar stealth device  

Microsoft Academic Search

This patent discloses an active radar stealth device mounted on a host platform for minimizing the radar cross-section of the host platform. A coating which is essentially microwave transparent is attached to the surface of a host platform and is exposed to an incident microwave field. A plurality of detector\\/emitter pairs contained within the coating detect and actively cancel, respectively,

R. N. Cain; Albert J. Corda

1991-01-01

412

Researches on radar technology  

Microsoft Academic Search

In Electronic Systems Research Center (ESRC), various researches have been conducted to realize defense radars with excellent functions and performance. This presentation introduces some of those radar research programs. Especially, the research concerning active phased array antenna started in an early stage of the 1970s. Successive various basic research programs have been conducted and finally led to successful development of

T. Itoh

2009-01-01

413

Equatorial radar system  

NASA Astrophysics Data System (ADS)

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar will be built in Pontianak, West Kalimantan, Indonesia (0.03 deg N, 109.29 deg E). The system is a 47-MHz monostatic Doppler radar with an active phased array configuration similar to that of the MU radar in Japan, which has been in successful operation since 1983. It will have a PA product of about 3 x 10 to the 9th W sq m (P = average transmitter power, A = effective antenna aperture) with a sensitivity of approximately 10 times that of the MU radar. This system configuration enables pulse-to-pulse beam steering within 20 deg from the zenith. As is the case of the MU radar, a variety of operations will be made feasible under the supervision of the radar controller. A brief description of the system configuration is presented.

Fukao, Shoichiro; Tsuda, Toshitaka; Sato, Toru; Kato, Susumu

414

The Cloud Radar System  

NASA Technical Reports Server (NTRS)

Improvement in our understanding of the radiative impact of clouds on the climate system requires a comprehensive view of clouds including their physical dimensions, dynamical generation processes, and detailed microphysical properties. To this end, millimeter vave radar is a powerful tool by which clouds can be remotely sensed. The NASA Goddard Space Flight Center has developed the Cloud Radar System (CRS). CRS is a highly sensitive 94 GHz (W-band) pulsed-Doppler polarimetric radar that is designed to fly on board the NASA high-altitude ER-2 aircraft. The instrument is currently the only millimeter wave radar capable of cloud and precipitation measurements from above most all clouds. Because it operates from high-altitude, the CRS provides a unique measurement perspective for cirrus cloud studies. The CRS emulates a satellite view of clouds and precipitation systems thus providing valuable measurements for the implementation and algorithm validation for the upcoming NASA CloudSat mission that is designed to measure ice cloud distributions on the global scale using a spaceborne 94 GHz radar. This paper describes the CRS instrument and preliminary data from the recent Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE). The radar design is discussed. Characteristics of the radar are given. A block diagram illustrating functional components of the radar is shown. The performance of the CRS during the CRYSTAL-FACE campaign is discussed.

Racette, Paul; Heymsfield, Gerald; Li, Lihua; Tian, Lin; Zenker, Ed

2003-01-01

415

Digital LPI Radar Detector.  

National Technical Information Service (NTIS)

The function of a Low Probability of Intercept (LPI) radar is to prevent its interception by an Electronic Support (ES) receiver. This objective is generally achieved through the use of a radar waveform that is mismatched to those waveforms for which an E...

P. G. Ong H. K. Teng

2001-01-01

416

HWL radar system analysis  

Microsoft Academic Search

Research is reported relating to the weapons-location problem as it relates to Marine Corps Hostile Weapons Locating (HWL) radar and lightweight mortar locator requirements. Several technical system problems are discussed, including a review of the HWL system mechanical design. A detailed description is also given of the EES computer modeling program (ballistic trajectory model and radar operational simulation) that was

F. R. Williamson; R. R. Sheppard; C. E. Summers; E. K. Reedy

1976-01-01

417

Advances in Radar Techniques  

NASA Astrophysics Data System (ADS)

Most of the clutter received by L, S, C, X, and Ku band radars obeys a Weibull ditribution. To suppress such Weibull-distributed sea and weather clutter, Weibull CFAR techniques are applied to data taken by an X-band radar using computer in real time. The results show the usefulness of Weibull CFAR.

Sekine, Matsuo

418

F-22 radar development  

Microsoft Academic Search

The USAF F-22 Engineering, Manufacturing and Development (EMD) program has pushed the state of airborne fire control radar technology well beyond that found in today's fielded systems. Advancements in performance, reliability, and low observability have been realized in the design of the F-22's new APG-77 Radar through the implementation of active array technology, low noise receiver components, high density packaging,

J. A. Malas

1997-01-01

419

Chaotic signals in radar?  

Microsoft Academic Search

Chaotic signals add to the design repertoire for radar. This paper discusses the properties of chaotic signals, their generation and use, including transmitter hardware and efficiency, with reference to results in communications research and recent theoretical and practical results in sonar, and development throughout the world for radar. Practical issues arising from the unique properties of chaotic systems are considered.

S. A. Harman; A. J. Fenwick; C. Williams

2006-01-01

420

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

421

Decoders for MST radars  

NASA Technical Reports Server (NTRS)

Decoding techniques and equipment used by MST radars are described and some recommendations for new systems are presented. Decoding can be done either by software in special-purpose (array processors, etc.) or general-purpose computers or in specially designed digital decoders. Both software and hardware decoders are discussed and the special case of decoding for bistatic radars is examined.

Woodman, R. F.

1983-01-01

422

Radar applications overview  

Microsoft Academic Search

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

Marshall Greenspan

1996-01-01

423

Radar - The Future  

Microsoft Academic Search

Progress in civil and military radar units since the invention of radar in 1935 is summarized, noting the trend to multipurpose units. The earliest systems functioned at 10 cm, then 3 cm after development of a cavity magnetron to provide power for shorter wavelengths. Military needs are driving improvements in three-dimensional scanning capabilities, Primarily to locate aircraft in the presence

G. Warwick

1985-01-01

424

Radar Frequency Radiation.  

National Technical Information Service (NTIS)

A method is presented for the determination of radar frequency radiation power densities that the PAVE PAWS radar system could produce in its air and ground environment. The effort was prompted by the concern of the people in the vicinity of OTIS AFB MA a...

E. Malowicki

1981-01-01

425

Machine for Testing Shock Absorbers.  

National Technical Information Service (NTIS)

The machine is for testing shock absorbers used in tanks, personnel carriers, and like vehicles. A shock absorber is tested by mounting it on one end of a piston which is reciprocated by hydraulic fluid under pressure. The other end of the shock absorber ...

E. W. Posse C. E. Rutledge

1964-01-01

426

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

427

Looking at Radar Images  

NSDL National Science Digital Library

These activities pertain to the value of the different types of images, including a false color mosaic, a Compressed Stokes image, a vegetation map and key, and various ground photographs. Students are given specific directions on how to decide what features of a radar image indicate such structures as upland forest, clear-cut areas, and roads. In a second activity, students look at the radar images to see if they can produce a vegetation map similar to the one they have been given. The third activity introduces 15 Decade Volcanoes that pose a particular threat to humans. Using the Decade Volcanoes as examples, students view radar images of volcanoes that occur around the world. The final exercise is aimed at helping students distinguish the differences between radar image data and visible photographs. Students will look at radar data and photographs of three sites taken by the astronauts.

428

Radar Cross Section (RCS) Data Base Deduced from Radar Images.  

National Technical Information Service (NTIS)

The creation of radar cross section (RCS) catalogs using existing radar images is discussed. Analysis of SIR-B images shows that spatial resolution has a significant impact on the radar data information content. Interpretation of radar data must be based ...

A. J. Sieber

1986-01-01

429

Spatial-frequency multiplication via absorbance modulation  

SciTech Connect

The absorbance of a thin film of photochromic material can be reversibly modified by exposure to two different wavelengths, {lambda}{sub 1} and {lambda}{sub 2}. When such a film is illuminated by both wavelengths simultaneously, and the longer wavelength {lambda}{sub 2} possesses a node in its intensity distribution, then the absorbance of the layer can be made high except at an arbitrarily small region near the node. By exploiting the large nonlinearity introduced by this mechanism, combined with the reversibility of the absorbance of the photochromic layer, the authors demonstrate that spatial frequencies larger than those present in incident intensity distributions may be generated. They show photoresist exposures to demonstrate this technique.

Tsai, H.-Y.; Wallraff, Gregory M.; Menon, Rajesh [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); IBM Almaden Research Center, San Jose, California 95120 (United States); Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 and LumArray, Inc., Somerville, Massachusetts 02143 (United States)

2007-08-27

430

Hafnium as a neutron absorber in research reactors  

Microsoft Academic Search

Research reactors usually require the periodic replacement of control rods because of the burnup of the neutron absorber material, even if devices have been mainly withdrawn. The purpose of this paper is the study of the reactivity worth of hafnium as a neutron absorber in the multi-purpose-type research reactor (MPTRR). The MPTRR design develops 20 MW, and it is configured

F. E. Jatuff; E. A. Villarino

1995-01-01

431

A Study of Resonant Absorbers for Underwater Sound.  

National Technical Information Service (NTIS)

In the first part of the work a simple model of a resonant absorber is proposed from which is derived an expression relating the acoustic impedance at the surface of the absorber with the dynamic modulus of the material from which it is made. Results are ...

W. Meeks

1965-01-01

432

Selective absorbers from substituted magnetite-based coatings  

Microsoft Academic Search

Selective solar absorbers have been prepared for industrial applications with an original treatment -- chemical conversion of the surface -- of ferritic stainless steels. They present a high solar absorbance ((alpha) s approximately equals 0.95), a low emittance ((xi) approximately equals 0.20), a high thermal stability, and a high resistance to corrosion by atmospheric agents. Characteristics of the material have

Jean P. Traverse

1992-01-01

433

Experimental optimization of composite collapsible tubular energy absorber device  

Microsoft Academic Search

A four-phase program to improve the specific energy absorbed by axially crushed composite collapsible tubular energy absorber devices was undertaken. In the first phase, examining of the crushing behaviour of non-triggered tubes was carried out. The second phase is aimed at obtaining the best position for the triggered wall. The third phase focuses on the effects of material sizing in

E. Mahdi; H. Sultan; A. M. S. Hamouda; A. A. Omer; A. S. Mokhtar

2006-01-01

434

Optimization and engineering of microwave absorbers  

NASA Astrophysics Data System (ADS)

In this thesis, a concerted effort has been made to study and evaluate the individual electromagnetic properties of the absorbing components including carbon black, conducting fibers, metal flakes, magnetic materials such as carbonyl iron, ferrite and the chiral type of micro- carbon coil. The study of the electromagnetic properties covers functions such as dielectric dissipation, random scattering effect at low and high frequencies, magnetic dissipation at high frequencies and also the effect of chirality for different angles of incidence. The results of these studies have been used in the design, engineering and optimization of the microwave absorbers. The objective of this thesis is to identify the absorption mechanism of each of various type of fillers and to study the synergic effect arising from a combination of these in a non-metallic host medium. This will help us in producing microwave absorbers suitable for broad band application with the advantages of light weight, having high strength and possessing good chemical resistance. The results from experimental measurements of various material combinations have been greatly influenced by the theoretical understanding of the absorption mechanism. Design of microwave absorbers is governed by the requirement of the users as well as the characteristics of the objects (targets) inferred by theoretical understanding and experimental data to arrive at the right formula. Finally a detailed quality control program has to be charted out reflecting both the electromagnetic as well as mechanical properties. This is done by carrying out the tests systematically on small samples and then proceeding to practical absorbers making use of the data compiled earlier on smaller samples. In this thesis, to modify all dielectric absorbing components including micro-carbon chirals to reduce the sensitivity of absorption for different incident angles is unprecedented topic.

Chen, Kuo-Liang

1998-12-01

435

FMCW radars for snow research  

Microsoft Academic Search

Frequency Modulated Continuous Wave (FMCW) radars have been used by snow scientists for the past 30 years. This radar technology provides a promising alternative to point measurements, as properties such as snow depth can be measured quickly and non-destructively. Recent advances in microwave FMCW radar technology have resulted in lightweight, portable instrumentation. This is in contrast to the early FMCW radar

Hans-Peter Marshall; Gary Koh

2008-01-01

436

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

437

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

438

Radar frequency radiation  

NASA Astrophysics Data System (ADS)

A method is presented for the determination of radar frequency radiation power densities that the PAVE PAWS radar system could produce in its air and ground environment. The effort was prompted by the concern of the people in the vicinity of OTIS AFB MA and BEALE AFB CA about the possible radar frequency radiation hazard of the PAVE PAWS radar. The method is based on the following main assumptions that: (a) the total field can be computed as the vector summation of the individual fields due to each antenna element; (b) the individual field can be calculated using distances for which the field point is in the far field of the antenna element. An RFR computer program was coded for the RADC HE 6180 digital computer and exercised to calculate the radiation levels in the air and ground space for the present baseline and the possible Six DB and 10 DB growth systems of the PAVE PAWS radar system at OTIS AFB MA. The average radiation levels due to the surveillance fence were computed for three regions: in the air space in front of the radar, at the radar hazard fence at OTIS AFB MA and at representative ground points in the OTIS AFB vicinity. It was concluded that the radar frequency radiation of PAVE PAWS does not present a hazard to personnel provided there is no entry to the air hazard zone or to the area within the hazard fence. The method developed offers a cost effective way to determine radiation levels from a phased array radar especially in the near field and transition regions.

Malowicki, E.

1981-11-01

439

RADAR IMAGING FOR COMBATTING TERRORISM  

Microsoft Academic Search

Radar, and in particular imaging radar, have many and varied applications to counterterrorism. Radar is a day\\/night all-weather\\u000a sensor, and imaging radars carried by aircraft or satellites are routinely able to achieve high-resolution images of target\\u000a scenes, and to detect and classify stationary and moving targets at operational ranges. Short-range radar techniques may be\\u000a used to identify small targets, even

Hugh D. Griffiths; Chris J. Baker

440

Multitone harmonic radar  

NASA Astrophysics Data System (ADS)

Nonlinear radar exploits the electronic response from a target whose reflected frequencies are different from those transmitted. Reception of frequencies that are not part of the transmitted probe distinguishes the received signal from a linear return produced by clutter and indicates the presence of electronics. Presented in this paper is a type of nonlinear radar that transmits multiple frequencies and listens for a harmonic of these frequencies as well as other frequencies near that harmonic. A laboratory test-bed has been constructed to demonstrate the multitone radar concept. Measurements of nonlinear responses from RF devices probed by multiple tones are reported.

Mazzaro, Gregory J.; Martone, Anthony F.

2013-05-01

441

A microprogrammable radar controller  

NASA Technical Reports Server (NTRS)

The Wave Propagation Lab. has completed the design and construction of a microprogrammable radar controller for atmospheric wind profiling. Unlike some radar controllers using state machines or hardwired logic for radar timing, this design is a high speed programmable sequencer with signal processing resources. A block diagram of the device is shown. The device is a single 8 1/2 inch by 10 1/2 inch printed circuit board and consists of three main subsections: (1) the host computer interface; (2) the microprogram sequencer; and (3) the signal processing circuitry. Each of these subsections are described in detail.

Law, D. C.

1986-01-01

442

New airborne Doppler radar  

NASA Astrophysics Data System (ADS)

U.S. and French research establishments will build and share an airborne Doppler radar that they will design to gather data on large-scale storm structures and global atmospheric processes.The University Corporation for Atmospheric Research (UCAR), Boulder, Colo., the Centre National d'Etudes des Telecommunications (CNET) and the Institut National des Sciences de l'Univers in Paris, France, have signed an $11 million agreement for joint development, operation and research use of the radar. The scheduled completion date of the Electra Doppler Radar (ELDORA) system is November 1, 1992.

443

Radar Remote Sensing  

NASA Technical Reports Server (NTRS)

This lecture was just a taste of radar remote sensing techniques and applications. Other important areas include Stereo radar grammetry. PolInSAR for volumetric structure mapping. Agricultural monitoring, soil moisture, ice-mapping, etc. The broad range of sensor types, frequencies of observation and availability of sensors have enabled radar sensors to make significant contributions in a wide area of earth and planetary remote sensing sciences. The range of applications, both qualitative and quantitative, continue to expand with each new generation of sensors.

Rosen, Paul A.

2012-01-01

444

Covert situational awareness with handheld ultrawideband short-pulse radar  

NASA Astrophysics Data System (ADS)

Law enforcement and emergency services all face the difficult task of determining the locations of people within a building. A handheld radar able to detect motion through walls and other obstructions has been developed to fill this need. This paper describes the attributes and difficulties of the radar design and includes test results of the radar's performance. This discussion begins by summarizing key user requirements and the electromagnetic losses of typical building materials. Ultra-wideband (UWB) short pulse radars are well suited for a handheld sensor primarily because of their inherit time isolation in high clutter environments and their capability to achieve high resolution at low spectral center frequencies. There are also constraints that complicate the system design. Using a technique referred to as time-modulation allows the radars to reject range ambiguities and enhances electromagnetic compatibility with similar radars and ambient systems. An outline of the specifications of the radar developed and a process diagram on how it generates a motion map showing range and direction of the people moving within structures is included. Images are then presented to illustrate its performance. The images include adults, child, and a dog. The test results also include data showing the radar's performance through a variety of building materials.

Barnes, Mark A.; Nag, Soumya; Payment, Tim

2001-08-01

445

Solar energy absorbing panel  

SciTech Connect

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 interconnected side-by-side, generally u-shaped sections, with the adjacent sides of adjacent sections forming parallel fins which facilitate transfer of heat to air passed therealong. Also, slot means are provided at one end edge of the panel which is adapted to receive the other end edge of another like panel therein, whereby the panels may be joined in an end-to-end arrangement.

McArthur, W.H.

1981-09-01

446

Radar cross section computation of inhomogeneous scatterers using edge-based finite element methods in frequency and time domains  

Microsoft Academic Search

This paper presents a flexible, body-conforming finite element modeling technique, using Whitney's edge and face basis functions, for efficient computation of radar cross section (RCS) of inhomogeneous scatterers, both in the frequency and time domains. The vector absorbing boundary conditions, originally developed for a spherical absorbing boundary, are generalized for planar and cylindrical boundaries. The computational resources required for the

K. Mahadevan; R. Mittra

1993-01-01

447

Nonlinear absorbance effects in bacteriorhodopsin  

NASA Astrophysics Data System (ADS)

Bacteriorhodopsin (BR) is a protein found in the cell membrane wall of Halobacterium halobium and serves as a light-activated proton pump (i.e., the protein converts light energy into chemical energy). The chromophore (retinal) responsible for light absorption is located within a pocket of the opsin and is bound via a Schiff base to a lysine residue in the amino acid sequence. When BR is illuminated by a laser light flash, transient changes occur in the visible absorption spectrum of the protein -- i.e., the material is photochromic. The optical absorption changes are characterized by a series of photointermediates, with characteristic rise and fall times that range from less than a picosecond to more then 10 milliseconds. This photochromic property of BR makes it a useful material for optical devices. With an aim toward developing an optical switch for the Army, we are studying the transient absorption of nanosecond light pulses from a dye laser in the spectral region in which the absorbance of BR increases as light intensity increases. This nonlinear effect is wavelength-dependent and becomes a bleach in a different spectral window. The nonlinear absorption change is reversible.

Rayfield, George W.

1991-03-01

448

RADAR performance experiments  

NASA Technical Reports Server (NTRS)

Theoretical studies and experimental results obtained at Coulommiers airport showed the capability of Proust radar to detect wind shears, in clear air condition as well as in presence of clouds or rain. Several examples are presented: in a blocking highs situation an atmospheric wave system at the Brunt-Vaisala frequency can be clearly distinguished; in a situation of clouds without rain the limit between clear air and clouds can be easily seen; and a windshear associated with a gust front in rainy conditions is shown. A comparison of 30 cm clear air radar Proust and 5 cm weather Doppler radar Ronsard will allow to select the best candidate for wind shear detection, taking into account the low sensibility to ground clutter of Ronsard radar.

Leroux, C.; Bertin, F.; Mounir, H.

1991-01-01

449

Phase Signature Radars.  

National Technical Information Service (NTIS)

The identification and classification of radar targets is facilitated by a newly developed technique based on measurements of the differential phase shift of the target scattering obtained at harmonic phase-locked frequencies. These phase differences are ...

W. B. Goggins P. Blacksmith C. J. Sletten

1974-01-01

450

Netted LPI RADARs.  

National Technical Information Service (NTIS)

A significant number of Low Probability of Intercept (LPI) radars are used in various military applications, from guided weapons (such anti-ship missile), to large platforms (aircrafts, ships), to large systems (Integrated Air Defense Systems - IADS). The...

C. Fougias C. Menychtas

2011-01-01

451

Passive MIMO Radar Detection.  

National Technical Information Service (NTIS)

Passive multiple-input multiple-output (MIMO) radar is a sensor network comprised of multiple distributed receivers that detects and localizes targets using the emissions from multiple non-cooperative radio frequency transmitters. This dissertation advanc...

D. E. Hack

2013-01-01

452

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...

453

Radar - The Future  

NASA Astrophysics Data System (ADS)

Progress in civil and military radar units since the invention of radar in 1935 is summarized, noting the trend to multipurpose units. The earliest systems functioned at 10 cm, then 3 cm after development of a cavity magnetron to provide power for shorter wavelengths. Military needs are driving improvements in three-dimensional scanning capabilities, Primarily to locate aircraft in the presence of ground clutter and sea surface scattering. Autonomous, separate transmitter and receiver units are being tested. Lengthening ground-based radar wavelengths to tens of meters will permit over-the-horizon sensing with backscattering, ionospheric bounce, or induction of a potential in the sea surface as the possible techniques. Mode S monopulse radars will permit transponder queries between small and large aircraft. Finally, pulse Doppler SAR systems may afford terrain recognition with no corroborating data except an expert systems data base.

Warwick, G.

1985-02-01

454

Imaging with Radar  

NSDL National Science Digital Library

This interactive activity from NOVA features synthetic aperture radar (SAR), which uses radio waves to create high-quality images. Examine SAR images of Washington, D.C., and learn about this technology's unique advantages.

Foundation, Wgbh E.

2004-01-29

455

Radar Target Approach Simulator.  

National Technical Information Service (NTIS)

A technique employed to generate nondispersive, continuously variable microwave time delay for the simulation of the approach of a radar to its target is described. A bulk elastic wave excited in a transparent crystal enables thousands of feet of propagat...

H. A. Cook

1971-01-01

456

Reflection measurements of microwave absorbers  

NASA Astrophysics Data System (ADS)

A swept-frequency interferometer is described for making rapid, real-time assessments of localized inhomogeneities in planar microwave absorber panels. An aperture-matched exponential horn is used to reduce residual reflections in the system to about -37 dB. This residual reflection is adequate for making comparative measurements on planar absorber panels whose reflectivities usually fall in the -15 to -25 dB range. Reflectivity measurements on a variety of planar absorber panels show that multilayer Jaumann absorbers have the greatest inhomogeneity, while honeycomb absorbers generally have excellent homogeneity within a sheet and from sheet to sheet. The test setup is also used to measure the center frequencies of resonant absorbers. With directional couplers and aperture-matched exponential horns, the technique can be easily applied in the standard 2 to 40 GHz waveguide bands.

Baker, Dirk E.; van der Neut, Cornelis A.

1988-12-01

457

Electrochemically regenerable carbon dioxide absorber  

NASA Technical Reports Server (NTRS)

Preliminary designs were generated for two electrochemically regenerable carbon dioxide absorber concepts. Initially, an electrochemically regenerable absorption bed concept was designed. This concept incorporated the required electrochemical regeneration components in the absorber design, permitting the absorbent to be regenerated within the absorption bed. This hardware was identified as the electrochemical absorber hardware. The second hardware concept separated the functional components of the regeneration and absorption process. This design approach minimized the extravehicular activity component volume by eliminating regeneration hardware components within the absorber. The electrochemical absorber hardware was extensively characterized for major operating parameters such as inlet carbon dioxide partial pressure, process air flow rate, operational pressure, inlet relative humidity, regeneration current density and absorption/regeneration cycle endurance testing.

Woods, R. R.; Marshall, R. D.; Schubert, F. H.; Heppner, D. B.

1979-01-01

458

Precise dispersion equations of absorbing filter glasses  

NASA Astrophysics Data System (ADS)

The refractive indices versus wavelength of optical transparent glasses are measured at a few wavelengths only. In order to calculate the refractive index at any wavelength, a so-called Sellmeier series is used as an approximation of the wavelength dependent refractive index. Such a Sellmeier representation assumes an absorbing free (= loss less) material. In optical transparent glasses this assumption is valid since the absorption of such transparent glasses is very low. However, optical filter glasses have often a rather high absorbance in certain regions of the spectrum. The exact description of the wavelength dependent function of the refractive index is essential for an optimized design for sophisticated optical applications. Digital cameras use an IR cut filter to ensure good color rendition and image quality. In order to reduce ghost images by reflections and to be nearly angle independent absorbing filter glass is used, e.g. blue glass BG60 from SCHOTT. Nowadays digital cameras improve their performance and so the IR cut filter needs to be improved and thus the accurate knowledge of the refractive index (dispersion) of the used glasses must be known. But absorbing filter glass is not loss less as needed for a Sellmeier representation. In addition it is very difficult to measure it in the absorption region of the filter glass. We have focused a lot of effort on measuring the refractive index at specific wavelength for absorbing filter glass - even in the absorption region. It will be described how to do such a measurement. In addition we estimate the use of a Sellmeier representation for filter glasses. It turns out that in most cases a Sellmeier representation can be used even for absorbing filter glasses. Finally Sellmeier coefficients for the approximation of the refractive index will be given for different filter glasses.

Reichel, S.; Biertümpfel, Ralf

2014-05-01

459

Active radar stealth device  

NASA Astrophysics Data System (ADS)

This patent discloses an active radar stealth device mounted on a host platform for minimizing the radar cross-section of the host platform. A coating which is essentially microwave transparent is attached to the surface of a host platform and is exposed to an incident microwave field. A plurality of detector/emitter pairs contained within the coating detect and actively cancel, respectively, the microwave field at each respective detector/emitter pair.

Cain, R. N.; Corda, Albert J.

1991-07-01

460

Radar Imaging of Mercury  

Microsoft Academic Search

Earth-based radar has been one of the few, and one of the most important, sources of new information about Mercury during\\u000a the three decades since the Mariner 10 encounters. The emphasis during the past 15 years has been on full-disk, dual-polarization\\u000a imaging of the planet, an effort that has been facilitated by the development of novel radar techniques and by

John K. Harmon

2007-01-01

461

Radar Imaging of Mercury  

Microsoft Academic Search

Earth-based radar has been one of the few, and one of the most important, sources of new information about Mercury during\\u000a the three decades since the Mariner 10 encounters. The emphasis during the past 15 years has been on full-disk, dual-polarization\\u000a imaging of the planet, an effort that has been facilitated by the development of novel radar techniques and by

J. Harmon

2004-01-01

462

Radar Imaging of Mercury  

Microsoft Academic Search

Earth-based radar has been one of the few, and one of the most important, sources of new information about Mercury during the three decades since the Mariner 10 encounters. The emphasis during the past 15 years has been on full-disk, dual-polarization imaging of the planet, an effort that has been facilitated by the development of novel radar techniques and by

John K. Harmon

2007-01-01

463

Downhole pulse radar  

SciTech Connect

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 samples for transmission uphole.

Chang, H.T.

1989-03-21

464

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

465

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

466

Doppler Radar Technology  

NSDL National Science Digital Library

This resource provides an introduction to the function and uses of the The National Weather Service's (NWS) Weather Surveillance Doppler Radar (WSR-88D). Topics include the components of the system, an overview of the products and overlays the system creates, and some example images with captions explaining what is being shown. There are also links to radar meteorology tutorials and to information on training to use the system and interpret its imagery.

467

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

468

A note on thermal analysis for an inclined plate crotch absorber  

SciTech Connect

Crotch absorbers are used to absorb unwanted synchrotron radiation to prevent most of the photons from striking the wall of a vacuum chamber. Since synchrotron radiation generated by bending the positron beam is very powerful, concentrated and penetrating, the absorber produces high internal heat generation. Depending on the materials used, this energy generation may be restricted near the surface of the absorber or distributed throughout the absorber with exponential decay in the direction of the penetration. The cooling of an absorber is important to prevent melting the material and to retain ultra high vacuum, since photon energy deposition on the metal surface causes the desorption of gases. This note describes an analytical solution of the heat transfer with application to designing a crotch absorber. The effects of angles and thicknesses of the plate and different materials on temperature distributions of the absorber are examined.

Choi, M.

1989-06-15

469

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

470

Plants absorb heavy metals  

SciTech Connect

Decontamination of heavy metals-polluted soils remains one of the most intractable problems of cleanup technology. Currently available techniques include extraction of the metals by physical and chemical means, such as acid leaching and electroosmosis, or immobilization by vitrification. There are presently no techniques for cleanup which are low cost and retain soil fertility after metals removal. But a solution to the problem could be on the horizon. A small but growing number of plants native to metalliferous soils are known to be capable of accumulating extremely high concentrations of metals in their aboveground portions. These hyperaccumulators, as they are called, contain up to 1,000 times larger metal concentrations in their aboveground parts than normal species. Their distribution is global, including many different families of flowering plants of varying growth forms, from herbaceous plants to trees. Hyperaccumulators absorb metals they do not need for their own nutrition. The metals are accumulated in the leaf and stem vacuoles, and to a lesser extent in the roots.

Parry, J.

1995-02-01

471

Passive radar augmented projectile (PRAP)  

US Patent & Trademark Office Database

The invention disclosed relates to gun-launched target projectiles wherein a radar-augmentor is included to increase the radar cross-section of the projectile to simulate on radar, an actual airborne threat such as aircraft and missiles. The radar augmentor comprises a base member, a uniform dielectric lens attached to said base member and a resilient support means between said base member and said lens. The dielectric lens is configured to provide a frontal radar return echo which simulates the actual airborne threat on radar.

1991-01-29

472

Innovative Anti Crash Absorber for a Crashworthy Landing Gear  

NASA Astrophysics Data System (ADS)

This paper defines an innovative concept to anti-crash absorber in composite material to be integrated on the landing gear as an energy-absorbing device in crash conditions to absorb the impact energy. A composite cylinder tube in carbon fiber material is installed coaxially to the shock absorber cylinder and, in an emergency landing gear condition, collapses in order to enhance the energy absorption performance of the landing system. This mechanism has been developed as an alternative solution to a high-pressure chamber installed on the Agusta A129 CBT helicopter, which can be considered dangerous when the helicopter operates in hard and/or crash landing. The characteristics of the anti-crash device are presented and the structural layout of a crashworthy landing gear adopting the developed additional energy absorbing stage is outlined. Experimental and numerical results relevant to the material characterization and the force peaks evaluation of the system development are reported. The anti-crash prototype was designed, analysed, optimized, made and finally the potential performances of a landing gear with the additional anti-crash absorber system are tested by drop test and then correlated with a similar test without the anti-crash system, showing that appreciable energy absorbing capabilities and efficiencies can be obtained in crash conditions.

Guida, Michele; Marulo, Francesco; Montesarchio, Bruno; Bruno, Massimiliano

2013-11-01

473

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

474

Polarimetric Borehole Radar System for Fracture Measurement  

Microsoft Academic Search

Radar polarimetry is a technology that overcomes the limitation between the radar resolution and the penetration depth of borehole radar. We have developed a stepped-frequency polarimetric borehole radar system. This is a polarimetric borehole radar system which measures the full-radar polarimetry in a borehole by changing the antenna arrangements. By using a network analyzer and an optical analog signal link,

Motoyuki Sato; Takashi Miwa

2000-01-01

475

High Resolution Capabilities of MIMO Radar  

Microsoft Academic Search

Multiple-input multiple-output (MIMO) radar is a multistatic architecture composed of multiple transmitters and receivers, which seeks to exploit the spatial diversity of radar backscatter. In conjunction with centralized processing, MIMO radar has the potential to significantly improve radar functions such as detection and parameter estimation. MIMO radar is distinct from other types of array radars such as phased array or

Nikolaus H. Lehmann; Alexander M. Haimovich; Rick S. Blum; Len Cimini

2006-01-01

476

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

477

Collector efficiency factor F' for absorbers with rectangular fluid ducts contacting the entire surface  

Microsoft Academic Search

The most commonly used absorbers in flat-plate collectors are manufactured as finned tubes. In this article, an alternative design is investigated: the absorber consists of a rectangular, narrow duct, in which the fluid contacts the entire surface. Under the conditions of fully developed laminar flow and negligible heat resistance of the absorber plate material, relations are developed to calculate the

Matthias Rommel; Wolfgang Moock

1997-01-01

478

A note on thermal analysis for an inclined plate crotch absorber  

Microsoft Academic Search

Crotch absorbers are used to absorb unwanted synchrotron radiation to prevent most of the photons from striking the wall of a vacuum chamber. Since synchrotron radiation generated by bending the positron beam is very powerful, concentrated and penetrating, the absorber produces high internal heat generation. Depending on the materials used, this energy generation may be restricted near the surface of

1989-01-01

479

Mars Radar Observations with the Goldstone Solar System Radar  

Microsoft Academic Search

The Goldstone Solar System Radar (GSSR) has successfully collected radar echo data from Mars over the past 30 years. As such, the GSSR has played a role as a specific mission element within Mars exploration. The older data provided local elevation information for Mars, along with radar scattering information with global resolution. Since the upgrade to the 70-m Deep Space

A. F. C. Haldemann; R. F. Jurgens; K. W. Larsen; R. E. Arvidson; M. A. Slade

2002-01-01

480

Microphysical cross validation of spaceborne radar and ground polarimetric radar  

Microsoft Academic Search

Ground-based polarimetric radar observations along the beam path of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR), matched in resolution volume and aligned to PR measurements, are used to estimate the parameters of a gamma raindrop size distribution (RSD) model along the radar beam in the presence of rain. The PR operates at 13.8 GHz, and its signal returns

V. Chandrasekar; Steven M. Bolen; Eugenio Gorgucci

2003-01-01

481

An electromechanical low frequency panel sound absorber.  

PubMed

The sound absorbing properties of a thin micro-perforated plate (MPP) coated with piezoelectric material with shunt damping technology is investigated. First a theoretical model is presented to predict the sound absorption coefficients of a thin plate attached with a piezoelectric patch and electrical circuits. Then the model is extended to analyze the sound absorption for a thin plate with micro perforations and piezoelectric material. Measurements are also carried out in an impedance tube and found to be in good agreements with the theoretical model. The sound absorption of the constructions can be much improved by tuning the electrical circuits. PMID:20707433

Chang, Daoqing; Liu, Bilong; Li, Xiaodong

2010-08-01

482

Phase Modulating the Urbana Radar.  

National Technical Information Service (NTIS)

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.

L. J. Herrington S. A. Bowhill

1983-01-01

483

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

484

Helicopter obstacle detection radar system  

Microsoft Academic Search

We have analyzed and experimentally tested the feasibility of thin wire detection using millimeter wave radar. The radar system includes a novel, fast scanning antenna and a transceiver\\/signal processor unit from BAE systems.

Lev S. Sadovnik; Vladimir A. Manasson; Robert M. Mino

2000-01-01

485

CFAR detection for multistatic radar  

Microsoft Academic Search

A multistatic radar system with n transmitters and one receiver is modelled. Several CFAR algorithms for detection are introduced. The proposed CFAR detectors are simulated and the performances are compared with the performance of a monostatic radar of higher power.

Vahideh Amanipour; Ali Olfat

2008-01-01

486

The UK radar scene today  

Microsoft Academic Search

Primary radar systems in the United Kingdom that recently entered service or are at an advanced stage of development are presented. Naval, airborne, and land-based types and civil and military radars, especially airborne equipment, are discussed.

J. Clarke

1985-01-01

487

The UK radar scene today  

NASA Astrophysics Data System (ADS)

Primary radar systems in the United Kingdom that recently entered service or are at an advanced stage of development are presented. Naval, airborne, and land-based types and civil and military radars, especially airborne equipment, are discussed.

Clarke, J.

488

Polarimetric radar modified  

NASA Astrophysics Data System (ADS)

Modification of 11-cm Doppler radar, to permit measurement of the complete polari-metric matrix of signals backscattered from meteorological media, was recently completed by the Gr