Magnetic field effects on microwave absorbing materials

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

PO calculation for reduction in radar cross section of hypersonic targets using RAM

NASA Astrophysics Data System (ADS)

Liu, Song-hua; Guo, Li-xin; Pan, Wei-tao; Chen, Wei; Xiao, Yi-fan

2018-06-01

The radar cross section (RCS) reduction of hypersonic targets by radar absorbing materials (RAM) coating under different reentry cases is analyzed in the C and X bands frequency range normally used for radar detection. The physical optics method is extended to both the inhomogeneous plasma sheath and RAM layer present simultaneously. The simulation results show that the absorbing coating can reduce the RCS of the plasma cloaking system and its effectiveness is related to the maximum plasma frequency. Moreover, the amount of the RCS decrease, its maxima, and the corresponding optimal RAM thickness depend on the non-uniformity and parameters of the plasma sheath. In addition, the backward RCS of the flight vehicle shrouded by plasma shielding and man-made absorber is calculated and compared to the bare cone.

Wideband-Switchable Metamaterial Absorber Using Injected Liquid Metal.

PubMed

Kim, Hyung Ki; Lee, Dongju; Lim, Sungjoon

2016-08-22

Metamaterial absorbers can provide good solutions for radar-cross-section (RCS) reduction. In spite of their attractive features of thinness, lightness, and low cost, resonant metamaterial absorbers have a drawback of narrow bandwidth. For practical radar applications, wideband absorbers are necessary. In this paper, we propose a wideband-switchable metamaterial absorber using liquid metal. In order to reduce RCS both for X-band and C-band, the switchable Jerusalem cross (JC) resonator is introduced. The JC resonator consists of slotted circular rings, chip resistors, and microfluidic channels. The JC resonator is etched on a flexible printed circuit board (FPCB), and the microfluidic channels are laser-etched on a polydimethylsiloxane (PDMS) material. The proposed absorber can switch the absorption frequency band by injecting a liquid metal alloy into the channels. The performance of the absorber was demonstrated through full-wave simulation and through measurements employing prototypes. The experimental results showed absorption ratios of over 90% from 7.43 GHz to 14.34 GHz, and from 5.62 GHz to 7.3 GHz, with empty channels and liquid metal-filled channels, respectively. Therefore, the absorption band was successfully switched between the C-band (4-8 GHz) and the X-band (8-12 GHz) by injecting liquid metal eutectic gallium indium alloy (EGaIn) into the channels.

Wideband-Switchable Metamaterial Absorber Using Injected Liquid Metal

NASA Astrophysics Data System (ADS)

Kim, Hyung Ki; Lee, Dongju; Lim, Sungjoon

2016-08-01

Metamaterial absorbers can provide good solutions for radar-cross-section (RCS) reduction. In spite of their attractive features of thinness, lightness, and low cost, resonant metamaterial absorbers have a drawback of narrow bandwidth. For practical radar applications, wideband absorbers are necessary. In this paper, we propose a wideband-switchable metamaterial absorber using liquid metal. In order to reduce RCS both for X-band and C-band, the switchable Jerusalem cross (JC) resonator is introduced. The JC resonator consists of slotted circular rings, chip resistors, and microfluidic channels. The JC resonator is etched on a flexible printed circuit board (FPCB), and the microfluidic channels are laser-etched on a polydimethylsiloxane (PDMS) material. The proposed absorber can switch the absorption frequency band by injecting a liquid metal alloy into the channels. The performance of the absorber was demonstrated through full-wave simulation and through measurements employing prototypes. The experimental results showed absorption ratios of over 90% from 7.43 GHz to 14.34 GHz, and from 5.62 GHz to 7.3 GHz, with empty channels and liquid metal-filled channels, respectively. Therefore, the absorption band was successfully switched between the C-band (4-8 GHz) and the X-band (8-12 GHz) by injecting liquid metal eutectic gallium indium alloy (EGaIn) into the channels.

Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets

PubMed Central

Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, YoungPak

2015-01-01

Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet–height and diameter– and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials. PMID:26354891

Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets

NASA Astrophysics Data System (ADS)

Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, Youngpak

2015-09-01

Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet-height and diameter- and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.

Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets.

PubMed

Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, YoungPak

2015-09-10

Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet-height and diameter- and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.

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

NASA Astrophysics Data System (ADS)

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

2011-01-01

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.

Additive manufacturing of RF absorbers

NASA Astrophysics Data System (ADS)

Mills, Matthew S.

The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.

Influence of Reduced Graphene Oxide on Effective Absorption Bandwidth Shift of Hybrid Absorbers.

PubMed

Ameer, Shahid; Gul, Iftikhar Hussain

2016-01-01

The magnetic nanoparticle composite NiFe2O4 has traditionally been studied for high-frequency microwave absorption with marginal performance towards low-frequency radar bands (particularly L and S bands). Here, NiFe2O4 nanoparticles and nanohybrids using large-diameter graphene oxide (GO) sheets are prepared via solvothermal synthesis for low-frequency wide bandwidth shielding (L and S radar bands). The synthesized materials were characterized using XRD, SEM, FTIR and microwave magneto dielectric spectroscopy. The dimension of these solvothermally synthesized pristine particles and hybrids lies within 30-58 nm. Microwave magneto-dielectric spectroscopy was performed in the low-frequency region in the 1 MHz-3 GHz spectrum. The as-synthesized pristine nanoparticles and hybrids were found to be highly absorbing for microwaves throughout the L and S radar bands (< -10 dB from 1 MHz to 3 GHz). This excellent microwave absorbing property induced by graphene sheet coupling shows application of these materials with absorption bandwidth which is tailored such that these could be used for low frequency. Previously, these were used for high frequency absorptions (typically > 4 GHz) with limited selective bandwidth.

Absorber Materials for Transition-Edge Sensor X-ray Microcalorimeters

NASA Technical Reports Server (NTRS)

Brown, Ari-David; Bandler, Simon; Brekosky, Regis; Chervenak, James; Figueroa-Feliciano, Enectali; Finkbeiner, Fred; Sadleir, Jack; Iyomoto, Naoko; Kelley, Richard; Kilbourne, Caroline;

Tech Transfer Webinar: Energy Absorbing Materials

ScienceCinema

Duoss, Eric

2018-01-16

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

Design and Manufacture of Energy Absorbing Materials

ScienceCinema

Duoss, Eric

2018-01-16

Learn about an ordered cellular material that has been designed and manufactured using direct ink writing (DIW), a 3-D printing technology being developed at LLNL. The new material is a patterned cellular material that can absorb mechanical energy-a cushion-while also providing protection against sheering. This material is expected to find utility in application spaces that currently use unordered foams, such as sporting and consumer goods as well as defense and aerospace.

A comparative study between different approaches to improve the RCS of a compact double-layer absorber

NASA Astrophysics Data System (ADS)

El-Hakim, H. A.; Mahmoud, K. R.

2017-10-01

In this paper, straightforward and efficient techniques have been addressed into double-layer structure to enlarge the operating bandwidth to include the X, Ku and K bands, in addition to increase the electromagnetic wave absorption for wide varieties of incident angles and both polarization types. To increase the band-stop resonating frequency up to 26 GHz, an additional layer of meta-surface, circuit analog radar absorber material (CAR), or a thin radar absorber material (RAM) layer is engineered. The synthesized layers are designed based on optimization process with genetic algorithm (GA) through numerical technique (Ansoft design software HFSS) for both transmission line (T.L) and the free space method to get optimal material properties suitable for the design. For different approaches, the designed structures achieved a reflectivity value less than -16 dB on average in the desired bandwidth from 8 to 26 GHz for TE/TM modes with incidence angle up to 50o.

Investigations on Absorber Materials at Cryogenic Temperatures

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

Marhauser, Frank; Elliott, Thomas; Rimmer, Robert

2009-05-01

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

Porcelain enamel neutron absorbing material

DOEpatents

Iverson, Daniel C.

1990-01-01

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.

Porcelain enamel neutron absorbing material

DOEpatents

Iverson, Daniel C.

1990-02-06

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.

A Wide Band Absorbing Material Design Using Band-Pass Frequency Selective Surface

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Xu, Qiang; Liu, Ting; Zheng, Dianliang; Zhou, Li

2018-03-01

Based on the high frequency advantage characteristics of the Fe based absorbing coating, a method for designing the structure of broadband absorbing structure by using frequency selective surface (FSS) is proposed. According to the transmission and reflection characteristic of the different size FSS structure, the frequency variation characteristic was simulated. Secondly, the genetic algorithm was used to optimize the high frequency broadband absorbing materials, including the single and double magnetic layer material. Finally, the absorbing characteristics in iron layer were analyzed as the band pass FSS structure was embedded, the results showed that the band-pass FSS had the influence on widening the absorbing frequency. As the FSS was set as the bottom layer, it was effective to achieve the good absorbing property in low frequency and the high frequency absorbing performance was not weakened, because the band-pass FSS led the low frequency absorption and the high frequency shielding effect. The results of this paper are of guiding significance for designing and manufacturing the broadband absorbing materials.

Reflection and transmission for layered composite materials

NASA Technical Reports Server (NTRS)

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

1991-01-01

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.

Boron cage compound materials and composites for shielding and absorbing neutrons

DOEpatents

Bowen, III, Daniel E; Eastwood, Eric A

2014-03-04

Boron cage compound-containing materials for shielding and absorbing neutrons. The materials include BCC-containing composites and compounds. BCC-containing compounds comprise a host polymer and a BCC attached thereto. BCC-containing composites comprise a mixture of a polymer matrix and a BCC filler. The BCC-containing materials can be used to form numerous articles of manufacture for shielding and absorbing neutrons.

Design of broadband absorber using 2-D materials for thermo-photovoltaic cell application

NASA Astrophysics Data System (ADS)

Agarwal, Sajal; Prajapati, Y. K.

2018-04-01

Present study is done to analyze a nano absorber for thermo-photovoltaic cell application. Optical absorbance of two-dimensional materials is exploited to achieve high absorbance. It is found that few alternating layers of graphene/transition metal dichalcogenide provide high absorbance of electromagnetic wave in visible as well as near infrared region. Four transition metal dichalcogenides are considered and found that most of these provide perfect absorbance for almost full considered wavelength range i.e. 200-1000 nm. Demonstrated results confirm the extended operating region and improved absorbance of the proposed absorber in comparison to the existing absorbers made of different materials. Further, absorber performance is improved by using thin layers of gold and chromium. Simple geometry of the proposed absorber also ensures easy fabrication.

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)

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

2013-09-01

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.

Porcelain enamel neutron absorbing material

DOEpatents

Iverson, D.C.

1987-11-20

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.

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

NASA Technical Reports Server (NTRS)

Petre-Lazar, S.; Popeea, G.

1974-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2005-12-01

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

Optimization on microwave absorbing properties of carbon nanotubes and magnetic oxide composite materials

NASA Astrophysics Data System (ADS)

Mingdong, Chen; Huangzhong, Yu; Xiaohua, Jie; Yigang, Lu

2018-03-01

Based on the physical principle of interaction between electromagnetic field and the electromagnetic medium, the relationship between microwave absorbing coefficient (MAC) and the electromagnetic parameters of materials was established. With the composite materials of nickel ferrite (NiFe2O4), carbon nanotubes (CNTs) and paraffin as an example, optimization on absorbing properties of CNTs/magnetic oxide composite materials was studied at the frequency range of 2-18 GHz, and a conclusion is drawn that the MAC is the biggest at the same frequency, when the CNTs is 10 wt% in the composite materials. Through study on the relationship between complex permeability and MAC, another interesting conclusion is drawn that MAC is obviously affected by the real part of complex permeability, and increasing real part of complex permeability is beneficial for improving absorbing properties. The conclusion of this paper can provide a useful reference for the optimization research on the microwave absorbing properties of CNTs/ferrite composite materials.

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

NASA Astrophysics Data System (ADS)

McCluggage, W. A.

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

Determining the Absorbance Spectra of Photochromic Materials From Measured Spectrophotometer Data

NASA Technical Reports Server (NTRS)

Downie, John D.

1998-01-01

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

Synthesis and microwave absorbing characteristics of functionally graded carbonyl iron/polyurethane composites

NASA Astrophysics Data System (ADS)

Yang, R. B.; Liang, W. F.; Wu, C. H.; Chen, C. C.

2016-05-01

Radar absorbing materials (RAMs) also known as microwave absorbers, which can absorb and dissipate incident electromagnetic wave, are widely used in the fields of radar-cross section reduction, electromagnetic interference (EMI) reduction and human health protection. In this study, the synthesis of functionally graded material (FGM) (CI/Polyurethane composites), which is fabricated with semi-sequentially varied composition along the thickness, is implemented with a genetic algorithm (GA) to optimize the microwave absorption efficiency and bandwidth of FGM. For impedance matching and broad-band design, the original 8-layered FGM was obtained by the GA method to calculate the thickness of each layer for a sequential stacking of FGM from 20, 30, 40, 50, 60, 65, 70 and 75 wt% of CI fillers. The reflection loss of the original 8-layered FGM below -10 dB can be obtained in the frequency range of 5.12˜18 GHz with a total thickness of 9.66 mm. Further optimization reduces the number of the layers and the stacking sequence of the optimized 4-layered FGM is 20, 30, 65, 75 wt% with thickness of 0.8, 1.6, 0.6 and 1.0 mm, respectively. The synthesis and measurement of the optimized 4-layered FGM with a thickness of 4 mm reveal a minimum reflection loss of -25.2 dB at 6.64 GHz and its bandwidth below - 10 dB is larger than 12.8 GHz.

Acoustic behavior of a fibrous bulk material. [Kevlar 29 sound absorber

NASA Technical Reports Server (NTRS)

Hersh, A. S.; Walker, B.

1979-01-01

A semiempirical model is presented describing the acoustic behavior of Kevlar 29, a bulk absorbing material. The model is based on an approximate solution to the one-dimensional equations representing conservation of fluctuating mass, momentum and energy. By treating the material as a momentum sink, theoretical expressions of the material complex propagation constants and characteristic impedance were derived in terms of a single constant. Evaluating the constant at a single frequency for a particular specimen, excellent agreement between prediction and measurement was achieved for a large range of sound frequencies and material porosities and thicknesses. Results show that Kevlar 29 absorbs sound efficiently even at low frequencies. This is explained in terms of a frequency dependent material phase speed.

Selective wave-transmitting electromagnetic absorber through composite metasurface

NASA Astrophysics Data System (ADS)

Sun, Zhiwei; Zhao, Junming; Zhu, Bo; Jiang, Tian; Feng, Yijun

2017-11-01

Selective wave-transmitting absorbers which have one or more narrow transmission bands inside a wide absorption band are often demanded in wireless communication and radome applications for reducing the coupling between different systems, improving anti-jamming capability, and reducing antennas' radar cross section. Here we propose a feasible method that utilizing composite of two metasurfaces with different polarization dependent characteristics, one works as electromagnetic polarization rotator and the other as a wideband polarization dependent electromagnetic wave absorber. The polarization rotator produces a cross polarization output in the wave-transmitting band, while preserves the polarization of the incidence outside the band. The metasurface absorber works for certain linear polarization with a much wider absorption band covering the wave-transmitting frequency. When combining these two metasurfaces properly, the whole structure behaves as a wideband absorber with a certain frequency transmission window. The proposal may be applied in radome designs to reduce the radar cross section of antenna or improving the electromagnetic compatibility in communication devices.

Review of Radar Absorbing Materials

DTIC Science & Technology

2005-01-01

Symposium, 1990. AP-S. Merging technologies for the 90’s. Digest 1990, 3, 1212. (30) Nortier, J. R., Van der Neut , C.A., Baker, D.E. Microwave Journal...1987, 219. (31) Kasevich, R. S.; Broderick, F., US Patent 5223849. 1993. (32) Van Der Plas, G., Barel, A., Schweicher, E. Antennas and Propagation

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

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

Brock, Billy C.; Loui, Hung; McDonald, Jacob J.

2012-03-05

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,more » 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.« less

Rhea's Surface: Ice Properties Measured by Radar.

NASA Astrophysics Data System (ADS)

Black, G.; Campbell, D.

2004-11-01

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

Application of Absorbable Hemostatic Materials Observed in Thyroid Operation

NASA Astrophysics Data System (ADS)

Li, Yan-Ming; Liang, Zhen-Zhen; Song, Yan

2016-05-01

To observe the application effects of the absorbable hemostatic materials in thyroid operation. Methods: From May 2014 to January 2015, 100 patients with thyroid surgery in our university affiliated hospital were selected as the research object. Randomly divided into experimental group and control group, 50 cases in each group. Application of absorbable hemostatic hemostatic materials in the experimental group during the operation, the control group using the traditional mechanical methods of hemostasis hemostasis to observe the operation time, bleeding volume, postoperative drainage volume, complications and hospital stay of the two groups. Results: The operation time, bleeding volume, postoperative drainage and hospital stay in the experimental group were significantly lower in the study group than in the control group, and the difference between the two groups was statistically significant (P< 0.05); The satisfaction of patients in the experimental group was significantly higher than that in the control group, the difference was statistically significant in the two groups (P < 0.05); There was no significant difference in the incidence of wound bleeding complications between the study group and the control group (P > 0.05). Conclusion: Absorbable hemostatic materials can effectively shorten the operation time, reduce intraoperative blood loss and postoperative drainage, reduce the length of hospital stay and improve the success rate of surgery and patient satisfaction, which is worthy to be popularized in clinical thyroid surgery.

Absorbable synthetic versus catgut suture material for perineal repair

PubMed Central

Kettle, Christine

2014-01-01

Background Approximately 70% of women will experience some degree of perineal trauma following vaginal delivery and will require stitches. This may result in perineal pain and superficial dyspareunia. Objectives The objective of this review was to assess the effects of absorbable synthetic suture material as compared with catgut on the amount of short and long term pain experienced by mothers following perineal repair. Search strategy We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register. Selection criteria Randomised trials comparing absorbable synthetic (polyglycolic acid and polyglactin) with plain or chromic catgut suture for perineal repair in mothers after vaginal delivery. Data collection and analysis Trial quality was assessed independently by two reviewers. Data were extracted by one reviewer and checked by the second reviewer. Main results Eight trials were included. Compared with catgut, the polyglycolic acid and polyglactin groups were associated with less pain in first three days (odds ratio 0.62, 95% confidence interval 0.54 to 0.71). There was also less need for analgesia (odds ratio 0.63, 95% confidence interval 0.52 to 0.77) and less suture dehiscence (odds ratio 0.45, 95% confidence interval 0.29 to 0.70). There was no significant difference in long term pain (odds ratio 0.81, 95% confidence interval 0.61 to 1.08). Removal of suture material was significantly more common in the polyglycolic acid and polyglactin groups (odds ratio 2.01, 95% confidence interval 1.56 to 2.58). There was no difference in the amount of dyspareunia experienced by women. Authors’ conclusions Absorbable synthetic suture material (in the form of polyglycolic acid and polyglactin sutures) for perineal repair following childbirth appears to decrease women’s experience of short-term pain. The length of time taken for the synthetic material to be absorbed is of concern. A trial addressing the use of polyglactin has recently been completed and this has

Study of sound-absorbing properties of glass-fiber reinforced materials used in engineering

NASA Astrophysics Data System (ADS)

Egorova, V. E.; Habibova, R. R.; Shafigullin, L. N.

2017-09-01

Modern engineering makes high demands to the noise level in the passenger compartment or cabin of KAMAZ. An effective means of dealing with noise is to use sound absorbing materials produced by the automotive industry. To increase sound-absorbing capacity of materials and structures using glass fibre reinforced polyurethane foams (PUF) obtained by the technology Fiber Composite Spraying.

Preparation and characterization of functional material based on hybrid polymer composites

NASA Astrophysics Data System (ADS)

Agusu, La; Amiruddin; Taswito, Chen Chen; Herdianto; Zamrun, Muh.

2016-08-01

The microstructures and properties of hybrid polymer composites based on polyaniline (PANi)/γ-Fe2O3 nanoparticles/TiO2/carbon have been investigated for multifunctional applications such as heavy metal removal and initial study for radar absorbing material application. γ-Fe2O3 nanoparticles with spherical shape were synthetized by a coprecipitation method from iron sand. By activating the polyethylene glycol (PEG-400) coated carbon of coconut shell, the homogenous shape and size of carbon was achieved. Then, γ- Fe2O3, TiO2, and carbon were mixed with PANi by an in situ polymerization method at low temperature 0-5 oC. Characterization process involved XRD, SEM, FTIR, VSM, and DC conductivity measurements. For radar absorber application, the functionalized polymer composites showed good electrical conductivity 0.45 S/cm to absorb the incoming electromagnetic energy. An efficient and effective reduction of Pb2+ ion from the water has been achieved by using this material.

Potential application of a homogeneous and anisotropic slab as an angle insensitive absorbing material

NASA Astrophysics Data System (ADS)

Wang, Fang; Liu, Chang; Liu, Xiaoning; Niu, Tiaoming; Wang, Jing; Mei, Zhonglei; Qin, Jiayong

2017-06-01

In this paper, a flat and incident angle independence absorbing material is proposed and numerically verified in the optical spectrum. A homogeneous and anisotropic dielectric slab as a non-reflecting layer is first reviewed, and a feasible realization strategy of the slab is then given by using layered isotropic materials. When the loss components of the constitutive materials are not zero, the slab will work as an angle insensitive absorbing layer, and the absorption rate augments with increase of the losses. As the numerical verifications, the field distributions of a metallic cylinder and a triangular metallic object individually covered by the designed absorbing layer are demonstrated. The simulation results show that the designed absorbing layer can efficiently absorb the incident waves with the property of incident angle independence at the operation frequency. This homogeneous slab can be used in one and two dimensional situations for the realization of an invisibility cloak, a carpet cloak and even a skin cloak, if it is used to conformally cover target objects.

Super water-absorbing new material from chitosan, EDTA and urea.

PubMed

Narayanan, Abathodharanan; Dhamodharan, Raghavachari

2015-12-10

A new, super water-absorbing, material is synthesized by the reaction between chitosan, EDTA and urea and named as CHEDUR. CHEDUR is probably formed through the crosslinking of chitosan molecules (CH) with the EDTA-urea (EDUR) adduct that is formed during the reaction. CHEDUR as well as the other products formed in control reactions are characterized extensively. CHEDUR exhibits a very high water uptake capacity when compared with chitosan, chitosan-EDTA adduct, as well as a commercial diaper material. A systematic study was done to find the optimum composition as well as reaction conditions for maximum water absorbing capacity. CHEDUR can play a vital role in applications that demand the rapid absorption and slow release of water such as agriculture, as a three in one new material for the slow release of urea, water and other metal ions that can be attached through the EDTA component. The other potential advantage of CHEDUR is that it can be expected to degrade in soil based on its chitosan backbone. The new material with rapid and high water uptake could also find potential applications as biodegradable active ingredient of the diaper material. Copyright © 2015 Elsevier Ltd. All rights reserved.

Porphyrin Based Near Infrared-Absorbing Materials for Organic Photovoltaics

NASA Astrophysics Data System (ADS)

Zhong, Qiwen

The conservation and transformation of energy is essential to the survival of mankind, and thus concerns every modern society. Solar energy, as an everlasting source of energy, holds one of the key solutions to some of the most urgent problems the world now faces, such as global warming and the oil crisis. Advances in technologies utilizing clean, abundant solar energy, could be the steering wheel of our societies. Solar cells, one of the major advances in converting solar energy into electricity, are now capturing people's interest all over the globe. While solar cells have been commercially available for many years, the manufacturing of solar cells is quite expensive, limiting their broad based implementation. The cost of solar cell based electricity is 15-50 cents per kilowatt hour (¢/kwh), depending on the type of solar cell, compared to 0.7 ¢/kwh for fossil fuel based electricity. Clearly, decreasing the cost of electricity from solar cells is critical for their wide spread deployment. This will require a decrease in the cost of light absorbing materials and material processing used in fabricating the cells. Organic photovoltaics (OPVs) utilize organic materials such as polymers and small molecules. These devices have the advantage of being flexible and lower cost than conventional solar cells built from inorganic semiconductors (e.g. silicon). The low cost of OPVs is tied to lower materials and fabrication costs of organic cells. However, the current power conversion efficiencies of OPVs are still below 15%, while convention crystalline Si cells have efficiencies of 20-25%. A key limitation in OPVs today is their inability to utilize the near infrared (NIR) portion of the solar spectrum. This part of the spectrum comprises nearly half of the energy in sunlight that could be used to make electricity. The first and foremost step in conversion solar energy conversion is the absorption of light, which nature has provided us optimal model of, which is

Food-processes wastewaters treatment using food solid-waste materials as adsorbents or absorbents

NASA Astrophysics Data System (ADS)

Rapti, Ilaira; Georgopoulos, Stavros; Antonopoulou, Maria; Konstantinou, Ioannis; Papadaki, Maria

2016-04-01

The wastewaters generated by olive-mills during the production of olive oil, wastewaters from a dairy and a cow-farm unit and wastewaters from a small food factory have been treated by means of selected materials, either by-products of the same units, or other solid waste, as absorbents or adsorbents in order to identify the capacity of those materials to remove organic load and toxicity from the aforementioned wastewaters. The potential of both the materials used as absorbents as well as the treated wastewaters to be further used either as fertilizers or for agricultural irrigation purposes are examined. Dry olive leaves, sheep wool, rice husks, etc. were used either in a fixed-bed or in a stirred batch arrangemen,t employing different initial concentrations of the aforementioned wastewaters. The efficiency of removal was assessed using scpectrophotometric methods and allium test phytotoxicity measurements. In this presentation the response of each material employed is shown as a function of absorbent/adsorbent quantity and kind, treatment time and wastewater kind and initial organic load. Preliminary results on the potential uses of the adsorbents/absorbents and the treated wastewaters are also shown. Keywords: Olive-mill wastewaters, dairy farm wastewaters, olive leaves, zeolite, sheep wool

Material Model Evaluation of a Composite Honeycomb Energy Absorber

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

Utilizing strongly absorbing materials for low-loss surface-wave nonlinear optics

NASA Astrophysics Data System (ADS)

Grosse, Nicolai B.; Franz, Philipp; Heckmann, Jan; Pufahl, Karsten; Woggon, Ulrike

2018-04-01

Optical media endowed with large nonlinear susceptibilities are highly prized for their employment in frequency conversion and the generation of nonclassical states of light. Although the presence of an optical resonance can greatly increase the nonlinear response (e.g., in epsilon-near-zero materials), the non-negligible increase in linear absorption often precludes the application of such materials in nonlinear optics. Absorbing materials prepared as thin films, however, can support a low-loss surface wave: the long-range surface exciton polariton (LRSEP). Its propagation lifetime increases with greater intrinsic absorption and reduced film thickness, provided that the film is embedded in a transparent medium (symmetric cladding). We explore LRSEP propagation in a molybdenum film by way of a prism-coupling configuration. Our observations show that excitation of the LRSEP mode leads to a dramatic increase in the yield of second-harmonic generation. This implies that the LRSEP mode is an effective vehicle for utilizing the nonlinear response of absorbing materials.

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

PubMed

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

2013-12-01

Microwave absorbing material plays a great role in electromagnetic pollution controlling, electromagnetic interference shielding and stealth technology, etc. The core-nanoshell composite materials doped with La were prepared by a solid-state reaction method, which is applied to the electromagnetic wave absorption. The core is magnetic fly-ash hollow cenosphere, and the shell is the nanosized ferrite doped with La. The thermal decomposition process of the sample was investigated by thermogravimetry and differential thermal analysis. The morphology and components of the composite materials were investigated by the X-ray diffraction analysis, the microstructure was observed by scanning electron microscope and transmission electron microscope. The results of vibrating sample magnetometer analysis indicated that the exchange-coupling interaction happens between ferrite of magnetic fly-ash hollow cenosphere and nanosized ferrite coating, which caused outstanding magnetic properties. The microwave absorbing property of the sample was measured by reflectivity far field radar cross section of radar microwave absorbing material with vector network analyzer. The results indicated that the exchange-coupling interaction enhanced magnetic loss of composite materials. Therefore, in the frequency of 5 GHz, the reflection coefficient can achieve -24 dB. It is better than single material and is consistent with requirements of the microwave absorbing material at the low-frequency absorption. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

A Triaxial Applicator for the Measurement of the Electromagnetic Properties of Materials

PubMed Central

2018-01-01

The design, analysis, and fabrication of a prototype triaxial applicator is described. The applicator provides both reflected and transmitted signals that can be used to characterize the electromagnetic properties of materials in situ. A method for calibrating the probe is outlined and validated using simulated data. Fabrication of the probe is discussed, and measured data for typical absorbing materials and for the probe situated in air are presented. The simulations and measurements suggest that the probe should be useful for measuring the properties of common radar absorbing materials under usual in situ conditions. PMID:29382122

Dendritic-metasurface-based flexible broadband microwave absorbers

NASA Astrophysics Data System (ADS)

Wang, Mei; Weng, Bin; Zhao, Jing; Zhao, Xiaopeng

2017-06-01

Based on the dendritic metasurface model, a type of flexible and lightweight microwave absorber (MA) comprising resistance film array with dendritic slot (RFADS), dielectric material, and metal plate is proposed. A broadband absorptivity of >80% is obtained both from simulation and experiment at frequency ranges of 3.0-9.2 and 3.2-9.00 GHz, respectively. And the thickness of MA is 5 mm, which is only 0.05λ _{low}, or 0.15λ _ {high}, where the λ _{low} and the λ _{high} are the beginning and the end of the working frequency. By combining this metasurface-based MA with the dendritic-resistance-film-based microwave metasurface absorber (MMA), we designed a broadband MMA. The simulations and experiments showed that this kind of MMA can absorb the radiation effectively at a wide frequency range 4.5-17.5 GHz. And the thickness of this combined MMA is 4 mm. All the structures showed their insensitivity to the incident angle (0°-40°) and the polarization of the incident wave because of their structural symmetry. In addition, the small thickness, low apparent density, and flexibility made those structures possess the advantages of being applied in microwave stealth and radar cross-section (RCS) reduction.

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

NASA Astrophysics Data System (ADS)

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

2014-02-01

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

Corrosion resistant neutron absorbing coatings

DOEpatents

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

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.

Corrosion resistant neutron absorbing coatings

DOEpatents

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

2013-11-12

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.

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

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

Glover, Brian B; Whites, Kieth W; Radway, Matthew J

2009-01-01

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

Absorbing Boundary Conditions For Optical Pulses In Dispersive, Nonlinear Materials

NASA Technical Reports Server (NTRS)

Goorjian, Peter M.; Kwak, Dochan (Technical Monitor)

1995-01-01

This paper will present results in computational nonlinear optics. An algorithm will be described that provides absorbing boundary conditions for optical pulses in dispersive, nonlinear materials. A new numerical absorber at the boundaries has been developed that is responsive to the spectral content of the pulse. Also, results will be shown of calculations of 2-D electromagnetic nonlinear waves computed by directly integrating in time the nonlinear vector Maxwell's equations. The results will include simulations of "light bullet" like pulses. Here diffraction and dispersion will be counteracted by nonlinear effects. Comparisons will be shown of calculations that use the standard boundary conditions and the new ones.

Improving impact resistance of ceramic materials by energy absorbing surface layers

NASA Technical Reports Server (NTRS)

Kirchner, H. P.; Seretsky, J.

1974-01-01

Energy absorbing surface layers were used to improve the impact resistance of silicon nitride and silicon carbide ceramics. Low elastic modulus materials were used. In some cases, the low elastic modulus was achieved using materials that form localized microcracks as a result of thermal expansion anisotropy, thermal expansion differences between phases, or phase transformations. In other cases, semi-vitreous or vitreous materials were used. Substantial improvements in impact resistance were observed at room and elevated temperatures.

Stability of an arch type shock absorber made of a rubber-like material

NASA Astrophysics Data System (ADS)

Kabrits, Sergey A.; Kolpak, Eugeny P.

2018-05-01

The paper considers the stability problem of an arch shock absorber made of a rubber-like material. As a model, the nonlinear theory of thin shells from elastomers K.F. Chernykh is used. The case of symmetrical and asymmetrical deformation of an arch shock absorber under symmetrical compression is investigated. The possibility of asymmetric bifurcation is evaluated depending on the boundary conditions.

Composition for absorbing hydrogen

DOEpatents

Heung, L.K.; Wicks, G.G.; Enz, G.L.

1995-05-02

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

Composition for absorbing hydrogen

DOEpatents

Heung, Leung K.; Wicks, George G.; Enz, Glenn L.

1995-01-01

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

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

PubMed

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

2014-06-01

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

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

NASA Astrophysics Data System (ADS)

Mandal, Avinandan; Das, Chapal Kumar

2013-01-01

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

Flexible metamaterial absorbers for stealth applications at terahertz frequencies.

PubMed

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

2012-01-02

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.

Damage tolerant light absorbing material

DOEpatents

Lauf, Robert J.; Hamby, Jr., Clyde; Akerman, M. Alfred; Seals, Roland D.

1993-01-01

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.

Damage tolerant light absorbing material

DOEpatents

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

1993-09-07

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.

An antibacterial and absorbable silk-based fixation material with impressive mechanical properties and biocompatibility

NASA Astrophysics Data System (ADS)

Shi, Chenglong; Pu, Xiaobing; Zheng, Guan; Feng, Xinglong; Yang, Xuan; Zhang, Baoliang; Zhang, Yu; Yin, Qingshui; Xia, Hong

2016-11-01

Implant-associated infections and non-absorbing materials are two important reasons for a second surgical procedure to remove internal fixation devices after an orthopedic internal fixation surgery. The objective of this study was to produce an antibacterial and absorbable fixation screw by adding gentamicin to silk-based materials. The antibacterial activity was assessed against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro by plate cultivation and scanning electron microscopy (SEM). We also investigated the properties, such as the mechanical features, swelling properties, biocompatibility and degradation, of gentamicin-loaded silk-based screws (GSS) in vitro. The GSS showed significant bactericidal effects against S. aureus and E. coli. The antibacterial activity remained high even after 4 weeks of immersion in protease solution. In addition, the GSS maintained the remarkable mechanical properties and excellent biocompatibility of pure silk-based screws (PSS). Interestingly, after gentamicin incorporation, the degradation rate and water-absorbing capacity increased and decreased, respectively. These GSS provide both impressive material properties and antibacterial activity and have great potential for use in orthopedic implants to reduce the incidence of second surgeries.

Material Activation Benchmark Experiments at the NuMI Hadron Absorber Hall in Fermilab

NASA Astrophysics Data System (ADS)

Matsumura, H.; Matsuda, N.; Kasugai, Y.; Toyoda, A.; Yashima, H.; Sekimoto, S.; Iwase, H.; Oishi, K.; Sakamoto, Y.; Nakashima, H.; Leveling, A.; Boehnlein, D.; Lauten, G.; Mokhov, N.; Vaziri, K.

2014-06-01

In our previous study, double and mirror symmetric activation peaks found for Al and Au arranged spatially on the back of the Hadron absorber of the NuMI beamline in Fermilab were considerably higher than those expected purely from muon-induced reactions. From material activation bench-mark experiments, we conclude that this activation is due to hadrons with energy greater than 3 GeV that had passed downstream through small gaps in the hadron absorber.

Neutron absorbers and methods of forming at least a portion of a neutron absorber

DOEpatents

Guillen, Donna P; Porter, Douglas L; Swank, W David; Erickson, Arnold W

2014-12-02

Methods of forming at least a portion of a neutron absorber include combining a first material and a second material to form a compound, reducing the compound into a plurality of particles, mixing the plurality of particles with a third material, and pressing the mixture of the plurality of particles and the third material. One or more components of neutron absorbers may be formed by such methods. Neutron absorbers may include a composite material including an intermetallic compound comprising hafnium aluminide and a matrix material comprising pure aluminum.

Cassini RADAR at Titan : Results in 2014/2015

NASA Astrophysics Data System (ADS)

Lorenz, Ralph D.

2015-04-01

Since the last EGU meeting, two Cassini flybys of Titan will have featured significant RADAR observations, illuminating our understanding of this enigmatic, complex world and its hydrocarbon seas in particular. T104, which executed in August 2014, featured a nadir-pointed altimetry swath over the northern part of Kraken Mare, Titan's largest sea. The echo characteristics showed that the sea surface was generally flat (to within a few mm), although a couple of areas appear to show some evidence of roughness. Intriguingly, altimetry processing which yielded (Mastrogiuseppe et al., GRL, 2014) the detection of a prominent bottom echo 160m beneath the surface of Ligeia Mare on T91 failed to yield a similar echo over most of Kraken on T104, suggesting either that Kraken is very deep (perhaps consistent with rather steep shoreline topography) or that the liquid in Kraken is more radar-absorbing than that in Ligeia, or both. The absorbing-liquid scenario may be consistent with a hydrological model for Titan's seas (Lorenz, GRL, 2014) wherein the most northerly seas receive more 'fresh' methane input, flushing ethane and other lower-volatility (and more radar-absorbing) solutes south into Kraken. T108, the last northern seas radar observation until T126 at the very end of the Cassini tour in 2017, is planned to execute on 11th January 2015, and preliminary results will be presented at the EGU meeting. This flyby features altimetry over part of Punga Mare, which will provide surface roughness information and possible bathymetry, permitting comparison of nadir-pointed data over all of Titan's three seas (Ligeia on T91; Kraken Mare on T104). The flyby also includes SAR observation of the so-called Ligeia 'Magic Island', the best-observed of several areas of varying radar brightness on Titan's seas. This brightness may be due to sediments suspended by currents, or by roughening of the surface either by local wind stress ('catspaw') or non-local stress (wind-driven currents

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

USGS Publications Warehouse

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

2001-01-01

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

Development of a primary standard for absorbed dose from unsealed radionuclide solutions

NASA Astrophysics Data System (ADS)

Billas, I.; Shipley, D.; Galer, S.; Bass, G.; Sander, T.; Fenwick, A.; Smyth, V.

2016-12-01

Currently, the determination of the internal absorbed dose to tissue from an administered radionuclide solution relies on Monte Carlo (MC) calculations based on published nuclear decay data, such as emission probabilities and energies. In order to validate these methods with measurements, it is necessary to achieve the required traceability of the internal absorbed dose measurements of a radionuclide solution to a primary standard of absorbed dose. The purpose of this work was to develop a suitable primary standard. A comparison between measurements and calculations of absorbed dose allows the validation of the internal radiation dose assessment methods. The absorbed dose from an yttrium-90 chloride (90YCl) solution was measured with an extrapolation chamber. A phantom was developed at the National Physical Laboratory (NPL), the UK’s National Measurement Institute, to position the extrapolation chamber as closely as possible to the surface of the solution. The performance of the extrapolation chamber was characterised and a full uncertainty budget for the absorbed dose determination was obtained. Absorbed dose to air in the collecting volume of the chamber was converted to absorbed dose at the centre of the radionuclide solution by applying a MC calculated correction factor. This allowed a direct comparison of the analytically calculated and experimentally determined absorbed dose of an 90YCl solution. The relative standard uncertainty in the measurement of absorbed dose at the centre of an 90YCl solution with the extrapolation chamber was found to be 1.6% (k  =  1). The calculated 90Y absorbed doses from published medical internal radiation dose (MIRD) and radiation dose assessment resource (RADAR) data agreed with measurements to within 1.5% and 1.4%, respectively. This study has shown that it is feasible to use an extrapolation chamber for performing primary standard absorbed dose measurements of an unsealed radionuclide solution. Internal radiation

Multistep Cylindrical Structure Analysis at Normal Incidence Based on Water-Substrate Broadband Metamaterial Absorbers

NASA Astrophysics Data System (ADS)

Fang, Chonghua

2018-01-01

A new multistep cylindrical structure based on water-substrate broadband metamaterial absorbers is designed to reduce the traditional radar cross-section (RCS) of a rod-shaped object. The proposed configuration consists of two distinct parts. One of these components is formed by a four-step cylindrical metal structure, whereas the other one is formed by a new water-substrate broadband metamaterial absorber. The designed structure can significantly reduce the radar cross section more than 10 dB from 4.58 to 18.42 GHz which is the 86.5 % bandwidth of from C-band to 20 GHz. The results of measurement show reasonably good accordance with the simulated ones, which verifies the ability and effect of the proposed design.

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

DOEpatents

Crane, Thomas W.

1986-01-01

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

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

DOEpatents

Crane, T.W.

1983-12-21

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

Signature management of radar returns from wind turbine generators

NASA Astrophysics Data System (ADS)

Tennant, A.; Chambers, B.

2006-04-01

The large radar cross section of wind turbine generator (WTG) blades combined with high tip speeds can produce significant Doppler returns when illuminated by a radar. Normally, an air traffic control radar system will filter out large returns from stationary targets, but the Doppler shifts introduced by the WTG blades are interpreted as moving aircraft that can confuse radar operators and compromise safety. A possible solution to this problem is to incorporate an active layer into the structure of the WTG blades that can be used to dynamically modulate the radar cross section (RCS) of the blade return. The active blade can operate in one of two modes: first the blade RCS can be modulated to provide a Doppler return that is outside the detectable range of the radar receiver system so that it is rejected; a second mode of operation is to introduce specific coding onto the Doppler returns so that they may be uniquely identified and rejected. The active layer used in the system consists of a frequency selective surface controlled by semiconductor diodes and is a development of techniques developed for active radar absorbers. Results of theoretical and experimental work using a 10 GHz Doppler radar and scale-model WTG are presented.

Arecibo radar imagery of Mars: The major volcanic provinces

NASA Astrophysics Data System (ADS)

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

2012-08-01

We present Earth-based radar images of Mars obtained with the upgraded Arecibo S-band (λ = 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

Thermally switchable meta-material absorber involving vanadium dioxide semiconductor-metal transition for thermo photovoltaic conversion

NASA Astrophysics Data System (ADS)

Bendelala, Fathi; Cheknane, Ali; Hilal, Hikmat S.

2018-01-01

A new switchable absorber design using meta-materials for thermo photovoltaic applications is proposed here. Conventional absorbents are normally non-adjustable with narrow band-widths and polarization-dependence. The present study describes an alternative infrared absorber structure with tunable characteristics. The absorber is based on VO2 which exhibits transition from semiconductor to metallic conductor by thermal effect. With this design, the results show that wide-band absorption can be achieved. The absorption bandwidth can be improved from 15.94 to 36.75 THz. With 40.42% relative shift in the peak frequency, a maximum absorption efficiency of 99% can be achieved. This structure design is polarization-independent of normal incident radiations, and may accommodate radiations from wide oblique angles. These new features make the new thermally adjustable absorber potentially useful in thermo-photovoltaic conversion devices.

Lightweight and efficient microwave absorbing materials based on walnut shell-derived nano-porous carbon.

PubMed

Qiu, Xu; Wang, Lixi; Zhu, Hongli; Guan, Yongkang; Zhang, Qitu

2017-06-08

Lightweight microwave absorbing materials have drawn tremendous attention. Herein, nano-porous biomass carbon materials have been prepared by carbonization with a subsequent potassium hydroxide activation of walnut shells and the microwave absorption properties have also been investigated. The obtained samples have large specific surface areas with numerous micropores and nanopores. The sample activated at 600 °C with a specific surface area of 736.2 m 2 g -1 exhibits the most enhanced microwave absorption performance. It has the maximum reflection loss of -42.4 dB at 8.88 GHz and the effective absorption bandwidth (reflection loss below -10 dB) is 1.76 GHz (from 8.08 GHz to 9.84 GHz), corresponding to a thickness of 2 mm. Additionally, the effective absorption bandwidth can reach 2.24 GHz (from 10.48 GHz to 12.72 GHz) when the absorber thickness is 1.5 mm. Three-dimensional porous architecture, interfacial polarization relaxation loss, and the dipolar relaxation loss make a great contribution to the excellent microwave absorption performance. In contrast, the non-activated sample with lower specific surface area (435.3 m 2 g -1 ) has poor microwave absorption performance due to a poor dielectric loss capacity. This comparison highlights the role of micropores and nanopores in improving the dielectric loss property of porous carbon materials. To sum up, porous biomass carbon has great potential to become lightweight microwave absorbers. Moreover, KOH is an efficient activation agent in the fabrication of carbonaceous materials.

Wind turbine generators with active radar signature control blades

NASA Astrophysics Data System (ADS)

Tennant, Alan; Chambers, Barry

2004-07-01

The large radar cross section of wind turbine generator (WTG) blades combined with high tip speeds can produce significant Doppler returns when illuminated by a radar. Normally, an air traffic control radar system will filter out large returns from stationary targets, however the Doppler shifts introduced by the WTG are interpreted as moving aircraft that can confuse radar operators and compromise safety. A possible solution to this problem that we are investigating is to incorporate an active layer into the structure of the WTG blades that can be used to dynamically modulate the RCS of the blade return. The active blade can operate in one of two modes: firstly the blade RCS can be modulated to provide a Doppler return that is outside the detectable range of the radar receiver system so that it is rejected: a second mode of operation is to introduce specific coding on to the Doppler returns so that they may be uniquely identified and rejected. The active layer used in the system consists of a frequency selective surface controlled by semiconductor diodes and is a development of techniques that we have developed for active radar absorbers. Results of experimental work using a 10GHz Doppler radar and scale model WTG with active Doppler imparting blades are presented.

Study on the millimeter-wave scale absorber based on the Salisbury screen

NASA Astrophysics Data System (ADS)

Yuan, Liming; Dai, Fei; Xu, Yonggang; Zhang, Yuan

2018-03-01

In order to solve the problem on the millimeter-wave scale absorber, the Salisbury screen absorber is employed and designed based on the RL. By optimizing parameters including the sheet resistance of the surface resistive layer, the permittivity and the thickness of the grounded dielectric layer, the RL of the Salisbury screen absorber could be identical with that of the theoretical scale absorber. An example is given to verify the effectiveness of the method, where the Salisbury screen absorber is designed by the proposed method and compared with the theoretical scale absorber. Meanwhile, plate models and tri-corner reflector (TCR) models are constructed according to the designed result and their scattering properties are simulated by FEKO. Results reveal that the deviation between the designed Salisbury screen absorber and the theoretical scale absorber falls within the tolerance of radar Cross section (RCS) measurement. The work in this paper has important theoretical and practical significance in electromagnetic measurement of large scale ratio.

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

PubMed

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

2013-11-28

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

Hematite from Natural Iron Stones as Microwave Absorbing Material on X-Band Frequency Ranges

NASA Astrophysics Data System (ADS)

Zainuri, Mochamad

2017-05-01

This study has been investigated the effect of hematite as microwave absorbing materials (RAM) on X-Band frequency ranges. Hematite was succesfully processed by coprecipitation method and calcined at 500 °C for 5 hour. It was synthesized from natural iron stones from Tanah Laut, South Kalimantan, Indonesia. The products were characterized by X-ray diffraxtion (XRD), conductivity measurement, Vibrating Sample Magnetometer (VSM), and Vector Network Analyzer (VNA). The result was shown that hematite has conductivity value on (2.5-3).10-7 S/cm and be included as dielectric materials. The hysterisis curve was shown that hematite was a super paramagnetic materials. The product was mixed on paint with procentage 10% of total weight and coated on steel grade AH36 with spray methods. Then, the maximum of reflection loss on x - band’s frequency range (8,2-12,4) GHz was -7 dB on frequency of 10.5 GHz. It mean that almost 50% electromagnetic energy was absorbed by hematite.

Absorptive coding metasurface for further radar cross section reduction

NASA Astrophysics Data System (ADS)

Sui, Sai; Ma, Hua; Wang, Jiafu; Pang, Yongqiang; Feng, Mingde; Xu, Zhuo; Qu, Shaobo

2018-02-01

Lossless coding metasurfaces and metamaterial absorbers have been widely used for radar cross section (RCS) reduction and stealth applications, which merely depend on redirecting electromagnetic wave energy into various oblique angles or absorbing electromagnetic energy, respectively. Here, an absorptive coding metasurface capable of both the flexible manipulation of backward scattering and further wideband bistatic RCS reduction is proposed. The original idea is carried out by utilizing absorptive elements, such as metamaterial absorbers, to establish a coding metasurface. We establish an analytical connection between an arbitrary absorptive coding metasurface arrangement of both the amplitude and phase and its far-field pattern. Then, as an example, an absorptive coding metasurface is demonstrated as a nonperiodic metamaterial absorber, which indicates an expected better performance of RCS reduction than the traditional lossless coding metasurface and periodic metamaterial-absorber. Both theoretical analysis and full-wave simulation results show good accordance with the experiment.

Magneto-Radar Hidden Metal Detector

DOEpatents

McEwan, Thomas E.

2005-07-05

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.

Solar radiation absorbing material

DOEpatents

Googin, John M.; Schmitt, Charles R.; Schreyer, James M.; Whitehead, Harlan D.

1977-01-01

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.

Boron-copper neutron absorbing material and method of preparation

DOEpatents

Wiencek, Thomas C.; Domagala, Robert F.; Thresh, Henry

1991-01-01

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

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

NASA Technical Reports Server (NTRS)

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

1982-01-01

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

Composite neutron absorbing coatings for nuclear criticality control

DOEpatents

Wright, Richard N.; Swank, W. David; Mizia, Ronald E.

2005-07-19

Thermal neutron absorbing composite coating materials and methods of applying such coating materials to spent nuclear fuel storage systems are provided. A composite neutron absorbing coating applied to a substrate surface includes a neutron absorbing layer overlying at least a portion of the substrate surface, and a corrosion resistant top coat layer overlying at least a portion of the neutron absorbing layer. An optional bond coat layer can be formed on the substrate surface prior to forming the neutron absorbing layer. The neutron absorbing layer can include a neutron absorbing material, such as gadolinium oxide or gadolinium phosphate, dispersed in a metal alloy matrix. The coating layers may be formed by a plasma spray process or a high velocity oxygen fuel process.

Hybrid waste filler filled bio-polymer foam composites for sound absorbent materials

NASA Astrophysics Data System (ADS)

Rus, Anika Zafiah M.; Azahari, M. Shafiq M.; Kormin, Shaharuddin; Soon, Leong Bong; Zaliran, M. Taufiq; Ahraz Sadrina M. F., L.

2017-09-01

Sound absorption materials are one of the major requirements in many industries with regards to the sound insulation developed should be efficient to reduce sound. This is also important to contribute in economically ways of producing sound absorbing materials which is cheaper and user friendly. Thus, in this research, the sound absorbent properties of bio-polymer foam filled with hybrid fillers of wood dust and waste tire rubber has been investigated. Waste cooking oil from crisp industries was converted into bio-monomer, filled with different proportion ratio of fillers and fabricated into bio-polymer foam composite. Two fabrication methods is applied which is the Close Mold Method (CMM) and Open Mold Method (OMM). A total of four bio-polymer foam composite samples were produce for each method used. The percentage of hybrid fillers; mixture of wood dust and waste tire rubber of 2.5 %, 5.0%, 7.5% and 10% weight to weight ration with bio-monomer. The sound absorption of the bio-polymer foam composites samples were tested by using the impedance tube test according to the ASTM E-1050 and Scanning Electron Microscope to determine the morphology and porosity of the samples. The sound absorption coefficient (α) at different frequency range revealed that the polymer foam of 10.0 % hybrid fillers shows highest α of 0.963. The highest hybrid filler loading contributing to smallest pore sizes but highest interconnected pores. This also revealed that when highly porous material is exposed to incident sound waves, the air molecules at the surface of the material and within the pores of the material are forced to vibrate and loses some of their original energy. This is concluded that the suitability of bio-polymer foam filled with hybrid fillers to be used in acoustic application of automotive components such as dashboards, door panels, cushion and etc.

Semitransparent Volcanic Materials on Radar Images of Venus

NASA Astrophysics Data System (ADS)

Bondarenko, N. V.; Kreslavsky, M. A.

2011-03-01

Possible observational effects due to semitransparent lava flows on Venus were analyzed and illustrated. Numerous examples show that interpretation of Magellan radar images requires consideration of subsurface scattering.

Millimeter wave radars raise weapon IQ

NASA Astrophysics Data System (ADS)

Lerner, E. J.

1985-02-01

The problems encountered by laser and IR homing devices for guided munitions may be tractable with warhead-mounted mm-wave radars. Operating at about 100 GHz and having several kilometers range, mm-wave radars see through darkness, fog, rain and smoke. The radar must be coupled with an analyzer that discerns moving and stationary targets and higher priority targets. The target lock-on can include shut-off of the transmitter and reception of naturally-generated mm-waves bouncing off the target when in the terminal phase of the flight. Monopulse transmitters have simplified the radar design, although mass production of finline small radar units has yet to be accomplished, particularly in combining GaAs, ferrites and other materials on one monolithic chip.

Synthesis and characterization of barium hexaferrite with manganese (Mn) doping material as anti-radar

NASA Astrophysics Data System (ADS)

Susilawati, Doyan, Aris; Khalilurrahman

2017-01-01

Have been successfully synthesized barium powder doping Manganese hexaferrite with the expected potential as anti-radar material. Synthesis was done by using the co-precipitation method, the variation of the variable x concentrations used were 0; 0.2; 0.4; and 0.6 and calcined at temperatures of 400, 600 and 800°C. Characterization powders of hexaferrite have used XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), LCR (inductance, capacitance, and resistance) meter, and VSM (Vibrating Sample Magnetometer). The higher the concentration and temperature of calcinations given affect the color of the powder. The test results using XRD indicates that it has formed barium hexaferrite phase with a hexagonal crystal structure. Tests using SEM showed that all the constituent elements barium powder hexaferrite by doping Manganese powders have been spread evenly. XRD test results were confirmed by a test using a TEM showing the crystal structure and the powder was sized nano particles. The results from the LCR meter showed that the barium powder hexaferrite by doping Manganese that has been synthesized classified in semiconductor materials. The result from VSM showed that the value of coercivity magnetic powder doped barium hexaferrite Manganese is smaller when compared with barium hexaferrite without doping and belong to the soft magnetic. Based on the results of the synthesis and characterization, we can conclude that the barium powder heksaferrite by doping Manganese potential as a material anti-radar.

Absorbent product and articles made therefrom

NASA Technical Reports Server (NTRS)

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

1982-01-01

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

Lunar and Venusian radar bright rings

NASA Technical Reports Server (NTRS)

Thompson, T. W.; Saunders, R. S.; Weissman, D. E.

1986-01-01

Twenty-one lunar craters have radar bright ring appearances which are analogous to eleven complete ring features in the earth-based 12.5 cm observations of Venus. Radar ring diameters and widths for the lunar and Venusian features overlap for sizes from 45 to 100 km. Radar bright areas for the lunar craters are associated with the slopes of the inner and outer rim walls, while level crater floors and level ejecta fields beyond the raised portion of the rim have average radar backscatter. It is proposed that the radar bright areas of the Venusian rings are also associated with the slopes on the rims of craters. The lunar craters have evolved to radar bright rings via mass wasting of crater rim walls and via post-impact flooding of crater floors. Aeolian deposits of fine-grained material on Venusian crater floors may produce radar scattering effects similar to lunar crater floor flooding. These Venusian aeolian deposits may preferentially cover blocky crater floors producing a radar bright ring appearance. It is proposed that the Venusian features with complete bright ring appearances and sizes less than 100 km are impact craters. They have the same sizes as lunar craters and could have evolved to radar bright rings via analogous surface processes.

Comparison of Image Processing Techniques using Random Noise Radar

DTIC Science & Technology

2014-03-27

detection UWB ultra-wideband EM electromagnetic CW continuous wave RCS radar cross section RFI radio frequency interference FFT fast Fourier transform...several factors including radar cross section (RCS), orientation, and material makeup. A single monostatic radar at some position collects only range and...Chapter 2 is to provide the theory behind noise radar and SAR imaging. Section 2.1 presents the basic concepts in transmitting and receiving random

Covert situational awareness with handheld ultrawideband short-pulse radar

NASA Astrophysics Data System (ADS)

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

2001-08-01

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

Thin and Broadband Two-Layer Microwave Absorber in 4-12 GHz with Developed Flaky Cobalt Material

NASA Astrophysics Data System (ADS)

Gill, Neeraj; Singh, Jaydeep; Puthucheri, Smitha; Singh, Dharmendra

2018-03-01

Microwave absorbing materials (MAMs) in the frequency range of 2.0-18.0 GHz are essential for the stealth and communication applications. Researchers came up with effective MAMs for the higher frequency regions, i.e., 8.0-18.0 GHz, while absorbers with comparable properties in the lower frequency band are still not in the limelight. Designing a MAM for the lower frequency range is a critical task. It is known that the factors governing the absorption in this frequency predominantly depend on the permeability and conductivity of the material, whereas the shape anisotropy of the particles can initiate different absorption mechanisms like multiple internal reflections, phase cancellations, surface charge polarization and enhanced conductivity that can promote the microwave absorption towards lower frequencies. But the material alone may not serve the purpose of getting broad absorption bandwidth. With the effective use of advanced electromagnetic technique like multi-layering this problem may be solved. Therefore, in this paper, a material with shape anisotropy (cobalt flakes with high shape anisotropy) has been prepared and a two-layer structure is developed which gives the absorption bandwidth in 4.17-12.05 GHz at a coating thickness of 2.66 mm.

Thin and Broadband Two-Layer Microwave Absorber in 4-12 GHz with Developed Flaky Cobalt Material

NASA Astrophysics Data System (ADS)

Gill, Neeraj; Singh, Jaydeep; Puthucheri, Smitha; Singh, Dharmendra

2018-05-01

Microwave absorbing materials (MAMs) in the frequency range of 2.0-18.0 GHz are essential for the stealth and communication applications. Researchers came up with effective MAMs for the higher frequency regions, i.e., 8.0-18.0 GHz, while absorbers with comparable properties in the lower frequency band are still not in the limelight. Designing a MAM for the lower frequency range is a critical task. It is known that the factors governing the absorption in this frequency predominantly depend on the permeability and conductivity of the material, whereas the shape anisotropy of the particles can initiate different absorption mechanisms like multiple internal reflections, phase cancellations, surface charge polarization and enhanced conductivity that can promote the microwave absorption towards lower frequencies. But the material alone may not serve the purpose of getting broad absorption bandwidth. With the effective use of advanced electromagnetic technique like multi-layering this problem may be solved. Therefore, in this paper, a material with shape anisotropy (cobalt flakes with high shape anisotropy) has been prepared and a two-layer structure is developed which gives the absorption bandwidth in 4.17-12.05 GHz at a coating thickness of 2.66 mm.

Wall characterization for through-the-wall radar applications

NASA Astrophysics Data System (ADS)

Greneker, Gene; Rausch, E. O.

2008-04-01

There has been continuing interest in the penetration of multilayer building materials, such as wood walls with air gaps and concrete hollow core block, using through-the-wall (TTW) radar systems. TTW operational techniques and signal propagation paths vary depending on how the TTW system is intended to be operated. For example, the operator of a TTW radar may be required to place the radar against the intervening wall of interest while collecting data. Other operational doctrines allow the radar to be operated in a stand-off mode from the wall. The stand-off distances can vary from feet to hundreds of feet, depending on the type of radar being used. When a signal is propagated through a multilayer wall with air gaps between the material and the wall construction uses materials of radically different dielectric constants, attenuation may not be the only effect that the probing signal experiences passing through the wall. This paper presents measurements of a hollow core concrete block wall and the measurement of a standard wall constructed of siding and wallboard. Both types of walls are typically found in most U.S. homes. These limited measurements demonstrate that the type of wall being penetrated by a wideband signal can modify the probing signal.

Automation of an RCS (Radar Cross Section) Measurement System and Its Application to Investigate the Electromagnetic Scattering from Scale Model Aircraft Canopies

DTIC Science & Technology

1989-12-01

8217 -E ep IP 760 7v rag-2-t 7 -vet ca vo - a~ .:cz : 112 !] 10 Star-, requency i- -in.- -,,z. 200 :1h too t rouencv, i ax. 210 N T iarizat~on i2:)15. 220... 10 2-3 Pyramidal Radar Absorbing Material (RAM) ... . 11 2-4 Hardware configuration .... ............. 13 2-5 Point source model for phase variation...two plates ....... 51 4- 10 Gated RCS of 4 inch circular flat plate a) time doi. ain and b) frequency response . . . . 52 5-1 Measurement test matrix

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

PubMed

Olah, Z

1979-11-01

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.

Carbon nanotube scaffolds with controlled porosity as electromagnetic absorbing materials in the gigahertz range

NASA Astrophysics Data System (ADS)

González, M.; Crespo, M.; Baselga, J.; Pozuelo, J.

2016-05-01

Control of the microscopic structure of CNT nanocomposites allows modulation of the electromagnetic shielding in the gigahertz range. The porosity of CNT scaffolds has been controlled by two freezing protocols and a subsequent lyophilization step: fast freezing in liquid nitrogen and slow freezing at -20 °C. Mercury porosimetry shows that slowly frozen specimens present a more open pore size (100-150 μm) with a narrow distribution whereas specimens frozen rapidly show a smaller pore size and a heterogeneous distribution. 3D-scaffolds containing 3, 4, 6 and 7% CNT were infiltrated with epoxy and specimens with 2, 5 and 8 mm thicknesses were characterized in the GHz range. Samples with the highest pore size and porosity presented the lowest reflected power (about 30%) and the highest absorbed power (about 70%), which allows considering them as electromagnetic radiation absorbing materials.Control of the microscopic structure of CNT nanocomposites allows modulation of the electromagnetic shielding in the gigahertz range. The porosity of CNT scaffolds has been controlled by two freezing protocols and a subsequent lyophilization step: fast freezing in liquid nitrogen and slow freezing at -20 °C. Mercury porosimetry shows that slowly frozen specimens present a more open pore size (100-150 μm) with a narrow distribution whereas specimens frozen rapidly show a smaller pore size and a heterogeneous distribution. 3D-scaffolds containing 3, 4, 6 and 7% CNT were infiltrated with epoxy and specimens with 2, 5 and 8 mm thicknesses were characterized in the GHz range. Samples with the highest pore size and porosity presented the lowest reflected power (about 30%) and the highest absorbed power (about 70%), which allows considering them as electromagnetic radiation absorbing materials. Electronic supplementary information (ESI) available: Scheme of hydrogenated derivative of diglycidyl ether of bisphenol-A (HDGEBA) and m-xylylenediamine; X-ray diffractograms of pristine CNT

Container and method for absorbing and reducing hydrogen concentration

DOEpatents

Wicks, George G.; Lee, Myung W.; Heung, Leung K.

2001-01-01

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

Experimental Investigation into the Radar Anomalies on the Surface of Venus

NASA Technical Reports Server (NTRS)

Kohler, E.; Gavin, P.; Chevrier, V.; Johnson, Natasha M.

2012-01-01

Radar mapping of thc surface of Venus shows areas of high reflectivity (low emissivity) in the Venusian highlands at altitudes between 2.5-4.75 kilometers. The origin of the radar anomalies found in the Venusian highlands remains unclear. Most explanations of the potential causes for these radar anomalies come from theoretical work. Previous studies suggest increased surface roughness or materials with higher dielectric constants as well as surface atmospheric interactions. Several possible candidates of high-dielectric materials are tellurium) ferroelectric materials, and lead or bismuth sulfides. While previous studies have been influential in determining possible sources for the Venus anomalies, only a very few hypotheses have been verified via experimentation. This work intends to experimentally constrain the source of the radar anomalies on Venus. This study proposes to investigate four possible materials that could potentially cause the high reflectivities on the surface of Venus and tests their behavior under simulated Venusian conditions.

Dual-band wide-angle metamaterial perfect absorber based on the combination of localized surface plasmon resonance and Helmholtz resonance.

PubMed

Zhang, Changlei; Huang, Cheng; Pu, Mingbo; Song, Jiakun; Zhao, Zeyu; Wu, Xiaoyu; Luo, Xiangang

2017-07-18

In this article, a dual-band wide-angle metamaterial perfect absorber is proposed to achieve absorption at the wavelength where laser radar operates. It is composed of gold ring array and a Helmholtz resonance cavity spaced by a Si dielectric layer. Numerical simulation results reveal that the designed absorber displays two absorption peaks at the target wavelength of 10.6 μm and 1.064 μm with the large frequency ratio and near-unity absorptivity under the normal incidence. The wide-angle absorbing property and the polarization-insensitive feature are also demonstrated. Localized surface plasmons resonance and Helmholtz resonance are introduced to analyze and interpret the absorbing mechanism. The designed perfect absorber can be developed for potential applications in infrared stealth field.

Carbon nanotube scaffolds with controlled porosity as electromagnetic absorbing materials in the gigahertz range.

PubMed

González, M; Crespo, M; Baselga, J; Pozuelo, J

2016-05-19

Control of the microscopic structure of CNT nanocomposites allows modulation of the electromagnetic shielding in the gigahertz range. The porosity of CNT scaffolds has been controlled by two freezing protocols and a subsequent lyophilization step: fast freezing in liquid nitrogen and slow freezing at -20 °C. Mercury porosimetry shows that slowly frozen specimens present a more open pore size (100-150 μm) with a narrow distribution whereas specimens frozen rapidly show a smaller pore size and a heterogeneous distribution. 3D-scaffolds containing 3, 4, 6 and 7% CNT were infiltrated with epoxy and specimens with 2, 5 and 8 mm thicknesses were characterized in the GHz range. Samples with the highest pore size and porosity presented the lowest reflected power (about 30%) and the highest absorbed power (about 70%), which allows considering them as electromagnetic radiation absorbing materials.

Low temperature selective absorber research

NASA Astrophysics Data System (ADS)

Herzenberg, S. A.; Silberglitt, R.

1982-04-01

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

Multiobjective Topology Optimization of Energy Absorbing Materials

DTIC Science & Technology

2015-08-01

absorbing liner for equestrian helmets. Part I: layered foam liner . Mater Des 30(9):3405–3413 Sethian J, Wiegmann A (2000) Structural boundary design via...Army Research Laboratory Wildman RA, Weile DS (2007) Geometry reconstruction of conduct- ing cylinders using genetic programming. IEEE Trans Antennas

Intrascleral outflow after deep sclerectomy with absorbable and non-absorbable implants in the rabbit eye.

PubMed

Kałużny, Jakub J; Grzanka, Dariusz; Wiśniewska, Halina; Niewińska, Alicja; Kałużny, Bartłomiej J; Grzanka, Alina

2012-10-01

The purpose of the study is an analysis of intrascleral drainage vessels formed in rabbits' eyes after non-penetrating deep sclerectomy (NPDS) with absorbable and non-absorbable implants, and comparison to eyes in which surgery was performed without implanted material. NPDS was carried out in 12 rabbits, with implantation of non-absorbable methacrylic hydrogel (N=10 eyes) or absorbable cross-linked sodium hyaluronate (N=6 eyes), or without any implant (N=8 eyes). All the animals were euthanized 1 year after surgery. Twenty-one eyeballs were prepared for light microscopy and 3 were prepared for transmission electron microscope (TEM) analysis. Aqueous humour pathways were stained with ferritin in 6 eyeballs. By light microscopy, small vessels adjacent to the areas of scarring were the most common abnormality. Vessel density was significantly higher in operated sclera compared to normal, healthy tissue, regardless of the type of implant used. The average vessel densities were 2.18±1.48 vessels/mm2 in non-implanted sclera, 2.34±1.69 vessels/mm2 in eyes with absorbable implants, and 3.64±1.78 vessels/mm2 in eyes with non-absorbable implants. Analysis of iron distribution in ferritin-injected eyes showed a positive reaction inside new aqueous draining vessels in all groups. TEM analysis showed that the ultrastructure of new vessels matched the features of the small veins. Aqueous outflow after NPDS can be achieved through the newly formed network of small intrascleral veins. Use of non-absorbable implants significantly increases vessel density in the sclera adjacent to implanted material compared to eyes in which absorbable implants or no implants were used.

A Two-Step Absorber Deposition Approach To Overcome Shunt Losses in Thin-Film Solar Cells: Using Tin Sulfide as a Proof-of-Concept Material System

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

Steinmann, Vera; Chakraborty, Rupak; Rekemeyer, Paul H.

2016-08-31

As novel absorber materials are developed and screened for their photovoltaic (PV) properties, the challenge remains to reproducibly test promising candidates for high-performing PV devices. Many early-stage devices are prone to device shunting due to pinholes in the absorber layer, producing 'false-negative' results. Here, we demonstrate a device engineering solution toward a robust device architecture, using a two-step absorber deposition approach. We use tin sulfide (SnS) as a test absorber material. The SnS bulk is processed at high temperature (400 degrees C) to stimulate grain growth, followed by a much thinner, low-temperature (200 degrees C) absorber deposition. At a lowermore » process temperature, the thin absorber overlayer contains significantly smaller, densely packed grains, which are likely to provide a continuous coating and fill pinholes in the underlying absorber bulk. We compare this two-step approach to the more standard approach of using a semi-insulating buffer layer directly on top of the annealed absorber bulk, and we demonstrate a more than 3.5x superior shunt resistance Rsh with smaller standard error ..sigma..Rsh. Electron-beam-induced current (EBIC) measurements indicate a lower density of pinholes in the SnS absorber bulk when using the two-step absorber deposition approach. We correlate those findings to improvements in the device performance and device performance reproducibility.« less

Competitive light absorbers in photoactive dental resin-based materials.

PubMed

Hadis, Mohammed A; Shortall, Adrian C; Palin, William M

2012-08-01

The absorbance profile of photoinitiators prior to, during and following polymerization of light curable resin-based materials will have a significant effect on the cure and color properties of the final material. So-called "colorless" photoinitiators are used in some light-activated resin-based composite restorative materials to lessen the yellowing effect of camphoroquinone (CQ) in order to improve the esthetic quality of dental restorations. This work characterizes absorption properties of commonly used photoinitiators, an acylphosphine oxide (TPO) and CQ, and assesses their influence on material discoloration. Dimethacrylate resin formulations contained low (0.0134 mol/dm(3)), intermediate (0.0405 mol/dm(3)) or high (0.0678 mol/dm(3)) concentrations of the photoinitiators and the inhibitor, butylated hydroxytoluene (BHT) at 0, 0.1 or 0.2% by mass. Disc shaped specimens (n = 3) of each resin were polymerized for 60s using a halogen light curing unit. Dynamic measurements of photoinitiator absorption, polymer conversion and reaction temperature were performed. A spectrophotometer was used to measure the color change before and after cure. GLM three-way analysis of variance revealed significant differences (p<0.001), where photoinitiator concentration (df = 2; F = 618.83)>photoinitiator type (df = 1; F = 176.12)>% BHT (df = 2, F = 13.17). BHT concentration affected the rate of polymerization and produced lower conversion in some of the CQ-based resins. Significant differences between photoinitiator type and concentrations were seen in color (where TPO resins became yellower and camphoroquinone resins became less yellow upon irradiation). Reaction temperature, kinetics and conversion also differed significantly for both initiators (p<0.001). Despite TPO-based resins producing a visually perceptible color change upon polymerization, the color change was significantly less than that produced with CQ-based resins. Although some photoinitiators such as TPO may be a

Coordinated Radar Resource Management for Networked Phased Array Radars

DTIC Science & Technology

2014-12-01

Coordinated radar resource management for networked phased array radars Peter W. Moo and Zhen Ding Radar Sensing & Exploitation Section Defence...15] P.W. Moo . Scheduling for multifunction radar via two-slope benefit functions. Radar, Sonar Navigation, IET, 5(8):884 –894, Oct. 2011. [16] M.I

Reduction of radar cross-section of a wind turbine

DOEpatents

McDonald, Jacob Jeremiah; Brock, Billy C.; Clem, Paul G.; Loui, Hung; Allen, Steven E.

2016-08-02

The various technologies presented herein relate to formation of a wind turbine blade having a reduced radar signature in comparison with a turbine blade fabricated using conventional techniques. Various techniques and materials are presented to facilitate reduction in radar signature of a wind turbine blade, where such techniques and materials are amenable for incorporation into existing manufacturing techniques without degradation in mechanical or physical performance of the blade or major alteration of the blade profile.

Diesel NO{sub x} reduction by plasma-regenerated absorbent beds

DOEpatents

Wallman, P.H.; Vogtlin, G.E.

1998-02-10

Reduction of NO{sub x} from diesel engine exhaust by use of plasma-regenerated absorbent beds is described. This involves a process for the reduction of NO{sub x} and particulates from diesel engines by first absorbing NO{sub x} onto a solid absorbent bed that simultaneously acts as a physical trap for the particulate matter, and second regenerating said solid absorbent by pulsed plasma decomposition of absorbed NO{sub x} followed by air oxidation of trapped particulate matter. The absorbent bed may utilize all metal oxides, but the capacity and the kinetics of absorption and desorption vary between different materials, and thus the composition of the absorbent bed is preferably a material which enables the combination of NO{sub x} absorption capability with catalytic activity for oxidation of hydrocarbons. Thus, naturally occurring or synthetically prepared materials may be utilized, particularly those having NO{sub x} absorption properties up to temperatures around 400 C which is in the area of diesel engine exhaust temperatures. 1 fig.

Compressive Sensing for Radar and Radar Sensor Networks

DTIC Science & Technology

2013-12-02

Zero Correlation Zone Sequence Pair Sets for MIMO Radar Inspired by recent advances in MIMO radar, we apply orthogonal phase coded waveforms to MIMO ...radar system in order to gain better range resolution and target direction finding performance [2]. We provide and investigate a generalized MIMO radar...ZCZ) sequence-Pair Set (ZCZPS). We also study the MIMO radar ambiguity function of the system using phase coded waveforms, based on which we analyze

High-resolution three-dimensional imaging radar

NASA Technical Reports Server (NTRS)

Cooper, Ken B. (Inventor); Chattopadhyay, Goutam (Inventor); Siegel, Peter H. (Inventor); Dengler, Robert J. (Inventor); Schlecht, Erich T. (Inventor); Mehdi, Imran (Inventor); Skalare, Anders J. (Inventor)

2010-01-01

A three-dimensional imaging radar operating at high frequency e.g., 670 GHz, is disclosed. The active target illumination inherent in radar solves the problem of low signal power and narrow-band detection by using submillimeter heterodyne mixer receivers. A submillimeter imaging radar may use low phase-noise synthesizers and a fast chirper to generate a frequency-modulated continuous-wave (FMCW) waveform. Three-dimensional images are generated through range information derived for each pixel scanned over a target. A peak finding algorithm may be used in processing for each pixel to differentiate material layers of the target. Improved focusing is achieved through a compensation signal sampled from a point source calibration target and applied to received signals from active targets prior to FFT-based range compression to extract and display high-resolution target images. Such an imaging radar has particular application in detecting concealed weapons or contraband.

Ultra wideband ground penetrating radar imaging of heterogeneous solids

DOEpatents

Warhus, J.P.; Mast, J.E.

1998-11-10

A non-invasive imaging system for analyzing engineered structures comprises pairs of ultra wideband radar transmitters and receivers in a linear array that are connected to a timing mechanism that allows a radar echo sample to be taken at a variety of delay times for each radar pulse transmission. The radar transmitters and receivers are coupled to a position determining system that provides the x,y position on a surface for each group of samples measured for a volume from the surface. The radar transmitter and receivers are moved about the surface, e.g., attached to the bumper of a truck, to collect such groups of measurements from a variety of x,y positions. Return signal amplitudes represent the relative reflectivity of objects within the volume and the delay in receiving each signal echo represents the depth at which the object lays in the volume and the propagation speeds of the intervening material layers. Successively deeper z-planes are backward propagated from one layer to the next with an adjustment for variations in the expected propagation velocities of the material layers that lie between adjacent z-planes. 11 figs.

Ultra wideband ground penetrating radar imaging of heterogeneous solids

DOEpatents

Warhus, John P.; Mast, Jeffrey E.

1998-01-01

A non-invasive imaging system for analyzing engineered structures comprises pairs of ultra wideband radar transmitters and receivers in a linear array that are connected to a timing mechanism that allows a radar echo sample to be taken at a variety of delay times for each radar pulse transmission. The radar transmitters and receivers are coupled to a position determining system that provides the x,y position on a surface for each group of samples measured for a volume from the surface. The radar transmitter and receivers are moved about the surface, e.g., attached to the bumper of a truck, to collect such groups of measurements from a variety of x,y positions. Return signal amplitudes represent the relative reflectivity of objects within the volume and the delay in receiving each signal echo represents the depth at which the object lays in the volume and the propagation speeds of the intervening material layers. Successively deeper z-planes are backward propagated from one layer to the next with an adjustment for variations in the expected propagation velocities of the material layers that lie between adjacent z-planes.

Nickel Nanoparticle Encapsulated in Few-Layer Nitrogen-Doped Graphene Supported by Nitrogen-Doped Graphite Sheets as a High-Performance Electromagnetic Wave Absorbing Material.

PubMed

Yuan, Haoran; Yan, Feng; Li, Chunyan; Zhu, Chunling; Zhang, Xitian; Chen, Yujin

2018-01-10

Herein we develop a facile strategy for fabricating nickel particle encapsulated in few-layer nitrogen-doped graphene supported by graphite carbon sheets as a high-performance electromagnetic wave (EMW) absorbing material. The obtained material exhibits sheetlike morphology with a lateral length ranging from a hundred nanometers to 2 μm and a thickness of about 23 nm. Nickel nanoparticles with a diameter of approximately 20 nm were encapsulated in about six layers of nitrogen-doped graphene. As applied for electromagnetic absorbing material, the heteronanostructures exhibit excellent electromagnetic wave absorption property, comparable to most EMW absorbing materials previously reported. Typically, the effective absorption bandwidth (the frequency region falls within the reflection loss below -10 dB) is up to 8.5 GHz at the thicknesses of 3.0 mm for the heteronanostructures with the optimized Ni content. Furthermore, two processes, carbonization at a high temperature and subsequent treatment in hot acid solution, were involved in the preparation of the heteronanostructures, and thus, mass production was achieved easily, facilitating their practical applications.

Development of a Continuum Damage Mechanics Material Model of a Graphite-Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.; Littell, Justin D.

2017-01-01

This paper describes the development of input properties for a continuum damage mechanics based material model, Mat 58, within LS-DYNA(Registered Trademark) to simulate the response of a graphite-Kevlar(Registered Trademark) hybrid plain weave fabric. A limited set of material characterization tests were performed on the hybrid graphite-Kevlar(Registered Trademark) fabric. Simple finite element models were executed in LS-DYNA(Registered Trademark) to simulate the material characterization tests and to verify the Mat 58 material model. Once verified, the Mat 58 model was used in finite element models of two composite energy absorbers: a conical-shaped design, designated the "conusoid," fabricated of four layers of hybrid graphite-Kevlar(Registered Trademark) fabric; and, a sinusoidal-shaped foam sandwich design, designated the "sinusoid," fabricated of the same hybrid fabric face sheets with a foam core. Dynamic crush tests were performed on components of the two energy absorbers, which were designed to limit average vertical accelerations to 25- to 40-g, to minimize peak crush loads, and to generate relatively long crush stroke values under dynamic loading conditions. Finite element models of the two energy absorbers utilized the Mat 58 model that had been verified through material characterization testing. Excellent predictions of the dynamic crushing response were obtained.

Structural geologic interpretations from radar imagery

USGS Publications Warehouse

Reeves, Robert G.

1969-01-01

Certain structural geologic features may be more readily recognized on sidelooking airborne radar (SLAR) images than on conventional aerial photographs, other remote sensor imagery, or by ground observations. SLAR systems look obliquely to one or both sides and their images resemble aerial photographs taken at low sun angle with the sun directly behind the camera. They differ from air photos in geometry, resolution, and information content. Radar operates at much lower frequencies than the human eye, camera, or infrared sensors, and thus "sees" differently. The lower frequency enables it to penetrate most clouds and some precipitation, haze, dust, and some vegetation. Radar provides its own illumination, which can be closely controlled in intensity and frequency. It is narrow band, or essentially monochromatic. Low relief and subdued features are accentuated when viewed from the proper direction. Runs over the same area in significantly different directions (more than 45° from each other), show that images taken in one direction may emphasize features that are not emphasized on those taken in the other direction; optimum direction is determined by those features which need to be emphasized for study purposes. Lineaments interpreted as faults stand out on radar imagery of central and western Nevada; folded sedimentary rocks cut by faults can be clearly seen on radar imagery of northern Alabama. In these areas, certain structural and stratigraphic features are more pronounced on radar images than on conventional photographs; thus radar imagery materially aids structural interpretation.

Digital Alloy Absorber for Photodetectors

NASA Technical Reports Server (NTRS)

Hill, Cory J. (Inventor); Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor)

2016-01-01

In order to increase the spectral response range and improve the mobility of the photo-generated carriers (e.g. in an nBn photodetector), a digital alloy absorber may be employed by embedding one (or fraction thereof) to several monolayers of a semiconductor material (insert layers) periodically into a different host semiconductor material of the absorber layer. The semiconductor material of the insert layer and the host semiconductor materials may have lattice constants that are substantially mismatched. For example, this may performed by periodically embedding monolayers of InSb into an InAsSb host as the absorption region to extend the cutoff wavelength of InAsSb photodetectors, such as InAsSb based nBn devices. The described technique allows for simultaneous control of alloy composition and net strain, which are both key parameters for the photodetector operation.

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

Innovative Anti Crash Absorber for a Crashworthy Landing Gear

NASA Astrophysics Data System (ADS)

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

2014-06-01

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

Translatory shock absorber for attitude sensors

NASA Technical Reports Server (NTRS)

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

1976-01-01

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

A wideband absorber for television studios

NASA Astrophysics Data System (ADS)

Baird, M. D. M.

The acoustic treatment in BBC television has taken various forms to date, all of which have been relatively expensive, some of which provide inadequate absorption. An investigation has been conducted into the possibilities of producing a new type of wideband absorber which would be more economic, also taking installation time into account, than earlier designs. This Report describes the absorption coefficient measurements made on various combinations of materials, from which a wideband sound absorber has been developed. The absorber works efficiently between 50 Hz and 10 kHz, is simple and easy to construct using readily available materials, and is fire resistant. The design lends itself, if necessary, to on-site fine tuning, and savings in the region of 50 percent can be achieved in terms of cost and space with respect to previous designs.

Optimized multilayered wideband absorbers with graded fractal FSS

NASA Astrophysics Data System (ADS)

Vinoy, K. J.; Jose, K. A.; Varadan, Vijay K.; Varadan, Vasundara V.

2001-08-01

Various approaches have been followed for the reduction of radar cross section (RCS), especially of aircraft and missiles. In this paper we present the use of multiple layers of FSS-like fractal geometries printed on dielectric substrates for the same goal. The experimental results shown here indicate 15 dB reduction in the reflection of a flat surface, by the use of this configuration with low loss dielectrics. An extensive optimization scheme is required for extending the angle coverage as well as the bandwidth of the absorber. A brief investigation of such a scheme involving genetic algorithm for this purpose is also presented here.

Evaluation of absorbent materials for use as ad hoc dry decontaminants during mass casualty incidents as part of the UK’s Initial Operational Response (IOR)

PubMed Central

Kassouf, Nick; Syed, Sara; Larner, Joanne; Amlôt, Richard

2017-01-01

The UK’s Initial Operational Response (IOR) is a revised process for the medical management of mass casualties potentially contaminated with hazardous materials. A critical element of the IOR is the introduction of immediate, on-scene disrobing and decontamination of casualties to limit the adverse health effects of exposure. Ad hoc cleansing of the skin with dry absorbent materials has previously been identified as a potential means of facilitating emergency decontamination. The purpose of this study was to evaluate the in vitro oil and water absorbency of a range of materials commonly found in the domestic and clinical environments and to determine the effectiveness of a small, but representative selection of such materials in skin decontamination, using an established ex vivo model. Five contaminants were used in the study: methyl salicylate, parathion, diethyl malonate, phorate and potassium cyanide. In vitro measurements of water and oil absorbency did not correlate with ex vivo measurements of skin decontamination. When measured ex vivo, dry decontamination was consistently more effective than a standard wet decontamination method (“rinse-wipe-rinse”) for removing liquid contaminants. However, dry decontamination was ineffective against particulate contamination. Collectively, these data confirm that absorbent materials such as wound dressings and tissue paper provide an effective, generic capability for emergency removal of liquid contaminants from the skin surface, but that wet decontamination should be used for non-liquid contaminants. PMID:28152053

Near surface bulk density estimates of NEAs from radar observations and permittivity measurements of powdered geologic material

NASA Astrophysics Data System (ADS)

Hickson, Dylan; Boivin, Alexandre; Daly, Michael G.; Ghent, Rebecca; Nolan, Michael C.; Tait, Kimberly; Cunje, Alister; Tsai, Chun An

2018-05-01

The variations in near-surface properties and regolith structure of asteroids are currently not well constrained by remote sensing techniques. Radar is a useful tool for such determinations of Near-Earth Asteroids (NEAs) as the power of the reflected signal from the surface is dependent on the bulk density, ρbd, and dielectric permittivity. In this study, high precision complex permittivity measurements of powdered aluminum oxide and dunite samples are used to characterize the change in the real part of the permittivity with the bulk density of the sample. In this work, we use silica aerogel for the first time to increase the void space in the samples (and decrease the bulk density) without significantly altering the electrical properties. We fit various mixing equations to the experimental results. The Looyenga-Landau-Lifshitz mixing formula has the best fit and the Lichtenecker mixing formula, which is typically used to approximate planetary regolith, does not model the results well. We find that the Looyenga-Landau-Lifshitz formula adequately matches Lunar regolith permittivity measurements, and we incorporate it into an existing model for obtaining asteroid regolith bulk density from radar returns which is then used to estimate the bulk density in the near surface of NEA's (101955) Bennu and (25143) Itokawa. Constraints on the material properties appropriate for either asteroid give average estimates of ρbd = 1.27 ± 0.33g/cm3 for Bennu and ρbd = 1.68 ± 0.53g/cm3 for Itokawa. We conclude that our data suggest that the Looyenga-Landau-Lifshitz mixing model, in tandem with an appropriate radar scattering model, is the best method for estimating bulk densities of regoliths from radar observations of airless bodies.

Absorber for microwave investigation in the open space

NASA Astrophysics Data System (ADS)

Kubacki, Roman; Smólski, Bogusław; Głuszewski, Wojciech; Przesmycki, Rafał; Rudyk, Karol

2017-04-01

In some circumstances there is a need to realize the Electromagnetic Compatibility (EMC) investigation not in the specialized anechoic chamber but in the open space. Typical absorbers used in anechoic chamber to reduce the reflected rays from walls and floor, such as ferrite plates and graphite cones, are not suitable in the open space. In the work the investigation of the flexible absorbing material intended to the liquidation of the radiation reflected from the ground has been presented. As an absorbing material the metallic-glass with graphite was elaborated. This material was additionally exposed to the ionizing radiation in the dose of 100 kGy in the radioactive gamma source. The permittivity, permeability as well as the shielding properties have been analyzed.

Highly efficient special sound absorbing solutions

NASA Technical Reports Server (NTRS)

Ionescu, M.; Petre-Lazar, S.

1974-01-01

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

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

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

Space Radar Image of Kennedy Space Center, Florida

NASA Image and Video Library

1999-06-25

This image was produced during radar observations taken by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar as it flew over the Gulf Stream, Florida, and past the Atlantic Ocean on October 7, 1994. The data were produced using the X-band radar frequency. Knowing ahead of time that this region would be included in a regularly scheduled radar pass, the Kennedy Space Center team, who assembled and integrated the SIR-C/X-SAR equipment with the Spacelab pallet system, designed a set of radar reflectors from common construction materials and formed the letters "KSC" on the ground adjacent to the main headquarters building at the entrance to the Cape Canaveral launch facility. The point of light formed by the bright return from these reflectors are visible in the image. Other more diffuse bright spots are reflections from building faces, roofs and other large structures at the Kennedy Space Center complex. This frame covers an area of approximately 6 kilometers by 8 kilometers (4 miles by 5 miles), which was just a small portion of the data taken on this particular pass. http://photojournal.jpl.nasa.gov/catalog/PIA01747

Enhancement mechanism of the additional absorbent on the absorption of the absorbing composite using a type-based mixing rule

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Yuan, Liming; Zhang, Deyuan

2016-04-01

A silicone rubber composite filled with carbonyl iron particles and four different carbonous materials (carbon black, graphite, carbon fiber or multi-walled carbon nanotubes) was prepared using a two-roller mixture. The complex permittivity and permeability were measured using a vector network analyzer at the frequency of 2-18 GHz. Then a type-based mixing rule based on the dielectric absorbent and magnetic absorbent was proposed to reveal the enhancing mechanism on the permittivity and permeability. The enforcement effect lies in the decreased percolation threshold and the changing pending parameter as the carbonous materials were added. The reflection loss (RL) result showed the added carbonous materials enhanced the absorption in the lower frequency range, the RL decrement value being about 2 dB at 4-5 GHz with a thickness of 1 mm. All the added carbonous materials reinforced the shielding effectiveness (SE) of the composites. The maximum increment value of the SE was about 3.23 dB at 0.5 mm and 4.65 dB at 1 mm, respectively. The added carbonous materials could be effective additives for enforcing the absorption and shielding property of the absorbers.

Solar sustained plasma/absorber conceptual design

NASA Technical Reports Server (NTRS)

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

1979-01-01

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

Radar research at The Pennsylvania State University Radar and Communications Laboratory

NASA Astrophysics Data System (ADS)

Narayanan, Ram M.

2017-05-01

The Radar and Communications Laboratory (RCL) at The Pennsylvania State University is at the forefront of radar technology and is engaged in cutting edge research in all aspects of radar, including modeling and simulation studies of novel radar paradigms, design and development of new types of radar architectures, and extensive field measurements in realistic scenarios. This paper summarizes the research at The Pennsylvania State University's Radar and Communications Laboratory and relevant collaborative research with several groups over the past 15 years in the field of radar and related technologies, including communications, radio frequency identification (RFID), and spectrum sensing.

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging

NASA Technical Reports Server (NTRS)

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

2010-01-01

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

Equatorial radar system

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

Novel Ultraviolet Light Absorbing Polymers For Optical Applications

NASA Astrophysics Data System (ADS)

Doddi, Namassivaya; Yamada, Akira; Dunks, Gary B.

1988-07-01

Ultraviolet light absorbing monomers have been developed that can be copolymerized with acrylates. The composition of the resultant stable copolymers can be adjusted to totally block the transmission of light below about 430 nm. Fabrication of lenses from the materials is accomplished by lathe cutting and injection molding procedures. These ultraviolet light absorbing materials are non-mutagenic and non-toxic and are currently being used in intraocular lenses.

Freeze-Dried Carbon Nanotube Aerogels for High-Frequency Absorber Applications.

PubMed

Anoshkin, Ilya V; Campion, James; Lioubtchenko, Dmitri V; Oberhammer, Joachim

2018-06-13

A novel technique for millimeter wave absorber material embedded in a metal waveguide is proposed. The absorber material is a highly porous carbon nanotube (CNT) aerogel prepared by a freeze-drying technique. CNT aerogel structures are shown to be good absorbers with a low reflection coefficient, less than -12 dB at 95 GHz. The reflection coefficient of the novel absorber is 3-4 times lower than that of commercial absorbers with identical geometry. Samples prepared by freeze-drying at -25 °C demonstrate resonance behavior, while those prepared at liquid nitrogen temperature (-196 °C) exhibit a significant decrease in reflection coefficient, with no resonant behavior. CNT absorbers of identical volume based on wet-phase drying preparation show significantly worse performance than the CNT aerogel absorbers prepared by freeze-drying. Treatment of the freeze-dried CNT aerogel with n- and p-dopants (monoethanolamine and iodine vapors, respectively) shows remarkable improvement in the performance of the waveguide embedded absorbers, reducing the reflection coefficient by 2 dB across the band.

Mode trap for absorbing transverse modes of an accelerated electron beam

DOEpatents

Chojnacki, E.P.

1994-05-31

A mode trap to trap and absorb transverse modes formed by a beam in a linear accelerator includes a waveguide having a multiplicity of electrically conductive (preferably copper) irises and rings, each iris and ring including an aperture, and the irises and rings being stacked in a side-by-side, alternating fashion such that the apertures of the irises and rings are concentrically aligned. An absorbing material layer such as a dielectric is embedded in each iris and ring, and this absorbing material layer encircles, but is circumferentially spaced from its respective aperture. Each iris and ring includes a plurality of circumferentially spaced slots around its aperture and extending radially out toward its absorbing material layer. 9 figs.

Mode trap for absorbing transverse modes of an accelerated electron beam

DOEpatents

Chojnacki, Eric P.

1994-01-01

A mode trap to trap and absorb transverse modes formed by a beam in a linear accelerator includes a waveguide having a multiplicity of electrically conductive (preferably copper) irises and rings, each iris and ring including an aperture, and the irises and rings being stacked in a side-by-side, alternating fashion such that the apertures of the irises and rings are concentrically aligned. An absorbing material layer such as a dielectric is embedded in each iris and ring, and this absorbing material layer encircles, but is circumferentially spaced from its respective aperture. Each iris and ring includes a plurality of circumferentially spaced slots around its aperture and extending radially out toward its absorbing material layer.

Failure mechanisms in energy-absorbing composite structures

NASA Astrophysics Data System (ADS)

Johnson, Alastair F.; David, Matthew

2010-11-01

Quasi-static tests are described for determination of the energy-absorption properties of composite crash energy-absorbing segment elements under axial loads. Detailed computer tomography scans of failed specimens were used to identify local compression crush failure mechanisms at the crush front. These mechanisms are important for selecting composite materials for energy-absorbing structures, such as helicopter and aircraft sub-floors. Finite element models of the failure processes are described that could be the basis for materials selection and future design procedures for crashworthy structures.

A black body absorber from vertically aligned single-walled carbon nanotubes

PubMed Central

Mizuno, Kohei; Ishii, Juntaro; Kishida, Hideo; Hayamizu, Yuhei; Yasuda, Satoshi; Futaba, Don N.; Yumura, Motoo; Hata, Kenji

2009-01-01

Among all known materials, we found that a forest of vertically aligned single-walled carbon nanotubes behaves most similarly to a black body, a theoretical material that absorbs all incident light. A requirement for an object to behave as a black body is to perfectly absorb light of all wavelengths. This important feature has not been observed for real materials because materials intrinsically have specific absorption bands because of their structure and composition. We found a material that can absorb light almost perfectly across a very wide spectral range (0.2–200 μm). We attribute this black body behavior to stem from the sparseness and imperfect alignment of the vertical single-walled carbon nanotubes. PMID:19339498

Radar stage uncertainty

USGS Publications Warehouse

Fulford, J.M.; Davies, W.J.

2005-01-01

The U.S. Geological Survey is investigating the performance of radars used for stage (or water-level) measurement. This paper presents a comparison of estimated uncertainties and data for radar water-level measurements with float, bubbler, and wire weight water-level measurements. The radar sensor was also temperature-tested in a laboratory. The uncertainty estimates indicate that radar measurements are more accurate than uncorrected pressure sensors at higher water stages, but are less accurate than pressure sensors at low stages. Field data at two sites indicate that radar sensors may have a small negative bias. Comparison of field radar measurements with wire weight measurements found that the radar tends to measure slightly lower values as stage increases. Copyright ASCE 2005.

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

NASA Astrophysics Data System (ADS)

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

2010-08-01

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.

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

SHUTTLE IMAGING RADAR: PHYSICAL CONTROLS ON SIGNAL PENETRATION AND SUBSURFACE SCATTERING IN THE EASTERN SAHARA.

USGS Publications Warehouse

Schaber, Gerald G.; McCauley, John F.; Breed, Carol S.; Olhoeft, Gary R.

1986-01-01

It is found that the Shuttle Imaging Radar A (SIR-A) signal penetration and subsurface backscatter within the upper meter or so of the sediment blanket in the Eastern Sahara of southern Egypt and northern Sudan are enhanced both by radar sensor parameters and by the physical and chemical characteristics of eolian and alluvial materials. The near-surface stratigraphy, the electrical properties of materials, and the types of radar interfaces found to be responsible for different classes of SIR-A tonal response are summarized. The dominant factors related to efficient microwave signal penetration into the sediment blanket include 1) favorable distribution of particle sizes, 2) extremely low moisture content and 3) reduced geometric scattering at the SIR-A frequency (1. 3 GHz). The depth of signal penetration that results in a recorded backscatter, called radar imaging depth, was documented in the field to be a maximum of 1. 5 m, or 0. 25 times the calculated skin depth, for the sediment blanket. The radar imaging depth is estimated to be between 2 and 3 m for active sand dune materials.

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

USGS Publications Warehouse

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

2005-01-01

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

Direct detection of the Yarkovsky effect by radar ranging to ateroid 6489 Golevka

NASA Technical Reports Server (NTRS)

Chesley, S. R.; Ostro, S. J.; Vokrouhlicky, D.; Capek, D.; Giorgini, J. D.; Nolan, M. C.; Margot, J. L.; Hine, A. A.; Benner, L. A. M.; Chamberlin, A. B.

2003-01-01

Radar ranging from Arecibo, Puerto Rico, to the 0.5-kilometer near-Earth asteroid 6489 Golevka unambiguously reveals a small nongravitational acceleration caused by the anisotropic thermal emission of absorbed sunlight. The magnitude of this perturbation, known as the Yarkovsky effect, is a function of the asteroid's mass and surface thermal characteristics. Direct detection of the Yarkovsky effect on asteroids will help constrain their physical properties, such as bulk density, and refine their orbital paths.

Debris Flux Comparisons From The Goldstone Radar, Haystack Radar, and Hax Radar Prior, During, and After the Last Solar Maximum

NASA Technical Reports Server (NTRS)

Stokely, C. L.; Stansbery, E. G.; Goldstein, R. M.

2006-01-01

The continual monitoring of low Earth orbit (LEO) debris environment using highly sensitive radars is essential for an accurate characterization of these dynamic populations. Debris populations are continually evolving since there are new debris sources, previously unrecognized debris sources, and debris loss mechanisms that are dependent on the dynamic space environment. Such radar data are used to supplement, update, and validate existing orbital debris models. NASA has been utilizing radar observations of the debris environment for over a decade from three complementary radars: the NASA JPL Goldstone radar, the MIT Lincoln Laboratory (MIT/LL) Long Range Imaging Radar (known as the Haystack radar), and the MIT/LL Haystack Auxiliary radar (HAX). All of these systems are highly sensitive radars that operate in a fixed staring mode to statistically sample orbital debris in the LEO environment. Each of these radars is ideally suited to measure debris within a specific size region. The Goldstone radar generally observes objects with sizes from 2 mm to 1 cm. The Haystack radar generally measures from 5 mm to several meters. The HAX radar generally measures from 2 cm to several meters. These overlapping size regions allow a continuous measurement of cumulative debris flux versus diameter from 2 mm to several meters for a given altitude window. This is demonstrated for all three radars by comparing the debris flux versus diameter over 200 km altitude windows for 3 nonconsecutive years from 1998 through 2003. These years correspond to periods before, during, and after the peak of the last solar cycle. Comparing the year to year flux from Haystack for each of these altitude regions indicate statistically significant changes in subsets of the debris populations. Potential causes of these changes are discussed. These analysis results include error bars that represent statistical sampling errors, and are detailed in this paper.

Planetary radar studies

NASA Technical Reports Server (NTRS)

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

1981-01-01

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

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

NASA Technical Reports Server (NTRS)

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

1990-01-01

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

High-volume use of self-cementing spray dry absorber material for structural applications

NASA Astrophysics Data System (ADS)

Riley, Charles E.

Spray dry absorber (SDA) material, or spray dryer ash, is a byproduct of energy generation by coal combustion and sulfur emissions controls. Like any resource, it ought to be used to its fullest potential offsetting as many of the negative environmental impacts of coal combustion as possible throughout its lifecycle. Its cementitious and pozzolanic properties suggest it be used to augment or replace another energy and emissions intensive product: Portland cement. There is excellent potential for spray dryer ash to be used beneficially in structural applications, which will offset CO2 emissions due to Portland cement production, divert landfill waste by further utilizing a plentiful coal combustion by-product, and create more durable and sustainable structures. The research into beneficial use applications for SDA material is relatively undeveloped and the material is highly underutilized. This dissertation explored a specific self-cementing spray dryer ash for use as a binder in structural materials. Strength and stiffness properties of hydrated spray dryer ash mortars were improved by chemical activation with Portland cement and reinforcement with polymer fibers from automobile tire recycling. Portland cement at additions of five percent of the cementitious material was found to function effectively as an activating agent for spray dryer ash and had a significant impact on the hardened properties. The recycled polymer fibers improved the ductility and toughness of the material in all cases and increased the compressive strength of weak matrix materials like the pure hydrated ash. The resulting hardened materials exhibited useful properties that were sufficient to suggest that they be used in structural applications such as concrete, masonry block, or as a hydraulic cement binder. While the long-term performance characteristics remain to be investigated, from an embodied-energy and carbon emissions standpoint the material investigated here is far superior to

Simulation of a weather radar display for over-water airborne radar approaches

NASA Technical Reports Server (NTRS)

Clary, G. R.

1983-01-01

Airborne radar approach (ARA) concepts are being investigated as a part of NASA's Rotorcraft All-Weather Operations Research Program on advanced guidance and navigation methods. This research is being conducted using both piloted simulations and flight test evaluations. For the piloted simulations, a mathematical model of the airborne radar was developed for over-water ARAs to offshore platforms. This simulated flight scenario requires radar simulation of point targets, such as oil rigs and ships, distributed sea clutter, and transponder beacon replies. Radar theory, weather radar characteristics, and empirical data derived from in-flight radar photographs are combined to model a civil weather/mapping radar typical of those used in offshore rotorcraft operations. The resulting radar simulation is realistic and provides the needed simulation capability for ongoing ARA research.

Planetary radar studies. [radar mapping of the Moon and radar signatures of lunar and Venus craters

NASA Technical Reports Server (NTRS)

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

1981-01-01

Progress made in studying the evolution of Venusian craters and the evolution of infrared and radar signatures of lunar crater interiors is reported. Comparison of radar images of craters on Venus and the Moon present evidence for a steady state Venus crater population. Successful observations at the Arecibo Observatory yielded good data on five nights when data for a mix of inner and limb areas were acquired. Lunar craters with radar bright ejects are discussed. An overview of infrared radar crater catalogs in the data base is included.

Apollo experience report: Lunar module landing radar and rendezvous radar

NASA Technical Reports Server (NTRS)

Rozas, P.; Cunningham, A. R.

1972-01-01

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

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

Planetary Radar

NASA Technical Reports Server (NTRS)

Neish, Catherine D.; Carter, Lynn M.

2015-01-01

This chapter describes the principles of planetary radar, and the primary scientific discoveries that have been made using this technique. The chapter starts by describing the different types of radar systems and how they are used to acquire images and accurate topography of planetary surfaces and probe their subsurface structure. It then explains how these products can be used to understand the properties of the target being investigated. Several examples of discoveries made with planetary radar are then summarized, covering solar system objects from Mercury to Saturn. Finally, opportunities for future discoveries in planetary radar are outlined and discussed.

Radar orthogonality and radar length in Finsler and metric spacetime geometry

NASA Astrophysics Data System (ADS)

Pfeifer, Christian

2014-09-01

The radar experiment connects the geometry of spacetime with an observers measurement of spatial length. We investigate the radar experiment on Finsler spacetimes which leads to a general definition of radar orthogonality and radar length. The directions radar orthogonal to an observer form the spatial equal time surface an observer experiences and the radar length is the physical length the observer associates to spatial objects. We demonstrate these concepts on a forth order polynomial Finsler spacetime geometry which may emerge from area metric or premetric linear electrodynamics or in quantum gravity phenomenology. In an explicit generalization of Minkowski spacetime geometry we derive the deviation from the Euclidean spatial length measure in an observers rest frame explicitly.

Neutron Absorbing Alloys

DOEpatents

Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

2004-05-04

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.

The instrumental principles of MST radars and incoherent scatter radars and the configuration of radar system hardware

NASA Technical Reports Server (NTRS)

Roettger, Juergen

1989-01-01

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 transmitter/receiver system is described. Transmit/receive duplexers, transmitters, receivers, and quadrature detectors are explained. The radar controller, integrator, decoder and correlator design as well as the data transfer and the control and monitoring by the host computer are delineated. Typical operation parameters of some well-known radars are summarized.

2D Homologous Perovskites as Light-Absorbing Materials for Solar Cell Applications.

PubMed

Cao, Duyen H; Stoumpos, Constantinos C; Farha, Omar K; Hupp, Joseph T; Kanatzidis, Mercouri G

2015-06-24

We report on the fabrication and properties of the semiconducting 2D (CH3(CH2)3NH3)2(CH3NH3)(n-1)Pb(n)I(3n+1) (n = 1, 2, 3, and 4) perovskite thin films. The band gaps of the series decrease with increasing n values, from 2.24 eV (CH3(CH2)3NH3)2PbI4 (n = 1) to 1.52 eV CH3NH3PbI3 (n = ∞). The compounds exhibit strong light absorption in the visible region, accompanied by strong photoluminescence at room temperature, rendering them promising light absorbers for photovoltaic applications. Moreover, we find that thin films of the semi-2D perovskites display an ultrahigh surface coverage as a result of the unusual film self-assembly that orients the [Pb(n)I(3n+1)](-) layers perpendicular to the substrates. We have successfully implemented this 2D perovskite family in solid-state solar cells, and obtained an initial power conversion efficiency of 4.02%, featuring an open-circuit voltage (V(oc)) of 929 mV and a short-circuit current density (J(sc)) of 9.42 mA/cm(2) from the n = 3 compound. This result is even more encouraging considering that the device retains its performance after long exposure to a high-humidity environment. Overall, the homologous 2D halide perovskites define a promising class of stable and efficient light-absorbing materials for solid-state photovoltaics and other applications.

Removing interfering clutter associated with radar pulses that an airborne radar receives from a radar transponder

DOEpatents

Ormesher, Richard C.; Axline, Robert M.

2008-12-02

Interfering clutter in radar pulses received by an airborne radar system from a radar transponder can be suppressed by developing a representation of the incoming echo-voltage time-series that permits the clutter associated with predetermined parts of the time-series to be estimated. These estimates can be used to estimate and suppress the clutter associated with other parts of the time-series.

Recommendation on Transition from Primary/Secondary Radar to Secondary- Only Radar Capability

DTIC Science & Technology

1994-10-01

Radar Beacon Performance Monitor RCIU Remote Control Interface Unit RCL Remote Communications Link R E&D Research, Engineering and Development RML Radar...rate. 3.1.2.5 Maintenance The current LRRs have limited remote maintenance monitoring (RMM) capabilities via the Remote Control Interface Unit ( RCIU ...1, -2 and FPS-20 radars required an upgrade of some of the radar subsystems, namely the RCIU to respond as an RMS and the CD to interface with radar

Apollo couch energy absorbers

NASA Technical Reports Server (NTRS)

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

1972-01-01

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

Reconfigurable L-Band Radar

NASA Technical Reports Server (NTRS)

Rincon, Rafael F.

2008-01-01

The reconfigurable L-Band radar is an ongoing development at NASA/GSFC that exploits the capability inherently in phased array radar systems with a state-of-the-art data acquisition and real-time processor in order to enable multi-mode measurement techniques in a single radar architecture. The development leverages on the L-Band Imaging Scatterometer, a radar system designed for the development and testing of new radar techniques; and the custom-built DBSAR processor, a highly reconfigurable, high speed data acquisition and processing system. The radar modes currently implemented include scatterometer, synthetic aperture radar, and altimetry; and plans to add new modes such as radiometry and bi-static GNSS signals are being formulated. This development is aimed at enhancing the radar remote sensing capabilities for airborne and spaceborne applications in support of Earth Science and planetary exploration This paper describes the design of the radar and processor systems, explains the operational modes, and discusses preliminary measurements and future plans.

Unglazed transpired solar collector having a low thermal-conductance absorber

DOEpatents

Christensen, Craig B.; Kutscher, Charles F.; Gawlik, Keith M.

1997-01-01

An unglazed transpired solar collector using solar radiation to heat incoming air for distribution, comprising an unglazed absorber formed of low thermal-conductance material having a front surface for receiving the solar radiation and openings in the unglazed absorber for passage of the incoming air such that the incoming air is heated as it passes towards the front surface of the absorber and the heated air passes through the openings in the absorber for distribution.

Social Radar

DTIC Science & Technology

2012-01-01

RTA HFM-201/RSM PAPER 3 - 1 © 2012 The MITRE Corporation. All Rights Reserved. Social Radar Barry Costa and John Boiney MITRE Corporation...defenders require an integrated set of capabilities that we refer to as a “ social radar.” Such a system would support strategic- to operational-level...situation awareness, alerting, course of action analysis, and measures of effectiveness for each action undertaken. Success of a social radar

Thermally enhanced signal strength and SNR improvement of photoacoustic radar module

PubMed Central

Wang, Wei; Mandelis, Andreas

2014-01-01

A thermally enhanced method for improving photoacoustic imaging depth and signal-to-noise (SNR) ratio is presented in this paper. Experimental results showed that the maximum imaging depth increased by 20% through raising the temperature of absorbing biotissues (ex-vivo beef muscle) uniformly from 37 to 43°C, and the SNR was increased by 8%. The parameters making up the Gruneisen constant were investigated experimentally and theoretically. The studies showed that the Gruneisen constant of biotissues increases with temperature, and the results were found to be consistent with the photoacousitc radar theory. PMID:25136501

The proposed flatland radar

NASA Technical Reports Server (NTRS)

Green, J. L.; Gage, K. S.; Vanzandt, T. E.; Nastrom, G. D.

1986-01-01

A flexible very high frequency (VHF) stratosphere-troposphere (ST) radar configured for meteorological research is to be constructed near Urbana, Illinois. Measurement of small vertical velocities associated with synoptic-scale meteorology can be performed. A large Doppler microwave radar (CHILL) is located a few km from the site of the proposed ST radar. Since the microwave radar can measure the location and velocity of hydrometeors and the VHF ST radar can measure clear (or cloudy) air velocities, simultaneous observations by these two radars of stratiform or convective weather systems would provide valuable meteorological information.

Surface properties and surficial deposits on Venus: New results from Magellan radar altimeter data analysis

NASA Astrophysics Data System (ADS)

Bondarenko, Nataliya V.; Kreslavsky, Mikhail A.

2018-07-01

Microwave remote sensing data acquired with Magellan Venus orbiter are the main source of information about the surface of the planet. We analyze variability of the backscattering function (dependence of radar cross-section on incidence angle) for steep incidence angles 0.25°-4.75° in the 75°N-55°S latitude zone with data from the Magellan radar altimeter at 12.6 cm wavelength. We show that all variability of the backscattering function can be described by three parameters, describing (1) surface reflectivity, (2) relative proportion of horizontal facets, and (3) general roughness. Analysis of maps of these parameters revealed that surficial deposits, for example, microdune fields, are abundant on Venus even in places, where they are not readily seen in the synthetic aperture radar images. Properties of surficial deposits rather than original volcanic flow roughness define the shape of the backscattering function on the majority of regional plains. A large radar-dark flow in Bereghinia Planitia has anomalously high proportion of horizontal facets, which is consistent with it being formed by a relatively recent plain-forming volcanic episode. Some crater-associated radar-dark diffuse features and splotches are also characterized by increased proportion of horizontal faces, which indicate the presence of mantles deposited from fluidized granular material. The backscattering functions of the anomalous radar-bright material of mountaintops are more consistent with the strong internal scattering hypothesis rather than the exotic surficial material hypothesis. Obtained maps can be useful for planning future lander missions to sites with access to surface material with known provenance.

Mapping small elevation changes over large areas - Differential radar interferometry

NASA Technical Reports Server (NTRS)

Gabriel, Andrew K.; Goldstein, Richard M.; Zebker, Howard A.

1989-01-01

A technique is described, based on synthetic aperture radar (SAR) interferometry, which uses SAR images for measuring very small (1 cm or less) surface motions with good resolution (10 m) over swaths of up to 50 km. The method was applied to a Seasat data set of an imaging site in Imperial Valley, California, where motion effects were observed that were identified with movements due to the expansion of water-absorbing clays. The technique can be used for accurate measurements of many geophysical phenomena, including swelling and buckling in fault zones, residual displacements from seismic events, and prevolcanic swelling.

Unglazed transpired solar collector having a low thermal-conductance absorber

DOEpatents

Christensen, C.B.; Kutscher, C.F.; Gawlik, K.M.

1997-12-02

An unglazed transpired solar collector using solar radiation to heat incoming air for distribution, comprises an unglazed absorber formed of low thermal-conductance material having a front surface for receiving the solar radiation and openings in the unglazed absorber for passage of the incoming air such that the incoming air is heated as it passes towards the front surface of the absorber and the heated air passes through the openings in the absorber for distribution. 3 figs.

Automatic position calculating imaging radar with low-cost synthetic aperture sensor for imaging layered media

DOEpatents

Mast, Jeffrey E.

1998-01-01

An imaging system for analyzing structures comprises a radar transmitter and receiver connected to a timing mechanism that allows a radar echo sample to be taken at a variety of delay times for each radar pulse transmission. The radar transmitter and receiver are coupled to a position determining system that provides the x,y position on a surface for each group of samples measured for a volume from the surface. The radar transmitter and receiver are moved about the surface to collect such groups of measurements from a variety of x,y positions. Return signal amplitudes represent the relative reflectivity of objects within the volume and the delay in receiving each signal echo represents the depth at which the object lays in the volume and the propagation speeds of the intervening material layers. Successively deeper z-planes are backward propagated from one layer to the next with an adjustment for variations in the expected propagation velocities of the material layers that lie between adjacent z-planes.

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

Fly eye radar or micro-radar sensor technology

NASA Astrophysics Data System (ADS)

Molchanov, Pavlo; Asmolova, Olga

2014-05-01

To compensate for its eye's inability to point its eye at a target, the fly's eye consists of multiple angularly spaced sensors giving the fly the wide-area visual coverage it needs to detect and avoid the threats around him. Based on a similar concept a revolutionary new micro-radar sensor technology is proposed for detecting and tracking ground and/or airborne low profile low altitude targets in harsh urban environments. Distributed along a border or around a protected object (military facility and buildings, camp, stadium) small size, low power unattended radar sensors can be used for target detection and tracking, threat warning, pre-shot sniper protection and provides effective support for homeland security. In addition it can provide 3D recognition and targets classification due to its use of five orders more pulses than any scanning radar to each space point, by using few points of view, diversity signals and intelligent processing. The application of an array of directional antennas eliminates the need for a mechanical scanning antenna or phase processor. It radically decreases radar size and increases bearing accuracy several folds. The proposed micro-radar sensors can be easy connected to one or several operators by point-to-point invisible protected communication. The directional antennas have higher gain, can be multi-frequency and connected to a multi-functional network. Fly eye micro-radars are inexpensive, can be expendable and will reduce cost of defense.

Shock-absorbing effect of shoe insert materials commonly used in management of lower extremity disorders.

PubMed

Shiba, N; Kitaoka, H B; Cahalan, T D; Chao, E Y

1995-01-01

The efficacy of 3 shock-absorbing materials was compared by determining impact characteristics with a drop test method and also by testing the effect of each material when used as a shoe insert in 16 asymptomatic subjects. Peak vertical ground reaction force (F1, F2, F3) and temporal force factors (T1, T2, T3) were obtained with a force plate at a high-frequency sampling rate. Impact force, impact time, impact slope, and impact energy were determined. A standard weight was dropped from 3 heights on each material covering the force plate while reduction of peak force was compared. Impact force was attenuated most effectively by Insert 3 (polymeric foam rubber) and averaged 11% less than that in shoes without inserts. Impact time was increased for all 3 inserts. Impact slope and impact energy were reduced significantly in Insert 3. There was a significant difference in peak vertical force F1 for all 3 inserts, in vertical force F2 for Insert 2 (viscoelastic polymeric material), and in vertical force F3 for Insert 2. Drop-test studies showed that at all ball heights, the highest mean peak force was observed consistently in Insert 2.

Lunar Crater Ejecta: Physical Properties Revealed by Radar and Thermal Infrared Observations

NASA Technical Reports Server (NTRS)

Ghent, R. R.; Carter, L. M.; Bandfield, J. L.; Udovicic, C. J. Tai; Campbell, B. A.

2015-01-01

We investigate the physical properties, and changes through time, of lunar impact ejecta using radar and thermal infrared data. We use data from two instruments on the Lunar Reconnaissance Orbiter (LRO) - the Diviner thermal radiometer and the Miniature Radio Frequency (Mini-RF) radar instrument - together with Earth-based radar observations. We use this multiwavelength intercomparison to constrain block sizes and to distinguish surface from buried rocks in proximal ejecta deposits. We find that radar-detectable rocks buried within the upper meter of regolith can remain undisturbed by surface processes such as micrometeorite bombardment for greater than 3 Gyr. We also investigate the thermophysical properties of radar-dark haloes, comprised of fine-grained, rock-poor ejecta distal to the blocky proximal ejecta. Using Diviner data, we confirm that the halo material is depleted in surface rocks, but show that it is otherwise thermophysically indistinct from background regolith. We also find that radar-dark haloes, like the blocky ejecta, remain visible in radar observations for craters with ages greater than 3 Ga, indicating that regolith overturn processes cannot replenish their block populations on that timescale.

Mars Express MARSIS Radar: A Prediction of the Effect of Overlying Ice on Detecting Polar Basal Lakes and Inter-Glacial Aquifers

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Plaut, J. J.; Gurnett, D. A.; Picardi, G.

2004-01-01

The penetration of the MARSIS radar signal into the polar ice mass is modeled to determine the capability of the instrument to locate sub-glacial aquifers. As a ground penetrating radar, the orbiting MARSIS transmits a signal greater than 1 W between 1-5 MHz. In this work we will investigate the effect of ice conductive losses on the radar-detection of subsurface aquifers. Based on wave propagation analysis, it is found that for a bulk ice conductivity below 10-5 S/m, conductive losses in the medium are not significant. However, if the bulk ice conductivity is relatively large (greater than 10-5 S/m), the reflected signal from any deep aquifer will be absorbed as it propagates in the lossy ice medium limiting the probing depth.

Orbital SAR and Ground-Penetrating Radar for Mars: Complementary Tools in the Search for Water

NASA Technical Reports Server (NTRS)

Campbell, B. A.; Grant, J. A.

2000-01-01

The physical structure and compositional variability of the upper martian crust is poorly understood. Optical and infrared measurements probe at most the top few cm of the surface layer and indicate the presence of layered volcanics and sediments, but it is likely that permafrost, hydrothermal deposits, and transient liquid water pockets occur at depths of meters to kilometers within the crust. An orbital synthetic aperture radar (SAR) can provide constraints on surface roughness, the depth of fine-grained aeolian or volcanic deposits, and the presence of strongly absorbing near-surface deposits such as carbonates. This information is crucial to the successful landing and operation of any rover designed to search for subsurface water. A rover-based ground-penetrating radar (GPR) can reveal layering in the upper crust, the presence of erosional or other subsurface horizons, depth to a permafrost layer, and direct detection of near-surface transient liquid water. We detail here the radar design parameters likely to provide the best information for Mars, based on experience with SAR and GPR in analogous terrestrial or planetary environments.

Solar Radar Experiments

DTIC Science & Technology

1998-01-01

communications satellites and electric power grids. RELATED PROJECTS Studies with the HAARP radar facility being constructed in Alaska are conducted with...on wave-plasma interactions and also are assessing the possible use of HAARP as a solar radar. REFERENCES James, J. C., Radar studies of the sun, in

Tunable broadband near-infrared absorber based on ultrathin phase-change material

NASA Astrophysics Data System (ADS)

Hu, Er-Tao; Gu, Tong; Guo, Shuai; Zang, Kai-Yan; Tu, Hua-Tian; Yu, Ke-Han; Wei, Wei; Zheng, Yu-Xiang; Wang, Song-You; Zhang, Rong-Jun; Lee, Young-Pak; Chen, Liang-Yao

2017-11-01

In this work, a tunable broadband near-infrared light absorber was designed and fabricated with a simple and lithography free approach by introducing an ultrathin phase-change material Ge2Sb2Te5 (GST) layer into the metal-dielectric multilayered film structure with the structure parameters as that: SiO2 (72.7 nm)/Ge2Sb2Te5 (6.0 nm)/SiO2 (70.2 nm)/Cu (>100.0 nm). The film structure exhibits a modulation depth of ∼72.6% and an extinction ratio of ∼8.8 dB at the wavelength of 1410 nm. The high light absorption (95%) of the proposed film structure at the wavelength of 450 nm in both of the amorphous and crystalline phase of GST, indicates that the intensity of the reflectance in the infrared region can be rapidly tuned by the blue laser pulses. The proposed planar layered film structure with layer thickness as the only controllable parameter and large reflectivity tuning range shows the potential for practical applications in near-infrared light modulation and absorption.

A simulation study of detection of weapon of mass destruction based on radar

NASA Astrophysics Data System (ADS)

Sharifahmadian, E.; Choi, Y.; Latifi, S.

2013-05-01

Typical systems used for detection of Weapon of Mass Destruction (WMD) are based on sensing objects using gamma rays or neutrons. Nonetheless, depending on environmental conditions, current methods for detecting fissile materials have limited distance of effectiveness. Moreover, radiation related to gamma- rays can be easily shielded. Here, detecting concealed WMD from a distance is simulated and studied based on radar, especially WideBand (WB) technology. The WB-based method capitalizes on the fact that electromagnetic waves penetrate through different materials at different rates. While low-frequency waves can pass through objects more easily, high-frequency waves have a higher rate of absorption by objects, making the object recognition easier. Measuring the penetration depth allows one to identify the sensed material. During simulation, radar waves and propagation area including free space, and objects in the scene are modeled. In fact, each material is modeled as a layer with a certain thickness. At start of simulation, a modeled radar wave is radiated toward the layers. At the receiver side, based on the received signals from every layer, each layer can be identified. When an electromagnetic wave passes through an object, the wave's power will be subject to a certain level of attenuation depending of the object's characteristics. Simulation is performed using radar signals with different frequencies (ranges MHz-GHz) and powers to identify different layers.

Selective solar absorber emittance measurement at elevated temperature

NASA Astrophysics Data System (ADS)

Giraud, Philémon; Braillon, Julien; Raccurt, Olivier

2017-06-01

Durability of solar components for CSP (Concentrated Solar Power Plant) technologies is a key point to lower cost and ensure their large deployment. These technologies concentrated the solar radiation by means of mirrors on a receiver tube where it is collected as thermal energy. The absorbers are submitted to strong environmental constraints and the degradation of their optical properties (emittance and solar absorbance) have a direct impact on performance. The characterization of a material in such condition is complicated and requires advanced apparatuses, and different measurement methods exist for the determination of the two quantities of relevance regarding an absorber, which are its emittance and its solar absorbance. The objective is to develop new optical equipment for measure the emittance of this solar absorber at elevated temperature. In this paper, we present an optical bench developed for emittance measurement on absorbers is conditions of use. Results will be shown, with a discussion of some factors of influence over this measurement and how to control them.

High-resolution Earth-based lunar radar studies: Applications to lunar resource assessment

NASA Technical Reports Server (NTRS)

Stacy, N. J. S.; Campbell, D. B.

1992-01-01

The lunar regolith will most likely be a primary raw material for lunar base construction and resource extraction. High-resolution radar observations of the Moon provide maps of radar backscatter that have intensity variations generally controlled by the local slope, material, and structural properties of the regolith. The properties that can be measured by the radar system include the dielectric constant, density, loss tangent, and wavelength scale roughness. The radar systems currently in operation at several astronomical observatories provide the ability to image the lunar surface at spatial resolutions approaching 30 m at 3.8 cm and 12.6 cm wavelengths and approximately 500 m at 70 cm wavelength. The radar signal penetrates the lunar regolith to a depth of 10-20 wavelengths so the measured backscatter contains contributions from the vacuum-regolith interface and from wavelength-scale heterogeneities in the electrical properties of the subsurface material. The three wavelengths, which are sensitive to different scale structures and scattering volumes, provide complementary information on the regolith properties. Aims of the previous and future observations include (1) analysis of the scattering properties associated with fresh impact craters, impact crater rays, and mantled deposits; (2) analysis of high-incidence-angle observations of the lunar mare to investigate measurement of the regolith dielectric constant and hence porosity; (3) investigation of interferometric techniques using two time-delayed observations of the same site, observations that require a difference in viewing geometry less than 0.05 deg and, hence, fortuitous alignment of the Earth-Moon system when visible from Arecibo Observatory.

Rice straw-wood particle composite for sound absorbing wooden construction materials.

PubMed

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

2003-01-01

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 10, 20, and 30 wt.%. A commercial urea-formaldehyde adhesive was used as the composite binder, to achieve 140-290 psi of bending modulus of rupture (MOR) with 0.4 specific gravity, 700-900 psi of bending MOR with 0.6 specific gravity, and 1400-2900 psi of bending MOR with a 0.8 specific gravity. All of the composite boards were superior to insulation board in strength. Width and length of the rice straw particle did not affect the bending MOR. The composite boards made from a random cutting of rice straw and wood particles were the best and recommended for manufacturing processes. Sound absorption coefficients of the 0.4 and 0.6 specific gravity boards were higher than the other wood-based materials. The recommended properties of the rice straw-wood particle composite boards are described, to absorb noises, preserve the temperature of indoor living spaces, and to be able to partially or completely substitute for wood particleboard and insulation board in wooden constructions.

Space Radar Image of Ubar Optical/Radar

NASA Image and Video Library

1998-04-28

This pair of images from space shows a portion of the southern Empty Quarter of the Arabian Peninsula in the country of Oman. On the left is a radar image of the region around the site of the fabled Lost City of Ubar, discovered in 1992 with the aid of remote sensing data. On the right is an enhanced optical image taken by the shuttle astronauts. Ubar existed from about 2800 BC to about 300 AD. and was a remote desert outpost where caravans were assembled for the transport of frankincense across the desert. The actual site of the fortress of the Lost City of Ubar, currently under excavation, is too small to show in either image. However, tracks leading to the site, and surrounding tracks, show as prominent, but diffuse, reddish streaks in the radar image. Although used in modern times, field investigations show many of these tracks were in use in ancient times as well. Mapping of these tracks on regional remote sensing images provided by the Landsat satellite was a key to recognizing the site as Ubar. The prominent magenta colored area is a region of large sand dunes. The green areas are limestone rocks, which form a rocky desert floor. A major wadi, or dry stream bed, runs across the scene and appears as a white line. The radar images, and ongoing field investigations, will help shed light on an early civilization about which little in known. The radar image was taken by the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) and is centered at 18 degrees North latitude and 53 degrees East longitude. The image covers an area about 50 kilometers by 100 kilometers (31 miles by 62 miles). The colors in the image are assigned to different frequencies and polarizations of the radar as follows: red is L-band, horizontally transmitted, horizontally received; blue is C-band horizontally transmitted, horizontally received; green is L-band horizontally transmitted, vertically received. SIR-C/X-SAR, a joint mission of the German, Italian and the United

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

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

Kesim, Yunus E., E-mail: yunus.kesim@bilkent.edu.tr; Battal, Enes; UNAM-National Nanotechnology Research Center, Bilkent University, Ankara, 06800

2014-07-15

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

Absorbable magnesium-based stent: physiological factors to consider for in vitro degradation assessments

PubMed Central

Wang, Juan; Smith, Christopher E.; Sankar, Jagannathan; Yun, Yeoheung; Huang, Nan

2015-01-01

Absorbable metals have been widely tested in various in vitro settings using cells to evaluate their possible suitability as an implant material. However, there exists a gap between in vivo and in vitro test results for absorbable materials. A lot of traditional in vitro assessments for permanent materials are no longer applicable to absorbable metallic implants. A key step is to identify and test the relevant microenvironment and parameters in test systems, which should be adapted according to the specific application. New test methods are necessary to reduce the difference between in vivo and in vitro test results and provide more accurate information to better understand absorbable metallic implants. In this investigative review, we strive to summarize the latest test methods for characterizing absorbable magnesium-based stent for bioabsorption/biodegradation behavior in the mimicking vascular environments. Also, this article comprehensively discusses the direction of test standardization for absorbable stents to paint a more accurate picture of the in vivo condition around implants to determine the most important parameters and their dynamic interactions. PMID:26816631

Discrete Huygens’ modeling for the characterization of a sound absorbing medium

NASA Astrophysics Data System (ADS)

Chai, L.; Kagawa, Y.

2007-07-01

Based on the equivalence between the wave propagation in the electrical transmission-lines and acoustic tubes, the authors proposed the use of the transmission-line matrix modeling (TLM) for time-domain solution method of the sound field. TLM is known in electromagnetic engineering community, which is equivalent to the discrete Huygens' modeling. The wave propagation is simulated by tracing the sequences of the transmission and scattering of impulses. The theory and the demonstrated examples are presented in the references, in which a sound absorbing field was preliminarily considered to be a medium with simple acoustic resistance independent of frequency and the angle of incidence for the absorbing layer placed on the room wall surface. The present work is concerned with the time-domain response for the characterization of the sound absorbing materials. A lossy component with variable propagation velocity is introduced for sound absorbing materials to facilitate the energy consumption. The frequency characteristics of the absorption coefficient are also considered for the normal, oblique and random incidence. Some numerical demonstrations show that the present modeling provide a reasonable modeling of the homogeneous sound absorbing materials in time domain.

Highly Absorbing Metal Nanolaminates for Bi-Material THz Sensors

DTIC Science & Technology

2011-09-01

NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited HIGHLY ABSORBING...Prescribed by ANSI Std. 239-18 REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is...Government. IRB Protocol number: N/A. 12a. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution is unlimited 12b

41. Perimeter acquisition radar building radar element and coaxial display, ...

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

41. Perimeter acquisition radar building radar element and coaxial display, with drawing of typical antenna section. Drawing, from left to right, shows element, aluminum ground plane, cable connectors and hardware, cable, and back-up ring. Grey area is the concrete wall - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

Cross-hole radar scanning of two vertical, permeable, reactive-iron walls at the Massachusetts Military Reservation, Cape Cod, Massachusetts

USGS Publications Warehouse

Lane, J.W.; Joesten, P.K.; Savoie, J.G.

2001-01-01

A pilot-scale study was conducted by the U.S. Army National Guard (USANG) at the Massachusetts Military Reservation (MMR) on Cape Cod, Massachusetts, to assess the use of a hydraulic-fracturing method to create vertical, permeable walls of zero-valent iron to passively remediate ground water contaminated with chlorinated solvents. The study was conducted near the source area of the Chemical Spill-10 (CS-10) plume, a plume containing chlorinated solvents that underlies the MMR. Ground-water contamination near the source area extends from about 24 m (meters) to 35 m below land surface. The USANG designed two reactive-iron walls to be 12 m long and positioned 24 to 37 m below land surface to intersect and remediate part of the CS-10 plume.Because iron, as an electrical conductor, absorbs electromagnetic energy, the US Geological Survey used a cross-hole common-depth, radar scanning method to assess the continuity and to estimate the lateral and vertical extent of the two reactive-iron walls. The cross-hole radar surveys were conducted in boreholes on opposite sides of the iron injection zones using electric-dipole antennas with dominant center frequencies of 100 and 250 MHz. Significant decreases in the radar-pulse amplitudes observed in scans that traversed the injection zones were interpreted by comparing field data to results of two-dimensional finite-difference time-domain numerical models and laboratory-scale physical models.The numerical and physical models simulate a wall of perfectly conducting material embedded in saturated sand. Results from the numerical and physical models show that the amplitude of the radar pulse transmitted across the edge of a conductive wall is about 43 percent of the amplitude of a radar pulse transmitted across background material. The amplitude of a radar pulse transmitted through a hole in a conductive wall increases as the aperture of the hole increases. The modeling results indicate that holes with an aperture of less than 40

Review of Plasmonic Nanocomposite Metamaterial Absorber

PubMed Central

Hedayati, Mehdi Keshavarz; Faupel, Franz; Elbahri, Mady

2014-01-01

Plasmonic metamaterials are artificial materials typically composed of noble metals in which the features of photonics and electronics are linked by coupling photons to conduction electrons of metal (known as surface _lasmon). These rationally designed structures have spurred interest noticeably since they demonstrate some fascinating properties which are unattainable with naturally occurring materials. Complete absorption of light is one of the recent exotic properties of plasmonic metamaterials which has broadened its application area considerably. This is realized by designing a medium whose impedance matches that of free space while being opaque. If such a medium is filled with some lossy medium, the resulting structure can absorb light totally in a sharp or broad frequency range. Although several types of metamaterials perfect absorber have been demonstrated so far, in the current paper we overview (and focus on) perfect absorbers based on nanocomposites where the total thickness is a few tens of nanometer and the absorption band is broad, tunable and insensitive to the angle of incidence. The nanocomposites consist of metal nanoparticles embedded in a dielectric matrix with a high filling factor close to the percolation threshold. The filling factor can be tailored by the vapor phase co-deposition of the metallic and dielectric components. In addition, novel wet chemical approaches are discussed which are bio-inspired or involve synthesis within levitating Leidenfrost drops, for instance. Moreover, theoretical considerations, optical properties, and potential application of perfect absorbers will be presented. PMID:28788511

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

Spaceborne radar observations: A guide for Magellan radar-image analysis

NASA Technical Reports Server (NTRS)

Ford, J. P.; Blom, R. G.; Crisp, J. A.; Elachi, Charles; Farr, T. G.; Saunders, R. Stephen; Theilig, E. E.; Wall, S. D.; Yewell, S. B.

1989-01-01

Geologic analyses of spaceborne radar images of Earth are reviewed and summarized with respect to detecting, mapping, and interpreting impact craters, volcanic landforms, eolian and subsurface features, and tectonic landforms. Interpretations are illustrated mostly with Seasat synthetic aperture radar and shuttle-imaging-radar images. Analogies are drawn for the potential interpretation of radar images of Venus, with emphasis on the effects of variation in Magellan look angle with Venusian latitude. In each landform category, differences in feature perception and interpretive capability are related to variations in imaging geometry, spatial resolution, and wavelength of the imaging radar systems. Impact craters and other radially symmetrical features may show apparent bilateral symmetry parallel to the illumination vector at low look angles. The styles of eruption and the emplacement of major and minor volcanic constructs can be interpreted from morphological features observed in images. Radar responses that are governed by small-scale surface roughness may serve to distinguish flow types, but do not provide unambiguous information. Imaging of sand dunes is rigorously constrained by specific angular relations between the illumination vector and the orientation and angle of repose of the dune faces, but is independent of radar wavelength. With a single look angle, conditions that enable shallow subsurface imaging to occur do not provide the information necessary to determine whether the radar has recorded surface or subsurface features. The topographic linearity of many tectonic landforms is enhanced on images at regional and local scales, but the detection of structural detail is a strong function of illumination direction. Nontopographic tectonic lineaments may appear in response to contrasts in small-surface roughness or dielectric constant. The breakpoint for rough surfaces will vary by about 25 percent through the Magellan viewing geometries from low to high

Automatic position calculating imaging radar with low-cost synthetic aperture sensor for imaging layered media

DOEpatents

Mast, J.E.

1998-08-18

An imaging system for analyzing structures comprises a radar transmitter and receiver connected to a timing mechanism that allows a radar echo sample to be taken at a variety of delay times for each radar pulse transmission. The radar transmitter and receiver are coupled to a position determining system that provides the x,y position on a surface for each group of samples measured for a volume from the surface. The radar transmitter and receiver are moved about the surface to collect such groups of measurements from a variety of x,y positions. Return signal amplitudes represent the relative reflectivity of objects within the volume and the delay in receiving each signal echo represents the depth at which the object lays in the volume and the propagation speeds of the intervening material layers. Successively deeper z-planes are backward propagated from one layer to the next with an adjustment for variations in the expected propagation velocities of the material layers that lie between adjacent z-planes. 10 figs.

Ultrathin and lightweight microwave absorbers made of mu-near-zero metamaterials

PubMed Central

Zhong, Shuomin; He, Sailing

2013-01-01

We present a theory of perfect absorption in a bilayer model composed of a mu-near-zero (MNZ) metamaterial (MM) absorbing layer on a metallic substrate. Our analytical solutions reveal that a MM layer with a large purely imaginary permeability and a moderate permittivity backed by a metallic plane has a zero reflection at normal incidence when the thickness is ultrathin. The impedance-mismatched metamaterial absorber (MA) can be 77.3% thinner than conventional impedance-matched MAs with the same material loss in order to get the same absorption. A microwave absorber using double-layered spiral MMs with a thickness of only about one percent of the operating wavelength is designed and realized. An absorption efficiency above 93% at 1.74 GHz is demonstrated experimentally at illumination angles up to 60 degrees. Our absorber is 98% lighter than traditional microwave absorbers made of natural materials working at the same frequencies. PMID:23803861

Cassini radar : system concept and simulation results

NASA Astrophysics Data System (ADS)

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

1998-10-01

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

Space Radar Image of Raco Biomass Map

NASA Technical Reports Server (NTRS)

1999-01-01

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

Space Radar Image of Long Island Optical/Radar

NASA Technical Reports Server (NTRS)

1994-01-01

This pair of images of the Long Island, New York region is a comparison of an optical photograph (top) and a radar image (bottom), both taken in darkness in April 1994. The photograph at the top was taken by the Endeavour astronauts at about 3 a.m. Eastern time on April 20, 1994. The image at the bottom was acquired at about the same time four days earlier on April 16,1994 by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) system aboard the space shuttle Endeavour. Both images show an area approximately 100 kilometers by 40 kilometers (62 miles by 25 miles) that is centered at 40.7 degrees North latitude and 73.5 degrees West longitude. North is toward the upper right. The optical image is dominated by city lights, which are particularly bright in the densely developed urban areas of New York City located on the left half of the photo. The brightest white zones appear on the island of Manhattan in the left center, and Central Park can be seen as a darker area in the middle of Manhattan. To the northeast (right) of the city, suburban Long Island appears as a less densely illuminated area, with the brightest zones occurring along major transportation and development corridors. Since radar is an active sensing system that provides its own illumination, the radar image shows a great amount of surface detail, despite the night-time acquisition. The colors in the radar image were obtained using the following radar channels: red represents the L-band (horizontally transmitted and received); green represents the L-band (horizontally transmitted and vertically received); blue represents the C-band (horizontally transmitted and vertically received). In this image, the water surface - the Atlantic Ocean along the bottom edge and Long Island Sound shown at the top edge - appears red because small waves at the surface strongly reflect the horizontally transmitted and received L-band radar signal. Networks of highways and railroad lines are clearly

Space Radar Image of Long Island Optical/Radar

NASA Image and Video Library

1999-05-01

This pair of images of the Long Island, New York region is a comparison of an optical photograph (top) and a radar image (bottom), both taken in darkness in April 1994. The photograph at the top was taken by the Endeavour astronauts at about 3 a.m. Eastern time on April 20, 1994. The image at the bottom was acquired at about the same time four days earlier on April 16,1994 by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) system aboard the space shuttle Endeavour. Both images show an area approximately 100 kilometers by 40 kilometers (62 miles by 25 miles) that is centered at 40.7 degrees North latitude and 73.5 degrees West longitude. North is toward the upper right. The optical image is dominated by city lights, which are particularly bright in the densely developed urban areas of New York City located on the left half of the photo. The brightest white zones appear on the island of Manhattan in the left center, and Central Park can be seen as a darker area in the middle of Manhattan. To the northeast (right) of the city, suburban Long Island appears as a less densely illuminated area, with the brightest zones occurring along major transportation and development corridors. Since radar is an active sensing system that provides its own illumination, the radar image shows a great amount of surface detail, despite the night-time acquisition. The colors in the radar image were obtained using the following radar channels: red represents the L-band (horizontally transmitted and received); green represents the L-band (horizontally transmitted and vertically received); blue represents the C-band (horizontally transmitted and vertically received). In this image, the water surface - the Atlantic Ocean along the bottom edge and Long Island Sound shown at the top edge - appears red because small waves at the surface strongly reflect the horizontally transmitted and received L-band radar signal. Networks of highways and railroad lines are clearly

Design on the wide band absorber with low density based on the particle distribution

NASA Astrophysics Data System (ADS)

Zheng, Dianliang; Liu, Ting; Liu, Longbin; Xu, Yonggang

2018-04-01

In order to widen the absorbing band, an equivalent gradient structure absorber was designed based on the particle distribution. Firstly, the electromagnetic parameter of the absorbent with uniform dispersion was tested using the vector network analyzer in 8-18 GHz. Three different equivalent materials of the spherical, square and hexagon empty shape were designed. The scattering parameters and the monostatic reflection loss (RL) of the periodic structural materials were simulated in the commercial software. Then the effective permittivity and the permeability was derived by the Nicolson-Ross-Weir algorithm and fitted by Maxwell-Garnett mixing rule. The results showed that the simulated reflectance and transmission parameters of equivalent composites with the different shapes were very close. The derived effective permittivity and permeability of the composite with different absorbent content was also close, and the average deviation was about 0.52 + j0.15 and 0.15 + j0.01 respectively. Finally, the wide band absorbing material was designed using the genetic algorithm. The optimized RL result showed that the absorbing composites with thickness 3 mm had an excellent absorbing property (RL <-10 dB) in 8-18 GHz, the equivalent absorber density could be decreased 30.7% compared with the uniform structure.

Combining linear polarization spectroscopy and the Representative Layer Theory to measure the Beer-Lambert law absorbance of highly scattering materials.

PubMed

Gobrecht, Alexia; Bendoula, Ryad; Roger, Jean-Michel; Bellon-Maurel, Véronique

2015-01-01

Visible and Near Infrared (Vis-NIR) Spectroscopy is a powerful non destructive analytical method used to analyze major compounds in bulk materials and products and requiring no sample preparation. It is widely used in routine analysis and also in-line in industries, in-vivo with biomedical applications or in-field for agricultural and environmental applications. However, highly scattering samples subvert Beer-Lambert law's linear relationship between spectral absorbance and the concentrations. Instead of spectral pre-processing, which is commonly used by Vis-NIR spectroscopists to mitigate the scattering effect, we put forward an optical method, based on Polarized Light Spectroscopy to improve the absorbance signal measurement on highly scattering samples. This method selects part of the signal which is less impacted by scattering. The resulted signal is combined in the Absorption/Remission function defined in Dahm's Representative Layer Theory to compute an absorbance signal fulfilling Beer-Lambert's law, i.e. being linearly related to concentration of the chemicals composing the sample. The underpinning theories have been experimentally evaluated on scattering samples in liquid form and in powdered form. The method produced more accurate spectra and the Pearson's coefficient assessing the linearity between the absorbance spectra and the concentration of the added dye improved from 0.94 to 0.99 for liquid samples and 0.84-0.97 for powdered samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Burnable absorber arrangement for fuel bundle

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

Crowther, R.L.; Townsend, D.B.

1986-12-16

This patent describes a boiling water reactor core whose operation is characterized by a substantial proportion of steam voids with concomitantly reduced moderation toward the top of the core when the reactor is in its hot operating condition. The reduced moderation leads to slower burnup and greater conversion ratio in an upper core region so that when the reactor is in its cold shut down condition the resulting relatively increased moderation in the upper core region is accompanied by a reactivity profile that peaks in the upper core region. A fuel assembly is described comprising; a component of fissile materialmore » distributed over a substantial axial extent of the fuel assembly; and a component of neutron absorbing material having an axial distribution characterized by an enhancement in an axial zone of the fuel assembly, designated the cold shutdown control zone, corresponding to at least a portion of the axial region of the core when the cold shutdown reactivity peaks. The aggregate amount of neutron absorbing material in the cold shutdown zone of the fuel assembly is greater than the aggregate amount of neutron absorbing material in the axial zones of the fuel assembly immediately above and immediately below the cold shutdown control zone whereby the cold shutdown reactivity peak is reduced relative to the cold shutdown reactivity in the zones immediately above and immediately below the cold shutdown control zone. The cold shutdown zone has an axial extent measured from the bottom of the fuel assembly in the range between 68-88 percent of the height of the fissile material in the fuel assembly.« less

Estimated human absorbed dose of ¹⁷⁷Lu-BPAMD based on mice data: Comparison with ¹⁷⁷Lu-EDTMP.

PubMed

Yousefnia, Hassan; Zolghadri, Samaneh; Shanehsazzadeh, Saeed

2015-10-01

In this work, the absorbed dose of human organs for (177)Lu-BPAMD was evaluated based on biodistribution studies into the Syrian mice by RADAR method and was compared with (177)Lu-EDTMP as the only clinically used Lu-177 bone-seeking agent. The highest absorbed dose for both (177)Lu-BPAMD and (177)Lu-EDTMP is observed on the bone surface with 8.007 and 4.802 mSv/MBq. Generally, (177)Lu-BPAMD has considerable characteristics compared with (177)Lu-EDTMP and can be considered as a promising agent for the bone pain palliation therapy. Copyright © 2015 Elsevier Ltd. All rights reserved.

On the definition of absorbed dose

NASA Astrophysics Data System (ADS)

Grusell, Erik

2015-02-01

Purpose: The quantity absorbed dose is used extensively in all areas concerning the interaction of ionizing radiation with biological organisms, as well as with matter in general. The most recent and authoritative definition of absorbed dose is given by the International Commission on Radiation Units and Measurements (ICRU) in ICRU Report 85. However, that definition is incomplete. The purpose of the present work is to give a rigorous definition of absorbed dose. Methods: Absorbed dose is defined in terms of the random variable specific energy imparted. A random variable is a mathematical function, and it cannot be defined without specifying its domain of definition which is a probability space. This is not done in report 85 by the ICRU, mentioned above. Results: In the present work a definition of a suitable probability space is given, so that a rigorous definition of absorbed dose is possible. This necessarily includes the specification of the experiment which the probability space describes. In this case this is an irradiation, which is specified by the initial particles released and by the material objects which can interact with the radiation. Some consequences are discussed. Specific energy imparted is defined for a volume, and the definition of absorbed dose as a point function involves the specific energy imparted for a small mass contained in a volume surrounding the point. A possible more precise definition of this volume is suggested and discussed. Conclusions: The importance of absorbed dose motivates a proper definition, and one is given in the present work. No rigorous definition has been presented before.

Systems and Methods for Radar Data Communication

NASA Technical Reports Server (NTRS)

Bunch, Brian (Inventor); Szeto, Roland (Inventor); Miller, Brad (Inventor)

2013-01-01

A radar information processing system is operable to process high bandwidth radar information received from a radar system into low bandwidth radar information that may be communicated to a low bandwidth connection coupled to an electronic flight bag (EFB). An exemplary embodiment receives radar information from a radar system, the radar information communicated from the radar system at a first bandwidth; processes the received radar information into processed radar information, the processed radar information configured for communication over a connection operable at a second bandwidth, the second bandwidth lower than the first bandwidth; and communicates the radar information from a radar system, the radar information communicated from the radar system at a first bandwidth.

A study of different fabrics to increase radar cross section of humans.

PubMed

Ödman, Torbjörn; Welinder, Jan; Andersson, Nils; Otterskog, Magnus; Lindén, Maria; Ödman, Natalia; Larsson, Christer

2015-01-01

This purpose of the study was to increase the visibility on radar for unprotected pedestrians with the aid of conducting fabric. The experiment comprised measurements of four types of fabric to determine the radio frequency properties, such as radar cross section (RCS) for the vehicle radar frequency 77 GHz and transmission (shielding) in the frequency range 3-18 GHz. Two different thicknesses of polypyrrole (PPy) nonvowen fabric were tested and one thickness for 30 % and 40 % stainless steel fabrics respectively. A jacket with the thinner nonvowen material and one with 40 % steel were tested and compared to an unmodified jacket in the RCS measurement. The measurement showed an increase in RCS of 4 dB for the jacket with the 40 % steel lining compared to the unmodified jacket. The transmission measurement was aimed at determining the fabric with the highest transmission of an incoming radio wave. The 30 % steel fabric and the two thicknesses of the nonvowen fabrics were tested. One practical application is for example the use of radar reflective material in search and rescue (SAR) clothes. The study showed that the 30 % steel fabric was the best candidate for further RCS measurements.

Absorbed dose measurement in low temperature samples:. comparative methods using simulated material

NASA Astrophysics Data System (ADS)

Garcia, Ruth; Harris, Anthony; Winters, Martell; Howard, Betty; Mellor, Paul; Patil, Deepak; Meiner, Jason

2004-09-01

There is a growing need to reliably measure absorbed dose in low temperature samples, especially in the pharmaceutical and tissue banking industries. All dosimetry systems commonly used in the irradiation industry are temperature sensitive. Radiation of low temperature samples, such as those packaged with dry ice, must therefore take these dosimeter temperature effects into consideration. This paper will suggest a method to accurately deliver an absorbed radiation dose using dosimetry techniques designed to abrogate the skewing effects of low temperature environments on existing dosimetry systems.

Roadside IED detection using subsurface imaging radar and rotary UAV

NASA Astrophysics Data System (ADS)

Qin, Yexian; Twumasi, Jones O.; Le, Viet Q.; Ren, Yu-Jiun; Lai, C. P.; Yu, Tzuyang

2016-05-01

Modern improvised explosive device (IED) and mine detection sensors using microwave technology are based on ground penetrating radar operated by a ground vehicle. Vehicle size, road conditions, and obstacles along the troop marching direction limit operation of such sensors. This paper presents a new conceptual design using a rotary unmanned aerial vehicle (UAV) to carry subsurface imaging radar for roadside IED detection. We have built a UAV flight simulator with the subsurface imaging radar running in a laboratory environment and tested it with non-metallic and metallic IED-like targets. From the initial lab results, we can detect the IED-like target 10-cm below road surface while carried by a UAV platform. One of the challenges is to design the radar and antenna system for a very small payload (less than 3 lb). The motion compensation algorithm is also critical to the imaging quality. In this paper, we also demonstrated the algorithm simulation and experimental imaging results with different IED target materials, sizes, and clutters.

Metamaterial Absorber Based Multifunctional Sensor Application

NASA Astrophysics Data System (ADS)

Ozer, Z.; Mamedov, A. M.; Ozbay, E.

2017-02-01

In this study metamaterial based (MA) absorber sensor, integrated with an X-band waveguide, is numerically and experimentally suggested for important application including pressure, density sensing and marble type detecting applications based on rectangular split ring resonator, sensor layer and absorber layer that measures of changing in the dielectric constant and/or the thickness of a sensor layer. Changing of physical, chemical or biological parameters in the sensor layer can be detected by measuring the resonant frequency shifting of metamaterial absorber based sensor. Suggested MA based absorber sensor can be used for medical, biological, agricultural and chemical detecting applications in microwave frequency band. We compare the simulation and experimentally obtained results from the fabricated sample which are good agreement. Simulation results show that the proposed structure can detect the changing of the refractive indexes of different materials via special resonance frequencies, thus it could be said that the MA-based sensors have high sensitivity. Additionally due to the simple and tiny structures it could be adapted to other electronic devices in different sizes.

Stable fixation with absorbable sutures in craniofacial surgery.

PubMed

Linz, C; Kunz, F; Krauß, J; Böhm, H; Wirth, C; Hartmann, S; Wirbelauer, J; Schweitzer, T

2016-05-01

The present study analyses the exclusive use of absorbable suture material (Vicryl(®), Ethicon, Germany) in the fixation of transposed bone segments in craniofacial surgery without modification of the osteotomy design. Among 129 children up to 24 months of age, osteosynthesis was conducted exclusively with Vicryl(®) sutures. The stability of postoperative results was evaluated and possible foreign body reactions were examined within the framework of clinical and radiological routine checks. All examined children exhibited stable postoperative conditions while the length of hospital stay was not affected. X-ray examinations of the skull in two planes demonstrated good bony union in all cases. Relevant foreign body reactions were not observed. The exclusive application of absorbable suture material enables stable and cost effective osteosynthesis. Significant foreign body reactions were not observed. The exclusive use of absorbable sutures did not alter the osteotomy design. Copyright © 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Development of novel two-photon absorbing chromophores

NASA Astrophysics Data System (ADS)

Rogers, Joy E.; Slagle, Jonathan E.; McLean, Daniel G.; Sutherland, Richard L.; Krein, Douglas M.; Cooper, Thomas M.; Brant, Mark; Heinrichs, James; Kannan, Ramamurthi; Tan, Loon-Seng; Urbas, Augustine M.; Fleitz, Paul A.

2006-08-01

There has been much interest in the development of two-photon absorbing materials and many efforts to understand the nonlinear absorption properties of these dyes but this area is still not well understood. A computational model has been developed in our lab to understand the nanosecond nonlinear absorption properties that incorporate all of the measured one-photon photophysical parameters of a class of materials called AFX. We have investigated the nonlinear and photophysical properties of the AFX chromophores including the two-photon absorption cross-section, the excited state cross-section, the intersystem crossing quantum yield, and the singlet and triplet excited state lifetimes using a variety of experimental techniques that include UV-visible, fluorescence and phosphorescence spectroscopy, time correlated single photon counting, ultrafast transient absorption, and nanosecond laser flash photolysis. The model accurately predicts the nanosecond nonlinear transmittance data using experimentally measured parameters. Much of the strong nonlinear absorption has been shown to be due to excited state absorption from both the singlet and triplet excited states. Based on this understanding of the nonlinear absorption and the importance of singlet and triplet excited states we have begun to develop new two-photon absorbing molecules within the AFX class as well as linked to other classes of nonlinear absorbing molecules. This opens up the possibilities of new materials with unique and interesting properties. Specifically we have been working on a new class of two-photon absorbing molecules linked to platinum poly-ynes. In the platinum poly-yne chromophores the photophysics are more complicated and we have just started to understand what drives both the linear and non-linear photophysical properties.

Java Radar Analysis Tool

NASA Technical Reports Server (NTRS)

Zaczek, Mariusz P.

2005-01-01

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

Planetary surface characterization from dual-polarization radar observations

NASA Astrophysics Data System (ADS)

Virkki, Anne; Planetary Radar Team of the Arecibo Observatory

2017-10-01

We present a new method to investigate the physical properties of planetary surfaces using dual-polarization radar measurements. The number of radar observations has increased radically during the last five years, allowing us to compare the radar scattering properties of different small-body populations and compositional types. There has also been progress in the laboratory studies of the materials that are relevant to asteroids and comets.In a typical planetary radar measurement a circularly polarized signal is transmitted using a frequency of 2380 MHz (wavelength of 12.6 cm) or 8560 MHz (3.5 cm). The echo is received simultaneously in the same circular (SC) and the opposite circular (OC) polarization as the transmitted signal. The delay and doppler frequency of the signal give highly accurate astrometric information, and the intensity and the polarization are suggestive of the physical properties of the target's near-surface.The radar albedo describes the radar reflectivity of the target. If the effective near-surface is smooth and homogeneous in the wavelength-scale, the echo is received fully in the OC polarization. Wavelength-scale surface roughness or boulders within the effective near-surface volume increase the received echo power in both polarizations. However, there is a lack in the literature describing exactly how the physical properties of the target affect the radar albedo in each polarization, or how they can be derived from the radar measurements.To resolve this problem, we utilize the information that the diffuse components of the OC and SC parts are correlated when the near-surface contains wavelength-scale scatterers such as boulders. A linear least-squares fit to the detected values of OC and SC radar albedos allows us to separate the diffusely scattering part from the quasi-specular part. Combined with the spectro-photometric information of the target and laboratory studies of the permittivity-density dependence, the method provides us with a

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

PubMed Central

Ranganath, V.; Nichani, Ashish Sham

2013-01-01

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-є-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. PMID:23837127

Energy absorber uses expanded coiled tube

NASA Technical Reports Server (NTRS)

Johnson, E. F.

1972-01-01

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

Titan's surface from the Cassini RADAR radiometry data during SAR mode

USGS Publications Warehouse

Paganelli, F.; Janssen, M.A.; Lopes, R.M.; Stofan, E.; Wall, S.D.; Lorenz, R.D.; Lunine, J.I.; Kirk, R.L.; Roth, L.; Elachi, C.

2008-01-01

We present initial results on the calibration and interpretation of the high-resolution radiometry data acquired during the Synthetic Aperture Radar (SAR) mode (SAR-radiometry) of the Cassini Radar Mapper during its first five flybys of Saturn's moon Titan. We construct maps of the brightness temperature at the 2-cm wavelength coincident with SAR swath imaging. A preliminary radiometry calibration shows that brightness temperature in these maps varies from 64 to 89 K. Surface features and physical properties derived from the SAR-radiometry maps and SAR imaging are strongly correlated; in general, we find that surface features with high radar reflectivity are associated with radiometrically cold regions, while surface features with low radar reflectivity correlate with radiometrically warm regions. We examined scatterplots of the normalized radar cross-section ??0 versus brightness temperature, outlining signatures that characterize various terrains and surface features. The results indicate that volume scattering is important in many areas of Titan's surface, particularly Xanadu, while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties. ?? 2007.

FIRE_CI2_ETL_RADAR

Atmospheric Science Data Center

2015-11-25

FIRE_CI2_ETL_RADAR Project Title:  FIRE II CIRRUS Discipline:  ... Platform:  Ground Station Instrument:  Radar Spatial Coverage:  (37.06, -95.34) Spatial ... Order Data Guide Documents:  ETL_RADAR Guide Readme Files:  Readme ETL_RADAR (PS) ...

Use of absorbent materials in on-line coupled reversed-phase liquid chromatography-gas chromatography via the through oven transfer adsorption desorption interface.

PubMed

Flores, Gema; Díaz-Plaza, Eva María; Cortés, Jose Manuel; Villén, Jesús; Herraiz, Marta

2008-11-21

The use of absorbents as retaining materials in the through oven transfer adsorption desorption interface (TOTAD) of an on-line coupled reversed-phase liquid chromatography-gas chromatography system (RPLC-GC) is proposed for the first time. A comparative study of an adsorbent (Tenax TA) and two absorbents, namely polydimethylsiloxane and poly(50% phenyl/50% methylsiloxane) is performed to establish the best experimental conditions for the automated and simultaneous determination of 15 organophosphorus and organochlorine pesticide residues in olive oil. The proposed method provides satisfactory repeatability (RSDs lower, in general, than 8.5%) and sensitivity (limits of detection ranging from 0.6 to 81.9 microg/L) for the investigated compounds.

Global characterization of Titan's dune fields by RADAR and VIMS observations

NASA Astrophysics Data System (ADS)

garcia, A.; Rodriguez, S.; Lucas, A.; Appéré, T.; Le Gall, A.; Reffet, E.; Le Corre, L.; Le Mouélic, S.; Cornet, T.; Courrech Du Pont, S.; Narteau, C.; Bourgeois, O.; Radebaugh, J.; Arnold, K.; Barnes, J. W.; Sotin, C.; Brown, R. H.; Lorenz, R. D.; Turtle, E. P.

2013-12-01

Cassini/RADAR high-resolution images of Titan's surface revealed linear features, geomorphologically similar to longitudinal dunes. Those dunes cover a large portion of the whole surface of Titan, i.e 7.8%, and 13.4% are present on the 58.4% of the surface imaged by the RADAR/SAR from July 2004 to July 2013 (fig.1). 99.6% of the dunes are confined at the equatorial regions (30°N-30°S). Formed and sculpted by the wind, those features represent clues for the understanding of the climatic history on the satellite. By using the joint analysis between RADAR/SAR observations and the infrared VIMS mosaic corrected for atmospheric contributions acquired through July 2013 and June 2010 respectively, we found a very high degree of correlation at global scale (more than 70%) between the RADAR dunes and a specific infrared VIMS spectral unit, the 'dark brown unit'. Some RADAR dunes, less than 2%, also belong in a commonly referenced unit, the 'dark blue unit'. These two units have been delimited by defining for each a specific set of spectral criteria. We have shown that those two units present a spectral behavior different, especially at short wavelengths (below 2 μm) allowing to say that the 'dark brown unit' is dominated by organic sediment, similar to atmospheric aerosols, namely tholins, and the 'dark blue' is most likely enriched in water ice compared to the rest of Titan's surface. Given the strong correlation between RADAR dunes and the infrared 'dark brown unit' we are now able to extrapolate the total surface area of the dunes material to the total surface area of the 'dark brown unit' which correspond to 17% of the Titan's surface. This permits to estimate the volume of sediment of 360,000 km3 (total mass ≈ 290,000 GT). Thus, these estimates based on the RADAR dunes/VIMS units correlation make the dune fields the largest organic reservoir on Titan's surface and characterize more precisely the composition of the dune material over the total extend of the dune

Wave Absorber with Fine Weatherability for Improving ETC Environment

NASA Astrophysics Data System (ADS)

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

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.

The X-ray and ultraviolet absorbing outflow in 3C 351

NASA Astrophysics Data System (ADS)

Mathur, Smita; Wilkes, Belinda; Elvis, Martin; Fiore, Fabrizio

1994-10-01

3C 351 (z = 0.371), and X-ray-'quiet' quasar, is one of the few quasars showing signs of a 'warm absorber' in its X-ray spectrum; i.e., partially ionized absorbing material in the line of sight whose opacity depends on its ionization structure. The main feature in the X-ray spectrum is a K-edge due to O VII or O VIII. 3C 351 also shows unusually strong, blueshifted, associated, absorption lines in the ultraviolet (Bahcall et al. 1993) including O VI (lambda lambda 1031, 1037). This high ionization state strongly suggests an identification with the X-ray absorber and a site within the active nucleus. In this paper we demonstrate that the X-ray and UV absorption is due to the same material. This is the first confirmed UV/X-ray absorber. Physical conditions of the absorber are determined through the combination of constraints derived from both the X-ray and UV analysis. This highly ionized, outflowing, low-density, high-column density absorber situated outside the broad emission line region (BELR) is a previously unknown component of nuclear material. We rule out the identification of the absorber with a BELR cloud as the physical conditions in the two regions are inconsistent with one another. The effect of the X-ray quietness and IR upturn in the 3C 351 continuum on the BELR is also investigated. The strengths of the high-ionization lines of C IV lambda-1549 and O VI lambda-1034 with respect to Lyman-alpha are systematically lower (up to a factor of 10) in the material ionized by the 3C 351 continuum as compared to those produced by the 'standard' quasar continuum, the strongest effect being on the strength of O VI lambda-1034. We find that for a 3C 351-like continuum, C III) lambda-1909 ceases to be a density indicator.

Simulation, fabrication and characterization of THz metamaterial absorbers.

PubMed

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

2012-12-27

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 ~ λ/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.

RADAR performance experiments

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

46 CFR 121.404 - Radars.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Radars. 121.404 Section 121.404 Shipping COAST GUARD... Navigation Equipment § 121.404 Radars. (a) Except as allowed by paragraph (b) of this section, all self... radar system for surface navigation with a radar screen mounted at the primary operating station. (b...

46 CFR 121.404 - Radars.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Radars. 121.404 Section 121.404 Shipping COAST GUARD... Navigation Equipment § 121.404 Radars. (a) Except as allowed by paragraph (b) of this section, all self... radar system for surface navigation with a radar screen mounted at the primary operating station. (b...

46 CFR 121.404 - Radars.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Radars. 121.404 Section 121.404 Shipping COAST GUARD... Navigation Equipment § 121.404 Radars. (a) Except as allowed by paragraph (b) of this section, all self... radar system for surface navigation with a radar screen mounted at the primary operating station. (b...

46 CFR 121.404 - Radars.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Radars. 121.404 Section 121.404 Shipping COAST GUARD... Navigation Equipment § 121.404 Radars. (a) Except as allowed by paragraph (b) of this section, all self... radar system for surface navigation with a radar screen mounted at the primary operating station. (b...

46 CFR 121.404 - Radars.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Radars. 121.404 Section 121.404 Shipping COAST GUARD... Navigation Equipment § 121.404 Radars. (a) Except as allowed by paragraph (b) of this section, all self... radar system for surface navigation with a radar screen mounted at the primary operating station. (b...

Radar remote sensing in biology

USGS Publications Warehouse

Moore, Richard K.; Simonett, David S.

1967-01-01

The present status of research on discrimination of natural and cultivated vegetation using radar imaging systems is sketched. The value of multiple polarization radar in improved discrimination of vegetation types over monoscopic radars is also documented. Possible future use of multi-frequency, multi-polarization radar systems for all weather agricultural survey is noted.

Thermal tuning of infrared resonant absorbers based on hybrid gold-VO{sub 2} nanostructures

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

Kocer, Hasan; Department of Electrical Engineering, Turkish Military Academy, 06654 Ankara; Butun, Serkan

2015-04-20

Resonant absorbers based on plasmonic materials, metamaterials, and thin films enable spectrally selective absorption filters, where absorption is maximized at the resonance wavelength. By controlling the geometrical parameters of nano/microstructures and materials' refractive indices, resonant absorbers are designed to operate at wide range of wavelengths for applications including absorption filters, thermal emitters, thermophotovoltaic devices, and sensors. However, once resonant absorbers are fabricated, it is rather challenging to control and tune the spectral absorption response. Here, we propose and demonstrate thermally tunable infrared resonant absorbers using hybrid gold-vanadium dioxide (VO{sub 2}) nanostructure arrays. Absorption intensity is tuned from 90% to 20%more » and 96% to 32% using hybrid gold-VO{sub 2} nanowire and nanodisc arrays, respectively, by heating up the absorbers above the phase transition temperature of VO{sub 2} (68 °C). Phase change materials such as VO{sub 2} deliver useful means of altering optical properties as a function of temperature. Absorbers with tunable spectral response can find applications in sensor and detector applications, in which external stimulus such as heat, electrical signal, or light results in a change in the absorption spectrum and intensity.« less

High-resolution nondestructive testing of multilayer dielectric materials using wideband microwave synthetic aperture radar imaging

NASA Astrophysics Data System (ADS)

Kim, Tae Hee; James, Robin; Narayanan, Ram M.

2017-04-01

Fiber Reinforced Polymer or Plastic (FRP) composites have been rapidly increasing in the aerospace, automotive and marine industry, and civil engineering, because these composites show superior characteristics such as outstanding strength and stiffness, low weight, as well as anti-corrosion and easy production. Generally, the advancement of materials calls for correspondingly advanced methods and technologies for inspection and failure detection during production or maintenance, especially in the area of nondestructive testing (NDT). Among numerous inspection techniques, microwave sensing methods can be effectively used for NDT of FRP composites. FRP composite materials can be produced using various structures and materials, and various defects or flaws occur due to environmental conditions encountered during operation. However, reliable, low-cost, and easy-to-operate NDT methods have not been developed and tested. FRP composites are usually produced as multilayered structures consisting of fiber plate, matrix and core. Therefore, typical defects appearing in FRP composites are disbondings, delaminations, object inclusions, and certain kinds of barely visible impact damages. In this paper, we propose a microwave NDT method, based on synthetic aperture radar (SAR) imaging algorithms, for stand-off imaging of internal delaminations. When a microwave signal is incident on a multilayer dielectric material, the reflected signal provides a good response to interfaces and transverse cracks. An electromagnetic wave model is introduced to delineate interface widths or defect depths from the reflected waves. For the purpose of numerical analysis and simulation, multilayered composite samples with various artificial defects are assumed, and their SAR images are obtained and analyzed using a variety of high-resolution wideband waveforms.

Development of Radar Control system for Multi-mode Active Phased Array Radar for atmospheric probing

NASA Astrophysics Data System (ADS)

Yasodha, Polisetti; Jayaraman, Achuthan; Thriveni, A.

2016-07-01

Modern multi-mode active phased array radars require highly efficient radar control system for hassle free real time radar operation. The requirement comes due to the distributed architecture of the active phased array radar, where each antenna element in the array is connected to a dedicated Transmit-Receive (TR) module. Controlling the TR modules, which are generally few hundreds in number, and functioning them in synchronisation, is a huge task during real time radar operation and should be handled with utmost care. Indian MST Radar, located at NARL, Gadanki, which is established during early 90's, as an outcome of the middle atmospheric program, is a remote sensing instrument for probing the atmosphere. This radar has a semi-active array, consisting of 1024 antenna elements, with limited beam steering, possible only along the principle planes. To overcome the limitations and difficulties, the radar is being augmented into fully active phased array, to accomplish beam agility and multi-mode operations. Each antenna element is excited with a dedicated 1 kW TR module, located in the field and enables to position the radar beam within 20° conical volume. A multi-channel receiver makes the radar to operate in various modes like Doppler Beam Swinging (DBS), Spaced Antenna (SA), Frequency Domain Interferometry (FDI) etc. Present work describes the real-time radar control (RC) system for the above described active phased array radar. The radar control system consists of a Spartan 6 FPGA based Timing and Control Signal Generator (TCSG), and a computer containing the software for controlling all the subsystems of the radar during real-time radar operation and also for calibrating the radar. The main function of the TCSG is to generate the control and timing waveforms required for various subsystems of the radar. Important components of the RC system software are (i) TR module configuring software which does programming, controlling and health parameter monitoring of the

Radar Remote Sensing

NASA Technical Reports Server (NTRS)

Rosen, Paul A.

2012-01-01

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

Creating soil moisture maps based on radar satellite imagery

NASA Astrophysics Data System (ADS)

Hnatushenko, Volodymyr; Garkusha, Igor; Vasyliev, Volodymyr

2017-10-01

The presented work is related to a study of mapping soil moisture basing on radar data from Sentinel-1 and a test of adequacy of the models constructed on the basis of data obtained from alternative sources. Radar signals are reflected from the ground differently, depending on its properties. In radar images obtained, for example, in the C band of the electromagnetic spectrum, soils saturated with moisture usually appear in dark tones. Although, at first glance, the problem of constructing moisture maps basing on radar data seems intuitively clear, its implementation on the basis of the Sentinel-1 data on an industrial scale and in the public domain is not yet available. In the process of mapping, for verification of the results, measurements of soil moisture obtained from logs of the network of climate stations NOAA US Climate Reference Network (USCRN) were used. This network covers almost the entire territory of the United States. The passive microwave radiometers of Aqua and SMAP satellites data are used for comparing processing. In addition, other supplementary cartographic materials were used, such as maps of soil types and ready moisture maps. The paper presents a comparison of the effect of the use of certain methods of roughening the quality of radar data on the result of mapping moisture. Regression models were constructed showing dependence of backscatter coefficient values Sigma0 for calibrated radar data of different spatial resolution obtained at different times on soil moisture values. The obtained soil moisture maps of the territories of research, as well as the conceptual solutions about automation of operations of constructing such digital maps, are presented. The comparative assessment of the time required for processing a given set of radar scenes with the developed tools and with the ESA SNAP product was carried out.

Liquid carbon dioxide absorbents, methods of using the same, and related system

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

Perry, Robert James; Soloveichik, Grigorii Lev; Rubinsztajn, Malgorzata Iwona

A carbon dioxide absorbent composition is described, including (i) a liquid, nonaqueous silicon-based material, functionalized with one or more groups that either reversibly react with CO 2 or have a high-affinity for CO 2, and (ii) a hydroxy-containing solvent that is capable of dissolving both the silicon-based material and a reaction product of the silicon-based material and CO 2. The absorbent may be utilized in methods to reduce carbon dioxide in an exhaust gas, and finds particular utility in power plants.

Multi-Wavelength Observations of 2100 Ra-Shalom: Radar and Lightcurves

NASA Technical Reports Server (NTRS)

Shepard, M. K.; Clark-Joseph, B. E.; Benner, L. A. M.; Giorgini, J. D.; Kusnirak, P.; Margot, J.-L.; Nolan, M. C.; Ostro, S. J.; Pravec, P.; Sarounova, L.

2004-01-01

We conducted a multi-wavelength campaign to study the near-Earth asteroid (NEA) 2100 Ra-Shalom during its August 2003 encounter. Rotationally resolved observations were acquired at Arecibo (12.6 cm radar), the IRTF (0.8-2.5 micron and 3 micron), McDonald Observatory (0.48-0.92 micron), Palomar Observatory (8-15 micron), and Ondrejov Observatory (optical lightcurves). Our objectives were to determine Ra-Shalom's size and shape, and the composition and physical state of its near-surface material. Preliminary results from radar and lightcurve measurements will be presented here.

Design of Vivaldi Microstrip Antenna for Ultra-Wideband Radar Applications

NASA Astrophysics Data System (ADS)

Perdana, M. Y.; Hariyadi, T.; Wahyu, Y.

2017-03-01

The development of radar technology has an important role in several fields such as aviation, civil engineering, geology, and medicine. One of the essential components of the radar system is the antenna. The bandwidth can specify the resolution of the radar. The wider the bandwidth, the higher the resolution of radar. For Ground penetrating radar (GPR) or medical applications need with a high-resolution radar so it needs an antenna with a wide bandwidth. In addition, for the radar application is required antenna with directional radiation pattern. So, we need an antenna with wide bandwidth and directional radiation pattern. One of antenna that has meet with these characteristics is vivaldi antenna. In previous research, has designed several vivaldi microstrip antenna for ultra-wideband radar applications which has a working frequency of 3.1 to 10.7 GHz. However, these studies there is still a shortage of one of them is the radiation pattern from lowest to highest frequency radiation pattern is not uniform in the sense that not all directional. Besides the antenna material used is also not easily available and the price is not cheap. This paper will discuss the design of a vivaldi microstrip antenna which has a wide bandwidth with directional radiation pattern works on 3.1 to 10.7 GHz and using cheaper substrate. Substrates used for vivaldi microstrip antenna vivaldi is FR4 with a dielectric constant of 4.3 and a thickness of 1.6 mm. Based on the simulation results we obtained that the antenna design has frequency range 3.1-10.7 GHz for return loss less than -10 dB with a directional radiation pattern. This antenna gain is 4.8 to 8 dBi with the largest dimension is 50 mm x 40 mm.

Role of the calcaneal heel pad and polymeric shock absorbers in attenuation of heel strike impact.

PubMed

Noe, D A; Voto, S J; Hoffmann, M S; Askew, M J; Gradisar, I A

1993-01-01

The capacity of the calcaneal heel pad, with and without augmentation by a polymeric shock absorbing material (Sorbothane 0050), to attenuate heel strike impulses has been studied using five fresh human cadaveric lower leg specimens. The specimens, instrumented with an accelerometer, were suspended and impacted with a hammer; a steel rod was similarly suspended and impacted. The calcaneal heel pad attenuated the peak accelerations by 80%. Attenuations of up to 93% were achieved by the shock absorbing material when tested against the steel rod; however, when tested in series with the calcaneal heel pad, the reduction in peak acceleration due to the shock absorbing material dropped to 18%. Any evaluation of the effectiveness of shock absorbing shoe materials must take into account their mechanical interaction with the body.

Portable concealed weapon detection using millimeter-wave FMCW radar imaging

NASA Astrophysics Data System (ADS)

Johnson, Michael A.; Chang, Yu-Wen

2001-02-01

Unobtrusive detection of concealed weapons on persons or in abandoned bags would provide law enforcement a powerful tool to focus resources and increase traffic throughput in high- risk situations. We have developed a fast image scanning 94 GHz radar system that is suitable for portable operation and remote viewing of radar data. This system includes a novel fast image-scanning antenna that allows for the acquisition of medium resolution 3D millimeter wave images of stationary targets with frame times on order of one second. The 3D radar data allows for potential isolation of concealed weapons from body and environmental clutter such as nearby furniture or other people. The radar is an active system so image quality is not affected indoors, emitted power is however very low so there are no health concerns for operator or targets. The low power operation is still sufficient to penetrate heavy clothing or material. Small system size allows for easy transport and rapid deployment of the system as well as an easy migration path to future hand held systems.

Obstacle penetrating dynamic radar imaging system

DOEpatents

Romero, Carlos E [Livermore, CA; Zumstein, James E [Livermore, CA; Chang, John T [Danville, CA; Leach, Jr Richard R. [Castro Valley, CA

2006-12-12

An obstacle penetrating dynamic radar imaging system for the detection, tracking, and imaging of an individual, animal, or object comprising a multiplicity of low power ultra wideband radar units that produce a set of return radar signals from the individual, animal, or object, and a processing system for said set of return radar signals for detection, tracking, and imaging of the individual, animal, or object. The system provides a radar video system for detecting and tracking an individual, animal, or object by producing a set of return radar signals from the individual, animal, or object with a multiplicity of low power ultra wideband radar units, and processing said set of return radar signals for detecting and tracking of the individual, animal, or object.

Synergistic Use of Spacecraft Telecom Links for Collection of Planetary Radar Science Data

NASA Astrophysics Data System (ADS)

Asmar, S.; Bell, D. J.; Chahat, N. E.; Decrossas, E.; Dobreva, T.; Duncan, C.; Ellliot, H.; Jin, C.; Lazio, J.; Miller, J.; Preston, R.

2017-12-01

On multiple solar system missions, radar instruments have been used to probe subsurface geomorphology and to infer chemical composition based on the dielectric signature derived from the reflected signal. Example spacecraft radar instruments are the 90 MHz CONSERT radar used to probe the interior of Comet 67P/Churyumov-Gerasimenko to a depth of 760m, the 20 MHz SHARAD instrument used to investigate Mars subsurface ice features from Mars orbit at depths of 300 to 3000 meters and the upcoming RIMFAX 150 MHz to 1200 MHz ground penetrating radar that will ride on the Mars 2020 rover investigating to a depth of 10m below the rover. In all of these applications, the radar frequency and signal structures were chosen to match science goals of desired depth of penetration and spatial resolution combined with the expected subsurface materials and structures below the surface. Recently, JPL investigators have proposed a new radar science paradigm, synergistic use of the telecom hardware and telecom links to collect bistatic or monostatic radar signatures. All JPL spacecraft employ telecom hardware that operates at UHF (400 MHz and 900 MHz), X-band (8 GHz) or Ka-band (32 GHz). Using existing open-loop record functions in these radios, the telecom hardware can be used to capture opportunistic radar signatures from telecom signals penetrating the surface and reflecting off of subsurface structures. This paper reports on telecom strategies, radar science applications and recent laboratory and field tests to demonstrate the effectiveness of telecom link based radar data collection.

Microstructure Analysis of Bismuth Absorbers for Transition-Edge Sensor X-ray Microcalorimeters

NASA Astrophysics Data System (ADS)

Yan, Daikang; Divan, Ralu; Gades, Lisa M.; Kenesei, Peter; Madden, Timothy J.; Miceli, Antonino; Park, Jun-Sang; Patel, Umeshkumar M.; Quaranta, Orlando; Sharma, Hemant; Bennett, Douglas A.; Doriese, William B.; Fowler, Joseph W.; Gard, Johnathon D.; Hays-Wehle, James P.; Morgan, Kelsey M.; Schmidt, Daniel R.; Swetz, Daniel S.; Ullom, Joel N.

2018-03-01

Given its large X-ray stopping power and low specific heat capacity, bismuth (Bi) is a promising absorber material for X-ray microcalorimeters and has been used with transition-edge sensors (TESs) in the past. However, distinct X-ray spectral features have been observed in TESs with Bi absorbers deposited with different techniques. Evaporated Bi absorbers are widely reported to have non-Gaussian low-energy tails, while electroplated ones do not show this feature. In this study, we fabricated Bi absorbers with these two methods and performed microstructure analysis using scanning electron microscopy and X-ray diffraction microscopy. The two types of material showed the same crystallographic structure, but the grain size of the electroplated Bi was about 40 times larger than that of the evaporated Bi. This distinction in grain size is likely to be the cause of their different spectral responses.

Survey of Ultra-wideband Radar

NASA Astrophysics Data System (ADS)

Mokole, Eric L.; Hansen, Pete

The development of UWB radar over the last four decades is very briefly summarized. A discussion of the meaning of UWB is followed by a short history of UWB radar developments and discussions of key supporting technologies and current UWB radars. Selected UWB radars and the associated applications are highlighted. Applications include detecting and imaging buried mines, detecting and mapping underground utilities, detecting and imaging objects obscured by foliage, through-wall detection in urban areas, short-range detection of suicide bombs, and the characterization of the impulse responses of various artificial and naturally occurring scattering objects. In particular, the Naval Research Laboratory's experimental, low-power, dual-polarized, short-pulse, ultra-high resolution radar is used to discuss applications and issues of UWB radar. Some crucial issues that are problematic to UWB radar are spectral availability, electromagnetic interference and compatibility, difficulties with waveform control/shaping, hardware limitations in the transmission chain, and the unreliability of high-power sources for sustained use above 2 GHz.

Radar: Human Safety Net

ERIC Educational Resources Information Center

Ritz, John M.

2016-01-01

Radar is a technology that can be used to detect distant objects not visible to the human eye. A predecessor of radar, called the telemobiloscope, was first used to detect ships in the fog in 1904 off the German coast. Many scientists have worked on the development and refinement of radar (Hertz with electromagnetic waves; Popov with determining…

German Radar Observation Shuttle Experiment (ROSE)

NASA Technical Reports Server (NTRS)

Sleber, A. J.; Hartl, P.; Haydn, R.; Hildebrandt, G.; Konecny, G.; Muehlfeld, R.

1984-01-01

The success of radar sensors in several different application areas of interest depends on the knowledge of the backscatter of radar waves from the targets of interest, the variance of these interaction mechanisms with respect to changing measurement parameters, and the determination of the influence of he measuring systems on the results. The incidence-angle dependency of the radar cross section of different natural targets is derived. Problems involved by the combination of data gained with different sensors, e.g., MSS-, TM-, SPOTand SAR-images are analyzed. Radar cross-section values gained with ground-based radar spectrometers and spaceborne radar imaging, and non-imaging scatterometers and spaceborne radar images from the same areal target are correlated. The penetration of L-band radar waves into vegetated and nonvegetated surfaces is analyzed.

Liquid carbon dioxide absorbents, methods of using the same, and related systems

DOEpatents

O'Brien, Michael Joseph; Perry, Robert James; Lam, Tunchiao Hubert; Soloveichik, Grigorii Lev; Kniajanski, Sergei; Lewis, Larry Neil; Rubinsztajn, Malgorzata Iwona; Hancu, Dan

2016-09-13

A carbon dioxide absorbent composition is described, including (i) a liquid, nonaqueous silicon-based material, functionalized with one or more groups that either reversibly react with CO.sub.2 or have a high-affinity for CO.sub.2; and (ii) a hydroxy-containing solvent that is capable of dissolving both the silicon-based material and a reaction product of the silicon-based material and CO.sub.2. The absorbent may be utilized in methods to reduce carbon dioxide in an exhaust gas, and finds particular utility in power plants.

Using TRMM and GPM precipitation radar for calibration of weather radars in the Philippines

NASA Astrophysics Data System (ADS)

Crisologo, Irene; Bookhagen, Bodo; Smith, Taylor; Heistermann, Maik

2016-04-01

Torrential and sustained rainfall from tropical cyclones, monsoons, and thunderstorms frequently impact the Philippines. In order to predict, assess, and measure storm impact, it is imperative to have a reliable and accurate monitoring system in place. In 2011, the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) established a weather radar network of ten radar devices, eight of which are single-polarization S-band radars and two dual-polarization C-band radars. Because of a low-density hydrometeorological monitoring networks in the Philippines, calibration of weather radars becomes a challenging, but important task. In this study, we explore the potential of scrutinizing the calibration of ground radars by using the observations from the Tropical Rainfall Measuring Mission (TRMM). For this purpose, we compare different TRMM level 1 and 2 orbital products from overpasses over the Philippines, and compare these products to reflectivities observed by the Philippine ground radars. Differences in spatial resolution are addressed by computing adequate zonal statistics of the local radar bins located within the corresponding TRMM cell in space and time. The wradlib package (Heistermann et al. 2013; Heistermann et al. 2015) is used to process the data from the Subic S-band single-polarization weather radar. These data will be analyzed in conjunction with TRMM data for June to August 2012, three months of the wet season. This period includes the enhanced monsoon of 2012, locally called Habagat 2012, which brought sustained intense rainfall and massive floods in several parts of the country including the most populated city of Metro Manila. References Heistermann, M., Jacobi, S., Pfaff, T. (2013): Technical Note: An open source library for processing weather radar data (wradlib). Hydrol. Earth Syst. Sci., 17, 863-871, doi: 10.5194/hess-17-863-2013. Heistermann, M., S. Collis, M. J. Dixon, S. Giangrande, J. J. Helmus, B. Kelley, J

Spaceborne Imaging Radar-C instrument

NASA Technical Reports Server (NTRS)

Huneycutt, Bryan L.

1993-01-01

The Spaceborne Imaging Radar-C is the next radar in the series of spaceborne radar experiments, which began with Seasat and continued with SIR-A and SIR-B. The SIR-C instrument has been designed to obtain simultaneous multifrequency and simultaneous multipolarization radar images from a low earth orbit. It is a multiparameter imaging radar that will be flown during at least two different seasons. The instrument operates in the squint alignment mode, the extended aperture mode, the scansar mode, and the interferometry mode. The instrument uses engineering techniques such as beam nulling for echo tracking, pulse repetition frequency hopping for Doppler centroid tracking, generating the frequency step chirp for radar parameter flexibility, block floating-point quantizing for data rate compression, and elevation beamwidth broadening for increasing the swath illumination.

Study to investigate and evaluate means of optimizing the radar function for the space shuttle. [(pulse radar)

NASA Technical Reports Server (NTRS)

1975-01-01

Results are discussed of a study to define a radar and antenna system which best suits the space shuttle rendezvous requirements. Topics considered include antenna characteristics and antenna size tradeoffs, fundamental sources of measurement errors inherent in the target itself, backscattering crosssection models of the target and three basic candidate radar types. Antennas up to 1.5 meters in diameter are within specified installation constraints, however, a 1 meter diameter paraboloid and a folding, four slot backfeed on a two gimbal mount implemented for a spiral acquisition scan is recommended. The candidate radar types discussed are: (1) noncoherent pulse radar (2) coherent pulse radar and (3) pulse Doppler radar with linear FM ranging. The radar type recommended is a pulse Doppler with linear FM ranging. Block diagrams of each radar system are shown.

Different CO2 absorbents-modified SBA-15 sorbent for highly selective CO2 capture

NASA Astrophysics Data System (ADS)

Liu, Xiuwu; Zhai, Xinru; Liu, Dongyang; Sun, Yan

2017-05-01

Different CO2 absorbents-modified SBA-15 materials are used as CO2 sorbent to improve the selectivity of CH4/CO2 separation. The SBA-15 sorbents modified by physical CO2 absorbents are very limited to increasing CO2 adsorption and present poor selectivity. However, the SBA-15 sorbents modified by chemical CO2 absorbents increase CO2 adsorption capacity obviously. The separation coefficients of CO2/CH4 increase in this case. The adsorption and regeneration properties of the SBA-15 sorbents modified by TEA, MDEA and DIPA have been compared. The SBA-15 modified by triethanolamine (TEA) presents better CO2/CH4 separation performance than the materials modified by other CO2 absorbents.

The Comet Radar Explorer Mission

NASA Astrophysics Data System (ADS)

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

2014-11-01

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

High Conduction Neutron Absorber to Simulate Fast Reactor Environment in an Existing Test Reactor

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

Guillen, Donna; Greenwood, Lawrence R.; Parry, James

2014-06-22

A need was determined for a thermal neutron absorbing material that could be cooled in a gas reactor environment without using large amounts of a coolant that would thermalize the neutron flux. A new neutron absorbing material was developed that provided high conduction so a small amount of water would be sufficient for cooling thereby thermalizing the flux as little as possible. An irradiation experiment was performed to assess the effects of radiation and the performance of a new neutron absorbing material. Neutron fluence monitors were placed inside specially fabricated holders within a set of drop-in capsules and irradiated formore » up to four cycles in the Advanced Test Reactor. Following irradiation, the neutron fluence monitor wires were analyzed by gamma and x-ray spectrometry to determine the activities of the activation products. The adjusted neutron fluences were calculated and grouped into three bins – thermal, epithermal and fast to evaluate the spectral shift created by the new material. Fluence monitors were evaluated after four different irradiation periods to evaluate the effects of burn-up in the absorbing material. Additionally, activities of the three highest activity isotopes present in the specimens are given.« less

SAR-EDU - An education initiative for applied Synthetic Aperture Radar remote sensing

NASA Astrophysics Data System (ADS)

Eckardt, Robert; Richter, Nicole; Auer, Stefan; Eineder, Michael; Roth, Achim; Hajnsek, Irena; Walter, Diana; Braun, Matthias; Motagh, Mahdi; Pathe, Carsten; Pleskachevsky, Andrey; Thiel, Christian; Schmullius, Christiane

2013-04-01

Since the 1970s, radar remote sensing techniques have evolved rapidly and are increasingly employed in all fields of earth sciences. Applications are manifold and still expanding due to the continuous development of new instruments and missions as well as the availability of very high-quality data. The trend worldwide is towards operational employment of the various algorithms and methods that have been developed. However, the utilization of operational services does not keep up yet with the rate of technical developments and the improvements in sensor technology. With the enhancing availability and variety of space borne Synthetic Aperture Radar (SAR) data and a growing number of analysis algorithms the need for a vital user community is increasing. Therefore the German Aerospace Center (DLR) together with the Friedrich-Schiller-University Jena (FSU) and the Technical University Munich (TUM) launched the education initiative SAR-EDU. The aim of the project is to facilitate access to expert knowledge in the scientific field of radar remote sensing. Within this effort a web portal will be created to provide seminar material on SAR basics, methods and applications to support both, lecturers and students. The overall intension of the project SAR-EDU is to provide seminar material for higher education in radar remote sensing covering the topic holistically from the very basics to the most advanced methods and applications that are available. The principles of processing and interpreting SAR data are going to be taught using test data sets and open-source as well as commercial software packages. The material that is provided by SAR-EDU will be accessible at no charge from a DLR web portal. The educational tool will have a modular structure, consisting of separate modules that broach the issue of a particular topic. The aim of the implementation of SAR-EDU as application-oriented radar remote sensing educational tool is to advocate the development and wider use of

Airborne Radar Observations of Severe Hailstorms: Implications for Future Spaceborne Radar

NASA Technical Reports Server (NTRS)

Heymsfield, Gerald M.; Tian, Lin; Li, Lihua; McLinden, Matthew; Cervantes, Jaime I.

2013-01-01

A new dual-frequency (Ku and Ka band) nadir-pointing Doppler radar on the high-altitude NASA ER-2 aircraft, called the High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP), has collected data over severe thunderstorms in Oklahoma and Kansas during the Midlatitude Continental Convective Clouds Experiment (MC3E). The overarching motivation for this study is to understand the behavior of the dualwavelength airborne radar measurements in a global variety of thunderstorms and how these may relate to future spaceborne-radar measurements. HIWRAP is operated at frequencies that are similar to those of the precipitation radar on the Tropical Rainfall Measuring Mission (Ku band) and the upcoming Global Precipitation Measurement mission satellite's dual-frequency (Ku and Ka bands) precipitation radar. The aircraft measurements of strong hailstorms have been combined with ground-based polarimetric measurements to obtain a better understanding of the response of the Ku- and Ka-band radar to the vertical distribution of the hydrometeors, including hail. Data from two flight lines on 24 May 2011 are presented. Doppler velocities were approx. 39m/s2at 10.7-km altitude from the first flight line early on 24 May, and the lower value of approx. 25m/s on a second flight line later in the day. Vertical motions estimated using a fall speed estimate for large graupel and hail suggested that the first storm had an updraft that possibly exceeded 60m/s for the more intense part of the storm. This large updraft speed along with reports of 5-cm hail at the surface, reflectivities reaching 70 dBZ at S band in the storm cores, and hail signals from polarimetric data provide a highly challenging situation for spaceborne-radar measurements in intense convective systems. The Ku- and Ka-band reflectivities rarely exceed approx. 47 and approx. 37 dBZ, respectively, in these storms.

Preparation of nanosize polyaniline and its utilization for microwave absorber.

PubMed

Abbas, S M; Dixit, A K; Chatterjee, R; Goel, T C

2007-06-01

Polyaniline powder in nanosize has been synthesized by chemical oxidative route. XRD, FTIR, and TEM were used to characterize the polyaniline powder. Crytallite size was estimated from XRD profile and also ascertained by TEM in the range of 15 to 20 nm. The composite absorbers have been prepared by mixing different ratios of polyaniline into procured polyurethane (PU) binder. The complex permittivity (epsilon' - jepsilon") and complex permeability (mu' - jmu") were measured in X-band (8.2-12.4 GHz) using Agilent network analyzer (model PNA E8364B) and its software module 85071 (version 'E'). Measured values of these parameters were used to determine the reflection loss at different frequencies and sample thicknesses, based on a model of a single layered plane wave absorber backed by a perfect conductor. An optimized polyaniline/PU ratio of 3:1 has given a minimum reflection loss of -30 dB (99.9% power absorption) at the central frequency 10 GHz and the bandwidth (full width at half minimum) of 4.2 GHz over whole X-band (8.2 to 12.4 GHz) in a sample thickness of 3.0 mm. The prepared composites can be fruitfully utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).

Enhanced Weather Radar (EWxR) System

NASA Technical Reports Server (NTRS)

Kronfeld, Kevin M. (Technical Monitor)

2003-01-01

An airborne weather radar system, the Enhanced Weather Radar (EWxR), with enhanced on-board weather radar data processing was developed and tested. The system features additional weather data that is uplinked from ground-based sources, specialized data processing, and limited automatic radar control to search for hazardous weather. National Weather Service (NWS) ground-based Next Generation Radar (NEXRAD) information is used by the EWxR system to augment the on-board weather radar information. The system will simultaneously display NEXRAD and on-board weather radar information in a split-view format. The on-board weather radar includes an automated or hands-free storm-finding feature that optimizes the radar returns by automatically adjusting the tilt and range settings for the current altitude above the terrain and searches for storm cells near the atmospheric 0-degree isotherm. A rule-based decision aid was developed to automatically characterize cells as hazardous, possibly-hazardous, or non-hazardous based upon attributes of that cell. Cell attributes are determined based on data from the on-board radar and from ground-based radars. A flight path impact prediction algorithm was developed to help pilots to avoid hazardous weather along their flight plan and their mission. During development the system was tested on the NASA B757 aircraft and final tests were conducted on the Rockwell Collins Sabreliner.

Shock absorbing mount for electrical components

NASA Technical Reports Server (NTRS)

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

1975-01-01

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

Shallow radar (SHARAD) sounding observations of the Medusae Fossae Formation, Mars

USGS Publications Warehouse

Carter, L.M.; Campbell, B.A.; Watters, T.R.; Phillips, R.J.; Putzig, N.E.; Safaeinili, A.; Plaut, J.J.; Okubo, C.H.; Egan, A.F.; Seu, R.; Biccari, D.; Orosei, R.

2009-01-01

The SHARAD (shallow radar) sounding radar on the Mars Reconnaissance Orbiter detects subsurface reflections in the eastern and western parts of the Medusae Fossae Formation (MFF). The radar waves penetrate up to 580 m of the MFF and detect clear subsurface interfaces in two locations: west MFF between 150 and 155?? E and east MFF between 209 and 213?? E. Analysis of SHARAD radargrams suggests that the real part of the permittivity is ???3.0, which falls within the range of permittivity values inferred from MARSIS data for thicker parts of the MFF. The SHARAD data cannot uniquely determine the composition of the MFF material, but the low permittivity implies that the upper few hundred meters of the MFF material has a high porosity. One possibility is that the MFF is comprised of low-density welded or interlocked pyroclastic deposits that are capable of sustaining the steep-sided yardangs and ridges seen in imagery. The SHARAD surface echo power across the MFF is low relative to typical martian plains, and completely disappears in parts of the east MFF that correspond to the radar-dark Stealth region. These areas are extremely rough at centimeter to meter scales, and the lack of echo power is most likely due to a combination of surface roughness and a low near-surface permittivity that reduces the echo strength from any locally flat regions. There is also no radar evidence for internal layering in any of the SHARAD data for the MFF, despite the fact that tens-of-meters scale layering is apparent in infrared and visible wavelength images of nearby areas. These interfaces may not be detected in SHARAD data if their permittivity contrasts are low, or if the layers are discontinuous. The lack of closely spaced internal radar reflectors suggests that the MFF is not an equatorial analog to the current martian polar deposits, which show clear evidence of multiple internal layers in SHARAD data. ?? 2008 Elsevier Inc.

Historical aspects of radar atmospheric dynamics

NASA Technical Reports Server (NTRS)

Kato, Susumu

1989-01-01

A review of the history of radar techniques which have been applied to atmospheric observation is given. The author starts with ionosphere observation with the ionosonde, symbolizing as it does the earliest history of radar observation, and proceeds to later developments in radar observation such as the use of partial reflection, meteor, and incoherent scatter radars. Mesosphere stratosphere troposphere (MST) radars are discussed in terms of lower atmosphere observation.

Absorbent properties of carboxymethylated fiber, hydroentangled nonwoven and regenerated cellulose: a comparative study

USDA-ARS?s Scientific Manuscript database

Commercially-available, bleached cotton fibers, rayon, and their hydroentangled counterparts were carboxymethylated to produce cellulosic products with increased absorbency. These cellulose materials were tested for absorbance, spectroscopic properties, degree of substitution and carding ability. Ca...

Investigation into the energy-absorbing properties of multilayered circular thin-walled tube

NASA Astrophysics Data System (ADS)

Qi, Aidong; Liu, Chuanhua; Hu, Gongli; Gu, Hongjun

2002-05-01

With the rise in collision accident and the increase in requirement for resistance of blastproof structures in recent years, people attach much importance to the research and application of energy-absorbing device. In this paper the author calculates the specific strength, the specific hardness and ultimate internal force of a circular thin-walled tube by theoretic calculations, discusses the feasibility of using circular thin-walled tube as an energy-absorbing element, analyzes the energy-absorbing properties and the energy-absorbing mechanism through the energy-absorbing experiments using various materials and forms of arrangement, reaches the conclusion that the load-bearing capacity and energy-absorbing properties of multilayered tubes are superior to that of single tube, and puts forward the concept of 'grading tube'.

Radar Performance Improvement. Angle Tracking Modification to Fire Control Radar System for Space Shuttle Rendezvous

NASA Technical Reports Server (NTRS)

Little, G. R.

1976-01-01

The AN/APQ-153 fire control radar modified to provide angle tracking was evaluated for improved performance. The frequency agile modifications are discussed along with the range-rate improvement modifications, and the radar to computer interface. A parametric design and comparison of noncoherent and coherent radar systems are presented. It is shown that the shuttle rendezvous range and range-rate requirements can be made by a Ku-Band noncoherent pulse radar.

Reflection and Refraction of Light in Absorbing Media

NASA Astrophysics Data System (ADS)

Katsumata, Koichi; Sasaki, Shosuke

2018-05-01

The results of a rigorous calculation of optical phenomena in absorbing media based on Maxwell's equations are reported. In the case of an absorbing dielectric, we assume a complex dielectric constant. We find an expression for the angle of refraction as a function of the incident angle and the real and imaginary parts of the complex dielectric constant, all of which are real. The amplitudes of the reflected and transmitted waves are calculated on the same footing. These amplitudes are shown to be complex, from which we deduce the magnitude and phase change of the reflection and transmission coefficients. The same argument applies to an absorbing magnetic material if we replace the complex dielectric constant by a complex magnetic permeability.

Electromagnetic wave absorbing properties of amorphous carbon nanotubes.

PubMed

Zhao, Tingkai; Hou, Cuilin; Zhang, Hongyan; Zhu, Ruoxing; She, Shengfei; Wang, Jungao; Li, Tiehu; Liu, Zhifu; Wei, Bingqing

2014-07-10

Amorphous carbon nanotubes (ACNTs) with diameters in the range of 7-50 nm were used as absorber materials for electromagnetic waves. The electromagnetic wave absorbing composite films were prepared by a dip-coating method using a uniform mixture of rare earth lanthanum nitrate doped ACNTs and polyvinyl chloride (PVC). The microstructures of ACNTs and ACNT/PVC composites were characterized using transmission electron microscope and X-ray diffraction, and their electromagnetic wave absorbing properties were measured using a vector-network analyzer. The experimental results indicated that the electromagnetic wave absorbing properties of ACNTs are superior to multi-walled CNTs, and greatly improved by doping 6 wt% lanthanum nitrate. The reflection loss (R) value of a lanthanum nitrate doped ACNT/PVC composite was -25.02 dB at 14.44 GHz, and the frequency bandwidth corresponding to the reflector loss at -10 dB was up to 5.8 GHz within the frequency range of 2-18 GHz.

Consistency analysis and correction of ground-based radar observations using space-borne radar

NASA Astrophysics Data System (ADS)

Zhang, Shuai; Zhu, Yiqing; Wang, Zhenhui; Wang, Yadong

2018-04-01

The lack of an accurate determination of radar constant can introduce biases in ground-based radar (GR) reflectivity factor data, and lead to poor consistency of radar observations. The geometry-matching method was applied to carry out spatial matching of radar data from the Precipitation Radar (PR) on board the Tropical Rainfall Measuring Mission (TRMM) satellite to observations from a GR deployed at Nanjing, China, in their effective sampling volume, with 250 match-up cases obtained from January 2008 to October 2013. The consistency of the GR was evaluated with reference to the TRMM PR, whose stability is established. The results show that the below-bright-band-height data of the Nanjing radar can be split into three periods: Period I from January 2008 to March 2010, Period II from March 2010 to May 2013, and Period III from May 2013 to October 2013. There are distinct differences in overall reflectivity factor between the three periods, and the overall reflectivity factor in period II is smaller by a factor of over 3 dB than in periods I and III, although the overall reflectivity within each period remains relatively stable. Further investigation shows that in period II the difference between the GR and PR observations changed with echo intensity. A best-fit relation between the two radar reflectivity factors provides a linear correction that is applied to the reflectivity of the Nanjing radar, and which is effective in improving its consistency. Rain-gauge data were used to verify the correction, and the estimated precipitation based on the corrected GR reflectivity data was closer to the rain-gauge observations than that without correction.

Liquid Chromatography with Absorbance Detection and with Isotope-Dilution Mass Spectrometry for Determination of Isoflavones in Soy Standard Reference Materials

PubMed Central

Phillips, Melissa M.; Bedner, Mary; Gradl, Manuela; Burdette, Carolyn Q.; Nelson, Michael A.; Yen, James H.; Sander, Lane C.; Rimmer, Catherine A.

2017-01-01

Two independent analytical approaches, based on liquid chromatography with absorbance detection and liquid chromatography with mass spectrometric detection, have been developed for determination of isoflavones in soy materials. These two methods yield comparable results for a variety of soy-based foods and dietary supplements. Four Standard Reference Materials (SRMs) have been produced by the National Institute of Standards and Technology to assist the food and dietary supplement community in method validation and have been assigned values for isoflavone content using both methods. These SRMs include SRM 3234 Soy Flour, SRM 3236 Soy Protein Isolate, SRM 3237 Soy Protein Concentrate, and SRM 3238 Soy-Containing Solid Oral Dosage Form. A fifth material, SRM 3235 Soy Milk, was evaluated using the methods and found to be inhomogeneous for isoflavones and unsuitable for value assignment. PMID:27832301

A THz plasmonics perfect absorber and Fabry-Perot cavity mechanism (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhou, Jiangfeng; Bhattarai, Khagendra; Silva, Sinhara; Jeon, Jiyeon; Kim, Junoh; Lee, Sang Jun; Ku, Zahyun

2016-10-01

The plasmonic metamaterial perfect absorber (MPA) is a recently developed branch of metamaterial which exhibits nearly unity absorption within certain frequency range.[1-6] The optically thin MPA possesses characteristic features of angular-independence, high Q-factor and strong field localization that have inspired a wide range of applications including electromagnetic wave absorption,[3, 7, 8] spatial[6] and spectral[5] modulation of light,[9] selective thermal emission,[9] thermal detecting[10] and refractive index sensing for gas[11] and liquid[12, 13] targets. In this work, we demonstrate a MPA working at terahertz (THz) regime and characterize it using an ultrafast THz time-domain spectroscopy (THz-TDS). Our study reveal an ultra-thin Fabry-Perot cavity mechanism compared to the impedance matching mechanism widely adopted in previous study [1-6]. Our results also shows higher-order resonances when the cavities length increases. These higher order modes exhibits much larger Q-factor that can benefit potential sensing and imaging applications. [1] C. M. Watts, X. L. Liu, and W. J. Padilla, "Metamaterial Electromagnetic Wave Absorbers," Advanced Materials, vol. 24, pp. 98-120, Jun 19 2012. [2] M. Hedayati, F. Faupel, and M. Elbahri, "Review of Plasmonic Nanocomposite Metamaterial Absorber," Materials, vol. 7, pp. 1221-1248, 2014. [3] N. I. Landy, S. Sajuyigbe, J. J. Mock, D. R. Smith, and W. J. Padilla, "Perfect metamaterial absorber," Physical Review Letters, vol. 100, p. 207402, May 23 2008. [4] H. R. Seren, G. R. Keiser, L. Cao, J. Zhang, A. C. Strikwerda, K. Fan, et al., "Optically Modulated Multiband Terahertz Perfect Absorber," Advanced Optical Materials, vol. 2, pp. 1221-1226, 2014. [5] D. Shrekenhamer, J. Montoya, S. Krishna, and W. J. Padilla, "Four-Color Metamaterial Absorber THz Spatial Light Modulator," Advanced Optical Materials, vol. 1, pp. 905-909, 2013. [6] S. Savo, D. Shrekenhamer, and W. J. Padilla, "Liquid Crystal Metamaterial Absorber Spatial

Liquid chromatography with absorbance detection and with isotope-dilution mass spectrometry for determination of isoflavones in soy standard reference materials.

PubMed

Phillips, Melissa M; Bedner, Mary; Reitz, Manuela; Burdette, Carolyn Q; Nelson, Michael A; Yen, James H; Sander, Lane C; Rimmer, Catherine A

2017-02-01

Two independent analytical approaches, based on liquid chromatography with absorbance detection and liquid chromatography with mass spectrometric detection, have been developed for determination of isoflavones in soy materials. These two methods yield comparable results for a variety of soy-based foods and dietary supplements. Four Standard Reference Materials (SRMs) have been produced by the National Institute of Standards and Technology to assist the food and dietary supplement community in method validation and have been assigned values for isoflavone content using both methods. These SRMs include SRM 3234 Soy Flour, SRM 3236 Soy Protein Isolate, SRM 3237 Soy Protein Concentrate, and SRM 3238 Soy-Containing Solid Oral Dosage Form. A fifth material, SRM 3235 Soy Milk, was evaluated using the methods and found to be inhomogeneous for isoflavones and unsuitable for value assignment. Graphical Abstract Separation of six isoflavone aglycones and glycosides found in Standard Reference Material (SRM) 3236 Soy Protein Isolate.

A 10 cm Dual Frequency Doppler Weather Radar. Part I. The Radar System.

DTIC Science & Technology

1982-10-25

Evaluation System ( RAMCES )". The step attenuator required for this calibration can be programmed remotely, has low power and temperature coefficients, and...Control and Evaluation System". The Quality Assurance/Fault Location Network makes use of fault location techniques at critical locations in the radar and...quasi-con- tinuous monitoring of radar performance. The Radar Monitor, Control and Evaluation System provides for automated system calibration and

Radar data smoothing filter study

NASA Technical Reports Server (NTRS)

White, J. V.

1984-01-01

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

47 CFR 80.273 - Radar standards.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Radar standards. 80.273 Section 80.273... MARITIME SERVICES Equipment Authorization for Compulsory Ships § 80.273 Radar standards. (a) Radar... with radar must comply with the following standards (all incorporated by reference, see § 80.7): (1...

47 CFR 80.273 - Radar standards.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Radar standards. 80.273 Section 80.273... MARITIME SERVICES Equipment Authorization for Compulsory Ships § 80.273 Radar standards. (a) Radar... with radar must comply with the following standards (all incorporated by reference, see § 80.7): (1...

47 CFR 80.273 - Radar standards.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Radar standards. 80.273 Section 80.273... MARITIME SERVICES Equipment Authorization for Compulsory Ships § 80.273 Radar standards. (a) Radar... with radar must comply with the following standards (all incorporated by reference, see § 80.7): (1...

Analysis of ALTAIR 1998 Meteor Radar Data

NASA Technical Reports Server (NTRS)

Zinn, J.; Close, S.; Colestock, P. L.; MacDonell, A.; Loveland, R.

2011-01-01

II and III. The main point of this paper is to use these deceleration rate data, together with results from a computer model, to determine values of the quantities mPs 2 (the meteor mass times its material density squared); and further, by combining these m s 2 values with meteor mass estimates for the same set of meteors determined separately from measured radar scattering

Interception of LPI radar signals

NASA Astrophysics Data System (ADS)

Lee, Jim P.

1991-11-01

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 control, and power management that a radar may employ against current Electronic Warfare (EW) receivers. The general conclusion is that it is possible to design a LPI radar which is effective against current intercept EW receivers. LPI operation is most easily achieved at close ranges and against a target with a large radar cross section. The general system sensitivity requirement for the detection of current and projected LPI radars is found to be on the order of -100 dBmi which cannot be met by current EW receivers. Finally, three potential LPI receiver architectures, using channelized, superhet, and acousto-optic receivers with narrow RF and video bandwidths are discussed. They have shown some potential in terms of providing the sensitivity and capability in an environment where both conventional and LPI signals are present.

Modeling Radar Scattering by Planetary Regoliths for Varying Angles of Incidence

NASA Astrophysics Data System (ADS)

Prem, P.; Patterson, G. W.; Zimmerman, M. I.

2017-12-01

Bistatic radar observations can play an important role in characterizing the texture and composition of planetary regoliths. Multiple scattering within a closely-packed particulate medium, such as a regolith, can lead to a response referred to as the Coherent Backscatter Opposition Effect (CBOE), associated with an increase in the intensity of backscattered radiation and an increase in Circular Polarization Ratio (CPR) at small bistatic angles. The nature of the CBOE is thought to depend not only on regolith properties, but also on the angle of incidence (Mishchenko, 1992). The latter factor is of particular interest in light of recent radar observations of the Moon over a range of bistatic and incidence angles by the Mini-RF instrument (on board the Lunar Reconnaissance Orbiter), operating in bistatic mode with a ground-based transmitter at the Arecibo Observatory. These observations have led to some intriguing results that are not yet well-understood ­- for instance, the lunar South Polar crater Cabeus shows an elevated CPR at only some combinations of incidence angle/bistatic angle, a potential clue to the depth distribution of water ice at the lunar poles (Patterson et al., 2017). Our objective in this work is to develop a model for radar scattering by planetary regoliths that can assist in the interpretation of Mini-RF observations. We approach the problem by coupling the Multiple Sphere T-Matrix (MSTM) code of Mackowski and Mishchenko (2011) to a Monte Carlo radiative transfer model. The MSTM code is based on the solution of Maxwell's equations for the propagation of electromagnetic waves in the presence of a cluster of scattering/absorbing spheres, and can be used to model the scattering of radar waves by an aggregation of nominal regolith particles. The scattering properties thus obtained serve as input to the Monte Carlo model, which is used to simulate radar scattering at larger spatial scales. The Monte Carlo approach has the advantage of being able to

Energy-Absorbing, Lightweight Wheels

NASA Technical Reports Server (NTRS)

Waydo, Peter

2003-01-01

Improved energy-absorbing wheels are under development for use on special-purpose vehicles that must traverse rough terrain under conditions (e.g., extreme cold) in which rubber pneumatic tires would fail. The designs of these wheels differ from those of prior non-pneumatic energy-absorbing wheels in ways that result in lighter weights and more effective reduction of stresses generated by ground/wheel contact forces. These wheels could be made of metals and/or composite materials to withstand the expected extreme operating conditions. As shown in the figure, a wheel according to this concept would include an isogrid tire connected to a hub via spring rods. The isogrid tire would be a stiff, lightweight structure typically made of aluminum. The isogrid aspect of the structure would both impart stiffness and act as a traction surface. The hub would be a thin-walled body of revolution having a simple or compound conical or other shape chosen for structural efficiency. The spring rods would absorb energy and partially isolate the hub and the supported vehicle from impact loads. The general spring-rod configuration shown in the figure was chosen because it would distribute contact and impact loads nearly evenly around the periphery of the hub, thereby helping to protect the hub against damage that would otherwise be caused by large loads concentrated onto small portions of the hub.

46 CFR 130.310 - Radar.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Radar. 130.310 Section 130.310 Shipping COAST GUARD... EQUIPMENT AND SYSTEMS Navigational Equipment § 130.310 Radar. Each vessel of 100 or more gross tons must be fitted with a general marine radar in the pilothouse. ...

46 CFR 130.310 - Radar.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Radar. 130.310 Section 130.310 Shipping COAST GUARD... EQUIPMENT AND SYSTEMS Navigational Equipment § 130.310 Radar. Each vessel of 100 or more gross tons must be fitted with a general marine radar in the pilothouse. ...

46 CFR 130.310 - Radar.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Radar. 130.310 Section 130.310 Shipping COAST GUARD... EQUIPMENT AND SYSTEMS Navigational Equipment § 130.310 Radar. Each vessel of 100 or more gross tons must be fitted with a general marine radar in the pilothouse. ...

46 CFR 130.310 - Radar.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Radar. 130.310 Section 130.310 Shipping COAST GUARD... EQUIPMENT AND SYSTEMS Navigational Equipment § 130.310 Radar. Each vessel of 100 or more gross tons must be fitted with a general marine radar in the pilothouse. ...

46 CFR 130.310 - Radar.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Radar. 130.310 Section 130.310 Shipping COAST GUARD... EQUIPMENT AND SYSTEMS Navigational Equipment § 130.310 Radar. Each vessel of 100 or more gross tons must be fitted with a general marine radar in the pilothouse. ...

Radar Image of Galapagos Island

NASA Image and Video Library

1996-10-23

This is an image showing part of Isla Isabella in the western Galapagos Islands. It was taken by the L-band radar in HH polarization from the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar on the 40th orbit of NASA’s space shuttle Endeavour.

Low-Angle Radar Tracking

DTIC Science & Technology

1976-02-01

Transition from Specular Reflection to Diffuse Scattering. . . 10 Composition of the Electric-Field Vector as Seen at the Radar...r t (16) R • FIGURE P COMPOSITION OF THE ELECTRIC-FIELD VECTOR AS SEEN AT THE RADAR, R, IN FIG. 2. The electric field at the radar, E, is the sum...wavelengths in the VHP and UHF ranges even subsurface characteristics can be important. So in a field experiment one must be careful to measure

All-digital radar architecture

NASA Astrophysics Data System (ADS)

Molchanov, Pavlo A.

2014-10-01

All digital radar architecture requires exclude mechanical scan system. The phase antenna array is necessarily large because the array elements must be co-located with very precise dimensions and will need high accuracy phase processing system for aggregate and distribute T/R modules data to/from antenna elements. Even phase array cannot provide wide field of view. New nature inspired all digital radar architecture proposed. The fly's eye consists of multiple angularly spaced sensors giving the fly simultaneously thee wide-area visual coverage it needs to detect and avoid the threats around him. Fly eye radar antenna array consist multiple directional antennas loose distributed along perimeter of ground vehicle or aircraft and coupled with receiving/transmitting front end modules connected by digital interface to central processor. Non-steering antenna array allows creating all-digital radar with extreme flexible architecture. Fly eye radar architecture provides wide possibility of digital modulation and different waveform generation. Simultaneous correlation and integration of thousands signals per second from each point of surveillance area allows not only detecting of low level signals ((low profile targets), but help to recognize and classify signals (targets) by using diversity signals, polarization modulation and intelligent processing. Proposed all digital radar architecture with distributed directional antenna array can provide a 3D space vector to the jammer by verification direction of arrival for signals sources and as result jam/spoof protection not only for radar systems, but for communication systems and any navigation constellation system, for both encrypted or unencrypted signals, for not limited number or close positioned jammers.

Absorption-induced scattering and surface plasmon out-coupling from absorber-coated plasmonic metasurfaces

PubMed Central

Petoukhoff, Christopher E.; O'Carroll, Deirdre M.

2015-01-01

Interactions between absorbers and plasmonic metasurfaces can give rise to unique optical properties not present for either of the individual materials and can influence the performance of a host of optical sensing and thin-film optoelectronic applications. Here we identify three distinct mode types of absorber-coated plasmonic metasurfaces: localized and propagating surface plasmons and a previously unidentified optical mode type called absorption-induced scattering. The extinction of the latter mode type can be tuned by controlling the morphology of the absorber coating and the spectral overlap of the absorber with the plasmonic modes. Furthermore, we show that surface plasmons are backscattered when the crystallinity of the absorber is low but are absorbed for more crystalline absorber coatings. This work furthers our understanding of light–matter interactions between absorbers and surface plasmons to enable practical optoelectronic applications of metasurfaces. PMID:26271900

Jupiter Trojan's Shallow Subsurface: Direct Observation By Radar Sounding

NASA Astrophysics Data System (ADS)

Herique, A.; Plettemeier, D.; Beck, P.; Michel, P.; Kumamoto, A.; Kofman, W. W.

2017-12-01

Most of the Jupiter's Trojan are classified as spectral type P or D from visible and near-IR observations. Still, major question remain regarding theire origin and geological evolution: What ices are present in their interior, and in what amount? What is the abundance and the nature of the organic fraction? Did they experience some level of differentiation powered by 26Al? Answering theses question is the goal of the Solar-Power Sail JAXA mission [1, 2]. This mission plans to study the surface by remote sensing in the optical in IR domain. This probe will carry a large-sized lander with a drill to sample the constitutive material at meter depth in order to complement physical and chemical properties measured by on-board instruments. The sample return is an option under study.Radar sounding of the shallow subsurface would be envisaged in complement to this payload. Sounding radar could provide the structure of the first tens of meters of the Trojan surface. It will allow identifying layering, ice lens, and embedded block. It also will enable to reconnect the surface with the deep interior in order to identify exogenous / pristine material. For the surface package, the drilling and the sample return, radar sounding is a unique opportunity to support the selection of the landing site and to provide the greater geological context of the samples that will be returned to Earth.In this paper, we will detail the objective of this instrument and then we will outline the proposed instrument, which is inheriting from the radar developed for the AIDA/AIM mission.[1] Mori, O. et al., Science experiments on a Jupiter Trojan Asteroid in the solar powerd sail mission. LPSC 2016 - 1822.[2] Okada, T. et al., Science and Exploration of a Jupiter Trojan Asteroid in the solar-power sail mission. LPSC 2017 - 1828.

Analysis of Borehole-Radar Reflection Data from Machiasport, Maine, December 2003

USGS Publications Warehouse

Johnson, Carole D.; Joesten, Peter K.

2005-01-01

In December 2003, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, collected borehole-radar reflection logs in two boreholes in Machiasport, Maine. These bedrock boreholes were drilled as part of a hydrogeologic investigation of the area surrounding the former Air Force Radar Tracking Station site on Howard Mountain near Bucks Harbor. The boreholes, MW09 and MW10, are located approximately 50 meters (m) from, and at the site of, respectively, the locations of former buildings where trichloroethylene was used as part of defense-site operations. These areas are thought to be potential source areas for contamination that has been detected in downgradient bedrock wells. This investigation focused on testing borehole-radar methods at this site. Single-hole radar-reflection surveys were used to identify the depth, orientation, and spatial continuity of reflectors that intersect and surround the boreholes. In addition, the methods were used to (1) identify the radial depth of penetration of the radar waves in the electrically resistive bimodal volcanic formation at the site, (2) provide information for locating additional boreholes at the site, and (3) test the potential applications of borehole-radar methods for further aquifer characterization and (or) evaluation of source-area remediation efforts. Borehole-radar reflection logging uses a pair of downhole transmitting and receiving antennas to record the reflected wave amplitude and transit time of high-frequency electromagnetic waves. For this investigation, 60- and 100-megahertz antennas were used. The electromagnetic waves emitted by the transmitter penetrate into the formation surrounding the borehole and are reflected off of a material with different electromagnetic properties, such as a fracture or change in rock type. Single-hole directional radar surveys indicate the bedrock surrounding these boreholes is highly fractured, because several reflectors were identified in the radar

Comparison of radar data versus rainfall data

PubMed Central

Espinosa, B.; Hromadka, T.V.; Perez, R.

2015-01-01

Doppler radar data are increasingly used in rainfall-runoff synthesis studies, perhaps due to radar data availability, among other factors. However, the veracity of the radar data are often a topic of concern. In this paper, three Doppler radar outcomes developed by the United States National Weather Service at three radar sites are examined and compared to actual rain gage data for two separate severe storm events in order to assess accuracy in the published radar estimates of rainfall. Because the subject storms were very intense rainfall events lasting approximately one hour in duration, direct comparisons between the three radar gages themselves can be made, as well as a comparison to rain gage data at a rain gage location subjected to the same storm cells. It is shown that topographic interference with the radar outcomes can be a significant factor leading to differences between radar and rain gage readings, and that care is needed in calibrating radar outcomes using available rain gage data in order to interpolate rainfall estimates between rain gages using the spatial variation observed in the radar readings. The paper establishes and describes•the need for “ground-truthing” of radar data, and•possible errors due to topographic interference. PMID:26649276

Classification and correction of the radar bright band with polarimetric radar

NASA Astrophysics Data System (ADS)

Hall, Will; Rico-Ramirez, Miguel; Kramer, Stefan

2015-04-01

The annular region of enhanced radar reflectivity, known as the Bright Band (BB), occurs when the radar beam intersects a layer of melting hydrometeors. Radar reflectivity is related to rainfall through a power law equation and so this enhanced region can lead to overestimations of rainfall by a factor of up to 5, so it is important to correct for this. The BB region can be identified by using several techniques including hydrometeor classification and freezing level forecasts from mesoscale meteorological models. Advances in dual-polarisation radar measurements and continued research in the field has led to increased accuracy in the ability to identify the melting snow region. A method proposed by Kitchen et al (1994), a form of which is currently used operationally in the UK, utilises idealised Vertical Profiles of Reflectivity (VPR) to correct for the BB enhancement. A simpler and more computationally efficient method involves the formation of an average VPR from multiple elevations for correction that can still cause a significant decrease in error (Vignal 2000). The purpose of this research is to evaluate a method that relies only on analysis of measurements from an operational C-band polarimetric radar without the need for computationally expensive models. Initial results show that LDR is a strong classifier of melting snow with a high Critical Success Index of 97% when compared to the other variables. An algorithm based on idealised VPRs resulted in the largest decrease in error when BB corrected scans are compared to rain gauges and to lower level scans with a reduction in RMSE of 61% for rain-rate measurements. References Kitchen, M., R. Brown, and A. G. Davies, 1994: Real-time correction of weather radar data for the effects of bright band, range and orographic growth in widespread precipitation. Q.J.R. Meteorol. Soc., 120, 1231-1254. Vignal, B. et al, 2000: Three methods to determine profiles of reflectivity from volumetric radar data to correct

Coherent Laser Radar System Theory.

DTIC Science & Technology

1987-11-05

This program is aimed at developing a system theory for the emerging technology of multifunction coherent CO2 laser radars. It builds upon previous...work funded by U.S. Army Research Office contract DAAG29-80-K-0022. Keywords include: Laser radar theory, Radar system theory , and Laser speckle.

Study of earth abundant tco and absorber materials for photovoltaic applications

NASA Astrophysics Data System (ADS)

Prabhakar, Tejas

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

Recommendation on transition from primary/secondary radar to secondary-only radar capability

DOT National Transportation Integrated Search

1994-10-01

This recommendation has been prepared to support the FAA decision to deactivate primary Long-range radars and presents a : transition strategy and implementation plan for the transformation of the existing primary/secondary en route radar : system to...

Current radar-responsive tag development activities at Sandia National Laboratories

NASA Astrophysics Data System (ADS)

Ormesher, Richard C.; Plummer, Kenneth W.; Wells, Lars M.

2004-08-01

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

Evaluation of meteorological airborne Doppler radar

NASA Technical Reports Server (NTRS)

Hildebrand, P. H.; Mueller, C. K.

1984-01-01

This paper will discuss the capabilities of airborne Doppler radar for atmospheric sciences research. The evaluation is based on airborne and ground based Doppler radar observations of convective storms. The capability of airborne Doppler radar to measure horizontal and vertical air motions is evaluated. Airborne Doppler radar is shown to be a viable tool for atmospheric sciences research.

46 CFR 184.404 - Radars.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Radars. 184.404 Section 184.404 Shipping COAST GUARD... MISCELLANEOUS SYSTEMS AND EQUIPMENT Navigation Equipment § 184.404 Radars. (a) A vessel must be fitted with a Federal Communications Commission (FCC) type accepted general marine radar system for surface navigation...

46 CFR 184.404 - Radars.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Radars. 184.404 Section 184.404 Shipping COAST GUARD... MISCELLANEOUS SYSTEMS AND EQUIPMENT Navigation Equipment § 184.404 Radars. (a) A vessel must be fitted with a Federal Communications Commission (FCC) type accepted general marine radar system for surface navigation...

46 CFR 184.404 - Radars.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Radars. 184.404 Section 184.404 Shipping COAST GUARD... MISCELLANEOUS SYSTEMS AND EQUIPMENT Navigation Equipment § 184.404 Radars. (a) A vessel must be fitted with a Federal Communications Commission (FCC) type accepted general marine radar system for surface navigation...

46 CFR 184.404 - Radars.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Radars. 184.404 Section 184.404 Shipping COAST GUARD... MISCELLANEOUS SYSTEMS AND EQUIPMENT Navigation Equipment § 184.404 Radars. (a) A vessel must be fitted with a Federal Communications Commission (FCC) type accepted general marine radar system for surface navigation...

46 CFR 184.404 - Radars.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Radars. 184.404 Section 184.404 Shipping COAST GUARD... MISCELLANEOUS SYSTEMS AND EQUIPMENT Navigation Equipment § 184.404 Radars. (a) A vessel must be fitted with a Federal Communications Commission (FCC) type accepted general marine radar system for surface navigation...

Ground-penetrating radar research in Belgium: from developments to applications

NASA Astrophysics Data System (ADS)

Lambot, Sébastien; Van Meirvenne, Marc; Craeye, Christophe

2014-05-01

Ground-penetrating radar research in Belgium spans a series of developments and applications, including mainly ultra wideband radar antenna design and optimization, non-destructive testing for the characterization of the electrical properties of soils and materials, and high-resolution subsurface imaging in agricultural engineering, archeology and transport infrastructures (e.g., road inspection and pipe detection). Security applications have also been the topic of active research for several years (i.e., landmine detection) and developments in forestry have recently been initiated (i.e., for root zone and tree trunk imaging and characterization). In particular, longstanding research has been devoted to the intrinsic modeling of antenna-medium systems for full-wave inversion, thereby providing an effective way for retrieving the electrical properties of soils and materials. Full-wave modeling is a prerequisite for benefiting from the full information contained in the radar data and is necessary to provide robust and accurate estimates of the properties of interest. Nevertheless, this has remained a major challenge in geophysics and electromagnetics for many years, mainly due to the complex interactions between the antennas and the media as well as to the significant computing resources that are usually required. Efforts have also been dedicated to the development of specific inversion strategies to cope with the complexity of the inverse problems usually dealt with as well as ill-posedness issues that arise from a lack of information in the radar data. To circumvent this last limitation, antenna arrays have been developed and modeled in order to provide additional information. Moreover, data fusion ways have been investigated, by mainly combining GPR data with electromagnetic induction complementary information in joint interpretation analyses and inversion procedures. Finally, inversions have been regularized by combining electromagnetics models together with soil

Advanced Borehole Radar for Hydrogeology

NASA Astrophysics Data System (ADS)

Sato, M.

2014-12-01

Ground Penetrating Radar is a useful tool for monitoring the hydrogeological environment. We have developed GPR systems which can be applied to these purposes, and we will demonstrate examples borehole radar measurements. In order to have longer radar detection range, frequency lower than100MHz has been normally adopted in borehole radar. Typical subsurface fractures of our interests have a few mm aperture and radar resolution is much poorer than a few cm in this frequency range. We are proposing and demonstrating to use radar polarimetry to solve this problem. We have demonstrated that a full-polarimetry borehole radar can be used for characterization of subsurface fractures. Together with signal processing for antenna characteristic compensation to equalize the signal by a dipole antenna and slot antennas, we could demonstrate that polarimetric borehole radar can estimate the surface roughness of subsurface fractures, We believe the surface roughness is closely related to water permeability through the fractures. We then developed a directional borehole radar, which uses optical field sensor. A dipole antenna in a borehole has omni-directional radiation pattern, and we cannot get azimuthal information about the scatterers. We use multiple dipole antennas set around the borehole axis, and from the phase differences, we can estimate the 3-diemnational orientation of subsurface structures. We are using optical electric field sensor for receiver of borehole radar. This is a passive sensor and connected only with optical fibers and does not require any electric power supply to operate the receiver. It has two major advantages; the first one is that the receiver can be electrically isolated from other parts, and wave coupling to a logging cable is avoided. Then, secondary, it can operate for a long time, because it does not require battery installed inside the system. It makes it possible to set sensors in fixed positions to monitor the change of environmental

Radar network communication through sensing of frequency hopping

DOEpatents

Dowla, Farid; Nekoogar, Faranak

2013-05-28

In one embodiment, a radar communication system includes a plurality of radars having a communication range and being capable of operating at a sensing frequency and a reporting frequency, wherein the reporting frequency is different than the sensing frequency, each radar is adapted for operating at the sensing frequency until an event is detected, each radar in the plurality of radars has an identification/location frequency for reporting information different from the sensing frequency, a first radar of the radars which senses the event sends a reporting frequency corresponding to its identification/location frequency when the event is detected, and all other radars in the plurality of radars switch their reporting frequencies to match the reporting frequency of the first radar upon detecting the reporting frequency switch of a radar within the communication range. In another embodiment, a method is presented for communicating information in a radar system.

Sensor management in RADAR/IRST track fusion

NASA Astrophysics Data System (ADS)

Hu, Shi-qiang; Jing, Zhong-liang

2004-07-01

In this paper, a novel radar management strategy technique suitable for RADAR/IRST track fusion, which is based on Fisher Information Matrix (FIM) and fuzzy stochastic decision approach, is put forward. Firstly, optimal radar measurements' scheduling is obtained by the method of maximizing determinant of the Fisher information matrix of radar and IRST measurements, which is managed by the expert system. Then, suggested a "pseudo sensor" to predict the possible target position using the polynomial method based on the radar and IRST measurements, using "pseudo sensor" model to estimate the target position even if the radar is turned off. At last, based on the tracking performance and the state of target maneuver, fuzzy stochastic decision is used to adjust the optimal radar scheduling and retrieve the module parameter of "pseudo sensor". The experiment result indicates that the algorithm can not only limit Radar activity effectively but also keep the tracking accuracy of active/passive system well. And this algorithm eliminates the drawback of traditional Radar management methods that the Radar activity is fixed and not easy to control and protect.

Radar data processing and analysis

NASA Technical Reports Server (NTRS)

Ausherman, D.; Larson, R.; Liskow, C.

1976-01-01

Digitized four-channel radar images corresponding to particular areas from the Phoenix and Huntington test sites were generated in conjunction with prior experiments performed to collect X- and L-band synthetic aperture radar imagery of these two areas. The methods for generating this imagery are documented. A secondary objective was the investigation of digital processing techniques for extraction of information from the multiband radar image data. Following the digitization, the remaining resources permitted a preliminary machine analysis to be performed on portions of the radar image data. The results, although necessarily limited, are reported.

Ultra-wideband radar motion sensor

DOEpatents

McEwan, Thomas E.

1994-01-01

A motion sensor is based on ultra-wideband (UWB) radar. UWB radar range is determined by a pulse-echo interval. For motion detection, the sensors operate by staring at a fixed range and then sensing any change in the averaged radar reflectivity at that range. A sampling gate is opened at a fixed delay after the emission of a transmit pulse. The resultant sampling gate output is averaged over repeated pulses. Changes in the averaged sampling gate output represent changes in the radar reflectivity at a particular range, and thus motion.

Ultra-wideband radar motion sensor

DOEpatents

McEwan, T.E.

1994-11-01

A motion sensor is based on ultra-wideband (UWB) radar. UWB radar range is determined by a pulse-echo interval. For motion detection, the sensors operate by staring at a fixed range and then sensing any change in the averaged radar reflectivity at that range. A sampling gate is opened at a fixed delay after the emission of a transmit pulse. The resultant sampling gate output is averaged over repeated pulses. Changes in the averaged sampling gate output represent changes in the radar reflectivity at a particular range, and thus motion. 15 figs.

Applications of high-frequency radar

NASA Astrophysics Data System (ADS)

Headrick, J. M.; Thomason, J. F.

1998-07-01

Efforts to extend radar range by an order of magnitude with use of the ionosphere as a virtual mirror started after the end of World War II. A number of HF radar programs were pursued, with long-range nuclear burst and missile launch detection demonstrated by 1956. Successful east coast radar aircraft detect and track tests extending across the Atlantic were conducted by 1961. The major obstacles to success, the large target-to-clutter ratio and low signal-to-noise ratio, were overcome with matched filter Doppler processing. To search the areas that a 2000 nautical mile (3700 km) radar can reach, very complex and high dynamic range processing is required. The spectacular advances in digital processing technology have made truly wide-area surveillance possible. Use of the surface attached wave over the oceans can enable HF radar to obtain modest extension of range beyond the horizon. The decameter wavelengths used by both skywave and surface wave radars require large physical antenna apertures, but they have unique capabilities for air and surface targets, many of which are of resonant scattering dimensions. Resonant scattering from the ocean permits sea state and direction estimation. Military and commercial applications of HF radar are in their infancy.

Acoustic Properties of Absorbent Asphalts

NASA Astrophysics Data System (ADS)

Trematerra, Amelia; Lombardi, Ilaria

2017-08-01

Road traffic is one of the greater cause of noise pollution in urban centers; a prolonged exposure to this source of noise disturbs populations subjected to it. In this paper is reported a study on the absorbent coefficients of asphalt. The acoustic measurements are carried out with a impedance tube (tube of Kundt). The sample are measured in three conditions: with dry material (traditional), “wet” asphalt and “dirty” asphalt.

Effects of increased collagen-matrix density on the mechanical properties and in vivo absorbability of hydroxyapatite-collagen composites as artificial bone materials.

PubMed

Yunoki, Shunji; Sugiura, Hiroaki; Ikoma, Toshiyuki; Kondo, Eiji; Yasuda, Kazunori; Tanaka, Junzo

2011-02-01

The aim of this study was to evaluate the effects of increased collagen-matrix density on the mechanical properties and in vivo absorbability of porous hydroxyapatite (HAp)-collagen composites as artificial bone materials. Seven types of porous HAp-collagen composites were prepared from HAp nanocrystals and dense collagen fibrils. Their densities and HAp/collagen weight ratios ranged from 122 to 331 mg cm⁻³ and from 20/80 to 80/20, respectively. The flexural modulus and strength increased with an increase in density, reaching 2.46 ± 0.48 and 0.651 ± 0.103 MPa, respectively. The porous composites with a higher collagen-matrix density exhibited much higher mechanical properties at the same densities, suggesting that increasing the collagen-matrix density is an effective way of improving the mechanical properties. It was also suggested that other structural factors in addition to collagen-matrix density are required to achieve bone-like mechanical properties. The in vivo absorbability of the composites was investigated in bone defects of rabbit femurs, demonstrating that the absorption rate decreased with increases in the composite density. An exhaustive increase in density is probably limited by decreases in absorbability as artificial bones.

Shuttle Imaging Radar - Geologic applications

NASA Technical Reports Server (NTRS)

Macdonald, H.; Bridges, L.; Waite, W.; Kaupp, V.

1982-01-01

The Space Shuttle, on its second flight (November 12, 1981), carried the first science and applications payload which provided an early demonstration of Shuttle's research capabilities. One of the experiments, the Shuttle Imaging Radar-A (SIR-A), had as a prime objective to evaluate the capability of spaceborne imaging radars as a tool for geologic exploration. The results of the experiment will help determine the value of using the combination of space radar and Landsat imagery for improved geologic analysis and mapping. Preliminary analysis of the Shuttle radar imagery with Seasat and Landsat imagery from similar areas provides evidence that spaceborne radars can significantly complement Landsat interpretation, and vastly improve geologic reconnaissance mapping in those areas of the world that are relatively unmapped because of perpetual cloud cover.

Bayesian characterization of micro-perforated panels and multi-layer absorbers

NASA Astrophysics Data System (ADS)

Schmitt, Andrew Alexander Joseph

First described by the late acoustician Dah-You Maa, micro-perforated panel (MPP) absorbers produce extremely high acoustic absorption coefficients. This is done without the use of conventional fibrous or porous materials that are often used in acoustic treatments, meaning MPP absorbers are capable of being implemented and withstanding critical situations where traditional absorbers do not suffice. The absorption function of a micro-perforated panel yields high yet relatively narrow results at certain frequencies, although wide-band absorption can be designed by stacking multiple MPP absorbers comprised of different characteristic parameters. Using Bayesian analysis, the physical properties of panel thickness, pore diameter, perforation ratio, and air depth are estimated inversely from experimental data of acoustic absorption, based on theoretical models for design of micro-perforated panels. Furthermore, this analysis helps to understand the interdependence and uncertainties of the parameters and how each affects the performance of the panel. Various micro-perforated panels are manufactured and tested in single- and double-layer absorber constructions.

Midwavelength interband cascade infrared photodetectors with superlattice absorbers and gain

NASA Astrophysics Data System (ADS)

Lei, Lin; Li, Lu; Lotfi, Hossein; Ye, Hao; Yang, Rui Q.; Mishima, Tetsuya D.; Santos, Michael B.; Johnson, Matthew B.

2018-01-01

We report on a comparison study of the electrical and optical properties of a set of device structures with different numbers of cascade stages, type-II superlattice (T2SL) absorber thickness, and doping variations, as well as a noncurrent-matched interband cascade infrared photodetectors (ICIP) structure with equal absorbers. Multistage ICIPs were demonstrated to be capable of operating at high temperatures at zero-bias with superior carrier transport over comparable conventional one-stage detectors. Based on the temperature dependence and bias sensitivity of their responsivities with various absorber thicknesses, the diffusion length is estimated to be between 0.6 and 1.0 μm for T2SL materials at high temperatures (>250 K). A comparison of responsivities between current matched ICIPs with varied absorber thicknesses and noncurrent-matched ICIPs with equal absorbers shows that the current-matching among cascade stages is necessary to maximize responsivity. Additionally, electrical gain exceeding unity is demonstrated in these detectors in the reverse-illumination configuration.

The PROUST radar

NASA Technical Reports Server (NTRS)

Bertin, F.; Glass, M.; Ney, R.; Petitdidier, M.

1986-01-01

The Stratosphere-Troposphere (ST) radar called PROUST works at 935 MHz using the same klystron and antenna as the coherent-scatter radar. The use of this equipment for ST work has required some important modifications of the transmitting system and the development of receiving, data processing and acquisition (1984,1985) equipment. The modifications are discussed.

Novel quad-band terahertz metamaterial absorber based on single pattern U-shaped resonator

NASA Astrophysics Data System (ADS)

Wang, Ben-Xin; Wang, Gui-Zhen

2017-03-01

A novel quad-band terahertz metamaterial absorber using four different modes of single pattern resonator is demonstrated. Four obvious frequencies with near-perfect absorption are realized. Near-field distributions of the four modes are provided to reveal the physical picture of the multiple-band absorption. Unlike most previous quad-band absorbers that typically require four or more patterns, the designed absorber has only one resonant structure, which is simpler than previous works. The presented quad-band absorber has potential applications in biological sensing, medical imaging, and material detection.

Radar-aeolian roughness project

NASA Technical Reports Server (NTRS)

Greeley, Ronald; Dobrovolskis, A.; Gaddis, L.; Iversen, J. D.; Lancaster, N.; Leach, Rodman N.; Rasnussen, K.; Saunders, S.; Vanzyl, J.; Wall, S.

1991-01-01

The objective is to establish an empirical relationship between measurements of radar, aeolian, and surface roughness on a variety of natural surfaces and to understand the underlying physical causes. This relationship will form the basis for developing a predictive equation to derive aeolian roughness from radar backscatter. Results are given from investigations carried out in 1989 on the principal elements of the project, with separate sections on field studies, radar data analysis, laboratory simulations, and development of theory for planetary applications.

Impact of frequency and polarization diversity on a terahertz radar's imaging performance

NASA Astrophysics Data System (ADS)

Cooper, Ken B.; Dengler, Robert J.; Llombart, Nuria

2011-05-01

The Jet Propulsion Laboratory's 675 GHz, 25 m standoff imaging radar can achieve >1 Hz real time frame rates over 40x40 cm fields of view for rapid detection of person-borne concealed weapons. In its normal mode of operation, the radar generates imagery based solely on the time-of-flight, or range, between the radar and target. With good clothing penetration at 675 GHz, a hidden object will be detectable as an anomaly in the range-to-surface profile of a subject. Here we report on results of two modifications in the radar system that were made to asses its performance using somewhat different detection approaches. First, the radar's operating frequency and bandwidth were cut in half, to 340 GHz and 13 GHz, where there potential system advantages include superior transmit power and clothing penetration, as well as a lower cost of components. In this case, we found that the twofold reduction in range and cross-range resolution sharply limited the quality of through-clothes imagery, although some improvement is observed for detection of large targets concealed by very thick clothing. The second radar modification tested involved operation in a fully polarimetric mode, where enhanced image contrast might occur between surfaces with different material or geometric characteristics. Results from these tests indicated that random speckle dominates polarimetric power imagery, making it an unattractive approach for contrast improvement. Taken together, the experiments described here underscore the primary importance of high resolution imaging in THz radar applications for concealed weapons detection.

Estimating Lunar Pyroclastic Deposit Depth from Imaging Radar Data: Applications to Lunar Resource Assessment

NASA Technical Reports Server (NTRS)

Campbell, B. A.; Stacy, N. J.; Campbell, D. B.; Zisk, S. H.; Thompson, T. W.; Hawke, B. R.

1992-01-01

Lunar pyroclastic deposits represent one of the primary anticipated sources of raw materials for future human settlements. These deposits are fine-grained volcanic debris layers produced by explosive volcanism contemporaneous with the early stage of mare infilling. There are several large regional pyroclastic units on the Moon (for example, the Aristarchus Plateau, Rima Bode, and Sulpicius Gallus formations), and numerous localized examples, which often occur as dark-halo deposits around endogenic craters (such as in the floor of Alphonsus Crater). Several regional pyroclastic deposits were studied with spectral reflectance techniques: the Aristarchus Plateau materials were found to be a relatively homogeneous blanket of iron-rich glasses. One such deposit was sampled at the Apollo 17 landing site, and was found to have ferrous oxide and titanium dioxide contents of 12 percent and 5 percent, respectively. While the areal extent of these deposits is relatively well defined from orbital photographs, their depths have been constrained only by a few studies of partially filled impact craters and by imaging radar data. A model for radar backscatter from mantled units applicable to both 70-cm and 12.6-cm wavelength radar data is presented. Depth estimates from such radar observations may be useful in planning future utilization of lunar pyroclastic deposits.

Design of a five-band terahertz perfect metamaterial absorber using two resonators

NASA Astrophysics Data System (ADS)

Meng, Tianhua; Hu, Dan; Zhu, Qiaofen

2018-05-01

We present a polarization-insensitive five-band terahertz perfect metamaterial absorber composed of two metallic circular rings and a metallic ground film separated by a dielectric layer. The calculated results show that the absorber has five distinctive absorption bands whose peaks are greater than 99% on average. The physical origin of the absorber originates from the combination of dipolar, hexapolar, and surface plasmon resonance of the patterned metallic structure, which is different from the work mechanism of previously reported absorbers. In addition, the influence of the structural parameters on the absorption spectra is analyzed to further confirm the origin of the five-band absorption peaks. The proposed absorber has potential applications in terahertz imaging, refractive index sensing, and material detecting.

Analysis of Active Lava Flows on Kilauea Volcano, Hawaii, Using SIR-C Radar Correlation Measurements

NASA Technical Reports Server (NTRS)

Zebker, H. A.; Rosen, P.; Hensley, S.; Mouginis-Mark, P. J.

1995-01-01

Precise eruption rates of active pahoehoe lava flows on Kilauea volcano, Hawaii, have been determined using spaceborne radar data acquired by the Space Shuttle Imaging Radar-C (SIR-C). Measurement of the rate of lava flow advance, and the determination of the volume of new material erupted in a given period of time, are among the most important observations that can be made when studying a volcano.

Electromagnetic Wave Absorbing Properties of Amorphous Carbon Nanotubes

PubMed Central

Zhao, Tingkai; Hou, Cuilin; Zhang, Hongyan; Zhu, Ruoxing; She, Shengfei; Wang, Jungao; Li, Tiehu; Liu, Zhifu; Wei, Bingqing

2014-01-01

Amorphous carbon nanotubes (ACNTs) with diameters in the range of 7–50 nm were used as absorber materials for electromagnetic waves. The electromagnetic wave absorbing composite films were prepared by a dip-coating method using a uniform mixture of rare earth lanthanum nitrate doped ACNTs and polyvinyl chloride (PVC). The microstructures of ACNTs and ACNT/PVC composites were characterized using transmission electron microscope and X-ray diffraction, and their electromagnetic wave absorbing properties were measured using a vector-network analyzer. The experimental results indicated that the electromagnetic wave absorbing properties of ACNTs are superior to multi-walled CNTs, and greatly improved by doping 6 wt% lanthanum nitrate. The reflection loss (R) value of a lanthanum nitrate doped ACNT/PVC composite was −25.02 dB at 14.44 GHz, and the frequency bandwidth corresponding to the reflector loss at −10 dB was up to 5.8 GHz within the frequency range of 2–18 GHz. PMID:25007783

46 CFR 108.717 - Radar.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Radar. 108.717 Section 108.717 Shipping COAST GUARD... Miscellaneous Equipment § 108.717 Radar. Each self-propelled unit of 1,600 gross tons and over in ocean or coastwise service must have— (a) A marine radar system for surface navigation; and (b) Facilities on the...

46 CFR 108.717 - Radar.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Radar. 108.717 Section 108.717 Shipping COAST GUARD... Miscellaneous Equipment § 108.717 Radar. Each self-propelled unit of 1,600 gross tons and over in ocean or coastwise service must have— (a) A marine radar system for surface navigation; and (b) Facilities on the...

46 CFR 108.717 - Radar.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Radar. 108.717 Section 108.717 Shipping COAST GUARD... Miscellaneous Equipment § 108.717 Radar. Each self-propelled unit of 1,600 gross tons and over in ocean or coastwise service must have— (a) A marine radar system for surface navigation; and (b) Facilities on the...

46 CFR 108.717 - Radar.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Radar. 108.717 Section 108.717 Shipping COAST GUARD... Miscellaneous Equipment § 108.717 Radar. Each self-propelled unit of 1,600 gross tons and over in ocean or coastwise service must have— (a) A marine radar system for surface navigation; and (b) Facilities on the...

46 CFR 108.717 - Radar.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Radar. 108.717 Section 108.717 Shipping COAST GUARD... Miscellaneous Equipment § 108.717 Radar. Each self-propelled unit of 1,600 gross tons and over in ocean or coastwise service must have— (a) A marine radar system for surface navigation; and (b) Facilities on the...

Nanostructured materials for hydrogen storage

DOEpatents

Williamson, Andrew J.; Reboredo, Fernando A.

2007-12-04

A system for hydrogen storage comprising a porous nano-structured material with hydrogen absorbed on the surfaces of the porous nano-structured material. The system of hydrogen storage comprises absorbing hydrogen on the surfaces of a porous nano-structured semiconductor material.

Optimization of the acoustic absorption coefficients of certain functional absorbents

NASA Technical Reports Server (NTRS)

Pocsa, V.; Biborosch, L.; Veres, A.; Halpert, E.; Lorian, R.; Botos, T.

1974-01-01

The sound absorption coefficients of some functional absorbents (mineral wool plates) are determined by the reverberation chamber method. The influence of the angle of inclination of the sound absorbing material with respect to the surface to be treated is analyzed as well as the influence of the covering index, defined as the ratio of the designed area of a plate and the area of the treated surface belonging to another plate. As compared with the conventional method of applying sound-absorbing plates, the analyzed structures have a higher technological and economical efficiency. The optimum structure corresponds to an angle of inclination of 15 deg and a covering index of 0.8.

Extended target recognition in cognitive radar networks.

PubMed

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

2010-01-01

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.

Utilizing Weather RADAR for Rapid Location of Meteorite Falls and Space Debris Re-Entry

NASA Technical Reports Server (NTRS)

Fries, Marc D.

2016-01-01

This activity utilizes existing NOAA weather RADAR imagery to locate meteorite falls and space debris falls. The near-real-time availability and spatial accuracy of these data allow rapid recovery of material from both meteorite falls and space debris re-entry events. To date, at least 22 meteorite fall recoveries have benefitted from RADAR detection and fall modeling, and multiple debris re-entry events over the United States have been observed in unprecedented detail.

Penn State Radar Systems: Implementation and Observations

NASA Astrophysics Data System (ADS)

Urbina, J. V.; Seal, R.; Sorbello, R.; Kuyeng, K.; Dyrud, L. P.

2014-12-01

Software Defined Radio/Radar (SDR) platforms have become increasingly popular as researchers, hobbyists, and military seek more efficient and cost-effective means for radar construction and operation. SDR platforms, by definition, utilize a software-based interface for configuration in contrast to traditional, hard-wired platforms. In an effort to provide new and improved radar sensing capabilities, Penn State has been developing advanced instruments and technologies for future radars, with primary objectives of making such instruments more capable, portable, and more cost effective. This paper will describe the design and implementation of two low-cost radar systems and their deployment in ionospheric research at both low and mid-latitudes. One radar has been installed near Penn State campus, University Park, Pennsylvania (77.97°W, 40.70°N), to make continuous meteor observations and mid-latitude plasma irregularities. The second radar is being installed in Huancayo (12.05°S, -75.33°E), Peru, which is capable of detecting E and F region plasma irregularities as well as meteor reflections. In this paper, we examine and compare the diurnal and seasonal variability of specular, non- specular, and head-echoes collected with these two new radar systems and discuss sampling biases of each meteor observation technique. We report our current efforts to validate and calibrate these radar systems with other VHF radars such as Jicamarca and SOUSY. We also present the general characteristics of continuous measurements of E-region and F-region coherent echoes using these modern radar systems and compare them with coherent radar events observed at other geographic mid-latitude radar stations.

Venus wind-altitude radar

NASA Technical Reports Server (NTRS)

Levanon, N.

1974-01-01

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

Evaluation of Various Radar Data Quality Control Algorithms Based on Accumulated Radar Rainfall Statistics

NASA Technical Reports Server (NTRS)

Robinson, Michael; Steiner, Matthias; Wolff, David B.; Ferrier, Brad S.; Kessinger, Cathy; Einaudi, Franco (Technical Monitor)

2000-01-01

The primary function of the TRMM Ground Validation (GV) Program is to create GV rainfall products that provide basic validation of satellite-derived precipitation measurements for select primary sites. A fundamental and extremely important step in creating high-quality GV products is radar data quality control. Quality control (QC) processing of TRMM GV radar data is based on some automated procedures, but the current QC algorithm is not fully operational and requires significant human interaction to assure satisfactory results. Moreover, the TRMM GV QC algorithm, even with continuous manual tuning, still can not completely remove all types of spurious echoes. In an attempt to improve the current operational radar data QC procedures of the TRMM GV effort, an intercomparison of several QC algorithms has been conducted. This presentation will demonstrate how various radar data QC algorithms affect accumulated radar rainfall products. In all, six different QC algorithms will be applied to two months of WSR-88D radar data from Melbourne, Florida. Daily, five-day, and monthly accumulated radar rainfall maps will be produced for each quality-controlled data set. The QC algorithms will be evaluated and compared based on their ability to remove spurious echoes without removing significant precipitation. Strengths and weaknesses of each algorithm will be assessed based on, their abilit to mitigate both erroneous additions and reductions in rainfall accumulation from spurious echo contamination and true precipitation removal, respectively. Contamination from individual spurious echo categories will be quantified to further diagnose the abilities of each radar QC algorithm. Finally, a cost-benefit analysis will be conducted to determine if a more automated QC algorithm is a viable alternative to the current, labor-intensive QC algorithm employed by TRMM GV.

Surface and Basal Roughness in Radar Sounding Data: Obstacle and Opportunity

NASA Astrophysics Data System (ADS)

Schroeder, D. M.; Grima, C.; Haynes, M.

2015-12-01

The surface and basal roughness of glaciers, ice sheets, and ice shelves can pose a significant obstacle to the visual interpretation and quantitative analysis of radar sounding data. Areas of high surface roughness - including grounding zones, shear margins, and crevasse fields - can produce clutter and side-lobe signals that obscure the interpretation of englacial and subglacial features. These areas can also introduce significant variation in bed echo strength profiles as a result of losses from two-way propagation through rough ice surfaces. Similarly, reflections from rough basal interfaces beneath ice sheets and ice shelves can also result in large, spatially variable losses in bed echo power. If unmitigated and uncorrected, these effects can degrade or prevent the definitive interpretation of material and geometric properties at the base of ice sheets and ice shelves using radar reflectivity and bed echo character. However, these effects also provide geophysical signatures of surface and basal interface character - including surface roughness, firn density, subglacial bedform geometry, ice shelf basal roughness, marine-ice/brine detection, and crevasse geometry - that can be observed and constrained by exploiting roughness effects in radar sounding data. We present a series of applications and approaches for characterizing and correcting surface and basal roughness effects for airborne radar sounding data collected in Antarctica. We also present challenges, insights, and opportunities for extending these techniques to the orbital radar sounding of Europa's ice shell.

Preliminary analyses of SIB-B radar data for recent Hawaii lava flows

NASA Technical Reports Server (NTRS)

Kaupp, V. H.; Derryberry, B. A.; Macdonald, H. C.; Gaddis, L. R.; Mouginis-Mark, P. J.

1986-01-01

The Shuttle Imaging Radar (SIR-B) experiment acquired two L-band (23 cm wavelength) radar images (at about 28 and 48 deg incidence angles) over the Kilauea Volcano area of southeastern Hawaii. Geologic analysis of these data indicates that, although aa lava flows and pyroclastic deposits can be discriminated, pahoehoe lava flows are not readily distinguished from surrounding low return materials. Preliminary analysis of data extracted from isolated flows indicates that flow type (i.e., aa or pahoehoe) and relative age can be determined from their basic statistics and illumination angle.

SMAP RADAR Calibration and Validation

NASA Astrophysics Data System (ADS)

West, R. D.; Jaruwatanadilok, S.; Chaubel, M. J.; Spencer, M.; Chan, S. F.; Chen, C. W.; Fore, A.

2015-12-01

The Soil Moisture Active Passive (SMAP) mission launched on Jan 31, 2015. The mission employs L-band radar and radiometer measurements to estimate soil moisture with 4% volumetric accuracy at a resolution of 10 km, and freeze-thaw state at a resolution of 1-3 km. Immediately following launch, there was a three month instrument checkout period, followed by six months of level 1 (L1) calibration and validation. In this presentation, we will discuss the calibration and validation activities and results for the L1 radar data. Early SMAP radar data were used to check commanded timing parameters, and to work out issues in the low- and high-resolution radar processors. From April 3-13 the radar collected receive only mode data to conduct a survey of RFI sources. Analysis of the RFI environment led to a preferred operating frequency. The RFI survey data were also used to validate noise subtraction and scaling operations in the radar processors. Normal radar operations resumed on April 13. All radar data were examined closely for image quality and calibration issues which led to improvements in the radar data products for the beta release at the end of July. Radar data were used to determine and correct for small biases in the reported spacecraft attitude. Geo-location was validated against coastline positions and the known positions of corner reflectors. Residual errors at the time of the beta release are about 350 m. Intra-swath biases in the high-resolution backscatter images are reduced to less than 0.3 dB for all polarizations. Radiometric cross-calibration with Aquarius was performed using areas of the Amazon rain forest. Cross-calibration was also examined using ocean data from the low-resolution processor and comparing with the Aquarius wind model function. Using all a-priori calibration constants provided good results with co-polarized measurements matching to better than 1 dB, and cross-polarized measurements matching to about 1 dB in the beta release. During the

Borehole radar interferometry revisited

USGS Publications Warehouse

Liu, Lanbo; Ma, Chunguang; Lane, John W.; Joesten, Peter K.

2014-01-01

Single-hole, multi-offset borehole-radar reflection (SHMOR) is an effective technique for fracture detection. However, commercial radar system limitations hinder the acquisition of multi-offset reflection data in a single borehole. Transforming cross-hole transmission mode radar data to virtual single-hole, multi-offset reflection data using a wave interferometric virtual source (WIVS) approach has been proposed but not fully demonstrated. In this study, we compare WIVS-derived virtual single-hole, multi-offset reflection data to real SHMOR radar reflection profiles using cross-hole and single-hole radar data acquired in two boreholes located at the University of Connecticut (Storrs, CT USA). The field data results are similar to full-waveform numerical simulations developed for a two-borehole model. The reflection from the adjacent borehole is clearly imaged by both the real and WIVS-derived virtual reflection profiles. Reflector travel-time changes induced by deviation of the two boreholes from the vertical can also be observed on the real and virtual reflection profiles. The results of this study demonstrate the potential of the WIVS approach to improve bedrock fracture imaging for hydrogeological and petroleum reservoir development applications.

Eliminating the non-Gaussian spectral response of X-ray absorbers for transition-edge sensors

NASA Astrophysics Data System (ADS)

Yan, Daikang; Divan, Ralu; Gades, Lisa M.; Kenesei, Peter; Madden, Timothy J.; Miceli, Antonino; Park, Jun-Sang; Patel, Umeshkumar M.; Quaranta, Orlando; Sharma, Hemant; Bennett, Douglas A.; Doriese, William B.; Fowler, Joseph W.; Gard, Johnathon D.; Hays-Wehle, James P.; Morgan, Kelsey M.; Schmidt, Daniel R.; Swetz, Daniel S.; Ullom, Joel N.

2017-11-01

Transition-edge sensors (TESs) as microcalorimeters for high-energy-resolution X-ray spectroscopy are often fabricated with an absorber made of materials with high Z (for X-ray stopping power) and low heat capacity (for high resolving power). Bismuth represents one of the most compelling options. TESs with evaporated bismuth absorbers have shown spectra with undesirable and unexplained low-energy tails. We have developed TESs with electroplated bismuth absorbers over a gold layer that are not afflicted by this problem and that retain the other positive aspects of this material. To better understand these phenomena, we have studied a series of TESs with gold, gold/evaporated bismuth, and gold/electroplated bismuth absorbers, fabricated on the same die with identical thermal coupling. We show that the bismuth morphology is linked to the spectral response of X-ray TES microcalorimeters.

Solid-state radar switchboard

NASA Astrophysics Data System (ADS)

Thiebaud, P.; Cross, D. C.

1980-07-01

A new solid-state radar switchboard equipped with 16 input ports which will output data to 16 displays is presented. Each of the ports will handle a single two-dimensional radar input, or three ports will accommodate a three-dimensional radar input. A video switch card of the switchboard is used to switch all signals, with the exception of the IFF-mode-control lines. Each card accepts inputs from up to 16 sources and can pass a signal with bandwidth greater than 20 MHz to the display assigned to that card. The synchro amplifier of current systems has been eliminated and in the new design each PPI receives radar data via a single coaxial cable. This significant reduction in cabling is achieved by adding a serial-to-parallel interface and a digital-to-synchro converter located at the PPI.

A satellite-based radar wind sensor

NASA Technical Reports Server (NTRS)

Xin, Weizhuang

1991-01-01

The objective is to investigate the application of Doppler radar systems for global wind measurement. A model of the satellite-based radar wind sounder (RAWS) is discussed, and many critical problems in the designing process, such as the antenna scan pattern, tracking the Doppler shift caused by satellite motion, and backscattering of radar signals from different types of clouds, are discussed along with their computer simulations. In addition, algorithms for measuring mean frequency of radar echoes, such as the Fast Fourier Transform (FFT) estimator, the covariance estimator, and the estimators based on autoregressive models, are discussed. Monte Carlo computer simulations were used to compare the performance of these algorithms. Anti-alias methods are discussed for the FFT and the autoregressive methods. Several algorithms for reducing radar ambiguity were studied, such as random phase coding methods and staggered pulse repitition frequncy (PRF) methods. Computer simulations showed that these methods are not applicable to the RAWS because of the broad spectral widths of the radar echoes from clouds. A waveform modulation method using the concept of spread spectrum and correlation detection was developed to solve the radar ambiguity. Radar ambiguity functions were used to analyze the effective signal-to-noise ratios for the waveform modulation method. The results showed that, with suitable bandwidth product and modulation of the waveform, this method can achieve the desired maximum range and maximum frequency of the radar system.

Rapid decrease of radar cross section of meteor head echo observed by the MU radar

NASA Astrophysics Data System (ADS)

Nakamura, T.; Nishio, M.; Sato, T.; Tsutsumi, S.; Tsuda, T.; Fushimi, K.

The meteor head echo observation using the MU (Middle and Upper atmosphere) radar (46.5M Hz, 1MW), Shigaraki, Japan, was carried out simultaneously with a high sensitive ICCD (Image-intensified CCD) camera observation in November 2001. The time records were synchronized using GPS satellite signals, in order to compare instantaneous radar and optical meteor magnitudes. 26 faint meteors were successfully observed simultaneously by both equipments. Detailed comparison of the time variation of radar echo intensity and absolute optical magnitude showed that the radar scattering cross section is likely to decrease rapidly by 5 - 20 dB without no corresponding magnitude variation in the optical data. From a simple modeling, we concluded that such decrease of RCS (radar cross section ) is probably due to the transition from overdense head echo to underd ense head echo.

Radar investigation of asteroids

NASA Technical Reports Server (NTRS)

Ostro, S. J.

1981-01-01

Software to support all stages of asteroid radar observation and data analysis is developed. First-order analysis of all data in hand is complete. Estimates of radar cross sections, circular polarization ratios, and limb-to-limb echo spectral bandwidths for asteroids 7 Iris, 16 Psyche, 97 Klotho, 1862 Apollo, and 1915 Quetzalcoatl are reported. Radar observations of two previously unobserved asteroids were conducted. An Aten asteroid, 2100 Ra-Shalom, with the smallest known semimajor axis (0.83) was detected. Preliminary data reduction indicates a circular polarization ratio comparable to those of Apollo, Quetzalcoatl, and Toro.

Broadband planar multilayered absorbers tuned by VO2 phase transition

NASA Astrophysics Data System (ADS)

Peng, Hao; Ji, Chunhui; Lu, Lulu; Li, Zhe; Li, Haoyang; Wang, Jun; Wu, Zhiming; Jiang, Yadong; Xu, Jimmy; Liu, Zhijun

2017-08-01

The metal-insulator transition makes vanadium dioxide an attractive material for developing reconfigurable optoelectronic components. Here we report on dynamically tunable broadband absorbers consisting of planar multilayered thin films. By thermally triggering the phase transition of vanadium dioxide, the effective impedance of multilayered structures is tuned in or out of the condition of impedance matching to free-space, leading to switchable broadband absorptions. Two types of absorbers are designed and demonstrated by using either the insulating or metallic state of vanadium dioxide at the impedance matched condition. The planar multilayered absorbers exhibit tunable absorption bands over the wavelength ranges of 5-9.3 μm and 3.9-8.2 μm, respectively. A large modulation depth up to 88% is measured. The demonstrated broadband absorbance tunability is of potential interest for reconfigurable bolometric sensing, camouflaging, and modulation of mid-infrared lights.

Design of a nonlinear torsional vibration absorber

NASA Astrophysics Data System (ADS)

Tahir, Ammaar Bin

larger than that in the latter. A nonlinear absorber design has been proposed comprising of thin beams as elastic elements. The geometric configuration of the proposed design has been shown to provide cubic stiffness nonlinearity in torsion. The values of design variables, namely the strength of nonlinearity alpha and torsional stiffness kalpha, were obtained by optimizing dimensions and material properties of the beams for a maximum vibration energy dissipation in the nonlinear absorber. A parametric study has also been conducted to analyze the effect of the magnitude of excitation provided to the system on the performance of a nonlinear absorber. It has been shown that the nonlinear absorber turns out to be more effective in terms of energy dissipation as compared to a linear absorber with an increase in the excitation level applied to the system.

High Throughput Light Absorber Discovery, Part 2: Establishing Structure-Band Gap Energy Relationships.

PubMed

Suram, Santosh K; Newhouse, Paul F; Zhou, Lan; Van Campen, Douglas G; Mehta, Apurva; Gregoire, John M

2016-11-14

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4 V 1.5 Fe 0.5 O 10.5 as a light absorber with direct band gap near 2.7 eV. The strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platform for identifying new optical materials.

Eyeballing oscillators for pulsed Doppler radar

NASA Astrophysics Data System (ADS)

Goldman, S.

1985-03-01

The visibility of small targets to a Doppler radar system in the presence of large targets is limited by phase noise. Such limitations occur when an airborne radar searches the ground for a mobile vehicle. Under these conditions, the performance of the Doppler radar depends greatly on the specifications of its phased-locked oscillator. Goldman (1984) has discussed the steps required to evaluate the noise resulting from a pulsed Doppler radar system. In the present investigation, these techniques are applied in reverse to determine system specifications for oscillator noise. A 95-GHz pulsed Doppler radar system is used as an example of specifying system phase noise.

Coded continuous wave meteor radar

NASA Astrophysics Data System (ADS)

Chau, J. L.; Vierinen, J.; Pfeffer, N.; Clahsen, M.; Stober, G.

2016-12-01

The concept of a coded continuous wave specular meteor radar (SMR) is described. The radar uses a continuously transmitted pseudorandom phase-modulated waveform, which has several advantages compared to conventional pulsed SMRs. The coding avoids range and Doppler aliasing, which are in some cases problematic with pulsed radars. Continuous transmissions maximize pulse compression gain, allowing operation at lower peak power than a pulsed system. With continuous coding, the temporal and spectral resolution are not dependent on the transmit waveform and they can be fairly flexibly changed after performing a measurement. The low signal-to-noise ratio before pulse compression, combined with independent pseudorandom transmit waveforms, allows multiple geographically separated transmitters to be used in the same frequency band simultaneously without significantly interfering with each other. Because the same frequency band can be used by multiple transmitters, the same interferometric receiver antennas can be used to receive multiple transmitters at the same time. The principles of the signal processing are discussed, in addition to discussion of several practical ways to increase computation speed, and how to optimally detect meteor echoes. Measurements from a campaign performed with a coded continuous wave SMR are shown and compared with two standard pulsed SMR measurements. The type of meteor radar described in this paper would be suited for use in a large-scale multi-static network of meteor radar transmitters and receivers. Such a system would be useful for increasing the number of meteor detections to obtain improved meteor radar data products, such as wind fields. This type of a radar would also be useful for over-the-horizon radar, ionosondes, and observations of field-aligned-irregularities.

Space Radar Image of Weddell Sea

NASA Image and Video Library

1999-04-15

Two radar images are shown in this composite to compare the size of a standard spaceborne radar image small inset to the image that is created when the radar instrument is used in the ScanSAR mode large image.

Inflatable Space Structures Technology Development for Large Radar Antennas

NASA Technical Reports Server (NTRS)

Freeland, R. E.; Helms, Richard G.; Willis, Paul B.; Mikulas, M. M.; Stuckey, Wayne; Steckel, Gary; Watson, Judith

2004-01-01

There has been recent interest in inflatable space-structures technology for possible applications on U.S. Department of Defense (DOD) missions because of the technology's potential for high mechanical-packaging efficiency, variable stowed geometry, and deployment reliability. In recent years, the DOD sponsored Large Radar Antenna (LRA) Program applied this new technology to a baseline concept: a rigidizable/inflatable (RI) perimeter-truss structure supporting a mesh/net parabolic reflector antenna. The program addressed: (a) truss concept development, (b) regidizable materials concepts assessment, (c) mesh/net concept selection and integration, and (d) developed potential mechanical-system performance estimates. Critical and enabling technologies were validated, most notably the orbital radiation durable regidized materials and the high modulus, inflatable-deployable truss members. These results in conjunction with conclusions from previous mechanical-packaging studies by the U.S. Defense Advanced Research Projects Agency (DARPA) Special Program Office (SPO) were the impetus for the initiation of the DARPA/SPO Innovative Space-based Antenna Technology (ISAT) Program. The sponsor's baseline concept consisted of an inflatable-deployable truss structure for support of a large number of rigid, active radar panels. The program's goal was to determine the risk associated with the application of these new RI structures to the latest in radar technologies. The approach used to define the technology maturity level of critical structural elements was to: (a) develop truss concept baseline configurations (s), (b) assess specific inflatable-rigidizable materials technologies, and (c) estimate potential mechanical performance. The results of the structures portion of the program indicated there was high risk without the essential materials technology flight experiments, but only moderate risk if the appropriate on-orbit demonstrations were performed. This paper covers both

Preparation and microwave absorption properties of honeycomb core structures coated with composite absorber

NASA Astrophysics Data System (ADS)

Luo, Hui; Chen, Fu; Wang, Fang; Wang, Xian; Dai, Weiyong; Hu, Sheng; Gong, Rongzhou

2018-05-01

Honeycomb structure coated with paraffin filled with composite of graphene and flaky carbonyl iron powder (FCIP) as lossy filler have been studied. The composite of graphene/FCIP with different weight ratio were synthesized via mechanical milling, the electromagnetic properties of the samples were measured by transmission/reflection method in the frequency range of 8-12 GHz. The microwave absorbing properties of the microwave absorbing honeycomb structure (MAHS) and microwave absorbing honeycomb sandwich structure (MAHSS) were studied based on the Finite Element Method with periodical boundary conditions. The matching layer on the top of the honeycomb sandwich structure can enhanced the microwave absorption properties. It was shown that a light weight and broadband MAHSS could be implemented with the use of the magnetic material and dielectric material.

Microwave impregnation of porous materials with thermal energy storage materials

DOEpatents

Benson, D.K.; Burrows, R.W.

1993-04-13

A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

Microwave impregnation of porous materials with thermal energy storage materials

DOEpatents

Benson, David K.; Burrows, Richard W.

1993-01-01

A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

Development of an innovative solar absorber

NASA Astrophysics Data System (ADS)

Goodchild, Gavin

Solar thermal systems have great potential to replace or reduce the dependence of conventional fossil fuel based heating technologies required for space and water heating. Specifically solar domestic hot water systems can contribute 50-75% of the annual thermal load. To date residential users have been slow to purchase and install systems, primarily due to the large monetary investment required to purchase and install a system. Recent innovations in materials design and manufacturing techniques, offer opportunities for the development of absorber plate designs that have the potential to reduce cost, increase efficiency and reduce payback periods. Consequently, this design study was conducted in conjunction with industrial partners to develop an improved absorber based on roll bond manufacturing that can be produced at reduced cost with comparable or greater thermal efficiency.

Mapping the Upper Subsurface of MARS Using Radar Polarimetry

NASA Technical Reports Server (NTRS)

Carter, L. M.; Rincon, R.; Berkoski, L.

2012-01-01

Future human exploration of Mars will require detailed knowledge of the surface and upper several meters of the subsurface in potential landing sites. Likewise, many of the Planetary Science Decadal Survey science goals, such as understanding the history of Mars climate change, determining how the surface was altered through processes like volcanism and fluvial activity, and locating regions that may have been hospitable to life in the past, would be significantly advanced through mapping of the upper meters of the surface. Synthetic aperture radar (SAR) is the only remote sensing technique capable of penetrating through meters of material and imaging buried surfaces at high (meters to tens-of-meters) spatial resolution. SAR is capable of mapping the boundaries of buried units and radar polarimetry can provide quantitative information about the roughness of surface and subsurface units, depth of burial of stratigraphic units, and density of materials. Orbital SAR systems can obtain broad coverage at a spatial scale relevant to human and robotic surface operations. A polarimetric SAR system would greatly increase the safety and utility of future landed systems including sample caching.

Evidence for highly reflecting materials on the surface and subsurface of Venus

NASA Technical Reports Server (NTRS)

Jurgens, R. F.; Slade, M. A.; Saunders, R. S.

1988-01-01

Radar images at a 12.5-centimeter wavelength made with the Goldstone radar interferometer in 1980 and 1986, together with lunar radar images and recent Venera 15 and 16 data, indicate that material on the surface and subsurface of Venus has a Fresnel reflectivity in excess of 50 percent. Such high reflectivities have been reported on the surface in mountainous regions. Material of high reflectivity may also underlie lower reflectivity surficial materials of the plains regions, where it has been excavated by impact cratering in some areas.

Absorber for solar power.

PubMed

Powell, W R

1974-10-01

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.

Electromagnetic characterization of advanced nanostructured materials and multilayer design optimization for metrological and low radar observability applications

NASA Astrophysics Data System (ADS)

Micheli, Davide; Pastore, Roberto; Delfini, Andrea; Giusti, Alfonso; Vricella, Antonio; Santoni, Fabio; Marchetti, Mario; Tolochko, Oleg; Vasilyeva, Ekaterina

2017-05-01

In this work the electromagnetic characterization of composite materials reinforced with carbon and metallic nanoparticles is presented. In particular, the electric permittivity and the magnetic permeability as a function of the frequency are used to evaluate the electromagnetic absorption capability of the nanocomposites. The aim is the study of possible applications in advanced coating able to tune the electromagnetic reflectivity of satellite surfaces in specific frequency ranges, in a special way for those surfaces that for some reason could be exposed to the antenna radiation pattern. In fact, the interference caused by the spurious electromagnetic multipath due to good electric conductive satellite surface components could in turn affect the main radiation lobe of TLC and Telemetry antennas, thus modifying its main propagation directions and finally increasing the microwave channel pathloss. The work reports the analysis of different nanostructured materials in the 2-10 GHz frequency range. The employed nanopowders are of carbon nanotubes, cobalt, argent, titanium, nickel, zinc, copper, iron, boron, bismuth, hafnium, in different weight percentages versus the hosting polymeric matrix. The materials are classified as a function of their electromagnetic losses capability by taking into account of both electric and magnetic properties. The possibility to design multi-layered structures optimized to provide specific microwave response is finally analyzed by the aid of swam intelligence algorithm. This novel technique is in general interesting for metrological purpose and remote sensing purposes, and can be effectively used in aerospace field for frequency selective materials design, in order to reduce the aircraft/spacecraft radar observability at certain frequencies.

Shuttle orbiter radar cross-sectional analysis

NASA Technical Reports Server (NTRS)

Cooper, D. W.; James, R.

1979-01-01

Theoretical and model simulation studies on signal to noise levels and shuttle radar cross section are described. Pre-mission system calibrations, system configuration, and postmission system calibration of the tracking radars are described. Conversion of target range, azimuth, and elevation into radar centered east north vertical position coordinates are evaluated. The location of the impinging rf energy with respect to the target vehicles body axis triad is calculated. Cross section correlation between the two radars is presented.

Downhole pulse radar

DOEpatents

Chang, Hsi-Tien

1989-01-01

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

Online clustering algorithms for radar emitter classification.

PubMed

Liu, Jun; Lee, Jim P Y; Senior; Li, Lingjie; Luo, Zhi-Quan; Wong, K Max

2005-08-01

Radar emitter classification is a special application of data clustering for classifying unknown radar emitters from received radar pulse samples. The main challenges of this task are the high dimensionality of radar pulse samples, small sample group size, and closely located radar pulse clusters. In this paper, two new online clustering algorithms are developed for radar emitter classification: One is model-based using the Minimum Description Length (MDL) criterion and the other is based on competitive learning. Computational complexity is analyzed for each algorithm and then compared. Simulation results show the superior performance of the model-based algorithm over competitive learning in terms of better classification accuracy, flexibility, and stability.

Microscopic modeling of nitride intersubband absorbance

NASA Astrophysics Data System (ADS)

Montano, Ines; Allerman, A. A.; Wierer, J. J.; Moseley, M.; Skogen, E. J.; Tauke-Pedretti, A.; Vawter, G. A.

III-nitride intersubband structures have recently attracted much interest because of their potential for a wide variety of applications ranging from electro-optical modulators to terahertz quantum cascade lasers. To overcome present simulation limitations we have developed a microscopic absorbance simulator for nitride intersubband devices. Our simulator calculates the band structure of nitride intersubband systems using a fully coupled 8x8 k.p Hamiltonian and determines the material response of a single period in a density-matrix-formalism by solving the Heisenberg equation including many-body and dephasing contributions. After calculating the polarization due to intersubband transitions in a single period, the resulting absorbance of a superlattice structure including radiative coupling between the different periods is determined using a non-local Green's-function formalism. As a result our simulator allows us to predict intersubband absorbance of superlattice structures with microscopically determined lineshapes and linewidths accounting for both many-body and correlation contributions. This work is funded by Sandia National Laboratories Laboratory Directed Research and Development program. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin.

Bistatic and Multistatic Radar: Surveillance, Countermeasures, and Radar Cross Sections. (Latest citations from the Aerospace Database)

NASA Technical Reports Server (NTRS)

1998-01-01

The bibliography contains citations concerning the design, development, testing, and evaluation of bistatic and multistatic radar used in surveillance and countermeasure technology. Citations discuss radar cross sections, target recognition and characteristics, ghost recognition, motion image compensation, and wavelet analysis. Stealth aircraft design, stealth target tracking, synthetic aperture radar, and space applications are examined.

Bistatic and Multistatic Radar: Surveillance, Countermeasures, and Radar Cross Sections. (Latest Citations from the Aerospace Database)

NASA Technical Reports Server (NTRS)

1997-01-01

The bibliography contains citations concerning the design, development, testing, and evaluation of bistatic and multistatic radar used in surveillance and countermeasure technology. Citations discuss radar cross sections, target recognition and characteristics, ghost recognition, motion image compensation, and wavelet analysis. Stealth aircraft design, stealth target tracking, synthetic aperture radar, and space applications are examined.

HF Radar Sea-echo from Shallow Water.

PubMed

Lipa, Belinda; Nyden, Bruce; Barrick, Don; Kohut, Josh

2008-08-06

HF radar systems are widely and routinely used for the measurement of ocean surface currents and waves. Analysis methods presently in use are based on the assumption of infinite water depth, and may therefore be inadequate close to shore where the radar echo is strongest. In this paper, we treat the situation when the radar echo is returned from ocean waves that interact with the ocean floor. Simulations are described which demonstrate the effect of shallow water on radar sea-echo. These are used to investigate limits on the existing theory and to define water depths at which shallow-water effects become significant. The second-order spectral energy increases relative to the first-order as the water depth decreases, resulting in spectral saturation when the waveheight exceeds a limit defined by the radar transmit frequency. This effect is particularly marked for lower radar transmit frequencies. The saturation limit on waveheight is less for shallow water. Shallow water affects second-order spectra (which gives wave information) far more than first-order (which gives information on current velocities), the latter being significantly affected only for the lowest radar transmit frequencies for extremely shallow water. We describe analysis of radar echo from shallow water measured by a Rutgers University HF radar system to give ocean wave spectral estimates. Radar-derived wave height, period and direction are compared with simultaneous shallow-water in-situ measurements.

Mathematical analysis study for radar data processing and enhancement. Part 1: Radar data analysis

NASA Technical Reports Server (NTRS)

James, R.; Brownlow, J. D.

1985-01-01

A study is performed under NASA contract to evaluate data from an AN/FPS-16 radar installed for support of flight programs at Dryden Flight Research Facility of NASA Ames Research Center. The purpose of this study is to provide information necessary for improving post-flight data reduction and knowledge of accuracy of derived radar quantities. Tracking data from six flights are analyzed. Noise and bias errors in raw tracking data are determined for each of the flights. A discussion of an altiude bias error during all of the tracking missions is included. This bias error is defined by utilizing pressure altitude measurements made during survey flights. Four separate filtering methods, representative of the most widely used optimal estimation techniques for enhancement of radar tracking data, are analyzed for suitability in processing both real-time and post-mission data. Additional information regarding the radar and its measurements, including typical noise and bias errors in the range and angle measurements, is also presented. This is in two parts. This is part 1, an analysis of radar data.

Tracking radar studies of bird migration

NASA Technical Reports Server (NTRS)

Williams, T. C.; Williams, J. M.; Teal, J. M.; Kanwisher, J. W.

1972-01-01

The application of tracking radar for determining the flight paths of migratory birds is discussed. The effects produced by various meteorological parameters are described. Samples of radar scope presentations obtained during tracking studies are presented. The characteristics of the radars and their limitations are examined.

Earth resources shuttle imaging radar. [systems analysis and design analysis of pulse radar for earth resources information system

NASA Technical Reports Server (NTRS)

1975-01-01

A report is presented on a preliminary design of a Synthetic Array Radar (SAR) intended for experimental use with the space shuttle program. The radar is called Earth Resources Shuttle Imaging Radar (ERSIR). Its primary purpose is to determine the usefulness of SAR in monitoring and managing earth resources. The design of the ERSIR, along with tradeoffs made during its evolution is discussed. The ERSIR consists of a flight sensor for collecting the raw radar data and a ground sensor used both for reducing these radar data to images and for extracting earth resources information from the data. The flight sensor consists of two high powered coherent, pulse radars, one that operates at L and the other at X-band. Radar data, recorded on tape can be either transmitted via a digital data link to a ground terminal or the tape can be delivered to the ground station after the shuttle lands. A description of data processing equipment and display devices is given.

Ultra-thin and -broadband microwave magnetic absorber enhanced by phase gradient metasurface incorporation

NASA Astrophysics Data System (ADS)

Fan, Ya; Wang, Jiafu; Li, Yongfeng; Pang, Yongqiang; Zheng, Lin; Xiang, Jiayu; Zhang, Jieqiu; Qu, Shaobo

2018-05-01

Based on the effect of anomalous reflection and refraction caused by the circularly cross-polarized phase gradient metasurface (PGM), an ultra-thin and -broadband composite absorber composed of metasurface and conventional magnetic absorbing film is proposed and demonstrated in this paper. In the case of keeping nearly the same thickness of absorbing layer, the equivalent thickness of magnetic absorbing film is enlarged by the effect of anomalous reflection and refraction, resulting in the expansion and improvement of the absorbing bandwidth and efficiency in low microwave frequency. A biarc metallic sub-cell for circularly crossed polarization is adopted to form a broadband phase gradient, by the means of rotating the Pancharatnam–Berry phases. As indicated in the experimental results, the fabricated 3.6 mm-thick absorber can averagely absorb microwave energy with the specular reflection below  ‑10 dB in the frequency interval of 2–12 GHz, which shows a good match with simulated results. Due to ultra-thin thickness and ultra-wide operating bandwidth, the proposed application of PGM in absorbing can provide an alternative way to enhance the absorbing property of current absorbing materials.

Derivation of a Levelized Cost of Coating (LCOC) metric for evaluation of solar selective absorber materials

DOE PAGES

Ho, C. K.; Pacheco, J. E.

2015-06-05

A new metric, the Levelized Cost of Coating (LCOC), is derived in this paper to evaluate and compare alternative solar selective absorber coatings against a baseline coating (Pyromark 2500). In contrast to previous metrics that focused only on the optical performance of the coating, the LCOC includes costs, durability, and optical performance for more comprehensive comparisons among candidate materials. The LCOC is defined as the annualized marginal cost of the coating to produce a baseline annual thermal energy production. Costs include the cost of materials and labor for initial application and reapplication of the coating, as well as the costmore » of additional or fewer heliostats to yield the same annual thermal energy production as the baseline coating. Results show that important factors impacting the LCOC include the initial solar absorptance, thermal emittance, reapplication interval, degradation rate, reapplication cost, and downtime during reapplication. The LCOC can also be used to determine the optimal reapplication interval to minimize the levelized cost of energy production. As a result, similar methods can be applied more generally to determine the levelized cost of component for other applications and systems.« less

Radar investigation of asteroids

NASA Astrophysics Data System (ADS)

Ostro, S. J.

1984-07-01

The initial radar observations of the mainbelt asteroids 9 Metis, 27 Euterpe, and 60 Echo are examined. For each target, data are taken simultaneously in the same sense of circular polarization as transmitted as well as in the opposite (OC) sense. Estimates of the radar cross sections provide estimates of the circular polarization ratio, and the normalized OC radar cross section. The circular polarization ratio, is comparable to values measured for other large S type asteroids and for a few much smaller, Earth approaching objects, most of the echo is due to single reflection backscattering from smooth surface elements.

Radar investigation of asteroids

NASA Technical Reports Server (NTRS)

Ostro, S. J.

1984-01-01

The initial radar observations of the mainbelt asteroids 9 Metis, 27 Euterpe, and 60 Echo are examined. For each target, data are taken simultaneously in the same sense of circular polarization as transmitted as well as in the opposite (OC) sense. Estimates of the radar cross sections provide estimates of the circular polarization ratio, and the normalized OC radar cross section. The circular polarization ratio, is comparable to values measured for other large S type asteroids and for a few much smaller, Earth approaching objects, most of the echo is due to single reflection backscattering from smooth surface elements.

A microprogrammable radar controller

NASA Technical Reports Server (NTRS)

Law, D. C.

1986-01-01

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

Eliminating the non-Gaussian spectral response of X-ray absorbers for transition-edge sensors

DOE PAGES

Divan, Ralu; Gades, Lisa M.; Kenesei, Peter; ...

2017-11-08

Transition-edge sensors (TESs) as microcalorimeters for high-energy-resolution X-ray spectroscopy are often fabricated with an absorber made of materials with high Z (for X-ray stopping power) and low heat capacity (for high resolving power). Bismuth represents one of the most compelling options. TESs with evaporated bismuth absorbers have shown spectra with undesirable and unexplained low-energy tails. We have developed TESs with electroplated bismuth absorbers over a gold layer that are not afflicted by this problem and that retain the other positive aspects of this material. To better understand these phenomena, we have studied a series of TESs with gold, gold/evaporated bismuth,more » and gold/electroplated bismuth absorbers, fabricated on the same die with identical thermal coupling. Lastly, we show that the bismuth morphology is linked to the spectral response of X-ray TES microcalorimeters.« less

Eliminating the non-Gaussian spectral response of X-ray absorbers for transition-edge sensors

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

Divan, Ralu; Gades, Lisa M.; Kenesei, Peter

Transition-edge sensors (TESs) as microcalorimeters for high-energy-resolution X-ray spectroscopy are often fabricated with an absorber made of materials with high Z (for X-ray stopping power) and low heat capacity (for high resolving power). Bismuth represents one of the most compelling options. TESs with evaporated bismuth absorbers have shown spectra with undesirable and unexplained low-energy tails. We have developed TESs with electroplated bismuth absorbers over a gold layer that are not afflicted by this problem and that retain the other positive aspects of this material. To better understand these phenomena, we have studied a series of TESs with gold, gold/evaporated bismuth,more » and gold/electroplated bismuth absorbers, fabricated on the same die with identical thermal coupling. Lastly, we show that the bismuth morphology is linked to the spectral response of X-ray TES microcalorimeters.« less

Establishment of new design criteria for GlidCop ® X-ray absorbers

DOE PAGES

Collins, Jeff T.; Nudell, Jeremy; Navrotski, Gary; ...

2017-02-20

Here, an engineering research program has been conducted at the Advanced Photon Source (APS) in order to determine the thermomechanical conditions that lead to crack formation in GlidCop ®, a material commonly used to fabricate X-ray absorbers at X-ray synchrotron facilities. This dispersion-strengthened copper alloy is a proprietary material and detailed technical data of interest to the synchrotron community is limited. The results from the research program have allowed new design criteria to be established for GlidCop ® X-ray absorbers based upon the thermomechanically induced fatigue behavior of the material. X-ray power from APS insertion devices was used to exposemore » 30 GlidCop ® samples to 10000 thermal loading cycles each under various beam power conditions, and all of the samples were metallurgically examined for crack presence/geometry. In addition, an independent testing facility was hired to measure temperature-dependent mechanical data and uniaxial mechanical fatigue data for numerous GlidCop ® samples. Data from these studies support finite element analysis (FEA) simulation and parametric models, allowing the development of a thermal fatigue model and the establishment of new design criteria so that the thermomechanically induced fatigue life of X-ray absorbers may be predicted. It is also demonstrated how the thermal fatigue model can be used as a tool to geometrically optimize X-ray absorber designs.« less

Establishment of new design criteria for GlidCop ® X-ray absorbers

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

Collins, Jeff T.; Nudell, Jeremy; Navrotski, Gary

Here, an engineering research program has been conducted at the Advanced Photon Source (APS) in order to determine the thermomechanical conditions that lead to crack formation in GlidCop ®, a material commonly used to fabricate X-ray absorbers at X-ray synchrotron facilities. This dispersion-strengthened copper alloy is a proprietary material and detailed technical data of interest to the synchrotron community is limited. The results from the research program have allowed new design criteria to be established for GlidCop ® X-ray absorbers based upon the thermomechanically induced fatigue behavior of the material. X-ray power from APS insertion devices was used to exposemore » 30 GlidCop ® samples to 10000 thermal loading cycles each under various beam power conditions, and all of the samples were metallurgically examined for crack presence/geometry. In addition, an independent testing facility was hired to measure temperature-dependent mechanical data and uniaxial mechanical fatigue data for numerous GlidCop ® samples. Data from these studies support finite element analysis (FEA) simulation and parametric models, allowing the development of a thermal fatigue model and the establishment of new design criteria so that the thermomechanically induced fatigue life of X-ray absorbers may be predicted. It is also demonstrated how the thermal fatigue model can be used as a tool to geometrically optimize X-ray absorber designs.« less

The First Year of Cassini RADAR Observations of Titan

NASA Astrophysics Data System (ADS)

Elachi, C.; Lorenz, R. D.

2005-12-01

Titan`s atmosphere is essentially transparent to Radar, making it an ideal technique to study Titan`s surface. Cassini`s Titan Radar Mapper operates as a passive radiometer, scatterometer, altimeter, and synthetic aperture radar (SAR). Here we review data from four fly-bys in the first year of Cassini`s tour (Ta: October 2004, T3: February 2005, T7: September 2005, and T8: October 2005.) Early SAR images from Ta and T3 (showing < 3% of Titan`s surface) reveal that Titan is geologically young and complex (see Elachi et al., 2005, Science 13, 970-4). Significant variations were seen between the range of features seen in the Ta swath (centered at ~50N, 80W) and T3 (~ 30N, 70W) : the large-scale radiometric properties also differed, with T3 being radar-brighter. A variety of features have been identified in SAR, including two large impact craters, cryovolcanic flows and a probable volcanic dome. Dendritic and braided radar-bright sinuous channels, some 180km long, are evidence of fluvial activity. `Cat scratches`, arrays of linear dark features seem most likely to be Aeolian. Radar provides unique topographic information on Titan`s landscape e.g. the depth of the 80km crater observed in T3 can be geometrically determined to be around 1300m deep. Despite the shallow large-scale slopes indicated in altimetry to date, many small hills are seen in T3. Scatterometry and radiometry maps provide large-scale classification of surface types and polarization and incidence angle coverage being assembled will constrain dielectric and scattering properties of the surface. Judging from the TA/T3 diversity, we expect further variations in the types and distribution of surface materials and geologic features in T7, which spans a wide range of Southern latitudes. T8 SAR will cover a near-equatorial dark region, including the landing site of the Huygens probe.

Investigations on the sensitivity of a stepped-frequency radar utilizing a vector network analyzer for Ground Penetrating Radar

NASA Astrophysics Data System (ADS)

Seyfried, Daniel; Schubert, Karsten; Schoebel, Joerg

2014-12-01

Employing a continuous-wave radar system, with the stepped-frequency radar being one type of this class, all reflections from the environment are present continuously and simultaneously at the receiver. Utilizing such a radar system for Ground Penetrating Radar purposes, antenna cross-talk and ground bounce reflection form an overall dominant signal contribution while reflections from objects buried in the ground are of quite weak amplitude due to attenuation in the ground. This requires a large dynamic range of the receiver which in turn requires high sensitivity of the radar system. In this paper we analyze the sensitivity of our vector network analyzer utilized as stepped-frequency radar system for GPR pipe detection. We furthermore investigate the performance of increasing the sensitivity of the radar by means of appropriate averaging and low-noise pre-amplification of the received signal. It turns out that the improvement in sensitivity actually achievable may differ significantly from theoretical expectations. In addition, we give a descriptive explanation why our appropriate experiments demonstrate that the sensitivity of the receiver is independent of the distance between the target object and the source of dominant signal contribution. Finally, our investigations presented in this paper lead to a preferred setting of operation for our vector network analyzer in order to achieve best detection capability for weak reflection amplitudes, hence making the radar system applicable for Ground Penetrating Radar purposes.

Multimission airborne radar for the 1990s

NASA Astrophysics Data System (ADS)

Robinson, Thomas H.

1986-07-01

The continuing trend towards the development and production of aircraft capable of multiple missions indicates that future airborne radars must provide a broad spectrum of air-to-air and air-to-ground modes. This paper investigates the modal and functional requirements of a multimode radar projected for the mid-1990s period. The paper is divided into two sections. In the first, the multimission capabilities of current radars are presented to establish trends and capabilities. In the second, the requirements of the next generation system are established. Current multimode radars lay the basis for future systems. The experience gained on the APG-65 and APG-63/70 radars is presented and conclusions are drawn regarding their impact on future system requirements. Not only are modes and performance reviewed for these radars but also their system architecture. The discussion starts with the APG-65 radar which is the first true multimission radar with programmable signal and data processing. Following this, the evolution of the APG-63 radar, culminating with the most recent upgrading resulting in redesignation of APG-70, is presented. The incorporation of air-to-ground capabilities in the APG-70, resulting from the Dual Role Fighter program, is reviewed. Results from the Advanced Fighter Capabilities Demonstration program are presented showing how high resolution SAR was incorporated into a full weapon delivery solution. The specific radar requirements for the next decade radar system are developed. This development is done in two parts. First, mode requirements are synthesized for air superiority, navigation and strike/interdiction operation. This includes low altitude penetration requirements and a review of radar timeline constraints which arise. Second, the fundamental functional requirements needed to implement the mode requirements are explored. Architectural issues and their impact on reliability and sustainability are also considered.

Radar/radiometer facilities for precipitation measurements

NASA Technical Reports Server (NTRS)

Hodge, D. B.; Taylor, R. C.

1973-01-01

The OSU ElectroScience Laboratory Radar/Radiometer Facilities are described. This instrumentation includes a high-resolution radar/radiometer system, a fully automated low-resolution radar system, and a small surveillance radar system. The high-resolution radar/radiometer system operates at 3, 9, and 15 GHz using two 9.1 m and one 4.6 m parabolic antennas, respectively. The low-resolution and surveillance radars operate at 9 and 15 GHz, respectively. Both the high- and low-resolution systems are interfaced to real-time digital processing and recording systems. This capability was developed for the measurement of the temporal and spatial characteristics of precipitation in conjunction with millimeter wavelength propagation studies utilizing the Advanced Technology Satellites. Precipitation characteristics derived from these measurements could also be of direct benefit in such diverse areas as: the atmospheric sciences, meteorology, water resources, flood control and warning, severe storm warning, agricultural crop studies, and urban and regional planning.

Radar Reflectivity in Wingtip-Generated Wake Vortices

NASA Technical Reports Server (NTRS)

Marshall, Robert E.; Mudukutore, Ashok; Wissel, Vicki

1997-01-01

This report documents new predictive models of radar reflectivity, with meter-scale resolution, for aircraft wakes in clear air and fog. The models result from a radar design program to locate and quantify wake vortices from commercial aircraft in support of the NASA Aircraft Vortex Spacing System (AVOSS). The radar reflectivity model for clear air assumes: 1) turbulent eddies in the wake produce small discontinuities in radar refractive index; and 2) these turbulent eddies are in the 'inertial subrange' of turbulence. From these assumptions, the maximum radar frequency for detecting a particular aircraft wake, as well as the refractive index structure constant and radar volume reflectivity in the wake can be obtained from the NASA Terminal Area Simulation System (TASS) output. For fog conditions, an empirical relationship is used to calculate radar reflectivity factor from TASS output of bulk liquid water. Currently, two models exist: 1) Atlas-based on observations of liquid water and radar reflectivity factor in clouds; and 2) de Wolf- specifically tailored to a specific measured dataset (1992 Vandenberg Air Force Base).

Elastic, Frictional, Strength and Dynamic Characteristics of the Bell Shape Shock Absorbers Made of MR Wire Material

NASA Astrophysics Data System (ADS)

Lazutkin, G. V.; Davydov, D. P.; Boyarov, K. V.; Volkova, T. V.

2018-01-01

The results of the mechanical characteristic experimental studies are presented for the shock absorbers of DKU type with the elastic elements of the bell shape made of MR material and obtained by the cold pressing of mutually crossing wire spirals with their inclusion in the array of reinforcing wire harnesses. The design analysis and the technology of MR production based on the methods of similarity theory and dimensional analysis revealed the dimensionless determined and determining parameters of elastic frictional, dynamic and strength characteristics under the static and dynamic loading of vibration isolators. The main similarity criteria of mechanical characteristics for vibration isolators and their graphical and analytical representation are determined, taking into account the coefficients of these (affine) transformations of the hysteresis loop family field.

Long-wavelength Radar Studies of the Lunar Maria

NASA Technical Reports Server (NTRS)

Campbell, Bruce A.; Hawke, B. Ray; Thompson, Thomas W.

1995-01-01

among various mineral phases, but ilmenite content (FeTiO3) has typically been cited as the dominant cause of changes in loss tangent (and thus the radar absorption). The lack of correlation between the radar data and TiO2 estimates may arise from uncertainties in the Charette technique, subtle differences in the upper surface and bulk properties of the regolith, mineralogic effects on the radar not linked to titanium content, or to some combination of these factors. Dark crater haloes in the mare and highlands, and low radar returns from apparent cryptomare regions, are used to illustrate the role radar data can play in identifying changes in regolith composition; low-return haloes around craters such as Petavius may indicate 5-25% contamination of the highlands soil by excavated mare material or a layer of rock-poor ejecta at least several meters deep. The 7.5-m data were shown to correlate to a reasonable degree with estimates of Fe abundance, suggesting that this component of the mare basalts is primarily responsible for attenuation losses at very long wavelengths. The different sensitivities of the two radar wavelengths and multispectral data offers the potential for future deep mapping of the mare lava flows and regolith.

Long-wavelength Radar Studies of the Lunar Maria

NASA Technical Reports Server (NTRS)

Campbell, Bruce A.; Hawke, B. Ray; Thompson, Thomas W.

1995-01-01

various mineral phases, but ilmenite content (FeTiO3) has typically been cited as the dominant cause of changes in loss tangent (and thus the radar absorption). The lack of correlation between the radar data and TiO2 estimates may arise from uncertainties in the Charette technique, subtle differences in the upper surface and bulk properties of the regolith, mineralogic effects on the radar not linked to titanium content, or to some combination of these factors. Dark crater haloes in the mare and highlands, and low radar returns from apparent cryptomare regions, are used to illustrate the role radar data can play in identifying changes in regolith composition; low-return haloes around craters such as Petavius may indicate 5-25% contamination of the highlands soil by excavated mare material or a layer of rock-poor ejecta at least several meters deep. The 7.5-m data were shown to correlate to a reasonable degree with estimates of Fe abundance, suggesting that this component of the mare basalts is primarily responsible for attenuation losses at very long wavelengths. The different sensitivities of the two radar wavelengths and multispectral data offers the potential for future deep mapping of the mare lava flows and regolith.

Applications of Surface Penetrating Radar for Mars Exploration

NASA Astrophysics Data System (ADS)

Li, H.; Li, C.; Ran, S.; Feng, J.; Zuo, W.

2015-12-01

Surface Penetrating Radar (SPR) is a geophysical method that uses electromagnetic field probe the interior structure and lithological variations of a lossy dielectric materials, it performs quite well in dry, icy and shallow-soil environments. The first radar sounding of the subsurface of planet was carried out by Apollo Lunar Sounder Experiment (ALSE) of the Apollo 17 in 1972. ALSE provided very precise information about the moon's topography and revealed structures beneath the surface in both Mare Crisium and Mare Serenitatis. Russian Mars'92 was the first Mars exploration mission that tried to use SPR to explore martian surface, subsurface and ionosphere. Although Mars'96 launch failed in 1996, Russia(Mars'98, cancelled in 1998; Phobos-Grunt, launch failed in 2011), ESA(Mars Express, succeeded in 2003; Netlander, cancelled in 2003; ExoMars 2018) and NASA(MRO, succeeded in 2005; MARS 2020) have been making great effects to send SPR to Mars, trying to search for the existence of groundwater and life in the past 20 years. So far, no Ground Penetrating Radar(GPR) has yet provided in situ observations on the surface of Mars. In December 2013, China's CE-3 lunar rover (Yuto) equipped with a GPR made the first direct measurement of the structure and depth of the lunar soil, and investigation of the lunar crust structure along the rover path. China's Mars Exploration Program also plans to carry the orbiting radar sounder and rover GPR to characterize the nature of subsurface water or ices and the layered structure of shallow subsurface of Mars. SPR can provide diversity of applications for Mars exploration , that are: to map the distribution of solid and liquid water in the upper portions of the Mars' crust; to characterize the subsurface geologic environment; to investigate the planet's subsurface to better understand the evolution and habitability of Mars; to perform the martain ionosphere sounding. Based on SPR's history and achievements, combined with the

Noncooperative rendezvous radar system

NASA Technical Reports Server (NTRS)

1974-01-01

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

Externally tuned vibration absorber

DOEpatents

Vincent, Ronald J.

1987-09-22

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

Downhole pulse radar

DOEpatents

Chang, Hsi-Tien

1987-09-28

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

High throughput light absorber discovery, Part 2: Establishing structure–band gap energy relationships

DOE PAGES

Suram, Santosh K.; Newhouse, Paul F.; Zhou, Lan; ...

2016-09-23

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4V 1.5Fe 0.5O 10.5 as a light absorber with direct band gap near 2.7 eV. Here, the strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platformmore » for identifying new optical materials.« less

High throughput light absorber discovery, Part 2: Establishing structure–band gap energy relationships

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

Suram, Santosh K.; Newhouse, Paul F.; Zhou, Lan

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4V 1.5Fe 0.5O 10.5 as a light absorber with direct band gap near 2.7 eV. Here, the strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platformmore » for identifying new optical materials.« less

Radar investigation of asteroids

NASA Technical Reports Server (NTRS)

Ostro, S. J.

1983-01-01

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.

Radar, Insect Population Ecology, and Pest Management

NASA Technical Reports Server (NTRS)

Vaughn, C. R. (Editor); Wolf, W. (Editor); Klassen, W. (Editor)

1979-01-01

Discussions included: (1) the potential role of radar in insect ecology studies and pest management; (2) the potential role of radar in correlating atmospheric phenomena with insect movement; (3) the present and future radar systems; (4) program objectives required to adapt radar to insect ecology studies and pest management; and (5) the specific action items to achieve the objectives.

A Broadband Micro-Machined Far-Infrared Absorber

NASA Technical Reports Server (NTRS)

Wollack, E. J.; Datesman, A. M.; Jhabvala, C. A.; Miller, K. H.; Quijada, M. A.

2016-01-01

The experimental investigation of a broadband far-infrared meta-material absorber is described. The observed absorptance is greater than 0.95 from 1 to 20 terahertz (300-15 microns) over a temperature range spanning 5-300 degrees Kelvin. The meta-material, realized from an array of tapers approximately 100 microns in length, is largely insensitive to the detailed geometry of these elements and is cryogenically compatible with silicon-based micro-machined technologies. The electromagnetic response is in general agreement with a physically motivated transmission line model.

High-Resolution Radar Imagery of Mars

NASA Astrophysics Data System (ADS)

Harmon, John K.; Nolan, M. C.

2009-09-01

We present high-resolution radar images of Mars obtained during the 2005 and 2007 oppositions. The images were constructed from long-code delay-Doppler observations made with the Arecibo S-band (13-cm) radar. The average image resolution of 3 km represented a better than order-of-magnitude improvement over pre-upgrade Arecibo imagery of the planet. Images of depolarized reflectivity (an indicator primarily of wavelength-scale surface roughness) show the same bright volcanic flow features seen in earlier imagery, but with much finer detail. A new image of the Elysium region shows fine detail in the radar-bright channels of Athabasca Vallis, Marte Vallis, and Grjota Vallis. The new images of Tharsis and Olympus Mons also show a complex array of radar-bright and radar-dark features. Southern Amazonis exhibits some of the most complex and puzzling radar-bright structure on the planet. Another curiosity is the Chryse/Xanthe/Channels region, where we find some radar-bright features in or adjacent to fluvial chaos structures. Chryse/Xanthe is also the only region of Mars showing radar-bright craters (which are rare on Mars but common on the Moon and Mercury). We also obtained the first delay-Doppler image showing the enhanced backscatter from the residual south polar ice cap. In addition to the depolarized imagery, we were able to make the first delay-Doppler images of the circular polarization ratio (an important diagnostic for surface roughness texture). We find that vast areas of the radar-bright volcanic regions have polarization ratios close to unity. Such high ratios are rare for terrestrial lava flows and only seen for extremely blocky surfaces giving high levels of multiple scattering.

Radar research at the University of Kansas

NASA Astrophysics Data System (ADS)

Blunt, Shannon D.; Allen, Christopher; Arnold, Emily; Hale, Richard; Hui, Rongqing; Keshmiri, Shahriar; Leuschen, Carlton; Li, Jilu; Paden, John; Rodriguez-Morales, Fernando; Salandrino, Alessandro; Stiles, James

2017-05-01

Radar research has been synonymous with the University of Kansas (KU) for over half a century. As part of this special session organized to highlight significant radar programs in academia, this paper surveys recent and ongoing work at KU. This work encompasses a wide breadth of sensing applications including the remote sensing of ice sheets, autonomous navigation methods for unmanned aerial vehicles (UAVs), novel laser radar capabilities, detection of highenergy cosmic rays using bistatic radar, different forms of waveform diversity such as MIMO radar and pulse agility, and various radar-embedded communication methods. The results of these efforts impact our understanding of the changing nature of the environment, address the proliferation of unmanned systems in the US airspace, realize new sensing modalities enabled by the joint consideration of electromagnetics and signal processing, and greater facilitate radar operation in an increasingly congested and contested spectrum.

HF Radar Sea-echo from Shallow Water

PubMed Central

Lipa, Belinda; Nyden, Bruce; Barrick, Don; Kohut, Josh

2008-01-01

HF radar systems are widely and routinely used for the measurement of ocean surface currents and waves. Analysis methods presently in use are based on the assumption of infinite water depth, and may therefore be inadequate close to shore where the radar echo is strongest. In this paper, we treat the situation when the radar echo is returned from ocean waves that interact with the ocean floor. Simulations are described which demonstrate the effect of shallow water on radar sea-echo. These are used to investigate limits on the existing theory and to define water depths at which shallow-water effects become significant. The second-order spectral energy increases relative to the first-order as the water depth decreases, resulting in spectral saturation when the waveheight exceeds a limit defined by the radar transmit frequency. This effect is particularly marked for lower radar transmit frequencies. The saturation limit on waveheight is less for shallow water. Shallow water affects second-order spectra (which gives wave information) far more than first-order (which gives information on current velocities), the latter being significantly affected only for the lowest radar transmit frequencies for extremely shallow water. We describe analysis of radar echo from shallow water measured by a Rutgers University HF radar system to give ocean wave spectral estimates. Radar-derived wave height, period and direction are compared with simultaneous shallow-water in-situ measurements. PMID:27873776

Measuring the Spectral Properties of Candidate Mineral Sources of the Venus Radar Anomalies

NASA Astrophysics Data System (ADS)

Kohler, E.; Maturilli, A.; Koulen, J.; Helbert, J.

2016-12-01

Radar mapping of the surface of Venus shows areas of high reflectivity (low emissivity) in the Venusian highlands at altitudes between 2.5-4.75 kilometers. The origin of the radar anomalies found in the highlands remains unclear. Previous experimental research investigated possible materials under simulated Venusian atmospheric and surface conditions, with special emphasis on the combined effect of pressure and temperature, and chemical composition. The results of these studies identified candidate source materials for the radar anomalies. In order to fully be considered a true source candidate the material must have spectroscopic measurements comparable to those measured on the surface of Venus where the high temperature affects spectral characteristics of minerals. The spectroscopic measurements of the previously identified candidate minerals were made at the Planetary Spectroscopy Laboratory (PSL) of DLR in Berlin in an effort to identify the anomaly source. The spectroscopic measurements were made with a FTIR Bruker Vertex 80V evacuated to .1 mbar and using several pairings of detector+beamsplitter to cover the spectral range from 0.2 to 20 µm. Each sample was poured in a stainless steel reflectance cup and measured fresh. Successively each cup was heated (via an induction system) in vacuum (0.07 mbar) at 400°C for 8 hours and measured again in the UV+VIS+MIR spectral range. Three consecutive cycles of heating and measuring reflectance were performed to account for spectral variations arising from the thermal processing of the samples. Heating the samples directly inside the reflectance cups allows to measure every time exactly the same surface, exposed to increasing levels of thermal processing. Results from this study are expected to further constrain the source of the Venus radar anomalies.

On the radar cross section (RCS) prediction of vehicles moving on the ground

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

Sabihi, Ahmad

2014-12-10

As readers should be aware, Radar Cross Section depends on the factors such as: Wave frequency and polarization, Target dimension, angle of ray incidence, Target’s material and covering, Type of radar system as monostatic or bistatic, space in which contains target and propagating waves, and etc. Having moved or stationed in vehicles can be effective in RCS values. Here, we investigate effective factors in RCS of moving targets on the ground or sea. Image theory in electromagnetic applies to be taken into account RCS of a target over the ground or sea.

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

Survey of Radar Refraction Error Corrections

DTIC Science & Technology

2016-11-01

ELECTRONIC TRAJECTORY MEASUREMENTS GROUP RCC 266-16 SURVEY OF RADAR REFRACTION ERROR CORRECTIONS DISTRIBUTION A: Approved for...DOCUMENT 266-16 SURVEY OF RADAR REFRACTION ERROR CORRECTIONS November 2016 Prepared by Electronic...This page intentionally left blank. Survey of Radar Refraction Error Corrections, RCC 266-16 iii Table of Contents Preface

Research relative to weather radar measurement techniques

NASA Technical Reports Server (NTRS)

Smith, Paul L.

1992-01-01

Research relative to weather radar measurement techniques, which involves some investigations related to measurement techniques applicable to meteorological radar systems in Thailand, is reported. A major part of the activity was devoted to instruction and discussion with Thai radar engineers, technicians, and meteorologists concerning the basic principles of radar meteorology and applications to specific problems, including measurement of rainfall and detection of wind shear/microburst hazards. Weather radar calibration techniques were also considered during this project. Most of the activity took place during two visits to Thailand, in December 1990 and February 1992.

Parametric study on the performance of automotive MR shock absorbers

NASA Astrophysics Data System (ADS)

Gołdasz, J.; Dzierżek, S.

2016-09-01

The paper contains the results of a parametric study to explore the influence of various quantities on the performance range of semi-active automotive shock absorbers using the magnetorheological (MR) fluid under steady-state and transient excitations. The analysis was performed with simulated data and using a standard single-tube shock absorber configuration with a single-gap MR valve. Additionally, the impact of material variables and valves geometry was examined as the parameters were varied and its dynamic range studied.

Acute dermal toxicity and sensitization studies of novel nano-enhanced UV absorbers.

PubMed

Piasecka-Zelga, Joanna; Zelga, Piotr; Górnicz, Magdalena; Strzelczyk, Paweł; Sójka-Ledakowicz, Jadwiga

2015-01-01

Many employees working outside are exposed to the harmful effects of UV radiation. A growing problem is also sensitization to textile materials and allergic reactions to active compounds. Groups of inorganic UV blockers with nanoparticles may provide superior properties over organic UV absorbers with relatively less potential of provoking dermatitis. To assess acute dermal irritation and sensitization of nano UV absorbers. Five UV absorbers with nano-sized particles (Z11, TiO2 - SiO2 [TDPK], TK44, TK11, A8G) and 2 vehicles (paste-based on 10% PEG, and dispersion with 1% HEC) were tested. Acute dermal irritation was tested using group of 3 rabbits for each absorber. The sensitization study was carried out on groups of 15 guinea pigs for each tested textile with a UV absorber showing an Ultraviolet Protection Factor (UPF)>40. This research was designed according to OECD Test Guideline No. 404 and 406, and 21 rabbits and 60 guinea pigs were used in the study. In acute dermal irritation, Z11 and A8G modifiers and the analyzed paste gave results of 0.047 to 0.33 which classifies them as barely perceptible irritants, whereas the other analyzed modifiers and dispersion gave results of 0.00 and were classified as nonirritating. Only the textile with TK 11 did not have UPF>40. The analyzed barrier materials were classified as nonsenitizers (TDPK, A8G) or mild sensitizers (TK44, Z11). None of the analyzed materials or modifiers induced major skin reactions in animals. Therefore, they present low risk of provoking skin reactions in humans.

Brief review of emerging photovoltaic absorbers

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

Zakutayev, Andriy

Photovoltaic solar cells have recently made significant commercial progress and are on track toward meeting more than 1% of global energy demand. However, further research is needed on photovoltaic technologies that face no scalability constraints in generating more than 10% of the world's electricity. This 2017 article briefly reviews emerging photovoltaic absorber materials, focusing on research progress over the past 2-3 years. Particular emphasis is given to emerging solar cell absorbers -- for example, SnS, Sb 2Se 3, Cu 2SnS 3, and CuSbSe 2 -- related to established solar cell technologies such as CdTe, Cu(In,Ga)Se 2, and CH 3NH 3PbImore » 3. Lastly, the general publication and performance trends are discussed, and the promising future research directions are pointed out.« less

Brief review of emerging photovoltaic absorbers

DOE PAGES

Zakutayev, Andriy

2017-02-08

Photovoltaic solar cells have recently made significant commercial progress and are on track toward meeting more than 1% of global energy demand. However, further research is needed on photovoltaic technologies that face no scalability constraints in generating more than 10% of the world's electricity. This 2017 article briefly reviews emerging photovoltaic absorber materials, focusing on research progress over the past 2-3 years. Particular emphasis is given to emerging solar cell absorbers -- for example, SnS, Sb 2Se 3, Cu 2SnS 3, and CuSbSe 2 -- related to established solar cell technologies such as CdTe, Cu(In,Ga)Se 2, and CH 3NH 3PbImore » 3. Lastly, the general publication and performance trends are discussed, and the promising future research directions are pointed out.« less

Methods for absorbing neutrons

DOEpatents

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

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.

Estimated human absorbed dose of a new (153)Sm bone seeking agent based on biodistribution data in mice: Comparison with (153)Sm-EDTMP.

PubMed

Yousefnia, Hassan; Zolghadri, Samaneh

2015-11-01

The main goal in radiotherapy is to deliver the absorbed dose within the target organs in highest possible amount, while the absorbed dose of the other organs, especially the critical organs, should be kept as low as possible. In this work, the absorbed dose to human organs for a new (153)Sm bone-seeking agent was investigated. (153)Sm-(4-{[(bis(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl) acetic acid ((153)Sm-BPAMD) complex was successfully prepared. The biodistribution of the complex was investigated in male Syrian mice up to 48 h post injection. The human absorbed dose of the complex was estimated based on the biodistribution data of the mice by radiation absorbed dose assessment resource (RADAR) method. The target to non-target absorbed dose ratios for (153)Sm-BPAMD were compared with these ratios for (153)Sm-EDTMP. The highest absorbed dose for (153)Sm-BPAMD was observed in bone surface with 5.828 mGy/MBq. The dose ratios of the bone surface to the red marrow and to the total body for (153)Sm-BPAMD were 5.3 and 20.0, respectively, while these ratios for (153)Sm-EDTMP were 4.4 and 18.3, respectively. This means, for a given dose to the bone surface as the target organ, the red marrow (as the main critical organ) and the total body would receive lesser absorbed dose in the case of (153)Sm-BPAMD. Generally, the human absorbed dose estimation of (153)Sm-BPAMD indicated that all other tissues approximately received insignificant absorbed dose in comparison with bone surface and therefore can be regarded as a new potential agent for bone pain palliation therapy. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Advanced Architectures for Modern Weather/Multifunction Radars

DTIC Science & Technology

2017-03-01

Advanced Architectures for Modern Weather /Multifunction Radars Caleb Fulton The University of Oklahoma Advanced Radar Research Center Norman...and all of them are addressing the need to lower cost while improving beamforming flexibility in future weather radar systems that will be tasked...with multiple non- weather functions. Keywords: Phased arrays, digital beamforming, multifunction radar. Introduction and Overview As the performance

Impedance matched thin metamaterials make metals absorbing.

PubMed

Mattiucci, N; Bloemer, M J; Aközbek, N; D'Aguanno, G

2013-11-13

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others.

Radar cross section lectures

NASA Astrophysics Data System (ADS)

Fuhs, A. E.

A comprehensive account is given of the principles that can be applied in military aircraft configuration studies to minimize the radar cross section (RCS) that will be presented by the resulting design to advanced radars under various mission circumstances. It is noted that, while certain ECM techniques can be nullified by improved enemy electronics in a very short time, RCS reductions may require as much as a decade of radar development before prior levels of detectability can be reestablished by enemy defenses. Attention is given to RCS magnitude determinants, inverse scattering, the polarization and scattering matrix, the RCSs of flat plates and conducting cylinders, and antenna geometry and beam patterns.

Radar studies of bird migration

NASA Technical Reports Server (NTRS)

Williams, T. C.; Williams, J. M.

1974-01-01

Observations of bird migration with NASA radars were made at Wallops Island, Va. Simultaneous observations were made at a number of radar sites in the North Atlantic Ocean in an effort to discover what happened to those birds that were observed leaving the coast of North America headed toward Bermuda, the Caribbean and South America. Transatlantic migration, utilizing observations from a large number of radars is discussed. Detailed studies of bird movements at Wallops Island are presented.

46 CFR 11.480 - Radar observer.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 1 2014-10-01 2014-10-01 false Radar observer. 11.480 Section 11.480 Shipping COAST... ENDORSEMENTS Professional Requirements for National Deck Officer Endorsements § 11.480 Radar observer. (a) This section contains the requirements that an applicant must meet to qualify as a radar observer. (b) If an...

Weather Radar Studies

DTIC Science & Technology

1988-03-31

radar operation and data - collection activities, a large data -analysis effort has been under way in support of automatic wind-shear detection algorithm ...REDUCTION AND ALGORITHM DEVELOPMENT 49 A. General-Purpose Software 49 B. Concurrent Computer Systems 49 C. Sun Workstations 51 D. Radar Data Analysis 52...1. Algorithm Verification 52 2. Other Studies 53 3. Translations 54 4. Outside Distributions 55 E. Mesonet/LLWAS Data Analysis 55 1. 1985 Data 55 2

Hydrologic applications of weather radar

NASA Astrophysics Data System (ADS)

Seo, Dong-Jun; Habib, Emad; Andrieu, Hervé; Morin, Efrat

2015-12-01

By providing high-resolution quantitative precipitation information (QPI), weather radars have revolutionized hydrology in the last two decades. With the aid of GIS technology, radar-based quantitative precipitation estimates (QPE) have enabled routine high-resolution hydrologic modeling in many parts of the world. Given the ever-increasing need for higher-resolution hydrologic and water resources information for a wide range of applications, one may expect that the use of weather radar will only grow. Despite the tremendous progress, a number of significant scientific, technological and engineering challenges remain to realize its potential. New challenges are also emerging as new areas of applications are discovered, explored and pursued. The purpose of this special issue is to provide the readership with some of the latest advances, lessons learned, experiences gained, and science issues and challenges related to hydrologic applications of weather radar. The special issue features 20 contributions on various topics which reflect the increasing diversity as well as the areas of focus in radar hydrology today. The contributions may be grouped as follows:

Kharkiv Meteor Radar System (the XX Age)

NASA Astrophysics Data System (ADS)

Kolomiyets, S. V.

2012-09-01

Kharkiv meteor radar research are of historic value (Kolomiyets and Sidorov 2007). Kharkiv radar observations of meteors proved internationally as the best in the world, it was noted at the IAU General Assembly in 1958. In the 1970s Kharkiv meteor automated radar system (MARS) was recommended at the international level as a successful prototype for wide distribution. Until now, this radar system is one of the most sensitive instruments of meteor radars in the world for astronomical observations. In 2004 Kharkiv meteor radar system is included in the list of objects which compose the national property of Ukraine. Kharkiv meteor radar system has acquired the status of the important historical astronomical instrument in world history. Meteor Centre for researching meteors in Kharkiv is a analogue of the observatory and performs the same functions of a generator and a battery of special knowledge and skills (the world-famous studio). Kharkiv and the location of the instrument were brand points on the globe, as the place where the world-class meteor radar studies were carried out. They are inscribed in the history of meteor astronomy, in large letters and should be immortalized on a world-wide level.