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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

Introduction to Radar Absorbent Materials (RAM).  

National Technical Information Service (NTIS)

The purpose of this Introduction is to present, in a straightforward way, the electromagnetic principles of Radar Absorbent Materials (RAM) for the benefit of the non-electromagnetic-specialist who finds himself involved in this field. The fundamental the...

P. G. Lederer

1986-01-01

6

Radarabsorberande Material: En Oeversikt (Radar Absorbing Materials: An Overview).  

National Technical Information Service (NTIS)

The report discusses the present state of knowledge of radar absorbing materials (RAM). In particular, the possibility to make thin absorbents that are efficient in a wide frequency band is discussed. The properties of two types of materials, polymers and...

P. O. Olsson

1995-01-01

7

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

8

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

9

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

10

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

11

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

12

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

13

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

14

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

15

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

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

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

18

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

19

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

20

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

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

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

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

Conducting-polymer-based radar-absorbing materials  

NASA Astrophysics Data System (ADS)

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

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

1997-11-01

25

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

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

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

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

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

30

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

31

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

32

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

33

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

34

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

35

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

36

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

37

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

38

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

39

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

40

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

41

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

42

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

43

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

44

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

45

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

46

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

47

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

48

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

49

Experimental Investigation of Impulse Radar for Mitigation of Effects of Radar Absorbing Materials.  

National Technical Information Service (NTIS)

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 adva...

H. Jianguo L. Zhongliang S. Yi

1995-01-01

50

Heat Resistant Radar Absorber.  

National Technical Information Service (NTIS)

A foamed ceramic slab is bonded to the three-layer polyimide RAM substrate to produce a radar absorbed capable of at least 10db absorptivity of the range 3 to at least 10 GHZ and of withstanding very high temperatures, for example, 3000 F for 80 seconds o...

W. P. Manning W. T. Passiuk

1978-01-01

51

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

52

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

53

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

54

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

55

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

56

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

NASA Astrophysics Data System (ADS)

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 of a sphere and cylinder with a single-layer coating. The proposed method can be used to assess the effectiveness of radar-absorbing materials.

Nesterov, S. M.; Skorodumov, I. A.

1992-12-01

57

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

58

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

59

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

60

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

61

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

62

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

63

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

64

Studies on Specular and Non-Specular Reflectivities of Radar Absorbing Materials (RAM) at Submillimetre Wavelengths.  

National Technical Information Service (NTIS)

The absorbing material studies presented in this Report are related to an ongoing project at the HUT Radio Laboratory for realising a submillimetre wave compact antenna test range (CATR) based on a hologram. Absorbing materials are needed in all indoor an...

J. Saeily A. V. Raeisaenen

2003-01-01

65

Fabrication of Organic Radar Absorbing Materials: A Report on the TIF Project.  

National Technical Information Service (NTIS)

The fabrication of microwave absorbing materials requires the ability to make materials with well-controlled properties such as shape, thickness, permittivity and permeability. The ability to measure the permittivity and permeability is an essential requi...

D. Makeiff P. Saville T. Huber

2005-01-01

66

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

67

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

68

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

69

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

70

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

71

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

72

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

73

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

74

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

75

Terahertz Backscattering Behavior of Various Absorbing Materials.  

National Technical Information Service (NTIS)

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 operatin...

A. J. Gatesman C. Wu L. DeRoeck R. H. Giles T. Horgan

2009-01-01

76

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

77

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

78

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

79

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

80

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

81

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

82

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

83

Decision-Making Aid for Multi-Layer Radar Absorbent Coverings.  

National Technical Information Service (NTIS)

A multi-criteria optimization method for manufacture of multi-layer radar-absorbent materials intended for cladding of aircraft is presented. This entails firstly the application of an optimization method by nonlinear constraints, the generalized projecte...

A. Bastiere

1990-01-01

84

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

85

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

86

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

87

Multi-objective optimization design of radar absorbing sandwich structure  

Microsoft Academic Search

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

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

2010-01-01

88

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

89

Solar radiation absorbing material  

DOEpatents

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 microporous carbon article by controlling the pore size. A thermally conductive substrate is provided with a solar selective surface by adhering an array of carbon particles in a suitable binder to the substrate, a majority of said particles having diameters within the range of about 0.2-10 microns.

Googin, John M. (Oak Ridge, TN); Schmitt, Charles R. (Oak Ridge, TN); Schreyer, James M. (Oak Ridge, TN); Whitehead, Harlan D. (Clinton, TN)

1977-01-01

90

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

91

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

92

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

93

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

94

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

95

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

96

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

97

Method for Assisting in Decision-Making for Multilayer Radar Absorbent Coverings.  

National Technical Information Service (NTIS)

A multicriteria optimization method for multi-layer radar absorbent coverings destined for use with existing aircraft is presented. This technique first uses an optimization procedure with nonlinear constraints, specifically the generalized projected grad...

A. Bastiere

1989-01-01

98

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

99

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

100

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

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

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

2005-01-01

101

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

102

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

103

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. We have begun evaluation of several new UV-screened polycarbonate sheet glazing constructions. This has involved interactions with several major polymer industry companies to obtain improved candidate samples. Proposed absorber materials were tested for UV resistance, and appear adequate for unglazed ICS absorbers.

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

2005-11-01

104

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

105

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

106

Material Model Evaluation of a Composite Honeycomb Energy Absorber.  

National Technical Information Service (NTIS)

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 th...

E. L. Fasanella K. E. Jackson M. A. Polanco M. S. Annett

2012-01-01

107

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

Microsoft Academic Search

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

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

2004-01-01

108

Controlling radar signature  

SciTech Connect

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

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

1992-08-01

109

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.

110

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

Microsoft Academic Search

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

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

2011-01-01

111

DEVELOPMENT OF SOYBEAN OIL-BASED ENERGY ABSORBING MATERIALS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The energy absorbing materials were prepared from epoxidized soybean oil with three different curing agents: Jeffamine EDR-148 (EDR-148), diethylenetriamine (DETA) and triethylenetetramine (TETA). Resulting polymers exhibited tensile stress-strain behavior similar to rubbery materials with good da...

112

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

113

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

114

Calorimetric particle detectors with superconducting absorber materials  

NASA Astrophysics Data System (ADS)

Massive superconducting absorbers of molybdenum and vanadium are used as low temperature calorimeter particle detectors. The high temperature resolution of the thermometry system, consisting of a superconducting phase transition thermometer monitored with a DC Squid, enables the detection of alpha particles with large single crystals. With a 35 g molybdenum single crystal, an energy resolution of 10 percent Full Width Half Maximum (FWHM) on 5.8 MeV alpha particles is obtained. The observed temperature rise of 1.2 mK is a factor of eight less than expected from the calculated heat capacity. Using a 15g vanadium single crystal, the energy resolution in 5.8 MeV alpha particles is 1.2 percent FWHM. In this case, the pulse height is a factor of five smaller than expected from the calculated heat capacity. A possible reason for the large deviations from the expected heat capacity is the presence of hydrogen dissolved in these transition metals, another reason might be the presence of surface impurities or defects.

Forster, G.; Ferger, P.; Feilitzsch, F. V.; Moessbauer, R. L.; Azgui, F.; Igalson, J.

1991-11-01

115

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

116

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

117

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

118

Determining factors for high performance silicone rubber microwave absorbing materials  

NASA Astrophysics Data System (ADS)

Silicone rubber microwave absorbing materials (RMAMs) based on ferrite as the major absorbent were prepared by the mechanical blending method. The determining factors for the complex permittivity, complex permeability, and reflectivity of RMAM were thoroughly investigated with various samples including different crystal structures of Ba-ferrite (M-type, W-type, and Y-type), the ferrite with doped elements (Ba, Sr), the materials' thickness, the combination ratio of ferrite and carbonyl iron. The effects of surface modification and loading amount of ferrite on the mechanical properties, processing performance, and absorbing property of RMAM were also assessed. The results show that W-type Ba-ferrite based RMAM exhibits better absorbing property at high frequencies (8-18 GHz) than the other two barium ferrites (M-type and Y-type) based ones, and the absorbing property of RMAM based on Sr-ferrite is best. As the thickness of RMAM and the amount of absorbents increase, the absorption peak moves toward low frequency, the absorption frequency bandwidth is narrowed, and the reflectivity first decreases and later increases. The optimum thickness is 1.5-1.7 mm, and the amount of ferrite is 450 parts per hundreds of rubber (phr). Surface modification of the absorbent with silane coupling agent could improve the mechanical properties and processing performance of RMAM. It is concluded that there will be a synergistic effect when carbonyl iron (CI) is used in combination with Sr-ferrite (Sr-W) in an appropriate proportion. When the total volume fraction of absorbents is 51%, the optimum ratio of Cl to Sr-W is 17:34, the absorption frequency bandwidth (<-10 dB) is about 8 GHz, and the absorption area is -99 dB.

Zou, Hua; Li, Shuhuan; Zhang, Liqun; Yan, Shani; Wu, Hanguang; Zhang, Shuai; Tian, Ming

2011-06-01

119

Highly absorbing metal nanolaminates for THz bi-material detectors  

Microsoft Academic Search

Interest in THz-ray sensing has significantly increased in recent years. It has been demonstrated that bi-material MEMS detectors show a great potential to be used for THz imaging. Our work aims to identify metal nanolaminates to improve the detector absorption in the range of interest. Using a finite element simulation tools we demonstrate that Chromium and Nickel films can absorb

Dragoslav Grbovic; Fabio Alves; Apostolos Karamitros; Gamani Karunasiri

2011-01-01

120

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

121

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

122

Microwave Absorber Properties of Magnetic and Dielectric Composite Materials  

NASA Astrophysics Data System (ADS)

In recent years, because of the rapid progress in wireless technology, microwave absorbers or noise suppressors have become necessary for a safe-electromagnetic-wave-level environment. To design microwave absorbers or noise suppressors, it is necessary to have knowledge of complex permittivity, ?r* and permeability, ?r*. In this report, we show the values of complex permeability, ?r* and permittivity, ?r* for a composite materials of magnetic (Iron, Fe, coated by Fe3O4) and dielectric (Titanium Oxide, TiO2), by changing Fe / TiO2 volume fraction ratio. As changing of these, we can change the values of complex permeability (?r* = ?r' - j?r") and complex permittivity (?r* = ?r' - j?r"). And the results are applied in the design of a microwave absorber which makes reflection losses and the central frequency to do a purpose, for example, necessary conditions of ETC (5.8GHz) use in Japan.

An, Young Joon; Nishida, Ken; Yamamoto, Takashi; Ueda, Shunkichi; Deguchi, Takeshi

123

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

2008-02-21

124

Impact Mechanics and High-Energy Absorbing Materials: Review  

Microsoft Academic Search

In this paper a review of impact mechanics and high-energy absorbing materials is presented. We review different theoretical models (rigid-body dynamics, elastic, shock, and plastic wave propagation, and nonclassical or nonlocal models. and computational methods (finite-element, finite-difference, and mesh-free methods. used in impact mechanics. Some recent developments in numerical simulation of impact (e.g., peridynamics) and new design concepts proposed as

Pizhong Qiao; Mijia Yang; Florin Bobaru

2008-01-01

125

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

126

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

127

POLYMER ENGINEERING: Research on composite materials at Liverpool University, Part 2: Energy absorbing composite materials  

Microsoft Academic Search

The ability of a composite material to absorb energy in its bulk rather than at the tip of a crack is very important when such materials are used in the automobile industry, for example to protect passengers from the consequences of high speed impact under crash conditions. Part 2 of this article describes research into the design and fabrication of

D. Hull

1983-01-01

128

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

129

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

130

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

Microsoft Academic Search

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

P. J. J. McCullagh; I. D. Graham

1985-01-01

131

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.

132

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

133

Effect of various absorbing materials on the thermal performance of solar stills  

Microsoft Academic Search

There is a strong need to improve the single slope solar still thermal performance and increase the production rate of distilled water. Different types of absorbing materials were used to examine their effect on the yield of solar stills. These absorbing materials are of two types: coated and uncoated porous media (called metallic wiry sponges) and black volcanic rocks. Four

Salah Abdallah; Mazen M. Abu-Khader; Omar Badran

2009-01-01

134

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

135

Locally resonant phononic woodpile: A wide band anomalous underwater acoustic absorbing material  

NASA Astrophysics Data System (ADS)

To meet the demand of modern acoustic absorbing material for which acoustic absorbing frequency region can be readily tailored, we introduced woodpile structure into locally resonant phononic crystal (LRPC) and fabricated an underwater acoustic absorbing material, which is called locally resonant phononic woodpile (LRPW). Experimental results show that LRPW has a strong capability of absorbing sound in a wide frequency range. Further theoretical research revealed that LRPC units and woodpile structure in LRPW play an important role in realization of wide band underwater strong acoustic absorption.

Jiang, Heng; Wang, Yuren; Zhang, Milin; Hu, Yanping; Lan, Ding; Zhang, Yinmin; Wei, Bingchen

2009-09-01

136

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

137

Study of absorber materials usable on microstrip and their attribute improvements  

Microsoft Academic Search

A novel method for improving properties of ab- sorber materials usable on a microstrip transmission line is proposed. Improvement is obtained by using a metallic sheets and changing a distribution of electric field along the absorber. Suitability of these absorbers as sliding load ele- ments is discussed as well. Experimental verification of pro- posed modification has been done and comparison

Milan Prihoda; Ondrej Moravek; Karel Hoffmann

2011-01-01

138

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

139

Effect of weight fraction of carbon black and number of plies of E-glass fiber to reflection loss of E-glass/ripoxy composite for radar absorbing structure (RAS)  

NASA Astrophysics Data System (ADS)

Nowadays, studies on investigating radar absorbing structure (RAS) using fiber reinforced polymeric (FRP) composite materials are becoming popular research field because the electromagnetic properties of FRP composites can be tailored effectively by just adding some electromagnetic powders, such as carbon black, ferrite, carbonyl iron, and etc., to the matrix of composites. The RAS works not only as a load bearing structure to hold the antenna system, but also has the important function of absorbing the in-band electromagnetic wave coming from the electromagnetic energy of tracking systems. In this study, E-glass fiber reinforced ripoxy resin composite was fabricated by blending the conductive carbon black (Ketjenblack EC300J) with the binder matrix of the composite material and maximizing the coefficient of absorption more than 90% (more than -10 dB) within the X-band frequency (8 - 12 GHz). It was measured by electrical conductivity (LCR meter) and vector network analyzer (VNA). Finally, the composite RAS with 0.02 weight fraction of carbon black and 4 plies of E-glass fiber showed thickness of 2.1 mm, electrical conductivity of 8.33 × 10-6 S/m, and maximum reflection loss of -27.123 dB, which can absorb more than 90% of incident EM wave throughout the entire X-band frequency range, has been developed.

Widyastuti; Ramadhan, Rizal; Ardhyananta, Hosta; Zainuri, Mochamad

2013-09-01

140

Evaluation of blue and green absorbing proteorhodopsins as holographic materials.  

PubMed

Transient holographic diffraction is observed for the green (GPR) and blue (BPR) absorbing proteorhodopsins (BAC31A8 and HOT75M1, respectively), as well as the GPR E108Q and BPR E110Q variants. In contrast to bacteriorhodopsin, where the metastable bR-M pair is responsible for generating diffraction, the pR and red-shifted N-like states fulfill that role in both the green and blue wild-type proteorhodopsins. The GPR E108Q and BPR E110Q variants, however, behave more similarly to their bacteriorhodopsin analogue, D96N, with diffraction arising from the PR M-state (strongly enhanced in both GPR E108Q and BPR E110Q). Of the four proteins evaluated, wild type (WT) GPR and GPR E108Q produce the highest diffraction efficiencies, etamax, at approximately 1% for a 1.7 OD sample. GPR E108Q, however, requires 1-2 orders of magnitude less laser intensity to generate eta equivalent to WT GPR and BR D96N under similar conditions (as compared to literature values). WT BPR requires lower actinic powers than GPR but diffracts only about 30% as well. BPR E110Q performs the most poorly of the four, with etamax < 0.05% for a 1.4 OD film. The Kramers-Kronig transformation and Koglenik's coupled wave theory were used to predict the dispersion spectra and diffraction efficiency for the long M-state variants. To a first approximation, the gratings formed by all samples decay upon discontinuing the 520 nm actinic beams with a time constant characteristic of the appropriate intermediate: the N-like state for WT GPR and BPR and the M-state for GPR 108Q and BPR E110Q. PMID:18237161

Xi, Bangwei; Tetley, William C; Marcy, Duane L; Zhong, Cheng; Whited, Gregg; Birge, Robert R; Stuart, Jeffrey A

2008-02-01

141

Dysprosium titanate as an absorber material for control rods  

Microsoft Academic Search

Disprosium titanate is an attractive control rod material for the thermal neutron reactors. Its main advantages are: insignificant swelling, no out-gassing under neutron irradiation, rather high neutron efficiency, a high melting point (?1870°C), non-interaction with the cladding at temperatures above 1000°C, simple fabrication and easily reprocessed non-radioactive waste. It can be used in control rods as pellets and powder. The

V. D. Risovany; E. E. Varlashova; D. N. Suslov

2000-01-01

142

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

National Technical Information Service (NTIS)

The electromagnetic backscattering of a crosscut of a cruise missile coated by a thin homogeneous layer made of radar absorbent material is modeled using a finite element method. Based on the radar cross section and a reflection coefficient, optimization ...

H. T. Banks K. Ito J. Toivanen

2005-01-01

143

Gamma ray attenuation coefficient measurement for neutron-absorbent materials  

NASA Astrophysics Data System (ADS)

The compounds Na2B4O7, H3BO3, CdCl2 and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408 keV, have been determined by the ? rays transmission method in a good geometry setup; also, these coefficients were calculated by MCNP code. A comparison between experiments, simulations and Xcom code has shown that the study has potential application for determining the attenuation coefficient of various compound materials. Experiment and computation show that H3BO3 with the lowest average Z has the highest gamma ray attenuation coefficient among the aforementioned compounds.

Jalali, Majid; Mohammadi, Ali

2008-05-01

144

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

2012-08-01

145

Reflectance characteristics of selected materials for reference targets for 10.6-micron laser radars  

NASA Astrophysics Data System (ADS)

The reflective characteristics of several materials have been examined in an effort to develop a 10.6-micron reflectivity standard for field measurements with laser radars. Measurements on twelve different target materials showed that many materials have components of diffuse reflectivity, specular reflectivity, and retroreflectivity. For each material examined, both the effective Lambertian reflectivity and the beam depolarization were determined. It was also found that because of the strong retroreflection component present with many materials, the practice of estimating the effective diffuse reflectivity from measurements of total reflectivity could lead to erroneous reflectivity values for laser radar systems. One of the preferred reference targets found for 10.6-micron field measurements was canvas tarpaulin.

Henshall, H.; Cruickshank, J.

1988-07-01

146

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

NASA Astrophysics Data System (ADS)

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 ˜1.3eV (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 ˜260 generalized IpIIIqVIr chalcopyrite materials. It identifies over 20 high-SLME materials, including the best known as well as previously unrecognized PV absorbers.

Yu, Liping; Zunger, Alex

2012-02-01

147

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

148

Perfectly matched layer-absorbing boundary condition for left-handed materials  

Microsoft Academic Search

The perfectly matched layer (PML) absorbing boundary condition (ABC) is extended to truncate the boundary of left-handed materials in the Finite-Difference Time-Domain (FDTD) simulation. The uniaxial material parameters are given in the frequency domain, and discretized in the FDTD update procedure by means of the Z-Transform technique. The effectiveness of the PML is demonstrated by numerical results.

X. T. Dong; X. S. Rao; Y. B. Gan; B. Guo; W. Y. Yin

2004-01-01

149

Design of lightweight, broad-band microwave absorbers using genetic algorithms  

Microsoft Academic Search

A procedure for synthesizing multilayered radar absorbing coatings is presented. Given a predefined set of Nm available materials with frequency-dependent permittivities ?i(f) and permeabilities ?i(f ) (i=1,. . ., Nm), the technique determines simultaneously the optimal material choice for each layer and its thickness. This optimal choice results in a screen which maximally absorbs TM and TE incident plane waves

Eric Michielssen; Jean-Michel Sajer; S. Ranjithan; Raj Mittra

1993-01-01

150

Collapse hazard assessment in evaporitic materials from ground penetrating radar: a case study  

Microsoft Academic Search

Evaporitic materials have been studied by means of ground penetrating radar (GPR) in order to evaluate the collapse hazard.\\u000a The obtained 200 MHz GPR profiles show a low signal-noise ratio over the first 3 m depth, where well-defined and continuous\\u000a reflectors can be observed. Between 3 and 4.5 m depth, the signal to noise ratio decreases due to attenuation of the electromagnetic\\u000a (EM)

Tomás Martín-Crespo; David Gómez-Ortiz

2007-01-01

151

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

Microsoft Academic Search

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

Kai Sun; Nan Wu; Ye Tian; Xingwei Wang

2011-01-01

152

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

153

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

154

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

155

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

156

Reflection and transmission for layered composite materials  

NASA Astrophysics Data System (ADS)

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.

1991-03-01

157

Improvements on Calcium Rich Materials Analysis by External PIXE using Selective Absorbers  

Microsoft Academic Search

For Particle Induced X-ray Emission Spectroscopy (PIXE) and X-ray Fluorescence Technique (XRF), the analysis of materials rich in one or two elements may present some difficulties due to high counting rates and saturation effects in X-ray detectors. In this case, it is possible to use selective absorbers in order to reduce the intensity of the major elements with low attenuation

G. Güereca; J. L. Ruvalcaba-Sil

2004-01-01

158

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

Microsoft Academic Search

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

Suraj S. Deshmukh; Gareth H. McKinley

2007-01-01

159

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

160

Search of novel photovoltaic absorbers from first-principles spectroscopic screening of hundreds of materials  

NASA Astrophysics Data System (ADS)

Screening for candidate PV absorbers from numerous existing materials would require a good selection criterion. Initial selection criteria generally rest on the intrinsic material properties and abundance, postponing defect and contact issues to after the list of candidates has been narrowed down. The currently available Shockley-Queisser efficiency formula gives a universal efficiency vs band gap curve (no matter whether the gap is direct or indirect) and ignore all radiative recombination loss, and has proven over the years to be insufficient. Here we propose a calculable selection criterion of ``spectroscopic limited maximum efficiency (SLME)'' which considers the type of band gap (direct allowed, direct forbidden and indirect), the shape of absorption spectra and material-dependent radiative recombination loss by a simple model. First-principles quasiparticle calculations of SLME for ˜300 generalized I-III-VI and ˜500 I-V-VI materials identify over 40 candidates with higher SLME than currently used best thin-film absorbers. Analysis of the electronic structure of the top candidates reveals an interesting mechanism for high absorptivity and shows that some indirect gap materials can even be better than direct gap materials.

Yu, Liping; Zunger, Alex

2012-02-01

161

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

NASA Astrophysics Data System (ADS)

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

Okamoto, Koichi; Umezaki, Takeo; Hattori, Akira

162

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

2012-12-13

163

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

164

Surfaces with adaptive radar reflection coefficients  

NASA Astrophysics Data System (ADS)

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

Chambers, Barry

1997-10-01

165

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

166

Surface-active and Light-absorbing Secondary Organic Aerosol (SOA) Material  

NASA Astrophysics Data System (ADS)

We have observed the formation of light-absorbing, high-molecular-weight, and surface-active organics from methylgyloxal interacting with ammonium salts in aqueous aerosol mimics. Mixtures of methylglyoxal and glyoxal also form light-absorbing products and exhibit surface tension depression with a Langmuir-like dependence on initial methylglyoxal concentration. We used chemical ionization mass spectrometry with a volatilization flow tube inlet (Aerosol-CIMS) to characterize the product species. The results are consistent with aldol condensation products, carbon-nitrogen species, sulfur-containing compounds, and oligomeric species up to 759 amu. These observations have potentially significant implications for our understanding of the effects of SOA on climate, since a) SOA are typically treated as non-absorbing in climate models, and b) surface tension depression in aqueous aerosols by SOA material may result in increased cloud condensation nucleus (CCN) activity. Furthermore, surface film formation could affect aerosol heterogeneous chemistry. We will also discuss aerosol flow tube O3 oxidation experiments designed to determine the atmospheric lifetimes of the observed product compounds.

McNeill, V. F.; Sareen, N.; Schwier, A. N.; Shapiro, E. L.

2009-12-01

167

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

SciTech Connect

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

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

2010-09-15

168

Shock-Absorbing Materials. Rept. 1. Backpacking Materials for Deeply Buried Protective Structures.  

National Technical Information Service (NTIS)

The objective of this study was to review the existing theory and concepts pertaining to the use of backpacking materials around deeply buried protective structures and to provide a limited evaluation of a number of commercially available products in orde...

G. C. Hoff

1967-01-01

169

Scientists Identify New Quaternary Materials for Solar Cell Absorbers (Fact Sheet), NREL Highlights, Science  

SciTech Connect

Research provides insight for exploring use of earth-abundant quaternary semiconductors for large-scale solar cell applications. For large-scale solar electricity generation, it is critical to find new material that is Earth abundant and easily manufactured. Previous experimental studies suggest that Cu{sub 2}ZnSnS{sub 4} could be a strong candidate absorber materials for large-scale thin-film solar cells due to its optimal bandgap, high adsorption coefficient, and ease of synthesis. However, due to the complicated nature of the quaternary compound, it is unclear whether other quaternary compounds have physical properties suitable for solar cell application. Researchers at the National Renewable Energy Laboratory (NREL), Fudan University, and University College London have performed systematic searches of quaternary semiconductors using a sequential cation mutation method in which the material properties of the quaternary compounds can be derived and understood through the evolution from the binary, to ternary, and to quaternary compounds. The searches revealed that in addition to Cu{sub 2}ZnSnS{sub 4}, Cu{sub 2}ZnGeSe{sub 4} and Cu{sub 2}ZnSnSe{sub 4} are also suitable quaternary materials for solar cell absorbers. Through the extensive study of defect and alloy properties of these materials, the researchers propose that to maximize solar cell performance, growth of Cu{sub 2}ZnSnS{sub 4} under Cu-poor/Zn-rich conditions will be optimal and the formation of Cu{sub 2}ZnSn(S,Se){sub 4} alloy will be beneficial in improving solar cell performance.

Not Available

2011-10-01

170

Tantalum nitride films for the absorber material of refractive-type EUVL mask  

NASA Astrophysics Data System (ADS)

Tantalum nitride (TaxN) films were evaluated for use as the absorber material of masks for extreme ultraviolet lithography (EUVL). TaxN films deposited by DC sputtering using an Ar+N2 gas mixture had a low stress of less than 300 MPa, an amorphous-like structure, and a low deep ultraviolet (DUV) reflectivity. This film provides a DUV contrast of 30% with respect to the Mo/Si multilayer whose top is on Si layer. A TaxN film deposited using a Xe+N2 gas mixture was found to be better in the following ways: the stress was below 100 MPa, the change in stress was below 30 MPa, and the density was more than 1 g/cm3 higher. Furthermore, treating the surface of TaxN film with O2 plasma or sputtering a TaxO film on it using an Ar+O2 gas mixture improved the DUV contrast because the resulting surface has a lower DUV reflectivity than TaxN film. These results indicate that TaxN film is one of the most suitable materials for the absorber of EUVL masks.

Takahashi, Masashi; Ogawa, Taro; Hoshino, Eiichi; Hoko, Hiromasa; Lee, Byoung T.; Chiba, Akira; Yamanashi, Hiromasa; Okazaki, Shinji

2001-08-01

171

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

172

Shock-Absorbing Materials. Report 2. Cellular Concrete as a Backpacking Material.  

National Technical Information Service (NTIS)

The use of low-density cellular concrete, having an oven-try unit weight of 50 pcf or less, as a backpacking material for deeply buried protective structures was studied. Cellular concrete was found to be suitable for this type of application. A number of...

G. C. Hoff

1971-01-01

173

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

174

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

175

Light absorbing material (soot) in rainwater and in aerosol particles in the Maldives  

NASA Astrophysics Data System (ADS)

Simultaneous measurements of soot (absorbing material at 528 nm) and inorganic ions in aerosol and precipitation at the Maldives Climate Observatory Hanimaadhoo during the period May 2005 to February 2007 have made it possible to calculate the washout ratio (WR) of these components as a measure of how efficiently they are scavenged by precipitation. On the basis of air trajectories the data have been separated into days with polluted air arriving from the Indian subcontinent in a northeasterly sector during winter and clean monsoon days with southerly flow from the Indian Ocean. The average soot concentration was a factor of 10 higher in the former situations. Despite considerable scatter for individual days, a systematic pattern emerged when the WR for the different components were compared with each other. During the monsoon season the WR for soot was similar to that of sulfate and other fine mode aerosol components, indicating that soot containing particles in these situations were efficient as cloud condensation nuclei. The origin of the light absorbing material during the monsoon season is unclear. During the polluted winter days, on the other hand, the WR for soot was three times smaller than that of sulfate. This indicates that, even after a travel time of several days, the soot containing particles from India have retained much of their hydrophobic property. The low WR and the infrequent rain during this season probably contribute to extending the atmospheric lifetime of soot well beyond several days. Surprisingly high concentrations of non-sea-salt calcium were measured during the monsoon season, substantially higher than during the winter season. The origin of these high values could be long-range transport from the Australian or African continents. Another possibility might be exopolymer gels derived from the ocean surface microlayer.

Granat, L.; EngströM, J. E.; Praveen, S.; Rodhe, H.

2010-08-01

176

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

EPA Science Inventory

We propose to test and develop a suite of methodologies for direct detection of pooled and residual DNAPLs from surface ground-penetrating radar (GPR) data. This is a new, quantitative approach to the analysis of GPR data in which we determine material properties remotely by qua...

177

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

Microsoft Academic Search

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

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

2004-01-01

178

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

179

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

180

Standard Reference Materials: Certification and Use of Acidic Potassium Dichromate Solutions as an Ultraviolet Absorbance Standard-SRM 935.  

National Technical Information Service (NTIS)

The apparent specific absorbances of 0.001N perchloric acid solutions of a high purity potassium dichromate salt, Standard Reference Material (SRM) 935, have been certified at four wavelengths in the ultraviolet-235, 257, 313 and 350 nm. This publication ...

R. W. Burke R. Mavrodineanu

1977-01-01

181

Secondary organic material formed by methylglyoxal in aqueous aerosol mimics - Part 1: Surface tension depression and light-absorbing products  

NASA Astrophysics Data System (ADS)

We show that methylglyoxal forms light-absorbing secondary organic material in aqueous ammonium sulfate and ammonium nitrate solutions mimicking tropospheric aerosol particles. The light-absorbing products form on the order of minutes, and solution composition continues to change over several days. The results suggest an aldol condensation pathway involving the participation of the ammonium ion. Aqueous solutions of methylglyoxal, with and without inorganic salts, exhibit surface tension depression. Methylglyoxal uptake could potentially change the optical properties, climate effects, and heterogeneous chemistry of the seed aerosol over its lifetime.

Schwier, A. N.; Shapiro, E. L.; Sareen, N.; McNeill, V. F.

2009-07-01

182

Near-IR absorbing phthalocyanine derivatives as materials for organic solar cells  

NASA Astrophysics Data System (ADS)

Phthalocyanines (Pcs) are highly conjugated synthetic porphyrin analogs that exhibit high extinction coefficients and hole mobilities, and strong pi-pi interactions. We have developed a general method for the synthesis of peripherally functionalized Pc chromophores using 'click' chemistry, wherein an alkynyl substituted Pc is reacted with an azide, providing an elegant route to the creation of a library of numerous Pcs. We have also developed a simple route to the synthesis of tri- and tetravalent metal Pc derivatives such as titanyl phthalocyanine (TiO Pc) involving solvent-free conditions. Solvent-free conditions are environmentally friendly and industrially economical, and in the present context effectively eliminate the formation of non-metallated phthalocyanine (H 2Pc), a side product often seen in other routes that interferes with their purification. We have also prepared and characterized thin-films of some of these Pcs, TiOPcs in particular, wherein we have developed an easy route to various TiO Pc polymorphs exhibiting different near-IR sensitivities via spin-coating whose optical properties are reminiscent of Phase-I and Phase-II polymorphs of the unmodified TiOPc. Phase-II is particularly interesting as it is photoelectrically active in the near-IR region with a Q-band maximum at ca. 890 nm. We have also fabricated and characterized organic solar cells in both planar heterojunction (PHJ) and bulk heterojunction (BHJ) architectures based on one of these materials, which exhibited good near-IR photoactivity with the absorption spectrum extending up to 1 micrometer in the near-IR. The incident and absorbed photon to current efficiency (IPCE and APCE) spectra showed contributions from the TiOPc in the near-IR region with local maxima around 680 nm and 920 nm, corresponding to the Frenkel and the charge-transfer (CT) bands of the TiOPc, respectively.

Mayukh, Mayank

183

Novel planar absorber designs using genetic algorithms  

Microsoft Academic Search

Electromagnetic absorbers are often used to reduce radar echo from anechoic chambers, aircraft and so on. For many applications, the absorber must be built conformable to a complex surface, or must have a flat interface with the air. A new class of planar electromagnetic absorbers is proposed. This absorber is created by drilling textures within or on top of lossy

Suomin Cui; D. S. Weile; J. L. Volakis

2005-01-01

184

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

185

[Reaction of the fibrose eyeball covering upon the suture material synthetic and absorbable "Dexon". (Experimental study) (author's transl)].  

PubMed

The present paper deals with the results of 20 eyes of experimentally operated laboratory animals, whose perforating wounds (of cornea and those of sclerocorneal region) have been suturated with a new type of absorbable synthetic suture material "Dexon" thickness being 6-0. The synthetic absorbable suture material "Dexon" is made of polyglycol acid, and it has been introduced to market by the firm Davis and Geck (U.S.A.). The inflammatory tissue reaction to the presence of the suture material "Dexon" is prominent and can by compared to the reaction to chromic resorbable suture materials (catgut or collagen). The suture material "Dexon" start to resorb in the course of the 2nd-3rd weeks after operation. The suture material "Dexon" can be used at an advantage in the operation where it is possible to cover the knots by a conjuctival lobe (in sclerocorneal region or in strabismus surgery) in this way the tendency to overgrowing of epithelial cells along the suture channels can be prevented. The "Dexon" material is sufficiently flexible and firm and has no antigenic properties, therefore it appears very prospective for ophthalmosurgery. PMID:231422

Olah, Z

1979-11-01

186

Heat transport by material-dependent heating during absorption of radiation in the water absorbed dose calorimeter  

Microsoft Academic Search

Water absorbed dose calorimeters have been developed for the application as PTB standards for the dosimetry in radiation therapy with photon and electron radiation. Different detector types for various applications are available. In this paper, heat conduction effects of “sealed” detectors are investigated, caused by the material-dependent temperature rise during the absorption of 60Co-?-radiation in the detector walls and in

A. Krauss; M. Roos

1999-01-01

187

A Study of Cancellous Bone as a Shock-Absorbing Composite Material.  

National Technical Information Service (NTIS)

The goal of the project was to explore and define the structure-properties relationship in cancellous (spongy) bone and its role as shock absorber in the body. The primary tool for structural investigation was quantitative stereology. By using this techni...

R. M. Rose

1976-01-01

188

Analysis of Polarized Light Reflected from Absorbing Materials at Normal Incidence  

Microsoft Academic Search

Expressions are derived for the intensity of the analysed light reflected from absorbing crystals (a) under crossed polarizing units and (b) with the analyser slightly rotated from the crossed position Four intensity maxima per complete rotation of the specimen are obtained when the polarizers are crossed, but under certain circumstances, as the analyser is rotated from the crossed position, the

J Woodrow; B W Mott; H R Haines

1952-01-01

189

Millimeter radar  

Microsoft Academic Search

The paper discusses some of the advantages offered by millimeter waves over microwaves, reviews possible and past millimeter radar applications, and looks at some future millimeter radar systems. The coming millimeter radars include radiometric seekers, radiometers, and high resolution radar for satellite identification. Important problems to be resolved before millimeter radars can be put into production include component capability; radar

S. L. Johnston

1977-01-01

190

Mode-locked Nd: GdVO4 laser with graphene oxide/polyvinyl alcohol composite material absorber as well as an output coupler  

NASA Astrophysics Data System (ADS)

Graphene oxide/polyvinyl alcohol (GO/PVA) composite material saturable absorbers were fabricated. Sandwich structured GO/PVA absorber was used as an absorber as well as an output coupler in mode-locked Nd: GdVO4 laser. The laser pulses with the duration of 12 ps, repetition rate of 120 MHz and the maximum average output power of 680 mW were produced.

Wang, YongGang; Chen, Houren; Hsieh, Wenfeng; Tsang, YuenHong

2013-02-01

191

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

SciTech Connect

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

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

2011-03-01

192

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

193

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

194

Light-absorbing secondary organic material formed by glyoxal in aqueous aerosol mimics  

NASA Astrophysics Data System (ADS)

Light-absorbing and high-molecular-weight secondary organic products were observed to result from the reaction of glyoxal in mildly acidic (pH=4) aqueous inorganic salt solutions mimicking aqueous tropospheric aerosol particles. High-molecular-weight (500-600 amu) products were observed when ammonium sulfate ((NH4)2SO4) or sodium chloride (NaCl) was present in the aqueous phase. The products formed in the (NH4)2SO4 solutions absorb light at UV and visible wavelengths. Substantial absorption at 300-400 nm develops within two hours, and absorption between 400-600 nm develops within days. Pendant drop tensiometry measurements show that the products are not surface-active. The experimental results along with ab initio predictions of the UV/Vis absorption of potential products suggest that an aldol condensation mechanism is active in the glyoxal-(NH4)2SO4system, resulting in the formation of pi-conjugated products. If similar products are formed in atmospheric aerosol particles, they could change the optical properties of the seed aerosol over its lifetime.

Shapiro, E. L.; Szprengiel, J.; Sareen, N.; Jen, C. N.; Giordano, M. R.; McNeill, V. F.

2009-01-01

195

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

National Technical Information Service (NTIS)

Waste tank fissile material and non-fissile material estimates are used to evaluate criticality safety for the existing sludge inventory and batches of sludge sent to Extended Sludge Processing (ESP). This report documents the weight ratios of several non...

J. S. Clemmons

1994-01-01

196

Absorbents as packing materials in on-line coupling of reversed phase liquid chromatography and gas chromatography via a programmed temperature vaporizer.  

PubMed

A method based on the use of absorbents as packing materials in the interface of the direct coupling between reversed phase liquid chromatography and gas chromatography (RPLC-GC) is proposed. To that end, a comparative study on different adsorbents and absorbents was carried out. Specifically, Tenax TA and Gaschrom were used as adsorbents while polydimethylsiloxane and poly(50% phenyl:50% methylsiloxane) were the absorbents tested. Some experimental variables involved in the solvent elimination were separately optimised for adsorbent and absorbent materials. Relative standard deviations (RSD) lower than 10% were achieved in all cases but the use of absorbents showed interesting advantages with respect to adsorbents, namely a simpler performance of the experimental work, which facilitates the sample preparation step and the subsequent gas chromatographic analysis to be performed. PMID:17306811

Flores, Gema; Ruiz Del Castillo, Maria Luisa; Herraiz, Marta

2007-02-04

197

Millimeter wave complex dielectric permittivity and complex magnetic permeability measurements of absorbing materials  

Microsoft Academic Search

This dissertation presents new methods for characterization of materials in the millimeter wave range. Historically, this has been the most difficult part of the electromagnetic spectrum for accurate measurements of material properties. New instrumentation has now been developed for operation in this frequency band. The new techniques developed in the course of this work allowed precise measurement of dielectric properties

Igor Ivanovich Tkachov

2000-01-01

198

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

199

Sound absorbing property of porous metal materials with high temperature and high sound pressure by turbulence analogy  

NASA Astrophysics Data System (ADS)

A quantitative theoretical model is presented to investigate the sound absorbing property of porous metal materials with high temperature and high sound pressure based on Kolmogorov turbulence theory in this paper. The porous materials have a large number of anomalous pores with similar scale, and these irregular pores could be considered as quasi-periodic structure that is very similar to the small-scale turbulence. Therefore, Kolmogorov turbulence theory is adopted to analyze the wave propagation inside the porous metal materials, in which the characteristic velocity and characteristic scale can be obtained by the nondimensional analysis method. Furthermore, the acoustical pressure amplitude in the porous metal materials under high temperature and high sound pressure level can be figured out with respect to metal wire diameter, porosity, and other parameters. It is shown quantitatively that the acoustic pressure amplitude goes up with an increase in the temperature and/or the sound pressure level. This model is verified by the well agreement between the theoretical and experimental results. It could provide a reliable theoretical guidance for the applications of porous metal materials in the area of vibration and noise control under high temperature and high sound pressure level.

Hui Wu, Jiu; Hu, Zhi Ping; Zhou, Han

2013-05-01

200

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

201

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

202

Shock-absorbing behavior of five restorative materials used on implants.  

PubMed

The damping effect of five restorative materials used to veneer test crowns rigidly connected to a Brånemark implant and subjected to an impact force was measured. These materials included a gold alloy; a noble metal ceramic alloy; porcelain; a laboratory-processed, light-activated microfilled resin; and a heat- and pressure-polymerized poly(methyl methacrylate) resin. The two resins were found to reduce the impact force by about 50% when compared to porcelain or the alloys. The clinical significance of the results is discussed. PMID:1810320

Gracis, S E; Nicholls, J I; Chalupnik, J D; Yuodelis, R A

203

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

Microsoft Academic Search

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

Sergei Yu Guskov; A Kasperczuk; T Pisarczyk; S Borodziuk; M Kalal; J Limpouch; J Ullschmied; E Krousky; K Masek; M Pfeifer; K Rohlena; J Skala; P Pisarczyk

2006-01-01

204

Corrosion resistant neutron absorbing coatings  

Microsoft Academic Search

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

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

2012-01-01

205

Two-Photon Absorbing Materials and Two-Photon-Induced Chemistry  

Microsoft Academic Search

Two-photon absorption, the process by which an excited molecule or material is produced by the simultaneous\\u000a absorption of two photons, has been studied extensively in recent years, from both fundamental and application\\u000a points of view. On one side, the field has been expanded with the measurement of two-photon absorption\\u000a spectra and cross sections for a wide range of conjugated molecules. In

Mariacristina Rumi; Stephen Barlow; Jing Wang; Joseph W. Perry; Seth R. Marder

206

Rice straw–wood particle composite for sound absorbing wooden construction materials  

Microsoft Academic Search

In this study, rice straw–wood particle composite boards were manufactured as insulation boards using the method used in the wood-based panel industry. The raw material, rice straw, was chosen because of its availability. The manufacturing parameters were: a specific gravity of 0.4, 0.6, and 0.8, and a rice straw content (10\\/90, 20\\/80, and 30\\/70 weight of rice straw\\/wood particle) of

Han-Seung Yang; Dae-Jun Kim; Hyun-Joong Kim

2003-01-01

207

Passive Radar.  

National Technical Information Service (NTIS)

The basic ideas and concepts of one of the newest branches of radar, that of passive radar, are discussed. A great deal of attention is devoted to questions of the use of passive radar by the armed forces. The physical fundamentals of passive radar, and t...

A. G. Nikolaev S. V. Pertsov

1975-01-01

208

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

SciTech Connect

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

Not Available

2011-10-01

209

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

SciTech Connect

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

Aguiar, Vitor A. P.; Medina, Nilberto H. [Instituto de Fisica, Universidade de Sao Paulo, SP (Brazil); Moreira, Ramon H.; Silveira, Marcilei A. G. [Departamento de Fisica, Centro Universitario da FEI, Sao Bernardo do Campo, SP (Brazil)

2010-05-21

210

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

211

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

212

[Tendon sutures with a new monofilament synthetic absorbable suture material (PDS-suture of 6-0 strength). Results of animal experiments].  

PubMed

The absorbable synthetic suture (PDS suture 6-0 with spatula needle) was examined by experiments on the tendon of the M. flexor digitorum pedis communis of the hare. A total of 34 tendon sutures was prepared histologically and evaluated. The new suture material is distinguished by greatly extended absorption time, low foreign body reaction and an improved tensile strength. With this suture, the conditions in which absorbable suture material can be used are increased. This is particularly true of so-called bradytrophic tissue. PMID:6802585

Albers, W; Geldmacher, J; Giedl, H; Beyer, W

1982-03-01

213

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

214

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

215

Passive Radar.  

National Technical Information Service (NTIS)

This book sets forth in brief the physical principles of passive radar, describes the functional diagrams and circuit peculiarities of the apparatus, and offers recommendations for modifying radar receivers to adapt them for receiving natural radio-freque...

A. G. Nikolaev S. V. Pertsov

1975-01-01

216

Experimental Study on Reactivity Worth for Absorber Material in High Conversion Light Water Reactor Using FCA-HCLWR Core Fueled with Enriched Uranium  

Microsoft Academic Search

Experimental study on reactivity worth for absorber material in HCLWR core has been carried out in a series of experiments using the Fast Critical Assembly (FCA) in Japan Atomic Energy Research Institute (JAERI). The central reactivity worth as well as the simulated control rod worth of B4C with different B content and of Hf was measured in FCA-HCLWR core fueled

Shigeaki OKAJIMA; Toshitaka OSUGI; Takeshi SAKURAI; Yoshihisa TAHARA

1990-01-01

217

Heat absorbing window  

Microsoft Academic Search

A heat absorbing window is disclosed which can receive solar energy and transmit the illumination part of the solar energy, while utilizing the heat part of such energy to provide a source of heat for useful purposes. The window includes a frame with three window panes. The outermost pane faces the exterior and is of non-heat absorbing material. The middle

Berman

1978-01-01

218

Polypyrrole Based Microwave Absorbers  

Microsoft Academic Search

Reflection of microwave radiations from single layer and two-layer materials is calculated. Microwave absorbing materials are formulated by mixing a commercially available paint or rubber with the conducting polypyrrole (PPy) powder. The reflection loss strongly depends on thickness and complex permittivity of the material. For a single layer material, optimum values of the real part, ?', and imaginary part, ?'',

V.-T. Truong; S. Z. Riddell; R. F. Muscat

1998-01-01

219

Accelerated life testing of solar energy materials: Case study of some selective solar absorber coating materials for DHW systems. A report of task 10 solar materials research and development  

NASA Astrophysics Data System (ADS)

Accelerated life testing offers the possibility to forecast material service life prior to installation. For the development of new components and systems it, thus, opens a possibility for systematic life cost analysis and material selection. The present report documents the results of a joint study aimed at establishing the use and limitations of methods for accelerated life testing applicable to materials used in solar heating and cooling applications. The study was conducted as part of the work in Task 10 'Solar Materials Research and Development' of the International Energy Agency Solar Heating and Cooling Program. The work was organized as a case study in which four commercially-available selective absorber materials were selected for study. These materials are used in single-glazed flat plate solar collectors for domestic hot water production.

Carlsson, Bo; Koehl, Michael; Frei, Ulrich; Moeller, Kenneth

1994-02-01

220

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

221

Low temperature selective absorber research  

Microsoft Academic Search

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

S. A. Herzenberg; R. Silberglitt

1982-01-01

222

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

223

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

224

Doppler Radar  

Microsoft Academic Search

This paper contains a discussion of the principle of operation of cw doppler search radar systems and an analysis of their performance capabilities, with particular emphasis on the elimination of fixed targets. A comparison of these systems and MTI pulse radar systems is made.

E. J. Barlow

1949-01-01

225

TRMM Radar.  

National Technical Information Service (NTIS)

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...

K. Okamoto

1993-01-01

226

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

227

Spatial-spectral processing for imaging systems: Multibeam RF imaging and radar systems using spectral hole burning materials  

NASA Astrophysics Data System (ADS)

Systems which form many spatial beams (beamformers) for the RF and microwave spectral bands output either a few simultaneous spatial beams across a wide bandwidth---using true-time-delay beamformers---or many simultaneous spatial beams across a moderate bandwidth---using digital aperture synthesis imagers. The simultaneous spatial beams in true-time-delay beamformers require parallel hardware while digital aperture synthesis imagers requires both high speed digitizers and huge digital processors. Moreover; each output beam is typically processed further by a spectrum analyzer or a radar processor. Simultaneous formation and processing of all spatial beams is intractable for wide bandwidths and many beams. This dissertation develops and demonstrates a new class of photonic processing architectures which form and process many simultaneous, wide bandwidth spatial beams. These photonic architectures modulate RF signals from an emulated array of antennas onto an array of coherent optical carriers. I show the theory, the methods, and the results for systems which use Fourier optics and spectral hole burning (SHB) crystals; the demonstrated applications are: wideband RF imaging, Doppler radar, and multi-static radar applications. Proof-of-concept results show 20-beam RF images across a 1 GHz bandwidth and 20-beam radar correlations across bandwidths up to 150 MHz, but these systems can be scaled to process antenna arrays with thousands of beams across bandwidths up to 20 GHz. While these systems can process wide bandwidths for large antenna arrays, I also show an analysis that claims these systems can offer sensitivity levels comparable to other digital or analog beamformers.

Braker, Benjamin M.

228

Sound Absorbers  

NASA Astrophysics Data System (ADS)

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

Fuchs, H. V.; Möser, M.

229

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

Microsoft Academic Search

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

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

230

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

231

Principals of Radar and Meteorological Radar Devices.  

National Technical Information Service (NTIS)

Three meteorological radar units are described: the Malachite radiotheodolite with rangefinder attachment, the Meteorite radar station, and the MRL radar station. The principles of operation of these systems are given along with circuit descriptions and e...

O. G. Korol R. D. Chernyak

1973-01-01

232

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

233

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

234

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging.  

National Technical Information Service (NTIS)

Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observatory radar system transm...

B. A. Campbell D. B. Campbell L. M. Carter

2010-01-01

235

Pulsed-laser time-resolved thermal mirror technique in low-absorbance homogeneous linear elastic materials.  

PubMed

A theoretical model for a time-resolved photothermal mirror technique using pulsed-laser excitation was developed for low absorption samples. Analytical solutions to the temperature and thermoelastic deformation equations are found for three characteristic pulse profiles and are compared to finite element analysis methods results for finite samples. An analytical expression for the intensity of the center of a continuous probe laser at the detector plane is derived using the Fresnel diffraction theory, which allows modeling of experimental results. Experiments are performed in optical glasses, and the models are fitted to the data. The parameters of the fit are in good agreement with previous literature data for absorption, thermal diffusion, and thermal expansion of the materials tested. The combined modeling and experimental techniques are shown to be useful for quantitative determination of the physical properties of low absorption homogeneous linear elastic material samples. PMID:24067567

Lukasievicz, Gustavo V B; Astrath, Nelson G C; Malacarne, Luis C; Herculano, Leandro S; Zanuto, Vitor S; Baesso, Mauro L; Bialkowski, Stephen E

2013-10-01

236

Use of co-combustion bottom ash to design an acoustic absorbing material for highway noise barriers.  

PubMed

The present study aims to determine and evaluate the applicability of a new product consisting of coal bottom ash mixed with Portland cement in the application of highway noise barriers. In order to effectively recycle the bottom ash, the influence of the grain particle size of bottom ash, the thickness of the panel and the combination of different layers with various particle sizes have been studied, as well as some environmental properties including leachability (EN-12457-4, NEN-7345) and radioactivity tests. Based on the obtained results, the acoustic properties of the final composite material were similar or even better than those found in porous concrete used for the same application. According to this study, the material produced presented no environmental risk. PMID:23916843

Arenas, Celia; Leiva, Carlos; Vilches, Luis F; Cifuentes, Héctor

2013-08-02

237

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

238

Shipboard Radar.  

National Technical Information Service (NTIS)

The navigational radar 'Stvor' is designed for installation on ships of the shipping fleet and also on marine and river boats of low and medium tonnage. A 'Stvor' station enables ships to navigate in zero visibility -- in fog, at night, etc. Because of it...

1968-01-01

239

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

240

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

2012-11-29

241

Effects of material properties on laser-induced bubble formation in absorbing liquids and on submerged targets  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation of blood clots in a fluid-filled blood vessel is accomplished by an explosive evaporation process. The resulting vapor bubble rapidly expands and collapses to disrupt the thrombus (blood clot). The hydrodynamic pressures following the bubble expansion and collapse can also be used as a driving force to deliver clot-dissolving agents into thrombus for enhancement of laser thrombolysis. Thus, the laser-induced bubble formation plays an important role in the thrombus removal process. In this study the effects of material properties on laser-induced cavitation bubbles formed in liquids and on submerged targets have been visualized with a microsecond strobe or high speed framing camera.

Shangguan, Hanqun; Casperson, Lee W.; Shearin, Alan; Paisley, Dennis L.; Prahl, Scott A.

1997-05-01

242

Solar energy absorber  

SciTech Connect

A solar energy absorber module is described comprising a molded substantially rigid top sheet of translucent plastic material and a molded substantially rigid bottom sheet of solar energy absorbing substantially opaque plastic material bonded together by circular bond indentations formed in each of the top sheet and the bottom sheet. The circular bond indentation on each sheet is spaced from each other a distance equal to the diameter of the circular bond thereby forming convex lens-like elliptical sites located between adjacent circular bond indentations for augmentation of solar energy, the circular bond indentations being formed in successive offset rows to define longitudinal tortuous sinusoidal channels in communication with a header at each end of the module for passage of working fluid therethrough.

Smith, W.F.

1988-08-16

243

Theoretical Fundamentals of Radar.  

National Technical Information Service (NTIS)

The book examines the principles of radar, methods of coordinate measurement and scanning and circuits for radar stations of three types: with an operator, a continuous computer installation and a digital computer. It presents the characteristics of radar...

A. A. Korostelev A. V. Petrov N. I. Burenin V. E. Dulevich Y. A. Melnik

1967-01-01

244

Radar observations in low earth orbit  

NASA Astrophysics Data System (ADS)

This paper presents an overview on radar techniques for the observation of space debris in low Earth orbits which were developed at FGAN in the frame of DARA and ESA/ESOC study contracts for the employment of the Tracking and Imaging Radar (TIRA) system in the past five years. For space debris observations TIRA is mainly operated in two different modes: In a tracking mode and in a beam-park mode of operation. Methods and algorithms were developed to analyse raw radar data, to compute radar images, and to estimate physical characteristics of space objects like size, shape, attitude, orbit, orbital lifetime, ballistic coefficient, mass, and material composition.

Mehrholz, Dieter

1997-05-01

245

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

246

Microwave holography revealed by photothermal films and lock-in IR thermography: application to electromagnetic materials NDE  

Microsoft Academic Search

The amplitude and phase spacing distributions of electromagnetic fields are imaged and measured using microwaves interferometry revealed by photothermal films and lock-in infrared thermography. Such EM fields imaging is a powerful tool for NDE of dielectric and radar absorbing materials.

Daniel L. Balageas; Patrick Levesque; Mylene Nacitas; Jean-Claude Krapez; Gerard D. Gardette; Michel Lemistre

1996-01-01

247

Microwave holography revealed by photothermal films and lock-in IR thermography: application to electromagnetic materials NDE  

NASA Astrophysics Data System (ADS)

The amplitude and phase spacing distributions of electromagnetic fields are imaged and measured using microwaves interferometry revealed by photothermal films and lock-in infrared thermography. Such EM fields imaging is a powerful tool for NDE of dielectric and radar absorbing materials.

Balageas, Daniel L.; Levesque, Patrick; Nacitas, Mylene; Krapez, Jean-Claude; Gardette, Gerard D.; Lemistre, Michel

1996-11-01

248

Genetic algorithm design of Pareto optimal broadband microwave absorbers  

Microsoft Academic Search

The concept of Pareto optimality is applied to the study of choice tradeoffs between reflectivity and thickness in the design of multilayer microwave absorbers. Absorbers composed of a given number of layers of absorbing materials selected from a predefined database of available materials are considered. Three types of Pareto genetic algorithms for absorber synthesis are introduced and compared to each

D. S. Weile; E. Michielssen; D. E. Goldberg

1996-01-01

249

Absorber coatings' degradation  

SciTech Connect

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

Moore, S.W.

1984-01-01

250

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

251

Evaluation of the 1999-2003 Head Impact Upgrade of FMVSS No. 201 Upper-Interior Components: Effectiveness of Energy-Absorbing Materials Without Head-Protection Air Bags.  

National Technical Information Service (NTIS)

Energy-absorbing materials that meet the head-impact upgrade of FMVSS No. 201 reduce AIS 4-to-6 head injuries due to contact with upper-interior components by an estimated 24 percent. When all vehicles on the road meet FMVSS No. 201, it will save an estim...

C. J. Kahane

2011-01-01

252

A ?/4 Wave Absorber for Both 60 and 76 GHz Bands  

NASA Astrophysics Data System (ADS)

While the demand of millimeter-wave intelligent transport system(ITS) including the automotive radar increases, utilization of electromagnetic(EM) waves on the street is increasing now. However, malfunction may be caused to communication and detection by the diffused EM wave reflected from incidental facilities such as a road sign and others. If the road sign having an absorbing function of the unwanted EM waves is realized, it is very effective to prevent the diffused EM wave reflected from the road sign. In this study, we focus on a transparent ?/4 wave absorber with resistive films attached on the road sign in adding absorbing function of EM waves of automotive rader frequency. In this structure, spacer is fabrecated of light reflecting sheet consisting of a part of the road sign and polycarbonate(PC) plate made of the transparent dielectric material. In this case, we try to examine the absorption characteristics of the proposed absorber both 60 and 76GHz bands theoretically and experimentally. The results show that the high-performance ?/4 wave absorbers for 60 and 76 GHz bands are realized.

Kondo, Asuka; Toyota, Makoto; Soh, Tetsu; Hashimoto, Osamu

253

Radar Ionospheric Impact Mitigation  

Microsoft Academic Search

New ionospheric modeling technology is being developed to improve correction of ionospheric impacts on the performance of ground-based space-surveillance radars (SSRs) in near-real-time. These radars, which detect and track space objects, can experience significant target location errors due to ionospheric delay and refraction of the radar signals. Since these radars must detect and track targets essentially to the radar horizon,

G. Bishop; D. Decker; C. Baker

2006-01-01

254

Radar surveillance in urban environments  

Microsoft Academic Search

Radar surveillance in difficult environments like urban areas can be challenging due to large amounts of both multipath and clutter. Additionally, buildings and clutter like parked vehicles can produce shadowed areas where the line-of-sight is broken. We analyzed urban materials to determine how to utilize multipath to see into the shadows of urban environments, which polarization has the least loss,

Dave Tahmoush; Jerry Silvious; Bob Bender

2012-01-01

255

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

256

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

257

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

258

Features of ultrawideband radar projecting  

Microsoft Academic Search

The article presents a new approach to ultrawideband (UWB) radar projecting. Some advantages of such radars are shown in comparison with common narrowband radars and some features of UWB radars are considered, which do not allow the use of traditional methods. New methods of UWB radar characteristics calculation and radar systems projecting are suggested. It discusses the range equation, passive

Igor Immoreev; B. Vovshin

1995-01-01

259

Goldstone Solar System Radar.  

National Technical Information Service (NTIS)

Planning, direction, experimental design, and coordination of data-acquisition and engineering activities in support of all Goldstone planetary radar astronomy were performed. This work demands familiarity with the various components of a planetary radar ...

R. F. Jurgens

1988-01-01

260

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

261

Spaceborne Radar Study.  

National Technical Information Service (NTIS)

Three air-defense radar surveillance systems are described, each consisting of active radar satellites capable of operating at earth-synchronous orbit altitude with associated ground control stations. Systems 1 (three satellites) provides a detection fenc...

J. Greene R. Kaplan G. J. McNiff P. Nosal J. L. Schultz

1974-01-01

262

Statistical MIMO Radar.  

National Technical Information Service (NTIS)

Inspired by recent advances in multiple-input multiple-output (MIMO) communications, we introduce the statistical MIMO radar concept. Unlike beamforming, array radar, or STAP, which presuppose a high correlation between signals either transmitted or recei...

A. Haimovich E. Fishler R. Blum D. Chizhik R. Valenzuela

2004-01-01

263

CHIRP Doppler radar  

Microsoft Academic Search

The present investigation is concerned with the concept of a combination of the clinical procedure of reconstruction tomography with the radar processing for linear FM pulse compression. An approach based on such a combination is to be employed to map radar backscatter energy. Radar systems employing pulse compression of linear frequency modulated (CHIRP) pulses are considered along with the inversion

M. Bernfeld

1984-01-01

264

Aviation weather radar  

Microsoft Academic Search

The Federal Aviation Administration has established three ground-based weather radar programs. The terminal Doppler weather radar (TDWR) and weather system processor (WSP) provide wind shear detection capability for air traffic controllers in the terminal area. These systems also reduce weather related delays. The next generation weather radar (NEXRAD) is used by the FAA to improve safety and reduce weather related

D. H. Turnbull

1995-01-01

265

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

266

Microwave absorbing composite lattice grids  

Microsoft Academic Search

Stretching dominated lattice grids reinforced by glass fibers and carbon fibers filled with spongy materials were designed and manufactured to achieve multifunctional structures with microwave absorbing abilities. The reflectivity of the GFRC and CFRC grid panels was measured in the darkroom at normal and oblique incidences, respectively. GFRC grid panels of 20mm thickness and CFRC panels of 18mm thickness displayed

H. L. Fan; W. Yang; Z. M. Chao

2007-01-01

267

The RADOT Code for the Tracking of Radar Incident on Trees.  

National Technical Information Service (NTIS)

A computer code, RADOT, has been developed to track incident radar through forests consisting of realisitically simulated trees. RADOT fires parallel radar rays at the simulated forest and records information for all materials intersected between the orig...

M. O. Cohen H. A. Steinberg

1978-01-01

268

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

269

Cloud and Precipitation Radar  

NASA Astrophysics Data System (ADS)

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

Hagen, Martin; Höller, Hartmut; Schmidt, Kersten

270

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

2012-05-25

271

Drill string shock absorber  

Microsoft Academic Search

A telescopic shock absorber for use in a drill string includes a resilient arrangement to cushion telescopic contraction and extension of the shock absorber in response to shock loads and vibrations imparted during drilling. The shock absorber operates independently of the drilling fluid pressure conducted through the structure during drilling operations. A dampening system assists in cushioning the shock loads

E. A. Anderson; D. D. Webb

1985-01-01

272

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

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

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

273

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

274

Radar and method therefor  

US Patent & Trademark Office Database

A radar (300) comprises a transceiver (302) for transmitting pulses directed to a subsurface area of interest (102) and for receiving a reflected wave (210) from the subsurface area of interest. The pulses have a pulse duration and amplitude constrained by the equation, d.sup.2.vertline.E.vertline.e/m.ltoreq.1 Angstrom, where d is the pulse duration in seconds, E is the pulse amplitude in volts/meter, e equals the charge of an electron in Coulombs, and m equals the mass of an electron in Kg. A processing device (304), in communication with the transceiver, processes the reflected wave and displays an image of the subsurface area of interest and identifies the material composition of subsurface objects that have known properties that vary as a function of the pulse duration and amplitude.

2002-04-23

275

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

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

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

276

30. Perimeter acquisition radar building room #318, showing radar control. ...  

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

30. Perimeter acquisition radar building room #318, showing radar control. Console and line printers - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

277

Millimeter Wave Polarimetric Monopulse Radar Debugging System  

Microsoft Academic Search

For testing millimeter wave polarimetric monopulse radar and testing algorithms for polarimetric radar, millimeter wave polarimetric monopulse radar debugging system is proposed in this paper. Polarimetric radar, as a kind of radar with strong counter-countermeasure capability, is more and more popular used nowadays. The cost of polarimetric radar is more expensive than traditional single-polarimetric radar. Millimeter wave polarimetric monopulse radar

Jin Tao; Qi Xiaohui; Zhang Min; Qiao Xiaolin; Yuan Shuqing; Zhang Qunxing

2007-01-01

278

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

Microsoft Academic Search

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

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

2009-01-01

279

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

280

Radar in transition  

NASA Astrophysics Data System (ADS)

It is pointed out that radar engineers, at the end of 1984, find their field in transition between the conventional designs of the post War II era and the digitally controlled, solid-state systems which will be in place for the year 2000. The U.S. Navy has two major phased array radar systems in operation, including the rotating three-dimensional (3D) AN/SPS-48, and the phased-scanned AN/SPY-1 (Aegis) radars. The Aegis represents a major step beyond the conventional 3D and mechanical fire-control radars. However, it requires a special ship, dedicated to its use. Attention is given to questions regarding an extension of the application of Aegis technology to other U.S. Navy applications and to other navies, an ambitious solid-state radar program in the UK, and Army radars.

Barton, D. K.

1984-12-01

281

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

282

Spaceborne Atmospheric Radar Technology  

Microsoft Academic Search

NASA is developing advanced instrument concepts and technologies for future spaceborne atmospheric radars, with the over-arching objectives of making such instruments more capable in supporting future science needs, and more cost effective. Two such examples are the Second-Generation Precipitation Radar (PR-2) and the Nexrad-In-Space (NIS). PR- 2 is a 14\\/35-GHz dual-frequency rain radar with a deployable 5- meter, wide-swath scanned

Eastwood Im; Stephen L. Durden

283

Methods for absorbing neutrons  

SciTech Connect

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

284

DORIS radar calibration method  

NASA Astrophysics Data System (ADS)

Following the interest expressed by ESA and FGAN, it was decided to realise some evaluation of the DORIS calibration method with the TIRA radar. This paper, organised in four parts, describes: - the importance of radar calibration in the space debris domain - the principle of the DORIS calibration method - the results obtained with the TIRA FGAN radar using the DORIS reference - the advantages of the DORIS calibration and the future uses of this method in an European exercise involving for the ESA benefit both French and German radars.

Ameline, P.

2001-10-01

285

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging  

Microsoft Academic Search

Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observa- tory radar system transmits a single sense of circular polari- zation, and both senses of circular polarization are received, which allows for the construction

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

2011-01-01

286

The orientation and construction of high efficiency passive radar targets  

Microsoft Academic Search

A study of the conventional meteorological radar target, aluminized paper over an inverted tetrahedral wood frame, shows that it has very poor performance at low angles of elevation in precisely the region where it is likely to move out of radar range in clear weather. An octahedral target, constructed from the same materials, but having a different orientation, has a

P. J. Eccles

1965-01-01

287

Radar Location Equipment Development Program: Phase I  

SciTech Connect

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

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

1985-06-01

288

EISCAT Svalbard radar  

Microsoft Academic Search

The main fields of interest of the Finnish scientists in EISCAT research are listed. Finnish interests in the Polar Cap Radar (PMR) and areas where the Finnish contribution could be important are addressed: radar techniques; sporadic E layers in the polar cap; atmospheric models; auroral studies in the polar cap; nonthermal plasmas in the F region; coordinated measurements with the

Markku Lehtinen; Jorma Kangas

1992-01-01

289

EISCAT Svalbard Radar.  

National Technical Information Service (NTIS)

The main fields of interest of the Finnish scientists in EISCAT research are listed. Finnish interests in the Polar Cap Radar (PMR) and areas where the Finnish contribution could be important are addressed: radar techniques; sporadic E layers in the polar...

M. Lehtinen J. Kangas

1992-01-01

290

Doppler weather radar  

Microsoft Academic Search

The Doppler weather radar and its signals are examined from elementary considerations to show the origin and development of useful weather echo properties such as signal-to-noise ratio (SNR), range correlation, signal statistics, etc. We present a form of the weather radar equation which explicitly shows the echo power loss due to finite receiver bandwidth and how it is related to

RICHARD J. DOVIAK; DUSAN S. ZRNIC; DALE S. SIRMANS

1979-01-01

291

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

292

UWB radars in medicine  

Microsoft Academic Search

Applied research on biomedical applications of UWB radar is targeted to the identification of the possible new devices made possible by the technology, to the design and development of those devices, and to the clinical testing of the systems obtained. Applications can be divided into two main sectors according to the frequency range used. For the conventional UWB radar microwave

Enrico M. Staderini

2002-01-01

293

Stereo Radar Analysis.  

National Technical Information Service (NTIS)

The topographic accuracy of the AN/APQ-102(XA-2) side-looking radar and its specific applicability to 1:50,000 and 1:250,000 scale topographic mapping were tested using stereo radar techniques with real data. The two basic stereo configurations, opposite-...

G. Gracie R. K. Brewer J. W. Bricker R. A. Johnson

1970-01-01

294

Panchromatic and polypanchromatic radar  

Microsoft Academic Search

Application of broad-band (panchromatic) illumination in radar systems should permit improvement in image quality and reduction of tracking and detection problems due to fading. The effect of frequency averaging on radar return from a simple target array is demonstrated by numerical computation and on image quality by ultrasonic simulation. The required bandwidth for a slightly rough random surface is determined

RICHARD K. MOORE; WILLIAM P. WAITE

1969-01-01

295

Radar clutter classification  

Microsoft Academic Search

The problem of classifying radar clutter as found on air traffic control radar systems is studied, and an algorithm is developed to carry out this classification automatically. The basis for the algorithm is Bayes decision theory and the parametric maximum a posteriori probability (MAP) classifier. This classifier employs a quadratic discriminant function and is optimum for feature vectors that are

Wolfgang Stehwien

1990-01-01

296

Radar clutter classification  

Microsoft Academic Search

The problem of classifying radar clutter as found on air traffic control radar systems is studied. An algorithm based on Bayes decision theory and the parametric maximum a posteriori probability classifier is developed to perform this classification automatically. This classifier employs a quadratic discriminant function and is optimum for feature vectors that are distributed according to the multivariate normal density.

Wolfgang Stehwien

1989-01-01

297

Transient coupled conductive\\/radiative heat transfer in absorbing, emitting and scattering media: application to laser-flash measurements on ceramic materials  

Microsoft Academic Search

A model is presented for the calculation of transient combined radiative\\/conductive heat transfer in heterogeneous semitransparent materials at elevated temperatures. It is based on optical material properties (scattering, absorption) that can be determined experimentally at room temperature. This model is applied to the simulation of laser-flash measurements on ceramic powder compacts. We demonstrate that the relevance of the radiative contributions

J. Fricke

1997-01-01

298

Flexible metamaterial absorbers for stealth applications at terahertz frequencies.  

PubMed

We have wrapped metallic cylinders with strongly absorbing metamaterials. These resonant structures, which are patterned on flexible substrates, smoothly coat the cylinder and give it an electromagnetic response designed to minimize its radar cross section. We compare the normal-incidence, small-beam reflection coefficient with the measurement of the far-field bistatic radar cross section of the sample, using a quasi-planar THz wave with a beam diameter significantly larger than the sample dimensions. In this geometry we demonstrate a near-400-fold reduction of the radar cross section at the design frequency of 0.87 THz. In addition we discuss the effect of finite sample dimensions and the spatial dependence of the reflection spectrum of the metamaterial. PMID:22274387

Iwaszczuk, Krzysztof; Strikwerda, Andrew C; Fan, Kebin; Zhang, Xin; Averitt, Richard D; Jepsen, Peter Uhd

2012-01-01

299

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

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

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

300

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

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

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

301

On radar polarimetry in FM-CW radar  

Microsoft Academic Search

This paper attempts to apply the principle of radar polarimetry to wideband synthetic aperture FM-CW radar and presents a basic polarimetric detection result of a linear target in a laboratory measurement. Although the principle of radar polarimetry has well been established for the completely polarized wave and for the monostatic case, it still needs to be extended to wideband radar

Y. Yamaguchi; T. Nishikawa; W.-M. Boerner; M. Sengoku; Hyo Joon Eom

1993-01-01

302

Infrared temperature measurements on solar trough absorber tubes  

Microsoft Academic Search

The temperature distribution on solar trough absorber tubes determines thermal losses and hotspots can lead to material stress and limit absorber tube lifetime. The concentrated solar radiation, however, makes it difficult to determine the temperature on solar absorbers. Temperature sensors that require contact to the measurement object are not appropriate and even pyrometry fails, when external light sources interfere. Only

Markus Pfänder; Eckhard Lüpfert; Paul Pistor

2007-01-01

303

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

304

Air traffic control radar tester  

Microsoft Academic Search

Our aim is to develop a radar tester equipment for commercial and military services. The task is to create one (or more) target or clutter on the radar screen with given distance, velocity and fluctuation. This equipment is placed within few hundred meters from the radar, so it is able to analyze the whole radar system from the antenna, via

Péter KOVÁCS; Levente DUDÁS; Rudolf SELLER; József ORBÁN

2008-01-01

305

Air traffic control radar tester  

Microsoft Academic Search

Our aim had been to develop a radar tester equipment for commercial and military services. The task is to create one (or more) target or clutter on the radar screen with given distance, velocity and fluctuation. This equipment is placed within few hundred meters from the radar, so it is able to analyze the whole radar system from the antenna,

Levente DUDÁS; Rudolf SELLER; Péter RENNER; József ORBÁN

2009-01-01

306

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

307

Reflection co-efficient of multilayer microwave absorbers in X-band  

Microsoft Academic Search

Design of multilayer microwave absorbers has become essential for effective absorption of microwave energy in the given range of frequencies due to the limitation of amount of energy that could be absorbed by a single layer absorber. There are various methods to design multilayer microwave absorbing materials. In this, multiple layers of dielectric materials are usually placed on top of

M. Murugan; V. K. Kokate

2008-01-01

308

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

309

Porous absorber for solar air heaters  

SciTech Connect

A general discussion of the factors affecting solar collector performance is presented. Bench scale tests done to try to determine the heat transfer characteristics of various screen materials are explained. The design, performance, and evaluation of a crude collector with a simple screen stack absorber is treated. The more sophisticated absorber concept, and its first experimental approximation is examined. A short summary of future plans for the collector concept is included. (MHR)

Finch, J.A.

1980-09-10

310

Incoherent scatter radar contributions  

NASA Astrophysics Data System (ADS)

The contributions of the incoherent scatter radar technique to knowledge of the neutral upper atmosphere of the earth in general and the development of the CIRA 1986 model in particular are discussed. Incoherent radar scattering involves the transmission of a radio wave into the atmosphere and the reception of the energy scattered by the free electrons illuminated by the wave. Attention is given to the chronology of radar contributions to the development of upper atmosphere models, the ion energy balance and continuity equations, exospheric temperatures, and studies of the lower thermosphere.

Oliver, W. L.; Alcayde, D.; Bauer, P.

311

Active radar jamming  

NASA Astrophysics Data System (ADS)

Active radar jammers are described. In confusion jammers the perturbing action is produced by thermal noise which is intensified, or by a carrier wave modulated by a noise signal, or by a carrier wave which is frequency modulated with a lot of sine waves of different frequencies. There are jammers to be used once, which are fired to the spot or hang from a parachute. Deception jammers (misleading jammers) emit false radar echoes, one or several produced by a repetition system, requiring a certain form of memory. It is shown how to emit varying false distance or velocities, and how to disturb angles in a radar used to guide artillery fire.

Jernemalm, Veine

1988-09-01

312

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

Microsoft Academic Search

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

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

2006-01-01

313

Quantitative Analysis of Venus Radar Backscatter Data in Arcgis.  

National Technical Information Service (NTIS)

Ongoing mapping of the Ganiki Planitia (V14) quadrangle of Venus and definition of material units has involved an integrated but qualitative analysis of Magellan radar backscatter images and topography using standard geomorphological mapping techniques. H...

S. M. Long E. B. Grosfils

2005-01-01

314

Cassini radar : system concept and simulation results  

NASA Astrophysics Data System (ADS)

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

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

1998-10-01

315

Radar detection of wetland ecosystems: a review  

Microsoft Academic Search

Periodically, reviews of our knowledge of radar–wetland relationships and detection parameters have been provided by various authors. Since the publication of these works, additional research has been completed. Five major remote sensing journals spanning the years 1965–2007 formed the basis of this review. The vast majority of significant material found its way into these mainstream journals in one aspect or

Floyd M. Henderson; Anthony J. Lewis

2008-01-01

316

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

Microsoft Academic Search

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

Avelina Fernández; Pierre Picouet; Elsa Lloret

2010-01-01

317

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

Microsoft Academic Search

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

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

2007-01-01

318

Use of borosilicate-glass raschig rings as a neutron absorber in solutions of fissile material-ANSI\\/ANS8.5-1996  

Microsoft Academic Search

American National Standards Institute\\/American Nuclear Society (ANSI\\/ANS)-8.5 is one of several standards prepared by the ANS Standards Committee to provide guidance to enhance criticality safety in the handling, storage, and processing of fissionable materials. American National Standard ANSI\\/ANS-8.5-1996 provides this guidance for one type of boron-loaded glass in one type of geometry (cylindrical rings) for use with fissile solutions. Recorded

R. E. Rothe; N. Ketzlach; D. R. Finch

1996-01-01

319

Generalized Radar Output Simulation.  

National Technical Information Service (NTIS)

Using the outputs from the simulation of overall body motion related to observations at a complex of earth stations, this report develops a model for generating the scattering matrix and radar output voltages. The general multistatic case is treated using...

J. F. A. Ormsby S. H. Bickel

1969-01-01

320

Multimode Radar Altimeter (MRA).  

National Technical Information Service (NTIS)

Multimode radar altimeter functions in the Comet Nucleus Sample Return mission are described. Range measurement gives distance information for navigation; angle tracking can be performed by optical systems. Velocity (three axes) can be obtained by Doppler...

G. Picardi C. Dai R. Seu A. Coradini

1988-01-01

321

Radar Techniques Program.  

National Technical Information Service (NTIS)

This is the fifth Quarterly Technical Summary covering the development of an airborne Multiple-Antenna Moving-Target Surveillance Radar (MASR) which employs special antenna and signal-processing techniques to provide continuous, wide-area surveillance of ...

C. E. Muehe

1974-01-01

322

Incoherent radar spectra  

Microsoft Academic Search

General expressions for the incoherent scatter spectra are presented. These are relevant for the UHF radar in the monostatic backscatter case (thus excluding only the effect of the magnetic field), based on the Nyquist approach.

Matti K. Vallinkoski

1987-01-01

323

Ultra-wideband radar  

Microsoft Academic Search

Here, we present a description of a block scheme, characteristics, specific features of design and results of testing for a prototype of the ultrawideband (UWB) radar, which has been developed by Russian UWB group researchers at Moscow Aviation Institute at \\

I. Immoreev; E. Ziganshin

2004-01-01

324

Radar investigation of asteroids  

NASA Astrophysics Data System (ADS)

For 80 Sappho, 356 Liguria, 694 Ekard, and 2340 Hathor, data were taken simultaneously in the same sense of circular polarization as transmitted (SC) as well as in the opposite (OC) sense. Graphs show the average OC and SC radar echo power spectra soothed to a resolution of EFB Hz and plotted against Doppler frequency. Radar observations of the peculiar object 2201 Oljato reveal an unusual set of echo power spectra. The albedo and polarization ratio remain fairly constant but the bandwidths range from approximately 0.8 Hz to 1.4 Hz and the spectral shapes vary dramatically. Echo characteristics within any one date's approximately 2.5-hr observation period do not fluctuate very much. Laboratory measurements of the radar frequency electrical properties of particulate metal-plus-silicate mixtures can be combined with radar albedo estimates to constrain the bulk density and metal weight, fraction in a hypothetical asteroid regolith having the same particle size distribution as lab samples.

Ostro, S. J.

325

Theory of Adaptive Radar  

Microsoft Academic Search

This paper reviews the principles of adaptive radar in which both the spatial (antenna pattern) and temporal (Doppler filter) responses of the system are controlled adaptively. An adaptive system senses the angular-Doppler distribution of the external noise field and adjusts a set of radar parameters for maximum signal-to-interference ratio and optimum detection performance. A gradient technique for control of the

L. E. Brennan; L. S. Reed

1973-01-01

326

Radar in transition  

Microsoft Academic Search

It is pointed out that radar engineers, at the end of 1984, find their field in transition between the conventional designs of the post War II era and the digitally controlled, solid-state systems which will be in place for the year 2000. The U.S. Navy has two major phased array radar systems in operation, including the rotating three-dimensional (3D) AN\\/SPS-48,

D. K. Barton

1984-01-01

327

Terminal Doppler weather radar  

Microsoft Academic Search

The terminal Doppler weather radar (TDWR) system, now under development, will provide automatic detection of microbursts and low-level wind shear. This paper discusses the TDWR performance parameters and describes its structural elements, including the antenna subsystem, the transmitter, the receiver\\/exciter, the digital signal processor, and the radar product generator\\/remote monitoring subsystem. Attention is also given to the processes of the

M. Michelson; W. W. Shrader; J. G. Wieler

1990-01-01

328

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

SciTech Connect

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

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

1996-10-01

329

Mechanical energy absorber  

NASA Astrophysics Data System (ADS)

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

Wesselski, Clarence J.

1993-07-01

330

Mechanical energy absorber  

NASA Astrophysics Data System (ADS)

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

Wesselski, Clarence J.

1995-06-01

331

A Panel for Selectively Absorbing Solar Thermal Energy and the Method for Manufacturing the Panel.  

National Technical Information Service (NTIS)

A panel for selectively absorbing solar thermal energy is reported that consists of a metallic substrate, a layer of bright metallic material carried on the substrate, and a solar thermal energy absorbing coating carried on the bright metallic material. A...

J. R. Lowery

1974-01-01

332

Determination of ginsenoside content in Panax ginseng C.A. Meyer and Panax quinquefolius L. root materials and finished products by high-performance liquid chromatography with ultraviolet absorbance detection: interlaboratory study.  

PubMed

An interlaboratory study was conducted on an HPLC method with UV absorbance detection, previously validated using AOAC single-laboratory validation guidelines, for the determination of the six major ginsenosides (Rg1, Re, Rb1, Rc, Rb2, and Rd) in Panax ginseng C.A. Meyer and Panax quinquefolius L. root materials, extracts, and finished products. Fourteen participating laboratories analyzed five test materials (P. ginseng whole root, P. ginseng powdered extract, P. quinquefolius whole root, P. quinquefolius powdered extract, and P. ginseng powdered extract spiked in a matrix blank) as blind duplicates, and two test materials (P. ginseng powdered whole root tablet and P. quinquefolius powdered extract hard-filled capsule) as single samples. Due to the variability of the ginsenosides (low level concentration of Rb2 in P. quinquefolius raw materials and in P. ginseng spiked matrix blanks, and the possibility of incomplete hydrolysis of the finished products during processing), it was deemed more applicable to analyze total ginsenosides rather than individual ones. Outliers were evaluated and omitted using the Cochran's test and single and double Grubbs' tests. The reproducibility RSD (RSD(R)) for the blind duplicate samples ranged from 4.38 to 5.39%, with reproducibility Horwitz Ratio (HorRat(R)) values ranging from 1.5 to 1.9. For the single replicate samples, the data sets were evaluated solely by their repeatability HorRat (HorRat(r)), which were 2.9 and 3.5 for the capsule and tablet samples, respectively. Based on these results, the method is recommended for AOAC Official First Action for the determination of total ginsenosides in P. ginseng and P. quinquefolius root materials and powdered extracts. PMID:23513950

Brown, Paula N; Yu, Ronan; Cain, T; Huie, G; Jin, C D; Kababick, J N; Leong, G; LeVanseler, K; Lunetta, S; Ma, Y C; Reif, K; Schaneberg, B; Shevchuk, C; Smith, R; Sullivan, D; Wijewickreme, N; Windust, A

333

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

334

Bistatic Radar In Space A New Dimension In Imaging Radar  

Microsoft Academic Search

Based on a set of examples, this paper shows that bistatic space radar systems can have important capabilities for special imaging radar applications. It explains' the different categories of bistatic space radars as there are single orbit systems, crossing orbit systems, tethered systems and systems with geostationary\\/ge osynchronous transmitters (GEO-BISAR). It discusses the ideas of mixed systems, where aircrafts are

Hans Martin Braun; Philipp Hartl

1989-01-01

335

Studies on Radar and Non-radar Sensor Networks.  

National Technical Information Service (NTIS)

During the period of 12/1/2005--5/30/2006, we expanded our research from generic wireless sensor networks to radar sensor networks. For radar sensor networks, we performed the following preliminary studies: (1) Waveform design and diversity in radar senso...

Q. Liang

2006-01-01

336

33. Perimeter acquisition radar building room #320, perimeter acquisition radar ...  

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

33. Perimeter acquisition radar building room #320, perimeter acquisition radar operations center (PAROC), contains the tactical command and control group equipment required to control the par site. Showing spacetrack monitor console - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

337

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

338

Passive coherent location radar demonstration  

Microsoft Academic Search

This paper describes a passive coherent location (PCL) radar system developed by Dynetics, Inc. This system uses commercial FM broadcast signals for the radar waveform. This paper presents a technical description of the system and performance data.

C. L. Zoeller; M. J. Moody

2002-01-01

339

Terahertz radar cross section measurements  

Microsoft Academic Search

We present the result of terahertz radar cross section measurements on various objects including models of aircraft fighters. Application of a time domain system provides both values of radar cross section and ranging information.

Krzysztof Iwaszczuk; Henning Heiselberg; Peter Uhd Jepsen

2010-01-01

340

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

341

Coherent backscatter and the radar characteristics of outer planet satellites  

Microsoft Academic Search

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

Bruce Hapke

1990-01-01

342

The Clementine Bistatic Radar Experiment  

Microsoft Academic Search

During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, beta, for selected lunar areas. Observations of the lunar south pole yield a same-sense polarization enhancement around beta = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar

S. Nozette; C. L. Lichtenberg; P. Spudis; R. Bonner; W. Ort; E. Malaret; M. Robinson; E. M. Shoemaker

1996-01-01

343

Scanning ARM Cloud Radar Handbook.  

National Technical Information Service (NTIS)

The scanning ARM cloud radar (SACR) is a polarimetric Doppler radar consisting of three different radar designs based on operating frequency. These are designated as follows: (1) X-band SACR (X-SACR); (2) Ka-band SACR (Ka-SACR); and (3) W-band SACR (W-SAC...

K. Johnson K. Widener N. Bharadwaj

2012-01-01

344

The Venus Radar Mapper mission  

Microsoft Academic Search

The Venus Radar Mapper (VRM) mission is sponsored by NASA to put a single spacecraft in orbit around Venus to map the surface using a synthetic aperture mapping radar. This paper describes the VRM mission at its present state of design. The science objectives and project constraints are described. Key features of the spacecraft system and radar system are discussed.

E. Cutting; J. H. Kwok; S. N. Mohan

1984-01-01

345

Interception of LPI radar signals  

Microsoft Academic Search

Most current radars are designed to transmit short duration pulses with relatively high peak power. These radars can be detected easily by the use of relatively modest EW intercept receivers. Three radar functions (search, anti-ship missile (ASM) seeker, and navigation) are examined to evaluate the effectiveness of potential low probability of intercept (LPI) techniques, such as waveform coding, antenna profile

Jim P. Lee

1991-01-01

346

A radar tour of Venus  

Microsoft Academic Search

The surface of Venus is briefly characterized in a summary of results obtained by the Soviet Venera 15 and 16 8-cm synthetic-aperture radars, IR radiometers, and radar altimeters. A series of radar images, mainly from Kotelnikov et al. (1984), are presented and discussed, and the descent vehicles to be released by the two Vega spacecraft as they pass Venus in

J. K. Beatty

1985-01-01

347

Radar model with terrain effects  

NASA Astrophysics Data System (ADS)

This thesis presents a novel naval radar model which computes radar detection in the presence of land masses. The model is an interactive computer program which accepts scenarios and radar parameters from the user and displays a map of the area indicating where targets can and cannot be detected. The resulting map can be displayed at the user's computer terminal or printed offline.

Meritt, J. W.

1982-03-01

348

The Shuttle Radar Topography Mission  

Microsoft Academic Search

The Shuttle Radar Topography Mission produced the most complete, highest-resolution digital elevation model of the Earth. The project was a joint endeavor of NASA, the National Geospatial-Intelligence Agency, and the German and Italian Space Agencies and flew in February 2000. It used dual radar antennas to acquire interferometric radar data, processed to digital topographic data at 1 arc sec resolution.

Tom G. Farr; Paul A. Rosen; Edward Caro; Robert Crippen; Riley Duren; Scott Hensley; Michael Kobrick; Mimi Paller; Ernesto Rodriguez; Ladislav Roth; David Seal; Scott Shaffer; Joanne Shimada; Jeffrey Umland; Marian Werner; Michael Oskin; Douglas Burbank; Douglas Alsdorf

2007-01-01

349

Studies on Radar Sensor Networks.  

National Technical Information Service (NTIS)

During the period of 12/8/2006-6/30/2007, we performed the following studies in radar sensor network: (1) Sense-through-foliage target detection using UWB radar sensor network based on real-world data; (2) Foliage clutter modeling using UWB radars; (3) Ou...

Q. Liang

2007-01-01

350

Pulse-Doppler UWB Radar  

Microsoft Academic Search

The paper contains measurement results of moving targets by pulse-Doppler UWB radar. The description of a radar, principle of operation and technical specification are presented. Conditions and results of measurements are described. Feature of the presented measurements: Doppler signals of linear moving targets whose linear sizes exceed resolution of radar

A. Chernenko; E. Ziganshin

2006-01-01

351

Millimeter Radar Sea Return Study.  

National Technical Information Service (NTIS)

A site selection process was performed for a planned field exercise to measure radar sea clutter reflectivity at low grazing angles using several radar frequencies between 9.5 and 95 GHz. A detailed test plan was developed to collect calibrated radar cros...

R. N. Trebits

1979-01-01

352

Polarimetric Monopulse Radar Intelligent Emulator  

Microsoft Academic Search

For debugging polarimetric monopulse radar and testing polarization algorithms, a new polarimetric monopulse radar intelligent emulator is proposed and designed in this paper. The polarization information, as a basic character of the target echo, plays an important role in modern radar detection nowadays. The polarization algorithms are developed with rapid speed. It is not realistic to test all algorithms on

Jin Tao; Qi Xiaohui; Yuan Shuqing; Qiao Xiaolin; Zhang Min; Zhang Qunxing

2007-01-01

353

Synthetic Aperture Radar Signals: Formulations and Approaches for Data Analysis.  

National Technical Information Service (NTIS)

This report discusses principles of synthetic aperture radar, properties of radar targets, characteristics of radar imagery, statistical analysis of radar imagery, and the application of modern data analysis.

A. B. Lucero P. Swerling L. Breiman

1975-01-01

354

Instrumental Principles of MST Radars and Incoherent Scatter Radars and the Configuration of Radar System Hardware.  

National Technical Information Service (NTIS)

The principle of pulse modulation used in the case of coherent scatter radars (MST radars) is discussed. Coherent detection and the corresponding system configuration is delineated. Antenna requirements and design are outlined and the phase-coherent trans...

J. Roettger

1989-01-01

355

Radar sector blanker  

NASA Astrophysics Data System (ADS)

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

Hall, Roger B.

1994-03-01

356

Coherent IR radar technology  

NASA Astrophysics Data System (ADS)

Recent progress in the development of coherent IR radar equipment is reviewed, focusing on the Firepond laser radar installation and the more compact systems derived for it. The design and capabilities of Firepond as a long-range satellite-tracking device are outlined. The technological improvements necessary to make laser radar mobile are discussed: a lightweight, stable 5-10-W transmitter laser for both CW and pulsed operation, a 12-element HgCdTe detector array, an eccentric-pupil Ritchey-Chretien telescope, and a combination of near-field phase modification and anamorphic expansion to produce a fan beam of relatively uniform intensity. Sample images obtained with a prototype system are shown, and the applicability of the mobile system to range-resolved coherent DIAL measurement is found to be similar to that of a baseline DIAL system.

Gschwendtner, A. B.; Harney, R. C.; Hull, R. J.

357

Ground based radar  

NASA Astrophysics Data System (ADS)

The current state of turmoil in the world of ballistic missile technology dictates that the U.S. be prepared to deal with a growing ballistic missile threat. To meet this challenge the U.S. Army is developing a new family of ground based radar to support both the Theater Missile Defense and the Strategic Defense Initiatives. This class of radar provides affordable, reliable tracking and discrimination based on mature technology and commonality of design. The commonality of design concept uses technology and components that can be scaled in number, size, and capability. This approach allows ground based radar to support the near term requirements of both tactical and strategic defense and also provide flexibility for more sophisticated future threats.

Ryan, William W.

358

Flashlight radar: A three-dimensional imaging radar  

NASA Astrophysics Data System (ADS)

In support of several programs at Lincoln Laboratory, a small focused-beam polarimetric, millimeter-wave radar scatterometer (an instrument for measuring radar cross section) has been developed. An overview of the design of this Flashlight Radar is presented. Theoretical and empirical studies of antenna performance are discussed. The backscatter theory relating to the characteristics of the Flashlight Radar as a scatterometer is presented, and experimental RCS measurements are compared with theoretical predictions. The data processing steps (polarimetric calibration and compensation, signal processing, and image formation) are described. We show the results of two representative experiments using the Flashlight Radar. The first is a measurement of dihedral and trihedral reflectors with and without radar camouflage. The second is a faster scan of a truck tire, highlighting the radar's fine resolution and its ability to collect three-dimensional data.

Blejer, Dennis J.; Ferranti, Richard L.; Barnes, Richard M.; Irving, William W.; Verbout, Shawn M.

1989-08-01

359

Radar detection of phobos.  

PubMed

Radar echoes from the martian satellite Phobos provide information about that object's surface properties at scales near the 3.5-cm observing wavelength. Phobos appears less rough than the moon at centimeter-to-decimeter scales. The uppermost few decimeters of the satellite's regolith have a mean bulk density within 20% of 2.0 g cm(-3). The radar signature of Phobos (albedo, polarization ratio, and echo spectral shape) differs from signatures measured for small, Earth-approaching objects, but resembles those of large (>/=100-km), C-class, mainbelt asteroids. PMID:17847261

Ostro, S J; Jurgens, R F; Yeomans, D K; Standish, E M; Greiner, W

1989-03-24

360

Threat radar system simulations  

NASA Astrophysics Data System (ADS)

The capabilities, requirements, and goals of radar emitter simulators are discussed. Simulators are used to evaluate competing receiver designs, to quantify the performance envelope of a radar system, and to model the characteristics of a transmitted signal waveform. A database of candidate threat systems is developed and, in concert with intelligence data on a given weapons system, permits upgrading simulators to new projected threat capabilities. Four currently available simulation techniques are summarized, noting the usefulness of developing modular software for fast controlled-cost upgrades of simulation capabilities.

Miller, L.

361

Terminal Doppler weather radar  

NASA Astrophysics Data System (ADS)

The terminal Doppler weather radar (TDWR) system, now under development, will provide automatic detection of microbursts and low-level wind shear. This paper discusses the TDWR performance parameters and describes its structural elements, including the antenna subsystem, the transmitter, the receiver/exciter, the digital signal processor, and the radar product generator/remote monitoring subsystem. Attention is also given to the processes of the base data formation, point target removal, signal-to-noise thresholding, and velocity de-aliasing and to the TDWR algorithms and displays. A schematic diagram of the TDWR system is presented.

Michelson, M.; Shrader, W. W.; Wieler, J. G.

1990-02-01

362

Wavelets and impulse radar  

NASA Astrophysics Data System (ADS)

The signal generated by avalanche discharge circuitry that drives optical flash for cameras is ultra wideband and suitable as the excitation waveform for an Impulse Radar when transmitted through an appropriate antenna. In this paper, we experimentally and theoretically show that the Impulse Radar's radiated transmitted EM waves satisfy the admissibility condition of wavelets, i.e. (i) a finite power spectral density psd=<|S(f)|2>< and (ii) zero total area under the undulated wave amplitudes. If the radiated environment is linear (the natural scene), then the received signal also satisfies the admissibility condition.

Szu, Harold; Hsu, Charles; Scheff, Kim; Hansen, Peter; Willey, Jeff

2009-04-01

363

Ultrasonic waves propagation in absorbing thin plates  

Microsoft Academic Search

Guided wave theory is applied to a thin orthotropic and absorbing plate for low frequency propagation of ultrasonic waves. The aim of this paper is to give some physical interpretations of the non-destructive characterization of paper materials, which are cellulosic fibrous networks. It is shown that the propagation problem reduces to two normal modes of propagation in the plane of

A. Bonnin; R. Huchon; M. Deschamps

2000-01-01

364

Meteor studies applying incoherent scatter radar instruments  

NASA Astrophysics Data System (ADS)

Meteors appear in the ionosphere during the entry of solid particles, so-called meteoroids, from interplanetary space. Meteors are observed by the partial ionization of meteoroid and atmospheric material that is generated during the entry of the solid particles. The ionization is associated with optical emission (optical meteors) and it reflects radio waves (radio meteors). The radar backscattering is sensitive to objects that are too small to be detected optically and the sensitivity for observing radio meteors varies with the radio frequency used for the observation. Incoherent scatter radar facilities detect in majority sporadic meteors by their head echoes that originate directly from the surrounding of the entering meteoroid, hence providing the opportunity for detailed studies of meteor phenomena on small scales. Meteors are typically observed at 120 km to 80 km altitudes where the mean free path of atmospheric neutral particles changes from meters to millimeters. The phased-array incoherent scatter radars that are currently under development, such as the planned EISCAT_3D system in northern Scandinavia, will further improve the spatial and time resolution of radar observations, will allow simultaneous measurements of the meteors and of the parameters of the surrounding ionosphere and will possibly allow observing the formation of meteoric smoke particles associated with meteors. In this presentation we consider the possibilities for measurements with the future EISCAT 3D as a new path of studying the physics of meteor phenomena with high accuracy.

Mann, I.; Pellinen-Wannberg, A.; Tjulin, A.

2012-04-01

365

Bistatic synthetic aperture radar  

Microsoft Academic Search

Synthetic aperture radar (SAR) is becoming increasingly important in many military ground surveillance and targeting roles because of its ability to operate in all weather, day and night, and to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and receiver are on separate platforms, is seen as a potential means of countering vulnerability. This

A. M. Horne; G. Yates

2002-01-01

366

Goldstone solar system radar  

Microsoft Academic Search

Information is provided about physical nature planetary surfaces and their topography as well as dynamical properties such as orbits and spin states using ground based radar as a remote sensing tool. Accessible targets are the terrestrial planets: the Earth's Moon, Mercury, Venus and Mars, the outer planets rings and major moons, and many transient objects such as asteroids and comets.

R. F. Jurgens; P. E. Clark; R. M. Goldstein; S. J. Ostro; M. A. Slade; T. W. Thompson; R. S. Saunders

1986-01-01

367

Airborne firefinder radar concept  

Microsoft Academic Search

An airborne firefinder radar (AFFR) is suggested for an upgraded version of the forthcoming Global Hawk Unmanned Aerial Vehicle (UAV). The AFFR could detect an artillery shell within 1 second of firing and, within a few seconds, determine its trajectory origin location (position of the gun) to a circular error probable (CEP) of less than 50 meters. The AFFR could

R. J. Sullivan; J. F. Nicoll; J. M. Ralston

1998-01-01

368

Doppler Radar System.  

National Technical Information Service (NTIS)

The radar system is utilized to guide a fused guided missile to an aircraft target. The secondary doppler effects are utilized between a moving object and a secondary reflecting surface to detect the presence of the object and indicate its point of closes...

A. E. Resnik

1964-01-01

369

Mars 96 subsurface radar  

Microsoft Academic Search

The Mars 96 International Scientific Mission to launch an aerostat that will drift in the Martian atmosphere for ten days is described. The stabilizing element of the aerostat (guiderope) will be dragged on the Martian surface every night. A ground penetrating radar will be installed within the guiderope. Its external surface will act as a transmit and receive antenna. A

Y. Barbin; W. Kofman; M. Elkine; M. Finkelstein; V. Glotov; V. Zolotarev

1991-01-01

370

Passive Radar Tracking Apparatus.  

National Technical Information Service (NTIS)

The radar system tracks a target whether it generates a signal of its own or not and may be used to sense noise energy radiated by the sun, other objects, or other celestial bodies. The system includes an antenna assembly of four horns arranged in a recta...

D. K. Barton W. J. Rose

1965-01-01

371

Comet radar explorer  

Microsoft Academic Search

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

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

2010-01-01

372

Pulse Doppler radar waveforms  

Microsoft Academic Search

Modern military airborne radars are highly sophisticated, multi-mode systems which are required to detect difficult targets in all aspects and over a large range\\/velocity detection space. There are particular difficulties associated with the airborne case such as the limited antenna aperture, high platform velocity and severe clutter levels which present difficult waveform design challenges. This tutorial will consider the design

C. M. Alabaster

2010-01-01

373

Laser Radar Development.  

National Technical Information Service (NTIS)

A range-gated imaging (RGI) laser radar system was constructed and field-tested at the Chesapeake Bay Division of the Naval Research Laboratories to evaluate the capability of RGI systems to provide extremely high contrast image displays. The system emplo...

J. A. Jenney

1968-01-01

374

Laser Imaging Radar System.  

National Technical Information Service (NTIS)

The simplicity, compactness, and reasonable cost of direct detection diode-laser range finders provide incentive for their use in laser imaging radar systems (LIRS). Efforts have been made to increase range performance of a diode-laser range finder by mea...

S. P. Yun R. A. Olson

1993-01-01

375

Crosshole radar velocity tomography with finite-frequency Fresnel volume sensitivities  

Microsoft Academic Search

SUMMARY Crosshole-radar velocity tomography is increasingly being used to characterize the electrical and hydrologic properties of the Earth's near-surface. Because radar methods are sensitive to the water content of geologic materials, velocity tomography is a good proxy for imaging soil water retention in the vadose zone and porosity in the saturated zone. In many near-surface envi- ronments, radar velocity varies

Marc L. Buursink; Timothy C. Johnson; Partha S. Routh; Michael D. Knoll

2008-01-01

376

Current radar responsive tag development activities at Sandia National Laboratories.  

SciTech Connect

Over the past ten years, Sandia has developed RF radar responsive tag systems and supporting technologies for various government agencies and industry partners. RF tags can function as RF transmitters or radar transponders that enable tagging, tracking, and location determination functions. Expertise in tag architecture, microwave and radar design, signal analysis and processing techniques, digital design, modeling and simulation, and testing have been directly applicable to these tag programs. In general, the radar responsive tag designs have emphasized low power, small package size, and the ability to be detected by the radar at long ranges. Recently, there has been an interest in using radar responsive tags for Blue Force tracking and Combat ID (CID). The main reason for this interest is to allow airborne surveillance radars to easily distinguish U.S. assets from those of opposing forces. A Blue Force tracking capability would add materially to situational awareness. Combat ID is also an issue, as evidenced by the fact that approximately one-quarter of all U.S. casualties in the Gulf War took the form of ground troops killed by friendly fire. Because the evolution of warfare in the intervening decade has made asymmetric warfare the norm rather than the exception, swarming engagements in which U.S. forces will be freely intermixed with opposing forces is a situation that must be anticipated. Increasing utilization of precision munitions can be expected to drive fires progressively closer to engaged allied troops at times when visual de-confliction is not an option. In view of these trends, it becomes increasingly important that U.S. ground forces have a widely proliferated all-weather radar responsive tag that communicates to all-weather surveillance. The purpose of this paper is to provide an overview of the recent, current, and future radar responsive research and development activities at Sandia National Laboratories that support both the Blue Force Tracking and Combat ID application.

Plummer, Kenneth W.; Ormesher, Richard C.

2003-09-01

377

Absorption cross section of absorber cylinders  

NASA Astrophysics Data System (ADS)

The paper covers derivation and calculation of absorption and scattering cross sections of three types of cylinders made out of porous absorber material. These types are, respectively, (a) completely bulk reacting (homogeneous and isotropic), (b) axially locally reacting but bulk reacting about the circumference (rigid partitions inserted normal to the cylinder's axis), and (c) locally reacting in all directions. The sound field may be either plane waves with oblique incidence or diffuse sound fields. The characteristic data used for the absorber materials, propagation constant and wave impedance, are in the form of simple approximations taken from a model theory of fibrous absorbers for low frequencies, with experimental data being used at medium and high frequencies. A formulation of the scattered sound field in series of Bessel function is used. The numerical results show the influence of the frequency, the diameter, the materials' flow resistance and the angle of incidence. Maps are plotted of lines of constant absorption cross-sections for the different types of cylinders and sound fields, revealing the dependence upon these parameters. Acoustical phenomena of the sound absorption by absorber cylinders are discussed, such as resonance scattering, surface waves, frequency ranges with small angular dependence and parameter combinations with only small frequency dependence of the absorption. Such cylinders would be appropriate as calibration objects in round robin tests of sound absorption measurement in reverberant rooms.

Mechel, F. P.

1986-05-01

378

Characteristics and optimization of radar target with plasma cover  

NASA Astrophysics Data System (ADS)

In this paper, we investigated the characteristic of radar target, the spherical and the pyramidal missile warheads, and compared the RCS and performance of the targets with and without the cover of the plasma metamaterials. Numerical simulation is obtained by the numerical calculation Finite-difference time-domain method (FDTD). The parameters of plasmonic structures as a metamaterial cloak was designed and optimized. The relationship between the parameters of the cloak and the corresponding electromagnetic characteristic of the target are analyzed by the simulation and discussion in broadband radar signals. After optimization, the plasma cover could attenuate 40 dBsm of the radar cross section (RCS) of the targets maximally. The result shows that the anomalous phenomenon of cloaking and stealth effects induced by plasma materials for the radar target, which might have potential application of military affairs.

Yang, Ying-ying; Zhao, Wei-fang; Wang, Wen-ting; Yi, Xiao-jing; Ji, Jun-wen; Lin, Xue-chun

2013-09-01

379

Reusable oil absorbent bilge and fuel tank opening pads  

Microsoft Academic Search

For removing oil from the bilge area and fuel tank filler area of a boat, an oil absorbent pad is constructed with an outer wide mesh structural envelope confining and reinforcing an inner containment envelope of woven synthetic crepe material that will absorb oil with a wicking action while repelling water and which will contain therein granular open pore synthetic

Pedone

1977-01-01

380

Can the radar penetrate Martian polar deposits ?  

NASA Astrophysics Data System (ADS)

Layered stratigraphy of Martian polar deposits is believed %thought to contain a record of climatic history of Mars. Investigation %Exploration of stratigraphy of Martian polar sheets %by means of ground-penetrating radar would provide valuable information about the history and evolution of the planet and its water balance. An appropiate instrument for deep investigation of polar deposits is a ground-penetrating radar (GPR). Propagation of electromagnetic waves through such a complicated medium like Martian polar layered deposits are governed by two kinds of factors. Physical and chemical composition of the polar sheets determines its electrical properties, i.e. wave velocity and attenuation. On the other hand, layered structure of polar sheets and its geometrical parameters regulate dispersive properties of such medium. We simulated radio wave propagation in polar sheets under various assumptions about both these groups of parameters, both analytically and numerically. Basic dispersive properties of studied inhomogeneous medium were inferred from the solution of dispersion equation for regularly periodical medium (the Kronig-Penney problem). The geometrical parameters of the structure were chosen equal to characteristic parameters of real polar layered deposits, inferred from published observational data. Also immediate numerical simulations of ultra wide band (UWB) radar signals, propagated through polar sheets, were performed. Electrical properties of material of polar sheets varied in wide range of values, according to published results on physical and chemical composition of polar sheets. We found that, under most commonly made assumptions on chemical composition, the characteristic geometrical parameters of layered structure imply significant disptortion of radar signals at frequencies higher than 1 MHz. For this reason, a low frequency ( below 1 MHz ) radar appears to be better choise for investigation of Martian polar sheets.

Ilyushin, Ya. A.

381

51. View of upper radar scanner switch in radar scanner ...  

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

51. View of upper radar scanner switch in radar scanner building 105 from upper catwalk level showing emanating waveguides from upper switch (upper one-fourth of photograph) and emanating waveguides from lower radar scanner switch in vertical runs. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

382

Realistic Simulations Of Radar Scattering In Asteroids Using Geometric Optics  

NASA Astrophysics Data System (ADS)

We study the physical characteristics of asteroids that affect the circular-polarization ratio and the radar albedo at backscattering using simulations of radar scattering on asteroid surfaces. Previously, we have studied these radar parameters using aggregates of spheres and inhomogeneous spheres but without the multiple scattering effects that are relevant in realistic scattering by asteroid regolith. This time, we utilize geometric optics software for simulating electromagnetic scattering by the interacting single-scatterers (aggregated or inhomogeneous spheres) both on the surfaces of gaussian random spheres and inside them. We vary the physical parameters of the input single-scatterers as well as the refractive index and optical depth of the gaussian random spheres that simulate the asteroid in macroscopic scale. Thus, we investigate the effect of multiple scattering by various particles to the radar parameters and further develop their interpretation. The results are sensible in terms of the scale of the values of circular-polarization ratio and radar albedo as compared to the radar observations and show the well-known effect of multiple-scattering increasing the circular-polarization ratio for any particles. More importantly, the results show differences caused by the different physical parameters. For example, single-scatterers with smaller refractive indices (of, e.g., water ice) return smaller circular-polarization ratios and radar albedos compared to the particles with larger refractive indices (of, e.g., silicate materials or basalt). Also, the inhomogeneous spheres of size comparable to the wavelength can cause values of circular-polarization ratio and radar albedo a few times smaller than the spheres that are half the size but of the same material, although it is generally believed that specifically wavelength-scale roughness is the main cause of high circular-polarization ratios. This means that the effect of the scale of the surface structures, without forgetting the other physical properties, requires further investigation.

Virkki, Anne; Muinonen, K.; Penttilä, A.

2013-10-01

383

A modular wideband sound absorber  

NASA Astrophysics Data System (ADS)

The absorption coefficients were measured of various depths of RW2 grade Rockwool laid directly on the floor of the ISO-Standard reverberation room at BBC Research Department. The Rockwool was very effective as a wideband sound absorber. A new absorber was designed and tested, having the dimensions of the existing BBC type A modular absorbers and containing RW2 Rockwool. The new absorber has a smoother absorption coefficient curve, a less complicated construction, and weighs less than the existing BBC wideband absorber (type A8/A9). It has been named type A11 and has an equivalent performance to that of BBC type A2 and A3 absorbers combined. It complements, very well, the performance of the A10 very low frequency absorber, described in a companion Report (BBC RD No. 1992/10).

Plumb, G. D.

384

Real-time modeling of a radar sensor for enhanced vision  

NASA Astrophysics Data System (ADS)

Millimetric radar imaging systems have been used to improve situational awareness for flight crew in low visibility approaches. The image from the sensor is projected in a Head-Up Display (HUD) and, for aircraft without Cat-III auto-land facilities, can provide sufficient cues to continue a manual approach past the normal decision height. However, these images may be cluttered, features are often difficult to detect and there is no direct indication of system integrity. Guidance cues can be displayed in the HUD by tracking runway features in the radar image and the use of sensor fusion methods to detect variation in the size and shape of the runway can provide integrity monitoring, for timely warning of system malfunction. In order to develop real-time tracking algorithms, it is necessary to generate synthetic radar images, which exhibit the properties of actual millimetric radar sensors. This paper outlines the model of a radar sensor used to generate real-time radar images incorporating appropriate attenuation and clutter properties. These images are derived from standard 3D visual databases and have been integrated in a flight simulator using a commercial image generation system. The radar model incorporates the effects of material properties of objects, the sensor range and grazing angles and includes atmospheric attenuation. Examples of the radar images are presented in the paper together with a summary of the real-time performance of the radar model to simulate millimeter wave radar images using a proprietary workstation.

Allerton, David J.; Clare, Anthony J.

2003-09-01

385

An OTH radar clutter simulation  

NASA Astrophysics Data System (ADS)

A computer simulation is described which was developed with the objective of arriving at an understanding of OTH radar clutter originating in the equatorial ionosphere. This source of clutter is of particular interest in OTH radar, since all radar propagation paths must pass through the equatorial region, even if the desired targets are far removed from it. A central feature of the simulation is an ionospheric propagation model developed to synthesize OTH radar clutter by making use of state-of-the art models for global ionospheric structure, including small-scale irregularities, and combining these with efficient ray tracing procedures and a multiple phase-screen approach to computing the diffraction of radar energy by the irregular ionosphere. Simulated clutter data is compared to actual measurements using several radars, with generally satisfactory results.

Providakes, J.; Elkins, T. J.; Godwin, R. B.; Kelley, M. C.

1991-12-01

386

Radar Experiments Data Reduction, and Experimental Tests.  

National Technical Information Service (NTIS)

Work performed included software support for the evaluation and development of advanced radar antenna systems, development and maintenance of target identification databases, and the data reduction of raw radar data from field tests. Keywords: Radar anten...

W. O. Loescher

1990-01-01

387

Floor-plan radar  

NASA Astrophysics Data System (ADS)

Urban-warfare specialists, law-enforcement officers, counter-drug agents, and counter-terrorism experts encounter operational situations where they must assault a target building and capture or rescue its occupants. To minimize potential casualties, the assault team needs a picture of the building's interior and a copy of its floor plan. With this need in mind, we constructed a scale model of a single- story house and imaged its interior using synthetic-aperture techniques. The interior and exterior walls nearest the radar set were imaged with good fidelity, but the distal ones appear poorly defined and surrounded by ghosts and artifacts. The latter defects are traceable to beam attenuation, wavefront distortion, multiple scattering, traveling waves, resonance phenomena, and other effects not accounted for in the traditional (noninteracting, isotropic point scatterer) model for radar imaging.

Falconer, David G.; Ueberschaer, Ronald M.

2000-07-01

388

Ultrawideband radars: Features and capabilities  

Microsoft Academic Search

Features of ultrawideband (UWB) radars, which radiate signals whose spatial duration is substantially smaller than the antenna\\u000a dimensions and\\/or the longitudinal dimension of the illuminated target, are analyzed. It is shown that, during the radar observation\\u000a of the target, this signal changes its shape several times and enters the radar receiver as an unknown signal. In many cases,\\u000a this circumstance

I. Ya. Immoreev

2009-01-01

389

Imaging synthetic aperture radar  

DOEpatents

A linear-FM SAR imaging radar method and apparatus to produce a real-time image by first arranging the returned signals into a plurality of subaperture arrays, the columns of each subaperture array having samples of dechirped baseband pulses, and further including a processing of each subaperture array to obtain coarse-resolution in azimuth, then fine-resolution in range, and lastly, to combine the processed subapertures to obtain the final fine-resolution in azimuth. Greater efficiency is achieved because both the transmitted signal and a local oscillator signal mixed with the returned signal can be varied on a pulse-to-pulse basis as a function of radar motion. Moreover, a novel circuit can adjust the sampling location and the A/D sample rate of the combined dechirped baseband signal which greatly reduces processing time and hardware. The processing steps include implementing a window function, stabilizing either a central reference point and/or all other points of a subaperture with respect to doppler frequency and/or range as a function of radar motion, sorting and compressing the signals using a standard fourier transforms. The stabilization of each processing part is accomplished with vector multiplication using waveforms generated as a function of radar motion wherein these waveforms may be synthesized in integrated circuits. Stabilization of range migration as a function of doppler frequency by simple vector multiplication is a particularly useful feature of the invention; as is stabilization of azimuth migration by correcting for spatially varying phase errors prior to the application of an autofocus process.

Burns, Bryan L. (Tijeras, NM); Cordaro, J. Thomas (Albuquerque, NM)

1997-01-01

390

Radar techniques program  

Microsoft Academic Search

This is the fifth Quarterly Technical Summary covering the development of an airborne Multiple-Antenna Moving-Target Surveillance Radar (MASR) which employs special antenna and signal-processing techniques to provide continuous, wide-area surveillance of moving targets on or near the ground. Such a sensor, equipped with an appropriate data-reduction facility, can provide useful real-time information to a Tactical Air Control System. A DeHavilland

C. E. Muehe

1974-01-01

391

Tropopause detected by radar.  

PubMed

The tropopause has been detected by ultrasensitive, narrow-beam, microwave (10.7-centimeter) and ultrahigh-frequency (71.5-cm) radars. Its reflectivity is consistent with that expected theoretically for a refractively turbulent medium. Indications are that the layer is also mechanically turbulent, and that electromagnetic scatter techniques may be used to detect high-altitude clear-air turbulence. PMID:17737591

Atlas, D; Hardy, K R; Glover, K M; Katz, I; Konrad, T G

1966-09-01

392

Shuttle imaging radar experiment  

USGS Publications Warehouse

The shuttle imaging radar (SIR-A) acquired images of a variety of the earth's geologic areas covering about 10 million square kilometers. Structural and geomorphic features such as faults, folds, outcrops, and dunes are clearly visible in both tropical and arid regions. The combination of SIR-A and Seasat images provides additional information about the surface physical properties: topography and roughness. Ocean features were also observed, including large internal waves in the Andaman Sea. Copyright ?? 1982 AAAS.

Elachi, C.; Brown, W. E.; Cimino, J. B.; Dixon, T.; Evans, D. L.; Ford, J. P.; Saunders, R. S.; Breed, C.; Masursky, H.; Mccauley, J. F.; Schaber, G.; Dellwig, L.; England, A.; MacDonald, H.; Martin-Kaye, P.; Sabins, F.

1982-01-01

393

Millimeter Wave Cloud Radar (MMCR) Handbook  

SciTech Connect

The millimeter cloud radar (MMCR) systems probe the extent and composition of clouds at millimeter wavelengths. The MMCR is a zenith-pointing radar that operates at a frequency of 35 GHz. The main purpose of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops). This radar will also report radar reflectivity (dBZ) of the atmosphere up to 20 km. The radar possesses a doppler capability that will allow the measurement of cloud constituent vertical velocities.

KB Widener; K Johnson

2005-01-30

394

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

NASA Astrophysics Data System (ADS)

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 effective absorptivity while at the same time not giving rise to an overly large reflectivity. In this vein we here evaluate, as a function of frequency up to 20 GHz, the effective magnitudes of Re ? and Im ? for particulate composites and their dependence on the volume fraction ? of the particles, while independently varying conductivities. Our calculations are carried out using both the effective-medium theory (mixture theory, valid for small ?), and the multiple-scattering theory of Tsang and Kong valid for general ? but for small particle sizes. Multiple-scattering effects lead to increased effective absorptivities by adding scattering losses to the intrinsic losses of the media. We comment on the optimal values of the medium parameters and packing fractions for composite RAM materials. Percolation effects (transition from matrix dominance to particle dominance) are studied, both for the effective-medium theory and for the multiple-scattering theory, and compared for the two cases.

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

1999-09-01

395

An image-based approach for classification of human micro-doppler radar signatures  

NASA Astrophysics Data System (ADS)

With the advances in radar technology, there is an increasing interest in automatic radar-based human gait identification. This is because radar signals can penetrate through most dielectric materials. In this paper, an image-based approach is proposed for classifying human micro-Doppler radar signatures. The time-varying radar signal is first converted into a time-frequency representation, which is then cast as a two-dimensional image. A descriptor is developed to extract micro-Doppler features from local time-frequency patches centered along the torso Doppler frequency. Experimental results based on real data collected from a 24-GHz Doppler radar showed that the proposed approach achieves promising classification performance.

Tivive, Fok Hing Chi; Phung, Son Lam; Bouzerdoum, Abdesselam

2013-05-01

396

Radar clutter classification  

NASA Astrophysics Data System (ADS)

The problem of classifying radar clutter as found on air traffic control radar systems is studied. An algorithm based on Bayes decision theory and the parametric maximum a posteriori probability classifier is developed to perform this classification automatically. This classifier employs a quadratic discriminant function and is optimum for feature vectors that are distributed according to the multivariate normal density. Separable clutter classes are most likely to arise from the analysis of the Doppler spectrum. Specifically, a feature set based on the complex reflection coefficients of the lattice prediction error filter is proposed. The classifier is tested using data recorded from L-band air traffic control radars. The Doppler spectra of these data are examined; the properties of the feature set computed using these data are studied in terms of both the marginal and multivariate statistics. Several strategies involving different numbers of features, class assignments, and data set pretesting according to Doppler frequency and signal to noise ratio were evaluated before settling on a workable algorithm. Final results are presented in terms of experimental misclassification rates and simulated and classified plane position indicator displays.

Stehwien, Wolfgang

1989-11-01

397

The microwave absorbing phenomena of ferrite microwave absorbers  

Microsoft Academic Search

The complex permeability dispersions and the microwave absorbing phenomena are investigated in ferrite microwave absorbers. The complex permeability of hexagonal (Y- and Z-type) and spinel (NiZn ferrite and NiZnCo ferrite) ferrite microwave absorbers were measured in 200 MHz-16 GHz range. The theoretical matching frequencies are determined by plotting the measured complex permeability loci on the impedance matching solution map. One

J. Y. Shin; J. H. Oh

1993-01-01

398

Circular array radar technical and applications  

NASA Astrophysics Data System (ADS)

A new type circular array radar is introduced in this paper. First, the working theory of this radar is introduced, as well as the signal processing method. The characteristics and advancements of this type of radar are detailed analyzed, and the key technology of the circular array radar is proposed. Second, two applications of circular array radar are introduced; they are VHF circular array long-range surveillance radar and L band mini circular array radar. Finally, the potential prospect of this circular array radar is proposed.

Xu, Chengfa; Wang, Chonghui; Hong, Yongbin

2013-03-01

399

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

400

Topics in Mitigating Radar Bias  

Microsoft Academic Search

In this paper, we investigate two topics related to mitigating the effect of radar bias in ballistic missile tracking applications. We determine the absolute bias between two radars in polar coordinates when their relative bias is given in rectangular coordinates. Using this result, we then obtain the optimized steady-state filter to handle the random bias.

Demetrios Serakos; John E. Gray; Hazim Youssef

2008-01-01

401

Next Generation Incoherent Scatter Radars.  

National Technical Information Service (NTIS)

The 1990's promise to be an exciting time for users and practitioners of incoherent scatter radar as a new generation of radars is brought into operation at locations such as Svalbard, Resolute Bay, Alaska and Indonesia. Recent technological and theoretic...

J. M. Holt

1991-01-01

402

Radar Studies In Physical Volcanology  

Microsoft Academic Search

This paper discusses a number of projects currently underway at the University of Hawaii that involve airborne and orbital radar investigations of the styles of eruption and the geologic history of volcanoes on the Earth and Venus. The radar data have been derived from a NASA\\/JPL AIRSAR deployment to Hawaii in August 1990, the Magellan mission to Venus, and the

Peter J. Mouginis-Mark

1992-01-01

403

Decorrelation in interferometric radar echoes  

Microsoft Academic Search

A radar interferometric technique for topographic mapping of surfaces, implemented utilizing a single synthetic aperture radar (SAR) system in a nearly repeating orbit, is discussed. The authors characterize the various sources contributing to the echo correlation statistics, and isolate the term which most closely describes surficial change. They then examine the application of this approach to topographic mapping of vegetated

Howard A. Zebker; John Villasensor

1992-01-01

404

COBRA meteor radar antenna designs  

Microsoft Academic Search

A meteor radar system is one of the effective remote sensing techniques in measuring atmospheric parameters such as wind velocities, temperature, pressure and density which are essential in understanding the atmospheric dynamics in the Mesosphere Lower Thermosphere (MLT) region. Previous studies of very high frequency (VHF) meteors radar systems suggest that the minimum error for the estimation of the horizontal

Mohamad Zainuddin

2009-01-01

405

Imaging Radars for Geoscience Use  

Microsoft Academic Search

Properties of a side-looking airborne radar (SLAR) designed for geoscience rather than military use are presented. The speckled nature of usual single-frequency radar images may be reduced by averaging in azimuth and by averaging in range or transmitting excess range bandwidth. With synthetic aperture systems, averaging is possible in both range and azimuth, but only range averaging (excess bandwidth) is

R. K. Moore; G. C. Thomann

1971-01-01

406

Radar polarimetry for geoscience applications  

Microsoft Academic Search

The present volume on radar polarimetry for geoscience applications discusses wave properties and polarization, scattering matrix representation for simple targets, scattering models for point and distributed targets, polarimetric scatterometer systems and measurements, polarimetric radar system design, and polarimetric SAR applications. Attention is given to plane waves in a lossless homogeneous medium-wave polarization, polarization synthesis and response, and coordinate system transformations.

Fawwaz T. Ulaby; Charles Elachi; K. McDonald; K. Sarabandi; M. Whitt; H. Zebker; J. J. van Zyl

1990-01-01

407

A Multiband Passive Radar Demonstrator  

Microsoft Academic Search

Passive radar systems that exploit signals from the plethora of RF emissions that exist in the external environment offer a number of advantages over conventional active radar system, including procurement and operational cost saving. Each emitter has its own characteristics, including waveforms, which dictate system performance. BAE Systems Advanced Technology Centre has designed and built a demonstrator system to act

Dale Gould; Robert Pollard; Carlos Sarno; Paul Tittensor

2006-01-01

408

Radar noise jamming calculations simplified  

Microsoft Academic Search

The ratio of radar jamming noise power to radar thermal noise power (J\\/N) is considered for a multiple noise jammer environment where jammer distances and energy levels vary. It is shown that the computation of J\\/N in a multiple noise jammer environment may be significantly simplified in several practical cases by reducing each case to that of a single equivalent

G. P. Kefalas

1981-01-01

409

Environment-adaptive radar techniques  

Microsoft Academic Search

This report describes the work performed in the first year of a contract to investigate the measurement and mitigation of environmental effects in a selected modern radar system. The baseline system is a mobile ground-based tactical radar system which performs wide-area surveillance for aircraft targets as well as multiple target tracking for eventual handover. The dominant technical problem is found

J. E. Howard; G. W. Lank; A. W. Rihaczek

1981-01-01

410

Automotive Radar - Status and Trends  

Microsoft Academic Search

The paper gives a brief overview of automo- tive radar. The status of the frequency regulation for short and long range radar is summarized because of its impor- tance for car manufacturers and their sensor suppliers. Front end concepts and antenna techniques of 24 GHz and 77 GHz sensors are briefly described. Their impact on the sensor's field of view

Martin Schneider

411

UWB radar for patient monitoring  

Microsoft Academic Search

During the last few years the Moscow Aviation Institute (Russia) and the Industrial Technology Research Institute (Taiwan) have worked jointly on the development of ultrawideband (UWB) medical radars for remote and contactiess monitoring of patients in hospitals. Preliminary results of these works were published in [1]. As of the present, several radars have been produced and tested in real conditions

Igor Immoreev; Teh-Ho Tao

2008-01-01

412

Radar Studies of Bird Migration.  

National Technical Information Service (NTIS)

Observations of bird migration with NASA radars were made at Wallops Island, Va. Simultaneous observations were made at a number of radar sites in the North Atlantic Ocean in an effort to discover what happened to those birds that were observed leaving th...

T. C. Williams J. M. Williams

1974-01-01

413

Microwave Emissions from Police Radar  

Microsoft Academic Search

This study evaluated police officers' exposures to microwaves emitted by traffic radar units. Exposure measurements were taken at approximated ocular and testicular levels of officers seated in patrol vehicles. Comparisons were made of the radar manufacturers' published maximum power density specifications and actual measured power densities taken at the antenna faces of those units. Four speed-enforcement agencies and one transportation

J. M. Fink; J. P. Wagner; J. J. Congleton; J. C. Rock

1999-01-01

414

Resolution independent radar target recognition  

Microsoft Academic Search

The value of Through the Wall Radar Imaging (TWRI) data collected with one system is limited when training the automatic target recognition classifier of a second system because of variation in the Point Spread Function (PSF). The target image is a function of both the scene reflectivity and the PSF, which is in turn a function of the imaging radar's

Graeme E. Smith; Bijan G. Mobasseri

2011-01-01

415

Millimeter radar improves target identification  

NASA Astrophysics Data System (ADS)

Recently developed millimeter wave radar has advantages for target identification over conventional microwave radar which typically use lower frequencies. We describe the pertinent features involved in the construction of the new millimeter wave radar, the pseudo-optical cavity source and the quasi-optical duplexer. The long wavelength relative to light allows the radar beam to penetrate through most weather because the wavelength is larger than the particle size for dust, drizzle rain, fog. Further the mm wave beam passes through an atmospheric transmission window that provides a dip in attenuation. The higher frequency than conventional radar provides higher Doppler frequencies, for example, than X-band radar. We show by simulation that small characteristic vibrations and slow turns of an aircraft become visible so that the Doppler signature improves identification. The higher frequency also reduces beam width, which increases transmit and receive antenna gains. For the same power the transmit beam extends to farther range and the increase in receive antenna gain increases signal to noise ratio for improved detection and identification. The narrower beam can also reduce clutter and reject other noise more readily. We show by simulation that the radar can be used at lower elevations over the sea than conventional radar.

McAulay, Alastair D.

2011-05-01

416

Radar Detection of Copernicus Secondary Craters  

NASA Astrophysics Data System (ADS)

Copernicus Crater (D ~ 95 km) is one of the largest young primary craters on the lunar surface. We present radar mosaics of the Copernicus region that reveal numerous small secondary craters with ejecta blankets of blocky material extending in “tails” downrange from the parent crater. Individual secondary craters are more apparent in the radar circular polarization ratio images than in Clementine 750 nm images of similar resolution. A capability to distinguish between primary and secondary craters at large distances from the parent crater will improve the reliability of the age dating of small areas on the Moon and, possibly, other solar system bodies. Wells et al. (2010) investigated a group of otherwise unremarkable craters near the lunar south pole with parallel, asymmetric ejecta blankets visible in radar CPR but not optical images. The radar CPR is sensitive to blockiness on the radar wavelength, with low CPR indicative of smooth surfaces and high CPR of rough surfaces. The rough ejecta blankets seen by Wells et al (2010) were elongated downrange from Tycho crater, and the group of small craters was deemed to be a population of Tycho secondaries. Similar ejecta blankets are associated with numerous small craters in the Copernicus radar mosaics. These 12.8-cm radar images were obtained with the Arecibo and Green Bank telescopes operating in a radar bi-static mode as part of a project to map the lunar near-side at 80 m/pix (Campbell et al., 2010). Regions of high CPR are overlain on a contrast-enhanced depolarized radar image to aid in the identification of craters with associated CPR features. Using the presence of these high-CPR ejecta blankets as an indicator, the size and location of secondary craters present in the 160 m/pix mosaic are being measured. Several thousand potential secondary craters have been marked for investigation. To date, 157 secondary craters with D>3 km have been cataloged in a 1.47 million square km area surrounding Copernicus crater. 202 secondary craters with D>2.3 km in a 256 thousand square km region to the north of Copernicus have also been investigated. The size frequency distributions of these populations have steep power-law slopes of b= -6.7 and b= -5.2, respectively. These values are steeper than the canonical secondary power-law slope of b= -3 or b= -4. Ongoing debate over the reliability of ages derived from counts of craters with small diameters depends heavily on the relative dominance of small primary and secondary craters on the Moon. Continued investigation of large populations of secondary craters, like those of Copernicus and Tycho, will help to resolve this issue. Future work will focus on greater spatial coverage at higher resolution for Tycho, Copernicus, and other bright-rayed near-side craters such as Kepler, Aristarchus, and Aristillus. References: Campbell et al (2010), Icarus 208, 2, p 565-573. Wells et al (2010), JGR 115, doi:10.1029/2009JE003491

Wells, K. S.; Campbell, D. B.; Campbell, B. A.; Carter, L. M.; Anderson, R.

2010-12-01

417

Smart skin spiral antenna with chiral absorber  

Microsoft Academic Search

Recently there has been considerable interest toward designing 'smart skins' for aircraft. The smart skin is a composite layer which may contain conformal radars, conformal microstrip antennas or spiral antennas for electromagnetic applications. These embedded antennas will give rise to very low radar cross section (RCS) or can be completely 'hidden' to tracking radar. In addition, they can be used

Vijay K. Varadan; Vasundara V. Varadan

1995-01-01

418

Propagation effects in tactical radars  

NASA Astrophysics Data System (ADS)

Tactical battlefield radars are employed in surveillance and target acquisition roles at ranges of approximately 1 to 20 km, their main targets being enemy ground vehicles and personnel. As with all types of radar the operating environment has a significant effect on the design and performance of these systems and propagation considerations are an important factor. The major propagation factors which limit the performance of tactical radars are the availability of line of sight, ground clutter, and effects of the weather. The ways in which propagation factors affect the choice of such radar parameters as frequency, polarisation, and RF waveform are discussed, and the ways in which propagation constraints can be minimised by the design of the signal processing system are considered. In an EW environment an important operational requirement is to minimize the probability of the location of the position of the radar by the enemy. Propagation effects such as multipath and diffraction are considered in broad terms in this context.

Prew, B. A.

1982-04-01

419

Radar SLAM using visual features  

NASA Astrophysics Data System (ADS)

A vessel navigating in a critical environment such as an archipelago requires very accurate movement estimates. Intentional or unintentional jamming makes GPS unreliable as the only source of information and an additional independent supporting navigation system should be used. In this paper, we suggest estimating the vessel movements using a sequence of radar images from the preexisting body-fixed radar. Island landmarks in the radar scans are tracked between multiple scans using visual features. This provides information not only about the position of the vessel but also of its course and velocity. We present here a navigation framework that requires no additional hardware than the already existing naval radar sensor. Experiments show that visual radar features can be used to accurately estimate the vessel trajectory over an extensive data set.

Callmer, Jonas; Törnqvist, David; Gustafsson, Fredrik; Svensson, Henrik; Carlbom, Pelle

2011-12-01

420

Interferometric radar measurements  

NASA Astrophysics Data System (ADS)

The United States Army Space and Missile Defense Command (USASMDC) has interest in a technology demonstration that capitalizes on investment in fire control and smart interceptor technologies that have matured beyond basic research. The concept SWORD (Short range missile defense With Optimized Radar Distribution) consists of a novel approach utilizing a missile interceptor and interferometric fire control radar. A hit-to-kill, closed-loop, command guidance scheme is planned that takes advantage of extremely accurate target and interceptor state vectors derived via the fire control radar. The fire control system has the capability to detect, track, and classify multiple threats in a tactical regime as well as simultaneously provide command guidance updates to multiple missile interceptors. The missile interceptor offers a cost reduction potential as well as an enhancement to the kinematics range and lethality over existing SHORAD systems. Additionally, the Radio Frequency (RF) guidance scheme offers increased battlefield weather performance. The Air Defense (AD) community, responding to current threat capabilities and trends, has identified an urgent need to have a capability to counter proliferated, low cost threats with a low cost-per-kill weapon system. The SWORD system will offer a solution that meets this need. The SWORD critical technologies will be identified including a detailed description of each. Validated test results and basic principles of operation will be presented to prove the merit of past investments. The Deputy Assistant Secretary of the Army for Research and Technology (DAS(R&T) has a three- year Science and Technology Program to evaluate the errors and proposed mitigation techniques associated with target spectral dispersion and range gate straddle. Preliminary bench-top experiment results will be presented in this paper.

Smith, Ronald A.; Shipman, Mark; Holder, E. J.; Williams, James K.

2002-08-01

421

Gravity wave propagation studies using the Indian MST radar observations  

NASA Astrophysics Data System (ADS)

The Indian MST radar facility at Gadanki (13.5°N, 79.2°E) has been utilised to study the propagation of gravity waves from the troposphere/lower stratosphere to the mesosphere and their interaction with the radar backscattered signal variations. The main objective is to correlate vertically propagating gravity waves derived from the tropospheric velocity fields with the dynamics of mesospheric scattering centres. The tropospheric wind velocities and signal strengths over the entire height range have been subjected to power spectral and wavelet analysis to determine the predominant wave periods/amplitudes and the coupling between the lower atmosphere and mesosphere. Results show that (a) the gravity waves are clearly detectable near tropopause heights, (b) while relatively higher period gravity waves (20-50 min) interact with mesospheric scattering centres, the lower period waves (<20 min) are absorbed in the troposphere itself, (c) the mesospheric scattering layers are affected by gravity waves of complementary periods.

Chakravarty, S. C.

2012-02-01

422

Satellite radar altimeters  

NASA Astrophysics Data System (ADS)

The basic operating principles of satellite radar altimeters are reviwed, with a focus on factors affecting their use in remote sensing of the ocean surface. Topics discussed include range resolution requirements, the selection of the operating frequency (considering atmospheric absorption, technology, antenna size, ionospheric refraction, and conflicts with other onboard systems), beam-limited vs pulse-limited operation, transmitted-power requirements, and pulse compression. Particular attention is given to the pulse-limited footprint and the shape of the echo waveform, parameter extraction, and height corrections for spacecraft center-of-gravity location, instrument errors, propagation factors, surface bias, tides and atmospheric effects, and geoid variations. Diagrams and graphs are provided.

Rapley, Chris G.

423

Radar resource management for mechanically rotated, electronically scanned phased array radars  

Microsoft Academic Search

A key feature (in ballistic missile defence and intelligence gathering radars) is the formulation of the turret control policy and its feedback relationship to radar activity planning. The radar resource management process is discussed. The results of the radar planning algorithm, referred to as the radar plan, are provided to the turret policy control algorithm to formulate the sequence of

S. T. Cummings; K. Behar

1991-01-01

424

Shock Absorbers - Are They Necessary?  

Microsoft Academic Search

The economic benefits of running a shock absorber seem evident from their growing use in oil and gas drilling operations. However, some controversy still exists over when they should be used, how to get the greatest benefit from them, and whether there are some negative effects such as hole deviation associated with the usage of some shock absorbers. Extensive experience

S. W. Worford; P. G. Craig

1983-01-01

425

Shuttle rendezvous radar performance: evaluation and simulation  

Microsoft Academic Search

The authors describe the performance evaluation and simulation of the Ku-band shuttle rendezvous radar. Computer simulation, using the radar cross section for specific spacecraft, provided an estimate of rendezvous radar range performance for that spacecraft. The radar cross section model included smooth metallic surfaces, rough surfaces, and shadowing effects, as well as phase differences due to different path lengths to

J. W. Griffin; A. C. Lindberg; T. B. Ahn; P. L. Harton

1989-01-01

426

Passive VHF radar for ionospheric physics  

Microsoft Academic Search

Recent technological advances enable a new class of passive radar instruments. These radars have no dedicated transmitter, observing serendipitous scatter of existing sources. Such radars may have very high performance and cost far less than conventional radars. The resulting equipment is essentially reduced to simple antennas, desktop computers, and Global Positioning System equipment. The safety hazards, interference problems, licensing issues,

J. D. Sahr; D. M. Gidner; Chucai Zhou; F. D. Lind

2001-01-01

427

Advanced ground-based ESCAN radars  

Microsoft Academic Search

Electronically scanned radars (ESCAN radars) are key system elements of ground based military systems being developed for air and missile defense against future threats including tactical ballistic missiles, high agile and low RCS targets like drones, ARMs, UAVs. The radar design is governed on the one hand by challenging requirements on ESCAN radar performance and on the other hand by

U. Fuchs; W. Sieprath

2005-01-01

428

Cognitive radar: a way of the future  

Microsoft Academic Search

This article discusses a new idea called cognitive radar. Three ingredients are basic to the constitution of cognitive radar: 1) intelligent signal processing, which builds on learning through interactions of the radar with the surrounding environment; 2) feedback from the receiver to the transmitter, which is a facilitator of intelligence; and 3) preservation of the information content of radar returns,

Simon Haykin

2006-01-01

429

Radar sensor for vehicle cruise control applications  

Microsoft Academic Search

This paper deals with research efforts relating to radar sensors using millimeter wave technology, in particular to autonomous radars which are used for forward looking and to detect the distance and relative velocity of car ahead. The fundamental requirements to on-board radar equipment are formulated. Some experimental results of this radar research are presented.

S. B. Maltsev; V. I. Rudik; V. P. Rukin

2001-01-01

430

Soviet oceanographic synthetic aperture radar (SAR) research  

Microsoft Academic Search

Radar non-acoustic anti-submarine warfare (NAASW) became the subject of considerable scientific investigation and controversy in the West subsequent to the discovery by the Seasat satellite in 1978 that manifestations of underwater topography, thought to be hidden from the radar, were visible in synthetic aperture radar (SAR) images of the ocean. In addition, the Seasat radar produced images of ship wakes

D. N. Held; R. F. Gasparovic; A. W. Mansfield; W. K. Melville; E. L. Mollo-Christensen; H. A. Zebker

1991-01-01

431

SMAP Radar Processing and Expected Performance  

NASA Astrophysics Data System (ADS)

This presentation will describe the processing algorithms being developed for the Soil Moisture Active Passive (SMAP) radar data and the expected characteristics of the measured backscattering cross sections. The SMAP radar combines some unique features such as a conically scanned antenna with SAR processing of the data. The rapidly varying squint angle gives the measurements variable resolution and noise characteristics and poses a challenge to the processor to maintain accuracy around the wide (1000 km) swath. Rapid variation of Doppler around the scan leads to a time domain azimuth correlation algorithm, and variation of the Doppler geometry will likely require varying the processing bandwidth to manage ambiguity contamination errors. The basic accuracy requirement is 1-dB (one-sigma) in the backscatter measurements at a resolution of 3 km. The main error contributions come from speckle noise, calibration uncertainty, and radio frequency interference (RFI). Speckle noise is determined by system design parameters and details of the processing algorithms. The calibration of the backscatter measurements will be based on pre-launch characterization of the radar components which allow corrections for short term (~1 month) variations in performance. Longer term variations and biases will be removed using measurements of stable reference targets such as parts of the Amazon rain forest, and possibly the oceans and ice sheets. RFI survey measurements will be included to measure the extent of RFI around the world. The SMAP radar is designed to be able to hop the operating frequency within the 80 MHz allocated band to avoid the worst RFI emitters. Data processing will detect and discard further RFI contaminated measurements. This work is supported by the SMAP project at JPL - CalTech. The SMAP mission has not been formally approved by NASA. The decision to proceed with the mission will not occur until the completion of the National Environmental Policy Act (NEPA) process. Material in this document related to SMAP is for information purposes only.

West, R. D.; Jaruwatanadilok, S.

2011-12-01

432

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

433

Device for absorbing mechanical shock  

SciTech Connect

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, C.E.

1980-12-30

434

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, C.E.

1979-08-29

435

Shock absorbers - Are they necessary  

SciTech Connect

The economic benefits of running a shock absorber seem evident from their growing use in oil and gas drilling operations. However, some controversy still exists over when they should be used, how to get the greatest benefit from them, and whether there are some negative effects such as hole deviation associated with the usage of some shock absorbers. Extensive experience in recent years has included results with a wide variety of shock absorber designs in the full range of hole depths and sizes. The results show that lateral stiffness of the tool, the type of spring or other energy absorption system, and tool length have a significant influence on shock absorber performance. The energy absorption system and its location in the drill string, in conjunction with the type of bottom hole assembly design, bit selection, and formation characteristics, determine whether the maximum benefits possible from the shock absorber are attained. Major benefits from proper use of the appropriate shock absorber are longer bit life, higher drilling rates, longer drill-string life, reduced hazard from bending fatigue of the threaded connections in the drill string, and reduced wear on the rig equipment. These all result in a significant reduction of the overall drilling costs. Guidelines for shock absorber selection, placement in the drill string, and operating practices which yield the greatest overall benefit from the use of a shock absorber in oil field drilling are described. Ultimately, the decision to use a shock absorber will be based on economics. Does the use of a shock absorber reduce the overall drilling cost.

Worford, S.W.; Craig, P.G.

1983-02-01

436

Polarization radar processing technology  

NASA Astrophysics Data System (ADS)

A comprehensive effort is presented involving measurements and performance evaluation for the detection of scatters immersed in a background of natural and man-made clutter using polarization diverse waveforms. The effort spans evaluation from the initial stages of theoretical formulation to processor performance evaluation using real world data. The theoretical approach consists of determining polarimetric statistical properties of the backscatter waveform and the use of these properties to derive the optimum dual polarized S-Band radar system with selectable polarization on both transmit and receive. Recording equipment consists of 12 bit digital in-phase and quadrature channels indexed in time and phase for both polarizations. Several processors utilizing optimum and sub-optimum algorithms were evaluated using simulated and live radar data, and performance results were compared. The processor types include fully adaptive algorithms designed to operate on polarimetric spectral spread waveforms, and several combinations of single channel and polarization diverse receivers with both single and dual transmit polarization. A conventional fixed transmit and receive mode with no spectral processing is included. Comparisons are made between the various processors. The simulated and real data consist of randomly scattered dipoles, spheres, Swerling type scatters, and scatters of opportunity.

Stiefvater, Kenneth C.; Brown, Russell D.; Vannicola, Vincent C.; Wicks, Michael C.

1989-10-01

437

Radar resource sharing study  

NASA Astrophysics Data System (ADS)

The Radar Resource Sharing Study was undertaken to evaluate the relative advantages or three candidate technologies for implementing a shared beamformer for a dual band (S and UHF) airborne surveillance radar. The beamformer was required to interface with the two active array apertures and perform the signal combining and distribution functions necessary to produce the receive and transmit beams required for each band. The objective was to compare the three approaches in terms of size, weight, power consumption and hardware sharing, based on 1997 technology projections. The candidate beam-former technologies investigated were Conventional, Digital and Optical beamformers. In the digital and optical cases, technology limitations precluded accomplishing all of the required beamformer functions. Therefore, hybrid approaches which employed each of these technologies to the maximum practical extent were devised. The study commenced in September 1992 and was conducted primarily on the basis of beamformer requirements for monostatic operation. Later the scope was expanded to consider a bistatic receive implementation having significantly different beam requirements.

Gouse, Ronald; Clancy, John

1995-03-01

438

Experimental results on indoor electromagnetic wave absorber using magnetic wood  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to propose a new type of indoor electromagnetic wave absorber using magnetic wood. This magnetic wood has good electromagnetic wave absorbing characteristics, a low specific gravity, a wood texture and other wood characteristics and can be easily processed. Electromagnetic wave absorbing characteristics were measured for four types of magnetic wood. The sandwich-type magnetic wood demonstrated the best wave absorbing characteristics among the four types of magnetic wood that were studied. The experimental results showed that the proposed indoor electromagnetic wave absorber can be used to suppress the transmission and reception of cellular phone and Personal Handy Phone System (PHS) signals and can be used as a cross protection for indoor wireless Local Area Networks (LAN). This wood can be processed for use in furniture, building materials, and other applications.

Oka, Hideo; Narita, Koichi; Osada, Hiroshi; Seki, Kyoushirou

2002-05-01

439

Perspectives on Worldwide Spaceborne Radar Programs  

Microsoft Academic Search

Radar technology and techniques were originally developed for land-based, maritime, and airborne applications. Spaceborne radar systems development began in the 1960s in the USSR for military purposes, and in the 1970s in the United States for civilian scientific purposes. NASA launched the SeaSAT satellite in 1978, carrying a synthetic aperture radar, a radar altimeter, a radar scatterometer, and a radiometer,

P. A. Rosen; G. M. Buccolo

2007-01-01

440

Next Generation Weather Radar (NEXRAD)/Air Route Surveillance Radar (ARSR) Operational Comparison.  

National Technical Information Service (NTIS)

The National Weather Service (NWS), Federal Aviation Administration (FAA), and Department of Defense are in the process of fielding the Next Generation Weather Radars (NEXRAD). These doppler weather radars, also known as Weather Surveillance Radar (WSR)88...

B. Dunbar J. Mittelman

1993-01-01

441

Next Generation Weather Radar (NEXRAD)/Air Route Surveillance Radar (ARSR) Operational Comparison.  

National Technical Information Service (NTIS)

The National Weather Service (NWS), Federal Aviation Administration (FAA), and Department of Defense are in the process of fielding the Next Generation Weather Radars (NEXRAD). These doppler weather radars, also known as Weather Surveillance Radar (WSR)-8...

B. Dunbar J. Mittelman

1993-01-01

442

A lambda\\/4 Wave Absorber for Both 60 and 76 GHz Bands  

Microsoft Academic Search

While the demand of millimeter-wave intelligent transport system(ITS) including the automotive radar increases, utilization of electromagnetic(EM) waves on the street is increasing now. However, malfunction may be caused to communication and detection by the diffused EM wave reflected from incidental facilities such as a road sign and others. If the road sign having an absorbing function of the unwanted EM

Asuka Kondo; Makoto Toyota; Tetsu Soh; Osamu Hashimoto

2004-01-01

443

The Clementine bistatic radar experiment.  

PubMed

During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, beta, for selected lunar areas. Observations of the lunar south pole yield a same-sense polarization enhancement around beta = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar observations of periodically solar-illuminated lunar surfaces, including the north pole, yielded no such enhancement. A probable explanation for these differences is the presence of low-loss volume scatterers, such as water ice, in the permanently shadowed region at the south pole. PMID:8929403

Nozette, S; Lichtenberg, C L; Spudis, P; Bonner, R; Ort, W; Malaret, E; Robinson, M; Shoemaker, E M

1996-11-29

444

Radar polarimetry for geoscience applications  

SciTech Connect

A source book for remote sensing and radar design engineers, this text covers wave polarization, polarization synthesis, scattering matrices, SAR polarization systems, and an array of applications It covers: an introduction to the different mathematical representations used to describe scattering properties, a review of scatterometer system design and calibration techniques for use in polarimetric measurements, a study of specific polarimetric radar systems, such as the shuttle imaging radar C (SIR-C), that includes calibration and compression techniques, data processing guidelines, and design approaches.

Elachi, C.; Kuga, Y.; McDonald, K.; Sarabandi, K.; Ulaby, F.T.; Whitt, M.; Zebker, H.; van Zyl, J.J.

1990-01-01

445

Transmitter and Receiver Antenna Gain Analysis for Laser Radar and Communication Systems.  

National Technical Information Service (NTIS)

A comprehensive and fairly self-contained study of centrally obscured optical transmitting and receiving antennas is presented and is intended for use by the laser radar and communication systems designer. The material is presented in a format which allow...

B. J. Klein J. J. Degnan

1973-01-01

446

Method for designing an absorbent article  

US Patent & Trademark Office Database

A method for designing an absorbent article. The steps of the method are generating a physical spatial map of saturation of a fluid within an absorbent in a physical test environment, generating a virtual spatial map of saturation of a fluid within an absorbent in a virtual test environment, identifying absorbent-fluid interaction properties for the absorbent such that the virtual spatial map of saturation approximates the physical spatial map of saturation, inputting the absorbent-fluid interaction properties into a virtual model of the absorbent article to produce a representation of at least one feature of the absorbent article, evaluating the virtual model of the absorbent article to determine the performance of the at least one feature of the absorbent article, modifying the design of the absorbent article in response to the performance of the at least one feature of the absorbent article determined from the virtual model of the absorbent article.

Allende-Blanco; Mel (Loveland, OH); Anderson; Brian Bert (Liberty Township, OH); Hartt, IV; William Handy (Mason, OH); Lipic; Paul Martin (West Chester, OH); Schmidt; Mattias (Idstein, DE); Stevens; Douglas Gregory (Blue Ash, OH); Ehrnsperger; Bruno Johannes (Evendale, OH)

2010-03-23

447

Principles of quantitative absorbance measurements in anisotropic crystals  

NASA Astrophysics Data System (ADS)

The accurate measurement of absorbance ( A=-log T; T=I/I 0) in anisotropic materials like crystals is highly important for the determination of the concentration and orientation of the oscillator (absorber) under investigation. The absorbance in isotropic material is linearly dependent on the concentration of the absorber and on the thickness of the sample ( A=?·c·t). Measurement of absorbance in anisotropic media is more complicated, but it can be obtained from polarized spectra (i) on three random, but orthogonal sections of a crystal, or (ii) preferably on two orthogonal sections oriented parallel to each of two axes of the indicatrix ellipsoid. To compare among different crystal classes (including cubic symmetry) it is useful to convert measured absorbance values to one common basis (the total absorbance A tot), wherein all absorbers are corrected as if they were aligned parallel to the E-vector of the incident light. The total absorption coefficient ( a tot= A tot/ t) is calculated by 269_2004_Article_BF00199497_TeX2GIFE1.gif left( {text{i}} right)a_{{text{tot}}} = sumlimits_{i = 1}^3 {(a_{max ,i} + a_{min ,i} )} /2, {text{or}} {text{by}} {text{(ii) }}a_{{text{tot}}} = a_x + a_y + a_z . Only in special circumstances will unpolarized measurements of absorbance provide data useful for quantitative studies of anisotropic material. The orientation of the absorber with respect to the axes of the indicatrix ellipsoid is calculated according to A x/ A tot=cos2 ( x < absorber), and analogously for A yand A z. In this way, correct angles are obtained for all cases of symmetry. The extinction ratio of the polarizer ( Pe=I crossed/ I parallel) has considerable influence on the measured amplitude of absorption bands, especially in cases of strong anisotropic absorbance. However, if Pe is known, the true absorbance values can be calculated even with polarizers of low extinction ratio, according to A max=-log[( T max,obs-0.5· Pe· T min,obs)/(1-0.5· Pe)], and similar for A min. The theoretical approach is confirmed by measurements on calcite and topaz.

Libowitzky, Eugen; Rossman, George R.

1996-08-01

448

Miniature laser direct-detection radar  

NASA Astrophysics Data System (ADS)

A miniature laser with a total volume less than 15 cu cm and weight less than 100 g has been designed, fabricated, and assembled. The laser uses a composite rod consisting of Nd:Cr:GSGG material rod cladded with an Er:Cr:YSGG tube. The laser provides output at 1 and 3 micron wavelengths. The size and weight reduction is obtained by chemical pumping which eliminates the prime power and the power supply. The laser is used as an illuminator in a direct detection radar.

Acharekar, Madhu; Lebeau, Robert

1992-06-01

449

Microwave absorbing properties of ferrite-based nanocomposites  

NASA Astrophysics Data System (ADS)

A study of the microwave absorbing properties of polymer (epoxy) based nanocomposites is presented. The ferrite nanoparticles employed as filler materials were produced by a co-precipitation method, which was designed for production of large amounts at low cost. The absorbing properties of different kinds of ferrite nanoparticles, soft (manganese) and hard (cobalt) magnetic nanoparticles, are compared. In addition, the impact of high and low densities of the respective ferrite type has been investigated. Our analysis of the microwave absorbing properties is made over a wide frequency band including both MHz and GHz regions, which is of high interest for a number of different applications both military and civilian.

Jänis, A.; Olsson, R. T.; Savage, S. J.; Gedde, U. W.; Klement, U.

2007-04-01

450

Radar investigation of asteroids  

NASA Astrophysics Data System (ADS)

Radar investigations were conducted of selected minor planets, including: (1) observations during 1981-82 of 10 potential targets (2 Pallas, 8 Flora, 12 Victoria, 15 Eunomia, 19 Fortuna, 22 Kalliope, 132 Aethra, 219 Thusnelda, 433 Eros, and 2100 Ra-Shalom); and (2) continued analyses of observational data obtained during 1980-81 for 10 other asteroids (4 Vesta, 7 Iris, 16 Psyche, 75 Eurydike, 97 Klotho, 216 Kleopatra, 1685 Toro, 1862 Apollo, 1865 Cerberus, and 1915 Quetzalcoatl). Scientific objectives include estimation of echo strength, polarization, spectral shape, spectral bandwidth, and Doppler shift. These measurements: (1) yield estimates of target size, shape, and spin vector; (2) place constraints on topography, morphology, and composition of the planetary surface; (3) yield refined estimates of target orbital parameters; (4) reveal the presence of asteroidal satellites.

Ostro, S. J.

1981-07-01

451

Acoustical model of a Shoddy fibre absorber  

NASA Astrophysics Data System (ADS)

Shoddy fibres or "Shoddies" are a mixture of post-consumer and post-industrial fibres diverted from textile waste streams and recycled into their raw fibre form. They have found widespread use as a raw material for manufacturing sound absorbers that include, but are not limited to: automotive, architectural and home appliance applications. The purpose of this project is to develop a simple acoustic model to describe the acoustic behaviour of sound absorbers composed primarily of Shoddy fibres. The model requires knowledge of the material's bulk density only. To date, these materials have not been the focus of much published research and acoustical designers must rely on models that were developed for other materials or are overly complex. For modelling purposes, an equivalent fluid approach is chosen to balance complexity and accuracy. In deriving the proposed model, several popular equivalent fluid models are selected and the required input parameters for each model identified. The models are: the model of Delaney and Bazley, two models by Miki, the model of Johnson in conjunction with the model of Champoux and Allard and the model of Johnson in conjunction with the model of Lafarge. Characterization testing is carried out on sets of Shoddy absorbers produced using three different manufacturing methods. The measured properties are open porosity, tortuosity, airflow resistivity, the viscous and thermal characteristic lengths and the static thermal permeability. Empirical relationships between model parameters and bulk density are then derived and used to populate the selected models. This yields several 'simplified' models with bulk density as the only parameter. The most accurate model is then selected by comparing each model's prediction to the results of normal incidence sound absorption tests. The model of Johnson-Lafarge populated with the empirical relations is the most accurate model over the range of frequencies considered (approx. 300 Hz - 4000 Hz) Characterization testing yields specific values for intrinsic material parameters that allow for comparison to other porous materials. Individual parameter relations allow users to substitute measured or theoretical values as needed. A new empirical acoustical model is proposed to describe the behaviour of Shoddy-based fibre absorbers. The model requires knowledge of the bulk density only. This parameter is easily measured making application of the model elementary. Mots-clés : Shoddy, porous, fibre, recycled, absorption, model, acoustic.

Manning, John Peter

452

Ultrathin multiband gigahertz metamaterial absorbers  

NASA Astrophysics Data System (ADS)

We propose ultrathin multiband metamaterial absorbers in the microwave frequencies in which the design, analysis, fabrication, and measurement of the absorbers working in multiple bands are presented. The metamaterial absorbers consist of a periodic arrangement of different scales of electric-field-coupled-LC (ELC) resonators and a metallic background plane, separated by only 1 mm dielectric spacer. By tuning the scale factor of the ELC unit cells, we achieve independently multiple absorptions at different customized frequencies. Experiments demonstrate excellent absorption rates in the designed frequency bands over wide angles of incident waves for both transverse electric and magnetic polarizations. The explanation to the physical mechanism of the multiband metamaterial absorber is presented and verified.

Li, Hui; Yuan, Li Hua; Zhou, Bin; Shen, Xiao Peng; Cheng, Qiang; Cui, Tie Jun

2011-07-01

453

Radar images of Mars.  

PubMed

Full disk images of Mars have been obtained with the use of the Very Large Array (VLA) to map the radar reflected flux density. The transmitter system was the 70-m antenna of the Deep Space Network at Goldstone, California. The surface of Mars was illuminated with continuous wave radiation at a wavelength of 3,5 cm. The reflected energy was mapped in individual 12-minute snapshots with the VLA in its largest configuration; fringe spacings as small as 67 km were obtained. The images reveal near-surface features including a region in the Tharsis volcano area, over 2000 km in east-west extent, that displayed no echo to the very low level of the radar system noise. The feature, called Stealth, is interpreted as a deposit of dust or ash with a density less than about 0.5 gram per cubic centimeter and free of rocks larger than 1 cm across. The deposit must be several meters thick and may be much deeper. The strongest reflecting geological feature was the south polar ice cap, which was reduced in size to the residual south polar ice cap at the season of observation. The cap image is interpreted as arising from nearly pure CO(2) or H(2)O ice with a small amount of martian dust (less than 2 percent by volume) and a depth greater than 2 to 5 m. Only one anomalous reflecting feature was identified outside of the Tharsis region, although the Elysium region was poorly sampled in this experiment and the north pole was not visible from Earth. PMID:17784090

Muhleman, D O; Butler, B J; Grossman, A W; Slade, M A

1991-09-27

454

NASA Radar Images Asteroid Toutatis  

NASA Video Gallery

This 64-frame movie of asteroid Toutatis was generated from data by Goldstone's Solar System Radar on Dec. 12 and 13, 2012. In the movie clips, the rotation of the asteroid appears faster than it occurs in nature.

Anthony Greicius

2012-12-13

455

Mode S Baseline Radar Tracking.  

National Technical Information Service (NTIS)

Tests and evaluation were conducted to determine the baseline performance characteristics of the Moving Target Detector (MTD) and Radar Data Acquisition System (RDAS) as an integral part of the Mode S sensor. The MTD and RDAS were separately evaluated to ...

E. F. Mancus L. H. Baker

1982-01-01

456

Survey of Radar Signal Processing.  

National Technical Information Service (NTIS)

During the last decade, considerable progress has been made in radar signal processing, and this report states its present status. The three broad areas of coherent processing, noncoherent detection, and track-while-scan systems are discussed. Specificall...

G. V. Trunk

1977-01-01

457

A novel composite sound absorber with recycled rubber particles  

NASA Astrophysics Data System (ADS)

A new kind of composite sound absorber has been fabricated, using recycled rubber particles with good attenuation property as sound energy attenuation layer, low characteristic impedance materials such as polymer porous foam or perforated panel as matching layer. Its’ attractive characteristics include: low-cost, broad-band sound absorption, thin in thickness and relatively simple processing. An acoustic transmission analytical model is developed and successfully applied to evaluate the sound absorption of the composite absorber.

Hong, Zhou; Bo, Li; Guangsu, Huang; Jia, He

2007-07-01

458

Countercurrent flow absorber and desorber  

DOEpatents

Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system. 9 figs.

Wilkinson, W.H.

1984-10-16

459

Countercurrent flow absorber and desorber  

DOEpatents

Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system.

Wilkinson, William H. (Columbus, OH)

1984-01-01

460

Solar Radar Astronomy with LOFAR  

NASA Astrophysics Data System (ADS)

A new approach to the study of the Sun's corona and its dynamical processes is possible with radar investigations in the frequency range of about 10-50 MHz. The range of electron densities of the solar corona is such that radio waves at these frequencies can provide diagnostic radar echoes of large scale phenomena such as coronal mass ejections (CMEs). We expect that the frequency shift imposed on the echo signal by an earthward-moving CME will provide a direct measurement of the velocity, thereby providing a good estimate of the arrival time at Earth. It is known that CMEs are responsible for the largest geomagnetic storms at Earth, which are capable of causing power grid blackouts, satellite electronic upsets, and degradation of radio communications circuits. Thus, having accurate forecasts of potential CME-initiated geomagnetic storms is of practical space weather interest. New high power transmitting arrays are becoming available, along with proposed modifications to existing research facilities, that will allow the use of radio waves to study the solar corona by the radar echo technique. Of particular interest for such solar radar investigations is the bistatic configuration with the Low Frequency Array (LOFAR). The LOFAR facility will have an effective receiving area of about 1 square km at solar radar frequencies. Such large effective area will provide the receiving antenna gain needed for detailed investigations of solar coronal dynamics. Conservative estimates of the signal-to-noise ratio for solar radar echoes as a function of the integration time required to achieve a specified detection level (e.g., ~ 5 dB) indicate that time resolutions of 10s of seconds can be achieved. Thus, we are able to resolve variations in the solar radar cross section on time scales which will provide new information on the plasma dynamical processes associated with the solar corona, such as CMEs. It is the combination of high transmitted power and large effective receiving area that makes possible the significant performance indicated. We will review early and current solar radar investigations and proposed approaches to future radar studies of the solar corona. Solar radar experiments were done almost from the beginning of the modern era of space physics research and has a very interesting history. In addition to re-opening the solar radar window, LOFAR will also be able to open new studies of planetary hard surfaces (e.g., the Moon and asteroids), and solar system plasmas (solar wind, magnetosphere, dusty plasmas, comets).

Rodriguez, P.

2003-04-01

461

Laser radar observation of the polar stratospheric aerosol layer  

NASA Astrophysics Data System (ADS)

The polar stratosphere has been speculated to be an active sink region of various stratospheric materials; ozone, water vapor, NOX, aerosol particles and so on, but this process is not theoretically and/or observationally made clear. The observation of the polar stratospheric aerosol layer using laser radar certainly contributes to the study of the global transport of these stratospheric minor constituents. In addition to this, from the viewpoint of aerosol science, there may be many interesting phenomena which cannot be found in the stratosphere at mid and low latitudes; the effect of precipitation of high energy molecules and atoms, of very cold winter stratosphere, of very cold mesopause in summer. Laser radar observation is one of the main activities of the Antarctic Middle Atmosphere (AMA) project at Syowa Station (69.00 deg S, 39.35 deg E), Antarctica since May 1983. Laser radar measurement at Syowa Station is discussed in detail.

Iwasaka, Y.; Hirasawa, T.; Fukunishi, H.; Fujiwara, M.; Fujii, R.; Miyaoka, H.

1985-12-01

462

Synchronisation of bistatic radar systems  

Microsoft Academic Search

Bistatic radar is gaining more and more interest over the last years. It offers more freedom to deploy the transmitter and the receiver, e.g. in a way to enhance the signature of stealthy targets. Furthermore, the bi- or multistatic system can be realized without using expensive transmit\\/receive-modules. An additional feature of bistatic radar is that continuous wave signals can be

M. Weib

2004-01-01

463

Rendezvous radar for orbital vehicles  

NASA Astrophysics Data System (ADS)

In this paper some of the factors which relate to the system design of rendezvous radars are discussed and the system design and the capabilities of the OMV Rendezvous Radar System (RRS) are described. The potential for transferring manufacturing technologies and methods which have been developed for high-volume-production commercial and military hardware systems into the relatively low volume world of hi-rel electronics hardware for space is discussed.

Locke, John W.; Casey, Larry D.

1992-03-01

464

A radar image time series  

Microsoft Academic Search

A set of side-looking radar images has been collected over an area in the Sierrita Pediment, Arizona, U.S.A. The dates of image acquisition vary from 1965-1979 and the images are taken at various look angles, frequencies, flight directions and polarizations. The objective of the study is to demonstrate the photogrammetric orthophoto technique applied to radar images and at the same

F. Leberl; H. Fuchs; J. P. Ford

1981-01-01

465

LPI considerations for surveillance radars  

NASA Astrophysics Data System (ADS)

A low probability-of-intercept (LPI) radar is designed for covert operations which uses minimum radiated power and measures target characteristics with a waveform modulation that is difficult for an intercept receiver to identify. It is established that while doubling the number of an LPI radar's receivers improves the LPI factor by 3 dB, it increases cost by a factor of 2. Reducing video bandwidth reestablishes moderate cost without a major degradation of overall performance or increase in antenna size.

Ruffe, L. I.; Stott, G. F.

466

Radar imaging of Saturn's rings  

Microsoft Academic Search

We present delay–Doppler images of Saturn's rings based on radar observations made at Arecibo Observatory between 1999 and 2003, at a wavelength of 12.6 cm and at ring opening angles of 20.1°?|B|?26.7°. The average radar cross-section of the A ring is ?77% relative to that of the B ring, while a stringent upper limit of 3% is placed on the

Philip D. Nicholson; Richard G. French; Donald B. Campbell; Jean-Luc Margot; Michael C. Nolan; Gregory J. Black; Heikki J. Salo

2005-01-01

467

Representing radar QPE and QPF uncertainties using radar ensembles  

NASA Astrophysics Data System (ADS)

In the last years, new comprehension of the physics underlying the radar measurements as well as new technological advancements have allowed radar community to propose better algorithms and methodologies and significant advancements have been achieved in improving Quantitative Precipitation Estimates (QPE) and Quantitative Precipitation forecasting (QPF) by radar. Thus the study of the 2D uncertainties field associated to these estimates has become an important subject, specially to enhance the use of radar QPE and QPF in hydrological studies, as well as in providing a reference for satellite precipitations measurements. In this context the use of radar-based rainfall ensembles (i.e. equiprobable rainfall field scenarios generated to be compatible with the observations/forecasts and with the inferred structure of the uncertainties) has been seen as an extremely interesting tool to represent their associated uncertainties. The generation of such radar ensembles requires first the full characterization of the 3D field of associated uncertainties (2D spatial plus temporal), since rainfall estimates show an error structure highly correlated in space and time. A full methodology to deal with this kind of radar-based rainfall ensembles is presented. Given a rainfall event, the 2D uncertainty fields associated to the radar estimates are defined for every time step using a benchmark, or reference field, based on the best available estimate of the rainfall field. This benchmark is built using an advanced non parametric interpolation of a dense raingauge network able to use the spatial structure provided by the radar observations, and is confined to the region in which this combination could be taken as a reference measurement (Velasco-Forero et al. 2008, doi:10.1016/j.advwatres.2008.10.004). Then the spatial and temporal structures of these uncertainty fields are characterized and a methodology to generate consistent multiple realisations of them is used to generate the radar-based rainfall ensembles scenarios. This methodology, based on the improvement of the "String of Beads" model (Pegram and Clothier, 2001, doi:10.1016/S0022-1694(00)00373-5), is designed to preserve their main characteristics, such as anisotropy and the temporal variations of their spatial correlation. The discussion of the results on an illustrative case study and their potential interest in hydrological applications is also discussed.

Sempere-Torres, D.; Llort, X.; Roca, J.; Pegram, G.

2009-09-01

468

Radar detection of moving objects around corners  

NASA Astrophysics Data System (ADS)

Detection of moving objects around corners, with no direct line-of-sight to the objects, is demonstrated in experiments using a coherent test-range radar. A setting was built up on the test-range ground consisting of two perpendicular wall sections forming a corner, with an opposite wall, intended to mimic a street scenario on a reduced scale. Two different wall materials were used, viz. light concrete and metallic walls. The latter choice served as reference, with elimination of transmission through the walls, e.g. facilitating comparison with theoretical calculations. Standard radar reflectors were used as one kind of target objects, in horizontal, circular movement, produced by a turntable. A human formed a second target, both walking and at standstill with micro-Doppler movements of body parts. The radar signal was produced by frequency stepping of a gated CW (Continuous Wave) waveform over a bandwidth of 2 or 4 GHz, between 8.5 and 12.5 GHz. Standard Doppler signal processing has been applied, consisting of a double FFT. The first of these produced "range profiles", on which the second FFT was applied for specific range gates, which resulted in Doppler frequency spectra, used for the detection. The reference reflectors as well as the human could be detected in this scenario. The target detections were achieved both in the wave component having undergone specular reflection in the opposite wall (strongest) as well as the diffracted component around the corner. Time-frequency analysis using Short Time Fourier Transform technique brought out micro-Doppler components in the signature of a walking human. These experiments have been complemented with theoretical field calculations and separate reflection measurements of common building materials.

Sume, A.; Gustafsson, M.; Jänis, A.; Nilsson, S.; Rahm, J.; Örbom, A.

2009-05-01

469

Australian Weather Watch Radar Home Page  

NSDL National Science Digital Library

The Commonwealth Bureau of Meteorology's Weather Watch Radar website provides up-to-date radar images of the locations of rain in Australia in relation to local features such as coast lines. The newly developed Loops provide four consecutive radar images so that users can view how the weather has been changing in the last forty to fifty minutes. The website provides radar images of past cyclone events as well as updates on severe weather throughout Australia. Those interested in radar systems can discover how the weather radars work and how to interpret the maps. [RME

470

Shock wave absorber having a deformable liner  

DOEpatents

This invention discloses a shock wave absorber for a piping system carrying liquid. The absorber has a plastically deformable liner defining the normal flow boundary for an axial segment of the piping system, and a nondeformable housing is spaced outwardly from the liner so as to define a gas-tight space therebetween. The flow capacity of the liner generally corresponds to the flow capacity of the piping system line, but the liner has a noncircular cross section and extends axially of the piping system line a distance between one and twenty times the diameter thereof. Gas pressurizes the gas-tight space equal to the normal liquid pressure in the piping system. The liner has sufficient structural capacity to withstand between one and one-half and two times this normal liquid pressures; but at greater pressures it begins to plastically deform initially with respect to shape to a more circular cross section, and then with respect to material extension by circumferentially stretching the wall of the liner. A high energy shock wave passing through the liner thus plastically deforms the liner radially into the gas space and progressively also as needed in the axial direction of the shock wave to minimize transmission of the shock wave beyond the absorber.

Youngdahl, C.K.; Wiedermann, A.H.; Shin, Y.W.; Kot, C.A.; Ockert, C.E.

1983-08-26

471

Multiparameter radar analysis using wavelets  

NASA Astrophysics Data System (ADS)

Multiparameter radars have been used in the interpretation of many meteorological phenomena. Rainfall estimates can be obtained from multiparameter radar measurements. Studying and analyzing spatial variability of different rainfall algorithms, namely R(ZH), the algorithm based on reflectivity, R(ZH, ZDR), the algorithm based on reflectivity and differential reflectivity, R(KDP), the algorithm based on specific differential phase, and R(KDP, Z DR), the algorithm based on specific differential phase and differential reflectivity, are important for radar applications. The data used in this research were collected using CSU-CHILL, CP-2, and S-POL radars. In this research multiple objectives are addressed using wavelet analysis namely, (1)space time variability of various rainfall algorithms, (2)separation of convective and stratiform storms based on reflectivity measurements, (3)and detection of features such as bright bands. The bright band is a multiscale edge detection problem. In this research, the technique of multiscale edge detection is applied on the radar data collected using CP-2 radar on August 23, 1991 to detect the melting layer. In the analysis of space/time variability of rainfall algorithms, wavelet variance introduces an idea about the statistics of the radar field. In addition, multiresolution analysis of different rainfall estimates based on four algorithms, namely R(ZH), R( ZH, ZDR), R(K DP), and R(KDP, Z DR), are analyzed. The flood data of July 29, 1997 collected by CSU-CHILL radar were used for this analysis. Another set of S-POL radar data collected on May 2, 1997 at Wichita, Kansas were used as well. At each level of approximation, the detail and the approximation components are analyzed. Based on this analysis, the rainfall algorithms can be judged. From this analysis, an important result was obtained. The Z-R algorithms that are widely used do not show the full spatial variability of rainfall. In addition another intuitively obvious result was observed namely, R( KDP) has reduced the spatial variability due to smoothing of KDP estimates. The convective and stratiform separation was studied using multiresolution analysis. The June 22, 1995 data collected by CSU-CHILL radar were used to evaluate the technique. Another set of data collected on August 23, 1991 representing stratiform conditions were also studied.

Tawfik, Ben Bella Sayed

472

Space-based radar antenna thermal control  

NASA Astrophysics Data System (ADS)

Improved thermal management for large planar phased array antennas proposed for future spaced-based radar applications in Low Earth Orbit (LEO) is a critical issue. Effective and lightweight thermal management concepts are required to enhance thermal control and provide near isothermal operation during transit between daylight and eclipse periods and radar electronic power-on and off operation. Due to the planar array's large area the antenna has sufficient area to radiate the deposited power during both eclipse and daylight periods. The critical issue is keeping the antenna warm during the eclipse period, thereby maintaining the structure and sensitive electronic components near an isothermal condition. The thermal concept discussed provides a totally passive, lightweight and highly effective thermal control approach. The concept utilizes a phase change material (PCM), which exploits the large latent heat capacity for effective energy storage. In addition, the concept utilizes a new lightweight and high thermal conductivity carbon foam material to integrally contain or encapsulate the PCM. The carbon foam thermal conductivity and cell geometric characteristics result in effective thermal transfer during both thermal energy storage and extraction. The overall design concept provides a weight efficient and highly effective thermal control approach that requires no additional parasitic power. High payoff includes improved temperature control for near isothermal operation of the antenna array during the entire orbit. .

Vrable, Daniel L.; Vrable, Michael D.

2001-02-01

473

Experimental verification of metamaterial based subwavelength microwave absorbers  

NASA Astrophysics Data System (ADS)

We designed, implemented, and experimentally characterized electrically thin microwave absorbers by using the metamaterial concept. The absorbers consist of (i) a metal back plate and an artificial magnetic material layer; (ii) metamaterial back plate and a resistive sheet layer. We investigated absorber performance in terms of absorbance, fractional bandwidth, and electrical thickness, all of which depend on the dimensions of the metamaterial unit cell and the distance between the back plate and metamaterial layer. As a proof of concept, we demonstrated a ?/4.7 thick absorber of type I, with a 99.8% absorption peak along with a 8% fractional bandwidth. We have shown that as the electrical size of the metamaterial unit cell decreases, the absorber electrical thickness can further be reduced. We investigated this concept by using two different magnetic metamaterial inclusions: the split-ring resonator (SRR) and multiple SSR (MSRR). We have also demonstrated experimentally a ?/4.7 and a ?/4.2 thick absorbers of type II, based on SRR and MSRR magnetic metamaterial back plates, respectively. The absorption peak of the SRR layout is 97.4%, while for the MSRR one the absorption peak is 98.4%. The 10 dB bandwidths were 9.9% and 9.6% for the SRR and MSRR cases, respectively.

Alici, Kamil Boratay; Bilotti, Filiberto; Vegni, Lucio; Ozbay, Ekmel

2010-10-01

474

Simulation, fabrication and characterization of THz metamaterial absorbers.  

PubMed

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical(1) and experimental demonstration(2) of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical(3), near IR(4), mid IR(5) , THz(6) , mm-wave(7) , microwave(8) and radio(9) bands. Applications include perfect lenses(10), sensors(11), telecommunications(12), invisibility cloaks(13) and filters(14,15). We have recently developed single band(16), dual band(17) and broadband(18) THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers(19). In our MM absorber the THz radiation is absorbed in a thickness of ~ ?/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems. PMID:23299442

Grant, James P; McCrindle, Iain J H; Cumming, David R S

2012-12-27

475

Forecasting weather radar propagation conditions  

NASA Astrophysics Data System (ADS)

The increasing use of weather radar quantitative precipitation estimates, particularly in automatic applications such as operational hydrometeorological modelling or assimilation in numerical weather prediction (NWP) models, has promoted the development of quality control procedures on radar data. Anomalous propagation (AP) of the radar beam due to deviation from the standard refractivity vertical profile, is one of the factors that may affect seriously the quality of radar observations because of the increase in quantity and intensity of non-precipitating clutter echoes and consequent contamination of the estimated rainfall field. Another undesired effect of AP is the change in the expected radar echo height, which may be relevant when correcting for beam blockage in radar rainfall estimation in complex terrain. The aim of this paper is to study the use of NWP mesoscale forecasts to predict and monitor AP events. A nested 15-km grid resolution version of the MASS model has been used to retrieve refractivity profiles in the coastal area of Barcelona, near a weather radar and a radiosonde station. Using the refractivity profiles two different magnitudes were computed: the vertical refractivity profile of the lowest 1000 m layer and a ducting index which describes the existence and intensity of the most super-refractive layer contained in the lowest 3-km layer. A comparison between model forecasts and radiosonde diagnostics during a six-month period showed that the model tended to underestimate the degree of super-refraction, with a bias of 4 km-1 and RMSE of 11 km-1 in the 1-km vertical refractivity gradient. Further analysis of the data showed that a combination of previous observations and forecasts allowed to produce modified forecasts improving the original direct model output, decreasing substantially the bias, reducing the RMSE by 20% and improving the skill by 40%, beating also radiosonde observations persistence.

Bech, J.; Codina, B.; Lorente, J.

2007-06-01

476

Wellen Radar (WERA): a new ground-wave HF radar for ocean remote sensing  

Microsoft Academic Search

HF radars can be used to measure surface currents and wave spectra. The Coastal Radar (CODAR) used by the University of Hamburg was designed for current mapping only. It has been operated for 15 field experiments during the past 15 years. Recently, a new HF radar called Wellen Radar (WERA) has been developed at the University of Hamburg. One main

K.-W Gurgel; G Antonischki; H.-H Essen; T Schlick

1999-01-01

477

Object recognation with surveillance radar systems  

Microsoft Academic Search

In this thesis have written description and principle of radar systems and them classification. As well as radar systems are used where and for what. The most optimal signal transmission and principles of systems in general.

Gun Sergiy

2010-01-01

478

Vacuum Microwave Integrated Circuits for radar  

Microsoft Academic Search

Vacuum microwave integrated circuits (VMIC) for radar applications is suggested for design of radars with high resistance against radioactivity and high power electromagnetic. We present design of the VMIC suggested and give preliminary results of its feasibility study and implementation.

K. A. Lukin; Gun-Sik Park

2008-01-01

479

ALTAIR Radar Study of Equatorial Spread F.  

National Technical Information Service (NTIS)

The results of research on equatorial spread-F (ESF) phenomena obtained by using two backscatter radars, ALTAIR and TRADEX, are summarized. The radar measurements were made in support of three rocket campaigns conducted from the Kwajalein Atoll during the...

R. T. Tsunoda

1981-01-01

480

Planetary Ephemerides Approximation for Radar Astronomy.  

National Technical Information Service (NTIS)

The planetary ephemerides approximation for radar astronomy is discussed, and, in particular, the effect of this approximation on the performance of the programmable local oscillator (PLO) used in Goldstone Solar System Radar is presented. Four different ...

R. Sadr M. Shahshahani

1991-01-01

481

Meteor Detection on ST (MST) Radars.  

National Technical Information Service (NTIS)

The ability to detect radar echoes from backscatter due to turbulent irregularities of the radio refractive index in the clear atmosphere has lead to an increasing number of established mesosphere - stratosphere - troposphere (MST or ST) radars. Humidity ...

S. K. Avery

1987-01-01

482

Extended Target Recognition in Cognitive Radar Networks  

PubMed Central

We address the problem of adaptive waveform design for extended target recognition in cognitive radar networks. A closed-loop active target recognition radar system is extended to the case of a centralized cognitive radar network, in which a generalized likelihood ratio (GLR) based sequential hypothesis testing (SHT) framework is employed. Using Doppler velocities measured by multiple radars, the target aspect angle for each radar is calculated. The joint probability of each target hypothesis is then updated using observations from different radar line of sights (LOS). Based on these probabilities, a minimum correlation algorithm is proposed to adaptively design the transmit waveform for each radar in an amplitude fluctuation situation. Simulation results demonstrate performance improvements due to the cognitive radar network and adaptive waveform design. Our minimum correlation algorithm outperforms the eigen-waveform solution and other non-cognitive waveform design approaches.

Wei, Yimin; Meng, Huadong; Liu, Yimin; Wang, Xiqin

2010-01-01

483

Extended target recognition in cognitive radar networks.  

PubMed

We address the problem of adaptive waveform design for extended target recognition in cognitive radar networks. A closed-loop active target recognition radar system is extended to the case of a centralized cognitive radar network, in which a generalized likelihood ratio (GLR) based sequential hypothesis testing (SHT) framework is employed. Using Doppler velocities measured by multiple radars, the target aspect angle for each radar is calculated. The joint probability of each target hypothesis is then updated using observations from different radar line of sights (LOS). Based on these probabilities, a minimum correlation algorithm is proposed to adaptively design the transmit waveform for each radar in an amplitude fluctuation situation. Simulation results demonstrate performance improvements due to the cognitive radar network and adaptive waveform design. Our minimum correlation algorithm outperforms the eigen-waveform solution and other non-cognitive waveform design approaches. PMID:22163464

Wei, Yimin; Meng, Huadong; Liu, Yimin; Wang, Xiqin

2010-11-11

484

Radar Wind Profilers in the Colorado Network.  

National Technical Information Service (NTIS)

Radar systems used to measure vertical profiles of the horizontal wind in nearly all weather conditions can use frequencies between about 40 and 1000 MHz. This report describes three radar systems that measure wind profiles continuously and automatically....

R. G. Strauch D. A. Merritt K. P. Moran

1985-01-01

485

Social Radar Workflows, Dashboards, and Environments.  

National Technical Information Service (NTIS)

To build a global 'Social Radar,' an integrated set of capabilities supporting strategic and operational level situation awareness, alerts, and option awareness, there is a need for an overarching enterprise approach. Social Radar's objective is to demons...

B. Costa G. Klein J. Mathieu M. Fulk M. Lorber

2012-01-01

486

Lidar-Radar Lower Atmospheric Observations.  

National Technical Information Service (NTIS)

Daytime observations of the vertical temperature and humidity structure in the atmosphere below 1000 meters made with a Cricketsonde rocket system are compared with simultaneous observations from a ruby lidar (laser radar) and a microwave K-band radar. Ob...

W. Viezee J. Oblanas

1968-01-01

487

Range Delay Techniques for Radar Target Simulators.  

National Technical Information Service (NTIS)

It was recognized that the Radar Guided Seeker and countermeasure development using flight tests as a primary evaluation tool is costly and insecure from interception of signal and telemetry emenations. Radar Target Simulators were developed which provide...

L. C. Buse

1988-01-01

488

Multi-Radar Mapping of Auroral Convection.  

National Technical Information Service (NTIS)

Simultaneous radar azimuth scans with the Millstone Hill, Sondrestrom, and EISCAT incoherent scatter radars produce maps of the ionospheric convection electric field at high latitudes which span 10 hours of magnetic local time. A series of convection 'sna...

J. C. Foster T. Turunen P. Pollari H. Kohl V. B. Wickwar

1989-01-01

489

46 CFR 121.404 - Radars.  

Code of Federal Regulations, 2012 CFR

...OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS VESSEL CONTROL AND MISCELLANEOUS SYSTEMS AND EQUIPMENT Navigation Equipment...radar is not necessary due to the vessel's route and local weather conditions. (c) The radar and its installation must...

2012-10-01

490

3D Laser Radar Vision Processor System.  

National Technical Information Service (NTIS)

Loral Defense Systems (LDS) developed a 3D Laser Radar Vision Processor system capable of detecting, classifying, and identifying small mobile targets as well as larger fixed targets using three dimensional laser radar imagery for use with a robotic type ...

T. M. Sebok

1990-01-01

491

On Water Detection in the Martian Subsurface Using Sounding Radar  

NASA Astrophysics Data System (ADS)

Several radar experiments are planned to map the martian subsurface down to several kilometers, searching for subsurface liquid water reservoirs, using different concepts and techniques, all based on the penetration property of radio frequency waves in arid soils. The penetration depth of low-frequency radar is mainly related to the electromagnetic properties of the investigated medium. Thus a good knowledge of the martian subsurface dielectric profile along the first few kilometers is necessary for future water identification and data interpretation. In this work we have investigated the electrical and magnetic properties of the martian surface and subsurface, using terrestrial laboratory analogues in the frequency range 1-500 MHz, covering the frequency domain of the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) experiment on board the Mars Express mission (ESA-2003), the NetLander ground-penetrating radar (GPR) (CNES-2007), and future sounding radar that may be updated to the Mars exploration program in the ``follow the water'' strategy. In our approach, we constructed experimentally the most common dielectric profile representative of the martian subsurface by measuring the electric permittivity and magnetic permeability of well defined mixtures of basaltic, volcanic, and sedimentary materials that have been reported for Mars. We also considered iron oxides (hematite and maghemite) and evaporites that may be present, such as gypsum, and their mixtures with representative amounts of the martian geological context under the most common petrophysical and geophysical conditions, along the subsurface profile. This led to synthetic representative samples of the martian subsurface materials under adequate conditions of porosity and temperature that should exist in the first 2.5 km of the upper crust. Dielectric measurements show that the first layers of the martian subsurface (a few hundred meters), which are mainly composed of volcanic iron-rich materials, could dramatically decrease the radar penetration depth initially foreseen, thus limiting deep subsurface exploration. We also investigated the constraints on subsurface water detectability in a radar lossy medium and its dielectric identification among surrounding geological materials. .

Heggy, E.; Paillou, P.; Ruffie, G.; Malezieux, J. M.; Costard, F.; Grandjean, G.

2001-12-01

492

Wave Absorber with Fine Weatherability for Improving ETC Environment  

NASA Astrophysics Data System (ADS)

Wave absorber of rubber sheet containing natural rubber and EPDM is designed, fabricated and measured for improving ETC environment. As a result, proposed absorption material has fine weatherability and wave absorption satisfied with ETC standard can be realized theoretically before and after the weatherability test if the thickness of absorber is fabricated at the ranging from 2.26mm to 2.52mm. Moreover, absorber sheet sample based on theoretical values is fabricated and are measured. As a result, 20dB or more is also confirmed at the incident angle ranging from 5 to 55 degrees experimentally. Therefore, the wave absorber with fine weatherability being satisfied with ETC standard can be realized.

Miura, Yu; Matsumoto, Kouta; Okada, Osamu; Hashimoto, Osamu

493

Multi-Wavelength Radar Studies of Lunar Pyroclastic Deposits  

NASA Astrophysics Data System (ADS)

Lunar pyroclastic deposits were formed early in the Moon's history and are comprised of fine-grained, glassy materials. These low-albedo features are typically associated with mare boundaries, sites of mare volcanism, and fractures in and around impact craters. Optical, ultraviolet and infrared data have been used to map the locations of over one hundred pyroclastic deposits and to study their compositional differences (e.g. Gaddis et al., Icarus, 161, 262, 2003; Weitz et al., JGR, 103, 22725, 1998). We use multi-wavelength radar observations to study the distribution, depth and embedded rock abundance of these deposits. Data were acquired at S-band (12.6 cm wavelength) and P-band (70 cm wavelength) using Arecibo Observatory and the Green Bank Telescope in a bistatic configuration. The P-band images have resolutions of 150 m/pixel; S-band images have resolutions between 20 and 80 m/pixel. Pyroclastic deposits appear dark to the radar at both observed wavelengths because they are smooth, easily penetrable by radar waves, and generally contain few embedded blocks. At S-band wavelengths, changes in radar reflectivity across some of the pyroclastic deposits highlight areas with increased rock abundance. Radar circular polarization ratio maps can be used to identify fine-grained deposits in cases where optical or near-infrared data are ambiguous about the presence of pyro