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Sample records for absorbance band centered

  1. Wide band cryogenic ultra-high vacuum microwave absorber

    DOEpatents

    Campisi, I.E.

    1992-05-12

    An absorber waveguide assembly for absorbing higher order modes of microwave energy under cryogenic ultra-high vacuum conditions, that absorbs wide-band multi-mode energy. The absorber is of a special triangular shape, made from flat tiles of silicon carbide and aluminum nitride. The leading sharp end of the absorber is located in a corner of the waveguide and tapers to a larger cross-sectional area whose center is located approximately in the center of the wave guide. The absorber is relatively short, being of less height than the maximum width of the waveguide. 11 figs.

  2. Wide band cryogenic ultra-high vacuum microwave absorber

    DOEpatents

    Campisi, Isidoro E.

    1992-01-01

    An absorber wave guide assembly for absorbing higher order modes of microwave energy under cryogenic ultra-high vacuum conditions, that absorbs wide-band multi-mode energy. The absorber is of a special triangular shape, made from flat tiles of silicon carbide and aluminum nitride. The leading sharp end of the absorber is located in a corner of the wave guide and tapers to a larger cross-sectional area whose center is located approximately in the center of the wave guide. The absorber is relatively short, being of less height than the maximum width of the wave guide.

  3. An ultrathin dual-band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Duan, Junping; Zhang, Wendong; Wang, Wanjun; Zhang, Binzhen

    2016-10-01

    The design and preparation of an ultrathin dual-band metamaterial absorber whose resonant frequency located at radar wave (20 GHz-60 GHz) is presented in this paper. The absorber is composed of a 2-D periodic sandwich featured with two concentric annuluses. The influence on the absorber's performance produced by resonant cell's structure size and material parameters was numerically simulated and analyzed based on the standard full wave finite integration technology in CST. Laser ablation process was adopted to prepare the designed absorber on epoxy resin board coated with on double plane of copper with a thickness that is 1/30 and 1/50 of the resonant wavelength at a resonant frequency of 30.51 GHz and 48.15 GHz. The full width at half maximum (FWHM) reached 2.2 GHz and 2.35 GHz and the peak of the absorptance reached 99.977%. The ultrathin absorber is nearly omnidirectional for all polarizations. The test results of prepared sample testify the designed absorber's excellent absorbing performance forcefully. The absorber expands inspirations of radar stealth in military domain due to its flexible design, cost-effective and other outstanding properties.

  4. Tunable metamaterial dual-band terahertz absorber

    NASA Astrophysics Data System (ADS)

    Luo, C. Y.; Li, Z. Z.; Guo, Z. H.; Yue, J.; Luo, Q.; Yao, G.; Ji, J.; Rao, Y. K.; Li, R. K.; Li, D.; Wang, H. X.; Yao, J. Q.; Ling, F. R.

    2015-11-01

    We report a design of a temperature controlled tunable dual band terahertz absorber. The compact single unit cell consists of two nested closed square ring resonators and a layer metallic separated by a substrate strontium titanate (STO) dielectric layer. It is found that the absorber has two distinctive absorption peaks at frequencies 0.096 THz and 0.137 THz, whose peaks are attained 97% and 75%. Cooling the absorber from 400 K to 250 K causes about 25% and 27% shift compared to the resonance frequency of room temperature, when we cooling the temperature to 150 K, we could attained both the two tunabilities exceeding 53%. The frequency tunability is owing to the variation of the dielectric constant of the low-temperature co-fired ceramic (LTCC) substrate. The mechanism of the dual band absorber is attributed to the overlapping of dual resonance frequencies, and could be demonstrated by the distributions of the electric field. The method opens up avenues for designing tunable terahertz devices in detection, imaging, and stealth technology.

  5. Dual band metamaterial perfect absorber based on artificial dielectric "molecules".

    PubMed

    Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-07-13

    Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of these dual band metamaterial absorbers proposed were based on resonances of metal patterns. Here, we numerically and experimentally demonstrate a dual band metamaterial perfect absorber composed of artificial dielectric "molecules" with high symmetry. The artificial dielectric "molecule" consists of four "atoms" of two different sizes corresponding to two absorption bands with near unity absorptivity. Numerical and experimental absorptivity verify that the dual-band metamaterial absorber is polarization insensitive and can operate in wide-angle incidence.

  6. Absorption enhancement of a dual-band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Zhong, Min; Han, Gui Ming; Liu, Shui Jie; Xu, Bang Li; Wang, Jie; Huang, Hua Qing

    2017-02-01

    In this paper, we propose and fabricate a dual-band metamaterial absorber in 6-24 THz region. Electric field distribution reveal that the first absorption band is obtained from localized surface plasmon (LSP) modes which are excited both on inside and outside edges of each circular-patterned metal-dielectric stack, while the second absorption band is excited by LSP modes on outside edges of each stack. Measured results indicate that the absorption band width can be tuned by increasing the radius of circular-patterned layers or reducing the thickness of dielectric spacing layers. Moreover, the designed dual-band metamaterial absorber is independent on circular-patterned dielectric layer combinations.

  7. Miniaturization for ultrathin metamaterial perfect absorber in the VHF band.

    PubMed

    Khuyen, Bui Xuan; Tung, Bui Son; Yoo, Young Joon; Kim, Young Ju; Kim, Ki Won; Chen, Liang-Yao; Lam, Vu Dinh; Lee, YoungPak

    2017-03-22

    An efficient resolution for ultrathin metamaterial perfect absorber (MPA) is proposed and demonstrated in the VHF radio band (30-300 MHz). By adjusting the lumped capacitors and the through vertical interconnects, the absorber is miniaturized to be only λ/816 and λ/84 for its thickness and periodicity with respect to the operating wavelength (at 102 MHz), respectively. The detailed simulation and calculation show that the MPA can maintain an absorption rate over 90% in a certain range of incident angle and with a wide variation of capacitance. Additionally, we utilized the advantages of the initial single-band structure to realize a nearly perfect dual-band absorber in the same range. The results were confirmed by both simulation and experiment at oblique incidence angles up to 50°. Our work is expected to contribute to the actualization of future metamaterial-based devices working at radio frequency.

  8. Miniaturization for ultrathin metamaterial perfect absorber in the VHF band

    PubMed Central

    Khuyen, Bui Xuan; Tung, Bui Son; Yoo, Young Joon; Kim, Young Ju; Kim, Ki Won; Chen, Liang-Yao; Lam, Vu Dinh; Lee, YoungPak

    2017-01-01

    An efficient resolution for ultrathin metamaterial perfect absorber (MPA) is proposed and demonstrated in the VHF radio band (30–300 MHz). By adjusting the lumped capacitors and the through vertical interconnects, the absorber is miniaturized to be only λ/816 and λ/84 for its thickness and periodicity with respect to the operating wavelength (at 102 MHz), respectively. The detailed simulation and calculation show that the MPA can maintain an absorption rate over 90% in a certain range of incident angle and with a wide variation of capacitance. Additionally, we utilized the advantages of the initial single-band structure to realize a nearly perfect dual-band absorber in the same range. The results were confirmed by both simulation and experiment at oblique incidence angles up to 50°. Our work is expected to contribute to the actualization of future metamaterial-based devices working at radio frequency. PMID:28327658

  9. Miniaturization for ultrathin metamaterial perfect absorber in the VHF band

    NASA Astrophysics Data System (ADS)

    Khuyen, Bui Xuan; Tung, Bui Son; Yoo, Young Joon; Kim, Young Ju; Kim, Ki Won; Chen, Liang-Yao; Lam, Vu Dinh; Lee, Youngpak

    2017-03-01

    An efficient resolution for ultrathin metamaterial perfect absorber (MPA) is proposed and demonstrated in the VHF radio band (30–300 MHz). By adjusting the lumped capacitors and the through vertical interconnects, the absorber is miniaturized to be only λ/816 and λ/84 for its thickness and periodicity with respect to the operating wavelength (at 102 MHz), respectively. The detailed simulation and calculation show that the MPA can maintain an absorption rate over 90% in a certain range of incident angle and with a wide variation of capacitance. Additionally, we utilized the advantages of the initial single-band structure to realize a nearly perfect dual-band absorber in the same range. The results were confirmed by both simulation and experiment at oblique incidence angles up to 50°. Our work is expected to contribute to the actualization of future metamaterial-based devices working at radio frequency.

  10. Dual band metamaterial perfect absorber based on Mie resonances

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoming; Lan, Chuwen; Bi, Ke; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-08-01

    We numerically and experimentally demonstrated a polarization insensitive dual-band metamaterial perfect absorber working in wide incident angles based on the two magnetic Mie resonances of a single dielectric "atom" with simple structure. Two absorption bands with simulated absorptivity of 99% and 96%, experimental absorptivity of 97% and 94% at 8.45 and 11.97 GHz were achieved due to the simultaneous magnetic and electric resonances in dielectric "atom" and copper plate. Mie resonances of dielectric "atom" provide a simple way to design metamaterial perfect absorbers with high symmetry.

  11. Dual-band polarization-/angle-insensitive metamaterial absorber

    SciTech Connect

    Xiong, Han; Zhong, Lin-Lin; Luo, Chao-Ming; Hong, Jing-Song

    2015-06-15

    A dual-band metamaterial absorber (MA) based on triangular resonators is designed and investigated in this paper. It is composed of a two-dimensional periodic metal-dielectric-metal sandwiches array on a dielectric substrate. The simulation results clearly show that this absorber has two absorption peaks at 14.9 and 18.9 GHz, respectively, and experiments are conducted to verify the proposed designs effectively. For each polarization, the dual-band absorber is insensitive to the incident angle (up to 60°) and the absorption peaks remain high for both transverse electric (TE) and transverse magnetic (TM) radiation. To study the physical mechanism of power loss, the current distribution at the dual absorption peaks is given. The MA proposed in this paper has potential applications in many scientific and martial fields.

  12. Dual-band polarization-/angle-insensitive metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Xiong, Han; Zhong, Lin-Lin; Luo, Chao-Ming; Hong, Jing-Song

    2015-06-01

    A dual-band metamaterial absorber (MA) based on triangular resonators is designed and investigated in this paper. It is composed of a two-dimensional periodic metal-dielectric-metal sandwiches array on a dielectric substrate. The simulation results clearly show that this absorber has two absorption peaks at 14.9 and 18.9 GHz, respectively, and experiments are conducted to verify the proposed designs effectively. For each polarization, the dual-band absorber is insensitive to the incident angle (up to 60°) and the absorption peaks remain high for both transverse electric (TE) and transverse magnetic (TM) radiation. To study the physical mechanism of power loss, the current distribution at the dual absorption peaks is given. The MA proposed in this paper has potential applications in many scientific and martial fields.

  13. Multi-band metamaterial absorber topology for infrared frequency regime

    NASA Astrophysics Data System (ADS)

    Mulla, Batuhan; Sabah, Cumali

    2017-02-01

    In this paper, a new multiband metamaterial absorber design is proposed and the numerical characterization is carried out. The design is composed of three layers with differently sized quadruplets in which the interaction among them causes the multiband absorption response in the infrared frequency regime. In order to characterize the absorber and explain the multiband topology, some parametric studies with respect to the dimensions of the structure are carried out and the contributions of the quadruplets to the absorption spectrum are analyzed. According to the results, it is found that the proposed metamaterial absorber has five bands in the infrared frequency regime with the absorption levels of: 98.90%, 99.39%, 86.46%, 92.80% and 97.96%. Moreover, the polarization dependency of the structure is examined and it is found that the design operates well as a perfect absorber with polarization independency in the studied frequency range.

  14. Infrared Perfect Ultra-narrow Band Absorber as Plasmonic Sensor

    NASA Astrophysics Data System (ADS)

    Wu, Dong; Liu, Yumin; Li, Ruifang; Chen, Lei; Ma, Rui; Liu, Chang; Ye, Han

    2016-11-01

    We propose and numerically investigate a novel perfect ultra-narrow band absorber based on a metal-dielectric-metal-dielectric-metal periodic structure working at near-infrared region, which consists of a dielectric layer sandwiched by a metallic nanobar array and a thin gold film over a dielectric layer supported by a metallic film. The absorption efficiency and ultra-narrow band of the absorber are about 98 % and 0.5 nm, respectively. The high absorption is contributed to localized surface plasmon resonance, which can be influenced by the structure parameters and the refractive index of dielectric layer. Importantly, the ultra-narrow band absorber shows an excellent sensing performance with a high sensitivity of 2400 nm/RIU and an ultra-high figure of merit of 4800. The FOM of refractive index sensor is significantly improved, compared with any previously reported plasmonic sensor. The influences of structure parameters on the sensing performance are also investigated, which will have a great guiding role to design high-performance refractive index sensors. The designed structure has huge potential in sensing application.

  15. Conformal dual-band near-perfectly absorbing mid-infrared metamaterial coating.

    PubMed

    Jiang, Zhi Hao; Yun, Seokho; Toor, Fatima; Werner, Douglas H; Mayer, Theresa S

    2011-06-28

    Metamaterials offer a new approach to create surface coatings with highly customizable electromagnetic absorption from the microwave to the optical regimes. Thus far, efficient metamaterial absorbers have been demonstrated at microwave frequencies, with recent efforts aimed at much shorter terahertz and infrared wavelengths. The present infrared absorbers have been constructed from arrays of nanoscale metal resonators with simple circular or cross-shaped geometries, which provide a single band response. In this paper, we demonstrate a conformal metamaterial absorber with a narrow band, polarization-independent absorptivity of >90% over a wide ±50° angular range centered at mid-infrared wavelengths of 3.3 and 3.9 μm. The highly efficient dual-band metamaterial was realized by using a genetic algorithm to identify an array of H-shaped nanoresonators with an effective electric and magnetic response that maximizes absorption in each wavelength band when patterned on a flexible Kapton and Au thin film substrate stack. This conformal metamaterial absorber maintains its absorption properties when integrated onto curved surfaces of arbitrary materials, making it attractive for advanced coatings that suppress the infrared reflection from the protected surface.

  16. 83. Shock absorber attaching "egg" to the launch control center, ...

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

    83. Shock absorber attaching "egg" to the launch control center, southwest corner - Ellsworth Air Force Base, Delta Flight, Launch Control Facility, County Road CS23A, North of Exit 127, Interior, Jackson County, SD

  17. 86. Shock absorber, top of launch control center, southeast corner ...

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

    86. Shock absorber, top of launch control center, southeast corner - Ellsworth Air Force Base, Delta Flight, Launch Control Facility, County Road CS23A, North of Exit 127, Interior, Jackson County, SD

  18. Circuit modeling of graphene absorber in terahertz band

    NASA Astrophysics Data System (ADS)

    Taghvaee, Hamid Reza; Nasari, Hadiseh; Abrishamian, Mohammad Sadegh

    2017-01-01

    Here we develop and extend a transmission line method (TLM) to analyze the performance of graphene assisted metamaterial (GM) devices working in the terahertz (THz) band. We demonstrate that a circuit model can be presented for different parts of the device including graphene and also the patterned metallic sheet by analyzing the distribution of surface induced current. In pursuit of evaluating the efficiency and accuracy of our proposed method, we compare its results, obtained from an easy to implement MATLAB code for a typical GM absorber with those obtained from full wave simulations. The excellence of the proposed method in terms of computation time (showing more than 3 orders of magnitude reduction in run time) and memory resource besides producing results with acceptable agreement with the results of full wave simulation (with an error less than 5%) versus incident angle, dielectric thickness and chemical potential, nominates it as a promising approach to simulate other graphene-based devices.

  19. 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.

  20. Design of Tunable, Thin, and Wide-band Microwave Absorbers

    DTIC Science & Technology

    2012-04-05

    switchable or tunable radar absorbers, which are very useful in electromagnetic compatibility test facilities, radar camouflage and deception roles, and...applications requires switchable or tunable radar absorbers, which are very useful in electromagnetic compatibility test facilities, radar camouflage ...2012. [2] Q. Zhang and Z. Shen, “A dual-polarized switchable microwave absorber,” IEEE AP- S International Symposium , Chicago, July 2012.

  1. Dual band metamaterial perfect absorber based on artificial dielectric “molecules”

    PubMed Central

    Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-01-01

    Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of these dual band metamaterial absorbers proposed were based on resonances of metal patterns. Here, we numerically and experimentally demonstrate a dual band metamaterial perfect absorber composed of artificial dielectric “molecules” with high symmetry. The artificial dielectric “molecule” consists of four “atoms” of two different sizes corresponding to two absorption bands with near unity absorptivity. Numerical and experimental absorptivity verify that the dual-band metamaterial absorber is polarization insensitive and can operate in wide-angle incidence. PMID:27406699

  2. Analysis and design of triple-band high-impedance surface absorber with periodic diversified impedance

    NASA Astrophysics Data System (ADS)

    Rui Zhang, Guo; Heng Zhou, Pei; Bin Zhang, Hui; Bo Zhang, Lin; Liang Xie, Jian; Jiang Deng, Long

    2013-10-01

    In this paper, a triple-band planar absorber with high-impedance surface (HIS) is designed and fabricated. The absorber structure is composed of polyurethane foam sandwiched between a lossy sheet of frequency selective surfaces (FSS) and a perfect electric conductor. The lossy FSS possesses different resistances in a periodic composite unit as compared with typical HIS absorber. Losses in the FSS are introduced by printing the periodic composite square ring pattern on blank stickers using various resistive inks. Physical mechanism of the HIS absorbers is analyzed by equivalent circuit model and electric field distribution studies. The proposed absorber with periodic composite units offers superimposed triple-band absorption as compared with that of the single units having single- or dual-band absorption characteristics. The reflection loss measurements show that the 90% absorption bandwidth of the HIS absorber is increased by 42% by the proposed composite periodic units.

  3. Genetically modified photosynthetic antenna complexes with blueshifted absorbance bands.

    PubMed

    Fowler, G J; Visschers, R W; Grief, G G; van Grondelle, R; Hunter, C N

    1992-02-27

    Light energy for photosynthesis is collected by the antenna system, creating an excited state which migrates energetically 'downhill'. To achieve efficient migration of energy the antenna is populated with a series of pigments absorbing at progressively redshifted wavelengths. This variety in absorbing species in vivo has been created in a biosynthetically economical fashion by modulating the absorbance behaviour of one kind of (bacterio)chlorophyll molecule. This modulation is poorly understood but has been ascribed to pigment-pigment and pigment-protein interactions. We have examined the relationship between aromatic residues in antenna polypeptides and pigment absorption, by studying the effects of site-directed mutagenesis on a bacterial antenna complex. A clear correlation was observed between the absorbance of bacteriochlorophyll a and the presence of two tyrosine residues, alpha Tyr44 and alpha Tyr45, in the alpha subunit of the peripheral light-harvesting complex of Rhodobacter sphaeroides, a purple photosynthetic bacterium that provides a well characterized system for site-specific mutagenesis. By constructing single (alpha Tyr44, alpha Tyr45----PheTyr) and then double (alpha Tyr44, alpha Tyr45----PheLeu) site-specific mutants, the absorbance of bacteriochlorophyll was blueshifted by 11 and 24 nm at 77 K, respectively. The results suggest that there is a close approach of tyrosine residues to bacteriochlorophyll, and that this proximity may promote redshifts in vivo.

  4. Characteristics of a broad band and thin ferrite absorbing wall

    NASA Astrophysics Data System (ADS)

    Kotsuka, Youji

    The author proposes a method of reducing the thickness of a ferrite absorbing wall and controlling the matching frequency characteristics by applying a DC magnetic field, HDC, perpendicularly to the microwave magnetic field. The matching characteristics of this method are investigated in detail on the basis of experimental data. The thickness reduction of the absorbing is first discussed from the standpoint of scalar permeability. Based upon these investigations, a thinned ferrite absorbing wall has been designed on a trial basis. The synthetic wave-absorbing material consists of a ferrite disk backed with a samarium-cobalt magnetic material generating a static magnetic field. Fairly good VSWR (voltage standing wave ratio) characteristics below 1.2 have been obtained with a total thickness of 3.8 mm in the frequency range from VHF to UHF. As an application of these characteristics, by controlling both the ferrite thickness and DC magnetic field simultaneously, it has been clarified that the matching frequency characteristics are easily exchanged in the broad frequency region.

  5. Simple exponential functions describing the absorbance bands of visual pigment spectra.

    PubMed

    Stavenga, D G; Smits, R P; Hoenders, B J

    1993-05-01

    Literature data for visual pigment spectra are formally treated by assuming that the spectra consist of a summation of absorbance bands, that the shape of the bands is invariant according to the Mansfield-MacNichol transform and that this shape is described by simple exponential functions. A new template for constructing visual pigment spectra from peak wavelengths is derived.

  6. Enhancing Localized Evaporation through Separated Light Absorbing Centers and Scattering Centers.

    PubMed

    Zhao, Dengwu; Duan, Haoze; Yu, Shengtao; Zhang, Yao; He, Jiaqing; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

    2015-11-26

    This report investigates the enhancement of localized evaporation via separated light absorbing particles (plasmonic absorbers) and scattering particles (polystyrene nanoparticles). Evaporation has been considered as one of the most important phase-change processes in modern industries. To improve the efficiency of evaporation, one of the most feasible methods is to localize heat at the top water layer rather than heating the bulk water. In this work, the mixture of purely light absorptive plasmonic nanostructures such as gold nanoparticles and purely scattering particles (polystyrene nanoparticles) are employed to confine the incident light at the top of the solution and convert light to heat. Different concentrations of both the light absorbing centers and the light scattering centers were evaluated and the evaporation performance can be largely enhanced with the balance between absorbing centers and scattering centers. The findings in this study not only provide a new way to improve evaporation efficiency in plasmonic particle-based solution, but also shed lights on the design of new solar-driven localized evaporation systems.

  7. Enhancing Localized Evaporation through Separated Light Absorbing Centers and Scattering Centers

    PubMed Central

    Zhao, Dengwu; Duan, Haoze; Yu, Shengtao; Zhang, Yao; He, Jiaqing; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

    2015-01-01

    This report investigates the enhancement of localized evaporation via separated light absorbing particles (plasmonic absorbers) and scattering particles (polystyrene nanoparticles). Evaporation has been considered as one of the most important phase-change processes in modern industries. To improve the efficiency of evaporation, one of the most feasible methods is to localize heat at the top water layer rather than heating the bulk water. In this work, the mixture of purely light absorptive plasmonic nanostructures such as gold nanoparticles and purely scattering particles (polystyrene nanoparticles) are employed to confine the incident light at the top of the solution and convert light to heat. Different concentrations of both the light absorbing centers and the light scattering centers were evaluated and the evaporation performance can be largely enhanced with the balance between absorbing centers and scattering centers. The findings in this study not only provide a new way to improve evaporation efficiency in plasmonic particle-based solution, but also shed lights on the design of new solar-driven localized evaporation systems. PMID:26606898

  8. Design, simulation, and fabrication of single-/dual-/triple band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Yu, Zetai; Liu, Shouyin; Fang, Chonghua; Huang, Xiaojun; Yang, Helin

    2015-06-01

    Single-/dual-/triple band metamaterial absorbers based on cut wire and square ring are discussed at microwave frequencies. The single-/dual-/triple band characteristics are realized by loading the cut wires in the square ring. The results indicate that the proposed metamaterial absorbers exhibit near-perfect impedance matching with free space and high absorbance of 99.50% at 4.70 GHz for single-band condition, and absorbance of 98.75% and 97.64% at 4.44 and 8.55 GHz, respectively, for dual-band condition. The triple band MMA can achieve the absorbance of 96.94%, 97.91% and 94.83% at 4.48 GHz, 7.81 GHz and 14.05 GHz, respectively. It also exhibits a wide range of angles of incidence for both TE and TM radiation. The physical mechanism of the absorptions is interpreted by the simulated surface current distributions and power-loss of the structures. Microwave experiments are performed to successfully realize these ideas, and measured results are in good agreement with the numerical results.

  9. Creating a Multiband Perfect Metamaterial Absorber at K Frequency Band Using Defects in the Structure

    NASA Astrophysics Data System (ADS)

    Tran, Manh Cuong; Nguyen, Thi Thuy; Ho, Tuan Hung; Do, Hoang Tung

    2017-01-01

    We present a simple method to achieve a multiband perfect metamaterial absorber for use in the K band by applying defects to the absorber structure. Open boundary conditions with an excitation port are used for simulation of the whole considered structure. A defect was then introduced into the structure to obtain multiband absorption. Two perfect absorption peaks were observed at 19.8 GHz and 23.1 GHz for the structure with a defect of 2 × 2 unit cells. The multiple resonance frequencies could be tuned by varying the defect dimensions. In addition, it was found that the absorber structure is insensitive to the polarization angle of the incident electromagnetic wave over a wide range due to the symmetry of the configuration. This represents a simpler method to create a multifrequency absorber compared with previous works. To the best of our knowledge, this is the first study considering the influence of structural defects on the absorption frequencies of a metamaterial absorber.

  10. Ultrathin triple-band polarization-insensitive wide-angle compact metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Shang, Shuai; Yang, Shizhong; Tao, Lu; Yang, Lisheng; Cao, Hailin

    2016-07-01

    In this study, the design, realization, and characterization of an ultrathin triple-band polarization-insensitive wide-angle metamaterial absorber are reported. The metamaterial absorber comprises a periodic array of modified six-fold symmetric snowflake-shaped resonators with strip spiral line load, which is printed on a dielectric substrate backed by a metal ground plane. It is shown that the absorber exhibits three distinct near-unity absorption peaks, which are distributed across C, X, Ku bands, respectively. Owing to the six-fold symmetry, the absorber is insensitive to the polarization of the incident radiation. In addition, the absorber shows excellent absorption performance over wide oblique incident angles for both transverse electric and transverse magnetic polarizations. Simulated surface current and field distributions at the three absorption peaks are demonstrated to understand the absorption mechanism. Particularly, the absorption modes come from the fundamental and high-order dipole resonances. Furthermore, the experimental verification of the designed absorber is conducted, and the measured results are in reasonable agreement with the simulated ones. The proposed ultrathin (˜0.018λ0, λ0 corresponding to the lowest peak absorption frequency) compact (0.168λ0×0.168λ0 corresponding to the area of a unit cell) absorber enables potential applications such as stealth technology, electromagnetic interference and spectrum identification.

  11. Experimental indication for band gap widening of chalcopyrite solar cell absorbers after potassium fluoride treatment

    SciTech Connect

    Pistor, P.; Greiner, D.; Kaufmann, C. A.; Brunken, S.; Gorgoi, M.; Steigert, A.; Calvet, W.; Lauermann, I.; Klenk, R.; Unold, T.; Lux-Steiner, M.-C.

    2014-08-11

    The implementation of potassium fluoride treatments as a doping and surface modification procedure in chalcopyrite absorber preparation has recently gained much interest since it led to new record efficiencies for this kind of solar cells. In the present work, Cu(In,Ga)Se{sub 2} absorbers have been evaporated on alkali containing Mo/soda-lime glass substrates. We report on compositional and electronic changes of the Cu(In,Ga)Se{sub 2} absorber surface as a result of a post deposition treatment with KF (KF PDT). In particular, by comparing standard X-ray photoelectron spectroscopy and synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES), we are able to confirm a strong Cu depletion in the absorbers after the KF PDT which is limited to the very near surface region. As a result of the Cu depletion, we find a change of the valence band structure and a shift of the valence band onset by approximately 0.4 eV to lower binding energies which is tentatively explained by a band gap widening as expected for Cu deficient compounds. The KF PDT increased the open circuit voltage by 60–70 mV compared to the untreated absorbers, while the fill factor deteriorated.

  12. Ultra-thin narrow-band, complementary narrow-band, and dual-band metamaterial absorbers for applications in the THz regime

    NASA Astrophysics Data System (ADS)

    Astorino, Maria Denise; Frezza, Fabrizio; Tedeschi, Nicola

    2017-02-01

    In this paper, ultra-thin narrow-band, complementary narrow-band, and dual-band metamaterial absorbers (MMAs), exploiting the same electric ring resonator configuration, are investigated at normal and oblique incidence for both transverse electric (TE) and transverse magnetic (TM) polarizations, and with different physical properties in the THz regime. In the analysis of the ultra-thin narrow-band MMA, the limit of applicability of the transmission line model has been overcome with the introduction of a capacitance which considers the z component of the electric field. These absorbing structures have shown a wide angular response and a polarization-insensitive behavior due to the introduction of a conducting ground plane and to the four-fold rotational symmetry of the resonant elements around the propagation axis. We have adopted a retrieval procedure to extract the effective electromagnetic parameters of the proposed MMAs and we have compared the simulated and analytical results through the interference theory.

  13. Low-frequency and broad band metamaterial absorber: design, fabrication, and characterization

    NASA Astrophysics Data System (ADS)

    Sun, Liang Kui; Cheng, Hai Feng; Zhou, Yong Jiang; Wang, Jun

    2011-10-01

    We report a metamaterial absorber (MA) with a broad absorption band in the frequency region of 2-4 GHz, whose thickness is not limited to the quarter-wavelength. Theoretical and experimental results show that the absorber has two adjacent absorption apexes at 2.24 and 3.46 GHz, respectively, which are both related to the electric and magnetic resonances of the metamaterial. The absorption is over 68% in the whole wave band of 2-4 GHz provided the thickness of 4 mm. The distributions of the surface currents and the power loss density indicate that the surface currents produced by the electric and magnetic resonances are strongly consumed by the resistive patches. This low-frequency absorber has potential applications in many scientific and martial fields.

  14. Design of a Quad-Band Wide-Angle Microwave Metamaterial Absorber

    NASA Astrophysics Data System (ADS)

    Ren, Yu-Hui; Ding, Jun; Guo, Chen-Jiang; Qu, Yan; Song, Yi-Chuan

    2017-01-01

    We report the design, analysis, fabrication, and measurement of a quad-band microwave metamaterial absorber that exhibits four distinct high absorption peaks at specific resonance frequencies. The proposed structure consists of a metallic hexagonal patch layer on top of a dielectric substrate with a metallic film as bottom layer. The simulation and experimental results show that the absorber presents four distinctive perfect (>90%) absorption peaks up to incidence angle of 40° for both transverse electric and transverse magnetic modes. The results prove that this kind of quad-band absorber has good performance over a wide incidence angle range and is polarization insensitive. Moreover, the experimental and numerical simulation results are essentially in agreement.

  15. Terahertz dual-band metamaterial absorber based on graphene/MgF(2) multilayer structures.

    PubMed

    Su, Zhaoxian; Yin, Jianbo; Zhao, Xiaopeng

    2015-01-26

    We design an ultra-thin terahertz metamaterial absorber based on graphene/MgF(2) multilayer stacking unit cells arrayed on an Au film plane and theoretically demonstrate a dual-band total absorption effect. Due to strong anisotropic permittivity, the graphene/MgF(2) multilayer unit cells possess a hyperbolic dispersion. The strong electric and magnetic dipole resonances between unit cells make the impedance of the absorber match to that of the free space, which induces two total absorption peaks in terahertz range. These absorption peaks are insensitive to the polarization and nearly omnidirectional for the incident angle. But the absorption intensity and frequency depend on material and geometric parameters of the multilayer structure. The absorbed electromagnetic waves are finally converted into heat and, as a result, the absorber shows a good nanosecond photothermal effect.

  16. A polarization-sensitive mid-infrared plasmonic absorber for multi-band resonance

    NASA Astrophysics Data System (ADS)

    Li, Yongqian; Wang, Binbin; Xu, Xiaolun; Su, Lei; Zhou, Zili

    2014-05-01

    The aim of this work is to present a multi-band absorption metamaterials. One dual cross-shape perfect absorber metamaterials (PAMs) was developed to obtain multi-band spectrum at mid-infrared. The PAMs possess three distinct resonant peaks standing independently, which are attributed to the polarization sensitive excitation of plasmonic resonance. The optical parameters retrieved by S-parameters method were investigated, which provides a satisfactory qualitative description of the multiple-band spectra responses. On the other hand, the near-field plasmonic behaviors and redistribution of the electromagnetic field were probed theoretically and numerically into the PAMs structure, which also explains the observed absorption behavior of the PAMs ensemble based upon the microscopic perspective. The multiplex spectrum enables the infrared perfect absorber metamaterials (PAMs) a powerful tool for direct access to vibrational fingerprints of single molecular structure.

  17. Independent polarization and multi-band THz absorber base on Jerusalem cross

    NASA Astrophysics Data System (ADS)

    Arezoomand, Afsaneh Saee; Zarrabi, Ferdows B.; Heydari, Samaneh; Gandji, Navid P.

    2015-10-01

    In this paper, we present the design and simulation of a single and multi-band perfect metamaterial absorber (MA) in the THz region base on Jerusalem cross (JC) and metamaterial load in unit cells. The structures consist of dual metallic layers for allowing near-perfect absorption with absorption peak of more than 99%. In this novel design, four-different shape of Jerusalem cross is presented and by adding L, U and W shape loaded to first structure, we tried to achieve a dual-band absorber. In addition, by good implementation of these loaded, we are able to control the absorption resonance at second resonance at 0.9, 0.7 and 0.85 THz respectively. In the other hand, we achieved a semi stable designing at first resonance between 0.53 and 0.58 THz. The proposed absorber has broadband polarization angle. The surface current modeled and proved the broadband polarization angle at prototype MA. The LC resonance of the metamaterial for Jerusalem cross and modified structures are extracting from equivalent circuit. As a result, proposed MA is useful for THz medical imaging and communication systems and the dual-band absorber has applications in many scientific and technological areas.

  18. Simple design of novel triple-band terahertz metamaterial absorber for sensing application

    NASA Astrophysics Data System (ADS)

    Wang, Ben-Xin; Wang, Gui-Zhen; Sang, Tian

    2016-04-01

    For a general metamaterial absorber, single patterned structure has only one resonance absorption peak. Therefore, a multi-band perfect absorber can be obtained by employing multiple different-sized metallic patterns. However, this kind of design strategy removes the novelty of their resonance mechanism and is also quite troublesome in regard to fabrication. Here, a novel and simple design of a triple-band terahertz absorber formed by only an asymmetric cross is presented. Theoretical results show that the proposed structure has three distinct absorption bands whose peaks are all over 99%. The first two absorption peaks are due to the magnetic resonances of the different sections of the asymmetric cross, and the third peak is based on the surface response of the structure. Moreover, sensing performance of the absorber is investigated in terms of the surrounding index. It is found that the figure of merit and quality factor of the third peak is much larger than those of the first two peaks, which reveals the proposed absorber’s, in particular the third resonance mode of the metamaterial, potential applications in sensing and detection.

  19. Design and experimental verification of a perfect dual-band optical metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Ye, Fenghua; Ye, Huan; Wang, Xiaozhi

    2017-03-01

    A perfect dual-band optical absorber is designed and measured. A low absorption peak (P1) and two high absorption peaks (P2 and P3) are obtained. The P1 peak is excited by the resonance of internal surface plasmon (ISP) mode. The P2 peak is resulted by the coupling of local surface plasma (LSP) modes and the resonance of ISP mode. The P3 peak is excited by the resonance of ISP mode. The damping constant of the gold film is optimization calculated in simulations. Measured results indicate that high absorption performed is obtained with different dielectric layers. The measured metamaterial absorber displays high absorption performed at TM and TE configurations. Moreover, the proposed metamaterial absorber is sensitivity on the change of the refractive index of the environmental media.

  20. Multi-band microwave metamaterial absorber based on coplanar Jerusalem crosses

    NASA Astrophysics Data System (ADS)

    Wang, Guo-Dong; Liu, Ming-Hai; Hu, Xi-Wei; Kong, Ling-Hua; Cheng, Li-Li; Chen, Zhao-Quan

    2014-01-01

    The influence of the gap on the absorption performance of the conventional split ring resonator (SRR) absorber is investigated at microwave frequencies. Our simulated results reveal that the geometry of the square SRR can be equivalent to a Jerusalem cross (JC) resonator and its corresponding metamaterial absorber (MA) is changed to a JC absorber. The JC MA exhibits an experimental absorption peak of 99.1% at 8.72 GHz, which shows an excellent agreement with our simulated results. By simply assembling several JCs with slightly different geometric parameters next to each other into a unit cell, a perfect multi-band absorption can be effectively obtained. The experimental results show that the MA has four distinct and strong absorption peaks at 8.32 GHz, 9.8 GHz, 11.52 GHz and 13.24 GHz. Finally, the multi-reflection interference theory is introduced to interpret the absorption mechanism.

  1. Tunable multiwavelength L-band Brillouin-Erbium fiber laser utilizing passive EDF absorber section

    NASA Astrophysics Data System (ADS)

    Al-Mashhadani, T. F.; Al-Mansoori, M. H.; Jamaludin, M. Z.; Abdullah, F.; Abass, A. K.; Rawi, N. I. M.

    2013-12-01

    We demonstrate a simple tunable L-band multiwavelength Brillouin-Erbium fiber laser that utilizes a short passive erbium doped fiber (PEDF) as an absorber section. The impact of including the PEDF absorber section on the laser tunability is investigated. The proposed laser structure exhibits a wide tuning range of 24.4 nm (from 1583.5 nm to 1607.9 nm) at 1480 nm pump and Brillouin pump powers of 100 and 4 mW, respectively. This tuning range represents a 31% increase compared with a laser without a PEDF absorber section. The average number of stable output channels produced within this wavelength range is 16 channels with a spacing of 0.089 nm.

  2. Independently tunable dual-band perfect absorber based on graphene at mid-infrared frequencies

    DOE PAGES

    Zhang, Yuping; Li, Tongtong; Chen, Qi; ...

    2015-12-22

    We design a dual-band absorber formed by combining two cross-shaped metallic resonators of different sizes within a super-unit-cell arranged in mirror symmetry. Simulations indicate that absorption efficiencies greater than 99% can be achieved at two different frequencies under normal incidence. We also employ a design scheme with graphene integration, which allows independent tuning of individual absorption frequencies by electrostatically changing the Fermi energy of the graphene layer. High absorbance is maintained over a wide incident angle range up to 50 degrees for both TE and TM polarizations. Thus, it enables a promising way to design electrically tunable absorbers, which maymore » contribute toward the realization of frequency selective detectors for sensing applications.« less

  3. Independently tunable dual-band perfect absorber based on graphene at mid-infrared frequencies

    SciTech Connect

    Zhang, Yuping; Li, Tongtong; Chen, Qi; Zhang, Huiyun; O’Hara, John F.; Abele, Ethan; Taylor, Antoinette J.; Chen, Hou-Tong; Azad, Abul K.

    2015-12-22

    We design a dual-band absorber formed by combining two cross-shaped metallic resonators of different sizes within a super-unit-cell arranged in mirror symmetry. Simulations indicate that absorption efficiencies greater than 99% can be achieved at two different frequencies under normal incidence. We also employ a design scheme with graphene integration, which allows independent tuning of individual absorption frequencies by electrostatically changing the Fermi energy of the graphene layer. High absorbance is maintained over a wide incident angle range up to 50 degrees for both TE and TM polarizations. Thus, it enables a promising way to design electrically tunable absorbers, which may contribute toward the realization of frequency selective detectors for sensing applications.

  4. Varied absorption peaks of dual-band metamaterial absorber analysis by using reflection theory

    NASA Astrophysics Data System (ADS)

    Xiong, Han; Yu, Yan-Tao; Tang, Ming-Chun; Chen, Shi-Yong; Liu, Dan-Ping; Ou, Xiang; Zeng, Hao

    2016-03-01

    Cross-resonator metamaterial absorbers (MMA) have been widely investigated from microwave to optical frequencies. However, only part of the factors influencing the absorption properties were analyzed in previous works at the same time. In order to completely understand how the spacer thickness, dielectric parameter and incidence angle affect the absorption properties of the dual-band MMA, two sets of simulation were performed. It was found that with increasing incident angles, the low-frequency absorption peak showed a blue shift, while the high-frequency absorption peaks showed a red shift. However, with the increase in spacer thickness, both of the absorption peaks showed a red shift. By using the reflection theory expressions, the physical mechanism of the cross-resonator MMA was well explained. This method provides an effective way to analyze multi-band absorber in technology.

  5. Achieving a multi-band metamaterial perfect absorber via a hexagonal ring dielectric resonator

    NASA Astrophysics Data System (ADS)

    Li, Li-Yang; Wang, Jun; Du, Hong-Liang; Wang, Jia-Fu; Qu, Shao-Bo

    2015-06-01

    A multi-band absorber composed of high-permittivity hexagonal ring dielectric resonators and a metallic ground plate is designed in the microwave band. Near-unity absorptions around 9.785 GHz, 11.525 GHz, and 12.37 GHz are observed for this metamaterial absorber. The dielectric hexagonal ring resonator is made of microwave ceramics with high permittivity and low loss. The mechanism for the near-unity absorption is investigated via the dielectric resonator theory. It is found that the absorption results from electric and magnetic resonances where enhanced electromagnetic fields are excited inside the dielectric resonator. In addition, the resonance modes of the hexagonal resonator are similar to those of standard rectangle resonators and can be used for analyzing hexagonal absorbers. Our work provides a new research method as well as a solid foundation for designing and analyzing dielectric metamaterial absorbers with complex shapes. Project supported by the National Natural Science Foundation of China (Grant Nos. 61331005, 11204378, 11274389, 11304393, and 61302023), the Aviation Science Foundation of China (Grant Nos. 20132796018 and 20123196015), the Natural Science Foundation for Post-Doctoral Scientists of China (Grant Nos. 2013M532131 and 2013M532221), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2013JM6005), and the Special Funds for Authors of Annual Excellent Doctoral Degree Dissertations of China (Grant No. 201242).

  6. A triple-band, polarization- and incident angle-independent microwave metamaterial absorber with interference theory

    NASA Astrophysics Data System (ADS)

    Chen, Junfeng; Hu, Zhaoyang; Wang, Shengming; Huang, Xiutao; Liu, Minghai

    2016-01-01

    We present the design, fabrication and characterization of an ultrathin triple-band metamaterial absorber (MMA) in the microwave frequencies. The unit cell of the MMA consists of three different sizes of electric split ring resonators (eSRRs) and continuous metal film separated by only 1 mm dielectric substrate. The single-band MMA of this structure is firstly investigated. Then, by tuning the scale factor of the unit cells, the proposed triple-band MMA achieves absorption peaks at 9.85 GHz, 13.05 GHz and 14.93 GHz, respectively. Electric field distributions at three resonant frequencies are investigated to qualitatively analyze the loss mechanism. The further simulated and experimental results indicate that the proposed MMA is also polarization- and incident angle-independent. Finally, the interference theory is introduced to quantitatively analyze the MMA, which provides good insight into the physics behind the absorbing structure. To calculate the absorption rates accurately, we employ a simulation strategy make the near-field coupling between two metallic layers get back (compensation method). The measured absorption spectra show an excellent agreement with the theoretical calculation and simulation results. Therefore, the explanation to the physical mechanism of the triple-band MMA is presented and verified.

  7. A wide-angle and polarization insensitive infrared broad band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Xie, Ting; Chen, Zhong; Ma, Rongyi; Zhong, Min

    2017-01-01

    In this paper, we present the design and experimental demonstration of a broad single-band metamaterial absorber composed of a simple two-dimensional periodic silver-SiO2-silver sandwich array. The experimental results show that a near-perfect absorption band with a bandwidth of approximately 0.4 μm in the THz region is obtained, which is in reasonable agreement with the simulated results. The calculated electric field intensity distributions indicate that the broad absorption band is achieved by plasmonic hybridization of two plasmon resonances: one originates from outward coupling between adjacent unit cells and the other arises from inward coupling between the two sub-structures. The effects of the structural parameters and the SiO2 layer thickness on the broad absorption band are investigated experimentally. The effect of the angle of incidence on the broad absorption band is also investigated experimentally and the absorption band remains high at large angles of incidence (60°), which thus provides more efficient absorption of obliquely incident beams.

  8. Solid analyte and aqueous solutions sensing based on a flexible terahertz dual-band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Yan, Xin; Liang, Lan-Ju; Ding, Xin; Yao, Jian-Quan

    2017-02-01

    A high-sensitivity sensing technique was demonstrated based on a flexible terahertz dual-band metamaterial absorber. The absorber has two perfect absorption peaks, one with a fundamental resonance (f1) of the structure and another with a high-order resonance (f2) originating from the interactions of adjacent unit cells. The quality factor (Q) and figure of merit of f2 are 6 and 14 times larger than that of f1, respectively. For the solid analyte, the changes in resonance frequency are monitored upon variation of analyte thickness and index; a linear relation between the amplitude absorption with the analyte thickness is achieved for f2. The sensitivity (S) is 31.2% refractive index units (RIU-1) for f2 and 13.7% RIU-1 for f1. For the aqueous solutions, the amplitude of absorption decreases linearly with increasing the dielectric constant for the ethanol-water mixture of f1. These results show that the designed absorber cannot only identify a solid analyte but also characterize aqueous solutions through the frequency shift and amplitude absorption. Therefore, the proposed absorber is promising for future applications in high-sensitivity monitoring biomolecular, chemical, ecological water systems, and aqueous biosystems.

  9. Dielectric-based subwavelength metallic meanders for wide-angle band absorbers.

    PubMed

    Shen, Su; Qiao, Wen; Ye, Yan; Zhou, Yun; Chen, Linsen

    2015-01-26

    We propose nano-meanders that can achieve wide-angle band absorption in visible regime. The nano-meander consists of a subwavelength dielectric grating covered by continuous ultra-thin Aluminum film (less than one tenth of the incident wavelength). The excited photonic resonant modes, such as cavity mode, surface plasmonic mode and Rayleigh-Wood anomaly, are discussed in detail. Nearly total resonant absorption due to funneling mechanism in the air nano-groove is almost invariant with large incident angle in transverse magnetic polarization. From both the structural geometry and the nanofabrication point of view, the light absorber has a very simple geometrical structure and it is easy to be integrated into complex photonic devices. The highly efficient angle-robust light absorber can be potential candidate for a range of passive and active photonic applications, including solar-energy harvesting as well as producing artificial colors on a large scale substrate.

  10. Multi-band polarization insensitive metamaterial absorber with dual cross-wires structure

    NASA Astrophysics Data System (ADS)

    Yao, Li-fang; Li, Min-hua; Zhai, Xiao-min; Wang, Hui-bo; Dong, Jian-feng

    2015-11-01

    A five-band metamaterial absorber (MMA) based on a simple planar structure is proposed. It utilizes different areas of a single unit cell to match impedance, and produces different absorptive frequencies. Numerical calculation shows that the MMA has five different absorption peaks at 3.78 GHz, 7.66 GHz, 10.9 GHz, 14.5 GHz and 16.7 GHz, and their absorption rates reach 95.5%, 98.6%, 95.7%, 96.6% and 99.8%, respectively. The proposed structure is polarization insensitive for transverse electric (TE) and transverse magnetic (TM) incident waves. Also, the absorptive characteristics over large incident angles are examined. In addition, we analyze the absorption mechanism by the surface current density and power flow density distributions. This simple structure provides a way to design multi-band MMA, and also saves the cost of fabrication.

  11. The use of high spectral resolution bands for estimating absorbed photosynthetically active radiation (A par)

    NASA Technical Reports Server (NTRS)

    Kim, Moon S.; Daughtry, C. S. T.; Chappelle, E. W.; Mcmurtrey, J. E.; Walthall, C. L.

    1994-01-01

    Most remote sensing estimations of vegetation variables such as Leaf Area Index (LAI), Absorbed Photosynthetically Active Radiation (APAR), and phytomass are made using broad band sensors with a bandwidth of approximately 100 nm. However, high resolution spectrometers are available and have not been fully exploited for the purpose of improving estimates of vegetation variables. A study directed to investigate the use of high spectral resolution spectroscopy for remote sensing estimates of APAR in vegetation canopies in the presence of nonphotosynthetic background materials such as soil and leaf litter is presented. A high spectral resolution method defined as the Chlorophyll Absorption Ratio Index (CARI) was developed for minimizing the effects of nonphotosynthetic materials in the remote estimates of APAR. CARI utilizes three bands at 550, 670, and 700 nm with bandwidth of 10 nm. Simulated canopy reflectance of a range of LAI were generated with the SAIL model using measurements of 42 different soil types as canopy background. CARI obtained from the simulated canopy reflectance was compared with the broad band vegetation indices (Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI), and Simple Ratio (SR)). CARI reduced the effect of nonphotosynthetic background materials in the assessment of vegetation canopy APAR more effectively than broad band vegetation indices.

  12. Expanded graphite—Phenolic resin composites based double layer microwave absorber for X-band applications

    NASA Astrophysics Data System (ADS)

    Gogoi, Jyoti Prasad; Bhattacharyya, Nidhi Saxena

    2014-11-01

    In this investigation, double layer microwave absorbers are designed and developed with paired combination of 5 wt. %, 7 wt. %, 8 wt. %, and 10 wt. % expanded graphite-novolac phenolic resin (EG-NPR) composites, in the frequency range of 8.2-12.4 GHz. The thickness and compositional combination of the two layers constituting the absorber are optimized to achieve minimum value of reflection loss (dB) and a broad microwave absorption bandwidth. Double layer combinations showing -25 dB absorption bandwidth >2 GHz and -30 dB absorption bandwidth >1 GHz are chosen for fabrication. The total thickness of the fabricated double layer microwave absorber is varied from 3 mm to 3.4 mm. Absorption bandwidths at -10 dB, -20 dB, -25 dB and -30 dB are determined for the fabricated structure. The maximum -25 dB and -30 dB absorption bandwidth of 2.47 GHz and 1.77 GHz, respectively, are observed for the double layer structure with (5 wt. %-8 wt. %) EG-NPR composites with total thickness of 3.2 mm, while -10 dB bandwidth covers the entire X-band range.

  13. Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications

    NASA Astrophysics Data System (ADS)

    Yong, Zhengdong; Zhang, Senlin; Gong, Chensheng; He, Sailing

    2016-04-01

    Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10-4 × (λres/n)3. Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics.

  14. Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications

    PubMed Central

    Yong, Zhengdong; Zhang, Senlin; Gong, Chensheng; He, Sailing

    2016-01-01

    Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10−4 × (λres/n)3. Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics. PMID:27046540

  15. Nanosized barium hexaferrite in novolac phenolic resin as microwave absorber for X-band application

    NASA Astrophysics Data System (ADS)

    Ozah, S.; Bhattacharyya, N. S.

    2013-09-01

    Nanosized barium ferrite (BaFe12O19) with Novolac phenolic resin (NPR) is developed as a magnetic absorber for application in the frequency range 8.2-12.4 GHz. The absorption is studied by modifying the microstructural properties of the ferrite inclusion with annealing temperature and its content in the composite. Transmission electron microscopy and X-ray diffraction pattern confirms the formation of hexagonal structure of barium ferrite. The crystallite size of the barium ferrite particles is in nano-range and increases with annealing temperature. The BaFe12O19/NPR composite is prepared with different weight percentage of ferrite inclusions. The complex permittivity and complex permeability is measured at X-band and found to increase with annealing temperature and contents of ferrite inclusion. Theoretical study of reflection loss gives that 2 mm absorber samples are showing the best results for X-band application. Reflection loss measurement of the samples shows absorption peak of -24.61 dB at 10.26 GHz for 30 wt%, -28.39 dB at 9.98 GHz for 40 wt% and -37.06 dB at 9.5 GHz for 50 wt% of BaFe12O19 in NPR matrix.

  16. Ultra-wideband microwave absorber by connecting multiple absorption bands of two different-sized hyperbolic metamaterial waveguide arrays

    PubMed Central

    Yin, Xiang; Long, Chang; Li, Junhao; Zhu, Hua; Chen, Lin; Guan, Jianguo; Li, Xun

    2015-01-01

    Microwave absorbers have important applications in various areas including stealth, camouflage, and antenna. Here, we have designed an ultra-broadband light absorber by integrating two different-sized tapered hyperbolic metamaterial (HMM) waveguides, each of which has wide but different absorption bands due to broadband slow-light response, into a unit cell. Both the numerical and experimental results demonstrate that in such a design strategy, the low absorption bands between high absorption bands with a single-sized tapered HMM waveguide array can be effectively eliminated, resulting in a largely expanded absorption bandwidth ranging from 2.3 to 40 GHz. The presented ultra-broadband light absorber is also insensitive to polarization and robust against incident angle. Our results offer a further step in developing practical artificial electromagnetic absorbers, which will impact a broad range of applications at microwave frequencies. PMID:26477740

  17. Ultra-wideband microwave absorber by connecting multiple absorption bands of two different-sized hyperbolic metamaterial waveguide arrays

    NASA Astrophysics Data System (ADS)

    Yin, Xiang; Long, Chang; Li, Junhao; Zhu, Hua; Chen, Lin; Guan, Jianguo; Li, Xun

    2015-10-01

    Microwave absorbers have important applications in various areas including stealth, camouflage, and antenna. Here, we have designed an ultra-broadband light absorber by integrating two different-sized tapered hyperbolic metamaterial (HMM) waveguides, each of which has wide but different absorption bands due to broadband slow-light response, into a unit cell. Both the numerical and experimental results demonstrate that in such a design strategy, the low absorption bands between high absorption bands with a single-sized tapered HMM waveguide array can be effectively eliminated, resulting in a largely expanded absorption bandwidth ranging from 2.3 to 40 GHz. The presented ultra-broadband light absorber is also insensitive to polarization and robust against incident angle. Our results offer a further step in developing practical artificial electromagnetic absorbers, which will impact a broad range of applications at microwave frequencies.

  18. A super-compact metamaterial absorber cell in L-band

    SciTech Connect

    Cao, Z. X.; Yuan, F. G.; Li, L. H.

    2014-05-14

    A super-compact metamaterial absorber (SMA) unit cell in L band (1–2 GHz) is proposed, which is composed of a pair of electric ring resonator (ERR) and its complementary ERR (CERR) with a high dielectric substrate sandwiched in between. The CERR has a cross sectional area where approximately the etched copper foil in ERR is now retained, and the remaining region is now etched. In contract with quarter-wavelength (λ/4) thickness which is required for conventional absorbers, the largest in-plane dimension and thickness of the SMA cell are only λ/33 and λ/250, respectively, leading to a super compact cell volume. While traditionally the long straight wire is introduced in electric-LC resonators for increasing inductance, the CERR achieves similar inductance with much shorter lengths. Thus, its cell dimensions can be drastically reduced without compromising its performance. In addition, simulations together with an automated phase correction algorithm show that the SMA is a type of metamaterial possessing simultaneous negative electric permittivity (NEP) and negative magnetic permeability (NMP). Further the SMA has a very large imaginary part of the NEP and NMP, resulting in significantly large imaginary part of the refractive index at resonant frequency. These properties are well suited to design excellent absorbers. In addition, numerical results demonstrate that the maximum absorption coefficient of the SMA can reach greater than 99% at resonant frequency, and the full-width half-maximum is roughly 1% of the operating frequency, and a wide incident angle of ±49° over 90% absorption. Meanwhile, it is pointed out that this type of absorber is rather sensitive to polarization characteristic of the incident electromagnetic wave.

  19. A super-compact metamaterial absorber cell in L-band

    NASA Astrophysics Data System (ADS)

    Cao, Z. X.; Yuan, F. G.; Li, L. H.

    2014-05-01

    A super-compact metamaterial absorber (SMA) unit cell in L band (1-2 GHz) is proposed, which is composed of a pair of electric ring resonator (ERR) and its complementary ERR (CERR) with a high dielectric substrate sandwiched in between. The CERR has a cross sectional area where approximately the etched copper foil in ERR is now retained, and the remaining region is now etched. In contract with quarter-wavelength (λ /4) thickness which is required for conventional absorbers, the largest in-plane dimension and thickness of the SMA cell are only λ /33 and λ /250, respectively, leading to a super compact cell volume. While traditionally the long straight wire is introduced in electric-LC resonators for increasing inductance, the CERR achieves similar inductance with much shorter lengths. Thus, its cell dimensions can be drastically reduced without compromising its performance. In addition, simulations together with an automated phase correction algorithm show that the SMA is a type of metamaterial possessing simultaneous negative electric permittivity (NEP) and negative magnetic permeability (NMP). Further the SMA has a very large imaginary part of the NEP and NMP, resulting in significantly large imaginary part of the refractive index at resonant frequency. These properties are well suited to design excellent absorbers. In addition, numerical results demonstrate that the maximum absorption coefficient of the SMA can reach greater than 99% at resonant frequency, and the full-width half-maximum is roughly 1% of the operating frequency, and a wide incident angle of ±49° over 90% absorption. Meanwhile, it is pointed out that this type of absorber is rather sensitive to polarization characteristic of the incident electromagnetic wave.

  20. High power L-band mode-locked fiber laser based on topological insulator saturable absorber.

    PubMed

    Meng, Yichang; Semaan, Georges; Salhi, Mohamed; Niang, Alioune; Guesmi, Khmaies; Luo, Zhi-Chao; Sanchez, Francois

    2015-09-07

    We demonstrate a passive mode-locked Er:Yb doped double-clad fiber laser using a microfiber-based topological insulator (Bi(2)Se(3)) saturable absorber (TISA). By optimizing the cavity loss and output coupling ratio, the mode-locked fiber laser can operate in L-band with high average output power. With the highest pump power of 5 W, 91st harmonic mode locking of soliton bunches with average output power of 308 mW was obtained. This is the first report that the TISA based erbium-doped fiber laser operating above 1.6 μm and is also the highest output power yet reported in TISA based passive mode-locked fiber laser.

  1. X-band microwave absorbing characteristics of multicomponent composites with magnetodielectric fillers

    NASA Astrophysics Data System (ADS)

    Afghahi, Seyyed Salman Seyyed; Jafarian, Mojtaba; Stergiou, Charalampos A.

    2016-12-01

    We have studied the microwave absorbing performance in the X-band (8-12.4 GHz) of epoxy composites filled with magnetic and dielectric oxides and multiwalled carbon nanotubes. To this end, pure cobalt-substituted Ba-hexaferrite and calcium titanate were synthesized with the hydrothermal method in the form of nanosized powder. Moreover, the produced powders were characterized in regard of their structural, morphological and static magnetic properties. For the electromagnetic investigation, composite samples were also prepared with various thicknesses up to 4 mm and two basic filler compositions; namely 30 wt% of BaCoFe11O19 and 30 wt% of the mixture BaCoFe11O19/CaTiO3/carbon nanotubes. The magnetic composites show strong but narrowband reflection losses up to 27.5 dB, whereas the magnetodielectric composites with maximum losses of 15.8 dB possess wider bandwidth of operation, due to improved impedance matching. Furthermore, the characteristic frequency of the maximum losses for these quarter-wavelength absorbers was verified to be in inverse proportion to the layer thickness. These findings are supported by reflectance measurements of the samples both in waveguide and free-space.

  2. Dual-band near-infrared plasmonic perfect absorber assisted by strong coupling between bright-dark nanoresonators

    NASA Astrophysics Data System (ADS)

    Lian, Yudong; Ren, Guobin; Liu, Huaiqing; Gao, Yixiao; Zhu, Bofeng; Wu, Beilei; Jian, Shuisheng

    2016-12-01

    In this paper, a plasmonic structure with subwavelength air groove periodically etched on metallic surface is designed and numerically investigated by using Finite Element Method (FEM). The simulation results reveal that the transverse magnetic (TM) polarized incident wave can be perfectly absorbed by the air grooves due to the metallic ohmic loss of Fabry-Pérot resonance. More importantly, by introducing an additional nanoresonator to form a pair of bright-dark resonators, a dual-band plasmonic nearly-perfect absorber can be achieved and the original single absorption peak splits into two absorption peaks. Moreover, the resonance wavelengths correspond to the absorption peaks can be manipulated by varying the geometric parameters. Furthermore, the proposed absorber is found to have large angle tolerance. This dual-band and angle independent near-infrared plasmonic perfect absorber has potential applications in infrared technology and devices, such as imaging devices, thermal bolometers, solar cells and wavelength selective radiators.

  3. S-band Q-switched fiber laser using MoSe2 saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Ismail, M. A.; Sathiyan, S.; Reduan, S. A.; Ruslan, N. E.; Lee, C. S. J.; Zulkifli, M. Z.; Thambiratnam, K.; Ismail, M. F.; Harun, S. W.

    2017-01-01

    A passively Q-switched S-band fiber laser using Molybdenum Diselenide (MoSe2) saturable absorber (SA) is proposed and demonstrated. The SA is fabricated by depositing MoSe2 onto two fiber ferrules using the drop-cast method before heating and connecting the two fiber ferrules to form the SA. The passively Q-switched fiber laser designed using the MoSe2 SA has an operational range of 1491.0-1502.0 nm. The output pulse train has a pulse-width ranging from 2.0 μs to 1.0 μs and corresponding repetition rate of between 34.5 kHz and 90 kHz with increasing pump powers, as well as a signal-to-noise of about 35.97 dB. The peak performance of the proposed laser is between 1480.0 and 1490.0 nm, corresponding to the first peak gain region with the S-band.

  4. Use of narrow-band spectra to estimate the fraction of absorbed photosynthetically active radiation

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G.; Huemmrich, Karl F.; Goward, Samuel N.

    1990-01-01

    A novel approach is proposed for using high-spectral resolution imagers to estimate the fraction of photosynthetically active radiation adsorbed, f(apar), by vegetated land surfaces. In comparison to approaches using broad-band vegetation indices, the proposed method appears to be relatively insensitive to the reflectance of nonphotosynthetically active material beneath the canopy, such as leaf litter or soil. The method is based on a relationship between the second derivative of the reflectance vs wavelength function for terrestrial vegetation and f(apar). The relationship can be defined by the second derivatives in either of two windows, one in the visible region centered at 0.69 micron, another in the near-infrared region centered at 0.74 micron.

  5. Design and Development of Expanded Graphite-Based Non-metallic and Flexible Metamaterial Absorber for X-band Applications

    NASA Astrophysics Data System (ADS)

    Borah, Dipangkar; Bhattacharyya, Nidhi S.

    2017-01-01

    The possibility of using expanded graphite instead of a metallic layer as unit cells and ground planes for metamaterial absorbers in X-band is investigated. A metamaterial absorber was fabricated on a flexible linear low-density polyethylene substrate using an expanded graphite-based circular ring as the unit cell structure. The unit cell was simulated and optimized for which the metamaterial absorber exhibited 98.9% absorption at 11.22 GHz. The fabricated expanded graphite-based absorber showed a reflection loss of -24.51 dB at 11.56 GHz with -10 dB bandwidth of 0.39 GHz (3.37%). The performance of the same structure with copper was also measured. The expanded graphite-based metamaterial absorber showed enhanced performance as compared to the copper-based metamaterial absorber. The width of the ring was varied to tune the reflection loss. The proposed expanded graphite-based metamaterial absorber possesses the advantages of being ultra-thin, flexible and non-corrosive.

  6. The light-induced carotenoid absorbance changes in Rhodopseudomonas sphaeroides: an analysis and interpretation of the band shifts.

    PubMed

    Symons, M; Swysen, C; Sybesma, C

    1977-12-23

    An analysis has been made of the spectrum of the carotenoid absorption band shift generated by continuous illumination of chromatophores of the GlC-mutant of Rhodopseudomonas sphaeroides at room temperature by means of three computer programs. There appears to be at least two pools of the same carotenoid, only one of which, comprising about 20% of the total carotenoid content, is responsible for the light-induced absorbance changes. The 'remaining' pool absorbs at wavelengths which were about 5 nm lower than those at which the 'changing' pool absorbs. This difference in absorption wavelength could indicate that the two pools are influenced differently by permanent local electric fields. The electrochromic origin of the absorbance changes has been demonstrated directly; the isosbestic points of the absorption difference spectrum move to shorter wavelengths upon lowering of the light-induced electric field. Band shifts up to 1.7 nm were observed. A comparison of the light-induced absorbance changes with a KCl-valinomycin-induced diffusion potential has been used to calibrate the electrochromic shifts. The calibration value appeared to be 137 +/- 6 mV per nm shift.

  7. Six-band terahertz metamaterial absorber based on the combination of multiple-order responses of metallic patches in a dual-layer stacked resonance structure

    PubMed Central

    Wang, Ben-Xin; Wang, Gui-Zhen; Sang, Tian; Wang, Ling-Ling

    2017-01-01

    This paper reports on a numerical study of the six-band metamaterial absorber composed of two alternating stack of metallic-dielectric layers on top of a continuous metallic plane. Six obvious resonance peaks with high absorption performance (average larger than 99.37%) are realized. The first, third, fifth, and the second, fourth, sixth resonance absorption bands are attributed to the multiple-order responses (i.e., the 1-, 3- and 5-order responses) of the bottom- and top-layer of the structure, respectively, and thus the absorption mechanism of six-band absorber is due to the combination of two sets of the multiple-order resonances of these two layers. Besides, the size changes of the metallic layers have the ability to tune the frequencies of the six-band absorber. Employing the results, we also present a six-band polarization tunable absorber through varying the sizes of the structure in two orthogonal polarization directions. Moreover, nine-band terahertz absorber can be achieved by using a three-layer stacked structure. Simulation results indicate that the absorber possesses nine distinct resonance bands, and average absorptivities of them are larger than 94.03%. The six-band or nine-band absorbers obtained here have potential applications in many optoelectronic and engineering technology areas. PMID:28120897

  8. Six-band terahertz metamaterial absorber based on the combination of multiple-order responses of metallic patches in a dual-layer stacked resonance structure

    NASA Astrophysics Data System (ADS)

    Wang, Ben-Xin; Wang, Gui-Zhen; Sang, Tian; Wang, Ling-Ling

    2017-01-01

    This paper reports on a numerical study of the six-band metamaterial absorber composed of two alternating stack of metallic-dielectric layers on top of a continuous metallic plane. Six obvious resonance peaks with high absorption performance (average larger than 99.37%) are realized. The first, third, fifth, and the second, fourth, sixth resonance absorption bands are attributed to the multiple-order responses (i.e., the 1-, 3- and 5-order responses) of the bottom- and top-layer of the structure, respectively, and thus the absorption mechanism of six-band absorber is due to the combination of two sets of the multiple-order resonances of these two layers. Besides, the size changes of the metallic layers have the ability to tune the frequencies of the six-band absorber. Employing the results, we also present a six-band polarization tunable absorber through varying the sizes of the structure in two orthogonal polarization directions. Moreover, nine-band terahertz absorber can be achieved by using a three-layer stacked structure. Simulation results indicate that the absorber possesses nine distinct resonance bands, and average absorptivities of them are larger than 94.03%. The six-band or nine-band absorbers obtained here have potential applications in many optoelectronic and engineering technology areas.

  9. Wide-angle, polarization-independent and dual-band infrared perfect absorber based on L-shaped metamaterial.

    PubMed

    Bai, Yang; Zhao, Li; Ju, Dongquan; Jiang, Yongyuan; Liu, Linhua

    2015-04-06

    We propose a wide-angle, polarization-independent and dual-band infrared perfect metamaterial absorber made of double L-shaped gold patches on a dielectric spacer and opaque gold ground layer. Numerical and experimental results demonstrate that the absorber has two near-unity absorption peaks, which are result from magnetic polariton modes generated at two different resonant wavelengths. In addition, the proposed structure also shows good absorption stability in a wide range of incident anglesθfor both TE and TM incidences at azimuthal angle φ = 0°. Moreover, we demonstrate that such structure has good absorption stability for a wide range of azimuthal angles due to the excitation of perpendicular magnetic polariton modes within the asymmetric double L-shaped structure. Such structure will assist in designing magnetic polaritons absorbing element for infrared spectroscopy and imaging.

  10. Novel approach for designing a thin and broadband microwave absorber in Ku band based on substituted M-hexaferrites

    NASA Astrophysics Data System (ADS)

    Afghahi, Seyyed Salman Seyyed; Jafarian, Mojtaba; Atassi, Yomen

    2016-12-01

    The design of novel microwave absorbers in the Ku band is still challenging. The aim of this work is to report the design of a new Ku absorber based on the combination of three M-hexaferrites with the formula of BaX0.3Y0.3Cr0.3Fe11.1O19 (XY=Co2+Zr4+, Zn2+Ti4+, Mn2+Ce4+), 15 wt% of each in epoxy matrix. The results indicate the formation of a broadband absorber with a reflection loss (RL) lower than -10 dB over the whole bandwidth 13.75-18 GHz. It has three matching frequencies (14.2, 15.3 and 16.8 GHz) with RL (-29.2, -21.5 and -24.7 dB, respectively) at a matching thickness of only 2.5 mm. This is to be compared with the RL of the absorbers based on 45 wt% of each ferrite alone in epoxy matrix are (-15, -28.8 and -20 dB, respectively) at matching frequency of (14.15, 13.55 and 16.5 GHz) and a matching thickness of 4 mm. This favorable performance resulting from combining the three ferrites within the absorber may be attributed to the enhanced exchange coupling interactions between the three powders of distinct magnetic characteristics.

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

    NASA Astrophysics Data System (ADS)

    Dwyer, Dan

    2011-12-01

    CuInGaSe2 (CIGS) device efficiencies are the highest of the thin film absorber materials (vs. CdTe, alpha-Si, CuInSe2). However, the band gap of the highest efficiency CIGS cells deviates from the expected ideal value predicted by models [1]. Widening the band gap to the theoretically ideal value is one way to increase cell efficiencies. Widening the band gap can be accomplished in two ways; by finding a solution to the Ga-related defects which limit the open circuit voltage at high Ga ratios, or by utilizing different elemental combinations to form an alternative high band gap photoactive Cu-chalcopyrite (which includes any combination of the cations Cu, Al, Ga, and In along with the anions S, Se, and Te). This thesis focuses on the second option, substituting aluminum for gallium in the chalcopyrite lattice to form a CuInAlSe2 (CIAS) film using a sputtering and selenization approach. Both sequential and co-sputtering of metal precursors is performed. Indium was found to be very mobile during both sputtering processes, with a tendency to diffuse to the film surface even when deposited as the base layer in a sequential sputtering process. Elemental diffusion was controlled to a degree using thicker Cu top layer in co-sputtering. The greater thermal conductivity of stainless steel foil (16 W/mK) vs. glass (0.9-1.3 W/mK) can also be used to limit indium diffusion, by keeping the substrate cooler during sputtering. In both sputtering methods aluminum is deposited oxygen-free by capping the film with a Cu capping layer in combination with controlling the indium diffusion. Selenization of metal precursor films is completed using two different techniques. The first is a thermal evaporation approach from a heated box source (method 1 -- reactive thermal evaporation (RTE-Se)). The second is batch selenization using a heated tube furnace (method 2 -- batch selenization). Some batch selenized precursors were capped with ˜ 1mum of selenium. In both selenization methods

  12. Strong coupling of plasmon and nanocavity modes for dual-band, near-perfect absorbers and ultrathin photovoltaics

    SciTech Connect

    Hagglund, Carl; Zeltzer, Gabriel; Ruiz, Ricardo; Wangperawong, Artit; Roelofs, Katherine E.; Bent, Stacey F.

    2016-01-29

    In this study, when optical resonances interact strongly, hybridized modes are formed with mixed properties inherited from the basic modes. Strong coupling therefore tends to equalize properties such as damping and oscillator strength of the spectrally separate resonance modes. This effect is here shown to be very useful for the realization of near-perfect dual-band absorption with ultrathin (~10 nm) layers in a simple geometry. Absorber layers are constructed by atomic layer deposition of the heavy-damping semiconductor tin monosulfide (SnS) onto a two-dimensional gold nanodot array. In combination with a thin (55 nm) SiO2 spacer layer and a highly reflective Al film on the back, a semiopen nanocavity is formed. The SnS-coated array supports a localized surface plasmon resonance in the vicinity of the lowest order antisymmetric Fabry–Perot resonance of the nanocavity. Very strong coupling of the two resonances is evident through anticrossing behavior with a minimum peak splitting of 400 meV, amounting to 24% of the plasmon resonance energy. The mode equalization resulting from this strong interaction enables simultaneous optical impedance matching of the system at both resonances and thereby two near-perfect absorption peaks, which together cover a broad spectral range. When paired with the heavy damping from SnS band-to-band transitions, this further enables approximately 60% of normal incident solar photons with energies exceeding the band gap to be absorbed in the 10 nm SnS coating. Thereby, these results establish a distinct relevance of strong coupling phenomena to efficient, nanoscale photovoltaic absorbers and more generally for fulfilling a specific optical condition at multiple spectral positions.

  13. Strong coupling of plasmon and nanocavity modes for dual-band, near-perfect absorbers and ultrathin photovoltaics

    DOE PAGES

    Hagglund, Carl; Zeltzer, Gabriel; Ruiz, Ricardo; ...

    2016-01-29

    In this study, when optical resonances interact strongly, hybridized modes are formed with mixed properties inherited from the basic modes. Strong coupling therefore tends to equalize properties such as damping and oscillator strength of the spectrally separate resonance modes. This effect is here shown to be very useful for the realization of near-perfect dual-band absorption with ultrathin (~10 nm) layers in a simple geometry. Absorber layers are constructed by atomic layer deposition of the heavy-damping semiconductor tin monosulfide (SnS) onto a two-dimensional gold nanodot array. In combination with a thin (55 nm) SiO2 spacer layer and a highly reflective Almore » film on the back, a semiopen nanocavity is formed. The SnS-coated array supports a localized surface plasmon resonance in the vicinity of the lowest order antisymmetric Fabry–Perot resonance of the nanocavity. Very strong coupling of the two resonances is evident through anticrossing behavior with a minimum peak splitting of 400 meV, amounting to 24% of the plasmon resonance energy. The mode equalization resulting from this strong interaction enables simultaneous optical impedance matching of the system at both resonances and thereby two near-perfect absorption peaks, which together cover a broad spectral range. When paired with the heavy damping from SnS band-to-band transitions, this further enables approximately 60% of normal incident solar photons with energies exceeding the band gap to be absorbed in the 10 nm SnS coating. Thereby, these results establish a distinct relevance of strong coupling phenomena to efficient, nanoscale photovoltaic absorbers and more generally for fulfilling a specific optical condition at multiple spectral positions.« less

  14. Electrochromic responses of carotenoid absorbance bands in purified light-harvesting complexes from Rhodobacter capsulatus reconstituted into liposomes.

    PubMed

    Goodwin, M G; Jackson, J B

    1993-09-13

    Light-Harvesting Complexes I and II (LHI and LHII) were extracted from chromatophores of Rhodobacter capsulatus, purified in Triton X-100 and reconstituted into phospholipid vesicles. Application of membrane potentials (K+ diffusion potentials) to LHII proteoliposomes led to absorbance changes in the carotenoid bands which were spectrally similar to those in chromatophores. These (electrochromic) absorbance changes were linear with the applied membrane potential between -107 mV and +105 mV. The data were consistent with the existence of two forms of carotenoid in LHII. One form, comprising 2/3 of the total and with a long wavelength absorbance maximum at 510 nm, was not significantly affected by membrane potential. The other component, comprising 1/3 of the total and with a long wavelength absorbance maximum at 516.5 nm, was shifted by approx. 1.6 nm to the red by a membrane potential of 105 mV. Reduction of the B800 bacteriochlorophyll in LHII with NaBH4 before reconstitution did not affect the absorbance spectrum of the carotenoids and it did not affect their response to applied membrane potentials in proteoliposomes. Although the electrochromically-sensitive carotenoids might be associated with B800, interactions with the bacteriochlorophyll are perhaps not the cause of the polarisation of the carotenoid that is responsible for the linearity of the response. The carotenoids in reconstituted LHI complexes were not detectably electrochromic. The electrochromic absorbance changes of carotenoids in LHII could be useful for membrane potential measurement in liposomes containing ion-translocating proteins.

  15. Experimental demonstration of terahertz metamaterial absorbers with a broad and flat high absorption band.

    PubMed

    Huang, Li; Chowdhury, Dibakar Roy; Ramani, Suchitra; Reiten, Matthew T; Luo, Sheng-Nian; Taylor, Antoinette J; Chen, Hou-Tong

    2012-01-15

    We present the design, numerical simulations and experimental measurements of terahertz metamaterial absorbers with a broad and flat absorption top over a wide incidence angle range for either transverse electric or transverse magnetic polarization depending on the incident direction. The metamaterial absorber unit cell consists of two sets of structures resonating at different but close frequencies. The overall absorption spectrum is the superposition of individual components and becomes flat at the top over a significant bandwidth. The experimental results are in excellent agreement with numerical simulations.

  16. Expanded graphite/Novolac phenolic resin composite as single layer electromagnetic wave absorber for x-band applications

    NASA Astrophysics Data System (ADS)

    Gogoi, Jyoti P.; Bhattacharyya, Nidhi Saxena

    2013-01-01

    Expanded graphite/novolac phenolic resin (EG/NPR) composites are developed as dielectric absorbers with 4mm thickness and its microwave absorption ability studied in the frequency range 8.4 to 12.4 GHz. A high reflection loss ~ -43 dB is observed at 12.4 GHz for 5 wt. % EG/NPR composites. With the increase in EG concentration in the composite the reflection loss decreases and the absorption peak shifts towards lower frequency. 7 wt. %, 8 wt. % and 10 wt. % composites shows a 10dB absorption bandwidth of order of 1GHz. Light weight EG/NPR composite shows potential to be used as cost-effective broadband microwave absorber over the X-band.

  17. Theoretical model of homogeneous metal-insulator-metal perfect multi-band absorbers for the visible spectrum

    NASA Astrophysics Data System (ADS)

    Kajtár, G.; Kafesaki, M.; Economou, E. N.; Soukoulis, C. M.

    2016-02-01

    We present a rigorous study of the perfect absorption properties of metal-insulator-metal (MIM) structures in the visible spectrum. We provide a derivation (based on the transfer matrix method) and analysis of the conditions for which the perfect absorption occurs. We show that these conditions are fulfilled when the incident wave excites the eigenmodes of the structure. The quantitative analysis allows us to design specific perfect absorbers for our needs. The analytical model is verified by rigorous simulations based on rigorous coupled wave analysis, which demonstrate also the angle and polarization insensitivity of the absorption properties of such a structure. Employing the MIM approach and results, we also investigate and demonstrate multiple perfect absorption bands and broad-band absorption in properly designed multilayer metal-insulator systems.

  18. Reconstructing the energy band electronic structure of pulsed laser deposited CZTS thin films intended for solar cell absorber applications

    NASA Astrophysics Data System (ADS)

    Pandiyan, Rajesh; Oulad Elhmaidi, Zakaria; Sekkat, Zouheir; Abd-lefdil, Mohammed; El Khakani, My Ali

    2017-02-01

    We report here on the use of pulsed KrF-laser deposition (PLD) technique for the growth of high-quality Cu2ZnSnS4 (CZTS) thin films onto Si, and glass substrates without resorting to any post sulfurization process. The PLD-CZTS films were deposited at room temperature (RT) and then subjected to post annealing at different temperatures ranging from 200 to 500 °C in Argon atmosphere. The X-ray diffraction and Raman spectroscopy confirmed that the PLD films crystallize in the characteristic kesterite CZTS structure regardless of their annealing temperature (Ta), but their crystallinity is much improved for Ta ≥ 400 °C. The PLD-CZTS films were found to exhibit a relatively dense morphology with a surface roughness (RMS) that increases with Ta (from ∼14 nm at RT to 70 nm at Ta = 500 °C with a value around 40 nm for Ta = 300-400 °C). The optical bandgap of the PLD-CZTS films, was derived from UV-vis transmission spectra analysis, and found to decrease from 1.73 eV for non-annealed films to ∼1.58 eV for those annealed at Ta = 300 °C. These band gap values are very close to the optimum value needed for an ideal solar cell absorber. In order to achieve a complete reconstruction of the one-dimensional energy band structure of these PLD-CZTS absorbers, we have combined both XPS and UPS spectroscopies to determine their chemical bondings, the position of their valence band maximum (relative to Fermi level), and their work function values. This enabled us to sketch out, as accurately as possible, the band alignment of the heterojunction interface formed between CZTS and both CdS and ZnS buffer layer materials.

  19. B-side electron transfer promoted by absorbance of multiple photons in Rhodobacter sphaeroides R-26 reaction centers

    SciTech Connect

    Lin, S.; Jackson, J.A.; Taguchi, A.K.W.; Woodbury, N.W.

    1999-06-03

    Femtosecond transient absorbance spectra of quinone-depleted Rhodobacter sphaeroides R-26 reaction centers in the Q{sub X} transition region have been measured at 15 K under various excitation conditions. This study focuses on the excitation wavelength dependence and excitation intensity dependence of the formation of charge-separated states on the A- and B-side of the reaction center, judging from the bleaching of the 533 nm (B-side) and 544 nm (A-side) ground-state transitions of the reaction center bacteriopheophytins (H{sub A} and H{sub B}). Upon low-intensity selective excitation directly into the bacteriopheophytin Q{sub Y} transitions (near 760 nm), bleaching of both ground-state bacteriopheophytin Q{sub X} transitions appeared immediately, showing that initially either the A- or B-side bacteriopheophytin could be excited. However, both excited states ultimately resulted in P{sup +}H{sub A}{sup {minus}} formation under these conditions. Low-intensity excitation at any of the various wavelengths showed no difference in the kinetics of the A-side charge separation forming P{sup +}H{sub A}{sup {minus}} and no substantial formation of the B-side charge-separated state, P{sup +}H{sub B}{sup {minus}}. In contrast, high-intensity 595 nm excitation resulted in substantial long-lived bleaching of the B-side bacteriopheophytin ground-state transition at 533 nm. This 533 nm bleaching was formed with essentially the same time constant as the bleaching at 544 nm due to A-side charge separation. Both bleaching bands persisted at the longest times measured in quinone-removed reaction centers. The long-lived bleaching at 533 nm using high-intensity excitation most likely represents the formation of P{sup +}H{sub B}{sup {minus}} with a relative yield of nearly 40%. One possible mechanism for B-side electron transfer is that two-photon excitation of the reaction center resulting in the state P{sup *}B{sub B}{sup *} makes P{sup +}B{sub B}{sup {minus}} thermodynamically

  20. Band to band tunneling in III-V semiconductors: Implications of complex band structure, strain, orientation, and off-zone center contribution

    SciTech Connect

    Majumdar, Kausik

    2014-05-07

    In this paper, we use a tight binding Hamiltonian with spin orbit coupling to study the real and complex band structures of relaxed and strained GaAs. A simple d orbital on-site energy shift coupled with appropriate scaling of the off-diagonal terms is found to correctly reproduce the band-edge shifts with strain. Four different 〈100〉 strain combinations, namely, uniaxial compressive, uniaxial tensile, biaxial compressive, and biaxial tensile strain are studied, revealing rich valence band structure and strong relative orientation dependent tunneling. It is found that complex bands are unable to provide unambiguous tunneling paths away from the Brillouin zone center. Tunneling current density distribution over the Brillouin zone is computed using non-equilibrium Green's function approach elucidating a physical picture of band to band tunneling.

  1. Structural and magnetic properties of La3+ substituted barium-natural nanoferrites as microwave absorber in X-band

    NASA Astrophysics Data System (ADS)

    Widanarto, W.; Amirudin, F.; Ghoshal, S. K.; Effendi, M.; Cahyanto, W. T.

    2017-03-01

    Selection of proper microwave absorbers in the X-band is vital to prevent the interference issues that often damage devices and cause signal degradation. In this spirit, we prepared three La3+ substituted barium-natural nanoferrites (BNFs) samples with chemical composition of BaO:(x)La2O3:(6-x)Fe2O3 (x=0, 0.1, 0.2 in mol) via solid-state reaction route. Synthesized samples were characterized via SEM, XRD, VSM, and VNA measurements to determine the La3+ ions concentration dependent variation in the structural, magnetic and microwave absorption properties. Transmission/reflection line (TRL) method was used to evaluate the samples reflection loss. La3+ free samples sintered at 1100 °C revealed hexagonal BaFe12O19 and rhombohedral Fe2O3 phases. SEM images displayed the growth of new particle with the average size of 0.2 - 0.8 μm as filler in BNFs. Furthermore, an incorporation of La3+ into the BNF system manifested the emergence of new BaLa2Fe2O7 tetragonal crystal phase. The average crystallite size of BNF was found to decrease with increasing La3+ ion concentrations. Conversely, substitution of La3+ in the BNF caused insignificant changes in the magnetic properties, the real part of the relative permittivity and the natural resonance frequency. Meanwhile, a reasonable shift in the microwave frequency absorption and enhancement in the reflection loss was evidenced due to the inclusion of La3+. BNF sample containing 0.2 mol La2O3 exhibited a saturation magnetization and magnetic field anisotropy of 19.02 and 0.36 T, respectively, where the maximum reflection loss is discerned to be -26.61 dB at 10.87 GHz with 1.25 GHz bandwidth. This new class of ferrites may be prospective for microwave absorber in the X-band.

  2. Dual-band microwave absorption properties of metamaterial absorber composed of split ring resonator on carbonyl iron powder composites

    NASA Astrophysics Data System (ADS)

    Lim, Jun-Hee; Ryu, Yo-Han; Kim, Sung-Soo

    2015-05-01

    This study investigated the dual-band absorption properties of metamaterial absorbers composed of a split ring resonator (SRR) on a grounded magnetic substrate. Polymer composites of carbonyl iron powders (CIP) of high permeability and magnetic loss were used as the substrate material. Computational tools were used to model the interaction between electromagnetic waves and materials with the SRR structure. For perpendicular polarization with an electric field (E) perpendicular to the SRR gap, dualband absorption peaks are predicted in the simulation result of reflection loss. Magnetic resonance resulting from antiparallel currents between the SRR and the ground plane is observed at the frequencies of two absorption peaks. The first strong absorption peak at the lower frequency (3.3 GHz) is due to magnetic resonance at the wire part of the SRR. The second absorption peak at the higher frequency (7.2 GHz) is due to magnetic resonance at the SRR split gap. The decreased capacitance with increased gap spacing moves the second absorption frequency to higher frequencies, while the first absorption peak is invariant with gap spacing. In the case of dual gaps at the opposite sides of the SRR, a single absorption peak is predicted due to the elimination of low-frequency resonance. For parallel polarization with the E-field parallel to the SRR gap, a single absorption peak is predicted, corresponding to magnetic resonance at the SRR wire.[Figure not available: see fulltext.

  3. A generation/recombination model assisted with two trap centers in wide band-gap semiconductors

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Ken; Kuwabara, Takuhito; Uda, Tsuyoshi

    2013-03-01

    A generation/recombination (GR) model assisted with two trap centers has been proposed for studying reverse current on pn junctions in wide band-gap semiconductors. A level (Et1) has been assumed to be located near the bottom of the conduction band and the other (Et2) to be near the top of the valence band. The GR model has been developed by assuming (1) a high-electric field; F, (2) a short distance; d, between trap centers, (3) reduction in an energy-difference; Δeff = |Et1 - Et2| - eFd, and (4) hopping or tunneling conductions between trap centers with the same energy-level (Δeff ≈ 0). The GR rate has been modeled by trap levels, capture cross-sections, trap densities, and transition rate between trap centers. The GR rate, about 1010 greater than that estimated from the single-level model, has been predicted on pn junctions in a material with band-gap of 3.1 eV. Device simulations using the proposed GR model have been demonstrated for SiC diodes with and without a guard ring. A reasonable range for reverse current at room temperature has been simulated and stable convergence has been obtained in a numerical scheme for analyzing diodes with an electrically floating region.

  4. Broad-band efficiency calibration of ITER bolometer prototypes using Pt absorbers on SiN membranes

    NASA Astrophysics Data System (ADS)

    Meister, H.; Willmeroth, M.; Zhang, D.; Gottwald, A.; Krumrey, M.; Scholze, F.

    2013-12-01

    The energy resolved efficiency of two bolometer detector prototypes for ITER with 4 channels each and absorber thicknesses of 4.5 μm and 12.5 μm, respectively, has been calibrated in a broad spectral range from 1.46 eV up to 25 keV. The calibration in the energy range above 3 eV was performed against previously calibrated silicon photodiodes using monochromatized synchrotron radiation provided by five different beamlines of Physikalische Technische Bundesanstalt at the electron storage rings BESSY II and Metrology Light Source in Berlin. For the measurements in the visible range, a setup was realised using monochromatized halogen lamp radiation and a calibrated laser power meter as reference. The measurements clearly demonstrate that the efficiency of the bolometer prototype detectors in the range from 50 eV up to ≈6 keV is close to unity; at a photon energy of 20 keV the bolometer with the thick absorber detects 80% of the photons, the one with the thin absorber about 50%. This indicates that the detectors will be well capable of measuring the plasma radiation expected from the standard ITER scenario. However, a minimum absorber thickness will be required for the high temperatures in the central plasma. At 11.56 keV, the sharp Pt-L3 absorption edge allowed to cross-check the absorber thickness by fitting the measured efficiency to the theoretically expected absorption of X-rays in a homogeneous Pt-layer. Furthermore, below 50 eV the efficiency first follows the losses due to reflectance expected for Pt, but below 10 eV it is reduced further by a factor of 2 for the thick absorber and a factor of 4 for the thin absorber. Most probably, the different histories in production, storage, and operation led to varying surface conditions and additional loss channels.

  5. Development of FeCoB/Graphene Oxide based microwave absorbing materials for X-Band region

    NASA Astrophysics Data System (ADS)

    Das, Sukanta; Chandra Nayak, Ganesh; Sahu, S. K.; Oraon, Ramesh

    2015-06-01

    This work explored the microwave absorption capability of Graphene Oxide and Graphene Oxide coated with FeCoB for stealth technology. Epoxy based microwave absorbing materials were prepared with 30% loading of Graphene Oxide, FeCoB alloy and Graphene Oxide coated with FeCoB. Graphene Oxide and FeCoB were synthesized by Hummer's and Co-precipitation methods, respectively. The filler particles were characterized by FESEM, XRD and Vibrating Sample Magnetometer techniques. Permittivity, permeability and reflection loss values of the composite absorbers were measured with vector network analyzer which showed a reflection loss value of -7.86 dB, at 10.72 GHz, for single layered Graphene Oxide/Epoxy based microwave absorbers which can be correlated to the absorption of about 83.97% of the incident microwave energy. Reflection loss value of FeCoB/Epoxy based microwave absorber showed -13.30 dB at 11.67 GHz, which corresponded to maximum absorption of 93.8%. However, reflection loss values of Graphene Oxide coated with FeCoB/Epoxy based single-layer absorber increased to -22.24 dB at 12.4 GHz which corresponds to an absorption of 99% of the incident microwave energy.

  6. Quantitative photoluminescence of broad band absorbing melanins: a procedure to correct for inner filter and re-absorption effects

    NASA Astrophysics Data System (ADS)

    Riesz, Jennifer; Gilmore, Joel; Meredith, Paul

    2005-07-01

    We report methods for correcting the photoluminescence emission and excitation spectra of highly absorbing samples for re-absorption and inner filter effects. We derive the general form of the correction, and investigate various methods for determining the parameters. Additionally, the correction methods are tested with highly absorbing fluorescein and melanin (broadband absorption) solutions; the expected linear relationships between absorption and emission are recovered upon application of the correction, indicating that the methods are valid. These procedures allow accurate quantitative analysis of the emission of low quantum yield samples (such as melanin) at concentrations where absorption is significant.

  7. Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

    2016-11-01

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

  8. Passively synchronized Q-switched and mode-locked dual-band Tm(3+):ZBLAN fiber lasers using a common graphene saturable absorber.

    PubMed

    Jia, Chenglai; Shastri, Bhavin J; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R; Saad, Mohammed; Chen, Lawrence R

    2016-11-02

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm(3+):ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

  9. Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

    PubMed Central

    Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

    2016-01-01

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications. PMID:27804993

  10. Charge carrier dynamics and recombination in graded band gap CuIn1-xGaxSe2 polycrystalline thin-film photovoltaic solar cell absorbers

    SciTech Connect

    Kuciauskas, Darius; Li, Jian V.; Contreras, Miguel A.; Pankow, Joel; Dippo, Patricia; Young, Matthew; Mansfield, Lorelle M.; Noufi, Rommel; Levi, Dean

    2013-01-01

    We report the results of spectroscopic time-resolved photoluminescence (TRPL) analysis for polycrystalline CuIn1-xGaxSe2 (CIGS) films. On the <5 ns time scale, we investigated minority carrier spatial redistribution from the initial absorption profile near the surface of the films to the conduction band minimum. Based on these data, the estimated minority carrier mobility is 75–230 cm2 V-1s-1. Full TRPL decays were analyzed using models for donor-acceptor pair (DAP) recombination. We estimated that the concentration of DAP recombination centers was 5×1015–1017cm-3. Data also show that Shockley-Reed-Hall and surface recombination are not significant for polycrystalline CIGS absorbers used in high-efficiency photovoltaic solar cells.

  11. Broad Band X-Ray Telescope (BBXRT) Work Station in the Spacelab Payload Operations Control Center

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The primary objective of the STS-35 mission was round the clock observation of the celestial sphere in ultraviolet and X-Ray astronomy with the Astro-1 observatory which consisted of four telescopes: the Hopkins Ultraviolet Telescope (HUT); the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE); the Ultraviolet Imaging Telescope (UIT); and the Broad Band X-Ray Telescope (BBXRT). The Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at the Marshall Space Flight Center (MSFC) was the air/ground communication channel used between the astronauts and ground control teams during the Spacelab missions. Teams of controllers and researchers directed on-orbit science operations, sent commands to the spacecraft, received data from experiments aboard the Space Shuttle, adjusted mission schedules to take advantage of unexpected science opportunities or unexpected results, and worked with crew members to resolve problems with their experiments. Due to loss of data used for pointing and operating the ultraviolet telescopes, MSFC ground teams were forced to aim the telescopes with fine tuning by the flight crew. This photo captures the activity of WUPPE (Wisconsin Ultraviolet Photo-Polarimeter Experiment) data review at the Science Operations Area during the mission. This image shows mission activities at the Broad Band X-Ray Telescope (BBXRT) Work Station in the Science Operations Area (SOA).

  12. Influence of the Cu Content in Cu2ZnSn(S,Se)4 solar cell absorbers on order-disorder related band gap changes

    NASA Astrophysics Data System (ADS)

    Lang, Mario; Renz, Tobias; Mathes, Niklas; Neuwirth, Markus; Schnabel, Thomas; Kalt, Heinz; Hetterich, Michael

    2016-10-01

    We investigate the electronic structure and the radiative recombination in wet-chemically fabricated Cu2ZnSn(S,Se)4 solar cell absorbers utilizing photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy, focusing especially on the effects of varying Cu content. This includes the impact of the latter on the band gap energy and the change in band gap energy related to the order-disorder transition. Characteristic PL and PLE parameters like the energetic position of the PL maximum and the PL yield as a function of the excitation power as well as the PLE tailing parameter do not depend on composition indicating that the nature of the radiative transition is not altered by the Cu content. However, the band gap energy Eg significantly increases as a function of decreasing Cu content. This increase is more pronounced in the disordered than in the ordered atomic arrangement of Cu and Zn atoms in the Cu-Zn planes of the kesterite crystal structure.

  13. Optical band gap of NpO2 and PuO2 from optical absorbance of epitaxial films

    NASA Astrophysics Data System (ADS)

    Mark McCleskey, T.; Bauer, Eve; Jia, Quanxi; Burrell, Anthony K.; Scott, Brian L.; Conradson, Steven D.; Mueller, Alex; Roy, Lindsay; Wen, Xiaodong; Scuseria, Gustavo E.; Martin, Richard L.

    2013-01-01

    We report a solution based synthesis of epitaxial thin films of neptunium oxide and plutonium oxide. Actinides represent a challenge to first principle calculations due to features that arise from f orbital interactions. Conventional semi-local density functional theory predicts NpO2 and PuO2 to be metallic, when they are well known insulators. Improvements in theory are dependent on comparison with accurate measurements of material properties, which in turn demand high-quality samples. The high melting point of actinide oxides and their inherent radioactivity makes single crystal and epitaxial film formation challenging. We report on the preparation of high quality epitaxial actinide films. The films have been characterized through a combination of X-ray diffraction and X-ray absorption fine structure (XANES and EXAFS) measurements. We report band gaps of 2.80 ± 0.1 eV and 2.85 ± 0.1 eV at room temperature for PuO2 and NpO2, respectively, and compare our measurements with state-of-the-art calculations.

  14. Improvement of the performance of microwave X band absorbers based on pure and doped Ba-hexaferrite

    NASA Astrophysics Data System (ADS)

    Seyyed Afghahi, Seyyed Salman; Jafarian, Mojtaba; Salehi, Mohsen; Atassi, Yomen

    2017-01-01

    Optimum Fe/Ba mole ratio is determined in doped Ba-hexaferrite prepared via mechanical activation. X-ray diffractometer (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and vector network analyzer are used to analyze phases, structures, electromagnetic and microwave absorption properties. The mole ratio of Fe/Ba=10 is detected to be optimum for doping and synthesizing the Ba-hexaferrite. In order to achieve high absorption in X band the ions of Zr4+-Sn4+-Ti4+-M2+ (M=Mg2+, Zn2+, Cu2+, Co2+) are used as dopants. The results indicate the formation of single phase Ba-hexaferrite in either pure or doped compounds without any non-magnetic intermediate phases and with spherical and hexagonal morphologies respectively for the pure and doped ferrite. It is found out that BaCo2Zr(SnTi)0.5Fe8O19 compound has the maximum saturation magnetization (49.80 emu/g). Also the composite of BaCo2Zr(SnTi)0.5Fe8O19 50 wt% in epoxy resin exhibits a minimum reflection loss of -29 dB at 12.2 GHz with 2.6 GHz bandwidth.

  15. Optimal design and loss mechanism analysis of microwave absorbing unidirectional SiC fiber composites with broad absorption band and good polarization stability

    NASA Astrophysics Data System (ADS)

    Wan, Guangchao; Jiang, Jianjun; He, Yun; Bie, Shaowei

    2016-04-01

    A microwave-absorbing unidirectional SiC fiber composite with wide absorption and good polarization stability was designed by genetic algorithm. The anisotropic nature of unidirectional fiber composites was considered in the design by characterizing tensor permittivity. This special composite is composed of two kinds of SiC fibers that separately exhibit relatively high conductivity and low conductivity. The electromagnetic loss mechanism of this composite was examined for polarizations that differ in the electric field of the incident wave, applied either in the direction of the fiber or in the transverse direction, perpendicular to the fibers. For both polarizations, the absorption band of our composite can reach 6 GHz and the lowest microwave reflectivity was about -20 dB over a range of 8-18 GHz. When the electric field is polarized parallel to fibers, strong coupling among the high-conductivity fibers can induce a strong current and thus efficiently dissipate the electromagnetic energy. When the electric field is polarized perpendicular to fibers, the electromagnetic loss mechanism in the composite resembles the electric energy loss in capacitors and currents in the transverse direction are obstructed by the fibers resulting in attenuation of the electromagnetic energy in the matrix.

  16. Strong Narrow-Band Luminescence from Silicon-Vacancy Color Centers in Spatially Localized Sub-10 nm Nanodiamond

    PubMed Central

    Catledge, Shane A.; Singh, Sonal

    2011-01-01

    Discrete nanodiamond particles of 500 nm and 6 nm average size were seeded onto silicon substrates and plasma treated using chemical vapor deposition to create silicon-vacancy color centers. The resulting narrow-band room temperature photoluminescence is intense, and readily observed even for weakly agglomerated sub-10 nm size diamond. This is in contrast to the well-studied nitrogen-vacancy center in diamond which has luminescence properties that are strongly dependant on particle size, with low probability for incorporation of centers in sub-10 nm crystals. We suggest the silicon-vacancy center to be a viable alternative to nitrogen-vacancy defects for use as a biomarker in the clinically-relevant sub-10 nm size regime, for which nitrogen defect-related luminescent activity and stability is reportedly poor. PMID:21603120

  17. Trapping of diffusing particles by clusters of absorbing disks on a reflecting wall with disk centers on sites of a square lattice

    NASA Astrophysics Data System (ADS)

    Berezhkovskii, Alexander M.; Dagdug, Leonardo; Vazquez, Marco-Vinicio; Lizunov, Vladimir A.; Zimmerberg, Joshua; Bezrukov, Sergey M.

    2013-02-01

    A simple approximate formula is derived for the rate constant that describes steady-state flux of diffusing particles through a cluster of perfectly absorbing disks on the otherwise reflecting flat wall, assuming that the disk centers occupy neighboring sites of a square lattice. A distinctive feature of trapping by a disk cluster is that disks located at the cluster periphery shield the disks in the center of the cluster. This competition of the disks for diffusing particles makes it impossible to find an exact analytical solution for the rate constant in the general case. To derive the approximate formula, we use a recently suggested approach [A. M. Berezhkovskii, L. Dagdug, V. A. Lizunov, J. Zimmerberg, and S. M. Bezrukov, J. Chem. Phys. 136, 211102 (2012)], 10.1063/1.4726015, which is based on the replacement of the disk cluster by an effective uniform partially absorbing spot. The formula shows how the rate constant depends on the size and shape of the cluster. To check the accuracy of the formula, we compare its predictions with the values of the rate constant obtained from Brownian dynamics simulations. The comparison made for 18 clusters of various shapes and sizes shows good agreement between the theoretical predictions and numerical results.

  18. Ks- and Lp-band polarimetry on stellar and bow-shock sources in the Galactic center

    NASA Astrophysics Data System (ADS)

    Buchholz, R. M.; Witzel, G.; Schödel, R.; Eckart, A.

    2013-09-01

    Context. Infrared observations of the Galactic center (GC) provide a unique opportunity to study stellar and bow-shock polarization effects in a dusty environment. Aims: The goals of this work are to present new Ks- and Lp-band polarimetry on an unprecedented number of sources in the central parsec of the GC, thereby expanding our previous results in the H- and Ks-bands. Methods: We use AO-assisted Ks- and Lp-band observations, obtained at the ESO VLT. High precision photometry and the new polarimetric calibration method for NACO allow us to map the polarization in a region of 8'' × 25'' (Ks) resp. 26'' × 28'' (Lp). These are the first polarimetric observations of the GC in the Lp-band in 30 years, with vastly improved spatial resolution compared to previous results. This allows resolved polarimetry on bright bow-shock sources in this area for the first time at this wavelength. Results: We find foreground polarization to be largely parallel to the Galactic plane (Ks-band: 6.1% at 20°, Lp-band: 4.5% at 20°), in good agreement with our previous findings and with older results. The previously described Lp-band excess in the foregound polarization towards the GC could be confirmed here for a much larger number of sources. The bow-shock sources contained in the FOV seem to show a different relation between the polarization in the observed wavelength bands than what was determined for the foreground. This points to the different relevant polarization mechanisms. The resolved polarization patterns of IRS 5 and 10W match the findings we presented earlier for IRS 1W. Additionally, intrinsic Lp-band polarization was measured for IRS 1W and 21, as well as for other, less prominent mid-infrared-excess sources (IRS 2S, 2L, 5NE). The new data offer support for the presumed bow-shock nature of several of these sources (1W, 5, 5NE, 10W, 21) and for the model of bow-shock polarization presented in our last work. Tables 1 and 2 are available in electronic form at http

  19. Laparoscopic gastrointestinal anastomoses using knotless barbed absorbable sutures are safe and reproducible: a single-center experience with 242 patients

    PubMed Central

    Lee, Sang-Woong; Kawai, Masaru; Tashiro, Keitaro; Nomura, Eiji; Tokuhara, Takaya; Kawashima, Satoshi; Tanaka, Ryo; Uchiyama, Kazuhisa

    2016-01-01

    Objective Intracorporeal reconstruction of the digestive tract is technically challenging. The V-Loc 180 wound closure device (Covidien) is a self-anchoring unidirectional barbed suture that obviates the need for knot tying. The aim of this prospective cohort study was to investigate the use of the novel suture in gastrointestinal enterotomy closure. Methods The subjects comprised patients with malignant disease who were scheduled to undergo laparoscopic gastrectomy with curative intent. The barbed suture was used to close the entry hole for the linear stapler during intracorporeal reconstruction following laparoscopic gastric resection. The primary endpoint was the proportion of patients who developed anastomotic leakage at the site where the barbed suture was applied. Results Between July 2012 and March 2015, 242 patients were enrolled. Of 362 anastomoses, the enterotomy hole at 256 sites was closed using the barbed suture. These 256 sites consisted of 95 gastroduodenostomies, 25 gastrogastrostomies, 13 gastrojejunostomies, 90 jejunojejunostomies, 17 esophagojejunostomies and 16 primary closures of the stomach following local gastric resection. There were no anastomosis-related complications, conversion to usual sutures, mechanical closure of the entry hole and reoperation due to adhesive obstructions or mortality over a median follow-up period of 17.8 months. Conclusions The use of the unidirectional barbed absorbable suture for gastrointestinal closure is safe and effective in laparoscopic gastrectomy. PMID:26819279

  20. Exact solution for eigenfunction statistics at the center-of-band anomaly in the Anderson localization model

    NASA Astrophysics Data System (ADS)

    Kravtsov, V. E.; Yudson, V. I.

    2010-11-01

    An exact solution is found for the problem of the center-of-band (E=0) anomaly in the one-dimensional Anderson model of localization. By deriving and solving an equation for the generating function Φ(u,ϕ) we obtained an exact expression in quadratures for statistical moments Iq=⟨|ψE(r)|2q⟩ of normalized wave functions ψE(r) which show violation of one-parameter scaling and emergence of an additional length scale at E≈0 .

  1. Multispectral metamaterial absorber.

    PubMed

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

    2014-03-01

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

  2. Spin coherence and 14N ESEEM effects of nitrogen-vacancy centers in diamond with X-band pulsed ESR

    NASA Astrophysics Data System (ADS)

    Rose, B. C.; Weis, C. D.; Tyryshkin, A. M.; Schenkel, T.; Lyon, S. A.

    2017-02-01

    Pulsed ESR experiments are reported for ensembles of negatively-charged nitrogen-vacancy centers (NV$^-$) in diamonds at X-band magnetic fields (280-400 mT) and low temperatures (2-70 K). The NV$^-$ centers in synthetic type IIb diamonds (nitrogen impurity concentration $<1$~ppm) are prepared with bulk concentrations of $2\\cdot 10^{13}$ cm$^{-3}$ to $4\\cdot 10^{14}$ cm$^{-3}$ by high-energy electron irradiation and subsequent annealing. We find that a proper post-radiation anneal (1000$^\\circ$C for 60 mins) is critically important to repair the radiation damage and to recover long electron spin coherence times for NV$^-$s. After the annealing, spin coherence times of T$_2 = 0.74$~ms at 5~K are achieved, being only limited by $^{13}$C nuclear spectral diffusion in natural abundance diamonds. At X-band magnetic fields, strong electron spin echo envelope modulation (ESEEM) is observed originating from the central $^{14}$N nucleus. The ESEEM spectral analysis allows for accurate determination of the $^{14}$N nuclear hypefine and quadrupole tensors. In addition, the ESEEM effects from two proximal $^{13}$C sites (second-nearest neighbor and fourth-nearest neighbor) are resolved and the respective $^{13}$C hyperfine coupling constants are extracted.

  3. Time-resolved X-, K-, and W-band EPR of the radical pair state P{sub 700}{sup {center_dot}-}A{sub 1}{sup {center_dot}-} of photosystem I in comparison with P{sub 865}{sup {center_dot}+}Q{sub A}{sup {center_dot}-} in bacterial reaction centers

    SciTech Connect

    Est, A. van der; Prisner, T.; Moebius, K.; Stehlik, D.; Bittl, R.; Fromme, P.; Lubitz, W.

    1997-02-20

    The spin-polarized EPR spectra at 95 GHz (W-band), 24 GHz (K-band), and 9 GHz (X-band) of the radical pair P{sub 700}{sup {center_dot}+}A{sub 1}{sup {center_dot}-} in highly purified photosystem I particles are presented. The spectra are analyzed to obtain both the magnetic parameters of the radical pair as well as the relative orientation of the two species. From the analysis, the g-tensor of A{sub 1}{sup {center_dot}-} is found to be g{sub xx} = 2.0062, g{sub yy} = 2.0051, and g{sub zz} = 2.0022, and it is shown that A{sub 1} is oriented such that the carbonyl bonds are parallel to the vector joining the centers of P{sub 700}{sup {center_dot}+} and A{sub 1}{sup {center_dot}-}. The anisotropy of the g-tensor is considerably larger than that obtained for chemically reduced phylloquinone in frozen 2-propanol solution. Possible reasons for this difference and their implications for the A{sub 1} binding site are discussed. The relative orientation of P{sub 700}{sup {center_dot}+} and A{sub 1}{sup {center_dot}-} is compared with earlier estimates obtained using less accurate g-values for A{sub 1}{sup {center_dot}-}. A comparison with the spectra of P{sub 865}{sup {center_dot}+}Q{sub A}{sup {center_dot}-} in bacterial reaction centers (bRCs) of Rhodobacter sphaeroides R-26 in which the nonheme iron has been replaced by zinc (Zn-bRCs) allows the structural and magnetic properties of the charge-separated state in the two systems to be compared. 52 refs., 5 figs., 7 tabs.

  4. The role of deep acceptor centers in the oxidation of acceptor-doped wide-band-gap perovskites ABO3

    NASA Astrophysics Data System (ADS)

    Putilov, L. P.; Tsidilkovski, V. I.

    2017-03-01

    The impact of deep acceptor centers on defect thermodynamics and oxidation of wide-band-gap acceptor-doped perovskites without mixed-valence cations is studied. These deep centers are formed by the acceptor-bound small hole polarons whose stabilization energy can be high enough (significantly higher than the hole-acceptor Coulomb interaction energy). It is shown that the oxidation enthalpy ΔHox of oxide is determined by the energy εA of acceptor-bound states along with the formation energy EV of oxygen vacancies. The oxidation reaction is demonstrated to be either endothermic or exothermic, and the regions of εA and EV values corresponding to the positive or negative ΔHox are determined. The contribution of acceptor-bound holes to the defect thermodynamics strongly depends on the acceptor states depth εA: it becomes negligible at εA less than a certain value (at which the acceptor levels are still deep). With increasing εA, the concentration of acceptor-bound small hole polarons can reach the values comparable to the dopant content. The results are illustrated with the acceptor-doped BaZrO3 as an example. It is shown that the experimental data on the bulk hole conductivity of barium zirconate can be described both in the band transport model and in the model of hopping small polarons localized on oxygen ions away from the acceptor centers. Depending on the εA magnitude, the oxidation reaction can be either endothermic or exothermic for both mobility mechanisms.

  5. Structure of the reaction center of photosystem I of plants. An investigation with linear-dichroic absorbance-detected magnetic resonance

    SciTech Connect

    Vrieze, J.; Gast, P.; Hoff, A.J.

    1996-06-06

    Photosystem I particles from spinach were studied with linear-dichroic absorbance-detected magnetic resonance in zero-magnetic field. The microwave-induced triplet-minus-singlet (T-S) spectra and the linear-dichroic (LD) T-S spectra were recorded for the {bar D}+ {bar E} and the {bar D} - {bar E} microwave transitions of the triplet state of the primary donor, {sub 3}P{sub 700}. From these data the directions of the optical transition moments contributing to the T-S spectra in the 600-750 nm region, with respect to the triplet x- and y-axes of {sub 3}P{sub 700} were obtained. A comparison is made with data obtained for monomeric chlorophyll (Chl) a in two glasses. The orientation of the Q{sub Y}-transition moment with respect to the in-plane triplet x- and y-axes of {sub 3}P{sub 700} differs from monomeric Chl a in the two glasses. This difference is ascribed to the different environments of P{sub 700} and Chl a, rather than to the dimeric structure of P{sub 700}. In addition to the Q{sub Y}-absorption band of P{sub 700}, the T-S and LD(T-S) spectra contain features that are ascribed to transitions involving accessory Chls. The contribution of the Q{sub Y} transition of the primary acceptor to a band at 687 nm in the T-S spectrum is discussed, and a comparison is made with the signal of the primary acceptor in the T-S spectrum of Heliobacterium chlorum. 51 refs., 4 figs., 2 tabs.

  6. The Galactic Center EGRET Source and the Broad-band Spectrum of SGR A East

    NASA Astrophysics Data System (ADS)

    Fatuzzo, M.; Melia, F.; Yusef-Zadeh, F.; Markoff, S.

    1999-06-01

    High energy (30 MeV - 10 GeV) emission associated with a Galactic Center source has recently been observed by EGRET on board the Compton Gamma-ray Observatory. Continuum low-frequency radio observations of the Galactic Center reveal the presence of several viable source candidates, one of which is a prominent elliptical shell structure known as Sgr A East. Although morphologically similar to supernova remnants (SNRs), its inferred energetics and size appear to be extreme and have generated some uncertainty regarding this interpretation. Additionally, the radio spectral index determined from 6 cm and 20 cm observations of Sgr A East (~ 1) differs from the indices normally found for SNRs (~ 0.5). This difference is quite significant given that the corresponding index for the electron distribution for Sgr A East is then ~3 (versus ~2 for SNRs) and therefore unlike that thought to be produced directly from the shock acceleration processes believed to occur in such an environment. Regardless, recent observations of this region at 1720 MHz (the transition frequency of OH maser emission) have revealed the presence of several maser spots, suggesting a kinship between Sgr A East and three EGRET SNRs also observed at 1720 MHz: IC443, W28 and W44. This possible kinship suggests that Sgr A East could be the source of the EGRET emission. We show here that the pion-production and decay mechanism invoked to account for gamma-ray emission from SNRs can also naturally account for the radio through TeV spectrum of Sgr A East (including the EGRET data). The differences between the spectral features of Sgr A East and the other SNRs then results from the differences between the underlying energetics and the properties of the surrounding interstellar medium.

  7. Diode-pumped femtosecond oscillators using ultra-broad-band Yb-doped crystals and modelocked using low-temperature grown or ion implanted saturable-absorber mirrors

    NASA Astrophysics Data System (ADS)

    Druon, F.; Valentine, G. J.; Chénais, S.; Raybaut, P.; Balembois, F.; Georges, P.; Brun, A.; Kemp, A. J.; Birkin, D. J. L.; Sibbett, W.; Mohr, S.; Kopf, D.; Burns, D.; Courjaud, A.; Hönninger, C.; Salin, F.; Gaumé, R.; Aron, A.; Aka, G.; Viana, B.; Clerc, C.; Bernas, H.

    2002-12-01

    Femtosecond modelocked lasers using new ytterbium-doped borate crystals (Yb:Sr3Y(BO3)3, Yb:Ca4GdO(BO3)3 and Yb:Ca4YO(BO3)3) are demonstrated. Pulse duration as short as 69 fs has been obtained. To modelock such lasers, fast saturable absorbers need to be used. Two different types of fast saturable absorbers have been studied: low-temperature-grown semiconductor mirrors (SESAM) and high-energy-ion-implanted semiconductor Bragg reflectors (SBR). We demonstrated, for the first time to our knowledge, that ion-implanted SBR can be used to modelock oscillators using Yb-doped materials.

  8. Shock Absorbing System

    NASA Astrophysics Data System (ADS)

    1982-01-01

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

  9. Absorber for terahertz radiation management

    SciTech Connect

    Biallas, George Herman; Apeldoorn, Cornelis; Williams, Gwyn P.; Benson, Stephen V.; Shinn, Michelle D.; Heckman, John D.

    2015-12-08

    A method and apparatus for minimizing the degradation of power in a free electron laser (FEL) generating terahertz (THz) radiation. The method includes inserting an absorber ring in the FEL beam path for absorbing any irregular THz radiation and thus minimizes the degradation of downstream optics and the resulting degradation of the FEL output power. The absorber ring includes an upstream side, a downstream side, and a plurality of wedges spaced radially around the absorber ring. The wedges form a scallop-like feature on the innermost edges of the absorber ring that acts as an apodizer, stopping diffractive focusing of the THz radiation that is not intercepted by the absorber. Spacing between the scallop-like features and the shape of the features approximates the Bartlett apodization function. The absorber ring provides a smooth intensity distribution, rather than one that is peaked on-center, thereby eliminating minor distortion downstream of the absorber.

  10. Fine-Structure Measurements of Oxygen A Band Absorbance for Estimating the Thermodynamic Average Temperature of the Earth's Atmosphere: An Experiment in Physical and Environmental Chemistry

    ERIC Educational Resources Information Center

    Myrick, M. L.; Greer, A. E.; Nieuwland, A.; Priore, R. J.; Scaffidi, J.; Andreatta, Daniele; Colavita, Paula

    2006-01-01

    The experiment describe the measures of the A band transitions of atmospheric oxygen, a rich series of rotation-electronic absorption lines falling in the deep red portion of the optical spectrum and clearly visible owing to attenuation of solar radiation. It combines pure physical chemistry with analytical and environmental science and provides a…

  11. Parity splitting and E1/E2 branching in the alternating parity band of {sup 240}Pu from two-center octupole wave functions using supersymmetric quantum mechanics

    SciTech Connect

    Jolos, R. V.; Brentano, P. von

    2011-08-15

    An interpretation is suggested of the recently published experimental data on the alternating parity bands in {sup 240}Pu. The interpretation is based on the assumption that the main role in the description of the properties of the alternating parity bands plays the octupole mode which preserves the axial symmetry. The mathematical technique of the supersymmetric quantum mechanics is used for the realization of the model with the two-center octupole wave functions. A good description of the parity splitting and of the ratio of the dipole and quadrupole transitional moments is obtained for the first two bands.

  12. Shock Absorbing Helmets

    NASA Technical Reports Server (NTRS)

    1978-01-01

    This paper presents a description of helmets used by football players that offer three times the shock-absorbing capacity of earlier types. An interior padding for the helmets, composed of Temper Foam, first used by NASA's Ames Research Center in the design of aircraft seats is described.

  13. Complexities in pyroxene compositions derived from absorption band centers: Examples from Apollo samples, HED meteorites, synthetic pure pyroxenes, and remote sensing data

    NASA Astrophysics Data System (ADS)

    Moriarty, D. P.; Pieters, C. M.

    2016-02-01

    We reexamine the relationship between pyroxene composition and near-infrared absorption bands, integrating measurements of diverse natural and synthetic samples. We test an algorithm (PLC) involving a two-part linear continuum removal and parabolic fits to the 1 and 2 μm bands—a computationally simple approach which can easily be automated and applied to remote sensing data. Employing a suite of synthetic pure pyroxenes, the PLC technique is shown to derive similar band centers to the modified Gaussian model. PLC analyses are extended to natural pyroxene-bearing materials, including (1) bulk lunar basalts and pyroxene separates, (2) diverse lunar soils, and (3) HED meteorites. For natural pyroxenes, the relationship between composition and absorption band center differs from that of synthetic pyroxenes. These differences arise from complexities inherent in natural materials such as exsolution, zoning, mixing, and space weathering. For these reasons, band center measurements of natural pyroxene-bearing materials are compositionally nonunique and could represent three distinct scenarios (1) pyroxene with a narrow compositional range, (2) complexly zoned pyroxene grains, or (3) a mixture of multiple pyroxene (or nonpyroxene) components. Therefore, a universal quantitative relationship between band centers and pyroxene composition cannot be uniquely derived for natural pyroxene-bearing materials without additional geologic context. Nevertheless, useful relative relationships between composition and band center persist in most cases. These relationships are used to interpret M3 data from the Humboldtianum Basin. Four distinct compositional units are identified (1) Mare Humboldtianum basalts, (2) distinct outer basalts, (3) low-Ca pyroxene-bearing materials, and (4) feldspathic materials.

  14. Substitution of Li for Cu in Cu2ZnSnS4: Toward Wide Band Gap Absorbers with Low Cation Disorder for Thin Film Solar Cells.

    PubMed

    Lafond, A; Guillot-Deudon, C; Vidal, J; Paris, M; La, C; Jobic, S

    2017-03-06

    The substitution of lithium for copper in Cu2ZnSnS4 (CZTS) has been experimentally and theoretically investigated. Formally, the (Cu1-xLix)ZnSnS4 system exhibits two well-defined solid solutions. Indeed, single crystal structural analyses demonstrate that the low (x < 0.4) and high (x > 0.6) lithium-content compounds adopt the kesterite structure and the wurtz-kesterite structure, respectively. For x between 0.4 and 0.6, the two aforementioned structure types coexist. Moreover, (119)Sn NMR analyses carried out on a (Cu0.7Li0.3)2ZnSnS4 sample clearly indicate that lithium replaces copper preferentially on two of the three available 2-fold crystallographic sites commonly occupied by Cu and Zn in disordered kesterite. Furthermore, the observed individual lines in the NMR spectrum suggest that the propensity of Cu and Zn atoms to be randomly distributed over the 2c and 2d crystallographic sites is lowered when lithium is partially substituted for copper. Additionally, the first-principles calculations provide insights into the arrangement of Li atoms as a function of the Cu/Zn disorder and its effect on the structural (lattice parameters) and optical properties of CZTS (band gap evolution). Those calculations agree with the experimental observations and account for the evolutions of the unit cell parameters as well as for the increase of band gap when the Li-content increases. The calculation of the formation enthalpy of point defect unambiguously indicates that Li modifies the Cu/Zn disorder in a manner similar to the change of Cu/Zn disorder induced by Ag alloying. Overall, it was found that Li alloying is a versatile way of tuning the optoelectronic properties of CZTS making it a good candidate as wide band gap materials for the top cells of tandem solar cells.

  15. Catalytic Activity-d-Band Center Correlation for the O2 Reduction on Platinum in Alkaline Solutions

    SciTech Connect

    Lima,F.; Zhang, J.; Shao, M.; Sasaki, K.; Vukmirovic, M.; Ticianelli, E.; Adzic, R.

    2007-01-01

    We determined, by the rotating disk electrode technique, the kinetics of the oxygen-reduction reaction (ORR) on the surfaces of single crystals of Au(111), Ag(111), Pd(111), Rh(111), Ir(111), and Ru(0001), on Pt monolayers deposited on their surfaces, and also on nanoparticles of these metals dispersed on high-surface-area carbon. Plotting the correlation between the experimentally determined activities of these three types of electrocatalysts with the calculated metal d-band center energies,{var_epsilon}{sub d}, revealed a volcano-type dependence. In all cases, the electronic properties of the metal electrocatalysts, represented by the {var_epsilon}{sub d} value, were used for elucidating the metal-dependent catalytic activities, and establishing their electronic properties-the ORR kinetics relationship. Pt(111), Pt/C, and Pt/Pd(111) were found to top their corresponding volcano plots. Pd in alkaline solutions showed particularly high activity, suggesting it may offer potential replacement for Pt in fuel cells.

  16. Effect of band-aligned double absorber layers on photovoltaic characteristics of chemical bath deposited PbS/CdS thin film solar cells.

    PubMed

    Ho Yeon, Deuk; Chandra Mohanty, Bhaskar; Lee, Seung Min; Soo Cho, Yong

    2015-09-23

    Here we report the highest energy conversion efficiency and good stability of PbS thin film-based depleted heterojunction solar cells, not involving PbS quantum dots. The PbS thin films were grown by the low cost chemical bath deposition (CBD) process at relatively low temperatures. Compared to the quantum dot solar cells which require critical and multistep complex procedures for surface passivation, the present approach, leveraging the facile modulation of the optoelectronic properties of the PbS films by the CBD process, offers a simpler route for optimization of PbS-based solar cells. Through an architectural modification, wherein two band-aligned junctions are stacked without any intervening layers, an enhancement of conversion efficiency by as much as 30% from 3.10 to 4.03% facilitated by absorption of a wider range of solar spectrum has been obtained. As an added advantage of the low band gap PbS stacked over a wide gap PbS, the devices show stability over a period of 10 days.

  17. Effect of band-aligned double absorber layers on photovoltaic characteristics of chemical bath deposited PbS/CdS thin film solar cells

    PubMed Central

    Ho Yeon, Deuk; Chandra Mohanty, Bhaskar; Lee, Seung Min; Soo Cho, Yong

    2015-01-01

    Here we report the highest energy conversion efficiency and good stability of PbS thin film-based depleted heterojunction solar cells, not involving PbS quantum dots. The PbS thin films were grown by the low cost chemical bath deposition (CBD) process at relatively low temperatures. Compared to the quantum dot solar cells which require critical and multistep complex procedures for surface passivation, the present approach, leveraging the facile modulation of the optoelectronic properties of the PbS films by the CBD process, offers a simpler route for optimization of PbS-based solar cells. Through an architectural modification, wherein two band-aligned junctions are stacked without any intervening layers, an enhancement of conversion efficiency by as much as 30% from 3.10 to 4.03% facilitated by absorption of a wider range of solar spectrum has been obtained. As an added advantage of the low band gap PbS stacked over a wide gap PbS, the devices show stability over a period of 10 days. PMID:26394761

  18. Effect of band-aligned double absorber layers on photovoltaic characteristics of chemical bath deposited PbS/CdS thin film solar cells

    NASA Astrophysics Data System (ADS)

    Ho Yeon, Deuk; Chandra Mohanty, Bhaskar; Lee, Seung Min; Soo Cho, Yong

    2015-09-01

    Here we report the highest energy conversion efficiency and good stability of PbS thin film-based depleted heterojunction solar cells, not involving PbS quantum dots. The PbS thin films were grown by the low cost chemical bath deposition (CBD) process at relatively low temperatures. Compared to the quantum dot solar cells which require critical and multistep complex procedures for surface passivation, the present approach, leveraging the facile modulation of the optoelectronic properties of the PbS films by the CBD process, offers a simpler route for optimization of PbS-based solar cells. Through an architectural modification, wherein two band-aligned junctions are stacked without any intervening layers, an enhancement of conversion efficiency by as much as 30% from 3.10 to 4.03% facilitated by absorption of a wider range of solar spectrum has been obtained. As an added advantage of the low band gap PbS stacked over a wide gap PbS, the devices show stability over a period of 10 days.

  19. 56  Gb/s multi-band CAP for data center interconnects up to an 80  km SMF.

    PubMed

    Wei, Jinlong; Eiselt, Nicklas; Sanchez, Christian; Du, Ruoyang; Griesser, Helmut

    2016-09-01

    We present the first (to the best of our knowledge) experimental demonstration of a 56 Gb/s multi-band carrierless amplitude and phase modulation (CAP) signal transmission over an 80-km single-mode fiber link with zero overhead pre-FEC signal recovery and enhanced timing jitter tolerance for optical data center interconnects.

  20. ACTS propagation experiment discussion: Ka-band propagation measurements using the ACTS propagation terminal and the CSU-CHILL and Space Communications Technology Center Florida propagation program

    NASA Technical Reports Server (NTRS)

    Bringi, V. N.; Chandrasekar, V.; Mueller, Eugene A.; Turk, Joseph; Beaver, John; Helmken, Henry F.; Henning, Rudy

    1993-01-01

    Papers on Ka-band propagation measurements using the ACTS propagation terminal and the Colorado State University CHILL multiparameter radar and on Space Communications Technology Center Florida Propagation Program are discussed. Topics covered include: microwave radiative transfer and propagation models; NASA propagation terminal status; ACTS channel characteristics; FAU receive only terminal; FAU terminal status; and propagation testbed.

  1. Trapped H2O in SiO condensate - An explanation for the 3 micron band observed toward the Galactic center

    NASA Technical Reports Server (NTRS)

    Wada, S.; Sakata, A.; Tokunaga, A. T.

    1991-01-01

    An SiO condensate containing trapped and adsorbed H2O was produced in the laboratory. The SiO condensate is not a silicate; it is an amorphous silicon suboxide material. The micron absorption of trapped H2O in this condensate matches very closely the 3 micron absorption band of the Galactic center source IRS 7.

  2. Sound Absorbers

    NASA Astrophysics Data System (ADS)

    Fuchs, H. V.; Möser, M.

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

  3. Optical absorbance and band-gap engineering of (BN) 1 -x(C2)x two-dimensional alloys: Phase separation and composition fluctuation effects

    NASA Astrophysics Data System (ADS)

    Guilhon, I.; Marques, M.; Teles, L. K.; Bechstedt, F.

    2017-01-01

    The (BN) 1 -x(C2)x alloys are promising materials for band-gap engineering in two-dimensional electronics. In this work, we provide a complete scenario of statistical possibilities for the distribution of atoms and its influence on electronic and optical properties. Using first-principles calculations combined with the generalized quasichemical approximation to account for disorder effects, we study the properties of these two-dimensional alloys as a function of their average composition. Our results show that atomic arrangements with C-C and B-N bonds are energetically favored over the ones with B-B and N-N bonds, explaining the known tendency to phase separation, verified by a T -x phase diagram. We calculate the energy gap as a function of the composition considering both composition fluctuation and phase separation effects. Experimental data are discussed in this context. Finally, we obtain absorption spectra reproducing a two-peak pattern for intermediate carbon concentrations found experimentally and identified with phase-segregated instead of homogeneous alloys.

  4. THz-metamaterial absorbers

    NASA Astrophysics Data System (ADS)

    Tuong Pham, Van; Park, J. W.; Vu, Dinh Lam; Zheng, H. Y.; Rhee, J. Y.; Kim, K. W.; Lee, Y. P.

    2013-03-01

    An ultrabroad-band metamaterial absorber was investigated in mid-IR regime based on a similar model in previous work. The high absorption of metamaterial was obtained in a band of 8-11.7 THz with energy loss distributed in SiO2, which is appropriate potentially for solar-cell applications. A perfect absorption peak was provided by using a sandwich structure with periodical anti-dot pattern in the IR region, getting closed to visible-band metamaterials. The dimensional parameters were examined for the corresponding fabrication. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology, 30 October-2 November, 2012, Ha Long, Vietnam.

  5. Threshold Shifts and Cochlear Injury in Chinchillas Exposed to Octave Bands of Noise Centered at 63 and 1000 HZ for 9 Days,

    DTIC Science & Technology

    1982-10-01

    2.0 kHz. The 1000-Hz octave bands produced more permanent threshold shift at the lower 33 %.. . %. , Ic CV) 1 00 EuG LLS) 2C C LJ5- 0o x ezw CA OJ...Officer Commander Naval Medical R&D Command US Army Transportation School National Naval Medical Center ATTN: ATSPoTD-ST Bethesda, 1D 20014 (1) Fort

  6. Erbium concentration dependent absorbance in tellurite glass

    SciTech Connect

    Sazali, E. S. Rohani, M. S. Sahar, M. R. Arifin, R. Ghoshal, S. K. Hamzah, K.

    2014-09-25

    Enhancing the optical absorption cross-section in topically important rare earth doped tellurite glasses is challenging for photonic devices. Controlled synthesis and detailed characterizations of the optical properties of these glasses are important for the optimization. The influence of varying concentration of Er{sup 3+} ions on the absorbance characteristics of lead tellurite glasses synthesized via melt-quenching technique are investigated. The UV-Vis absorption spectra exhibits six prominent peaks centered at 490, 526, 652, 800, 982 and 1520 nm ascribed to the transitions in erbium ion from the ground state to the excited states {sup 4}F{sub 7/2}, {sup 2}H{sub 11/2}, {sup 4}F{sub 9/2}, {sup 4}I{sub 9/2}, {sup 2}H{sub 11/2} and {sup 4}I{sub 13/2}, respectively. The results are analyzed by means of optical band gap E{sub g} and Urbach energy E{sub u}. The values of the energy band gap are found decreased from 2.82 to 2.51 eV and the Urbach energy increased from 0.15 to 0.24 eV with the increase of the Er{sub 2}O{sub 3} concentration from 0 to 1.5 mol%. The excellent absorbance of the prepared tellurite glasses makes them suitable for fabricating solid state lasers.

  7. Dual broadband metamaterial absorber.

    PubMed

    Kim, Young Ju; Yoo, Young Joon; Kim, Ki Won; Rhee, Joo Yull; Kim, Yong Hwan; Lee, YoungPak

    2015-02-23

    We propose polarization-independent and dual-broadband metamaterial absorbers at microwave frequencies. This is a periodic meta-atom array consisting of metal-dielectric-multilayer truncated cones. We demonstrate not only one broadband absorption from the fundamental magnetic resonances but additional broadband absorption in high-frequency range using the third-harmonic resonance, by both simulation and experiment. In simulation, the absorption was over 90% in 3.93-6.05 GHz, and 11.64-14.55 GHz. The corresponding experimental absorption bands over 90% were 3.88-6.08 GHz, 9.95-10.46 GHz and 11.86-13.84 GHz, respectively. The origin of absorption bands was elucidated. Furthermore, it is independent of polarization angle owing to the multilayered circular structures. The design is scalable to smaller size for the infrared and the visible ranges.

  8. Absorbent Material

    NASA Technical Reports Server (NTRS)

    1985-01-01

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

  9. Frequency down-conversion of 637 nm light to the telecommunication band for non-classical light emitted from NV centers in diamond.

    PubMed

    Ikuta, Rikizo; Kobayashi, Toshiki; Yasui, Shuto; Miki, Shigehito; Yamashita, Taro; Terai, Hirotaka; Fujiwara, Mikio; Yamamoto, Takashi; Koashi, Masato; Sasaki, Masahide; Wang, Zhen; Imoto, Nobuyuki

    2014-05-05

    We demonstrate a low-noise frequency down-conversion of photons at 637 nm to the telecommunication band at 1587 nm by the difference frequency generation in a periodically-poled lithium niobate. An internal conversion efficiency of the converter is estimated to be 0.44 at the maximum which is achieved by a pump power of 0.43 W, whereas a rate of internal background photons caused by the strong cw pump laser is estimated to be 9 kHz/mW within a bandwidth of about 1 nm. By using the experimental values related to the intrinsic property of the converter, and using the intensity correlation and the average photon number of a 637 nm input light pulse, we derive the intensity correlation of a converted telecom light pulse. Then we discuss feasibility of a single-photon frequency conversion to the telecommunication band for a long-distance quantum communication based on NV centers in diamond.

  10. Dust in the Milky Way absorbs and scatters starlight

    NASA Technical Reports Server (NTRS)

    2002-01-01

    1.25, 2.2, and 3.5 Aum Solar elongation angle = 90 degree Maps. Galactic coordinate Mollweide projection maps of the entire sky as seen by the DIRBE at a fixed angle relative to the Sun. Stars concentrated in the Galactic plane (horizontal feature) dominate the images at these wavelengths. Dust in the Milky Way absorbs and scatters starlight, producing the dark band that runs through the Galactic center in the 1.25 Aum image; this 'extinction' effect diminishes with increasing wavelength.

  11. Development and Evaluation of a Combined Cultivator and Band Sprayer with a Row-Centering RTK-GPS Guidance System

    PubMed Central

    Perez-Ruiz, Manuel; Carballido, Jacob; Agüera, Juan; Rodríguez-Lizana, Antonio

    2013-01-01

    Typically, low-pressure sprayers are used to uniformly apply pre- and post-emergent herbicides to control weeds in crop rows. An innovative machine for weed control in inter-row and intra-row areas, with a unique combination of inter-row cultivation tooling and intra-row band spraying for six rows and an electro-hydraulic side-shift frame controlled by a GPS system, was developed and evaluated. Two weed management strategies were tested in the field trials: broadcast spraying (the conventional method) and band spraying with mechanical weed control using RTK-GPS (the experimental method). This approach enabled the comparison between treatments from the perspective of cost savings and efficacy in weed control for a sugar beet crop. During the 2010–2011 season, the herbicide application rate (112 L ha−1) of the experimental method was approximately 50% of the conventional method, and thus a significant reduction in the operating costs of weed management was achieved. A comparison of the 0.2-trimmed means of weed population post-treatment showed that the treatments achieved similar weed control rates at each weed survey date. Sugar beet yields were similar with both methods (p = 0.92). The use of the experimental equipment is cost-effective on ≥20 ha of crops. These initial results show good potential for reducing herbicide application in the Spanish beet industry. PMID:23478600

  12. Development and evaluation of a combined cultivator and band sprayer with a row-centering RTK-GPS guidance system.

    PubMed

    Perez-Ruiz, Manuel; Carballido, Jacob; Agüera, Juan; Rodríguez-Lizana, Antonio

    2013-03-11

    Typically, low-pressure sprayers are used to uniformly apply pre- and post-emergent herbicides to control weeds in crop rows. An innovative machine for weed control in inter-row and intra-row areas, with a unique combination of inter-row cultivation tooling and intra-row band spraying for six rows and an electro-hydraulic side-shift frame controlled by a GPS system, was developed and evaluated. Two weed management strategies were tested in the field trials: broadcast spraying (the conventional method) and band spraying with mechanical weed control using RTK-GPS (the experimental method). This approach enabled the comparison between treatments from the perspective of cost savings and efficacy in weed control for a sugar beet crop. During the 2010-2011 season, the herbicide application rate (112 L ha(-1)) of the experimental method was approximately 50% of the conventional method, and thus a significant reduction in the operating costs of weed management was achieved. A comparison of the 0.2-trimmed means of weed population post-treatment showed that the treatments achieved similar weed control rates at each weed survey date. Sugar beet yields were similar with both methods (p = 0.92). The use of the experimental equipment is cost-effective on ≥20 ha of crops. These initial results show good potential for reducing herbicide application in the Spanish beet industry.

  13. Facilitated diffusion of iron(II) and dioxygen substrates into human H-chain ferritin. A fluorescence and absorbance study employing the ferroxidase center substitution Y34W.

    PubMed

    Bou-Abdallah, Fadi; Zhao, Guanghua; Biasiotto, Giorgio; Poli, Maura; Arosio, Paolo; Chasteen, N Dennis

    2008-12-31

    Ferritin is a widespread iron mineralizing and detoxification protein that stores iron as a hydrous ferric oxide mineral core within a shell-like structure of 4/3/2 octahedral symmetry. Iron mineralization is initiated at dinuclear ferroxidase centers inside the protein where Fe(2+) and O(2) meet and react to form a mu-1,2-peroxodiferric intermediate that subsequently decays to form mu-oxo dimeric and oligomeric iron(III) species and ultimately the mineral core. Several types of channels penetrate the protein shell and are possible pathways for the diffusion of iron and dioxygen to the ferroxidase centers. In the present study, UV/visible and fluorescence stopped-flow spectrophotometries were used to determine the kinetics and pathways of Fe(2+) diffusion into the protein shell, its binding at the ferroxidase center and its subsequent oxidation by O(2). Three fluorescence variants of human H-chain ferritin were prepared in which Trp34 was introduced near the ferroxidase center. They included a control variant no. 1 (W93F/Y34W), a "1-fold" channel variant no. 2 (W93F/Y34W/Y29Q) and a 3-fold channel variant no. 3 (Y34W/W93F/D131I/E134F). Anaerobic rapid mixing of Fe(2+) with apo-variant no. 1 quenched the fluorescence of Trp34 with a rate exhibiting saturation kinetics with respect to Fe(2+) concentration, consistent with a process involving facilitated diffusion. A half-life of approximately 3 ms for this process is attributed to the time for diffusion of Fe(2+) across the protein shell to the ferroxidase center. No fluorescence quenching was observed with the 3-fold channel variant no. 3 or when Zn(2+) was prebound in each of the eight 3-fold channels of variant no. 1, observations indicating that the hydrophilic channels are the only avenues for rapid Fe(2+) access to the ferroxidase center. Substitution of Tyr29 with glutamine at the entrance of the "1-fold" hydrophobic channel had no effect on the rate of Fe(2+) oxidation to form the mu-1,2-peroxodiferric

  14. The effects of a community-centered muscle strengthening exercise program using an elastic band on the physical abilities and quality of life of the rural elderly

    PubMed Central

    Park, So-Yeon; Kim, Jin-Kyung; Lee, Seong-A

    2015-01-01

    [Purpose] The purpose of this study was to examine the effects of a muscle strengthening exercise program using an elastic band on changes in the physical abilities and quality of life of the rural elderly. [Subjects] The subjects of this study were 46 elderly people (8 males, 38 females) aged 65 or older, who lived in a rural area and managed their daily lives independently. [Methods] The study’s exercise program was conducted 16 times for 80 minutes each session over an eight-week period. This program consisted of several exercises to strengthen muscular endurance and improve balance ability based on exercises using Thera-bands. The physical abilities of the subjects were divided into muscular endurance, upper-extremity flexibility, balance, and low-extremity agility. Each ability was measured to compare the effects of the exercise program. In addition, the Korean version of the World Health Organization Quality of Life (WHOQOL)-BREF questionnaire was used to examine changes in the subjects’ quality of life. [Results] The subjects showed improvements in muscular endurance, balance, and low-extremity agility. They also exhibited an overall statistically significant improvement in quality of life scores after the exercise program. In terms of the main items, changes were observed in the areas of psychological relations, social relations, and environment. [Conclusion] The community-centered muscle strengthening exercise program using the elastic band was found to improve muscular endurance, balance, agility, and quality of life of rural elderly subjects. PMID:26311926

  15. A peek behind the dusty curtain: KS-band polarization photometry and bow shock models of the Galactic center source IRS 8

    NASA Astrophysics Data System (ADS)

    Rauch, C.; Mužić, K.; Eckart, A.; Buchholz, R. M.; García-Marín, M.; Sabha, N.; Straubmeier, C.; Valencia-S., M.; Yazici, S.

    2013-03-01

    Context. IRS 8 offers the possibility to study unique bow shock properties and polarization features in the dusty environment at the Galactic center. Aims: We aim to gain insight into the properties of the surrounding material of the bow shock source IRS 8, based on the measured polarization distribution along its extended feature. Bow shock models enable a relative positioning of its central star with respect to the northern arm and Sagittarius A*. Methods: The analysis is based on polarimetric KS-band and nonpolarimetric L'- and N-band data obtained with the adaptive-optics assisted instrument NAOS/CONICA (KS- and L'-band) and the mid-infrared imager/spectrograph VISIR (N-band) at the ESO Very Large Telescope. A polarization map covering an area of ~31.9'' × 8.2'' at the position of IRS 8 was obtained using high-precision photometric methods, together with a polarimetric calibration specified for NACO. In addition, simulated L'-band bow shock models are presented, which allow a positioning of IRS 8 with respect to the interaction medium of the northern arm. Results: This work presents interstellar dust properties for the northern arm in the vicinity of a bow shock, as well as a three-dimensional positioning of IRS 8 with respect to the northern arm and Sagittarius A*. The presented polarization maps for the Galactic center source IRS 8 show a total intrinsic polarization degree of 3.3% at 13° east of north, measured on nondeconvolved images, and 4.3% at 19° on Lucy-Richardson deconvolved images. Analysis of the polarization distribution along the bow shock reveals a polarization pattern as it would be produced by absorption on aligned grains and shows a decreasing polarization degree towards the apex of the bow shock. Current literature provides a mean electron density for IRS 8. The comparison of this value with properties of simulated polarization maps in a circumstellar environment, which are capable of multiple scattering, leads to the conclusion that

  16. Estimating Temperature Retrieval Accuracy Associated With Thermal Band Spatial Resolution Requirements for Center Pivot Irrigation Monitoring and Management

    NASA Technical Reports Server (NTRS)

    Ryan, Robert E.; Irons, James; Spruce, Joseph P.; Underwood, Lauren W.; Pagnutti, Mary

    2006-01-01

    This study explores the use of synthetic thermal center pivot irrigation scenes to estimate temperature retrieval accuracy for thermal remote sensed data, such as data acquired from current and proposed Landsat-like thermal systems. Center pivot irrigation is a common practice in the western United States and in other parts of the world where water resources are scarce. Wide-area ET (evapotranspiration) estimates and reliable water management decisions depend on accurate temperature information retrieval from remotely sensed data. Spatial resolution, sensor noise, and the temperature step between a field and its surrounding area impose limits on the ability to retrieve temperature information. Spatial resolution is an interrelationship between GSD (ground sample distance) and a measure of image sharpness, such as edge response or edge slope. Edge response and edge slope are intuitive, and direct measures of spatial resolution are easier to visualize and estimate than the more common Modulation Transfer Function or Point Spread Function. For these reasons, recent data specifications, such as those for the LDCM (Landsat Data Continuity Mission), have used GSD and edge response to specify spatial resolution. For this study, we have defined a 400-800 m diameter center pivot irrigation area with a large 25 K temperature step associated with a 300 K well-watered field surrounded by an infinite 325 K dry area. In this context, we defined the benchmark problem as an easily modeled, highly common stressing case. By parametrically varying GSD (30-240 m) and edge slope, we determined the number of pixels and field area fraction that meet a given temperature accuracy estimate for 400-m, 600-m, and 800-m diameter field sizes. Results of this project will help assess the utility of proposed specifications for the LDCM and other future thermal remote sensing missions and for water resource management.

  17. Acne phototherapy using UV-free high-intensity narrow-band blue light: a three-center clinical study

    NASA Astrophysics Data System (ADS)

    Shalita, Alan R.; Harth, Yoram; Elman, Monica; Slatkine, Michael; Talpalariu, Gerry; Rosenberg, Yitzhak; Korman, Avner; Klein, Arieh

    2001-05-01

    Propionibacterium. acnes is a Gram positive, microaerophilic bacterium which takes a part in the pathogenesis of inflammatory acne. P. acnes is capable to produce high amounts endogenic porphyrins with no need of any trigger molecules. Light in the violet-blue range (407-420 nm) has been shown to exhibit a phototoxic effect on Propionibacterium acnes when irradiated in vitro. The purpose of our study was to test the clinical effects of a high intensity narrowband blue light source on papulo pustular acne. A total of 35 patients in 3 centers were treated twice a week with a high intensity metal halide lamp illuminating the entire face (20x20 cm2) or the back with visible light in the 407-420 nm range at an intensity of 90 mW/cm2 (CureLight Ltd.) for a total of 4 weeks. UV is totally cut off. In each treatment the patient was exposed to light for 8-15 minutes. After 8 treatments, 80% of the patients with mild to moderate papulo-pustular acne showed significant improvement at reducing the numbers of non- inflammatory, inflammatory and total facial lesions. Inflammatory lesion count decrease by a mean of 68%. No side effects to the treatment were noticed. In conclusion, full face or back illumination with the high intensity pure blue light we used exhibits a rapid significant decrease in acne lesions counts in 8 biweekly treatments.

  18. 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.

  19. Highlights from the Center for Adaptive Optics Treasury Survey of Distant Galaxies, Including H-band Photometry of a z=1.3 Supernova

    NASA Astrophysics Data System (ADS)

    Melbourne, J.; Barczys, M.; Wright, S. A.; Max, C. E.; Larkin, J.; Koo, D. C.; Perlmutter, S.; Steinbring, E.; Metevier, A.; Chun, M.

    2005-12-01

    The Center for Adaptive Optics Treasury Survey (CATS) is observing the deep HST galaxy fields (e.g., GOODS-N and S, COSMOS, GEMS, and EGS) with high-resolution near-infrared imaging from ground-based adaptive optics on large telescopes. Initial results from the first ten Keck laser guide star pointings are presented. Highlights include, 1) H-band (rest-frame R) photometry over maximum of a z=1.32 Type Ia supernova from the HST cluster supernova search of Perlmutter et al. (see poster of Dawson et al.); 2) a near-infrared study of small bulges of distant disk galaxies (z ˜0.6); 3) Stellar population synthesis models of AGN cores to z=1; and 4) Detection of lensed arcs around a z=0.20 cluster. CATS plans its first public data release in Fall 2006. This work is funded by the NSF Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under the cooperative agreement No. AST-9876783.

  20. Radiation accumulation of F{sub 2} color centers in LiF crystal

    SciTech Connect

    Lisitsyna, L. A.

    2016-01-15

    The paper presents the results of the research of the F{sub 2} centers accumulation dose dependences in the LiF crystals, the kinetics of absorption relaxation initiated by exposure to a single electron pulse in the band maxima of different electron centers obtained by time-resolved spectrometry with nanosecond resolution. An analytical description of the F{sub 2} center accumulation in an absorbed dose range ≤10{sup 3} Gy is provided.

  1. Investigation of Cu(In,Ga)Se2 Solar Cell Performance Deviations in Nominally Equal Absorbers

    NASA Astrophysics Data System (ADS)

    Knecht, Robin; Parisi, Jürgen; Riedel, Ingo; Schäffler, Raymund; Dimmler, Bernhard

    2012-10-01

    Cu(In,Ga)Se2 (CIGSe) solar cells were fabricated independently by industrial scale co-evaporation in two separate production lines with the same nominal composition and thickness of the absorber film. Although the device properties were believed to be the same we observed substantial deviations of the respective values of the open circuit voltage (ΔVOC = 40 mV) and of the fill factor (ΔFF= 4%), whereas the short circuit current was essentially the same. We performed fundamental device analysis, space charge and defect spectroscopy, transient photoluminescence as well as in-depth profiling of the chemical gradients of the absorber films. Using the results from the experiments we set up a simulation baseline which allowed us to conclude that the apparent deviations can be related to the presence of deep recombination centers with different concentration within the CIGSe absorber as well as to variations of the band gap grading.

  2. Carbon Absorber Retrofit Equipment (CARE)

    SciTech Connect

    Klein, Eric

    2015-12-23

    During Project DE-FE0007528, CARE (Carbon Absorber Retrofit Equipment), Neumann Systems Group (NSG) designed, installed and tested a 0.5MW NeuStream® carbon dioxide (CO2) capture system using the patented NeuStream® absorber equipment and concentrated (6 molal) piperazine (PZ) as the solvent at Colorado Springs Utilities’ (CSU’s) Martin Drake pulverized coal (PC) power plant. The 36 month project included design, build and test phases. The 0.5MW NeuStream® CO2 capture system was successfully tested on flue gas from both coal and natural gas combustion sources and was shown to meet project objectives. Ninety percent CO2 removal was achieved with greater than 95% CO2product purity. The absorbers tested support a 90% reduction in absorber volume compared to packed towers and with an absorber parasitic power of less than 1% when configured for operation with a 550MW coal plant. The preliminary techno-economic analysis (TEA) performed by the Energy and Environmental Research Center (EERC) predicted an over-the-fence cost of $25.73/tonne of CO2 captured from a sub-critical PC plant.

  3. Single-Band and Dual-Band Infrared Detectors

    NASA Technical Reports Server (NTRS)

    Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor); Soibel, Alexander (Inventor); Nguyen, Jean (Inventor); Khoshakhlagh, Arezou (Inventor)

    2015-01-01

    Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.

  4. 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.

  5. 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.

  6. Electronic properties of perovskite absorbers for solar cell applications

    NASA Astrophysics Data System (ADS)

    Filip, Marina; Giustino, Feliciano

    2015-03-01

    Metal halide perovskite absorbers have captured the attention of the photovoltaics research community in the past 3 years, reaching efficiencies over 19%. Despite this unprecedented progress, the remarkable physical properties of these materials are not yet fully understood. In this work we show an exhaustive computational study of CH3NH3PbI3 within density functional theory and the GW approximation. We show the effect of semicore states and spin-orbit coupling on the quasiparticle band gap of CH3NH3PbI3 and describe a straightforward ``self-consistent scissor'' method to correct the underestimated dielectric screening in the G0W0 approach. Finally, we model the interplay between the structural and electronic properties of lead-iodide perovskites and propose novel lead-iodide peroskite absorbers with different cations at the center of the cuboctahedral cavity facilitating the tunning of the fundamental band gap. This work was supported by the ERC (EU FP7 / ERC 239578), UK EPSRC (EP/J009857/1) and the Leverhulme Trust (RL-2012-001).

  7. 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.

  8. Shock absorber control system

    SciTech Connect

    Nakano, Y.; Ohira, M.; Ushida, M.; Miyagawa, T.; Shimodaira, T.

    1987-01-13

    A shock absorber control system is described for controlling a dampening force of a shock absorber of a vehicle comprising: setting means for setting a desired dampening force changeable within a predetermined range; drive means for driving the shock absorber to change the dampening force of the shock absorber linearly; control means for controlling the drive means in accordance with the desired dampening force when the setting of the desired dampening force has been changed; detecting means for detecting an actual dampening force of the shock absorber; and correcting means for correcting the dampening force of the shock absorber by controlling the drive means in accordance with a difference between the desired dampening force and the detected actual dampening force.

  9. CPCs with segmented absorbers

    SciTech Connect

    Keita, M.; Robertson, H.S. )

    1991-01-01

    One of the most promising means of improving the performance of solar thermal collectors is to reduce the energy lost by the hot absorber. One way to do this, not currently part of the technology, is to recognize that since the absorber is usually not irradiated uniformly, it is therefore possible to construct an absorber of thermally isolated segments, circulate the fluid in sequence from low to high irradiance segments, and reduce loss by improving effective concentration. This procedure works even for ideal concentrators, without violating Winston's theorem. Two equivalent CPC collectors with single and segmented absorber were constructed and compared under actual operating conditions. The results showed that the daily thermal efficiency of the collector with segmented absorber is higher (about 13%) than that of the collector with nonsegmented absorber.

  10. 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.

  11. Leaf absorbance and photosynthesis

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

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

  12. Relationship Between Absorber Layer Properties and Device Operation Modes For High Efficiency Thin Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Ravichandran, Ram; Kokenyesi, Robert; Wager, John; Keszler, Douglas; CenterInverse Design Team

    2014-03-01

    A thin film solar cell (TFSC) can be differentiated into two distinct operation modes based on the transport mechanism. Current TFSCs predominantly exploit diffusion to extract photogenerated minority carriers. For efficient extraction, the absorber layer requires high carrier mobilities and long minority carrier lifetimes. Materials exhibiting a strong optical absorption onset near the fundamental band gap allows reduction of the absorber layer thickness to significantly less than 1 μm. In such a TFSC, a strong intrinsic electric field drives minority carrier extraction, resulting in drift-based transport. The basic device configuration utilized in this simulation study is a heterojunction TFSC with a p-type absorber layer. The diffusion/drift device operation modes are simulated by varying the thickness and carrier concentration of the absorber layer, and device performance between the two modes is compared. In addition, the relationship between device operation mode and transport properties, including carrier mobility and minority carrier lifetime are explored. Finally, candidate absorber materials that enable the advantages of a drift-based TFSC developed within the Center for Inverse Design are presented. School of Electrical Engineering and Computer Science.

  13. Advanced neutron absorber materials

    DOEpatents

    Branagan, Daniel J.; Smolik, Galen R.

    2000-01-01

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

  14. 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.

  15. 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.

  16. Wideband-Switchable Metamaterial Absorber Using Injected Liquid Metal

    PubMed Central

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

    2016-01-01

    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. PMID:27546310

  17. Internal absorber solar collector

    DOEpatents

    Sletten, Carlyle J.; Herskovitz, Sheldon B.; Holt, F. S.; Sletten, E. J.

    1981-01-01

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

  18. Lipid-absorbing Polymers

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  19. Electromagnetic power absorber

    NASA Technical Reports Server (NTRS)

    Iwasaki, R. S. (Inventor)

    1979-01-01

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

  20. Warm Absorber Diagnostics of AGN Dynamics

    NASA Astrophysics Data System (ADS)

    Kallman, Timothy

    Warm absorbers and related phenomena are observable manifestations of outflows or winds from active galactic nuclei (AGN) that have great potential value. Understanding AGN outflows is important for explaining the mass budgets of the central accreting black hole, and also for understanding feedback and the apparent co-evolution of black holes and their host galaxies. In the X-ray band warm absorbers are observed as photoelectric absorption and resonance line scattering features in the 0.5-10 keV energy band; the UV band also shows resonance line absorption. Warm absorbers are common in low luminosity AGN and they have been extensively studied observationally. They may play an important role in AGN feedback, regulating the net accretion onto the black hole and providing mechanical energy to the surroundings. However, fundamental properties of the warm absorbers are not known: What is the mechanism which drives the outflow?; what is the gas density in the flow and the geometrical distribution of the outflow?; what is the explanation for the apparent relation between warm absorbers and the surprising quasi-relativistic 'ultrafast outflows' (UFOs)? We propose a focused set of model calculations that are aimed at synthesizing observable properties of warm absorber flows and associated quantities. These will be used to explore various scenarios for warm absorber dynamics in order to answer the questions in the previous paragraph. The guiding principle will be to examine as wide a range as possible of warm absorber driving mechanisms, geometry and other properties, but with as careful consideration as possible to physical consistency. We will build on our previous work, which was a systematic campaign for testing important class of scenarios for driving the outflows. We have developed a set of tools that are unique and well suited for dynamical calculations including radiation in this context. We also have state-of-the-art tools for generating synthetic spectra, which are

  1. Radar Absorbing Materials for Cube Stealth Satellite

    NASA Astrophysics Data System (ADS)

    Micheli, D.; Pastore, R.; Vricella, A.; Marchetti, M.

    A Cube Stealth Satellite is proposed for potential applications in defense system. Particularly, the faces of the satellite exposed to the Earth are made of nanostructured materials able to absorb radar surveillance electromagnetic waves, conferring stealth capability to the cube satellite. Microwave absorbing and shielding material tiles are proposed using composite materials consisting in epoxy-resin and carbon nanotubes filler. The electric permittivity of the composite nanostructured materials is measured and discussed. Such data are used by the modeling algorithm to design the microwave absorbing and the shielding faces of the cube satellite. The electromagnetic modeling takes into account for several incidence angles (0-80°), extended frequency band (2-18 GHz), and for the minimization of the electromagnetic reflection coefficient. The evolutionary algorithm used for microwave layered microwave absorber modeling is the recently developed Winning Particle Optimization. The mathematical model of the absorbing structure is finally experimentally validated by comparing the electromagnetic simulation to the measurement of the manufactured radar absorber tile. Nanostructured composite materials manufacturing process and electromagnetic reflection measurements methods are described. Finally, a finite element method analysis of the electromagnetic scattering by cube stealth satellite is performed.

  2. "Smart" Electromechanical Shock Absorber

    NASA Technical Reports Server (NTRS)

    Stokes, Lebarian; Glenn, Dean C.; Carroll, Monty B.

    1989-01-01

    Shock-absorbing apparatus includes electromechanical actuator and digital feedback control circuitry rather than springs and hydraulic damping as in conventional shock absorbers. Device not subject to leakage and requires little or no maintenance. Attenuator parameters adjusted in response to sensory feedback and predictive algorithms to obtain desired damping characteristic. Device programmed to decelerate slowly approaching vehicle or other large object according to prescribed damping characteristic.

  3. 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.

  4. Effect of the bio-absorbent on the microwave absorption property of the flaky CIPs/rubber absorbers

    NASA Astrophysics Data System (ADS)

    Cheng, Yang; Xu, Yonggang; Cai, Jun; Yuan, Liming; Zhang, Deyuan

    2015-09-01

    Microwave absorbing composites filled with flaky carbonyl iron particles (CIPs) and the bio-absorbent were prepared by using a two-roll mixer and a vulcanizing machine. The electromagnetic (EM) parameters were measured by a vector network analyzer and the reflection loss (RL) was measured by the arch method in the frequency range of 1-4 GHz. The uniform dispersion of the absorbents was verified by comparing the calculated RL with the measured one. The results confirm that as the bio-absorbent was added, the permittivity was increased due to the volume content of absorbents, and the permeability was enlarged owing to the volume content of CIPs and interactions between the two absorbents. The composite filled with bio-absorbents achieved an excellent absorption property at a thickness of 1 mm (minimum RL reaches -7.8 dB), and as the RL was less than -10 dB the absorption band was widest (2.1-3.8 GHz) at a thickness of 2 mm. Therefore, the bio-absorbent is a promising additive candidate on fabricating microwave absorbing composites with a thinner thickness and wider absorption band.

  5. Unidirectional perfect absorber

    PubMed Central

    Jin, L.; Wang, P.; Song, Z.

    2016-01-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices. PMID:27615125

  6. Shock absorber servicing tool

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  7. Unidirectional perfect absorber

    NASA Astrophysics Data System (ADS)

    Jin, L.; Wang, P.; Song, Z.

    2016-09-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices.

  8. Electrochromic absorbance changes of photosynthetic pigments in Rhodopseudomonas sphaeroides. I. Stimulation by secondary electron transport at low temperature.

    PubMed

    de Grooth, B G; Amesz, J

    1977-11-17

    Light-induced absorbance changes were measured at temperatures between --30 and --55 degrees C in chromatophores of Rhodopseudomonas sphaeroides. Absorbance changes due to photooxidation of reaction center bacteriochlorophyll (P-870) were accompanied by a red shift of the absorption bands of a carotenoid. The red shift was inhibited by gramicidin D. The kinetics of P-870 indicated electron transport from the "primary" to a secondary electron acceptor. This electron transport was slowed down by lowering the temperature or increasing the pH of the suspension. Electron transport from soluble cytochrome c to P-870+ occurred in less purified chromatophore preparations. This electron transport was accompanied by a relatively large increase of the carotenoid absorbance change. This agrees with the hypothesis that P-870 is located inside the membrane, so that an additional membrane potential is generated upon transfer of an electron from cytochrome to P-870+. A strong stimulation of the carotenoid changes (more than 10-fold in some experiments) and pronounced band shifts of bacteriochlorophyll B-850 were observed upon illumination in the presence of artifical donor-acceptor systems. Reduced N-methylphenazonium methosulphate (PMS) and N,N,N',N'-tetramethyl-p-phenylene-diamine (TMPD) were fairly efficient donors, whereas endogenous ubiquinone and oxidized PMS acted as secondary acceptor. These results indicate the generation of large membrane potentials at low temperature, caused by sustained electron transport across the chromatophore membrane. The artificial probe, merocyanine MC-V did not show electrochromic band shifts at low temperature.

  9. Narrow-band single photon emission at room temperature based on a single nitrogen-vacancy center coupled to an all-fiber-cavity

    SciTech Connect

    Albrecht, Roland; Bommer, Alexander; Becher, Christoph; Pauly, Christoph; Mücklich, Frank; Schell, Andreas W.; Engel, Philip; Benson, Oliver; Schröder, Tim; Reichel, Jakob

    2014-08-18

    We report the realization of a device based on a single Nitrogen-Vacancy (NV) center in diamond coupled to a fiber-cavity for use as single photon source (SPS). The device consists of two concave mirrors each directly fabricated on the facets of two optical fibers and a preselected nanodiamond containing a single NV center deposited onto one of these mirrors. Both, cavity in- and out-put are directly fiber-coupled, and the emission wavelength is easily tunable by variation of the separation of the two mirrors with a piezo-electric crystal. By coupling to the cavity, we achieve an increase of the spectral photon rate density by two orders of magnitude compared to free-space emission of the NV center. With this work, we establish a simple all-fiber based SPS with promising prospects for the integration into photonic quantum networks.

  10. Ultra-thin metamaterial absorber with extremely bandwidth for solar cell and sensing applications in visible region

    NASA Astrophysics Data System (ADS)

    Tang, Jingyao; Xiao, Zhongyin; Xu, Kaikai

    2016-10-01

    In this paper, we proposed a broadband and ultra-thin metamaterial absorber in the visible region. The absorber is composed of three layers, and the most remarkable difference is that the split ring resonators (SRR) made of metal stannum are encrusted in the indium antimonide (InSb) plane on the top layer. Numerical results reveal that a broadband absorption spectrum above 90% can be realized from 353.9 THz to 613.2 THz due to the coupling effect between the material of stannum and InSb. The metamaterial absorber is ultra-thin, having the total thickness of 56 nm, i.e. less than λ/10 with respect to the center frequency of the absorption band more than 90%. In addition, the impedance matching theory, surface current distributions, E-field and H-field are investigated to explain the physical mechanism of the absorption. The sensing applications are discussed and the simulated results show that the proposed absorber operates well with a good efficiency. Moreover, the visible absorber has potential applications in the aspects of solar energy harvest, integrated photodetectors and so on.

  11. Solar concentrator/absorber

    NASA Technical Reports Server (NTRS)

    Von Tiesenhausen, G. F.

    1976-01-01

    Collector/energy converter, consisting of dual-slope optical concentrator and counterflow thermal energy absorber, is attached to multiaxis support structure. Efficient over wide range of illumination levels, device may be used to generate high temperature steam, serve as solar powered dryer, or power absorption cycle cooler.

  12. Neutron Absorbing Alloys

    SciTech Connect

    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.

  13. Metasurface Broadband Solar Absorber

    PubMed Central

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-01-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999

  14. Metasurface Broadband Solar Absorber

    DOE PAGES

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; ...

    2016-02-01

    Here, we demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Moreover, our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributionsmore » to elucidate how the absorption occurs within the metasurface structure.« less

  15. Metasurface Broadband Solar Absorber

    SciTech Connect

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-02-01

    Here, we demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Moreover, our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure.

  16. Ionized Absorbers in AGN

    NASA Technical Reports Server (NTRS)

    Mathur, S.

    1999-01-01

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

  17. 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.

  18. Optimization and engineering of microwave absorbers

    NASA Astrophysics Data System (ADS)

    Chen, Kuo-Liang

    1998-12-01

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

  19. Band heterotopia.

    PubMed

    Alam, M S; Naila, N

    2010-01-01

    Band heterotopias are one of the rarest groups of congenital disorder that result in variable degree of structural abnormality of brain parenchyma. Band of heterotopic neurons result from a congenital or acquired deficiency of the neuronal migration. MRI is the examination of choice for demonstrating these abnormalities because of the superb gray vs. white matter differentiation, detail of cortical anatomy and ease of multiplanar imaging. We report a case of band heterotopia that showed a bilateral band of gray matter in deep white matter best demonstrated on T2 Wt. and FLAIR images.

  20. Absorbency properties of different brands of standardized endodontic paper points.

    PubMed

    Pumarola-Suñé, J; Solá-Vicens, L; Sentís-Vilalta, J; Canalda-Sahli, C; Brau-Aguadé, E

    1998-12-01

    A comparative study of the absorbency properties of different endodontic paper points has been conducted. Twenty standardized absorbent paper points, size 30, from 13 bands (Dentaline, Zipperer, Kerr, Diadent, Roeko novo, Roeko color, Maillefer, P.D., Schein, Spectrapoint, Proclinic, Euronda, and Alpro) of 12 manufacturers were tested. Each dry paper point was weighted using an electronic laboratory balance. A length of 16 mm from the tip was then lowered in distilled water for 5 s, the paper point was weighted again, and the difference between both measurements was taken as the value of the fluid absorbed. Diadent, Kerr, and Dentalite showed significantly higher absorbencies (p < 0.05) than standardized paper points of the remaining brands. The study demonstrates a wide variation in the absorbency properties of this dental accessory.

  1. Design and simulation of a tunable metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Fu, Yanan; Zhao, Guozhong; Li, Yonghua

    2016-11-01

    A photo-excited tunable and broad band metamaterial absorber in the terahertz region is proposed. The metamaterial absorber is composed of three layers like the sandwich, the top layer is a ring metal-semiconductor square split ring and the bottom layer is a metallic ground plane, these two layers are separated by a dielectric spacer, which we choose as the polyimide. The conductivity of the silicon can be tuned actively with the incident pump power. We use the full wave simulation and the equivalent circuit parameter to analysis this absorber, and interpreted the phenomena showed when the conductivity of the silicon filled in the gap of ring is changed by the electric field. The proposed equivalent circuit parameter can save more time to design this kind of absorber in need. The proposed photo-excited tunable metamaterial absorber can also be used as terahertz modulators and switches.

  2. Using C-Band Dual-Polarization Radar Signatures to Improve Convective Wind Forecasting at Cape Canaveral Air Force Station and NASA Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Amiot, Corey G.; Carey, Lawrence D.; Roeder, William P.; McNamara, Todd M.; Blakeslee, Richard J.

    2017-01-01

    The United States Air Force's 45th Weather Squadron (45WS) is the organization responsible for monitoring atmospheric conditions at Cape Canaveral Air Force Station and NASA Kennedy Space Center (CCAFS/KSC) and issuing warnings for hazardous weather conditions when the need arises. One such warning is issued for convective wind events, for which lead times of 30 and 60 minutes are desired for events with peak wind gusts of 35 knots or greater (i.e., Threshold-1) and 50 knots or greater (i.e., Threshold-2), respectively (Roeder et al. 2014).

  3. Design of Tunable, Thin, and Wide-band Microwave Absorbers

    DTIC Science & Technology

    2011-07-28

    the first part (Section 2) is the theoretical analysis of scattering by a twodimensional periodic array of vertical microstrip lines; the other...first part (Section 2) is the theoretical analysis of scattering by a two- dimensional periodic array of vertical microstrip lines; the other (Section 3... Microstrip Lines This section provides a theoretical analysis of scattering by a two-dimensional (2D) periodic array of vertical microstrip lines

  4. Metamaterial perfect absorber based on artificial dielectric "atoms".

    PubMed

    Liu, Xiaoming; Bi, Ke; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-09-05

    In this work, we numerically designed and then experimentally verified a metamaterial perfect absorber based on artificial dielectric "atoms". This metamaterial absorber is composed of dielectric ceramic material (SrTiO3) "atoms" embedded in a background matrix on a metal plate. The dielectric "atoms" couple strongly to the incident electric and magnetic fields at the Mie resonance mode, leading to the narrow perfect absorption band with simulated and experimental absorptivities of 99% and 98.5% at 8.96 GHz, respectively. The designed metamaterial perfect absorber is polarization insensitive and can operate in wide angle incidence.

  5. Integrated tuned vibration absorbers: a theoretical study.

    PubMed

    Gardonio, Paolo; Zilletti, Michele

    2013-11-01

    This article presents a simulation study on two integrated tuned vibration absorbers (TVAs) designed to control the global flexural vibration of lightly damped thin structures subject to broad frequency band disturbances. The first one consists of a single axial switching TVA composed by a seismic mass mounted on variable axial spring and damper elements so that the characteristic damping and natural frequency of the absorber can be switched iteratively to control the resonant response of three flexural modes of the hosting structure. The second one consists of a single three-axes TVA composed by a seismic mass mounted on axial and rotational springs and dampers, which are arranged in such a way that the suspended mass is characterized by uncoupled heave and pitch-rolling vibrations. In this case the three damping and natural frequency parameters of the absorber are tuned separately to control three flexural modes of the hosting structure. The simulation study shows that the proposed single-unit absorbers produce, respectively, 5.3 and 8.7 dB reductions of the global flexural vibration of a rectangular plate between 20 and 120 Hz.

  6. 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.

  7. 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.

  8. The preprophase band is a localized center of clathrin-mediated endocytosis in late prophase cells of the onion cotyledon epidermis.

    PubMed

    Karahara, Ichirou; Suda, Jinsuke; Tahara, Hiroshi; Yokota, Etsuo; Shimmen, Teruo; Misaki, Kazuyo; Yonemura, Shigenobu; Staehelin, Lucas Andrew; Mineyuki, Yoshinobu

    2009-03-01

    The preprophase band (PPB) marks the site on the plant cell cortex where the cell plate will fuse during the final stage of cytokinesis. Recent studies have shown that several cytoskeletal proteins are depleted at the PPB site, but the processes that bring about these changes are still unknown. We have investigated the membrane systems associated with the PPB regions of epidermal cells of onion cotyledons by means of serial thin sections and electron tomograms. In contrast with specimens preserved by chemical fixatives, our high-pressure frozen cells demonstrated the presence of large numbers of clathrin-coated pits and vesicles in the PPB regions. The vesicles were of two types: clathrin-coated and structurally related, non-coated vesicles. Quantitative analysis of the data revealed that the number of clathrin-coated pits and vesicles is higher in the PPB regions than outside of these regions. Immunofluorescent microscopy using anti-plant clathrin-antibody confirmed this result. In contrast, no differences in secretory activities were observed. We postulate that the removal of membrane proteins by endocytosis plays a role in the formation of PPB 'memory' structures.

  9. Direct band gap silicon crystals predicted by an inverse design method

    NASA Astrophysics Data System (ADS)

    Oh, Young Jun; Lee, In-Ho; Lee, Jooyoung; Kim, Sunghyun; Chang, Kee Joo

    2015-03-01

    Cubic diamond silicon has an indirect band gap and does not absorb or emit light as efficiently as other semiconductors with direct band gaps. Thus, searching for Si crystals with direct band gaps around 1.3 eV is important to realize efficient thin-film solar cells. In this work, we report various crystalline silicon allotropes with direct and quasi-direct band gaps, which are predicted by the inverse design method which combines a conformation space annealing algorithm for global optimization and first-principles density functional calculations. The predicted allotropes exhibit energies less than 0.3 eV per atom and good lattice matches, compared with the diamond structure. The structural stability is examined by performing finite-temperature ab initio molecular dynamics simulations and calculating the phonon spectra. The absorption spectra are obtained by solving the Bethe-Salpeter equation together with the quasiparticle G0W0 approximation. For several allotropes with the band gaps around 1 eV, photovoltaic efficiencies are comparable to those of best-known photovoltaic absorbers such as CuInSe2. This work is supported by the National Research Foundation of Korea (2005-0093845 and 2008-0061987), Samsung Science and Technology Foundation (SSTF-BA1401-08), KIAS Center for Advanced Computation, and KISTI (KSC-2013-C2-040).

  10. 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.

  11. Charge recombination reactions in photosystem II. 2. Transient absorbance difference spectra and their temperature dependence.

    PubMed

    Hillmann, B; Brettel, K; van Mieghem, F; Kamlowski, A; Rutherford, A W; Schlodder, E

    1995-04-11

    Absorbance difference spectra of the transient states in photosystem II (PS II) have been examined in the Qv absorption region between 660 and 700 nm. The P680+Pheo-/P680Pheo, 3P680/P680, and P680+QA-/P680QA spectra were measured in O2-evolving PS II core complexes from Synechococcus and PS II-enriched membrane fragments from spinach. The low-temperature absorbance difference spectra vary only slightly between both PS II preparations. The 3P680/P680 spectrum is characterized by a bleaching at 685 nm at 25 K and indicates weak exciton coupling with neighboring pigment(s). We conclude that P680 absorbs at 685 nm in more intact PS II preparations at cryogenic temperature. The difference spectra of the radical pairs are strongly temperature dependent. At low temperature the P680+QA-/P680QA- spectrum exhibits the strongest bleaching at 675 nm whereas the P680+Phe-/P680Pheo spectra show two distinct bleaching bands at 674 and 684 nm. It is suggested that an electrochronic red shift resulting in a bleaching at 675 nm and an absorbance increase at about 682 nm dominates the spectral features of the charge-separated states. On the basis of the present results and those in the literature, we conclude that the interactions between the pigments and especially the organization of the primary donor must be quite different in PS II compared to bacterial reaction centers, although the basic structural arrangement of the pigments might be similar. Spectral data obtained with samples in the presence of singly and doubly reduced QA indicate that the primary photochemistry in PS II is not strongly influenced by the redox state of QA at low temperature and confirm the results of the accompanying paper [Van Mieghem, F. J. E., Brettel, K., Hillmann, B., Kamlowski, A., Rutherford, A. W., & Schlodder, E. (1995) Biochemistry 34, 4798-4813]. The spectra of the primary radical pair and the reaction center triplet obtained with more intact PS II preparations differ widely from those of D1/D2

  12. Liquid Cryogen Absorber for MICE

    SciTech Connect

    Baynham, D.E.; Bish, P.; Bradshaw, T.W.; Cummings, M.A.; Green,M.A.; Ishimoto, S.; Ivaniouchenkov, I.; Lau, W.; Yang, S.Q.; Zisman, M.S.

    2005-08-20

    The Muon Ionization Cooling Experiment (MICE) will test ionization cooling of muons. In order to have effective ionization cooling, one must use an absorber that is made from a low-z material. The most effective low z materials for ionization cooling are hydrogen, helium, lithium hydride, lithium and beryllium, in that order. In order to measure the effect of material on cooling, several absorber materials must be used. This report describes a liquid-hydrogen absorber that is within a pair of superconducting focusing solenoids. The absorber must also be suitable for use with liquid helium. The following absorber components are discussed in this report; the absorber body, its heat exchanger, the hydrogen system, and the hydrogen safety. Absorber cooling and the thin windows are not discussed here.

  13. Ultra-broadband microwave metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Ding, Fei; Cui, Yanxia; Ge, Xiaochen; Jin, Yi; He, Sailing

    2012-03-01

    A microwave ultra-broadband polarization-independent metamaterial absorber is demonstrated. It is composed of a periodic array of metal-dielectric multilayered quadrangular frustum pyramids. These pyramids possess resonant absorption modes at multi-frequencies, of which the overlapping leads to the total absorption of the incident wave over an ultra-wide spectral band. The experimental absorption at normal incidence is above 90% in the frequency range of 7.8-14.7 GHz, and the absorption is kept large when the incident angle is smaller than 60°. The experimental results agree well with the numerical simulation.

  14. Toward a High-Efficient Utilization of Solar Radiation by Quad-Band Solar Spectral Splitting.

    PubMed

    Cao, Feng; Huang, Yi; Tang, Lu; Sun, Tianyi; Boriskina, Svetlana V; Chen, Gang; Ren, Zhifeng

    2016-12-01

    The promising quad-band solar spectral splitter incorporates the properties of the optical filter and the spectrally selective solar thermal absorber can direct PV band to PV modules and absorb thermal band energy for thermal process with low thermal losses. It provides a new strategy for spectral splitting and offers potential ways for hybrid PVT system design.

  15. Imaging of Damped Ly-alpha Absorbers

    NASA Astrophysics Data System (ADS)

    Jim, K. T. C.; Roth, K. C.

    1998-05-01

    Intervening H I gas clouds toward QSOs give rise to damped Ly-alpha absorption. Because of the high column density (N(H I)>= 2*E(20) cm(-2) ) these systems have been thought to be galactic disks in some stage of formation. However, because potential optical counterparts have not been identified for most damped Ly-alpha systems, it is possible that some of the absorbing systems could be dwarf irregular galaxies or low surface brightness galaxies, and are thus difficult to image. In any case, the absorbers are expected to have small angular separation from the QSOs, and so high resolution imaging is required to differentiate the absorbers from the QSOs. Because previous studies have not shown any dominant morphological form for the few candidate objects known, our images are obtained with the Hawaii tip-tilt system in order to achieve the best possible morphological classification. By imaging in the NIR and optical bands that bracket the 4000 Angstroms break of these Ly-alpha absorbers, we can more readily select candidate objects by photometrically constraining their redshifts. In our sample of 14 QSOs with abosorbers from 1absorbers (Kolhatkar et al.)

  16. Ferroelectrics based absorbing layers

    NASA Astrophysics Data System (ADS)

    Hao, Jianping; Sadaune, Véronique; Burgnies, Ludovic; Lippens, Didier

    2014-07-01

    We show that ferroelectrics-based periodic structure made of BaSrTiO3 (BST) cubes, arrayed onto a metal plate with a thin dielectric spacer film exhibit a dramatic enhancement of absorbance with value close to unity. The enhancement is found around the Mie magnetic resonance of the Ferroelectrics cubes with the backside metal layer stopping any transmitted waves. It also involves quasi-perfect impedance matching resulting in reflection suppression via simultaneous magnetic and electrical activities. In addition, it was shown numerically the existence of a periodicity optimum, which is explained from surface waves analysis along with trade-off between the resonance damping and the intrinsic loss of ferroelectrics cubes. An experimental verification in a hollow waveguide configuration with a good comparison with full-wave numerical modelling is at last reported by measuring the scattering parameters of single and dual BST cubes schemes pointing out coupling effects for densely packed structures.

  17. Black phosphorus saturable absorber for ultrashort pulse generation

    SciTech Connect

    Sotor, J. Sobon, G.; Abramski, K. M.; Macherzynski, W.; Paletko, P.

    2015-08-03

    Low-dimensional materials, due to their unique and versatile properties, are very interesting for numerous applications in electronics and optoelectronics. Recently rediscovered black phosphorus, with a graphite-like layered structure, can be effectively exfoliated up to the single atomic layer called phosphorene. Contrary to graphene, it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, black phosphorus is now intensively investigated and can complement or replace graphene in various photonics and electronics applications. Here, we demonstrate that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation. The mechanically exfoliated ∼300 nm thick layers of black phosphorus were transferred onto the fiber core, and under pulsed excitation at 1560 nm wavelength, its transmission increases by 4.6%. We have demonstrated that the saturable absorption of black phosphorus is polarization sensitive. The fabricated device was used to mode-lock an Er-doped fiber laser. The generated optical solitons with the 10.2 nm bandwidth and 272 fs duration were centered at 1550 nm. The obtained results unambiguously show that black phosphorus can be effectively used for ultrashort pulse generation with performances similar or even better than currently used graphene or carbon nanotubes. This application of black phosphorus proves its great potential to future practical use in photonics.

  18. Electrochemically regenerable carbon dioxide absorber

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  19. Broadband patterned magnetic microwave absorber

    SciTech Connect

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

    2014-07-28

    It is a tough task to greatly improve the working bandwidth for the traditional flat microwave absorbers because of the restriction of available material parameters. In this work, a simple patterning method is proposed to drastically broaden the absorption bandwidth of a conventional magnetic absorber. As a demonstration, an ultra-broadband microwave absorber with more than 90% absorption in the frequency range of 4–40 GHz is designed and experimentally realized, which has a thin thickness of 3.7 mm and a light weight equivalent to a 2-mm-thick flat absorber. In such a patterned absorber, the broadband strong absorption is mainly originated from the simultaneous incorporation of multiple λ/4 resonances and edge diffraction effects. This work provides a facile route to greatly extend the microwave absorption bandwidth for the currently available absorbing materials.

  20. Liquid Hydrogen Absorber for MICE

    SciTech Connect

    Ishimoto, S.; Suzuki, S.; Yoshida, M.; Green, Michael A.; Kuno, Y.; Lau, Wing

    2010-05-30

    Liquid hydrogen absorbers for the Muon Ionization Cooling Experiment (MICE) have been developed, and the first absorber has been tested at KEK. In the preliminary test at KEK we have successfully filled the absorber with {approx}2 liters of liquid hydrogen. The measured hydrogen condensation speed was 2.5 liters/day at 1.0 bar. No hydrogen leakage to vacuum was found between 300 K and 20 K. The MICE experiment includes three AFC (absorber focusing coil) modules, each containing a 21 liter liquid hydrogen absorber made of aluminum. The AFC module has safety windows to separate its vacuum from that of neighboring modules. Liquid hydrogen is supplied from a cryocooler with cooling power 1.5 W at 4.2 K. The first absorber will be assembled in the AFC module and installed in MICE at RAL.

  1. Infrared bolometers with silicon nitride micromesh absorbers

    NASA Technical Reports Server (NTRS)

    Bock, J. J.; Turner, A. D.; DelCastillo, H. M.; Beeman, J. W.; Lange, A. E.; Mauskopf, P. D.

    1996-01-01

    Sensitive far infrared and millimeter wave bolometers fabricated from a freestanding membrane of low stress silicon nitride are reported. The absorber, consisting of a metallized silicon nitride micromesh thermally isolated by radial legs of silicon nitride, is placed in an integrating cavity to efficiently couple to single mode or multiple mode infrared radiation. This structure provides low heat capacity, low thermal conduction and minimal cross section to energetic particles. A neutron transmutation doped Ge thermister is bump bonded to the center of the device and read out with evaporated Cr-Au leads. The limiting performance of the micromesh absorber is discussed and the recent results obtained from a 300 mK cold stage are summarized.

  2. 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.

  3. Timing the warm absorber in NGC4051

    NASA Astrophysics Data System (ADS)

    Silva, C.; Uttley, P.; Costantini, E.

    2015-07-01

    In this work we have combined spectral and timing analysis in the characterization of highly ionized outflows in Seyfert galaxies, the so-called warm absorbers. Here, we present our results on the extensive ˜600ks of XMM-Newton archival observations of the bright and highly variable Seyfert 1 galaxy NGC4051, whose spectrum has revealed a complex multi-component wind. Working simultaneously with RGS and PN data, we have performed a detailed analysis using a time-dependent photoionization code in combination with spectral and Fourier timing techniques. This method allows us to study in detail the response of the gas due to variations in the ionizing flux of the central source. As a result, we will show the contribution of the recombining gas to the time delays of the most highly absorbed energy bands relative to the continuum (Silva, Uttley & Costantini in prep.), which is also vital information for interpreting the continuum lags associated with propagation and reverberation effects in the inner emitting regions. Furthermore, we will illustrate how this powerful method can be applied to other sources and warm-absorber configurations, allowing for a wide range of studies.

  4. Band models and correlations for infrared radiation

    NASA Technical Reports Server (NTRS)

    Tiwari, S. N.

    1975-01-01

    Absorption of infrared radiation by various line and band models are briefly reviewed. Narrow band model relations for absorptance are used to develop 'exact' formulations for total absorption by four wide band models. Application of a wide band model to a particular gas largely depends upon the spectroscopic characteristic of the absorbing-emitting molecule. Seven continuous correlations for the absorption of a wide band model are presented and each one of these is compared with the exact (numerical) solutions of the wide band models. Comparison of these results indicate the validity of a correlation for a particular radiative transfer application. In radiative transfer analyses, use of continuous correlations for total band absorptance provides flexibilities in various mathematical operations.

  5. Energy absorber for the CETA

    NASA Technical Reports Server (NTRS)

    Wesselski, Clarence J.

    1994-01-01

    The energy absorber that was developed for the CETA (Crew Equipment and Translation Aid) on Space Station Freedom is a metal on metal frictional type and has a load regulating feature that prevents excessive stroking loads from occurring while in operation. This paper highlights some of the design and operating aspects and the testing of this energy absorber.

  6. Improvement Of The Helmholtz Absorber

    NASA Technical Reports Server (NTRS)

    Morrow, Duane L.

    1992-01-01

    Helmholtz-resonator system improved to enable it to absorb sound at more than one frequency without appreciable loss of effectiveness at primary frequency. Addition of annular cavities enables absorption of sound at harmonic frequencies in addition to primary frequency. Improved absorber designed for use on structures of high transmission loss. Applied to such machines as fixed-speed engines and fans.

  7. Metal-shearing energy absorber

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

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

  8. 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.

  9. 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

  10. 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.

  11. Optical properties of color centers in calcium-stabilized gadolinium gallium garnets

    SciTech Connect

    Pogatshnik, G.J. ); Cain, L.S. ); Chen, Y. ); Evans, B.D. )

    1991-01-15

    The addition of small amounts of calcium during the crystal growth of large-diameter, gadolinium gallium garnet (GGG) crystals creates color centers that absorb in the near-uv region of the spectrum. Ultraviolet and {gamma}-ray irradiation of the crystals produced changes in the intensities of the uv color-center bands along with a broad absorption throughout the visible spectrum. The color center that gives rise to an absorption band at 350 nm serves as a photoionizable donor center so that uv excitation results in a visible coloration of the crystals. The effects of oxidation and reduction treatments on the strength of the color-center bands and on the radiation response of the material were examined. Photoluminescence bands were observed in both reduced GGG crystals as well as crystals that were irradiated with neutrons. Visible coloration is likely to occur during flashlamp pumping of laser rods that utilize large-diameter GGG crystals as the laser host. The changes in the optical properties of the material under uv excitation indicate that the addition of small amounts of calcium to assist in the growth of large-diameter crystals is likely to result in the degradation of laser performance.

  12. Study of paramagnetic defect centers in as-grown and annealed TiO2 anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR

    PubMed Central

    Misra, S.K.; Andronenko, S.I.; Tipikin, D.; Freed, J. H.; Somani, V.; Prakash, Om

    2016-01-01

    Detailed EPR investigations on as-grown and annealed TiO2 nanoparticles in the anatase and rutile phases were carried out at X-band (9.6 GHz) at 77, 120–300 K and at 236 GHz at 292 K. The analysis of EPR data for as-grown and annealed anatase and rutile samples revealed the presence of several paramagnetic centers: Ti3+, O−, adsorbed oxygen (O2−) and oxygen vacancies. On the other hand, in as-grown rutile samples, there were observed EPR lines due to adsorbed oxygen (O2−) and the Fe3+ ions in both Ti4+ substitutional positions, with and without coupling to an oxygen vacancy in the near neighborhood. Anatase nanoparticles were completely converted to rutile phase when annealed at 1000° C, exhibiting EPR spectra similar to those exhibited by the as-grown rutile nanoparticles. The high-frequency (236 GHz) EPR data on anatase and rutile samples, recorded in the region about g = 2.0 exhibit resolved EPR lines, due to O− and O2− ions enabling determination of their g-values with higher precision, as well as observation of hyperfine sextets due to Mn2+ and Mn4+ ions in anatase. PMID:27041794

  13. 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.

  14. Metal Hydrides as hot carrier cell absorber materials

    NASA Astrophysics Data System (ADS)

    Wang, Pei; Wen, Xiaoming; Shrestha, Santosh; Conibeer, Gavin; Aguey-Zinsou, Kondo-Francois

    2016-09-01

    The hot Carrier Solar Cell (HCSC) allows the photon-induced hot carriers (the carriers with energy larger than the band gap) to be collected before they completely thermalise. The absorber of the HCSC should have a large phononic band gap to supress Klemens Decay, which results in a slow carrier cooling speed. In fact, a large phononic band gap likely exists in a binary compound whose constituent elements have a large mass ratio between each other. Binary hydrides with their overwhelming mass ratio of the constituent elements are important absorber candidates. Study on different types of binary hydrides as potential absorber candidates is presented in this paper. Many binary transition metal hydrides have reported theoretical or experimental phonon dispersion charts which show large phononic band gaps. Among these hydrides, the titanium hydride (TiHX) is outstanding because of its low cost, easy fabrication process and is relatively inert to air and water. A TiHX thin film is fabricated by directly hydrogenating an evaporated titanium thin film. Characterisation shows good crystal quality and the hydrogenation process is believed to be successful. Ultrafast transient absorption (TA) spectroscopy is used to study the electron cooling time of TiHX. The result is very noisy due to the low absorption and transmission of the sample. The evolution of the TA curves has been explained by band to band transition using the calculated band structure of TiH2. Though not reliable due to the high noise, decay time fitting at 700nm and 600nm shows a considerably slow carrier cooling speed of the sample.

  15. An introduction to absorbent dressings.

    PubMed

    Jones, Menna Lloyd

    2014-12-01

    Exudate bathes the wound bed with a serous fluid that contains essential components that promote wound healing. However, excess exudate is often seen as a challenge for clinicians. Absorbent dressings are often used to aid in the management of exudate, with the aim of providing a moist but unmacerated environment. With so many different types of absorbent dressings available today-alongside making a holistic assessment-it is essential that clinicians also have the knowledge and skill to select the most appropriate absorbent dressing for a given patient.

  16. Self-Regulating Shock Absorber

    NASA Technical Reports Server (NTRS)

    Wesselski, Clarence J.

    1995-01-01

    Mechanical shock absorber keeps frictional damping force within tolerable limit. Its damping force does not increase with coefficient of friction between energy-absorbing components; rather, frictional damping force varies only slightly. Relatively insensitive to manufacturing variations and environmental conditions altering friction. Does not exhibit high breakaway friction and consequent sharp increase followed by sharp decrease in damping force at beginning of stroking. Damping force in absorber does not vary appreciably with speed of stroking. In addition, not vulnerable to leakage of hydraulic fluid.

  17. Laparoscopic gastric banding

    MedlinePlus

    ... adjustable gastric banding; Bariatric surgery - laparoscopic gastric banding; Obesity - gastric banding; Weight loss - gastric banding ... gastric banding is not a "quick fix" for obesity. It will greatly change your lifestyle. You must ...

  18. Spectral estimators of absorbed photosynthetically active radiation in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.; Bauer, M. E.

    1985-01-01

    Most models of crop growth and yield require an estimate of canopy leaf area index (LAI) or absorption of radiation. Relationships between photosynthetically active radiation (PAR) absorbed by corn canopies and the spectral reflectance of the canopies were investigated. Reflectance factor data were acquired with a Landsat MSS band radiometer. From planting to silking, the three spectrally predicted vegetation indices examined were associated with more than 95 percent of the variability in absorbed PAR. The relationships developed between absorbed PAR and the three indices were evaluated with reflectance factor data acquired from corn canopies planted in 1979 through 1982. Seasonal cumulations of measured LAI and each of the three indices were associated with greater than 50 percent of the variation in final grain yields from the test years. Seasonal cumulations of daily absorbed PAR were associated with up to 73 percent of the variation in final grain yields. Absorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index. Absorbed PAR may be estimated reliably from spectral reflectance data of crop canopies.

  19. Spectral estimators of absorbed photosynthetically active radiation in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.; Bauer, M. E.

    1984-01-01

    Most models of crop growth and yield require an estimate of canopy leaf area index (LAI) or absorption of radiation. Relationships between photosynthetically active radiation (PAR) absorbed by corn canopies and the spectral reflectance of the canopies were investigated. Reflectance factor data were acquired with a LANDSAT MSS band radiometer. From planting to silking, the three spectrally predicted vegetation indices examined were associated with more than 95% of the variability in absorbed PAR. The relationships developed between absorbed PAR and the three indices were evaluated with reflectance factor data acquired from corn canopies planted in 1979 through 1982. Seasonal cumulations of measured LAI and each of the three indices were associated with greater than 50% of the variation in final grain yields from the test years. Seasonal cumulations of daily absorbed PAR were associated with up to 73% of the variation in final grain yields. Absorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index. Absorbed PAR may be estimated reliably from spectral reflectance data of crop canopies.

  20. Spontaneous emission and absorber theory

    NASA Astrophysics Data System (ADS)

    Pegg, David T.

    1997-01-01

    One of the long term interests of George Series was the construction of a theory of spontaneous emission which does not involve field quantisation. His approach was written in terms of atomic operators only and he drew a parallel with the Wheeler-Feynman absorber theory of radiation. By making a particular extra postulate, he was able to obtain the correct spontaneous emission rate and the Lamb shift reasonably simply and directly. An examination of his approach indicates that this postulate is physically reasonable and the need for it arises because quantisation in his theory occurs after the response of the absorber has been accounted for by means of the radiative reaction field. We review briefly an alternative absorber theory approach to spontaneous emission based on the direct action between the emitting atom and a quantised absorber, and outline some applications to more recent effects of interest in quantum optics.

  1. Guided tissue regeneration. Absorbable barriers.

    PubMed

    Wang, H L; MacNeil, R L

    1998-07-01

    Over the past 15 years, techniques aimed at regeneration of lost periodontal tissue have become widely used and accepted in clinical practice. Among these techniques are those which use the principles of guided tissue regeneration (GTR), wherein barriers (i.e., membranes) are used to control cell and tissue repopulation of the periodontal wound. A variety of non-absorbable and absorbable barriers have been developed and used for this purpose, with a trend in recent years toward increased use of absorbable GTR materials. This article describes the evolution of absorbable barrier materials and overview materials available for clinical use today. In addition, advantages and disadvantages of these materials are discussed, as well as possible new developments in barrier-based GTR therapy.

  2. Countercurrent flow absorber and desorber

    DOEpatents

    Wilkinson, W.H.

    1984-10-16

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

  3. Countercurrent flow absorber and desorber

    DOEpatents

    Wilkinson, William H.

    1984-01-01

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

  4. Infrared spectroelectrochemistry of bacteriochlorophylls and bacteriopheophytins: Implications for the binding of the pigments in the reaction center from photosynthetic bacteria.

    PubMed

    Mäntele, W G; Wollenweber, A M; Nabedryk, E; Breton, J

    1988-11-01

    The IR spectra of the bacteriochlorophyll a and b cations and the bacteriopheophytin a and b anions were obtained by using an IR and optically transparent electrochemical cell. Prominent effects of radical formation on the vibrational spectra were found for bands assigned to the ester, keto, and acetyl C=O groups and for vibrations from macrocycle bonds. The (radical-minus-neutral) difference spectra are compared to the light-induced difference spectra of the primary donor photooxidation and the intermediary acceptor photoreduction in the reaction center of photosynthetic bacteria. Light-induced absorbance changes from bacteriochlorophyll a-containing reaction centers bear striking similarities to the electrochemically induced absorbance changes observed upon formation of bacteriochlorophyll a(+)in vitro. Comparison of the radical formation in vitro in a hydrogen-bonding or a nonhydrogen-bonding solvent suggests an ester C=O group hydrogen bonded in the neutral state but free in the cation state. For the keto C=O group, the same comparison indicates one free carbonyl group. The (anion-minus-neutral) difference spectra of bacteriopheophytin a and b exhibit a single band in the ester C=O frequency range. In contrast, two bands are observed in the difference spectra of the intermediary acceptor reduction in the reaction center of Rhodopseudomonas viridis. The higher frequency band exhibits a sensitivity to (1)H-(2)H exchange, which suggests a contribution from a protonated carboxyl group of an amino acid side chain.

  5. Absorber for wakefield interference management at the entrance of the wiggler of a free electron laser

    DOEpatents

    Marchlik, Matthew; Biallas, George Herman

    2017-03-07

    A method for managing the broad band microwave and TeraHertz (THz) radiation in a free electron laser (FEL) having a wiggler producing power in the electromagnetic spectrum. The method includes placement of broadband microwave and TeraHertz (THz) radiation absorbers on the upstream end of the wiggler. The absorbers dampen the bounced back, broad band microwave and THz radiation returning from the surfaces outside the nose of the cookie-cutter and thus preventing broadening of the electron beam pulse's narrow longitudinal energy distribution. Broadening diminishes the ultimate laser power from the wiggler. The broadband microwave and THz radiation absorbers are placed on either side of the slot in the cookie-cutter that shapes the wake field wave of the electron pulse to the slot shape of the wiggler chamber aperture. The broad band microwave and THz radiation absorber is preferably a non-porous pyrolytic grade of graphite with small grain size.

  6. Perfect selective metamaterial solar absorbers.

    PubMed

    Wang, Hao; Wang, Liping

    2013-11-04

    In this work, we numerically investigate the radiative properties of metamaterial nanostructures made of two-dimensional tungsten gratings on a thin dielectric spacer and an opaque tungsten film from UV to mid-infrared region as potential selective solar absorbers. The metamaterial absorber with single-sized tungsten patches exhibits high absorptance in the visible and near-infrared region due to several mechanisms such as surface plasmon polaritons, magnetic polaritons, and intrinsic bandgap absorption of tungsten. Geometric effects on the resonance wavelengths and the absorptance spectra are studied, and the physical mechanisms are elucidated in detail. The absorptance could be further enhanced in a broader spectral range with double-sized metamaterial absorbers. The total solar absorptance of the optimized metamaterial absorbers at normal incidence could be more than 88%, while the total emittance is less than 3% at 100°C, resulting in total photon-to-heat conversion efficiency of 86% without any optical concentration. Moreover, the metamaterial solar absorbers exhibit quasi-diffuse behaviors as well as polarization independence. The results here will facilitate the design of novel highly efficient solar absorbers to enhance the performance of various solar energy conversion systems.

  7. Surgical suite environmental control system. [using halothane absorbing filter

    NASA Technical Reports Server (NTRS)

    Higginbotham, E. J.; Jacobs, M. L.

    1974-01-01

    Theoretical and experimental work for a systems analysis approach to the problem of surgical suit exhaust systems centered on evaluation of halothane absorbing filters. An activated charcoal-alumina-charcoal combination proved to be the best filter for eliminating halothane through multilayer absorption of gas molecules.

  8. Configurable metamaterial absorber with pseudo wideband spectrum.

    PubMed

    Zhu, Weiren; Huang, Yongjun; Rukhlenko, Ivan D; Wen, Guangjun; Premaratne, Malin

    2012-03-12

    Metamaterials attain their behavior due to resonant interactions among their subwavelength components and thus show specific designer features only in a very narrow frequency band. There is no simple way to dynamically increase the operating bandwidth of a narrowband metamaterial, but it may be possible to change its central frequency, shifting the spectral response to a new frequency range. In this paper, we propose and experimentally demonstrate a metamaterial absorber that can shift its central operating frequency by using mechanical means. The shift is achieved by varying the gap between the metamaterial and an auxiliary dielectric slab parallel to its surface. We also show that it is possible to create multiple absorption peaks by adjusting the size and/or shape of the dielectric slab, and to shift them by moving the slab relative to the metamaterial. Specifically, using numerical simulations we design a microwave metamaterial absorber and experimentally demonstrate that its central frequency can be set anywhere in a 1.6 GHz frequency range. The proposed configuration is simple and easy to make, and may be readily extended to THz frequencies.

  9. Sweeping tuneable vibration absorbers for low-mid frequencies vibration control

    NASA Astrophysics Data System (ADS)

    Gardonio, P.; Zilletti, M.

    2015-10-01

    This paper presents a simulation study concerning the low-mid frequencies control of flexural vibration in a lightly damped thin plate, which is equipped with three sweeping tuneable vibration absorbers and is excited by a rain on the roof broad frequency band stationary disturbance. The sweeping tuneable vibration absorbers are semi-active mass-spring-dashpot systems whose stiffness and damping properties can be varied uniformly within given ranges. They are operated in such a way as their characteristic natural frequencies are continuously varied to control the response of flexural modes that resonate within given frequency bands. More specifically, in this study the three sweeping tuneable vibration absorbers are operated asynchronously, each within one of three sequential frequency bands comprised between 20 and 120, 120 and 220, 220 and 320 Hz. The flexural vibration control effects produced by the three sweeping tuneable vibration absorbers are compared to those produced by three classical tuneable vibration absorbers, each set to control the response of a specific flexural mode of the plate resonating in one of these three frequency bands. The study shows that the proposed sweeping tuneable vibration absorbers outperform the classical tuneable vibration absorbers and produce about 6, 5, 4 dB reduction of the plate overall flexural response in the three frequency bands of operation. Also, the study indicates that the sweeping tuneable vibration absorbers are robust to variations in the plate flexural response. For instance they still produce about 5.1, 5.3, 4.6 dB reductions of the flexural response in the three frequency bands of operation when the plate is tensioned such that the flexural natural frequencies are shifted up from about 40 percent, for the first resonance, to 7 percent, for the tenth resonance.

  10. Fabrication and microwave absorbing properties of NixPy nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Haoran; Wan, Lei; Chen, Yaqiong; Hu, Wenbin; Liu, Lei; Zhong, Cheng; Deng, Yida

    2015-06-01

    Materials possessing microwave absorbing properties have been a researching hotspot for their important applications amid a high frequency electromagnetic waves environment. This paper focuses on the preparation of a series of NixPy(x:y = 2.65-2.73) nanotubes (NTs) and their corresponding microwave absorbing properties. After being heat-treated, different NixPy phases would appear, without damaging their initial hollow morphologies. These processes were accompanied with the alteration of related physical properties. Low enough minimum reflection loss (RL) has been achieved in all of these samples, with -48.63 dB as the lowest one being obtained at the non-heat-treated sample. Besides, a large proportion of the microwave frequency band could be covered on the 450 °C heat-treated sample (over a 4.5 GHz bandwidth). These are indicative of the superior microwave absorbing nature of NixPy NTs.

  11. Hollow carbon spheres in microwaves: Bio inspired absorbing coating

    NASA Astrophysics Data System (ADS)

    Bychanok, D.; Li, S.; Sanchez-Sanchez, A.; Gorokhov, G.; Kuzhir, P.; Ogrin, F. Y.; Pasc, A.; Ballweg, T.; Mandel, K.; Szczurek, A.; Fierro, V.; Celzard, A.

    2016-01-01

    The electromagnetic response of a heterostructure based on a monolayer of hollow glassy carbon spheres packed in 2D was experimentally surveyed with respect to its response to microwaves, namely, the Ka-band (26-37 GHz) frequency range. Such an ordered monolayer of spheres mimics the well-known "moth-eye"-like coating structures, which are widely used for designing anti-reflective surfaces, and was modelled with the long-wave approximation. Based on the experimental and modelling results, we demonstrate that carbon hollow spheres may be used for building an extremely lightweight, almost perfectly absorbing, coating for Ka-band applications.

  12. Photothermal response of near-infrared-absorbing NanoGUMBOS.

    PubMed

    Dumke, Jonathan C; Qureshi, Ammar; Hamdan, Suzana; El-Zahab, Bilal; Das, Susmita; Hayes, Daniel J; Boldor, Dorin; Rupnik, Kresimir; Warner, Isiah M

    2014-01-01

    The photothermal properties of several near-infrared-absorbing nanoparticles derived from group of uniform materials based on organic salts (GUMBOS) and composed of cationic dyes coupled with biocompatible anions are evaluated. These nanoparticles were synthesized using a reprecipitation method performed at various pH values: 2.0, 5.0, 7.0, 9.0, and 11.0. The cations for the nanoparticles derived from GUMBOS (nanoGUMBOS), [1048] and [1061], have absorbance maxima at wavelengths overlapping with human soft tissue absorbance minima. Near-infrared-absorbing nanoGUMBOS excited with a 1064 nm continuous laser led to heat generation, with an average temperature increase of 20.4 ± 2.7 °C. Although the [1061][Deoxycholate] nanoGUMBOS generated the highest temperature increase (23.7 ± 2.4 °C), it was the least photothermally efficient compound (13.0%) due to its relatively large energy band gap of 0.892 eV. The more photothermally efficient compound [1048][Ascorbate] (64.4%) had a smaller energy band gap of 0.861 eV and provided an average photothermal temperature increase of 21.0 ± 2.1 °C.

  13. Mushroom plasmonic metamaterial infrared absorbers

    SciTech Connect

    Ogawa, Shinpei Fujisawa, Daisuke; Hata, Hisatoshi; Uetsuki, Mitsuharu; Misaki, Koji; Kimata, Masafumi

    2015-01-26

    There has been a considerable amount of interest in the development of various types of electromagnetic wave absorbers for use in different wavelength ranges. In particular, infrared (IR) absorbers with wavelength selectivity can be applied to advanced uncooled IR sensors, which would be capable of identifying objects through their radiation spectrum. In the present study, mushroom plasmonic metamaterial absorbers (MPMAs) for the IR wavelength region were designed and fabricated. The MPMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow silicon (Si) posts. A Si post height of 200 nm was achieved by isotropic XeF{sub 2} etching of a thin Si layer sandwiched between metal plates. This fabrication procedure is relatively simple and is consistent with complementary metal oxide semiconductor technology. The absorption spectra of the fabricated MPMAs were experimentally measured. In addition, theoretical calculations of their absorption properties were conducted using rigorous coupled wave analysis. Both the calculated and measured absorbance results demonstrated that these MPMAs can realize strong selective absorption at wavelengths beyond the period of the array by varying the micropatch width. Absorbance values greater than 90% were achieved. Dual- or single-mode absorption can also be selected by varying the width of the Si posts. Pixel structures using such MPMAs could be used as high responsivity, high resolution and fast uncooled IR sensors.

  14. Mushroom plasmonic metamaterial infrared absorbers

    NASA Astrophysics Data System (ADS)

    Ogawa, Shinpei; Fujisawa, Daisuke; Hata, Hisatoshi; Uetsuki, Mitsuharu; Misaki, Koji; Kimata, Masafumi

    2015-01-01

    There has been a considerable amount of interest in the development of various types of electromagnetic wave absorbers for use in different wavelength ranges. In particular, infrared (IR) absorbers with wavelength selectivity can be applied to advanced uncooled IR sensors, which would be capable of identifying objects through their radiation spectrum. In the present study, mushroom plasmonic metamaterial absorbers (MPMAs) for the IR wavelength region were designed and fabricated. The MPMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow silicon (Si) posts. A Si post height of 200 nm was achieved by isotropic XeF2 etching of a thin Si layer sandwiched between metal plates. This fabrication procedure is relatively simple and is consistent with complementary metal oxide semiconductor technology. The absorption spectra of the fabricated MPMAs were experimentally measured. In addition, theoretical calculations of their absorption properties were conducted using rigorous coupled wave analysis. Both the calculated and measured absorbance results demonstrated that these MPMAs can realize strong selective absorption at wavelengths beyond the period of the array by varying the micropatch width. Absorbance values greater than 90% were achieved. Dual- or single-mode absorption can also be selected by varying the width of the Si posts. Pixel structures using such MPMAs could be used as high responsivity, high resolution and fast uncooled IR sensors.

  15. Contribution of recoil atoms to irradiation damage in absorber materials

    NASA Astrophysics Data System (ADS)

    Simeone, D.; Hablot, O.; Micalet, V.; Bellon, P.; Serruys, Y.

    1997-08-01

    Absorbing materials are used to control the reactivity of nuclear reactors by taking advantage of nuclear reactions (e.g., 10B(n,α) 7Li) where neutrons are absorbed. During such reactions, energetic recoils are produced. As a result, radiation damage in absorbing materials originates both from these nuclear reactions and from elastic collisions between neutrons and atoms. This damage eventually leads to a partial destruction of the materials, and this is the main limitation on their lifetime in nuclear reactors. Using a formalism developed to calculate displacements per atoms (dpa) in a multi atomic target, we have calculated damages in terms of displacements per atom in a (n,α) absorbing material taking into account geometrical effects of 10 boron self shielding and transmutation reactions induced by neutrons inside the absorber. Radiation damage is calculated for boron carbide and hafnium diboride ceramics in a Pressurized Water Reactor environment. It is shown that recoils produced by nuclear reactions account for the main part of the radiation damage created in these ceramics. Damages are calculated as a function of the distance from the center of an absorber pellet. Due to the self-shielding effect, these damage curves exhibit sharp maxima, the position of which changes in time.

  16. A variable passive low-frequency absorber

    NASA Astrophysics Data System (ADS)

    Larsen, Niels Werner; Thompson, Eric R.; Gade, Anders Christian

    2005-04-01

    Multi-purpose concert halls face a dilemma. They can host classical music concerts, rock concerts and spoken word performances in a matter of a short period. These different performance types require significantly different acoustic conditions in order to provide the best sound quality to both the performers and the audience. A recommended reverberation time for classical music may be in the range of 1.5-2 s for empty halls, where rock music sounds best with a reverberation time around 0.8-1 s. Modern rhythmic music often contains high levels of sound energy in the low frequency bands but still requires a high definition for good sound quality. Ideally, the absorption of the hall should be adjustable in all frequency bands in order to provide good sound quality for all types of performances. The mid and high frequency absorption is easily regulated, but adjusting the low-frequency absorption has typically been too expensive or requires too much space to be practical for multi-purpose halls. Measurements were made on a variable low-frequency absorber to develop a practical solution to the dilemma. The paper will present the results of the measurements as well as a possible design.

  17. 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.

  18. Magnetically tunable metamaterial perfect absorber

    NASA Astrophysics Data System (ADS)

    Lei, Ming; Feng, Ningyue; Wang, Qingmin; Hao, Yanan; Huang, Shanguo; Bi, Ke

    2016-06-01

    A magnetically tunable metamaterial perfect absorber (MPA) based on ferromagnetic resonance is experimentally and numerically demonstrated. The ferrite-based MPA is composed of an array of ferrite rods and a metallic ground plane. Frequency dependent absorption of the ferrite-based MPA under a series of applied magnetic fields is discussed. An absorption peak induced by ferromagnetic resonance appears in the range of 8-12 GHz under a certain magnetic field. Both the simulated and experimental results demonstrate that the absorption frequency of the ferrite-based MPA can be tuned by the applied magnetic field. This work provides an effective way to fabricate the magnetically tunable metamaterial perfect absorber.

  19. Adaptive inertial shock-absorber

    NASA Astrophysics Data System (ADS)

    Faraj, Rami; Holnicki-Szulc, Jan; Knap, Lech; Seńko, Jarosław

    2016-03-01

    This paper introduces and discusses a new concept of impact absorption by means of impact energy management and storage in dedicated rotating inertial discs. The effectiveness of the concept is demonstrated in a selected case-study involving spinning management, a recently developed novel impact-absorber. A specific control technique performed on this device is demonstrated to be the main source of significant improvement in the overall efficiency of impact damping process. The influence of various parameters on the performance of the shock-absorber is investigated. Design and manufacturing challenges and directions of further research are formulated.

  20. 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.

  1. 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.

  2. Three intervening galaxy absorbers towards GRB 060418: faint and dusty?

    NASA Astrophysics Data System (ADS)

    Ellison, Sara L.; Vreeswijk, Paul; Ledoux, Cédric; Willis, Jon P.; Jaunsen, Andreas; Wijers, Ralph A. M. J.; Smette, Alain; Fynbo, Johan P. U.; Møller, Palle; Hjorth, Jens; Kaufer, Andreas

    2006-10-01

    We present an analysis of three strong, intervening Mg II absorption systems (zabs = 0.603, 0.656, 1.107) towards the optical afterglow of gamma-ray burst (GRB) 060418. From high-resolution Ultraviolet and Visual Echelle Spectrograph (UVES) spectra we measure metal column densities and find that the highest redshift absorber exhibits a large amount of dust depletion compared with damped Lyman absorbers (DLAs) seen in quasi-stellar object (QSO) spectra. The intervening zabs = 1.107 absorber is also unusual in exhibiting a clear 2175-Å bump, the first time this feature has been definitively detected in a GRB spectrum. The GRB afterglow spectrum is best fitted with a two-component extinction curve: a Small Magellanic Cloud (SMC) extinction law at z = 1.49 (the redshift of the host) with E(B - V) = 0.07 +/- 0.01 and a Galactic extinction curve at z ~ 1.1 with E(B - V) = 0.08 +/- 0.01. We also present a moderately deep New Technology Telescope (NTT) R-band image of the GRB 060418 field and spectroscopy of four galaxies within 1 arcmin. None of these objects has a redshift that matches any of the intervening absorbers, and we conclude that the galaxies responsible for the two intervening MgII absorbers at z ~ 0.6 have luminosities .

  3. R-SQUARE IMPEDANCES OF ERL FERRITE HOM ABSORBER.

    SciTech Connect

    HAHN, H.; BURRILL, A.; CALAGA,R.; KAYRAN, D.; ZHAO, Y.

    2005-07-10

    An R&D facility for an Energy Recovery Linac (ERL) intended as part of an electron-cooling project for RHIC is, being constructed at this laboratory. The center piece of the facility is a 5-cell 703.75 MHz super-conducting RF linac. Successful operation will depend on effective HOM damping. It is planned to achieve HOM damping exclusively with ferrite absorbers. The performance of a prototype absorber was measured by transforming it into a resonant cavity and alternatively by a conventional wire method. The results expressed as a surface or R-square impedance are presented in this paper.

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

    NASA Technical Reports Server (NTRS)

    Hall, John Michael

    2004-01-01

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

  5. Counterflow absorber for an absorption refrigeration system

    DOEpatents

    Reimann, Robert C.

    1984-01-01

    An air-cooled, vertical tube absorber for an absorption refrigeration system is disclosed. Strong absorbent solution is supplied to the top of the absorber and refrigerant vapor is supplied to the bottom of the absorber to create a direct counterflow of refrigerant vapor and absorbent solution in the absorber. The refrigeration system is designed so that the volume flow rate of refrigerant vapor in the tubes of the absorber is sufficient to create a substantially direct counterflow along the entire length of each tube in the absorber. This provides several advantages for the absorber such as higher efficiency and improved heat transfer characteristics, and allows improved purging of non-condensibles from the absorber.

  6. The J- and K-Band Brightness of the Solar F Corona Observed during the Solar Eclipse on 1998 February 26

    NASA Astrophysics Data System (ADS)

    Ohgaito, R.; Mann, I.; Kuhn, J. R.; MacQueen, R. M.; Kimura, H.

    2002-10-01

    We analyze J- and K-band observations of the 1998 solar eclipse and derive the F-corona brightness in the K band between 3 and 7 Rsolar from the center of the Sun and in the J band out to 5 Rsolar. The falloff in the K-band brightness from 3 to 7 Rsolar is fitted with a radial power law with exponent -2.4+/-0.1 at the solar equator and with exponent -2.9+0.2-0.1 at the solar pole. This slope is gentler than that derived from observations in 1983 but is steeper than that derived from observations for the 1991 eclipse. The radial profiles agree well with models that explain the F corona with weakly absorbing dust particles. Comparison of the J- and K-band brightness at 3 Rsolar from the center of the Sun indicates a reddening of the F corona with respect to the solar spectrum. The reddening is, however, less pronounced compared to the F corona observed during the 1983 total solar eclipse. This fact may be attributed to a change in the composition of dust near the Sun. As with the radial profiles, the reddening in 1998 is better explained with models that assume weakly absorbing rather than strongly absorbing dust particles in the solar corona. Similar to recent eclipse observations, we do not detect an excess emission feature of near-solar dust in the F corona. We hence can reject the hypothesis that suggests a correlation between the detection of an emission feature and the solar activity cycle.

  7. Triple-band metamaterial absorption utilizing single rectangular hole

    NASA Astrophysics Data System (ADS)

    Kim, Seung Jik; Yoo, Young Joon; Kim, Young Ju; Lee, YoungPak

    2017-01-01

    In the general metamaterial absorber, the single absorption band is made by the single meta-pattern. Here, we introduce the triple-band metamaterial absorber only utilizing single rectangular hole. We also demonstrate the absorption mechanism of the triple absorption. The first absorption peak was caused by the fundamental magnetic resonance in the metallic part between rectangular holes. The second absorption was generated by induced tornado magnetic field. The process of realizing the second band is also presented. The third absorption was induced by the third-harmonic magnetic resonance in the metallic region between rectangular holes. In addition, the visible-range triple-band absorber was also realized by using similar but smaller single rectangular-hole structure. These results render the simple metamaterials for high frequency in large scale, which can be useful in the fabrication of metamaterials operating in the optical range.

  8. Metamaterial Absorbers for Microwave Detection

    DTIC Science & Technology

    2015-06-01

    a) Depiction of metamaterial array of square resonators atop FR4. (b) Metamaterial dimensions and structure...comparison for varying resonator array dimension sizes. ..............23 Figure 12. Absorption derived from raw reflection data...36 x Figure 23. Metamaterial absorber array where resonator dimensions control the detection frequencies and

  9. Oil and fat absorbing polymers

    NASA Technical Reports Server (NTRS)

    Marsh, H. E., Jr. (Inventor)

    1977-01-01

    A method is described for forming a solid network polymer having a minimal amount of crosslinking for use in absorbing fats and oils. The polymer remains solid at a swelling ratio in oil or fat of at least ten and provides an oil absorption greater than 900 weight percent.

  10. Assessment of Thematic Mapper Band-to-band Registration by the Block Correlation Method

    NASA Technical Reports Server (NTRS)

    Card, D. H.; Wrigley, R. C.; Mertz, F. C.; Hall, J. R.

    1985-01-01

    Rectangular blocks of pixels from one band image were statistically correlated against blocks centered on identical pixels from a second band image. The block pairs were shifted in pixel increments both vertically and horizontally with respect to each other and the correlation coefficient to the maximum correlation was taken as the best estimate of registration error for each block pair. For the band combinations of the Arkansas scene studied, the misregistration of TM spectral bands within the noncooled focal plane lie well within the 0.2 pixel target specification. Misregistration between the middle IR bands is well within this specification also. The thermal IR band has an apparent misregistration with TM band 7 of approximately 3 pixels in each direction. The TM band 3 has a misregistration of approximately 0.2 pixel in the across-scan direction and 0.5 pixel in the along-scan direction, with both TM bands 5 and 7.

  11. Assessment of Thematic Mapper band-to-band registration by the block correlation method

    NASA Technical Reports Server (NTRS)

    Card, D. H.; Wrigley, R. C.; Mertz, F. C.; Hall, J. R.

    1983-01-01

    Rectangular blocks of pixels from one band image were statistically correlated against blocks centered on identical pixels from a second band image. The block pairs were shifted in pixel increments both vertically and horizontally with respect to each other and the correlation coefficient to the maximum correlation was taken as the best estimate of registration error for each block pair. For the band combinations of the Arkansas scene studied, the misregistration of TM spectral bands within the noncooled focal plane lie well within the 0.2 pixel target specification. Misregistration between the middle IR bands is well within this specification also. The thermal IR band has an apparent misregistration with TM band 7 of approximately 3 pixels in each direction. The TM band 3 has a misregistration of approximately 0.2 pixel in the across-scan direction and 0.5 pixel in the along-scan direction, with both TM bands 5 and 7.

  12. 47 CFR 90.1213 - Band plan.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Band plan. 90.1213 Section 90.1213 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND... § 90.1213 Band plan. The following channel center frequencies are permitted to be aggregated...

  13. 47 CFR 90.1213 - Band plan.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Band plan. 90.1213 Section 90.1213 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND... § 90.1213 Band plan. (a) The following channel center frequencies are permitted to be aggregated...

  14. 47 CFR 90.1213 - Band plan.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Band plan. 90.1213 Section 90.1213 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND... § 90.1213 Band plan. (a) The following channel center frequencies are permitted to be aggregated...

  15. 47 CFR 90.1213 - Band plan.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Band plan. 90.1213 Section 90.1213 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND... § 90.1213 Band plan. (a) The following channel center frequencies are permitted to be aggregated...

  16. 47 CFR 90.1213 - Band plan.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Band plan. 90.1213 Section 90.1213 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND... § 90.1213 Band plan. The following channel center frequencies are permitted to be aggregated...

  17. OVI absorbers in SDSS spectra

    NASA Astrophysics Data System (ADS)

    Frank, Stephan

    We conducted a systematic search for signatures of the Intergalactic Medium (IGM) in Quasar spectra of the Sloan Digital Sky Survey (SDSS) Data Release 3 (DR3), focusing on finding intervening absorbers via detection of their O VI doublet. We present a search algorithm, and criteria for distinguishing candidates from spurious Lyman a forest lines. In addition, we compare our findings with simulations of the Lyman a forest in order to estimate the detectability of O VI doublets over various redshift intervals. We obtain a sample of 1866 O VI doublet candidates with rest-frame equivalent width >= 0.05 λ in 855 AGN spectra (out of 3702 objects with redshifts in the range accessible for O VI detection). This sample is subdivided into 3 groups according to the likelihood of being real and the potential for follow-up observation of the candidate. The group with the cleanest and most secure candidates is comprised of 145 candidates. 69 of these reside at a velocity separation >= 5000 km/s from the QSO, and can therefore be classified tentatively as intervening absorbers. Most of these absorbers have not been picked up by earlier, automated QSO absorption line detection algorithms. This sample increases the number of known O VI absorbers at redshifts beyond z abs >= 2.7 substantially. We propose to obtain observations of some of the candidates with the best signatures for O VI doublets with high signal-to-noise and high resolution in order to better constrain the physical state of the absorbers. We then focused on a subsample of 387 AGN sightlines with an average S/N >= 5: 0, allowing for the detection of absorbers above a rest-frame equivalent width limit of W r >= 0:19 ? A for the O VI 1032 λ component. Accounting for random interlopers mimicking an O VI doublet, we derive for the first time a secure lower limit for the redshift number density DN/Dz for redshifts z abs >= 2:8. With extensive Monte Carlo simulations we quantify the losses of absorbers due to blending

  18. Light Absorbing Aerosols in Mexico City

    NASA Astrophysics Data System (ADS)

    Marley, N. A.; Kelley, K. L.; Kilaparty, P. S.; Gaffney, J. S.

    2008-12-01

    The direct effects of aerosol radiative forcing has been identified by the IPCC as a major uncertainty in climate modeling. The DOE Megacity Aerosol Experiment-Mexico City (MAX-Mex), as part of the MILAGRO study in March of 2006, was undertaken to reduce these uncertainties by characterization of the optical, chemical, and physical properties of atmospheric aerosols emitted from this megacity environment. Aerosol samples collected during this study using quartz filters were characterized in the uv-visible-infrared by using surface spectroscopic techniques. These included the use of an integrating sphere approach combined with the use of Kubelka-Munk theory to obtain aerosol absorption spectra. In past work black carbon has been assumed to be the only major absorbing species in atmospheric aerosols with an broad band spectral profile that follows a simple inverse wavelength dependence. Recent work has also identified a number of other absorbing species that can also add to the overall aerosol absorption. These include primary organics from biomass and trash burning and secondary organic aerosols including nitrated PAHs and humic-like substances, or HULIS. By using surface diffuse reflection spectroscopy we have also obtained spectra in the infrared that indicate significant IR absorption in the atmospheric window-region. These data will be presented and compared to spectra of model compounds that allow for evaluation of the potential importance of these species in adding strength to the direct radiative forcing of atmospheric aerosols. This work was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64327 as part of the Atmospheric Science Program.

  19. 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.

  20. 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.

  1. Absorbed dose from traversing spherically symmetric, Gaussian radioactive clouds

    SciTech Connect

    Thompson, J.M. ); Poston, J.W. . Dept. of Nuclear Engineering)

    1999-06-01

    If a large radioactive cloud is produced, sampling may require that an airplane traverse the cloud. A method to predict the absorbed dose to the aircrew from penetrating the radioactive cloud is needed. Dose rates throughout spherically symmetric Gaussian clouds of various sizes, and the absorbed doses from traversing the clouds, were calculated. Cloud size is a dominant parameter causing dose to vary by orders of magnitude for a given dose rate measured at some distance. A method to determine cloud size, based on dose rate readings at two or more distances from the cloud center, was developed. This method, however, failed to resolve the smallest cloud sizes from measurements made at 1,000 m to 2,000 m from the cloud center.

  2. Smart absorbing property of composites with MWCNTs and carbonyl iron as the filler

    NASA Astrophysics Data System (ADS)

    Xu, Yonggang; Yuan, Liming; Cai, Jun; Zhang, Deyuan

    2013-10-01

    A smart absorbing composite was prepared by mixing silicone rubber, multi-walled carbon nanotubes (MWCNTs) and flaky carbonyl iron particles (CIPs) in a two-roll mixer. The complex permittivity and permeability of composites with variable compression strain was measured by the transmission method and dc electric conductivity was measured by the standard four-point contact method, then the reflection loss (RL) could be calculated to evaluate the microwave absorbing ability. The results showed that the applied compression strain made the complex permittivity decrease but not obviously due to the broken original conductive network. The enforcement of the strain on the complex permeability was attributed to the orientation of flaky CIPs. With the compressing strain applied on the composites with thickness 1 mm or 1.5 mm, the RL value decreased (minimum -13.2 dB and -25.1 dB) and the absorbing band (RL<-10 dB) was widened (5.2-10.6 GHz and 4.0-8.4 GHz). While as the composite thickness decreased caused by the compression strain, the RL value still decreased (minimum -12.4 dB and -18.6 dB) and the absorbing band was also broadened (6.5-10.7 GHz and 4.4-10.0 GHz). Thus the smart absorbing property was effective on preparing absorbers with wide absorption band and high absorption ratio.

  3. Antimony sulphide, an absorber layer for solar cell application

    NASA Astrophysics Data System (ADS)

    Ali, N.; Hussain, Arshad; Ahmed, R.; Shamsuri, W. N. Wan; Shaari, A.; Ahmad, N.; Abbas, S. M.

    2016-01-01

    Replacement of the toxic, expensive and scarce materials with nontoxic, cheap and earth-abundant one, in solar cell absorber layer, is immensely needed to realize the vision of green and sustainable energy. Two-micrometre-thin antimony sulphide film is considered to be adequate as an absorbing layer in solar cell applications. In this paper, we synthesize antimony sulphide thin films on glass substrate by physical vapour deposition technique, and the obtained films were then annealed at different temperatures (150-250 °C). The as-deposited and annealed samples were investigated for structural and optoelectronic properties using different characterization techniques. The X-ray diffraction analysis showed that the annealed samples were polycrystalline with Sb2S3 phase, while the as-deposited sample was amorphous in nature. The optical properties are measured via optical ellipsometric techniques. The measured absorbance of the film is adequately high, and every photon is found to be absorbed in visible and NIR range. The conductivity type of the films measured by hot-point probe technique is determined to be p-type. The optical band gap of the resulted samples was in the range (2.4-1.3 eV) for the as-deposited and annealed films.

  4. Exploration of nonlinearly shunted piezoelectrics as vibration absorbers

    NASA Astrophysics Data System (ADS)

    Zhou, B.; Zang, C.; Wang, X.

    2016-09-01

    Practical realization of a nonlinearly shunted piezoelectric vibration absorber is numerically explored in this research. It is widely known that the linear resonant piezoelectric shunting strategy, acting as a tuned mass damper, is limited by the massive inductance required in low-frequency cases and sensitivity to drifts in structural frequencies. In order to overcome this limitation, a nonlinear piezoelectric shunting strategy is proposed based on the nonlinear energy sink theory. The essential idea is to passively absorb vibrational energy from the host structure through the intentional use of nonlinearity in piezoelectric shunting. The nonlinearly shunted piezoelectrics are supposed to work over a broad frequency band with a smaller inductance requirement compared with the linear resonant shunting. The nonlinearly shunted piezoelectric vibration absorber is built and applied in a cantilevered beam. Major challenges coming from the nonlinear tuning design for an effective vibration absorber exempted from high isolated response curves will be covered in this research. This numerical study is supposed to pave the way for experimental investigations that are currently in process.

  5. Assessment of Thematic Mapper Band-to-band Registration by the Block Correlation Method

    NASA Technical Reports Server (NTRS)

    Card, D. H.; Wrigley, R. C.; Mertz, F. C.; Hall, J. R.

    1984-01-01

    The design of the Thematic Mapper (TM) multispectral radiometer makes it susceptible to band-to-band misregistration. To estimate band-to-band misregistration a block correlation method is employed. This method is chosen over other possible techniques (band differencing and flickering) because quantitative results are produced. The method correlates rectangular blocks of pixels from one band against blocks centered on identical pixels from a second band. The block pairs are shifted in pixel increments both vertically and horizontally with respect to each other and the correlation coefficient for each shift position is computed. The displacement corresponding to the maximum correlation is taken as the best estimate of registration error for each block pair. Subpixel shifts are estimated by a bi-quadratic interpolation of the correlation values surrounding the maximum correlation. To obtain statistical summaries for each band combination post processing of the block correlation results performed. The method results in estimates of registration error that are consistent with expectations.

  6. Band structure controlled by chiral imprinting

    NASA Astrophysics Data System (ADS)

    Castro-Garay, P.; Adrian Reyes, J.; Ramos-Garcia, R.

    2007-09-01

    Using the configuration of an imprinted cholesteric elastomer immersed in a racemic solvent, the authors find the solution of the boundary-value problem for the reflection and transmission of incident optical waves due to the elastomer. They show a significant width reduction of the reflection band for certain values of nematic penetration depth, which depends on the volume fraction of molecules from the solvent, whose handedness is preferably absorbed. The appearance of nested band gaps of both handednesses during the sorting mixed chiral process is also obtained. This suggests the design of chemically controlled optical filters and optically monitored chiral pumps.

  7. Shock absorber operates over wide range

    NASA Technical Reports Server (NTRS)

    Creasy, W. K.; Jones, J. C.

    1965-01-01

    Piston-type hydraulic shock absorber, with a metered damping system, operates over a wide range of kinetic energy loading rates. It is used for absorbing shock and vibration on mounted machinery and heavy earth-moving equipment.

  8. 21 CFR 872.6050 - Saliva absorber.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... absorber is a device made of paper or cotton intended to absorb moisture from the oral cavity during dental... manufacturing practice requirements of the quality system regulation in part 820 of this chapter, with...

  9. The Challenges of C-band Missile Telemetry

    DTIC Science & Technology

    2013-02-20

    use in WW II for fire control Ku Band 12 – 18 GHz Kurz-under K Band 18 – 27 GHz Kurz (German for short) Ka Band 27 – 40 GHz Kurz-above V Band 40 – 75...target missiles. The issues that make C- band different from S- band are mostly independent of the modulation. It is through phase noise, frequency...thumb is that oscillator phase noise increases 6 dB with each octave increase in the center fre- quency. Consequently, given the fact that C- band is

  10. Semiconductor nanowire optical antenna solar absorbers.

    PubMed

    Cao, Linyou; Fan, Pengyu; Vasudev, Alok P; White, Justin S; Yu, Zongfu; Cai, Wenshan; Schuller, Jon A; Fan, Shanhui; Brongersma, Mark L

    2010-02-10

    Photovoltaic (PV) cells can serve as a virtually unlimited clean source of energy by converting sunlight into electrical power. Their importance is reflected in the tireless efforts that have been devoted to improving the electrical and structural properties of PV materials. More recently, photon management (PM) has emerged as a powerful additional means to boost energy conversion efficiencies. Here, we demonstrate an entirely new PM strategy that capitalizes on strong broad band optical antenna effects in one-dimensional semiconductor nanostructures to dramatically enhance absorption of sunlight. We show that the absorption of sunlight in Si nanowires (Si NWs) can be significantly enhanced over the bulk. The NW's optical properties also naturally give rise to an improved angular response. We propose that by patterning the silicon layer in a thin film PV cell into an array of NWs, one can boost the absorption for solar radiation by 25% while utilizing less than half of the semiconductor material (250% increase in the light absorption per unit volume of material). These results significantly advance our understanding of the way sunlight is absorbed by one-dimensional semiconductor nanostructures and provide a clear, intuitive guidance for the design of efficient NW solar cells. The presented approach is universal to any semiconductor and a wide range of nanostructures; as such, it provides a new PV platform technology.

  11. Semiconductor meta-surface based perfect light absorber.

    PubMed

    Liu, Guiqiang; Nie, Yiyou; Fu, Guolan; Liu, Xiaoshan; Liu, Yi; Tang, Li; Liu, Zhengqi

    2017-04-21

    We numerically proposed and demonstrated a semiconductor meta-surface light absorber, which consists of a silicon patches array on a silicon thin-film and an opaque silver substrate. The Mie resonances of the silicon patches and the fundamental cavity mode of the ultra-thin silicon film couple strongly to the incident optical field, leading to a multi-band perfect absorption. The maximal absorption is above 99.5% and the absorption is polarization-independent. Moreover, the absorption behavior is scalable in the frequency region via tuning the structural parameters. These features hold the absorber platform with wide applications in optoelectronics such as hot-electron excitation and photo-detection.

  12. Role of surface electromagnetic waves in metamaterial absorbers.

    PubMed

    Chen, Wen-Chen; Cardin, Andrew; Koirala, Machhindra; Liu, Xianliang; Tyler, Talmage; West, Kevin G; Bingham, Christopher M; Starr, Tatiana; Starr, Anthony F; Jokerst, Nan M; Padilla, Willie J

    2016-03-21

    Metamaterial absorbers have been demonstrated across much of the electromagnetic spectrum and exhibit both broad and narrow-band absorption for normally incident radiation. Absorption diminishes for increasing angles of incidence and transverse electric polarization falls off much more rapidly than transverse magnetic. We unambiguously demonstrate that broad-angle TM behavior cannot be associated with periodicity, but rather is due to coupling with a surface electromagnetic mode that is both supported by, and well described via the effective optical constants of the metamaterial where we achieve a resonant wavelength that is 19.1 times larger than the unit cell. Experimental results are supported by simulations and we highlight the potential to modify the angular response of absorbers by tailoring the surface wave.

  13. Microwave metamaterial absorber based on multiple square ring structures

    NASA Astrophysics Data System (ADS)

    Zhou, Weicheng; Wang, Pinghe; Wang, Nan; Jiang, Wei; Dong, Xiaochun; Hu, Song

    2015-11-01

    In this paper, we report the design, analysis, and simulation of quintuple-band metamaterial absorber (MMA) in the microwave region. The absorber is constructed of a delicate periodic patterned structures and a metallic background plane, separated by a dielectric substrate. By manipulating the periodic patterned structures, high absorption can be obtained at five specific resonance frequencies. Moreover, the significantly high absorptions of quintuple-peaks are persistent with polarization independence, and the influence of angle of incidence for both TE and TM modes was also elucidated. For explaining the absorption mechanism of proposed structures, the electric and magnetic field distributions and resistance matching principal were given. Importantly, the design idea has the ability to be extended to other frequencies, like terahertz, infrared and optical frequencies.

  14. Improving the laboratory monitoring of absorbent oil

    SciTech Connect

    V.S. Shved; S.S. Sychev; I.V. Safina; S.A. Klykov

    2009-05-15

    The performance of absorbent coal tar oil is analyzed as a function of the constituent and group composition. The qualitative and quantitative composition of the oil that ensures the required absorbent properties is determined. Operative monitoring may be based on absorbent characteristics that permit regulation of the beginning and end of regeneration.

  15. Influence of calcium on transport properties, band spectrum and superconductivity of YBa{sub 2}Cu{sub 3}O{sub y} and YBa{sub 1.5}La{sub 0.5}Cu{sub 3}O{sub y}{sup {center_dot}}

    SciTech Connect

    Gasumyants, V.E.; Vladimirskaya, E.V.; Patrina, I.B.

    1994-12-31

    The comparative investigation of transport phenomena in Y{sub 1-x}Ca{sub x}Ba{sub 2}Cu{sub 3}O{sub y} (0y>6.87 and 6.73y>6.96) and YBa{sub 2-x}La{sub x}Cu{sub 3}O{sub y} (0band. The main parameters of the band spectrum (the band filling with electrons degree and the total effective band width) have been determined. The dependencies of these ones from contents of substituting elements are discussed. Analyzing the results obtained simultaneously with the tendencies in oxygen content and critical temperature change we have confirmed the conclusion that the oxygen sublattice disordering has a determinant effect on band structure parameters and superconductive properties of YBa{sub 2}Cu{sub 3}O{sub y}{sup {center_dot}}. The results obtained suggest that Ca gives rise to some peculiarities in band spectrum of this compound.

  16. 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.

  17. 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.

  18. 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.

  19. MAGIICAT I. THE Mg II ABSORBER-GALAXY CATALOG

    SciTech Connect

    Nielsen, Nikole M.; Churchill, Christopher W.; Kacprzak, Glenn G.; Murphy, Michael T.

    2013-10-20

    We describe the Mg II Absorber-Galaxy Catalog, MAGIICAT, a compilation of 182 spectroscopically identified intermediate redshift (0.07 ≤ z ≤ 1.1) galaxies with measurements of Mg II λλ2796, 2803 absorption from their circumgalactic medium within projected distances of 200 kpc from background quasars. In this work, we present 'isolated' galaxies, which are defined as having no spectroscopically identified galaxy within a projected distance of 100 kpc and a line of sight velocity separation of 500 km s{sup –1}. We standardized all galaxy properties to the ΛCDM cosmology and galaxy luminosities, absolute magnitudes, and rest-frame colors to the B- and K-band on the AB system. We present galaxy properties and rest-frame Mg II equivalent width, W{sub r} (2796), versus galaxy redshift. The well-known anti-correlation between W{sub r} (2796) and quasar-galaxy impact parameter, D, is significant to the 8σ level. The mean color of MAGIICAT galaxies is consistent with an Sbc galaxy for all redshifts. We also present B- and K-band luminosity functions for different W{sub r} (2796) and redshift subsamples: 'weak absorbing' [W{sub r} (2796) < 0.3 Å], 'strong absorbing' [W{sub r} (2796) ≥ 0.3 Å], low redshift (z < (z)), and high redshift (z ≥ (z)), where (z) = 0.359 is the median galaxy redshift. Rest-frame color B – K correlates with M{sub K} at the 8σ level for the whole sample but is driven by the strong absorbing, high-redshift subsample (6σ). Using M{sub K} as a proxy for stellar mass and examining the luminosity functions, we infer that in lower stellar mass galaxies, Mg II absorption is preferentially detected in blue galaxies and the absorption is more likely to be weak.

  20. MAGIICAT I. The Mg II Absorber-Galaxy Catalog

    NASA Astrophysics Data System (ADS)

    Nielsen, Nikole M.; Churchill, Christopher W.; Kacprzak, Glenn G.; Murphy, Michael T.

    2013-10-01

    We describe the Mg II Absorber-Galaxy Catalog, MAGIICAT, a compilation of 182 spectroscopically identified intermediate redshift (0.07 <= z <= 1.1) galaxies with measurements of Mg II λλ2796, 2803 absorption from their circumgalactic medium within projected distances of 200 kpc from background quasars. In this work, we present "isolated" galaxies, which are defined as having no spectroscopically identified galaxy within a projected distance of 100 kpc and a line of sight velocity separation of 500 km s-1. We standardized all galaxy properties to the ΛCDM cosmology and galaxy luminosities, absolute magnitudes, and rest-frame colors to the B- and K-band on the AB system. We present galaxy properties and rest-frame Mg II equivalent width, Wr (2796), versus galaxy redshift. The well-known anti-correlation between Wr (2796) and quasar-galaxy impact parameter, D, is significant to the 8σ level. The mean color of MAGIICAT galaxies is consistent with an Sbc galaxy for all redshifts. We also present B- and K-band luminosity functions for different Wr (2796) and redshift subsamples: "weak absorbing" [Wr (2796) < 0.3 Å], "strong absorbing" [Wr (2796) >= 0.3 Å], low redshift (z < langzrang), and high redshift (z >= langzrang), where langzrang = 0.359 is the median galaxy redshift. Rest-frame color B - K correlates with MK at the 8σ level for the whole sample but is driven by the strong absorbing, high-redshift subsample (6σ). Using MK as a proxy for stellar mass and examining the luminosity functions, we infer that in lower stellar mass galaxies, Mg II absorption is preferentially detected in blue galaxies and the absorption is more likely to be weak.

  1. Carbon dioxide absorbents for rebreather diving.

    PubMed

    Pennefather, John

    2016-09-01

    Firstly I would like to thank SPUMS members for making me a Life Member of SPUMS; I was surprised and greatly honoured by the award. I also want to confirm and expand on the findings on carbon dioxide absorbents reported by David Harvey et al. For about 35 years, I was the main player in deciding which absorbent went into Australian Navy and Army diving sets. On several occasions, suppliers of absorbents to the anaesthesia market tried to supply the Australian military market. On no occasion did they provide absorbent that came close to the minimum absorbent capacity required, generally being 30-40% less efficient than diving-grade absorbents. Because I regard lives as being more important than any likely dollar saving, the best absorbent was always selected unless two suppliers provided samples with the same absorbent capacity. On almost every occasion, there was a clear winner and cost was never considered. I suggest the same argument for the best absorbent should be used by members and their friends who dive using rebreather sets. I make this point because of my findings on a set that was brought to me after the death of its owner. The absorbent was not the type or grain size recommended by the manufacturer of the set and did not resemble any of the diving grade absorbents I knew of. I suspected by its appearance that it was anaesthetic grade absorbent. When I tested the set, the absorbent system failed very quickly so it is likely that carbon dioxide toxicity contributed to his death. The death was not the subject of an inquest and I have no knowledge of how the man obtained the absorbent. Possibly there was someone from an operating theatre staff who unintentionally caused their friend's death by supplying him with 'borrowed absorbent'. I make this point as I would like to discourage members from making a similar error.

  2. Multi-band slow light metamaterial.

    PubMed

    Zhu, Lei; Meng, Fan-Yi; Fu, Jia-Hui; Wu, Qun; Hua, Jun

    2012-02-13

    In this paper, a multi-band slow light metamaterial is presented and investigated. The metamaterial unit cell is composed of three cut wires of different sizes and parallel to each other. Two transparency windows induced by two-two overlaps of absorption bands of three cut wires are observed. The multi-band transmission characteristics and the slow light properties of metamaterial are verified by numerical simulation, which is in a good agreement with theoretical predictions. The impacts of structure parameters on transparency windows are also investigated. Simulation results show the spectral properties can be tuned by adjusting structure parameters of metamaterial. The equivalent circuit model and the synthesis method of the multi-band slow light metamaterial are presented. It is seen from simulation results that the synthesis method accurately predicts the center frequency of the multi-band metamaterial, which opens a door to a quick and accurate construction for multi-band slow light metamaterial.

  3. Engineering the Electronic Band Structure for Multiband Solar Cells

    SciTech Connect

    Lopez, N.; Reichertz, L.A.; Yu, K.M.; Campman, K.; Walukiewicz, W.

    2010-07-12

    Using the unique features of the electronic band structure of GaNxAs1-x alloys, we have designed, fabricated and tested a multiband photovoltaic device. The device demonstrates an optical activity of three energy bands that absorb, and convert into electrical current, the crucial part of the solar spectrum. The performance of the device and measurements of electroluminescence, quantum efficiency and photomodulated reflectivity are analyzed in terms of the Band Anticrossing model of the electronic structure of highly mismatched alloys. The results demonstrate the feasibility of using highly mismatched alloys to engineer the semiconductor energy band structure for specific device applications.

  4. Engineering the electronic band structure for multiband solar cells.

    PubMed

    López, N; Reichertz, L A; Yu, K M; Campman, K; Walukiewicz, W

    2011-01-14

    Using the unique features of the electronic band structure of GaN(x)As(1-x) alloys, we have designed, fabricated and tested a multiband photovoltaic device. The device demonstrates an optical activity of three energy bands that absorb, and convert into electrical current, the crucial part of the solar spectrum. The performance of the device and measurements of electroluminescence, quantum efficiency and photomodulated reflectivity are analyzed in terms of the band anticrossing model of the electronic structure of highly mismatched alloys. The results demonstrate the feasibility of using highly mismatched alloys to engineer the semiconductor energy band structure for specific device applications.

  5. A polarization-independent broadband terahertz absorber

    SciTech Connect

    Shi, Cheng; Zang, XiaoFei E-mail: ymzhu@usst.edu.cn; Wang, YiQiao; Chen, Lin; Cai, Bin; Zhu, YiMing E-mail: ymzhu@usst.edu.cn

    2014-07-21

    A highly efficient broadband terahertz absorber is designed, fabricated, and experimentally as well as theoretically evaluated. The absorber comprises a heavily doped silicon substrate and a well-designed two-dimensional grating. Due to the destructive interference of waves and diffraction, the absorber can achieve over 95% absorption in a broad frequency range from 1 to 2 THz and for angles of incidence from 0° to 60°. Such a terahertz absorber is also polarization-independent due to its symmetrical structure. This omnidirectional and broadband absorber have potential applications in anti-reflection coatings, imaging systems, and so on.

  6. Come Join the Band

    ERIC Educational Resources Information Center

    Olson, Cathy Applefeld

    2011-01-01

    A growing number of students in Blue Springs, Missouri, are joining the band, drawn by a band director who emphasizes caring and inclusiveness. In the four years since Melissia Goff arrived at Blue Springs High School, the school's extensive band program has swelled. The marching band alone has gone from 100 to 185 participants. Also under Goff's…

  7. Multi-Band and Broad-Band Infrared Detectors Based on III-V Materials for Spectral Imaging Instruments

    NASA Technical Reports Server (NTRS)

    Bandara, S. V.; Gunapala, S. D.; Liu, J. K.; Rafol, S. B.; Hill, C. J.; Ting, D. Z.; Mumolo, J. M.; Trinh, T. Q.

    2005-01-01

    Quantum well infrared photodetector technology has shown remarkable success by realizing large-format focal plane arrays in both broad-bands and in multi-bands. The spectral response of these detectors based on the III-V material system are tailorable within the mid and long wavelength IR bands (similar to 3-25 mu m) and possibly beyond. Multi-band and broad-band detector arrays have been developed by vertically integrating stacks of multi quantum wells tailored for response in different wavelengths bands. Each detector stack absorbs photons within the specified wavelength band while allowing the transmission other photons, thus efficiently permitting multiband detection. Flexibility in many design parameters of these detectors allows for tuning and tailoring the spectral shape according to application requirements, specifically for spectral imaging instruments.

  8. Experimental demonstration of a magnetically tunable ferrite based metamaterial absorber.

    PubMed

    Huang, Yongjun; Wen, Guangjun; Zhu, Weiren; Li, Jian; Si, Li-Ming; Premaratne, Malin

    2014-06-30

    We synthesize and systematically characterize a novel type of magnetically tunable metamaterial absorber (MA) by integrating ferrite as a substrate or superstrate into a conventional passive MA. The nearly perfect absorption and tunability of this device is studied both numerically and experimentally within X-band (8-12 GHz) in a rectangular waveguide setup. Our measurements clearly show that the resonant frequency of the MA can be shifted across a wide frequency band by continuous adjustment of a magnetic field acting on the ferrite. Moreover, the effects of substrate/superstrate's thickness on the MA's tunability are discussed. The insight gained from the generic analysis enabled us to design an optimized tunable MA with relative frequency tuning range as larger as 11.5% while keeping the absorptivity higher than 98.5%. Our results pave a path towards applications with tunable devices, such as selective thermal emitters, sensors, and bolometers.

  9. False Color Bands

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    The theme for the weeks of 1/17 and 1/24 is the north polar region of Mars as seen in false color THEMIS images. Ice/frost will typically appear as bright blue in color; dust mantled ice will appear in tones of red/orange.

    In a gray scale image, the suble variations seen in this false color image are almost impossible to identify. Note the orange band in the center of the frame, and the bluer bands to either side of it.

    Image information: VIS instrument. Latitude 87, Longitude 65.5 East (294.5 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  10. Liquid crystal tunable metamaterial absorber.

    PubMed

    Shrekenhamer, David; Chen, Wen-Chen; Padilla, Willie J

    2013-04-26

    We present an experimental demonstration of electronically tunable metamaterial absorbers in the terahertz regime. By incorporation of active liquid crystal into strategic locations within the metamaterial unit cell, we are able to modify the absorption by 30% at 2.62 THz, as well as tune the resonant absorption over 4% in bandwidth. Numerical full-wave simulations match well to experiments and clarify the underlying mechanism, i.e., a simultaneous tuning of both the electric and magnetic response that allows for the preservation of the resonant absorption. These results show that fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications.

  11. Oxalate: Effect on calcium absorbability

    SciTech Connect

    Heaney, R.P.; Weaver, C.M. )

    1989-10-01

    Absorption of calcium from intrinsically labeled Ca oxalate was measured in 18 normal women and compared with absorption of Ca from milk in these same subjects, both when the test substances were ingested in separate meals and when ingested together. Fractional Ca absorption from oxalate averaged 0.100 +/- 0.043 when ingested alone and 0.140 +/- 0.063 when ingested together with milk. Absorption was, as expected, substantially lower than absorption from milk (0.358 +/- 0.113). Nevertheless Ca oxalate absorbability in these women was higher than we had previously found for spinach Ca. When milk and Ca oxalate were ingested together, there was no interference of oxalate in milk Ca absorption and no evidence of tracer exchange between the two labeled Ca species.

  12. Femtosecond infrared spectroscopy of reaction centers from Rhodobacter sphaeroides between 1000 and 1800 cm-1.

    PubMed Central

    Hamm, P; Zurek, M; Mäntele, W; Meyer, M; Scheer, H; Zinth, W

    1995-01-01

    Time-resolved pump-and-probe experiments of reaction centers of the purple bacterium Rhodobacter sphaeroides (R26) in the mid-IR region between 1000 and 1800 cm-1 are recorded with a time resolution of 300-400 fs. The difference spectra of the states P*, P+HA-, and P+QA- with respect to the ground state P predominantly reflect changes of the special pair. They show positive and negative bands due to changes of distinct vibrational modes superimposed on a broad background of enhanced absorption. A number of certain bands can be assigned to the special pair P, to the bacteriopheophytin HA, and to the quinone QA. The temporal evolution of the IR absorbance changes is well described by the time constants known from femtosecond spectroscopy of the electronic states. Differences occur only at very early times, which are indicative of fast vibrational relaxation with a time constant of a few hundred femtoseconds. PMID:7892185

  13. Thermal mechanisms of laser marking in transparent polymers with light-absorbing microparticles

    NASA Astrophysics Data System (ADS)

    Zelenska, K. S.; Zelensky, S. E.; Poperenko, L. V.; Kanev, K.; Mizeikis, V.; Gnatyuk, V. A.

    2016-01-01

    Interaction of highly viscous polystyrene suspensions of light-absorbing microparticles with pulsed radiation of a Q-switched YAG:Nd3+ laser is investigated. Absorption of laser radiation by the suspended microparticles causes thermal decomposition (pyrolysis) of the polymer in the vicinity of the overheated particles. Laser-induced incandescence (LII) of light-absorbing microparticles under irradiation by a sequence of laser pulses is observed. The mechanism of laser marking includes formation of light-absorbing and scattering centers by accumulation of carbonaceous and gaseous products of pyrolysis.

  14. Electromagnetic scattering by pyramidal and wedge absorber

    NASA Technical Reports Server (NTRS)

    Dewitt, Brian T.; Burnside, Walter D.

    1988-01-01

    Electromagnetic scattering from pyramidal and wedge absorbers used to line the walls of modern anechoic chambers is measured and compared with theoretically predicted values. The theoretical performance for various angles of incidence is studied. It is shown that a pyramidal absorber scatters electromagnetic energy more as a random rough surface does. The apparent reflection coefficient from an absorber wall illuminated by a plane wave can be much less than the normal absorber specifications quoted by the manufacturer. For angles near grazing incidence, pyramidal absorbers give a large backscattered field from the pyramid side-faces or edges. The wedge absorber was found to give small backscattered fields for near-grazing incidence. Based on this study, some new guidelines for the design of anechoic chambers are advocated because the specular scattering models used at present do not appear valid for pyramids that are large compared to the wavelength.

  15. 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.

  16. Synthesis of Dyed Monodisperse Poly(methylmethacrylate) Colloids for the Preparation of Submicron Periodic Light Absorbing Arrays.

    DTIC Science & Technology

    1995-07-05

    refractive index. This forms a novel submicron periodic system where a body - centered cubic array of absorbers interact with electromagnetic radiation with little scattering or diffraction of the incident light. jg p.1

  17. Center Size and Center Performance.

    ERIC Educational Resources Information Center

    Helburn, Suzanne; Morris, John

    1996-01-01

    Examined the impact of child care center size on cost, quality, and profits per child. Examined centers ranging from 40 to 80 children and found total cost and revenue per child were similar for small, medium, and large centers. Found profits per child were highest in large centers and that there was no relationship between center quality and…

  18. Wideband long wave infrared metamaterial absorbers based on silicon nitride

    NASA Astrophysics Data System (ADS)

    Üstün, Kadir; Turhan-Sayan, Gönül

    2016-11-01

    In this paper, we present silicon nitride metamaterial absorber designs that accomplish large bandwidth and high absorption in the long wave infrared (LWIR) region. These designs are based on the metal-insulator-metal topology, insulator (silicon nitride), and the top metal (aluminum) layers are optimized to obtain high absorptance values in large bandwidths, for three different silicon nitride based absorber structures. The absorption spectrum of the final design reaches absorptance values above 90% in the wavelength interval between 8.07 μm and 11.97 μm, and above 80% in the wavelength interval between 7.9 μm and 14 μm, in the case of normal incidence. The difficulty in the design process of such absorbers stems from the highly dispersive behavior of silicon nitride in the LWIR region. On the other hand, silicon nitride is a widely used material in microbolometers, and accomplishing wide band absorption in silicon nitride is crucial in this regard. Therefore, this study will pave the way for more efficient infrared imaging devices, which are crucial for defense and security systems. Additionally, such designs may also find applications in thermal emitters.

  19. Graphene metamaterial for multiband and broadband terahertz absorber

    NASA Astrophysics Data System (ADS)

    Gao, Runmei; Xu, Zongcheng; Ding, Chunfeng; Wu, Liang; Yao, Jianquan

    2015-12-01

    In this paper, we present the efficient design of functional graphene thin film metamaterial on a metal-plane separated by a thick dielectric layer. Perfect absorption is characterized by the complete suppression of incident and reflected light and complete dissipation of incident energy. We investigate the properties of graphene metamaterials and demonstrate multiband absorbers that have five absorption bands, using silicon interlayers, in the 0-2.2 THz range. The absorption rate reached up to 99.9% at a frequency of 1.08 THz, and the quality factor was 6.98 for a 0.14 THz bandwidth. We present a novel theoretical interpretation based on standing wave field theory, which shows that coherent superposition of the incident and reflection rays produce stationary waves, and the field energy localized inside the thick spacers and dissipated through the metal-planes. Thus, light was effectively trapped in the metamaterial absorbers with negligible near-field interactions, causing high absorption. The theory developed here explains all features observed in multiband metamaterial absorbers and therefore provides a profound understanding of the underlying physical mechanisms.

  20. Alternative Ear-Canal Measures Related to Absorbance

    PubMed Central

    Neely, Stephen T.; Stenfelt, Stefan; Schairer, Kim S.

    2013-01-01

    Several alternative ear-canal measures are similar to absorbance in their requirement for prior determination of a Thévenin-equivalent sound source. Examples are (1) sound intensity level (SIL), (2) forward-pressure level (FPL), (3) time-domain ear-canal reflectance (TDR), and (4) cochlear reflectance (CR). These four related measures are similar to absorbance in their utilization of wide-band stimuli and their focus on recording ear-canal sound pressure. The related measures differ from absorbance in how the ear-canal pressure is analyzed and in the type of information that is extracted from the recorded response. SIL and FPL have both been shown to be better as measures of sound level in the ear canal compared to sound pressure level (SPL) because they reduced calibration errors due to standing waves in studies of behavioral thresholds and otoacoustic emissions. TDR may be used to estimate ear-canal geometry and may have the potential to assess middle-ear pathology. CR reveals information about the inner ear that is similar to what is provided by other types of otoacoustic emissions and may have theoretical advantages that strengthen its interpretation. PMID:23900185

  1. Tunable broadband metamaterial absorber consisting of ferrite slabs and a copper wire

    NASA Astrophysics Data System (ADS)

    Yang, Yong-Jun; Huang, Yong-Jun; Wen, Guang-Jun; Zhong, Jing-Ping; Sun, Hai-Bin; Oghenemuero, Gordon

    2012-03-01

    A tunable broadband metamaterial absorber is demonstrated at microwave frequencies in this paper. The metamaterial absorber is composed of ferrite slabs with large resonance beamwidths and a copper wire. The theoretical analysis for the effective media parameters is presented to show the mechanism for achieving the perfect absorptivity characteristic. The numerical results of transmission, reflectance, and absorptivity indicate that the metamaterial absorber exhibits a near perfect impedance-match to free space and a high absorptivity of 98.2% for one layer and 99.97% for two layers at 9.9 GHz. The bandwidth with the absorptivity above 90% is about 2.3 GHz. Moreover, the absorption band can be shifted linearly in a wide frequency range by adjusting the magnetic bias. This metamaterial absorber opens a way to prepare perfectly matched layers for engineering applications.

  2. Experimental demonstration of a transparent graphene millimetre wave absorber with 28% fractional bandwidth at 140 GHz

    NASA Astrophysics Data System (ADS)

    Wu, Bian; Tuncer, Hatice M.; Naeem, Majid; Yang, Bin; Cole, Matthew T.; Milne, William I.; Hao, Yang

    2014-02-01

    The development of transparent radio-frequency electronics has been limited, until recently, by the lack of suitable materials. Naturally thin and transparent graphene may lead to disruptive innovations in such applications. Here, we realize optically transparent broadband absorbers operating in the millimetre wave regime achieved by stacking graphene bearing quartz substrates on a ground plate. Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate. An analytical model has been developed to predict the absorption performance and the angular dependence of the absorber. Using a repeated transfer-and-etch process, multilayer graphene was processed to control its surface resistivity. Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz. Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

  3. Ultra-thin wideband magnetic-type metamaterial absorber based on LC resonator at low frequencies

    NASA Astrophysics Data System (ADS)

    Zhang, Linbo; Zhou, Peiheng; Chen, Haiyan; Lu, Haipeng; Xie, Jianliang; Deng, Longjiang

    2015-10-01

    In this paper, we propose to realize a broad absorption band in the frequency regimes of 2-6 GHz based on multiple resonances. A magnetic-type metamaterial absorber with cross-arrow pattern is further demonstrated numerically and experimentally. Two absorption resonances are generated by LC resonance, leading to bandwidth expansion. The equivalent circuit theory and the surface current distributions of the proposed absorber are discussed to analyze the physical mechanism. Moreover, the broad bandwidth can be maintained as incident angle up to 30° for transverse electric polarization and 45° for transverse magnetic polarization. Finally, experimental results show that the proposed absorber with the total thickness of 2.4 mm exhibits a -10 dB absorption bandwidth by more than 70 %. The low-frequency absorber has potential applications in the area of eliminating microwave energy.

  4. Emitter/absorber interface of CdTe solar cells

    SciTech Connect

    Song, Tao; Kanevce, Ana; Sites, James R.

    2016-06-17

    The performance of CdTe solar cells can be very sensitive to their emitter/absorber interfaces, especially for high-efficiency cells with improved bulk properties. When interface defect states are located at efficient recombination energies, performance losses from acceptor-type interface defects can be significant. Numerical simulations show that the emitter/absorber band alignment, the emitter doping and thickness, and the defect properties of the interface (i.e. defect density, defect type, and defect energy) can all play significant roles in the interface recombination. In particular, a type I heterojunction with small conduction-band offset (0.1 eV absorber inversion and hence a large hole barrier adjacent to the interface. As a result, the electron-hole recombination is suppressed due to an insufficient hole supply at the interface. A large spike (..delta..EC >/= 0.4 eV), however, can impede electron transport and lead to a reduction of photocurrent and fill-factor. In contrast to the spike, a 'cliff' (.delta..EC < 0 eV) is likely to allow many holes in the vicinity of the interface, which will assist interface recombination and result in a reduced open-circuit voltage. In addition, a thin and highly-doped emitter can invert the absorber, form a large hole barrier, and decrease device performance losses due to high interface defect density. CdS is the most common emitter material used in CdTe solar cells, but the CdS/CdTe interface is in the cliff category and is not favorable from the band-offset perspective. Other n-type emitter choices, such as (Mg,Zn)O, Cd(S,O), or (Cd,Mg)Te, can be tuned by varying the elemental ratio for an optimal positive value of ..delta..EC. These materials are predicted to yield higher

  5. Emitter/absorber interface of CdTe solar cells

    NASA Astrophysics Data System (ADS)

    Song, Tao; Kanevce, Ana; Sites, James R.

    2016-06-01

    The performance of CdTe solar cells can be very sensitive to the emitter/absorber interface, especially for high-efficiency cells with high bulk lifetime. Performance losses from acceptor-type interface defects can be significant when interface defect states are located near mid-gap energies. Numerical simulations show that the emitter/absorber band alignment, the emitter doping and thickness, and the defect properties of the interface (i.e., defect density, defect type, and defect energy) can all play significant roles in the interface recombination. In particular, a type I heterojunction with small conduction-band offset (0.1 eV ≤ ΔEC ≤ 0.3 eV) can help maintain good cell efficiency in spite of high interface defect density, much like with Cu(In,Ga)Se2 (CIGS) cells. The basic principle is that positive ΔEC, often referred to as a "spike," creates an absorber inversion and hence a large hole barrier adjacent to the interface. As a result, the electron-hole recombination is suppressed due to an insufficient hole supply at the interface. A large spike (ΔEC ≥ 0.4 eV), however, can impede electron transport and lead to a reduction of photocurrent and fill-factor. In contrast to the spike, a "cliff" (ΔEC < 0 eV) allows high hole concentration in the vicinity of the interface, which will assist interface recombination and result in a reduced open-circuit voltage. Another way to mitigate performance losses due to interface defects is to use a thin and highly doped emitter, which can invert the absorber and form a large hole barrier at the interface. CdS is the most common emitter material used in CdTe solar cells, but the CdS/CdTe interface is in the cliff category and is not favorable from the band-offset perspective. The ΔEC of other n-type emitter choices, such as (Mg,Zn)O, Cd(S,O), or (Cd,Mg)Te, can be tuned by varying the elemental ratio for an optimal positive value of ΔEC. These materials are predicted to yield higher voltages and would therefore be

  6. 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.

  7. Nonlinear dynamic vibration absorbers with a saturation

    NASA Astrophysics Data System (ADS)

    Febbo, M.; Machado, S. P.

    2013-03-01

    The behavior of a new type of nonlinear dynamic vibration absorber is studied. A distinctive characteristic of the proposed absorber is the impossibility to extend the system to infinity. The mathematical formulation is based on a finite extensibility nonlinear elastic potential to model the saturable nonlinearity. The absorber is attached to a single degree-of-freedom linear/nonlinear oscillator subjected to a periodic external excitation. In order to solve the equations of motion and to analyze the frequency-response curves, the method of averaging is used. The performance of the FENE absorber is evaluated considering a variation of the nonlinearity of the primary system, the damping and the linearized frequency of the absorber and the mass ratio. The numerical results show that the proposed absorber has a very good efficiency when the nonlinearity of the primary system increases. When compared with a cubic nonlinear absorber, for a large nonlinearity of the primary system, the FENE absorber shows a better effectiveness for the whole studied frequency range. A complete absence of quasi-periodic oscillations is also found for an appropriate selection of the parameters of the absorber. Finally, direct integrations of the equations of motion are performed to verify the accuracy of the proposed method.

  8. Metamaterial absorber with random dendritic cells

    NASA Astrophysics Data System (ADS)

    Zhu, Weiren; Zhao, Xiaopeng

    2010-05-01

    The metamaterial absorber composed of random dendritic cells has been investigated at microwave frequencies. It is found that the absorptivities come to be weaker and the resonant frequency get red shift as the disordered states increasing, however, the random metamaterial absorber still presents high absorptivity more than 95%. The disordered structures can help understanding of the metamaterial absorber and may be employed for practical design of infrared metamaterial absorber, which may play important roles in collection of radiative heat energy and directional transfer enhancement.

  9. UDOF direct improvement by modulating mask absorber thickness

    NASA Astrophysics Data System (ADS)

    Yu, Tuan-Yen; Lio, En Chuan; Chen, Po Tsang; Wei, Chih I.; Chen, Yi Ting; Peng, Ming Chun; Chou, William; Yu, Chun Chi

    2016-10-01

    As the process generation migrate to advanced and smaller dimension or pitch, the mask and resist 3D effects will impact the lithography focus common window severely because of both individual depth-of-focus (iDOF) range decrease and center mismatch. Furthermore, some chemical or thermal factors, such as PEB (Post Exposure Bake) also worsen the usable depth-of-focus (uDOF) performance. So the mismatch of thru-pitch iDOF center should be considered as a lithography process integration issue, and more complicated to partition the 3D effects induced by optical or chemical factors. In order to reduce the impact of 3D effects induced by both optical and chemical issues, and improve iDOF center mismatch, we would like to propose a mask absorber thickness offset approach, which is directly to compensate the iDOF center bias by adjusting mask absorber thickness, for iso, semi-iso or dense characteristics in line, space or via patterns to enlarge common process window, i.e uDOF, which intends to provide similar application as Flexwave[1] (ASML trademark). By the way, since mask absorber thickness offset approach is similar to focus tuning or change on wafer lithography process, it could be acted as the process tuning method of photoresist (PR) profile optimization locally, PR scum improvement in specific patterns or to modulate etching bias to meet process integration request. For mass production consideration, and available material, current att-PSM blank, quartz, MoSi with chrome layer as hard-mask in reticle process, will be implemented in this experiment, i.e. chrome will be kept remaining above partial thru-pitch patterns, and act as the absorber thickness bias in different patterns. And then, from the best focus offset of thru-pitch patterns, the iDOF center shifts could be directly corrected and to enlarge uDOF by increasing the overlap of iDOF. Finally, some negative tone development (NTD) result in line patterns will be demonstrated as well.

  10. Adjustable gastric banding (image)

    MedlinePlus

    ... normal digestive process. In this procedure, a hollow band made of special material is placed around the ... pouch and causes a feeling of fullness. The band can be tightened or loosened over time to ...

  11. Playground Hazards in Atlanta Child Care Centers.

    ERIC Educational Resources Information Center

    Sacks, Jeffrey J.; And Others

    1990-01-01

    Examines 71 of the 605 licensed child care centers in Atlanta for playground hazards and school accidents. Finds 684 hazards in 66 centers, including climbing equipment over 6 feet high with inadequate impact-absorbing undersurfacing that had over twice the rate of fall injuries as climbing equipment under 6 feet high. (FMW)

  12. Exploring Light’s Interactions with Bubbles and Light Absorbers in Photoelectrochemical Devices using Ray Tracing

    SciTech Connect

    Stevens, John Colby

    2012-12-01

    Ray tracing was used to perform optical optimization of arrays of photovoltaic microrods and explore the interaction between light and bubbles of oxygen gas on the surface of the microrods. The incident angle of light was varied over a wide range. The percent of incident light absorbed by the microrods and reflected by the bubbles was computed over this range. It was found that, for the 10 μm diameter, 100 μm tall SrTiO3 microrods simulated in the model, the optimal center-­to-­center spacing was 14 μm for a square grid. This geometry produced 75% average and 90% maximum absorbance. For a triangular grid using the same microrods, the optimal center-­to-­center spacing was 14 μm. This geometry produced 67% average and 85% maximum absorbance. For a randomly laid out grid of 5 μm diameter, 100 μm tall SrTiO3 microrods with an average center-­to-­center spacing of 20 μm, the average absorption was 23% and the maximum absorption was 43%. For a 50% areal coverage fraction of bubbles on the absorber surface, between 2%-­20% of the incident light energy was reflected away from the rods by the bubbles, depending upon incident angle and bubble morphology.

  13. Establishing traceability of photometric absorbance values for accurate measurements of the haemoglobin concentration in blood

    NASA Astrophysics Data System (ADS)

    Witt, K.; Wolf, H. U.; Heuck, C.; Kammel, M.; Kummrow, A.; Neukammer, J.

    2013-10-01

    Haemoglobin concentration in blood is one of the most frequently measured analytes in laboratory medicine. Reference and routine methods for the determination of the haemoglobin concentration in blood are based on the conversion of haeme, haemoglobin and haemiglobin species into uniform end products. The total haemoglobin concentration in blood is measured using the absorbance of the reaction products. Traceable absorbance measurement values on the highest metrological level are a prerequisite for the calibration and evaluation of procedures with respect to their suitability for routine measurements and their potential as reference measurement procedures. For this purpose, we describe a procedure to establish traceability of spectral absorbance measurements for the haemiglobincyanide (HiCN) method and for the alkaline haematin detergent (AHD) method. The latter is characterized by a higher stability of the reaction product. In addition, the toxic hazard of cyanide, which binds to the iron ion of the haem group and thus inhibits the oxygen transport, is avoided. Traceability is established at different wavelengths by applying total least-squares analysis to derive the conventional quantity values for the absorbance from the measured values. Extrapolation and interpolation are applied to get access to the spectral regions required to characterize the Q-absorption bands of the HiCN and AHD methods, respectively. For absorbance values between 0.3 and 1.8, the contributions of absorbance measurements to the total expanded uncertainties (95% level of confidence) of absorbance measurements range from 1% to 0.4%.

  14. Diffuse Interstellar Bands in Emission

    NASA Astrophysics Data System (ADS)

    Williams, T. B.; Sarre, P.; Marshall, C. C. M.; Spekkens, K.; de Naray, R. Kuzio

    Recent Fabry-Pérot observations towards the galaxy NGC 1325 with the Southern African Large Telescope (SALT) led to the serendipitous discovery of an emission feature centered at 661.3 nm arising from material in the interstellar medium (ISM) of our Galaxy; this emission feature lies at the wavelength of one of the sharper and stronger diffuse bands normally seen in absorption. The flux of the feature is 4.2 +/- 0.5 × 10-18 es-1 cm-2 arcsec-2. It appears that this is the first observation of emission from a diffuse band carrier in the ISM, excited in this case by the interstellar radiation field. We present the discovery spectra and describe follow-up measurements proposed for SALT.

  15. Low Power Band to Band Tunnel Transistors

    DTIC Science & Technology

    2010-12-15

    the E-field and tunneling at the source- pocket junction you form a parasitic NPN + transistor and the injection mechanism of carriers into the...hypothesis that the 1000 ° C, 5s anneal split lead to a very wide pocket and the accidental formation of a NPN + transistor , while the 1000 ° C, 1s anneal...Low Power Band to Band Tunnel Transistors Anupama Bowonder Electrical Engineering and Computer Sciences University of California at Berkeley

  16. Device for absorbing mechanical shock

    DOEpatents

    Newlon, C.E.

    1979-08-29

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

  17. Device for absorbing mechanical shock

    DOEpatents

    Newlon, Charles E.

    1980-01-01

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

  18. Dilute Group III-V nitride intermediate band solar cells with contact blocking layers

    DOEpatents

    Walukiewicz, Wladyslaw [Kensington, CA; Yu, Kin Man [Lafayette, CA

    2012-07-31

    An intermediate band solar cell (IBSC) is provided including a p-n junction based on dilute III-V nitride materials and a pair of contact blocking layers positioned on opposite surfaces of the p-n junction for electrically isolating the intermediate band of the p-n junction by blocking the charge transport in the intermediate band without affecting the electron and hole collection efficiency of the p-n junction, thereby increasing open circuit voltage (V.sub.OC) of the IBSC and increasing the photocurrent by utilizing the intermediate band to absorb photons with energy below the band gap of the absorber layers of the IBSC. Hence, the overall power conversion efficiency of a IBSC will be much higher than an conventional single junction solar cell. The p-n junction absorber layers of the IBSC may further have compositionally graded nitrogen concentrations to provide an electric field for more efficient charge collection.

  19. Dilute group III-V nitride intermediate band solar cells with contact blocking layers

    DOEpatents

    Walukiewicz, Wladyslaw; Yu, Kin Man

    2015-02-24

    An intermediate band solar cell (IBSC) is provided including a p-n junction based on dilute III-V nitride materials and a pair of contact blocking layers positioned on opposite surfaces of the p-n junction for electrically isolating the intermediate band of the p-n junction by blocking the charge transport in the intermediate band without affecting the electron and hole collection efficiency of the p-n junction, thereby increasing open circuit voltage (V.sub.OC) of the IBSC and increasing the photocurrent by utilizing the intermediate band to absorb photons with energy below the band gap of the absorber layers of the IBSC. Hence, the overall power conversion efficiency of a IBSC will be much higher than an conventional single junction solar cell. The p-n junction absorber layers of the IBSC may further have compositionally graded nitrogen concentrations to provide an electric field for more efficient charge collection.

  20. Absorbencies of six different rodent beddings: commercially advertised absorbencies are potentially misleading.

    PubMed

    Burn, C C; Mason, G J

    2005-01-01

    Moisture absorbency is one of the most important characteristics of rodent beddings for controlling bacterial growth and ammonia production. However, bedding manufacturers rarely provide information on the absorbencies of available materials, and even when they do, absorption values are usually expressed per unit mass of bedding. Since beddings are usually placed into cages to reach a required depth rather than a particular mass, their volumetric absorbencies are far more relevant. This study therefore compared the saline absorbencies of sawdust, aspen woodchips, two virgin loose pulp beddings (Alpha-Dri and Omega-Dri), reclaimed wood pulp (Tek-Fresh), and corncob, calculated both by volume and by mass. Absorbency per unit volume correlated positively with bedding density, while absorbency per unit mass correlated negatively. Therefore, the relative absorbencies of the beddings were almost completely reversed depending on how absorbency was calculated. By volume, corncob was the most absorbent bedding, absorbing about twice as much saline as Tek-Fresh, the least absorbent bedding. Conversely, when calculated by mass, Tek-Fresh appeared to absorb almost three times as much saline as the corncob. Thus, in practical terms the most absorbent bedding here was corncob, followed by the loose pulp beddings; and this is generally supported by their relatively low ammonia production as seen in previous studies. Many factors other than absorbency determine whether a material is suitable as a rodent bedding, and they are briefly mentioned here. However, manufacturers should provide details of bedding absorbencies in terms of volume, in order to help predict the relative absorbencies of the beddings in practical situations.

  1. 21 CFR 872.6050 - Saliva absorber.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Saliva absorber. 872.6050 Section 872.6050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6050 Saliva absorber. (a) Identification. A...

  2. 21 CFR 872.6050 - Saliva absorber.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Saliva absorber. 872.6050 Section 872.6050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6050 Saliva absorber. (a) Identification. A...

  3. [Absorbed doses in dental radiology].

    PubMed

    Bianchi, S D; Roccuzzo, M; Albrito, F; Ragona, R; Anglesio, S

    1996-01-01

    The growing use of dento-maxillo-facial radiographic examinations has been accompanied by the publication of a large number of studies on dosimetry. A thorough review of the literature is presented in this article. Most studies were carried out on tissue equivalent skull phantoms, while only a few were in vivo. The aim of the present study was to evaluate in vivo absorbed doses during Orthopantomography (OPT). Full Mouth Periapical Examination (FMPE) and Intraoral Tube Panoramic Radiography (ITPR). Measurements were made on 30 patients, reproducing clinical conditions, in 46 anatomical sites, with 24 intra- and 22 extra-oral thermoluminiscent dosimeters (TLDS). The highest doses were measured, in orthopantomography, at the right mandibular angle (1899 mu Gy) in FMPE on the right naso-labial fold (5640 mu Gy and in ITPR on the palatal surface of the left second upper molar (1936 mu Gy). Intraoral doses ranged from 21 mu Gy, in orthopantomography, to 4494 mu Gy in FMPE. Standard errors ranged from 142% in ITPR to 5% in orthopantomography. The highest rate of standard errors was found in FMPE and ITPR. The data collected in this trial are in agreement with others in major literature reports. Disagreements are probably due to different exam acquisition and data collections. Such differences, presented comparison in several sites, justify lower doses in FMPE and ITPR. Advantages and disadvantages of in vivo dosimetry of the maxillary region are discussed, the former being a close resemblance to clinical conditions of examination and the latter the impossibility of collecting values in depth of tissues. Finally, both ITPR and FMPE required lower doses than expected, and can be therefore reconsidered relative to their radiation risk.

  4. Spin and band-gap engineering in copper-doped BN sheet

    SciTech Connect

    Zhou, Yungang; Jiang, Xiao-dong; Duan, G.; Gao, Fei; Zu, Xiaotao T.

    2010-05-01

    We perform first-principles calculations on single- or dimer-Cu absorbed BN sheet. It was found that the band gap of BN sheet was reduced due to the emergence of certain impurity states arisen from Cu atom. The value of band gap depends on the adsorption configuration. Unpaired electron in absorbed single-Cu atom is polarized causing a magnetic moment of 1.0 μB, while no magnetic moment has been detected after dimer-Cu adsorption. Comparing the analogous carbon nanostructures, Cu-absorbed BN sheet is more resistant to oxidation and thereby is more experimentally accessible.

  5. Nucleation of shear bands in amorphous alloys

    PubMed Central

    Perepezko, John H.; Imhoff, Seth D.; Chen, Ming-Wei; Wang, Jun-Qiang; Gonzalez, Sergio

    2014-01-01

    The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load–depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys. PMID:24594599

  6. Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events

    NASA Astrophysics Data System (ADS)

    Wang, P.; Tuinder, O. N. E.; Tilstra, L. G.; de Graaf, M.; Stammes, P.

    2012-10-01

    Cloud and aerosol information is needed in trace gas retrievals from satellite measurements. The Fast REtrieval Scheme for Clouds from the Oxygen A band (FRESCO) cloud algorithm employs reflectance spectra of the O2 A band around 760 nm to derive cloud pressure and effective cloud fraction. In general, clouds contribute more to the O2 A band reflectance than aerosols. Therefore, the FRESCO algorithm does not correct for aerosol effects in the retrievals and attributes the retrieved cloud information entirely to the presence of clouds, and not to aerosols. For events with high aerosol loading, aerosols may have a dominant effect, especially for almost cloud free scenes. We have analysed FRESCO cloud data and Absorbing Aerosol Index (AAI) data from the Global Ozone Monitoring Experiment (GOME-2) instrument on the Metop-A satellite for events with typical absorbing aerosol types, such as volcanic ash, desert dust and smoke. We find that the FRESCO effective cloud fractions are correlated with the AAI data for these absorbing aerosol events and that the FRESCO cloud pressure contains information on aerosol layer pressure. For cloud free scenes, the derived FRESCO cloud pressure is close to the aerosol layer pressure, especially for optically thick aerosol layers. For cloudy scenes, if the strongly absorbing aerosols are located above the clouds, then the retrieved FRESCO cloud pressure may represent the height of the aerosol layer rather than the height of the clouds. Combining FRESCO and AAI data, an estimate for the aerosol layer pressure can be given.

  7. Design of a nonlinear torsional vibration absorber

    NASA Astrophysics Data System (ADS)

    Tahir, Ammaar Bin

    Tuned mass dampers (TMD) utilizing linear spring mechanisms to mitigate destructive vibrations are commonly used in practice. A TMD is usually tuned for a specific resonant frequency or an operating frequency of a system. Recently, nonlinear vibration absorbers attracted attention of researchers due to some potential advantages they possess over the TMDs. The nonlinear vibration absorber, or the nonlinear energy sink (NES), has an advantage of being effective over a broad range of excitation frequencies, which makes it more suitable for systems with several resonant frequencies, or for a system with varying excitation frequency. Vibration dissipation mechanism in an NES is passive and ensures that there is no energy backflow to the primary system. In this study, an experimental setup of a rotational system has been designed for validation of the concept of nonlinear torsional vibration absorber with geometrically induced cubic stiffness nonlinearity. Dimensions of the primary system have been optimized so as to get the first natural frequency of the system to be fairly low. This was done in order to excite the dynamic system for torsional vibration response by the available motor. Experiments have been performed to obtain the modal parameters of the system. Based on the obtained modal parameters, the design optimization of the nonlinear torsional vibration absorber was carried out using an equivalent 2-DOF modal model. The optimality criterion was chosen to be maximization of energy dissipation in the nonlinear absorber attached to the equivalent 2-DOF system. The optimized design parameters of the nonlinear absorber were tested on the original 5-DOF system numerically. A comparison was made between the performance of linear and nonlinear absorbers using the numerical models. The comparison showed the superiority of the nonlinear absorber over its linear counterpart for the given set of primary system parameters as the vibration energy dissipation in the former is

  8. Intraprotein formation of a long wavelength absorbing complex and inhibition of excited-state deprotonation in a chiral hydroxybiphenyl.

    PubMed

    Bonancía, Paula; Vayá, Ignacio; Jiménez, M Consuelo; Miranda, Miguel A

    2012-12-27

    The two enantiomers of 2-(2-hydroxybiphenyl-4-yl)propanoic acid ((S)- and (R)-BPOH) have been selected as probes for human serum albumin (HSA). Photophysical characterization in the absence of protein led to emission maxima, singlet energies, quantum yields, and fluorescence lifetime values of 332 nm, 91 kcal mol(-1), and 0.28 and 1.8 ns for BPOH or 414 nm, 79 kcal mol(-1), and 0.31 and 3.3 ns for the corresponding phenolate BPO(-); the pK(a)* was found to be 1.17. In the presence of HSA, a light-absorbing ground-state complex (S)-BPOH@HSA was detected (maximum at ca. 300 nm) whose intensity increased with increasing protein concentration. The fluorescence spectra of (S)-BPOH in PBS, after addition of HSA, revealed a progressive diminution of the phenolate band, indicating that excited-state deprotonation is disfavored within the hydrophobic protein cavities. A similar trend was observed for (R)-BPOH, but the extent of deprotonation was significantly lower for this enantiomer. Addition of increasing amounts of the site II displacement probe (S)-ibuprofen ((S)-IBP) to BPOH@HSA led to a significant decrease of the absorption maximum at ca. 300 nm and to a recovery of the phenolate emission band at ca. 410 nm, which were again configuration dependent. The transient absorption spectrum of (S)-BPOH consisted on a broad band centered at 380 nm, attributed to the first triplet excited state. A dramatic enhancement of the triplet lifetimes within HSA was observed (19.0 μs within protein versus 1.3 μs in bulk PBS), although no stereodifferentiation was noticed in this case.

  9. Constraints on the relative sizes of intervening Mg II-absorbing clouds and quasar emitting regions

    NASA Astrophysics Data System (ADS)

    Lawther, D.; Paarup, T.; Schmidt, M.; Vestergaard, M.; Hjorth, J.; Malesani, D.

    2012-10-01

    Context. A significantly higher incidence of strong (rest equivalent width Wr > 1 Å) intervening Mg ii absorption is observed along gamma-ray burst (GRB) sight-lines relative to those of quasar sight-lines. A geometrical explanation for this discrepancy has been suggested: the ratio of the beam size of the source to the characteristic size of an Mg ii absorption system can influence the observed Mg ii equivalent width, if these two sizes are comparable. Aims: We investigate whether the differing beam sizes of the continuum source and broad-line region of Sloan Digital Sky Survey (SDSS) quasars produce a discrepancy between the incidence of strong Mg ii absorbers illuminated by the quasar continuum region and those of absorbers illuminated by both continuum and broad-line region light. Methods: We performed a semi-automated search for strong Mg ii absorbers in the SDSS Data Release 7 quasar sample. The resulting strong Mg ii absorber catalog is available at the CDS. We measured the sight-line number density of strong Mg ii absorbers superimposed on and off the quasar C iv λ 1550 and C iii] λ 1909 emission lines. Results: We see no difference in the sight-line number density of strong Mg ii absorbers superimposed on quasar broad emission lines compared to those superimposed on continuum-dominated spectral regions. This suggests that the Mg ii absorbing clouds typically observed as intervening absorbers in quasar spectra are larger than the beam sizes of both the continuum-emitting regions and broad line-emitting regions in the centers of quasars, corresponding to a lower limit of the order of 1017 cm for the characteristic size of an Mg ii absorbing cloud. Catalog of Mg II absorbers is available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/546/A67

  10. Thin film absorber for a solar collector

    DOEpatents

    Wilhelm, William G.

    1985-01-01

    This invention pertains to energy absorbers for solar collectors, and more particularly to high performance thin film absorbers. The solar collectors comprising the absorber of this invention overcome several problems seen in current systems, such as excessive hardware, high cost and unreliability. In the preferred form, the apparatus features a substantially rigid planar frame with a thin film window bonded to one planar side of the frame. An absorber in accordance with the present invention is comprised of two thin film layers that are sealed perimetrically. In a preferred embodiment, thin film layers are formed from a metal/plastic laminate. The layers define a fluid-tight planar envelope of large surface area to volume through which a heat transfer fluid flows. The absorber is bonded to the other planar side of the frame. The thin film construction of the absorber assures substantially full envelope wetting and thus good efficiency. The window and absorber films stress the frame adding to the overall strength of the collector.

  11. Absorber and emitter for solar thermo-photovoltaic systems to achieve efficiency exceeding the Shockley-Queisser limit.

    PubMed

    Rephaeli, Eden; Fan, Shanhui

    2009-08-17

    We present theoretical considerations as well as detailed numerical design of absorber and emitter for Solar Thermophotovoltaics (STPV) applications. The absorber, consisting of an array of tungsten pyramids, was designed to provide near-unity absorptivity over all solar wavelengths for a wide angular range, enabling it to absorb light effectively from solar sources regardless of concentration. The emitter, a tungsten slab with Si/SiO(2) multilayer stack, provides a sharp emissivity peak at the solar cell band-gap while suppressing emission at lower frequencies. We show that, under a suitable light concentration condition, and with a reasonable area ratio between the emitter and absorber, a STPV system employing such absorber-emitter pair and a single-junction solar cell can attain efficiency that exceeds the Shockley-Queisser limit.

  12. Intracavity absorption with a continuous wave dye laser - Quantification for a narrowband absorber

    NASA Technical Reports Server (NTRS)

    Brobst, William D.; Allen, John E., Jr.

    1987-01-01

    An experimental investigation of the dependence of intracavity absorption on factors including transition strength, concentration, absorber path length, and pump power is presented for a CW dye laser with a narrow-band absorber (NO2). A Beer-Lambert type relationship is found over a small but useful range of these parameters. Quantitative measurement of intracavity absorption from the dye laser spectral profiles showed enhancements up to 12,000 (for pump powers near lasing threshold) when compared to extracavity measurements. The definition of an intracavity absorption coefficient allowed the determination of accurate transition strength ratios, demonstrating the reliability of the method.

  13. A selective pyroelectric detector of millimeter-wave radiation with an ultrathin resonant meta-absorber

    NASA Astrophysics Data System (ADS)

    Paulish, A. G.; Kuznetsov, S. A.

    2016-11-01

    The results of experimental investigations of spectral and amplitude-frequency characteristics for a discrete wavelength-selective pyroelectric detector operating in the millimetric band are presented. The high spectral selectivity is attained due to integrating the detector with a resonant meta-absorber designed for a close-to-unity absorptivity at 140 GHz. It is demonstrated that the use of this meta-absorber provides an opportunity to construct small-sized and inexpensive multispectral polarization-sensitive systems for radiation detection in the range of millimeter and submillimeter waves.

  14. Optimal design of linear and non-linear dynamic vibration absorbers

    NASA Astrophysics Data System (ADS)

    Jordanov, I. N.; Cheshankov, B. I.

    1988-05-01

    An efficient numerical method is applied to obtain optimal parameters for both linear and non-linear damped dynamic vibration absorbers. The minimization of the vibration response has been carried out for damped as well as undamped force excited primary systems with linear and non-linear spring characteristics. Comparison is made with the optimum absorber parameters that are determined by using Den Hartog's classical results in the linear case. Six optimization criteria by which the response is minimized over narrow and broad frequency bands are examined. Pareto optimal solutions of the multi-objective decision making problem are obtained.

  15. Frequency-Switchable Metamaterial Absorber Injecting Eutectic Gallium-Indium (EGaIn) Liquid Metal Alloy.

    PubMed

    Ling, Kenyu; Kim, Hyung Ki; Yoo, Minyeong; Lim, Sungjoon

    2015-11-06

    In this study, we demonstrated a new class of frequency-switchable metamaterial absorber in the X-band. Eutectic gallium-indium (EGaIn), a liquid metal alloy, was injected in a microfluidic channel engraved on polymethyl methacrylate (PMMA) to achieve frequency switching. Numerical simulation and experimental results are presented for two cases: when the microfluidic channels are empty, and when they are filled with liquid metal. To evaluate the performance of the fabricated absorber prototype, it is tested with a rectangular waveguide. The resonant frequency was successfully switched from 10.96 GHz to 10.61 GHz after injecting liquid metal while maintaining absorptivity higher than 98%.

  16. A metamaterial absorber for the terahertz regime: design, fabrication and characterization.

    PubMed

    Tao, Hu; Landy, Nathan I; Bingham, Christopher M; Zhang, Xin; Averitt, Richard D; Padilla, Willie J

    2008-05-12

    We present a metamaterial that acts as a strongly resonant absorber at terahertz frequencies. Our design consists of a bilayer unit cell which allows for maximization of the absorption through independent tuning of the electrical permittivity and magnetic permeability. An experimental absorptivity of 70% at 1.3 terahertz is demonstrated. We utilize only a single unit cell in the propagation direction, thus achieving an absorption coefficient alpha = 2000 cm(-1). These metamaterials are promising candidates as absorbing elements for thermally based THz imaging, due to their relatively low volume, low density, and narrow band response.

  17. Frequency-Switchable Metamaterial Absorber Injecting Eutectic Gallium-Indium (EGaIn) Liquid Metal Alloy

    PubMed Central

    Ling, Kenyu; Kim, Hyung Ki; Yoo, Minyeong; Lim, Sungjoon

    2015-01-01

    In this study, we demonstrated a new class of frequency-switchable metamaterial absorber in the X-band. Eutectic gallium-indium (EGaIn), a liquid metal alloy, was injected in a microfluidic channel engraved on polymethyl methacrylate (PMMA) to achieve frequency switching. Numerical simulation and experimental results are presented for two cases: when the microfluidic channels are empty, and when they are filled with liquid metal. To evaluate the performance of the fabricated absorber prototype, it is tested with a rectangular waveguide. The resonant frequency was successfully switched from 10.96 GHz to 10.61 GHz after injecting liquid metal while maintaining absorptivity higher than 98%. PMID:26561815

  18. The nonlinear piezoelectric tuned vibration absorber

    NASA Astrophysics Data System (ADS)

    Soltani, P.; Kerschen, G.

    2015-07-01

    This paper proposes a piezoelectric vibration absorber, termed the nonlinear piezoelectric tuned vibration absorber (NPTVA), for the mitigation of nonlinear resonances of mechanical systems. The new feature of the NPTVA is that its nonlinear restoring force is designed according to a principle of similarity, i.e., the NPTVA should be an electrical analog of the nonlinear host system. Analytical formulas for the NPTVA parameters are derived using the homotopy perturbation method. Doing so, a nonlinear generalization of Den Hartog’s equal-peak tuning rule is developed for piezoelectric vibration absorbers.

  19. Hybrid Band effects program (Lockheed Martin shared vision CRADA)

    SciTech Connect

    Bacon, L. D.

    2012-03-01

    Hybrid Band{trademark} (H-band) is a Lockheed Martin Missiles and Fire Control (LMMFC) designation for a specific RF modulation that causes disruption of select electronic components and circuits. H-Band enables conventional high-power microwave (HPM) effects (with a center frequency of 1 to 2 GHz, for example) using a higher frequency carrier signal. The primary technical objective of this project was to understand the fundamental physics of Hybrid Band{trademark} Radio Frequency effects on electronic systems. The follow-on objective was to develop and validate a Hybrid Band{trademark} effects analysis process.

  20. Wild Band Edges: The Role of Bandgap Grading and Band-Edge Fluctuations in High-Efficiency Chalcogenide Devices: Preprint

    SciTech Connect

    Repins, Ingrid; Mansfield, Lorelle; Kanevce, Ana; Jensen, Soren A.; Kuciauskas, Darius; Glynn, Stephen; Barnes, Teresa; Metzger, Wyatt; Burst, James; Jiang, Chun-Sheng; Dippo, Patricia; Harvey, Steve; Teeter, Glenn; Perkins, Craig; Egaas, Brian; Zakutayev, Andriy; Alsmeier, J.-H.; Lussky, T.; Korte, L.; Wilks, R. G.; Bar, M.; Yan, Y.; Lany, Stephan; Zawadzki, Pawel; Park, Ji-Sang; Wei, Suhuai

    2016-06-16

    Band-edge effects -- including grading, electrostatic fluctuations, bandgap fluctuations, and band tails -- affect chalcogenide device efficiency. These effects now require more careful consideration as efficiencies increase beyond 20%. Several aspects of the relationships between band-edge phenomena and device performance for NREL absorbers are examined. For Cu(In,Ga)Se2 devices, recent increases in diffusion length imply changes to optimum bandgap profile. The origin, impact, and modification of electrostatic and bandgap fluctuations are also discussed. The application of the same principles to devices based on CdTe, kesterites, and emerging absorbers (Cu2SnS3, CuSbS2), considering differences in materials properties and defect formation energies, is examined.

  1. Wild Band Edges: The Role of Bandgap Grading and Band-Edge Fluctuations in High-Efficiency Chalcogenide Devices

    SciTech Connect

    Repins, Ingrid; Mansfield, Lorelle; Kanevce, Ana; Jensen, Soren A.; Kuciauskas, Darius; Glynn, Stephen; Barnes, Teresa; Metzger, Wyatt; Burst, James; Jiang, Chun-Sheng; Dippo, Patricia; Harvey, Steve; Teeter, Glenn; Perkins, Craig; Egaas, Brian; Zakutayev, Andriy; Alsmeier, J.-H.; Lussky, T.; Korte, L.; Wilks, R. G.; Bar, M.; Yan, Y.; Lany, Stephan; Zawadzki, Pawel; Park, Ji-Sang; Wei, Suhuai

    2016-11-21

    Band-edge effects - including grading, electrostatic fluctuations, bandgap fluctuations, and band tails - affect chalcogenide device efficiency. These effects now require more careful consideration as efficiencies increase beyond 20%. Several aspects of the relationships between band-edge phenomena and device performance for NREL absorbers are examined. For Cu(In, Ga)Se2 devices, recent increases in diffusion length imply changes to the optimum bandgap profile. The origin, impact, and modification of electrostatic and bandgap fluctuations are also discussed. The application of the same principles to devices based on CdTe, kesterites, and emerging absorbers (Cu2SnS3, CuSbS2), considering differences in materials properties, is examined.

  2. Wide Band to ''Double Band'' upgrade

    SciTech Connect

    Kasper, P.; Currier, R.; Garbincius, P.; Butler, J.

    1988-06-01

    The Wide Band beam currently uses electrons obtained from secondary photon conversions to produce the photon beam incident on the experimental targets. By transporting the positrons produced in these conversions as well as the electrons it is possible to almost double the number of photons delivered to the experiments per primary beam proton. 11 figs.

  3. NEAR-INFRARED IMAGING OF SIX METAL-RICH QUASAR ABSORBER GALAXY FIELDS

    SciTech Connect

    Straka, Lorrie A.; Kulkarni, Varsha P.; York, Donald G.

    2011-06-15

    Absorption lines in quasar spectra allow us to locate and study intervening galaxies. In order to obtain a clearer picture of these absorber galaxies, we have used the Near-Infrared Camera Fabry-Perot System at Apache Point Observatory to obtain near-infrared broadband images in one or more filters (J and K{sub s} ) of six quasar fields containing metal-rich low-z damped or sub-damped Ly{alpha} systems. These data allow us to search for the galaxies and constrain their luminosities. Candidate absorber galaxies are detected at 2.''01-7.''38 separation from the quasar in three out of six fields in the J and K{sub s} bands at >3{sigma} level with luminosities ranging from log(L/L{sub sun}) = 10.44-10.36 in the J band (for E-Sc type galaxies) and log(L/L{sub sun}) = 11.59-10.03 in the K{sub s} band for our detections. We place limits on the remaining fields with no detections of log(L/L{sub sun}) <10.83-9.75 for the J band and log(L/L{sub sun}) <10.43-10.05 for the K{sub s} band. We are also able to utilize Sloan Digital Sky Survey spectra for each field to calculate optical fluxes and limits as well as limits on star formation rate via [O II]{lambda}3727 emission in spectra. Our data, combined with other recent imaging results for metal-rich absorbers, suggest a possible positive correlation between absorber metallicity and galaxy luminosity, although the samples are still small.

  4. Tuning Ferritin's Band Gap through Mixed Metal Oxide Nanoparticle Formation.

    PubMed

    Olsen, Cameron; Embley, Jacob; Hansen, Kameron; Henrichsen, Andrew; Peterson, J; Colton, John S; Watt, Richard

    2017-03-23

    This study uses the formation of a mixed metal oxide inside ferritin to tune the band gap energy of the ferritin mineral. The mixed metal oxide is composed of both Co and Mn, and is formed by reacting aqueous Co2+ with MnO4- in the presence of apoferritin. Altering the ratio between the two reactants allowed for controlled tuning of the band gap energies. All minerals formed were indirect band gap materials, with indirect band gap energies ranging from 0.52 to 1.30 eV. The direct transitions were also measured, with energy values ranging from 2.71 to 3.11 eV. Tuning the band gap energies of these samples changes the wavelengths absorbed by each mineral, increasing ferritin's potential in solar-energy harvesting. Additionally, the success of using MnO4- in ferritin mineral formation opens the possibility for new mixed metal oxide cores inside ferritin.

  5. Origami-inspired metamaterial absorbers for improving the larger-incident angle absorption

    NASA Astrophysics Data System (ADS)

    Shen, Yang; Pang, Yongqiang; Wang, Jiafu; Ma, Hua; Pei, Zhibin; Qu, Shaobo

    2015-11-01

    When a folded resistive patch array stands up on a metallic plane, it can exhibit more outstanding absorption performance. Our theoretical investigations and simulations demonstrated that the folded resistive patch arrays can enhance the absorption bandwidth progressively with the increase of the incident angle for the oblique transverse magnetic incidence, which is contrary to the conventional resistive frequency selective surface absorber. On illumination, we achieved a 3D structure metamaterial absorber with the folded resistive patches. The proposed absorber is obtained from the inspiration of the origami, and it has broadband and lager-incident angle absorption. Both the simulations and the measurements indicate that the proposed absorber achieves the larger-incident angle absorption until 75° in the frequency band of 3.6-11.4 GHz. In addition, the absorber is extremely lightweight. The areal density of the fabricated sample is about 0.023 g cm-2. Due to the broadband and lager-incident angle absorption, it is expected that the absorbers may find potential applications such as stealth technologies and electromagnetic interference.

  6. Production of photocurrent due to intermediate-to-conduction-band transitions: a demonstration of a key operating principle of the intermediate-band solar cell.

    PubMed

    Martí, A; Antolín, E; Stanley, C R; Farmer, C D; López, N; Díaz, P; Cánovas, E; Linares, P G; Luque, A

    2006-12-15

    We present intermediate-band solar cells manufactured using quantum dot technology that show for the first time the production of photocurrent when two sub-band-gap energy photons are absorbed simultaneously. One photon produces an optical transition from the intermediate-band to the conduction band while the second pumps an electron from the valence band to the intermediate-band. The detection of this two-photon absorption process is essential to verify the principles of operation of the intermediate-band solar cell. The phenomenon is the cornerstone physical principle that ultimately allows the production of photocurrent in a solar cell by below band gap photon absorption, without degradation of its output voltage.

  7. S-Band Loads for SLAC Linac

    SciTech Connect

    Krasnykh, A.; Decker, F.-J.; LeClair, R.; /INTA Technologies, Santa Clara

    2012-08-28

    The S-Band loads on the current SLAC linac RF system were designed, in some cases, 40+ years ago to terminate 2-3 MW peak power into a thin layer of coated Kanthal material as the high power absorber [1]. The technology of the load design was based on a flame-sprayed Kanthal wire method onto a base material. During SLAC linac upgrades, the 24 MW peak klystrons were replaced by 5045 klystrons with 65+ MW peak output power. Additionally, SLED cavities were introduced and as a result, the peak power in the current RF setup has increased up to 240 MW peak. The problem of reliable RF peak power termination and RF load lifetime required a careful study and adequate solution. Results of our studies and three designs of S-Band RF load for the present SLAC RF linac system is discussed. These designs are based on the use of low conductivity materials.

  8. Attenuation of external Bremsstrahlung in metallic absorbers

    SciTech Connect

    Dhaliwal, A.S.; Powar, M.S.; Singh, M. )

    1990-12-01

    In this paper attenuation of bremsstrahlung from {sup 147}Pm and {sup 170}Tm beta emitters has been studied in aluminum, copper, tin, and lead metallic absorbers. Bremsstrahlung spectra and mass attenuation coefficients for monoenergetic gamma rays are used to calculate theoretical attenuation curves. Magnetic deflection and beta stopping techniques are used to measure the integral bremsstrahlung intensities above 30 keV in different target thicknesses. Comparison of measured and calculated attenuation curves shows a good agreement for various absorbers, thus providing a test of this technique, which may be useful in understanding bremsstrahlung intensity buildup and in the design of optimum shielding for bremsstrahlung sources. It is found that the absorption of bremsstrahlung in metallic absorbers does not obey an exponential law and that absorbers act as energy filters.

  9. 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.

  10. Neutron absorbing coating for nuclear criticality control

    DOEpatents

    Mizia, Ronald E.; Wright, Richard N.; Swank, William D.; Lister, Tedd E.; Pinhero, Patrick J.

    2007-10-23

    A neutron absorbing coating for use on a substrate, and which provides nuclear criticality control is described and which includes a nickel, chromium, molybdenum, and gadolinium alloy having less than about 5% boron, by weight.

  11. Durability of Polymeric Glazing and Absorber Materials

    SciTech Connect

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

    2005-01-01

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

  12. Modular Wideband Active Vibration Absorber

    NASA Technical Reports Server (NTRS)

    Smith, David R.; Zewari, Wahid; Lee, Kenneth Y.

    1999-01-01

    A comparison of space experiments with previous missions shows a common theme. Some of the recent experiments are based on the scientific fundamentals of instruments of prior years. However, the main distinguishing characteristic is the embodiment of advances in engineering and manufacturing in order to extract clearer and sharper images and extend the limits of measurement. One area of importance to future missions is providing vibration free observation platforms at acceptable costs. It has been shown by researchers that vibration problems cannot be eliminated by passive isolation techniques alone. Therefore, various organizations have conducted research in the area of combining active and passive vibration control techniques. The essence of this paper is to present progress in what is believed to be a new concept in this arena. It is based on the notion that if one active element in a vibration transmission path can provide a reasonable vibration attenuation, two active elements in series may provide more control options and better results. The paper presents the functions of a modular split shaft linear actuator developed by NASA's Goddard Space Flight Center and University of Massachusetts Lowell. It discusses some of the control possibilities facilitated by the device. Some preliminary findings and problems are also discussed.

  13. Porous absorber for solar air heaters

    SciTech Connect

    Finch, J.A.

    1980-09-10

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

  14. Multilayer Radar Absorbing Non-Woven Material

    NASA Astrophysics Data System (ADS)

    Dedov, A. V.; Nazarov, V. G.

    2016-06-01

    We study the electrical properties of multilayer radar absorbing materials obtained by adding nonwoven sheets of dielectric fibers with an intermediate layer of electrically conductive carbon fibers. Multilayer materials that absorb electromagnetic radiation in a wide frequency range are obtained by varying the content of the carbon fibers. The carbon-fiber content dependent mechanism of absorption of electromagnetic radiation by sheets and multilayer materials is considered.

  15. Non-absorbed Antibiotics for IBS

    DTIC Science & Technology

    2012-03-16

    absorbed antibiotic rifaximin for nonconstipated irritable bowel syndrome (IBS). This effort adds to the body of literature from other, smaller studies that...have demonstrated clinical efficacy for IBS with rifaximin . Non-absorbed antibiotics have been endorsed by the American College of Gastroenterology... rifaximin 400 mg three times daily for 10 days or placebo. During the initial 2 weeks of therapy and the subsequent 10 weeks of follow-up rifaximin

  16. Structured metal film as a perfect absorber.

    PubMed

    Xiong, Xiang; Jiang, Shang-Chi; Hu, Yu-Hui; Peng, Ru-Wen; Wang, Mu

    2013-08-07

    A new type of absorber, a four-tined fish-spear-like resonator (FFR), constructed by the two-photon polymerization process, is reported. An absorbance of more than 90% is experimentally realized and the resonance occurs in the space between the tines. Since a continuous layer of metallic thin film covers the structure, it is perfectly thermo- and electroconductive, which is the mostly desired feature for many applications.

  17. Developmental Changes in Infants' Sensitivity to Octave-Band Noises.

    ERIC Educational Resources Information Center

    Trehub, Sandra E.; And Others

    1980-01-01

    Localization responses to octave-band noises with center frequencies at 200, 400, 1000, 2000, 4000, and 10,000 Hz were obtained from infants 6, 12, and 18 months old in order to investigate infants' auditory sensitivity. (MP)

  18. VIEW ALONG OHIO AVENUE, LOOKING TOWARD 1905 BAND BARRACKS (BUILDING ...

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

    VIEW ALONG OHIO AVENUE, LOOKING TOWARD 1905 BAND BARRACKS (BUILDING 61 O)CENTER AND FORAGE HOUSE (BUILDING 476)LEFT. VIEW TO NORTHWEST - Plattsburgh Air Force Base, U.S. Route 9, Plattsburgh, Clinton County, NY

  19. Singing with the Band

    ERIC Educational Resources Information Center

    Altman, Timothy Meyer; Wright, Gary K.

    2012-01-01

    Usually band, orchestra, and choir directors work independently. However, the authors--one a choral director, the other a band director--have learned that making music together makes friends. Not only can ensemble directors get along, but joint concerts may be just the way to help students see how music can reach the heart. Combined instrumental…

  20. Rubber Band Science

    ERIC Educational Resources Information Center

    Cowens, John

    2005-01-01

    Not only are rubber bands great for binding objects together, but they can be used in a simple science experiment that involves predicting, problem solving, measuring, graphing, and experimenting. In this article, the author describes how rubber bands can be used to teach the force of mass.

  1. Stretch Band Exercise Program

    ERIC Educational Resources Information Center

    Skirka, Nicholas; Hume, Donald

    2007-01-01

    This article discusses how to use stretch bands for improving total body fitness and quality of life. A stretch band exercise program offers a versatile and inexpensive option to motivate participants to exercise. The authors suggest practical exercises that can be used in physical education to improve or maintain muscular strength and endurance,…

  2. Absorbance changes of carotenoids in different solvents.

    PubMed

    Zang, L Y; Sommerburg, O; van Kuijk, F J

    1997-01-01

    Carotenoids are typically measured in tissues with the high performance liquid chromatography (HPLC) and quantitation is usually done by calibrating with stock solutions in solvents. Four carotenoids including lutein, zeaxanthin, lycopene and beta-carotene were dissolved in hexane and methanol respectively, and their absorbance characteristics were compared. Lutein shows absorbance spectra that are almost independent of solvents at various concentrations. Spectra of zeaxanthin, lycopene and beta-carotene were found to be more solvent-dependent. The absorbance of zeaxanthin at lambda max is about approximately 2 times larger in methanol than in hexane at the higher concentrations, and increased non-linearly with increasing concentration in hexane. The absorbance of lycopene at lambda max in hexane is approximately 4 fold larger than in methanol, but the absorbance of the methanol sample can be recovered by re-extracting this sample in hexane. The absorbance of beta-carotene in hexane is larger than in methanol, and increased linearly with increasing concentration. But beta-carotene showed a non-linear concentration effect in methanol. There are very small variations in lambda max for all four carotenoids between hexane and methanol, due to differences in molar extinction coefficients. The non-linear concentration effects for these carotenoids are probably due to differences in solubility leading to the formation of microcrystals. Thus, care should be taken with quantitation of tissue carotenoid values, when they depend on measurement of concentrations in stock solutions.

  3. Perfect terahertz absorber using fishnet based metafilm

    SciTech Connect

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

    2009-01-01

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

  4. Progressive Band Selection

    NASA Technical Reports Server (NTRS)

    Fisher, Kevin; Chang, Chein-I

    2009-01-01

    Progressive band selection (PBS) reduces spectral redundancy without significant loss of information, thereby reducing hyperspectral image data volume and processing time. Used onboard a spacecraft, it can also reduce image downlink time. PBS prioritizes an image's spectral bands according to priority scores that measure their significance to a specific application. Then it uses one of three methods to select an appropriate number of the most useful bands. Key challenges for PBS include selecting an appropriate criterion to generate band priority scores, and determining how many bands should be retained in the reduced image. The image's Virtual Dimensionality (VD), once computed, is a reasonable estimate of the latter. We describe the major design details of PBS and test PBS in a land classification experiment.

  5. Simultaneous Analysis of the 2nu2, nu1, and nu3 Bands of Hydrogen Telluride

    PubMed

    Flaud; Betrencourt; Arcas; Burger; Polanz; Lafferty

    1997-04-01

    Spectra of a natural sample of hydrogen telluride as well as a spectrum of monoisotopic H2 130Te have been recorded by means of Fourier transform spectrometry with a resolution of 0.003 cm-1 in the spectral domain 7.5-4.3 μm where it is easy to observe the main absorbing bands nu1 and nu3. We have located and assigned for the first time the 2nu2 band which appears in the lower wavenumber range of the recorded spectral domain near 1700 cm-1. It proved necessary to treat simultaneously the three states (020), (100), and (001). nu1 and nu3 are indeed Coriolis-coupled vibration-rotation bands and it was observed that a few rotational levels of (001) could not be fitted to within their experimental accuracy without considering the second-order Coriolis interaction between the rotational levels of (020) and (001). In this way all the experimental levels were calculated to within the experimental uncertainty, and precise sets of vibrational energies and rotational and coupling constants were obtained for the seven most abundant H2Te isotopic species, namely H2 130Te, H2 128Te, H2 126Te, H2 125Te, H2 124Te, H2 123Te, and H2 122Te. For the most abundant isotopic species H2 130Te the bands centers arenu0 (2nu2) = 1715.9568, nu0 (nu1) = 2065.2709, nu0 (nu3) = 2072.1101 cm-1. Copyright 1997Academic Press

  6. Radiative transfer effects on reflected shock waves. II - Absorbing gas.

    NASA Technical Reports Server (NTRS)

    Su, F. Y.; Olfe, D. B.

    1972-01-01

    Radiative cooling effects behind a reflected shock wave are calculated for an absorbing-emitting gas by means of an expansion procedure in the small density ratio across the shock front. For a gray gas shock layer with an optical thickness of order unity or less the absorption integral is simplified by use of the local temperature approximation, whereas for larger optical thicknesses a Rosseland diffusion type of solution is matched with the local temperature approximation solution. The calculations show that the shock wave will attenuate at first and then accelerate to a constant velocity. Under appropriate conditions the gas enthalpy near the wall may increase at intermediate times before ultimately decreasing to zero. A two-band absorption model yields end-wall radiant-heat fluxes which agree well with available shock-tube measurements.

  7. A multiband perfect absorber based on hyperbolic metamaterials

    PubMed Central

    Sreekanth, Kandammathe Valiyaveedu; ElKabbash, Mohamed; Alapan, Yunus; Rashed, Alireza R.; Gurkan, Umut A.; Strangi, Giuseppe

    2016-01-01

    In recent years, considerable research efforts have been focused on near-perfect and perfect light absorption using metamaterials spanning frequency ranges from microwaves to visible frequencies. This relatively young field is currently facing many challenges that hampers its possible practical applications. In this paper, we present grating coupled-hyperbolic metamaterials (GC-HMM) as multiband perfect absorber that can offer extremely high flexibility in engineering the properties of electromagnetic absorption. The fabricated GC-HMMs exhibit several highly desirable features for technological applications such as polarization independence, wide angle range, broad- and narrow- band modes, multiband perfect and near perfect absorption in the visible to near-IR and mid-IR spectral range. In addition, we report a direct application of the presented system as an absorption based plasmonic sensor with a record figure of merit for this class of sensors. PMID:27188789

  8. Ultra-broadband microwave metamaterial absorber based on resistive sheets

    NASA Astrophysics Data System (ADS)

    Kim, Y. J.; Yoo, Y. J.; Hwang, J. S.; Lee, Y. P.

    2017-01-01

    We investigate a broadband perfect absorber for microwave frequencies, with a wide incident angle, using resistive sheets, based on both simulation and experiment. The absorber uses periodically-arranged meta-atoms, consisting of snake-shape metallic patterns and metal planes separated by three resistive sheet layers between four dielectric layers. We demonstrate the mechanism of the broadband by impedance matching with free space, and the distribution of surface currents at specific frequencies. In simulation, the absorption was over 96% in 1.4-6.0 GHz. The corresponding experimental absorption band over 96% was 1.4-4.0 GHz, however, the absorption was lower than 96% in the 4.0-6.0 GHz range because of the rather irregular thickness of the resistive sheets. Furthermore, it works for wide incident angles and is relatively independent of polarization. The design is scalable to smaller sizes in the THz range. The results of this study show potential for real applications in prevention of microwave frequency exposure, with devices such as cell phones, monitors, and microwave equipment.

  9. Research on Community Bands: Past, Present, and Future

    ERIC Educational Resources Information Center

    Rohwer, Debbie

    2016-01-01

    The purpose of this review of literature was to synthesize findings of studies investigating community bands. This review of literature centers on research that has been conducted on community bands in status studies, historical/cultural studies, pedagogical studies, health and wellness studies, and intergenerational studies. The last section of…

  10. The Collaborative Rehearsal: Blogging as a Reflective Paradigm for Band

    ERIC Educational Resources Information Center

    Brown, Daniel James

    2012-01-01

    This study explores the potential for the band rehearsal setting to be a reflectively collaborative space. School bands are traditionally large, performance-centered ensembles where discussions between director and student are limited by time and the size of the group. Recognizing the need to base rehearsals less on the conductor's…

  11. Synchrotron-based rotationally resolved high-resolution FTIR spectroscopy of azulene and the unidentified infrared bands of astronomy.

    PubMed

    Albert, Sieghard; Lerch, Philippe; Quack, Martin

    2013-10-07

    Chasing the unidentified IR bands: The first rotationally resolved high-resolution infrared spectrum of azulene is reported using synchrotron Fourier transform infrared spectroscopy including a rovibrational analysis of the out-of-plane fundamental ν44. Comparison of azulene, naphthalene, indole, and biphenyl infrared bands leads to coincidences with UIR bands at 12.8 μm with naphthalene and at 13.55 and 14.6 μm with biphenyl bands, but excluding azulene as a strong absorber.

  12. Increasing efficiency in intermediate band solar cells with overlapping absorptions

    NASA Astrophysics Data System (ADS)

    Krishna, Akshay; Krich, Jacob J.

    2016-07-01

    Intermediate band (IB) materials are promising candidates for realizing high efficiency solar cells. In IB photovoltaics, photons are absorbed in one of three possible electronic transitions—valence to conduction band, valence to intermediate band, or intermediate to conduction band. With fully concentrated sunlight, when the band gaps have been chosen appropriately, the highest efficiency IB solar cells require that these three absorptions be non-overlapping, so absorbed photons of fixed energy contribute to only one transition. The realistic case of overlapping absorptions, where the transitions compete for photons, is generally considered to be a source of loss. We show that overlapping absorptions can in fact lead to significant improvements in IB solar cell efficiencies, especially for IB that are near the middle of the band gap. At low to moderate concentration, the highest efficiency requires overlapping absorptions. We use the detailed-balance method and indicate how much overlap of the absorptions is required to achieve efficiency improvements, comparing with some known cases. These results substantially broaden the set of materials that can be suitable for high-efficiency IB solar cells.

  13. Polycyclic aromatic hydrocarbon ions and the diffuse interstellar bands

    NASA Technical Reports Server (NTRS)

    Salama, F.; Allamandola, L. J.

    1995-01-01

    Neutral naphthalene (C10H8), phenanthrene (C14H10), and pyrene (C16H10) absorb strongly in the ultraviolet and may contribute to the extinction curve. High abundances are required to produce detectable structures. The cations of these Polycyclic Aromatic Hydrocarbons (PAHs) absorb in the visible. C10H8(+) has 12 discrete absorption bands which fall between 6800 and 5000 A. The strongest band at 6741 A falls close to the weak 6742 A diffuse interstellar band (DIB). Five other weaker bands also match DIBs. The possibility that C10H8(+) is responsible for some of the DIBs can be tested by searching for new DIBS at 6520, 6151, and 5965 A, other moderately strong naphthalene cation band positions. If C10H8(+) is indeed responsible for the 6742 A feature, it accounts for 0.3% of the cosmic carbon. The spectrum of C16H10(+) is dominated by a strong band at 4435 A in an Ar matrix and 4395 A in a Ne matrix, a position which falls very close to the strongest DIB, that at 4430 A. If C16H10(+), or a closely related pyrene-like ion is indeed responsible for the 4430 A feature, it accounts for 0.2% of the cosmic carbon. We also report an intense, very broad UV-to-visible continuum which is associated with both ions and could explain how PAHs convert interstellar UV and visible radiation into IR.

  14. High-performance terahertz wave absorbers made of silicon-based metamaterials

    SciTech Connect

    Yin, Sheng; Zhu, Jianfei; Jiang, Wei; Yuan, Jun; Yin, Ge; Ma, Yungui; Xu, Wendao; Xie, Lijuan; Ying, Yibin

    2015-08-17

    Electromagnetic (EM) wave absorbers with high efficiency in different frequency bands have been extensively investigated for various applications. In this paper, we propose an ultra-broadband and polarization-insensitive terahertz metamaterial absorber based on a patterned lossy silicon substrate. Experimentally, a large absorption efficiency more than 95% in a frequency range of 0.9–2.5 THz was obtained up to a wave incident angle as large as 70°. Much broader absorption bandwidth and excellent oblique incidence absorption performance are numerically demonstrated. The underlying mechanisms due to the combination of a waveguide cavity mode and impedance-matched diffraction are analyzed in terms of the field patterns and the scattering features. The monolithic THz absorber proposed here may find important applications in EM energy harvesting systems such as THz barometer or biosensor.

  15. Broad-band frequency references in the near-infrared: Accurate dual comb spectroscopy of methane and acetylene

    NASA Astrophysics Data System (ADS)

    Zolot, A. M.; Giorgetta, F. R.; Baumann, E.; Swann, W. C.; Coddington, I.; Newbury, N. R.

    2013-03-01

    The Doppler-limited spectra of methane between 176 THz and 184 THz (5870-6130 cm-1) and acetylene between 193 THz and 199 THz (6430-6630 cm-1) are acquired via comb-tooth resolved dual comb spectroscopy with frequency accuracy traceable to atomic standards. A least squares analysis of the measured absorbance and phase line shapes provides line center frequencies with absolute accuracy of 0.2 MHz, or less than one thousandth of the room temperature Doppler width. This accuracy is verified through comparison with previous saturated absorption spectroscopy of 37 strong isolated lines of acetylene. For the methane spectrum, the center frequencies of 46 well-isolated strong lines are determined with similar high accuracy, along with the center frequencies for 1107 non-isolated lines at lower accuracy. The measured methane line-center frequencies have an uncertainty comparable to the few available laser heterodyne measurements in this region but span a much larger optical bandwidth, marking the first broad-band measurements of the methane 2ν3 region directly referenced to atomic frequency standards. This study demonstrates the promise of dual comb spectroscopy to obtain high resolution broadband spectra that are comparable to state-of-the-art Fourier-transform spectrometer measurements but with much improved frequency accuracy.Work of the US government, not subject to US copyright.

  16. Method of absorbance correction in a spectroscopic heating value sensor

    SciTech Connect

    Saveliev, Alexei; Jangale, Vilas Vyankatrao; Zelepouga, Sergeui; Pratapas, John

    2013-09-17

    A method and apparatus for absorbance correction in a spectroscopic heating value sensor in which a reference light intensity measurement is made on a non-absorbing reference fluid, a light intensity measurement is made on a sample fluid, and a measured light absorbance of the sample fluid is determined. A corrective light intensity measurement at a non-absorbing wavelength of the sample fluid is made on the sample fluid from which an absorbance correction factor is determined. The absorbance correction factor is then applied to the measured light absorbance of the sample fluid to arrive at a true or accurate absorbance for the sample fluid.

  17. New absorbed dose measurement with cylindrical water phantoms for multidetector CT

    NASA Astrophysics Data System (ADS)

    Ohno, Takeshi; Araki, Fujio; Onizuka, Ryota; Hioki, Kazunari; Tomiyama, Yuuki; Yamashita, Yusuke

    2015-06-01

    The aim of this study was to develop new dosimetry with cylindrical water phantoms for multidetector computed tomography (MDCT). The ionization measurement was performed with a Farmer ionization chamber at the center and four peripheral points in the body-type and head-type cylindrical water phantoms. The ionization was converted to the absorbed dose using a 60Co absorbed-dose-to-water calibration factor and Monte Carlo (MC) -calculated correction factors. The correction factors were calculated from MDCT (Brilliance iCT, 64-slice, Philips Electronics) modeled with GMctdospp (IMPS, Germany) software based on the EGSnrc MC code. The spectrum of incident x-ray beams and the configuration of a bowtie filter for MDCT were determined so that calculated photon intensity attenuation curves for aluminum (Al) and calculated off-center ratio (OCR) profiles in air coincided with those measured. The MC-calculated doses were calibrated by the absorbed dose measured at the center in both cylindrical water phantoms. Calculated doses were compared with measured doses at four peripheral points and the center in the phantom for various beam pitches and beam collimations. The calibration factors and the uncertainty of the absorbed dose determined using this method were also compared with those obtained by CTDIair (CT dose index in air). Calculated Al half-value layers and OCRs in air were within 0.3% and 3% agreement with the measured values, respectively. Calculated doses at four peripheral points and the centers for various beam pitches and beam collimations were within 5% and 2% agreement with measured values, respectively. The MC-calibration factors by our method were 44-50% lower than values by CTDIair due to the overbeaming effect. However, the calibration factors for CTDIair agreed within 5% with those of our method after correction for the overbeaming effect. Our method makes it possible to directly measure the absorbed dose for MDCT and is more robust and accurate than the

  18. Iliotibial band friction syndrome

    PubMed Central

    2010-01-01

    Published articles on iliotibial band friction syndrome have been reviewed. These articles cover the epidemiology, etiology, anatomy, pathology, prevention, and treatment of the condition. This article describes (1) the various etiological models that have been proposed to explain iliotibial band friction syndrome; (2) some of the imaging methods, research studies, and clinical experiences that support or call into question these various models; (3) commonly proposed treatment methods for iliotibial band friction syndrome; and (4) the rationale behind these methods and the clinical outcome studies that support their efficacy. PMID:21063495

  19. Redshift--Independent Distances of Spiral Galaxies: II. Internal Extinction at I Band

    NASA Astrophysics Data System (ADS)

    Giovanelli, R.; Haynes, M. P.; Salzer, J. J.; Wegner, G.; Dacosta, L. N.; Freudling, W.; Chamaraux, P.

    1993-12-01

    We analyze the photometric properties of a sample of 1450 Sbc--Sc galaxies with known redshifts, single--dish HI profiles and CCD I band images to derive laws that relate the measured isophotal radius at mu_I =23.5, magnitude, scale length and HI flux to the face--on aspect. Our results show that the central regions of spiral galaxies are substantially less transparent than most previous determinations suggest, but not as opaque as claimed by Valentijn (1990). Regions in the disk farther than two or three scale lengths from the center are close to completely transparent. In addition to statistically derived relations for the inclination dependence of photometric parameters, we present the results of a modelling exercise that utilizes the ``triplex'' model of Disney et al. (1989). Within the framework of that model, late spiral disks at I band have central optical depths on the order of tau_I ~ 5 and dust absorbing layers with scale heights on the order of half that of the stellar component. We discuss our results in light of previous determinations of internal extinction relations and point out the substantial impact of internal extinction on the scatter of the Tully--Fisher relation. We also find that the visual diameters by which large catalogs are constructed (UGC, ESO--Uppsala) are nearly proportional to face--on isophotal diameters.

  20. A fully functionalized metamaterial perfect absorber with simple design and implementation

    PubMed Central

    Fu, Sze Ming; Zhong, Yan Kai; Tu, Ming Hsiang; Chen, Bo Ruei; Lin, Albert

    2016-01-01

    Broadband perfect metamaterial absorbers have been drawing significant attention in recent years. A close-to-unity absorption over a broad spectral range is established and this facilitates many photonic applications. A more challenging goal is to construct a broadband absorber with a tailored spectral absorption. The spectral absorption control and spectral shaping are very critical in many applications, such as thermal-photovoltaic, thermal emitters, spectrum imaging system, biomedical and extraterrestrial sensing, and refractive index sensor. In this work, one-dimensional (1D) planar stacking structure is designed to achieve the ultimate goal of a functionalized absorber with a fully tailorable spectral absorption. The lithography and etching process are totally eliminated in this proposed structure, and the fabrication is fully compatible with the regular silicon IC processing. By using ~2 nm ultra-thin metallic layers with a 10-pair (10X) SiO2/Si3N4 integrated dielectric filter, we can achieve decent spectral response shaping. The planar configuration of the ultra-thin-metal metamaterial perfect absorber (MPA) is the key to the easy design/integration of the dielectric filters on top of the MPA. Specifically, band-rejected, high-pass, low-pass and band-pass structure are constructed successfully. Finally, experimental evidence to support our simulation result is also provided, which proves the feasibility of our proposal. PMID:27782181

  1. A fully functionalized metamaterial perfect absorber with simple design and implementation

    NASA Astrophysics Data System (ADS)

    Fu, Sze Ming; Zhong, Yan Kai; Tu, Ming Hsiang; Chen, Bo Ruei; Lin, Albert

    2016-10-01

    Broadband perfect metamaterial absorbers have been drawing significant attention in recent years. A close-to-unity absorption over a broad spectral range is established and this facilitates many photonic applications. A more challenging goal is to construct a broadband absorber with a tailored spectral absorption. The spectral absorption control and spectral shaping are very critical in many applications, such as thermal-photovoltaic, thermal emitters, spectrum imaging system, biomedical and extraterrestrial sensing, and refractive index sensor. In this work, one-dimensional (1D) planar stacking structure is designed to achieve the ultimate goal of a functionalized absorber with a fully tailorable spectral absorption. The lithography and etching process are totally eliminated in this proposed structure, and the fabrication is fully compatible with the regular silicon IC processing. By using ~2 nm ultra-thin metallic layers with a 10-pair (10X) SiO2/Si3N4 integrated dielectric filter, we can achieve decent spectral response shaping. The planar configuration of the ultra-thin-metal metamaterial perfect absorber (MPA) is the key to the easy design/integration of the dielectric filters on top of the MPA. Specifically, band-rejected, high-pass, low-pass and band-pass structure are constructed successfully. Finally, experimental evidence to support our simulation result is also provided, which proves the feasibility of our proposal.

  2. Integration of an interferometric IR absorber into an epoxy membrane based CO2 detector

    NASA Astrophysics Data System (ADS)

    Ashraf, S.; Mattsson, C. G.; Thungström, G.; Rödjegård, H.

    2014-05-01

    Measurements of carbon dioxide levels in the environment are commonly performed by using non-dispersive infrared technology (NDIR). Thermopile detectors are often used in NDIR systems because of their non-cooling advantages. The infrared absorber has a major influence on the detector responsivity. In this paper, the fabrication of a SU-8 epoxy membrane based Al/Bi thermopile detector and the integration of an interferometric infrared absorber structure of wavelength around 4 μm into the detector is reported. The membrane of thermopile detector has been utilized as a dielectric medium in an interferometric absorption structure. By doing so, a reduction in both thermal conductance and capacitance is achieved. In the fabrication of the thermopile, metal evaporation and lift off process had been used for the deposition of serially interconnected Al/Bi thermocouples. Serial resistance of fabricated thermopile was measured as 220 kΩ. The response of fabricated thermopile detector was measured using a visible to infrared source of radiation flux 3.23 mW mm-2. The radiation incident on the detector was limited using a band pass filter of wavelength 4.26 μm in front of the detector. A responsivity of 27.86 V mm2 W-1 at room temperature was achieved using this setup. The fabricated detector was compared to a reference detector with a broad band absorber. From the comparison it was concluded that the integrated interferometric absorber is functioning correctly.

  3. Magneto-optical reflectance and absorbance of PbS quantum dots

    NASA Astrophysics Data System (ADS)

    Barik, Puspendu; Singh, Akhilesh K.; Ullrich, Bruno

    2015-09-01

    Reflectance and absorbance of colloidal 2.5 nm PbS quantum dots were coincidentally measured under the presence of moderate magnetic fields below one Tesla. The work provides further insight to the optical and magneto-optical properties of quantum dots by revealing disconnect of band gap data collected in different experimental geometries and by the demonstration of reflective magneto-optical devices addressable with weak magnetic fields.

  4. Water absorbency by wool fibers: Hofmeister effect.

    PubMed

    Lo Nostro, Pierandrea; Fratoni, Laura; Ninham, Barry W; Baglioni, Piero

    2002-01-01

    Wool is a complex material, composed of cuticle and epicuticle cells, surrounded by a cell membrane complex. Wool fibers absorb moisture from air, and, once immersed in water, they take up considerable amounts of liquid. The water absorbency parameter can be determined from weight gain, according to a standard method, and used to quantify this phenomenon. In this paper we report a study on the water absorbency (or retention) of untreated wool fibers in the presence of aqueous 1 M salt solutions at 29 degrees C and a relative humidity of either 33% or 56%. The effect of anions was determined by selecting a wide range of different sodium salts, while the effect of cations was checked through some chlorides and nitrates. Our results show a significant specific ion and ion pair "Hofmeister" effects, that change the amount of water absorbed by the fibers. To understand this phenomenon, the water absorbency parameter (A(w)) is compared to different physicochemical parameters such as the lyotropic number, free energy of hydration of ions, molar surface tension increment, polarizability, refractive index increment, and molar refractivity. The data indicate that this Hofmeister phenomenon is controlled by dispersion forces that depend on the polarizability of ionic species, their adsorption frequencies, the solvent, and the substrate. These dispersion forces dominate the behavior in concentrated solutions. They are in accord with new developing theories of solutions and molecular interactions in colloidal systems that account for Hofmeister effects.

  5. Oxygen absorbers in food preservation: a review.

    PubMed

    Cichello, Simon Angelo

    2015-04-01

    The preservation of packaged food against oxidative degradation is essential to establish and improve food shelf life, customer acceptability, and increase food security. Oxygen absorbers have an important role in the removal of dissolved oxygen, preserving the colour, texture and aroma of different food products, and importantly inhibition of food spoilage microbes. Active packaging technology in food preservation has improved over decades mostly due to the sealing of foods in oxygen impermeable package material and the quality of oxygen absorber. Ferrous iron oxides are the most reliable and commonly used oxygen absorbers within the food industry. Oxygen absorbers have been transformed from sachets of dried iron-powder to simple self-adhesive patches to accommodate any custom size, capacity and application. Oxygen concentration can be effectively lowered to 100 ppm, with applications spanning a wide range of food products and beverages across the world (i.e. bread, meat, fish, fruit, and cheese). Newer molecules that preserve packaged food materials from all forms of degradation are being developed, however oxygen absorbers remain a staple product for the preservation of food and pharmaceutical products to reduce food wastage in developed nations and increased food security in the developing & third world.

  6. CSF oligoclonal banding

    MedlinePlus

    ... system. Oligoclonal bands may be a sign of multiple sclerosis. How the Test is Performed A sample of ... Performed This test helps support the diagnosis of multiple sclerosis (MS). However, it does not confirm the diagnosis. ...

  7. Decay of superdeformed bands

    SciTech Connect

    Carpenter, M.P.; Khoo, T.L.; Lauritsen, T.

    1995-12-31

    One of the major challenges in the study of superdeformation is to directly connect the large number of superdeformed bands now known to the yrast states. In this way, excitation energies, spins and parities can be assigned to the levels in the second well which is essential to establish the collective and single-particle components of these bands. This paper will review some of the progress which has been made to understand the decay of superdeformed bands using the new arrays including the measurement of the total decay spectrum and the establishment of direct one-step decays from the superdeformed band to the yrast line in {sup 194}Hg. 42 refs., 5 figs.

  8. Polygonal deformation bands

    NASA Astrophysics Data System (ADS)

    Antonellini, Marco; Mollema, Pauline Nella

    2015-12-01

    We report for the first time the occurrence of polygonal faults in sandstone, which is compelling given that layer-bound polygonal fault systems have been observed so far only in fine-grained sediments such as clay and chalk. The polygonal faults are shear deformation bands that developed under shallow burial conditions via strain hardening in dm-wide zones. The edges of the polygons are 1-5 m long. The shear deformation bands are organized as conjugate faults along each edge of the polygon and form characteristic horst-like structures. The individual deformation bands have slip magnitudes ranging from a few mm to 1.5 cm; the cumulative average slip magnitude in a zone is up to 10 cm. The deformation bands heaves, in aggregate form, accommodate a small isotropic horizontal extension (strain <0.005). The individual shear deformation bands show abutting T-junctions, veering, curving, and merging where they mechanically interact. Crosscutting relationships are rare. The interactions of the deformation bands are similar to those of mode I opening fractures. The documented fault networks have important implications for evaluating the geometry of km-scale polygonal fault systems in the subsurface, top seal integrity, as well as constraining paleo-tectonic stress regimes.

  9. Non-Absorbable Gas Behavior in the Absorber/Evaporator of a Absorption Chiller

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroshi; Nagamoto, Wataru; Sugiyama, Takahide

    A two-dimensional numerical study on non-absorbable gas behavior in the absorber/evaporator of an absorption chiller has been performed. In the present study, the effect of the pitch-to-diameter ratio of a cylinder bundle in the absorber was highlighted. From the results, a sudden decrease of the overall heat transfer coefficient of the absorber was observed at a certain mean concentration of non-absorbable gas for each pitch-to-diameter ratio. Such a critical concentration was also found to decrease as the pitch-to- diameter ratio increased. The sudden decrease occurs due to the sudden disappearance of recirculating region, which is formed between the absorber and the evaporator, and where most of non-absorbable gas stays when it exists. As the pitch-to-diameter ratio increases, the recirculating region becomes weak because the velocity of the high velocity region supporting the recirculating flow decreases. Then, the critical mean concentration of non-absorbable gas is found to decrease as pitch-to-ratio increases.

  10. K-band Polarimetry of NGC 891

    NASA Astrophysics Data System (ADS)

    Montgomery, Jordan; Clemens, Dan P.

    2014-06-01

    We present the first K-band (2.2 um) polarimetry observations of the edge-on galaxy NGC 891. Near-infrared (NIR) polarimetry reveals the plane-of-sky projected magnetic (B) field orientations in dusty, star-forming interstellar media. Previous optical wavelength polarimetry of NGC 891 found predominantly disk-perpendicular polarizations (Scarrott & Draper 1996) while H-band polarimetry revealed mostly disk-parallel polarizations with an interesting 15 degree offset from the major axis position angle (Jones 1997; Montgomery & Clemens 2014). In H-band, Montgomery & Clemens also detected the first NIR polarization null-point, located about 5 kpc northeast of NGC891's center. It may be related to the polarization null-points predicted by Wood (1997) and modeled by Wood & Jones (1997). At the longer K-band wavelength, these new observations better reveal B-field orientation changes in the disk. The Wood (1997) radiative transfer polarization model predicted null-point location changes with wavelengeth. We will use the new K-band polarimetry, along with our H-band polarimetry, to test this prediction. If the null-point location does not depend on wavelength, then the null-point may instead be due to spiral arm aligned B-fields (e.g., Fletcher et al. 2011).This research was supported through NSF grant AST 09-07790.

  11. Optical analysis of solar energy tubular absorbers.

    PubMed

    Saltiel, C; Sokolov, M

    1982-11-15

    The energy absorbed by a solar energy tubular receiver element for a single incident ray is derived. Two types of receiver elements were analyzed: (1) an inner tube with an absorbing coating surrounded by a semitransparent cover tube, and (2) a semitransparent inner tube filled with an absorbing fluid surrounded by a semitransparent cover tube. The formation of ray cascades in the semitransparent tubes is considered. A numerical simulation to investigate the influence of the angle of incidence, sizing, thickness, and coefficient of extinction of the tubes was performed. A comparison was made between receiver elements with and without cover tubes. Ray tracing analyses in which rays were followed within the tubular receiver element as well as throughout the rest of the collector were performed for parabolic and circular trough concentrating collectors.

  12. Interference theory of metamaterial perfect absorbers.

    PubMed

    Chen, Hou-Tong

    2012-03-26

    The impedance matching to free space in metamaterial perfect absorbers has been believed to involve and rely on magnetic resonant response, with direct evidence provided by the anti-parallel surface currents in the metal structures. Here I present a different theoretical interpretation based on interference, which shows that the two layers of metal structures in metamaterial absorbers are linked only by multiple reflections with negligible near-field interactions or magnetic resonances. This is further supported by the out-of-phase surface currents derived at the interfaces of resonator array and ground plane through multiple reflections and superpositions. The theory developed here explains all features observed in narrowband metamaterial absorbers and therefore provides a profound understanding of the underlying physics.

  13. 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.

  14. Absorber Materials at Room and Cryogenic Temperatures

    SciTech Connect

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

    2011-09-01

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

  15. Ferrite HOM Absorber for the RHIC ERL

    SciTech Connect

    Hahn,H.; Choi, E.M.; Hammons, L.

    2008-10-01

    A superconducting Energy Recovery Linac is under construction at Brookhaven National Laboratory to serve as test bed for RHIC upgrades. The damping of higher-order modes in the superconducting five-cell cavity for the Energy-Recovery linac at RHIC is performed exclusively by two ferrite absorbers. The ferrite properties have been measured in ferrite-loaded pill box cavities resulting in the permeability values given by a first-order Debye model for the tiled absorber structure and an equivalent permeability value for computer simulations with solid ring dampers. Measured and simulated results for the higher-order modes in the prototype copper cavity are discussed. First room-temperature measurements of the finished niobium cavity are presented which confirm the effective damping of higher-order modes in the ERL. by the ferrite absorbers.

  16. Photonic band gap structure simulator

    DOEpatents

    Chen, Chiping; Shapiro, Michael A.; Smirnova, Evgenya I.; Temkin, Richard J.; Sirigiri, Jagadishwar R.

    2006-10-03

    A system and method for designing photonic band gap structures. The system and method provide a user with the capability to produce a model of a two-dimensional array of conductors corresponding to a unit cell. The model involves a linear equation. Boundary conditions representative of conditions at the boundary of the unit cell are applied to a solution of the Helmholtz equation defined for the unit cell. The linear equation can be approximated by a Hermitian matrix. An eigenvalue of the Helmholtz equation is calculated. One computation approach involves calculating finite differences. The model can include a symmetry element, such as a center of inversion, a rotation axis, and a mirror plane. A graphical user interface is provided for the user's convenience. A display is provided to display to a user the calculated eigenvalue, corresponding to a photonic energy level in the Brilloin zone of the unit cell.

  17. Polarization-insensitive wide-angle multiband metamaterial absorber with a double-layer modified electric ring resonator array

    NASA Astrophysics Data System (ADS)

    Li, Wangchang; Zhou, Xiang; Ying, Yao; Qiao, Xiaojing; Qin, Faxiang; Li, Qian; Che, Shenglei

    2015-06-01

    In this letter, we report the design, demonstration and discussion of a multi- and broad- band metamaterial absorber (MMA) with wide angle polarization insensitive at microwave region. The MMA consisting of double layered electric ring resonator (ERR) with four fold rotational symmetry structure is used to realize a desirable absorption. Strong triple absorption peaks in 2˜8 GHz and broadband microwave absorption in 10˜18 GHz are demonstrated. The absorption can be reached as high as 0.73, 0.73 and 0.94 at 4.41, 5.15, 6.37 GHz, respectively. The multiband absorbing features originate from the synergetic effects of dipole resonance and Fabry-Pérot interference between two or three metasurfaces. This design is of high practical for constructing broad band and multiband absorber for electromagnetic intereference/compatibility (EMI/EMC) applications.

  18. Absorber topography dependence of phase edge effects

    NASA Astrophysics Data System (ADS)

    Shanker, Aamod; Sczyrba, Martin; Connolly, Brid; Waller, Laura; Neureuther, Andy

    2015-10-01

    Mask topography contributes to phase at the wafer plane, even for OMOG binary masks currently in use at the 22nm node in deep UV (193nm) lithography. Here, numerical experiments with rigorous FDTD simulation are used to study the impact of mask 3D effects on aerial imaging, by varying the height of the absorber stack and its sidewall angle. Using a thin mask boundary layer model to fit to rigorous simulations it is seen that increasing the absorber thickness, and hence the phase through the middle of a feature (bulk phase) monotonically changes the wafer-plane phase. Absorber height also influences best focus, revealed by an up/down shift in the Bossung plot (linewidth vs. defocus). Bossung plot tilt, however, responsible for process window variability at the wafer, is insensitive to changes in the absorber height (and hence also the bulk phase). It is seen to depend instead on EM edge diffraction from the thick mask edge (edge phase), but stays constant for variations in mask thickness within a 10% range. Both bulk phase and edge phase are also independent of sidewall angle fluctuation, which is seen to linearly affect the CD at the wafer, but does not alter wafer phase or the defocus process window. Notably, as mask topography varies, the effect of edge phase can be replicated by a thin mask model with 8nm wide boundary layers, irrespective of absorber height or sidewall angle. The conclusions are validated with measurements on phase shifting masks having different topographic parameters, confirming the strong dependence of phase variations at the wafer on bulk phase of the mask absorber.

  19. Quantum walk with one variable absorbing boundary

    NASA Astrophysics Data System (ADS)

    Wang, Feiran; Zhang, Pei; Wang, Yunlong; Liu, Ruifeng; Gao, Hong; Li, Fuli

    2017-01-01

    Quantum walks constitute a promising ingredient in the research on quantum algorithms; consequently, exploring different types of quantum walks is of great significance for quantum information and quantum computation. In this study, we investigate the progress of quantum walks with a variable absorbing boundary and provide an analytical solution for the escape probability (the probability of a walker that is not absorbed by the boundary). We simulate the behavior of escape probability under different conditions, including the reflection coefficient, boundary location, and initial state. Moreover, it is also meaningful to extend our research to the situation of continuous-time and high-dimensional quantum walks.

  20. OSCEE fan exhaust bulk absorber treatment evaluation

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  1. Analysis of Energy-Absorbing Foundations.

    DTIC Science & Technology

    1978-12-15

    1ENN51YVAN&A 5TATL UNIV UNIVERSITY PARK DEPT OF ENGI-CYTC F/S 13/h ANALYSIS OF ENERGY -ABSORBING POUNDATIONS.(U) ECC 78 V H NEUBERT, S Ji YIN DNA01-78...C-0036 UNCLASSIFIED DNA-48OFP NL "M~ENOMOEE MIflfl END ______ 1 32 112.2 MICROCOPY RILSOLUTION TEST CHIART LELL ,NA 480 MIL ANALYSIS OF ENERGY ...8217 REPORT & PERIOD COVERED Final Report for Period ANALYSIS OF ENERGY -ABSORBING FOUNDATIONS I Dee 77-1S Dee 78 6. PERFORMING ORG, REPORT NUMBER 7AUTHOR

  2. Shock-Absorbent Ball-Screw Mechanism

    NASA Technical Reports Server (NTRS)

    Hirr, Otto A., Jr.; Meneely, R. W.

    1986-01-01

    Actuator containing two ball screws in series employs Belleville springs to reduce impact loads, thereby increasing life expectancy. New application of springs increases reliability of equipment in which ball screws commonly used. Set of three springs within lower screw of ball-screw mechanism absorbs impacts that result when parts reach their upper and lower limits of movement. Mechanism designed with Belleville springs as shock-absorbing elements because springs have good energy-to-volume ratio and easily stacked to attain any stiffness and travel.

  3. Radio-Absorbing Nanocoatings on Corrugated Surfaces

    NASA Astrophysics Data System (ADS)

    Antipov, V. B.; Potekaev, A. I.; Vorozhtsov, A. B.; Melentyev, S. V.; Tsyganok, Yu. I.

    2016-12-01

    The feasibility of producing protective radio-absorbing shielding materials on the basis of differently shaped surfaces with nanostructured coatings is investigated. Combinations of special nanostructured materials and technical solutions for the shape of the absorbing surface were tested, in order to create efficient nanocoatings. It is shown that the coatings of interest that meet the requirements of low reflection and high attenuation of transmitted radiation combined with low coating thickness can be developed, using corrugated surfaces. Corrugated chicken egg-packing cell samples with nanostructured carbon coatings were examined and found to allow for effective shielding of electromagnetic radiation and to exhibit minimum reflection coefficients as compared to construction materials.

  4. Timing the warm absorber in NGC 4051

    NASA Astrophysics Data System (ADS)

    Silva, C. V.; Uttley, P.; Costantini, E.

    2016-12-01

    We investigated, using spectral-timing analysis, the characterization of highly ionized outflows in Seyfert galaxies, the so-called warm absorbers. Here, we present our results of the extensive 600 ks of XMM-Newton archival observations of the bright and highly variable Seyfert 1 galaxy NGC 4051 whose spectrum has revealed a complex multicomponent wind. Making use of both RGS and EPIC-pn data, we performed a detailed analysis through a time-dependent photoionization code in combination with spectral and Fourier spectral-timing techniques. The source light curves and the warm absorber parameters obtained from the data were used to simulate the response of the gas to variations in the ionizing flux of the central source. The resulting time variable spectra were employed to predict the effects of the warm absorber on the time lags and coherence of the energy dependent light curves. We have found that, in the absence of any other lag mechanisms, a warm absorber with the characteristics of the one observed in NGC 4051, is able to produce soft lags, up to 100 s, on timescales of hours. The time delay is associated with the response of the gas to changes in the ionizing source, either by photoionization or radiative recombination, which is dependent on its density. The range of radial distances that, under our assumptions, yield longer time delays are distances r 0.3-1.0 × 1016 cm, and hence gas densities n 0.4-3.0 × 107 cm-3. Since these ranges are comparable to the existing estimates of the location of the warm absorber in NGC 4051, we suggest that it is likely that the observed X-ray time lags may carry a signature of the warm absorber response time to changes in the ionizing continuum. Our results show that the warm absorber in NGC 4051 does not introduce lags on the short timescales associated with reverberation, but will likely modify the hard continuum lags seen on longer timescales, which in this source have been measured to be on the order of 50 s. Hence, these

  5. Durability of Polymeric Glazing and Absorber Materials

    SciTech Connect

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

    2005-11-01

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

  6. V-band IMPATT transmitter

    NASA Technical Reports Server (NTRS)

    Williams, D.; Ying, R. S.

    1983-01-01

    A V-band transmitter for communication application was developed that has 30 dB gain and consists of six stages of IMPATT amplifiers. The low and medium power stages are stable amplifiers while the two high power stages are triggered oscillators. Hybrid couplers in the form of Magic Tees were used for power combining two single diode IMPATT modules in the high driver stage and for a single diode IMPATT modules at the output stage. Output power of 4 watts CW across a 2.5 GHz band centered at 60 GHz was achieved with an input power of 4 mW. Dynamic range of the amplifier chain is in excess of 7 dB. A single diode one watt stable amplifier over a bandwidth greater than 2.5 GHz, a high power ( 1 watt) stable amplifier capable of operating in either the constant current or constant voltage mode and verification of the advantages of the latter mode of operation; and a 10 channel modulator with built in test equipment (specifically protective circuitry, failure monitoring, and mode of failure indicated) were also developed. The performance requirements of circulators/isolators for reflection amplifiers were also defined and verified.

  7. New insights into the opening band gap of graphene oxides

    NASA Astrophysics Data System (ADS)

    Tran, Ngoc Thanh Thuy; Lin, Shih-Yang; Lin, Ming-Fa

    Electronic properties of oxygen absorbed few-layer graphenes are investigated using first-principle calculations. They are very sensitive to the changes in the oxygen concentration, number of graphene layer, and stacking configuration. The feature-rich band structures exhibit the destruction or distortion of the Dirac cone, opening of band gap, anisotropic energy dispersions, O- and (C,O)-dominated energy dispersions, and extra critical points. The band decomposed charge distributions reveal the π-bonding dominated energy gap. The orbital-projected density of states (DOS) have many special structures mainly coming from a composite energy band, the parabolic and partially flat ones. The DOS and spatial charge distributions clearly indicate the critical orbital hybridizations in O-O, C-O and C-C bonds, being responsible for the diversified properties. All of the few-layer graphene oxides are semi-metals except for the semiconducting monolayer ones.

  8. Experimental Demonstration of Printed Graphene Nano-flakes Enabled Flexible and Conformable Wideband Radar Absorbers.

    PubMed

    Huang, Xianjun; Pan, Kewen; Hu, Zhirun

    2016-12-07

    In this work, we have designed, fabricated and experimentally characterized a printed graphene nano-flakes enabled flexible and conformable wideband radar absorber. The absorber covers both X (8-12 GHz) and Ku (12-18 GHz) bands and is printed on flexible substrate using graphene nano-flakes conductive ink through stencil printing method. The measured results show that an effective absorption (above 90%) bandwidth spans from 10.4 GHz to 19.7 GHz, namely a 62% fraction bandwidth, with only 2 mm thickness. The flexibility of the printed graphene nano-flakes enables the absorber conformably bending and attaching to a metal cylinder. The radar cross section (RCS) of the cylinder with and without absorber attachment has been compared and excellent absorption has been obtained. Only 3.6% bandwidth reduction has been observed comparing to that of un-bended absorber. This work has demonstrated unambiguously that printed graphene can provide flexible and conformable wideband radar absorption, which extends the graphene's application to practical RCS reductions.

  9. Experimental Demonstration of Printed Graphene Nano-flakes Enabled Flexible and Conformable Wideband Radar Absorbers

    NASA Astrophysics Data System (ADS)

    Huang, Xianjun; Pan, Kewen; Hu, Zhirun

    2016-12-01

    In this work, we have designed, fabricated and experimentally characterized a printed graphene nano-flakes enabled flexible and conformable wideband radar absorber. The absorber covers both X (8–12 GHz) and Ku (12–18 GHz) bands and is printed on flexible substrate using graphene nano-flakes conductive ink through stencil printing method. The measured results show that an effective absorption (above 90%) bandwidth spans from 10.4 GHz to 19.7 GHz, namely a 62% fraction bandwidth, with only 2 mm thickness. The flexibility of the printed graphene nano-flakes enables the absorber conformably bending and attaching to a metal cylinder. The radar cross section (RCS) of the cylinder with and without absorber attachment has been compared and excellent absorption has been obtained. Only 3.6% bandwidth reduction has been observed comparing to that of un-bended absorber. This work has demonstrated unambiguously that printed graphene can provide flexible and conformable wideband radar absorption, which extends the graphene’s application to practical RCS reductions.

  10. Infrared broadband metasurface absorber for reducing the thermal mass of a microbolometer.

    PubMed

    Jung, Joo-Yun; Song, Kyungjun; Choi, Jun-Hyuk; Lee, Jihye; Choi, Dae-Geun; Jeong, Jun-Ho; Neikirk, Dean P

    2017-03-27

    We demonstrate an infrared broadband metasurface absorber that is suitable for increasing the response speed of a microbolometer by reducing its thermal mass. A large fraction of holes are made in a periodic pattern on a thin lossy metal layer characterised with a non-dispersive effective surface impedance. This can be used as a non-resonant metasurface that can be integrated with a Salisbury screen absorber to construct an absorbing membrane for a microbolometer that can significantly reduce the thermal mass while maintaining high infrared broadband absorption in the long wavelength infrared (LWIR) band. The non-dispersive effective surface impedance can be matched to the free space by optimising the surface resistance of the thin lossy metal layer depending on the size of the patterned holes by using a dc approximation method. In experiments a high broadband absorption was maintained even when the fill factor of the absorbing area was reduced to 28% (hole area: 72%), and it was theoretically maintained even when the fill factor of the absorbing area was reduced to 19% (hole area: 81%). Therefore, a metasurface with a non-dispersive effective surface impedance is a promising solution for reducing the thermal mass of infrared microbolometer pixels.

  11. Experimental Demonstration of Printed Graphene Nano-flakes Enabled Flexible and Conformable Wideband Radar Absorbers

    PubMed Central

    Huang, Xianjun; Pan, Kewen; Hu, Zhirun

    2016-01-01

    In this work, we have designed, fabricated and experimentally characterized a printed graphene nano-flakes enabled flexible and conformable wideband radar absorber. The absorber covers both X (8–12 GHz) and Ku (12–18 GHz) bands and is printed on flexible substrate using graphene nano-flakes conductive ink through stencil printing method. The measured results show that an effective absorption (above 90%) bandwidth spans from 10.4 GHz to 19.7 GHz, namely a 62% fraction bandwidth, with only 2 mm thickness. The flexibility of the printed graphene nano-flakes enables the absorber conformably bending and attaching to a metal cylinder. The radar cross section (RCS) of the cylinder with and without absorber attachment has been compared and excellent absorption has been obtained. Only 3.6% bandwidth reduction has been observed comparing to that of un-bended absorber. This work has demonstrated unambiguously that printed graphene can provide flexible and conformable wideband radar absorption, which extends the graphene’s application to practical RCS reductions. PMID:27924823

  12. Optimization of a hybrid vibration absorber for vibration control of structures under random force excitation

    NASA Astrophysics Data System (ADS)

    Cheung, Y. L.; Wong, W. O.; Cheng, L.

    2013-02-01

    A recently reported design of a hybrid vibration absorber (HVA) which is optimized to suppress resonant vibration of a single degree-of-freedom (SDOF) system is re-optimized for suppressing wide frequency band vibration of the SDOF system under stationary random force excitation. The proposed HVA makes use of the feedback signals from the displacement and velocity of the absorber mass for minimizing the vibration response of the dynamic structure based on the H2 optimization criterion. The objective of the optimal design is to minimize the mean square vibration amplitude of a dynamic structure under a wideband excitation, i.e., the total area under the vibration response spectrum is minimized in this criterion. One of the inherent limitations of the traditional passive vibration absorber is that its vibration suppression is low if the mass ratio between the absorber mass and the mass of the primary structure is low. The active element of the proposed HVA helps further reduce the vibration of the controlled structure and it can provide significant vibration absorption performance even at a low mass ratio. Both the passive and active elements are optimized together for the minimization of the mean square vibration amplitude of the primary system. The proposed HVA are tested on a SDOF system and continuous vibrating structures with comparisons to the traditional passive vibration absorber.

  13. Asymmetric double split-ring metamaterials absorber in the terahertz region

    NASA Astrophysics Data System (ADS)

    Jun, He; Li, Qingmei; Shen, Jingling

    2012-12-01

    We present the simulation of an asymmetric double split-ring metamaterials absorber in terahertz region. The device consists of a metal/dielectric-spacer/metal structure allowing us select absorption by varying the asymmetric characteristics. When the two gaps are gradually away from the center in opposite direction, a giant amplitude modulation is observed at the fundamental inductive-capacitive (LC) resonance and the resonant frequencies are observed to red shifting. Besides, increasing the thickness of dielectric-spacer, the peak absorption can be changed. This theoretical simulation will be good reference for the follow experiments, and these asymmetric metamaterials absorbers is expected to be used as cloaking materials.

  14. Tunable microwave absorbing nano-material for X-band applications

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Ashiq, Muhammad Naeem; Khan, M. A.; Niaz, Shanawer; Rana, M. U.

    2016-03-01

    The effect of rare earth elements substitution in Sr1.96RE0.04Co2Fe27.80Mn0.2O46 (RE=Ce, Gd, Nd, La and Sm) X-type hexagonal ferrites prepared by using sol gel autocombustion method was studied. The XRD and FTIR analysis show the single phase of the prepared material. The lattice constants a (Å) and c (Å) varies with the additives. The particle size measured by Scherer formula for all the samples varies in the range of 54-100 nm and confirmed by the TEM analysis. The average grain size measured by SEM analysis lies in the range of 0.672-1.01 μm for all the samples. The Gd-substituted ferrite has higher value of coercivity (526.06 G) among all the samples which could be a good material for longitudinal recording media. The results also indicate that the Gd-substituted sample has maximum reflection loss of -25.2 dB at 11.878 GHz, can exhibit the best microwave absorption properties among all the substituted samples. Furthermore, the minimum value of reflection loss shifts towards the lower and higher frequencies with the substitution of rare earth elements which confirms that the microwave absorption properties can be tuned with the substitution of rare earth elements in pure ferrites. The peak value of attenuation constant at higher frequency agrees well the reflection loss data.

  15. Tunable Narrow Band Gap Absorbers For Ultra High Efficiency Solar Cells

    SciTech Connect

    Bedair, Salah M.; Hauser, John R.; Elmasry, Nadia; Colter, Peter C.; Bradshaw, G.; Carlin, C. Z.; Samberg, J.; Edmonson, Kenneth

    2012-07-31

    We report on a joint research program between NCSU and Spectrolab to develop an upright multijunction solar cell structure with a potential efficiency exceeding the current record of 41.6% reported by Spectrolab. The record efficiency Ge/GaAs/InGaP triple junction cell structure is handicapped by the fact that the current generated by the Ge cell is much higher than that of both the middle and top cells. We carried out a modification of the record cell structure that will keep the lattice matched condition and allow better matching of the current generated by each cell. We used the concept of strain balanced strained layer superlattices (SLS), inserted in the i-layer, to reduce the bandgap of the middle cell without violating the desirable lattice matched condition. For the middle GaAs cell, we have demonstrated an n-GaAs/i-(InGaAs/GaAsP)/p-GaAs structure, where the InxGa1-xAs/GaAs1-yPy SLS is grown lattice matched to GaAs and with reduced bandgap from 1.43 eV to 1.2 eV, depending upon the values of x and y.

  16. Perovskite semiconductor La(Ni0.75W0.25)O3 nanoparticles for visible-light-absorbing photocatalytic material

    NASA Astrophysics Data System (ADS)

    Xu, Lei; Xie, Hongde; Pu, Yinfu; Huang, Yanlin; Qin, Lin; Seo, Hyo Jin

    2017-01-01

    La(Ni0.75W0.25)O3 perovskite oxide was prepared via the sol-gel Pechini route. The pure crystalline phase was verified via X-ray diffraction measurements and Rietveld structure refinements. Some measurements were applied to characterize the surface of the nanoparticles such as transmission electron microscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, specific surface area, and X-ray photo-electron spectroscopy measurements. The optical measurement confirmed that this perovskite oxide can absorb the visible light presenting low band energy of 2.41 eV. The d-d allowed transitions in Ni2+-O octahedral have great contributions to the narrow band-gap. The Ni2+-containing perovskite was applied as a photocatalyst showing the desirable photodegradation ability for methylene blue solutions under the excitation of visible-light. The photocatalysis activities were discussed in the relationship with its special perovskite-type structure such as the NiO6 color centers and multivalent cation ions etc.

  17. 21 CFR 880.6025 - Absorbent tipped applicator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Absorbent tipped applicator. 880.6025 Section 880... Devices § 880.6025 Absorbent tipped applicator. (a) Identification. An absorbent tipped applicator is a device intended for medical purposes that consists of an absorbent swab on a wooden, paper, or...

  18. The Cooling of a Liquid Absorber using a Small Cooler

    SciTech Connect

    Baynham, D.E.; Bradshaw, T.W.; Green, M.A.; Ishimoto, S.; Liggins, N.

    2005-08-24

    This report discusses the use of small cryogenic coolers for cooling the Muon Ionization Cooling Experiment (MICE) liquid cryogen absorbers. Since the absorber must be able contain liquid helium as well liquid hydrogen, the characteristics of the available 4.2 K coolers are used here. The issues associated with connecting two-stage coolers to liquid absorbers are discussed. The projected heat flows into an absorber and the cool-down of the absorbers using the cooler are presented. The warm-up of the absorber is discussed. Special hydrogen safety issues that may result from the use of a cooler on the absorbers are also discussed.

  19. Obituary: David L. Band (1957-2009)

    NASA Astrophysics Data System (ADS)

    Cominsky, Lynn

    2011-12-01

    David L. Band, of Potomac Maryland, died on March 16, 2009 succumbing to a long battle with spinal cord cancer. His death at the age of 52 came as a shock to his many friends and colleagues in the physics and astronomy community. Band showed an early interest and exceptional aptitude for physics, leading to his acceptance at the Massachusetts Institute of Technology as an undergraduate student in 1975. After graduating from MIT with an undergraduate degree in Physics, Band continued as a graduate student in Physics at Harvard University. His emerging interest in Astrophysics led him to the Astronomy Department at the Harvard Smithsonian Center for Astrophysics (CfA), where he did his dissertation work with Jonathan Grindlay. His dissertation (1985) entitled "Non-thermal Radiation Mechanisms and Processes in SS433 and Active Galactic Nuclei" was "pioneering work on the physics of jets arising from black holes and models for their emission, including self-absorption, which previewed much to come, and even David's own later work on Gamma-ray Bursts," according to Grindlay who remained a personal friend and colleague of Band's. Following graduate school, Band held postdoctoral positions at the Lawrence Livermore Laboratory, the University of California at Berkeley and the Center for Astronomy and Space Sciences at the University of California San Diego where he worked on the BATSE experiment that was part of the Compton Gamma Ray Observatory (CGRO), launched in 1991. BATSE had as its main objective the study of cosmic gamma-ray bursts (GRBs) and made significant advances in this area of research. Band became a world-renowned figure in the emerging field of GRB studies. He is best known for his widely-used analytic form of gamma-ray burst spectra known as the "Band Function." After the CGRO mission ended, Band moved to the Los Alamos National Laboratory where he worked mainly on classified research but continued to work on GRB energetics and spectra. When NASA planned

  20. Methods of calculating radiation absorbed dose.

    PubMed

    Wegst, A V

    1987-01-01

    The new tumoricidal radioactive agents being developed will require a careful estimate of radiation absorbed tumor and critical organ dose for each patient. Clinical methods will need to be developed using standard imaging or counting instruments to determine cumulated organ activities with tracer amounts before the therapeutic administration of the material. Standard MIRD dosimetry methods can then be applied.

  1. Moving core beam energy absorber and converter

    DOEpatents

    Degtiarenko, Pavel V.

    2012-12-18

    A method and apparatus for the prevention of overheating of laser or particle beam impact zones through the use of a moving-in-the-coolant-flow arrangement for the energy absorbing core of the device. Moving of the core spreads the energy deposition in it in 1, 2, or 3 dimensions, thus increasing the effective cooling area of the device.

  2. Composition for absorbing hydrogen from gas mixtures

    DOEpatents

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

    1999-01-01

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

  3. 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.

  4. How to build a molecular shock absorber.

    PubMed

    McGough, A

    1999-12-02

    Newly determined structures of the alpha-helical repeats that make up the key 'rod' domains of spectrin and alpha-actinin - which serve as spacers between their actin-binding domains - have provided important insights into how these proteins function as molecular shock absorbers in cells.

  5. Novel shock absorber features varying yield strengths

    NASA Technical Reports Server (NTRS)

    Geier, D. J.

    1964-01-01

    A shock absorbent webbing of partially drawn synthetic strands is arranged in sections of varying density related to the varying mass of the human body. This is contoured to protect the body at points of contact, when subjected to large acceleration or deceleration forces.

  6. Shock absorber protects motive components against overloads

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Shock absorber with an output shaft, hollow gear, and a pair of springs forming a resilient driving connection between shaft and gear, operates when abnormally high torques are applied. This simple durable frictional device is valuable in rotating mechanisms subject to sudden overloads.

  7. Torus elements used in effective shock absorber

    NASA Technical Reports Server (NTRS)

    Cunningham, P.; Platus, D. L.

    1966-01-01

    Energy absorbing device forces torus elements to revolve annularly between two concentric tubes when a load is applied to one tube. Interference forces can be varied by using torus elements of different thicknesses. The device operates repeatedly in compression or tension, and under problems of large onset rate tolerance or structural overload.

  8. Aldehyde-containing urea-absorbing polysaccharides

    NASA Technical Reports Server (NTRS)

    Mueller, W. A.; Hsu, G. C.; Marsh, H. E., Jr. (Inventor)

    1977-01-01

    A novel aldehyde containing polymer (ACP) is prepared by reaction of a polysaccharide with periodate to introduce aldehyde groups onto the C2 - C3 carbon atoms. By introduction of ether and ester groups onto the pendant primary hydroxyl solubility characteristics are modified. The ACP is utilized to absorb nitrogen bases such as urea in vitro or in vivo.

  9. Theory of vortices in hybridized ballistic/diffusive-band superconductors

    NASA Astrophysics Data System (ADS)

    Tanaka, K.; Eschrig, M.; Agterberg, D. F.

    2007-06-01

    We study the electronic structure in the vicinity of a vortex in a two-band superconductor in which the quasiparticle motion is ballistic in one band and diffusive in the other. This study is based on a model appropriate for such a case, that we have introduced recently [Tanaka , Phys. Rev. B 73, 220501(R) (2006)]. We argue that in the two-band superconductor MgB2 , such a case is realized. Motivated by the experimental findings on MgB2 , we assume that superconductivity in the diffusive band is “weak,” i.e., mostly induced. We examine intriguing features of the order parameter, the current density, and the vortex core spectrum in the “strong” ballistic band under the influence of hybridization with the “weak” diffusive band. Although the order parameter in the diffusive band is induced, the characteristic length scales in the two bands differ due to Coulomb interactions. The current density in the vortex core is dominated by the contribution from the ballistic band, while outside the core the contribution from the diffusive band can be substantial, or even dominating. The current density in the diffusive band has strong temperature dependence, exhibiting the Kramer-Pesch effect when hybridization is strong. A particularly interesting feature of our model is the possibility of additional bound states near the gap edge in the ballistic band, that are prominent in the vortex center spectra. This contrasts with the single band case, where there is no gap-edge bound state in the vortex center. We find the above-mentioned unique features for parameter values relevant for MgB2 .

  10. Observation of band gaps in the gigahertz range and deaf bands in a hypersonic aluminum nitride phononic crystal slab

    NASA Astrophysics Data System (ADS)

    Gorisse, M.; Benchabane, S.; Teissier, G.; Billard, C.; Reinhardt, A.; Laude, V.; Defaÿ, E.; Aïd, M.

    2011-06-01

    We report on the observation of elastic waves propagating in a two-dimensional phononic crystal composed of air holes drilled in an aluminum nitride membrane. The theoretical band structure indicates the existence of an acoustic band gap centered around 800 MHz with a relative bandwidth of 6.5% that is confirmed by gigahertz optical images of the surface displacement. Further electrical measurements and computation of the transmission reveal a much wider attenuation band that is explained by the deaf character of certain bands resulting from the orthogonality of their polarization with that of the source.

  11. Absorbed fractions for electrons in ellipsoidal volumes

    NASA Astrophysics Data System (ADS)

    Amato, E.; Lizio, D.; Baldari, S.

    2011-01-01

    We applied a Monte Carlo simulation in Geant4 in order to calculate the absorbed fractions for monoenergetic electrons in the energy interval between 10 keV and 2 MeV, uniformly distributed in ellipsoids made from soft tissue. For each volume, we simulated a spherical shape, four oblate and four prolate ellipsoids, and one scalene shape. For each energy and for every geometrical configuration, an analytical relationship between the absorbed fraction and a 'generalized radius' was found, and the dependence of the fit parameters from electron energy is discussed and fitted by proper parametric functions. With the proposed formulation, the absorbed fraction for electrons in the 10-2000 keV energy range can be calculated for all volumes and for every ellipsoidal shape of practical interest. This method can be directly applied to evaluation of the absorbed fraction from the radionuclide emission of monoenergetic electrons, such as Auger or conversion electrons. The average deposited energy per disintegration in the case of extended beta spectra can be evaluated through integration. Two examples of application to a pure beta emitter such as 90Y and to 131I, whose emission include monoenergetic and beta electrons plus gamma photons, are presented. This approach represent a generalization of our previous studies, allowing a comprehensive treatment of absorbed fractions from electron and photon sources uniformly distributed in ellipsoidal volumes of any ellipticity and volume, in the whole range of practical interest for internal dosimetry in nuclear medicine applications, as well as in radiological protection estimations of doses from an internal contamination.

  12. Absorbed fractions for electrons in ellipsoidal volumes.

    PubMed

    Amato, E; Lizio, D; Baldari, S

    2011-01-21

    We applied a Monte Carlo simulation in Geant4 in order to calculate the absorbed fractions for monoenergetic electrons in the energy interval between 10 keV and 2 MeV, uniformly distributed in ellipsoids made from soft tissue. For each volume, we simulated a spherical shape, four oblate and four prolate ellipsoids, and one scalene shape. For each energy and for every geometrical configuration, an analytical relationship between the absorbed fraction and a 'generalized radius' was found, and the dependence of the fit parameters from electron energy is discussed and fitted by proper parametric functions. With the proposed formulation, the absorbed fraction for electrons in the 10-2000 keV energy range can be calculated for all volumes and for every ellipsoidal shape of practical interest. This method can be directly applied to evaluation of the absorbed fraction from the radionuclide emission of monoenergetic electrons, such as Auger or conversion electrons. The average deposited energy per disintegration in the case of extended beta spectra can be evaluated through integration. Two examples of application to a pure beta emitter such as (90)Y and to (131)I, whose emission include monoenergetic and beta electrons plus gamma photons, are presented. This approach represent a generalization of our previous studies, allowing a comprehensive treatment of absorbed fractions from electron and photon sources uniformly distributed in ellipsoidal volumes of any ellipticity and volume, in the whole range of practical interest for internal dosimetry in nuclear medicine applications, as well as in radiological protection estimations of doses from an internal contamination.

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

    PubMed Central

    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. PMID:27270944

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

    SciTech Connect

    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.

  15. Banded transformer cores

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W. T. (Inventor)

    1974-01-01

    A banded transformer core formed by positioning a pair of mated, similar core halves on a supporting pedestal. The core halves are encircled with a strap, selectively applying tension whereby a compressive force is applied to the core edge for reducing the innate air gap. A dc magnetic field is employed in supporting the core halves during initial phases of the banding operation, while an ac magnetic field subsequently is employed for detecting dimension changes occurring in the air gaps as tension is applied to the strap.

  16. Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events

    NASA Astrophysics Data System (ADS)

    Wang, P.; Tuinder, O. N. E.; Tilstra, L. G.; Stammes, P.

    2011-12-01

    Cloud and aerosol information is needed in trace gas retrievals from satellite measurements. The Fast REtrieval Scheme for Clouds from the Oxygen A band (FRESCO) cloud algorithm employs reflectance spectra of the O2 A band around 760 nm to derive cloud pressure and effective cloud fraction. In general, clouds contribute more to the O2 A band reflectance than aerosols. Therefore, the FRESCO algorithm does not correct for aerosol effects in the retrievals and attributes the retrieved cloud information entirely to the presence of clouds, and not to aerosols. For events with high aerosol loading, aerosols may have a dominant effect, especially for almost cloud-free scenes. We have analysed FRESCO cloud data and Absorbing Aerosol Index (AAI) data from the Global Ozone Monitoring Experiment (GOME-2) instrument on the Metop-A satellite for events with typical absorbing aerosol types, such as volcanic ash, desert dust and smoke. We find that the FRESCO effective cloud fractions are correlated with the AAI data for these absorbing aerosol events and that the FRESCO cloud pressures contain information on aerosol layer pressure. For cloud-free scenes, the derived FRESCO cloud pressures are close to those of the aerosol layer for optically thick aerosols. For cloudy scenes, if the strongly absorbing aerosols are located above the clouds, then the retrieved FRESCO cloud pressures may represent the height of the aerosol layer rather than the height of the clouds. Combining FRESCO cloud data and AAI, an estimate for the aerosol layer pressure can be given, which can be beneficial for aviation safety and operations in case of e.g. volcanic ash plumes.

  17. Extremely long carrier lifetime at intermediate states in wall-inserted type II quantum dot absorbers

    NASA Astrophysics Data System (ADS)

    Sato, Daisuke; Ota, Junya; Nishikawa, Kazutaka; Takeda, Yasuhiko; Miyashita, Naoya; Okada, Yoshitaka

    2012-11-01

    To realize highly efficient intermediate-band solar cells (IB-SCs), a long lifetime of photo-generated carriers in the IB is essential. We propose a new concept for this purpose based on IB absorbers using quantum-dots (QDs). By inserting potential walls between QDs and barriers that form a type II band alignment, electrons in the IB and holes in the valence band are farther separated compared to those in a conventional type II QD material, leading to significant reduction of radiative recombination. We designed a concrete structure using InAs QDs, GaAs1-xSbx barriers, and GaAs walls to find the suitable GaAs wall thickness and Sb content being 2 nm and x = 0.18, respectively, and demonstrated a lifetime of electrons excited to the IB as long as 220 ns.

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

    SciTech Connect

    Not Available

    2011-10-01

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

  19. Multi-Band-SWIFT

    NASA Astrophysics Data System (ADS)

    Idiyatullin, Djaudat; Corum, Curtis A.; Garwood, Michael

    2015-02-01

    A useful extension to SWIFT (SWeep Imaging with Fourier Transformation) utilizing sidebands of the excitation pulse is introduced. This MRI method, called Multi-Band-SWIFT, achieves much higher bandwidth than standard SWIFT by using multiple segmented excitations (bands) of the field of view. A description of the general idea and variants of the pulse sequence are presented. From simulations and semi-phenomenological theory, estimations of power deposition and signal-to-noise ratio are made. MB-SWIFT and ZTE (zero-TE) sequences are compared based on images of a phantom and human mandible. Multi-Band-SWIFT provides a bridge between SWIFT and ZTE sequences and allows greatly increased excitation and acquisition bandwidths relative to standard SWIFT for the same hardware switching parameters and requires less peak amplitude of the radiofrequency field (or greater flip angle at same peak amplitude) as compared to ZTE. Multi-Band-SWIFT appears to be an attractive extension of SWIFT for certain musculoskeletal and other medical imaging applications, as well as for imaging materials.

  20. Multi-Band-SWIFT.

    PubMed

    Idiyatullin, Djaudat; Corum, Curtis A; Garwood, Michael

    2015-02-01

    A useful extension to SWIFT (SWeep Imaging with Fourier Transformation) utilizing sidebands of the excitation pulse is introduced. This MRI method, called Multi-Band-SWIFT, achieves much higher bandwidth than standard SWIFT by using multiple segmented excitations (bands) of the field of view. A description of the general idea and variants of the pulse sequence are presented. From simulations and semi-phenomenological theory, estimations of power deposition and signal-to-noise ratio are made. MB-SWIFT and ZTE (zero-TE) sequences are compared based on images of a phantom and human mandible. Multi-Band-SWIFT provides a bridge between SWIFT and ZTE sequences and allows greatly increased excitation and acquisition bandwidths relative to standard SWIFT for the same hardware switching parameters and requires less peak amplitude of the radiofrequency field (or greater flip angle at same peak amplitude) as compared to ZTE. Multi-Band-SWIFT appears to be an attractive extension of SWIFT for certain musculoskeletal and other medical imaging applications, as well as for imaging materials.

  1. Banded Sunflower Moth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The banded sunflower moth, Cochylis hospes Walsingham, is an important insect pest of cultivated sunflower. Eggs are deposited on the bracts of sunflower heads. Larvae develop through five instars within the heads and are present in fields from mid-July to mid-September. Larvae feed initially on the...

  2. Absorbed dose thresholds and absorbed dose rate limitations for studies of electron radiation effects on polyetherimides

    NASA Technical Reports Server (NTRS)

    Long, Edward R., Jr.; Long, Sheila Ann T.; Gray, Stephanie L.; Collins, William D.

    1989-01-01

    The threshold values of total absorbed dose for causing changes in tensile properties of a polyetherimide film and the limitations of the absorbed dose rate for accelerated-exposure evaluation of the effects of electron radiation in geosynchronous orbit were studied. Total absorbed doses from 1 kGy to 100 MGy and absorbed dose rates from 0.01 MGy/hr to 100 MGy/hr were investigated, where 1 Gy equals 100 rads. Total doses less than 2.5 MGy did not significantly change the tensile properties of the film whereas doses higher than 2.5 MGy significantly reduced elongation-to-failure. There was no measurable effect of the dose rate on the tensile properties for accelerated electron exposures.

  3. INTERSTELLAR EXTINCTION LAW TOWARD THE GALACTIC CENTER III: J, H, K{sub S} BANDS IN THE 2MASS AND THE MKO SYSTEMS, AND 3.6, 4.5, 5.8, 8.0 {mu}m IN THE SPITZER/IRAC SYSTEM

    SciTech Connect

    Nishiyama, Shogo; Nagata, Tetsuya; Tamura, Motohide; Hatano, Hirofumi; Kato, Daisuke; Tanabe, Toshihiko; Sugitani, Koji

    2009-05-10

    We have determined interstellar extinction law toward the Galactic center (GC) at the wavelength from 1.2 to 8.0 {mu}m, using point sources detected in the IRSF/SIRIUS near-infrared (NIR) survey and those in the Two Micron All Sky Survey (2MASS) and Spitzer/IRAC/GLIMPSE II catalogs. The central region |l | {approx}<3.{sup 0}0 and |b | {approx}<1.{sup 0}0 has been surveyed in the J, H, and K{sub S} bands with the IRSF telescope and the SIRIUS camera whose filters are similar to the Mauna Kea Observatories (MKO) NIR photometric system. Combined with the GLIMPSE II point source catalog, we made K{sub S} versus K{sub S} - {lambda} color-magnitude diagrams (CMDs) where {lambda}=3.6, 4.5, 5.8, and 8.0 {mu}m. The K{sub S} magnitudes of bulge red clump stars and the K{sub S} - {lambda} colors of red giant branches are used as a tracer of the reddening vector in the CMDs. From these magnitudes and colors, we have obtained the ratios of total-to-selective extinction A{sub K{sub S}}/E{sub K{sub S}}{sub -{lambda}} for the four IRAC bands. Combined with A{sub {lambda}}/A{sub K{sub S}} for the J and H bands derived by Nishiyama et al., we obtain A{sub J} :A{sub H} :A{sub K{sub S}}:A {sub [3.6]}:A {sub [4.5]}:A {sub [5.8]}:A {sub [8.0]} = 3.02:1.73:1:0.50:0.39:0.36:0.43 for the line of sight toward the GC. This confirms the flattening of the extinction curve at {lambda} {approx}> 3 {mu}m from a simple extrapolation of the power-law extinction at shorter wavelengths, in accordance with recent studies. The extinction law in the 2MASS J, H, and K{sub S} bands has also been calculated, and good agreement with that in the MKO system is found. Thus, it is established that the extinction in the wavelength range of J, H, and K{sub S} is well fitted by a power law of steep decrease A {sub {lambda}} {proportional_to} {lambda}{sup -2.0} toward the GC. In nearby molecular clouds and diffuse interstellar medium, the lack of reliable measurements of the total-to-selective extinction ratios

  4. Determination of the primary charge separation rate in isolated photosystem II reaction centers with 500-fs time resolution

    SciTech Connect

    Wasielewski, M.R.; Johnson, D.G. ); Seibert, M. ); Govindjee )

    1989-01-01

    The authors have measured directly the rate of formation of the oxidized chlorophyll a electron donor (P680+) and the reduced electron acceptor pheophytin a{sup {minus}} (Pheoa{sup {minus}}) following excitation of isolated spinach photosystem II reaction centers at 4{degree}C. The reaction-center complex consists of D{sub 1}, D{sub 2}, and cytochrome b-559 proteins and was prepared by a procedure that stabilizes the protein complex. Transient absorption difference spectra were measured from 440 to 850 nm as a function of time with 500-fs resolution following 610-nm laser excitation. The formation of P680+-Pheoa{sup {minus}} is indicated by the appearance of a band due to P680+ at 820 nm and corresponding absorbance changes at 505 and 540 nm due to formation of Pheoa{sup {minus}}. The appearance of the 820-nm band is monoexponential with {tau} = 3.0 {plus minus} 0.6 ps. Treatment of the photosystem II reaction centers with sodium dithionite and methyl viologen followed by exposure to laser excitation, conditions known to result in accumulation of Pheoa{sup {minus}}, results in formation of a transient absorption spectrum due to {sup 1*}P680. They find no evidence for an electron acceptor that precedes the formation of Pheoa{sup {minus}}.

  5. Design of a non-traditional dynamic vibration absorber.

    PubMed

    Cheung, Y L; Wong, W O

    2009-08-01

    A non-traditional dynamic vibration absorber is proposed for the minimization of maximum vibration velocity response of a vibrating structure. Unlike the traditional damped absorber configuration, the proposed absorber has a linear viscous damper connecting the absorber mass directly to the ground instead of the main mass. Optimum parameters of the proposed absorber are derived based on the fixed-point theory for minimizing the maximum vibration velocity response of a single-degree-of-freedom system under harmonic excitation. The extent of reduction in maximum vibration velocity response of the primary system when using the traditional dynamic absorber is compared with that using the proposed one. Under the optimum tuning condition of the absorbers, it is proved analytically that the proposed absorber provides a greater reduction in maximum vibration velocity response of the primary system than the traditional absorber.

  6. MAGIICAT II. GENERAL CHARACTERISTICS OF THE Mg II ABSORBING CIRCUMGALACTIC MEDIUM

    SciTech Connect

    Nielsen, Nikole M.; Churchill, Christopher W.; Kacprzak, Glenn G. E-mail: cwc@nmsu.edu

    2013-10-20

    We examine the Mg II absorbing circumgalactic medium (CGM) for the 182 intermediate redshift (0.072 ≤ z ≤ 1.120) galaxies in the 'Mg II Absorber-Galaxy Catalog' (MAGIICAT). We parameterize the anti-correlation between equivalent width, W{sub r} (2796), and impact parameter, D, with a log-linear fit, and show that a power law poorly describes the data. We find that higher luminosity galaxies have larger W{sub r} (2796) at larger D (4.3σ). The covering fractions, f{sub c} , decrease with increasing D and W{sub r} (2796) detection threshold. Higher luminosity galaxies have larger f{sub c} ; no absorption is detected in lower luminosity galaxies beyond 100 kpc. Bluer and redder galaxies have similar f{sub c} for D < 100 kpc, but for D > 100 kpc, bluer galaxies have larger f{sub c} , as do higher redshift galaxies. The 'absorption radius', R(L) = R{sub *}(L/L*){sup β}, which we examine for four different W{sub r} (2796) detection thresholds, is more luminosity sensitive to the B-band than the K-band, more sensitive for redder galaxies than for bluer galaxies, and does not evolve with redshift for the K-band, but becomes more luminosity sensitive toward lower redshift for the B-band. These trends clearly indicate a more extended Mg II absorbing CGM around higher luminosity, bluer, and higher redshift galaxies. Several of our findings are in conflict with other works. We address these conflicts and discuss the implications of our results for the low-ionization, intermediate redshift CGM.

  7. Mutual orientation of absorbing chromophores and long wavelength pigments in photosystem I particles

    NASA Astrophysics Data System (ADS)

    Andreeva, Atanaska; Velitchkova, Maya

    1998-04-01

    The fluorescence anisotropy of photosystem I particles, isolated from spinach chloroplasts and containing approximately 200 chlorophyll molecules per reaction center, has been investigated at low temperatures. Fluorescence anisotropy has been measured upon excitation with laser lines at 476.5 and 632.8 nm. Using our data for the fluorescence anisotropy at these conditions and the new `practical' formula for the degree of polarization of a triple-chromophore complex under steady-state excitation, derived recently by Demidov, we estimate the mutual orientation of absorbing chromophores and long wavelength pigments—chlorophyll a molecules, that absorb at wavelengths longer than the corresponding reaction center, in Photosystem I particles. The angle between the transition dipole moments of chlorophyll a, belonging to the light-harvesting complex of PS I and absorbing the excitation at 632.8 nm, and the emitting long wavelength pigment at 735 nm is estimated to be 40°, whereas the angle between the transition dipole moments of chlorophyll b, belonging to the light-harvesting complex of PS I and absorbing the excitation at 476.5 nm, and the emitting long wavelength pigment at 735 nm—60°.

  8. Nanosecond passively Q-switched Nd:YVO4 laser based on WS2 saturable absorber

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Li, Lu; Wang, Yonggang; Zhang, Ling; Wen, Qiao; Yang, Guowen

    2017-04-01

    We report on a nanosecond pulse generation in a diode end-pumped passively Q-switched Nd:YVO4 laser using a tungsten disulfide (WS2) solution saturable absorber (SA). The WS2 suspension is fabricated by the liquid-phase-exfoliated method and injected into a quartz cell for the use of SA. Compared with solid absorber, such solution absorber has the virtues of good optical transparency, high heat dissipation and long term stability. By inserting the WS2 solution SA in the laser cavity, a stable Q-switched laser operation centered at 1064.45 nm wavelength is obtained with the shortest pulse duration of 788 ns and corresponding repetition rate of 333.5 kHz. The maximum average output power is registered to be 720 mW with the slope efficiency of 7.8%. To the best of our knowledge, it is the highest output power so far among pulsed lasers based on transition metal dichalcogenides (TMDs) SAs. The results demonstrate that WS2 solution absorber is a promising saturable absorber for the generation of high output power pulsed lasers.

  9. MCNP simulation of absorbed energy and dose by iodinated contrast agent

    NASA Astrophysics Data System (ADS)

    He, Wenjun; Mah, Eugene; Huda, Walter; Yao, Hai

    2012-03-01

    The purpose of this study is to investigate the absorbed dose and energy by iodinated contrast medium in diagnostic radiology. A simulation geometry in which an inner sphere (d = 0.2cm, 1cm, 5cm) filled with iodinated contrast medium (or water) is located at the center of a 20cm diameter water sphere was used in simulations performed with MCNP5 codes. Monoenergetic x-rays with energies ranging from 40 to 80keV from a cone beam source were utilized and contrast medium concentration ranged from 100 to 1mg/ml. Absorbed dose ratio (RD) to inner sphere and total absorbed energies ratio (RE) to the whole phantom with and without iodinated contrast medium were investigated. The maximum RD was ~13 for the 0.2cm diameter sphere with 100mg/ml contrast medium. The maximum RE was ~1.05 for the 5cm diameter contrast sphere at 80keV with 100mg/ml contrast medium. Under the same incident photon energy, increasing the inner sphere size from 0.2cm to 5cm caused a ~63% increase in the RD on average. Decreasing the contrast medium concentration from 100 to 10 mg/ml caused a decrease of RD of ~ 76%. A conclusion was reached that although local absorbed dose increase caused by iodinated contrast agent could be high; the increase in total absorbed energy is negligible.

  10. The Development of 6061-Aluminum Windows for the MICE LiquidAbsorber

    SciTech Connect

    Lau, W.; Yang, S.Q.; Green, M.A.; Ishimoto, S.; Swanson, J.

    2005-08-24

    The thin windows for the Muon Ionization Cooling Experiment (MICE) liquid Absorber will be fabricated from 6061-T6-aluminum. The absorber and vacuum vessel thin windows are 300-mm in diameter and are 180 mm thick at the center. The windows are designed for an internal burst pressure of 0.68 MPa (100 psig) when warm. The MICE experiment design calls for changeable windows on the absorber, so a bolted window design was adopted. Welded windows offer some potential advantages over bolted windows when they are on the absorber itself. This report describes the bolted window and its seal. This report also describes an alternate window that is welded directly to the absorber body. The welded window design presented permits the weld to be ground off and re-welded. This report presents a thermal FEA analysis of the window seal-weld, while the window is being welded. Finally, the results of a test of a welded-window are presented.

  11. Robust broadband vibration control of a flexible structure using an electrical dynamic absorber

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Myeong; Wang, Semyung; Brennan, Michael J.

    2011-07-01

    This paper presents a simple but practical feedback control method to suppress the vibration of a flexible structure in the frequency range between 10 Hz and 1 kHz. A dynamic vibration absorber is designed for this, which has a natural frequency of 100 Hz and a normalized bandwidth (twice the damping ratio) of 9.9. The absorber is realized electrically by feeding back the structural acceleration at one position on the host structure to a collocated piezoceramic patch actuator via an analog controller consisting of a second-order lowpass filter. This absorber is equivalent to a single degree-of-freedom mechanical oscillator consisting of a serially connected mass-spring-damper system. A first-order lowpass filter is additionally used to improve stability at very high frequencies. Experiments were conducted on a free-free beam embedded with a piezoceramic patch actuator and an accelerometer at its center. It is demonstrated that the single absorber can simultaneously suppress multiple vibration modes within the control bandwidth. It is further shown that the control system is robust to slight changes in the plant. The method described can be applied to many other practical structures, after retuning the absorber parameters for the structure under control.

  12. Imaging highly absorbing nanoparticles using photothermal microscopy

    NASA Astrophysics Data System (ADS)

    Lussier, Simon-Alexandre; Moradi, Hamid; Price, Alain; Murugkar, Sangeeta

    2015-03-01

    Gold nanoparticles (NPs) have tremendous potential in biomedicine. They can be used as absorbing labels inside living cells for the purpose of biomedical imaging, biosensing as well as for photothermal therapy. We demonstrate photothermal imaging of highly-absorbing particles using a pump-probe setup. The photothermal signal is recovered by heterodyne detection, where the excitation pump laser is at 532 nm and the probe laser is at 638 nm. The sample is moved by a scanning stage. Proof of concept images of red polystyrene microspheres and gold nanoparticles are obtained with this home-built multimodal microscope. The increase in temperature at the surface of the gold NPs, due to the pump laser beam, can be directly measured by means of this photothermal microscope and then compared with the results from theoretical predictions. This technique will be useful for characterization of nanoparticles of different shapes, sizes and materials that are used in cancer diagnosis and therapy.

  13. Impedance matched thin metamaterials make metals absorbing

    PubMed Central

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

    2013-01-01

    Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others. PMID:24220284

  14. A sound absorbing metasurface with coupled resonators

    NASA Astrophysics Data System (ADS)

    Li, Junfei; Wang, Wenqi; Xie, Yangbo; Popa, Bogdan-Ioan; Cummer, Steven A.

    2016-08-01

    An impedance matched surface is able, in principle, to totally absorb the incident sound and yield no reflection, and this is desired in many acoustic applications. Here we demonstrate a design of impedance matched sound absorbing surface with a simple construction. By coupling different resonators and generating a hybrid resonance mode, we designed and fabricated a metasurface that is impedance-matched to airborne sound at tunable frequencies with subwavelength scale unit cells. With careful design of the coupled resonators, over 99% energy absorption at central frequency of 511 Hz with a 50% absorption bandwidth of 140 Hz is achieved experimentally. The proposed design can be easily fabricated, and is mechanically stable. The proposed metasurface can be used in many sound absorption applications such as loudspeaker design and architectural acoustics.

  15. Absorbing Software Testing into the Scrum Method

    NASA Astrophysics Data System (ADS)

    Tuomikoski, Janne; Tervonen, Ilkka

    In this paper we study, how to absorb software testing into the Scrum method. We conducted the research as an action research during the years 2007-2008 with three iterations. The result showed that testing can and even should be absorbed to the Scrum method. The testing team was merged into the Scrum teams. The teams can now deliver better working software in a shorter time, because testing keeps track of the progress of the development. Also the team spirit is higher, because the Scrum team members are committed to the same goal. The biggest change from test manager’s point of view was the organized Product Owner Team. Test manager don’t have testing team anymore, and in the future all the testing tasks have to be assigned through the Product Backlog.

  16. The ultimate chrome absorber in photomask making

    NASA Astrophysics Data System (ADS)

    Hashimoto, Masahiro; Iwashita, Hiroyuki; Kominato, Atsushi; Shishido, Hiroaki; Ushida, Masao; Mitsui, Hideaki

    2008-05-01

    193nm-immersion lithography is the most promising technology for 32nm-node device fabrication. A new Cr absorber (TFC) for 193-nm attenuated phase-shift blanks was developed to meet the photomask requirements without any additional process step, such as hardmask etching. TFC was introduced with a design concept of the vertical profile for shorter etching time, the over etching time reduction. As a result, the dry-etching time was dramatically improved by more than 20% shorter than the conventional Cr absorber (TF11) without any process changes. We confirmed that 150nm-resist thickness was possible by TFC. The 32nm technology-node requirement is fully supported by TFC with thinner CAR, such as resolution and CD performance.

  17. Accelerated life testing of solar absorber coatings

    NASA Astrophysics Data System (ADS)

    Carlsson, Bo; Moeller, K.; Frei, Ulrich; Koehl, Michael

    1994-09-01

    Results from a comprehensive case study on accelerated life testing of some selective solar collector absorber coatings for DHW systems are reviewed. The study was conducted within Task X `Solar Materials Research and Development' of the IEA Solar Heating and Cooling Program from 1987 to 1992 and is unique due to its quantitative and systematic approach for durability assessment. The work of case study involved the development of both experimental and theoretical tools to aid the assessment of service life or absorber coatings. This entailed performance analysis, failure analysis, microclimate characterization, environmental resistance testing and life date analysis. Predicted in-service degradation of coatings from accelerated life testing was found to be in fairly good agreement both qualitatively and quantitatively with what was actually observed on coatings installed and tested for three years in solar collectors working under typical DHW conditions.

  18. Fault Detection for Automotive Shock Absorber

    NASA Astrophysics Data System (ADS)

    Hernandez-Alcantara, Diana; Morales-Menendez, Ruben; Amezquita-Brooks, Luis

    2015-11-01

    Fault detection for automotive semi-active shock absorbers is a challenge due to the non-linear dynamics and the strong influence of the disturbances such as the road profile. First obstacle for this task, is the modeling of the fault, which has been shown to be of multiplicative nature. Many of the most widespread fault detection schemes consider additive faults. Two model-based fault algorithms for semiactive shock absorber are compared: an observer-based approach and a parameter identification approach. The performance of these schemes is validated and compared using a commercial vehicle model that was experimentally validated. Early results shows that a parameter identification approach is more accurate, whereas an observer-based approach is less sensible to parametric uncertainty.

  19. Investigations on Absorber Materials at Cryogenic Temperatures

    SciTech Connect

    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 variations from room temperature down to 2 K. Initial results are presented in this paper.

  20. Shock wave absorber having apertured plate

    DOEpatents

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

    1983-08-26

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  1. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Yong W.; Wiedermann, Arne H.; Ockert, Carl E.

    1985-01-01

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  2. Vibration absorber modeling for handheld machine tool

    NASA Astrophysics Data System (ADS)

    Abdullah, Mohd Azman; Mustafa, Mohd Muhyiddin; Jamil, Jazli Firdaus; Salim, Mohd Azli; Ramli, Faiz Redza

    2015-05-01

    Handheld machine tools produce continuous vibration to the users during operation. This vibration causes harmful effects to the health of users for repeated operations in a long period of time. In this paper, a dynamic vibration absorber (DVA) is designed and modeled to reduce the vibration generated by the handheld machine tool. Several designs and models of vibration absorbers with various stiffness properties are simulated, tested and optimized in order to diminish the vibration. Ordinary differential equation is used to derive and formulate the vibration phenomena in the machine tool with and without the DVA. The final transfer function of the DVA is later analyzed using commercial available mathematical software. The DVA with optimum properties of mass and stiffness is developed and applied on the actual handheld machine tool. The performance of the DVA is experimentally tested and validated by the final result of vibration reduction.

  3. Disposable Diaper Absorbency: Improvements via Advanced Designs.

    PubMed

    Helmes, C Tucker; O'Connor, Robert; Sawyer, Larry; Young, Sharon

    2014-08-01

    Absorbency effectiveness in diapers has improved significantly in recent years with the advent of new ingredient combinations and advanced design features. With these features, many leading products maintain their dryness performance overnight. Considering the importance of holding liquid away from the skin, ongoing research in diaper construction focuses on strategies to increase the effectiveness to capture liquid and help avoid rewetting of infant skin. The layout and design of a disposable diaper allows for distribution of absorbency features where they can provide the optimal benefit. Clinical evidence indicates materials can keep moisture away from the skin in the diapered area, helping maintain proper skin hydration, minimizing irritation, and contributing to reduced rates of diaper rash.

  4. Tech Transfer Webinar: Energy Absorbing Materials

    ScienceCinema

    Duoss, Eric

    2016-07-12

    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.

  5. Metamaterial Resonant Absorbers for Terahertz Sensing

    DTIC Science & Technology

    2015-12-01

    and their periodic nature , finite element (FE) modeling is the preferable means of designing metamaterials. In order to use metamaterials in sensors ...will incorporate the metamaterial absorber design of this research into a more efficient, cost effective, bi-material THz sensor that can be employed...in a variety of naval applications. 14. SUBJECT TERMS terahertz sensors , metamaterials, uncooled detectors 15. NUMBER OF PAGES 73 16

  6. Lightweight Energy Absorbers for Blast Containers

    NASA Technical Reports Server (NTRS)

    Balles, Donald L.; Ingram, Thomas M.; Novak, Howard L.; Schricker, Albert F.

    2003-01-01

    Kinetic-energy-absorbing liners made of aluminum foam have been developed to replace solid lead liners in blast containers on the aft skirt of the solid rocket booster of the space shuttle. The blast containers are used to safely trap the debris from small explosions that are initiated at liftoff to sever frangible nuts on hold-down studs that secure the spacecraft to a mobile launch platform until liftoff.

  7. Design and Manufacture of Energy Absorbing Materials

    ScienceCinema

    Duoss, Eric

    2016-07-12

    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.

  8. Tech Transfer Webinar: Energy Absorbing Materials

    SciTech Connect

    Duoss, Eric

    2014-06-17

    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.

  9. Design and Manufacture of Energy Absorbing Materials

    SciTech Connect

    Duoss, Eric

    2014-05-28

    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.

  10. Hastings Center

    MedlinePlus

    ... on, and advocacy for, wiser health care and science policy. In addition to her leadership role at The Hastings Center, she is a professor at Harvard Medical School, where she directs the school’s Fellowship in Bioethics, a program that ...

  11. Shock wave absorber having a deformable liner

    DOEpatents

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

    1983-08-26

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

  12. COSMIC DUST IN Mg II ABSORBERS

    SciTech Connect

    Menard, Brice; Fukugita, Masataka

    2012-08-01

    Mg II absorbers induce reddening on background quasars. We measure this effect and infer the cosmic density of dust residing in these systems to be {Omega} Almost-Equal-To 2 Multiplication-Sign 10{sup -6}, in units of the critical density of the universe, which is comparable to the amount of dust found in galactic disks or about half the amount inferred to exist outside galaxies. We also estimate the neutral hydrogen abundance in Mg II clouds to be {Omega} Almost-Equal-To 1.5 Multiplication-Sign 10{sup -4}, which is approximately 5% of hydrogen in stars in galaxies. This implies a dust-to-gas mass ratio for Mg II clouds of about 1/100, which is similar to the value for normal galaxies. This would support the hypothesis of the outflow origin of Mg II clouds, which are intrinsically devoid of stars and hence have no sources of dust. Considerations of the dust abundance imply that the presence of Mg II absorbers around galaxies lasts effectively for a few Gyr. High-redshift absorbers allow us to measure the rest-frame extinction curve to 900 A, at which the absorption by the Lyman edge dominates over scattering by dust in the extinction opacity.

  13. Heaving buoys, point absorbers and arrays.

    PubMed

    Falnes, Johannes; Hals, Jørgen

    2012-01-28

    Absorption of wave energy may be considered as a phenomenon of interference between incident and radiated waves generated by an oscillating object; a wave-energy converter (WEC) that displaces water. If a WEC is very small in comparison with one wavelength, it is classified as a point absorber (PA); otherwise, as a 'quasi-point absorber'. The latter may be a dipole-mode radiator, for instance an immersed body oscillating in the surge mode or pitch mode, while a PA is so small that it should preferably be a source-mode radiator, for instance a heaving semi-submerged buoy. The power take-off capacity, the WEC's maximum swept volume and preferably also its full physical volume should be reasonably matched to the wave climate. To discuss this matter, two different upper bounds for absorbed power are applied in a 'Budal diagram'. It appears that, for a single WEC unit, a power capacity of only about 0.3 MW matches well to a typical offshore wave climate, and the full physical volume has, unfortunately, to be significantly larger than the swept volume, unless phase control is used. An example of a phase-controlled PA is presented. For a sizeable wave-power plant, an array consisting of hundreds, or even thousands, of mass-produced WEC units is required.

  14. Load limiting energy absorbing lightweight debris catcher

    NASA Technical Reports Server (NTRS)

    Kahn, Jon B. (Inventor); Schneider, William C. (Inventor)

    1991-01-01

    In the representative embodiment of the invention disclosed, a load limiting, energy absorbing net is arranged to overlay a normally-covered vent opening in the rear bulkhead of the space orbiter vehicle. Spatially-disposed flexible retainer straps are extended from the net and respectively secured to bulkhead brackets spaced around the vent opening. The intermediate portions of the straps are doubled over and stitched together in a pattern enabling the doubled-over portions to progressively separate at a predicable load designed to be well below the tensile capability of the straps as the stitches are successively torn apart by the forces imposed on the retainer members whenever the cover plate is explosively separated from the bulkhead and propelled into the net. By arranging these stitches to be successively torn away at a load below the strap strength in response to forces acting on the retainers that are less than the combined strength of the retainers, this tearing action serves as a predictable compact energy absorber for safely halting the cover plate as the retainers are extended as the net is deployed. The invention further includes a block of an energy-absorbing material positioned in the net for receiving loose debris produced by the explosive release of the cover plate.

  15. Gallbladder perforation by absorbable spiral tacker

    PubMed Central

    Wirsching, A; Vonlanthen, R

    2014-01-01

    Introduction Mesh fixation with tacker systems is common in laparoscopic and open hernia repair. Complications due to absorbable tackers are rare and have not been described in the literature. However, we report a case of gallbladder erosion due to tacker dislocation. Methods An open hernia repair was performed using an intraperitoneal onlay mesh for a recurrent parastomal hernia after two previous mesh repairs in a 67-year-old patient. Results On postoperative day 2, the patient was reoperated because of a dislocated tacker that eroded and perforated the fundus region of the gallbladder. Putatively, tacker dislocation occurred owing to imbalanced traction forces. Initially, the mesh was fixed with absorbable tackers around the stoma on the right and transmuscular suture fixation was carried out on the left abdominal side. On revision surgery, tension forces to the right were therefore neutralised by additional transmuscular sutures on the right side. Conclusions Absorbable tackers in open hernia repair provide a safe and effective mesh fixation if tension forces are carefully avoided. PMID:25245719

  16. Development of monofilar rotor hub vibration absorber

    NASA Technical Reports Server (NTRS)

    Duh, J.; Miao, W.

    1983-01-01

    A design and ground test program was conducted to study the performance of the monofilar absorber for vibration reduction on a four-bladed helicopter. A monofilar is a centrifugal tuned two degree-of-freedom rotor hub absorber that provides force attenuation at two frequencies using the same dynamic mass. Linear and non-linear analyses of the coupled monofilar/airframe system were developed to study tuning and attenuation characteristics. Based on the analysis, a design was fabricated and impact bench tests verified the calculated non-rotating natural frequencies and mode shapes. Performance characteristics were measured using a rotating absorber test facility. These tests showed significant attenuation of fixed-system 4P hub motions due to 3P inplane rotating-system hub forces. In addition, detuning effects of the 3P monofilar modal response were small due to the nonlinearities and tuning pin slippage. However, attenuation of 4P hub motions due to 5P inplane hub forces was poor. The performance of the 5P monofilar modal response was degraded by torsional motion of the dynamic mass relative to the support arm which resulted in binding of the dynamic components. Analytical design studies were performed to evaluate this torsional motion problem. An alternative design is proposed which may alleviate the torsional motion of the dynamic mass.

  17. New Insight into the Angle Insensitivity of Ultrathin Planar Optical Absorbers for Broadband Solar Energy Harvesting.

    PubMed

    Liu, Dong; Yu, Haitong; Duan, Yuanyuan; Li, Qiang; Xuan, Yimin

    2016-09-01

    Two challenging problems still remain for optical absorbers consisting of an ultrathin planar semiconductor film on top of an opaque metallic substrate. One is the angle-insensitive mechanism and the other is the system design needed for broadband solar energy harvesting. Here, first we theoretically demonstrates that the high refractive index, instead of the ultrathin feature as reported in previous studies, is the physical origin of the angle insensitivity for ultrathin planar optical absorbers. They exhibit omnidirectional resonance for TE polarization due to the high complex refractive index difference between the semiconductor and the air, while for TM polarization the angle insensitivity persists up to an incident angle related to the semiconductor refractive index. These findings were validated by fabricating and characterizing an 18 nm Ge/Ag absorber sample (representative of small band gap semiconductors for photovoltaic applications) and a 22 nm hematite/Ag sample (representative of large band gap semiconductors for photoelectrochemical applications). Then, we took advantage of angle insensitivity and designed a spectrum splitting configuration for broadband solar energy harvesting. The cascaded solar cell and unassisted solar water splitting systems have photovoltaic and photoelectrochemical cells that are also spectrum splitters, so an external spectrum splitting element is not needed.

  18. New Insight into the Angle Insensitivity of Ultrathin Planar Optical Absorbers for Broadband Solar Energy Harvesting

    PubMed Central

    Liu, Dong; Yu, Haitong; Duan, Yuanyuan; Li, Qiang; Xuan, Yimin

    2016-01-01

    Two challenging problems still remain for optical absorbers consisting of an ultrathin planar semiconductor film on top of an opaque metallic substrate. One is the angle-insensitive mechanism and the other is the system design needed for broadband solar energy harvesting. Here, first we theoretically demonstrates that the high refractive index, instead of the ultrathin feature as reported in previous studies, is the physical origin of the angle insensitivity for ultrathin planar optical absorbers. They exhibit omnidirectional resonance for TE polarization due to the high complex refractive index difference between the semiconductor and the air, while for TM polarization the angle insensitivity persists up to an incident angle related to the semiconductor refractive index. These findings were validated by fabricating and characterizing an 18 nm Ge/Ag absorber sample (representative of small band gap semiconductors for photovoltaic applications) and a 22 nm hematite/Ag sample (representative of large band gap semiconductors for photoelectrochemical applications). Then, we took advantage of angle insensitivity and designed a spectrum splitting configuration for broadband solar energy harvesting. The cascaded solar cell and unassisted solar water splitting systems have photovoltaic and photoelectrochemical cells that are also spectrum splitters, so an external spectrum splitting element is not needed. PMID:27582317

  19. New Insight into the Angle Insensitivity of Ultrathin Planar Optical Absorbers for Broadband Solar Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Liu, Dong; Yu, Haitong; Duan, Yuanyuan; Li, Qiang; Xuan, Yimin

    2016-09-01

    Two challenging problems still remain for optical absorbers consisting of an ultrathin planar semiconductor film on top of an opaque metallic substrate. One is the angle-insensitive mechanism and the other is the system design needed for broadband solar energy harvesting. Here, first we theoretically demonstrates that the high refractive index, instead of the ultrathin feature as reported in previous studies, is the physical origin of the angle insensitivity for ultrathin planar optical absorbers. They exhibit omnidirectional resonance for TE polarization due to the high complex refractive index difference between the semiconductor and the air, while for TM polarization the angle insensitivity persists up to an incident angle related to the semiconductor refractive index. These findings were validated by fabricating and characterizing an 18 nm Ge/Ag absorber sample (representative of small band gap semiconductors for photovoltaic applications) and a 22 nm hematite/Ag sample (representative of large band gap semiconductors for photoelectrochemical applications). Then, we took advantage of angle insensitivity and designed a spectrum splitting configuration for broadband solar energy harvesting. The cascaded solar cell and unassisted solar water splitting systems have photovoltaic and photoelectrochemical cells that are also spectrum splitters, so an external spectrum splitting element is not needed.

  20. Dual-band photon sorting plasmonic MIM metamaterial sensor

    NASA Astrophysics Data System (ADS)

    Jung, Young Uk; Bendoym, Igor; Golovin, Andrii B.; Crouse, David T.

    2014-06-01

    We propose plasmonic metal-insulator-metal (MIM) metamaterial designs for the sensing of two infrared wavelength bands, the mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) band by using a photon sorting technique. The proposed structures can capture light effectively on the metasurfaces based on coupling of free space energy to a subwavelength plasmonic mode. Photon sorting can be performed such that the incident light with a broad spectrum upon the metasurfaces can be "split" according to wavelength, channeling different spectral bands to different physical regions of the array on the surface where it is then absorbed by the insulator. Two different structures described in this work are (1) Square-type structure which consists of MIM resonators being periodically arranged to form a polarization independent sensor and (2) Meander-type structure which consists of MIM resonators being connected to form the meander shaped sensor. Mercury Cadmium Telluride (HgCdTe) posts are used as absorbing material within the MIM structure to generate free carriers and allow for collection of carrier charges. The proposed structures have compact designs and exhibit efficient light splitting and absorption for the IR spectral band. Structural and material properties, the electric field distribution and Poynting vector fields at the resonance frequencies are provided. Applications include thermal imaging, night vision systems, rifle sights, missile detection and discrimination, dual bandwidth optical filters, light trapping, and electromagnetically induced transparency.

  1. Comment on "Size-efficient metamaterial absorber at low frequencies: Design, fabrication, and characterization" [J. Appl. Phys. 117, 243105 (2015)

    NASA Astrophysics Data System (ADS)

    Liu, Lulu; Liu, Shaobin; Zhang, HaiFeng; Kong, Xiangkun; Yang, Hua; Ding, Guowen; Xu, Ce; Wang, Lingling; Shi, Wei

    2016-06-01

    In a recent article, Khuyen et al. [J. Appl. Phys. 117, 243105 (2015)] proposed a metamaterial perfect absorber (MPA) with a self-asymmetric structure and claimed that it could produce dual-band "perfect absorption." In this report, we demonstrate that the self-asymmetric structure is not a true MPA. The cross-polarization reflection, which is induced by coupling between the induced magnetic field and the incident electric field, is ignored in calculation of absorptivity of that structure. The real absorption rate of this structure is below 60%, which indicates that the structure cannot be called a perfect absorber.

  2. Banded electromagnetic stator core

    DOEpatents

    Fanning, Alan W.; Gonzales, Aaron A.; Patel, Mahadeo R.; Olich, Eugene E.

    1996-01-01

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups.

  3. Banded electromagnetic stator core

    DOEpatents

    Fanning, A.W.; Gonzales, A.A.; Patel, M.R.; Olich, E.E.

    1994-04-05

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups. 5 figures.

  4. Banded electromagnetic stator core

    DOEpatents

    Fanning, Alan W.; Gonzales, Aaron A.; Patel, Mahadeo R.; Olich, Eugene E.

    1994-01-01

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups.

  5. Banded electromagnetic stator core

    DOEpatents

    Fanning, A.W.; Gonzales, A.A.; Patel, M.R.; Olich, E.E.

    1996-06-11

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups. 5 figs.

  6. Wideband S Band Transmitter

    DTIC Science & Technology

    1989-10-01

    the phase variations across a +/-I nanosecond compressed pulse . During experimentation in the RADC Module Evaluation Lab the paired echos could be...22 4-11. Pulsing Interlock ....................................... 23 4-12. Pulse Fault Detector and Fault Summary...band transmitter was built by RCA Corporation under contract F30602-78-C-0122, titled "Wideband Amplifier, P/O Digitally Coded Radar’. After use by

  7. Micromechanics of shear banding

    SciTech Connect

    Gilman, J.J.

    1992-08-01

    Shear-banding is one of many instabilities observed during the plastic flow of solids. It is a consequence of the dislocation mechanism which makes plastic flow fundamentally inhomogeneous, and is exacerbated by local adiabatic heating. Dislocation lines tend to be clustered on sets of neighboring glide planes because they are heterogeneously generated; especially through the Koehler multiple-cross-glide mechanism. Factors that influence their mobilities also play a role. Strain-hardening decreases the mobilities within shear bands thereby tending to spread (delocalize) them. Strain-softening has the inverse effect. This paper reviews the micro-mechanisms of these phenomena. It will be shown that heat production is also a consequence of the heterogeneous nature of the microscopic flow, and that dislocation dipoles play an important role. They are often not directly observable, but their presence may be inferred from changes in thermal conductivity. It is argued that after deformation at low temperatures dipoles are distributed a la Pareto so there are many more small than large ones. Instability at upper yield point, the shapes of shear-band fronts, and mechanism of heat generation are also considered. It is shown that strain-rate acceleration plays a more important role than strain-rate itself in adiabatic instability.

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

    SciTech Connect

    Huang, Xianjun; Hu, Zhirun; Liu, Peiguo

    2014-11-15

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

  9. Selective Pyroelectric Detection of Millimetre Waves Using Ultra-Thin Metasurface Absorbers

    PubMed Central

    Kuznetsov, Sergei A.; Paulish, Andrey G.; Navarro-Cía, Miguel; Arzhannikov, Andrey V.

    2016-01-01

    Sensing infrared radiation is done inexpensively with pyroelectric detectors that generate a temporary voltage when they are heated by the incident infrared radiation. Unfortunately the performance of these detectors deteriorates for longer wavelengths, leaving the detection of, for instance, millimetre-wave radiation to expensive approaches. We propose here a simple and effective method to enhance pyroelectric detection of the millimetre-wave radiation by combining a compact commercial infrared pyro-sensor with a metasurface-enabled ultra-thin absorber, which provides spectrally- and polarization-discriminated response and is 136 times thinner than the operating wavelength. It is demonstrated that, due to the small thickness and therefore the thermal capacity of the absorber, the detector keeps the high response speed and sensitivity to millimetre waves as the original infrared pyro-sensor does against the regime of infrared detection. An in-depth electromagnetic analysis of the ultra-thin resonant absorbers along with their complex characterization by a BWO-spectroscopy technique is presented. Built upon this initial study, integrated metasurface absorber pyroelectric sensors are implemented and tested experimentally, showing high sensitivity and very fast response to millimetre-wave radiation. The proposed approach paves the way for creating highly-efficient inexpensive compact sensors for spectro-polarimetric applications in the millimetre-wave and terahertz bands. PMID:26879250

  10. Experimental demonstration of a transparent graphene millimetre wave absorber with 28% fractional bandwidth at 140 GHz

    PubMed Central

    Wu, Bian; Tuncer, Hatice M.; Naeem, Majid; Yang, Bin; Cole, Matthew T.; Milne, William I.; Hao, Yang

    2014-01-01

    The development of transparent radio-frequency electronics has been limited, until recently, by the lack of suitable materials. Naturally thin and transparent graphene may lead to disruptive innovations in such applications. Here, we realize optically transparent broadband absorbers operating in the millimetre wave regime achieved by stacking graphene bearing quartz substrates on a ground plate. Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate. An analytical model has been developed to predict the absorption performance and the angular dependence of the absorber. Using a repeated transfer-and-etch process, multilayer graphene was processed to control its surface resistivity. Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125–165 GHz. Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance. PMID:24549254

  11. Selective Pyroelectric Detection of Millimetre Waves Using Ultra-Thin Metasurface Absorbers

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Sergei A.; Paulish, Andrey G.; Navarro-Cía, Miguel; Arzhannikov, Andrey V.

    2016-02-01

    Sensing infrared radiation is done inexpensively with pyroelectric detectors that generate a temporary voltage when they are heated by the incident infrared radiation. Unfortunately the performance of these detectors deteriorates for longer wavelengths, leaving the detection of, for instance, millimetre-wave radiation to expensive approaches. We propose here a simple and effective method to enhance pyroelectric detection of the millimetre-wave radiation by combining a compact commercial infrared pyro-sensor with a metasurface-enabled ultra-thin absorber, which provides spectrally- and polarization-discriminated response and is 136 times thinner than the operating wavelength. It is demonstrated that, due to the small thickness and therefore the thermal capacity of the absorber, the detector keeps the high response speed and sensitivity to millimetre waves as the original infrared pyro-sensor does against the regime of infrared detection. An in-depth electromagnetic analysis of the ultra-thin resonant absorbers along with their complex characterization by a BWO-spectroscopy technique is presented. Built upon this initial study, integrated metasurface absorber pyroelectric sensors are implemented and tested experimentally, showing high sensitivity and very fast response to millimetre-wave radiation. The proposed approach paves the way for creating highly-efficient inexpensive compact sensors for spectro-polarimetric applications in the millimetre-wave and terahertz bands.

  12. Development of 4-Pixel-Array TES Microcalorimeters with Mushroom-Shaped Absorbers with Insulating Layers Supporting Overhang Regions

    NASA Astrophysics Data System (ADS)

    Maehata, K.; Iyomoto, N.; Maeda, M.; Ezaki, S.; Takano, A.; Matsumura, S.; Hara, T.; Mitsuda, K.; Yamasaki, N. Y.; Tanaka, K.

    2014-08-01

    A four-pixel-array superconducting transition-edge sensor (TES) microcalorimeter with a mushroom-shaped absorber was developed for energy dispersive spectroscopy performed on a transmission electron microscope. The TES consists of a bilayer of Au/Ti with either a 120- or 50-nm thickness. The absorber is made from a Au layer and its stem is deposited in the center of the TES surface. A TaO insulating layer of 100-nm thickness is inserted between the overhang region of the absorber and the TES surface. Two types of microcalorimeter were fabricated with differing absorber thicknesses of 0.5 and 5.0 m. An energy resolution of 15 eV FWHM with 5.9-keV X-rays was obtained using the 0.5-m-type microcalorimeter.

  13. Modeling the Effect of Polychromatic Light in Quantitative Absorbance Spectroscopy

    ERIC Educational Resources Information Center

    Smith, Rachel; Cantrell, Kevin

    2007-01-01

    Laboratory experiment is conducted to give the students practical experience with the principles of electronic absorbance spectroscopy. This straightforward approach creates a powerful tool for exploring many of the aspects of quantitative absorbance spectroscopy.

  14. Spectrophotometry of Thin Films of Light-Absorbing Particles.

    PubMed

    Binks, Bernard P; Fletcher, Paul D I; Johnson, Andrew J; Marinopoulos, Ioannis; Crowther, Jonathan M; Thompson, Michael A

    2017-04-06

    Thin films of dispersions of light-absorbing solid particles or emulsions containing a light-absorbing solute all have a nonuniform distribution of light-absorbing species throughout the sample volume. This results in nonuniform light absorption over the illuminated area, which causes the optical absorbance, as measured using a conventional specular UV-vis spectrophotometer, to deviate from the Beer-Lambert relationship. We have developed a theoretical model to account for the absorbance properties of such films, which are shown to depend on the size and volume fraction of the light-absorbing particles plus other sample variables. We have compared model predictions with measured spectra for samples consisting of emulsions containing a dissolved light-absorbing solute. Using no adjustable parameters, the model successfully predicts the behavior of nonuniform, light-absorbing emulsion films with varying values of droplet size, volume fraction, and other parameters.

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

    SciTech Connect

    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 without vias engineered as proposed by Luukkonen et al.. Unique values for the dielectric loss are required for different center frequencies. Parameters for the capacitive grid are D=5.0 mm and w=O.l mm for a center frequency of 3.36 GHz. The relative permittivity and thickness is 9.20(1-j0.234) and 1=3.048 mm. Consider a center frequency of5.81 GHz and again 1=3.048 mm, the required parameters for the capacitive grid are D=2.0 mm and w=0.2 mm where the required relative permittivity is now 9.20(1-j0.371) Admittedly, engineered dielectrics are themselves a historically interesting and fruitful research area which benefits today from advances in monolithic fabrication using direct-write of dielectrics with nanometer scale inclusions. However, our objective in the present study is to realize the advantages of the absorber proposed by Luukkonen et al. without resort to engineered lossy dielectrics. Specifically we are restricted to commercially available planer circuit materials without use of in-house direct-write technology or materials engineering capability. The materials considered here are TMM 10 laminate with (35 {mu}lm copper cladding with a complex permittivity 9.20-j0.0022) and Ohmegaply resistor conductor material (maximum 250 {Omega

  16. Resolving the forbidden band of SF6.

    PubMed

    Boudon, V; Manceron, L; Kwabia Tchana, F; Loëte, M; Lago, L; Roy, P

    2014-01-28

    Sulfur hexafluoride is an important molecule for modeling thermophysical and polarizability properties. It is also a potent greenhouse gas of anthropogenic origin, whose concentration in the atmosphere, although very low is increasing rapidly; its global warming power is mostly conferred by its strong infrared absorption in the ν3 S-F stretching region near 948 cm(-1). This heavy species, however, features many hot bands at room temperature (at which only 31% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v6 = 1 vibrational state. Unfortunately, the ν6 band itself (near 347 cm(-1)), in the first approximation, is both infrared- and Raman-inactive, and no reliable spectroscopic information could be obtained up to now and this has precluded a correct modeling of the hot bands. It has been suggested theoretically and experimentally that this band might be slightly activated through Coriolis interaction with infrared-active fundamentals and appears in high pressure measurements as a very faint, unresolved band. Using a new cryogenic multipass cell with 93 m optical path length and regulated at 163 ± 2 K temperature, coupled to synchrotron radiation and a high resolution interferometer, the spectrum of the ν6 far-infrared region has been recorded. Low temperature was used to avoid the presence of hot bands. We are thus able to confirm that the small feature in this region, previously viewed at low-resolution, is indeed ν6. The fully resolved spectrum has been analyzed, thanks to the XTDS software package. The band appears to be activated by faint Coriolis interactions with the strong ν3 and ν4 fundamental bands, resulting in the appearance of a small first-order dipole moment term, inducing unusual selection rules. The band center (ν6 = 347.736707(35) cm(-1)) and rovibrational parameters are now accurately determined for the v6 = 1 level. The ν6 perturbation-induced dipole moment is estimated to be 33 ± 3

  17. Band crossing in a shears band of {sup 108}Cd

    SciTech Connect

    Roy, Santosh; Datta, Pradip; Pal, S.; Chattopadhyay, S.; Bhattacharya, S.; Goswami, A.; Jain, H. C.; Joshi, P. K.; Bhowmik, R. K.; Kumar, R.; Muralithar, S.; Singh, R. P.; Madhavan, N.; Rao, P. V. Madhusudhana

    2010-05-15

    The level lifetimes have been measured for a shears band of {sup 108}Cd that exhibits band crossing. The observed level energies and B(M1) rates have been successfully described by a semiclassical geometric model based on shear mechanism. In this geometric model, the band crossing in the shears band has been described as the reopening of the angle between the blades of a shear.

  18. Effect of inclusions' distribution on microwave absorbing properties of composites

    NASA Astrophysics Data System (ADS)

    Qin, Siliang; Wang, Qingguo; Qu, Zhaoming

    2013-03-01

    Effect of inclusions' spatial distributions on the permeability and permittivity of composites is studied using the generalized Maxwell-Garnett equations. The result indicates that inclusions' orientation distribution can increase the longitudinal electromagnetic parameters. For inclusions' random and orientation distribution, single and three-layer absorbers are designed and optimized using genetic algorithm. The result shows that under a given absorbing requirement, absorber with inclusions' orientation distribution is lighter and thinner than absorber with inclusions' random distribution.

  19. Method for absorbing an ion from a fluid

    DOEpatents

    Gao, Huizhen; Wang, Yifeng; Bryan, Charles R.

    2007-07-03

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

  20. Dynamic testing of airplane shock-absorbing struts

    NASA Technical Reports Server (NTRS)

    Langer, P; Thome, W

    1932-01-01

    Measurement of perpendicular impacts of a landing gear with different shock-absorbing struts against the drum testing stand. Tests were made with pneumatic shock absorbers having various degrees of damping, liquid shock absorbers, steel-spring shock absorbers and rigid struts. Falling tests and rolling tests. Maximum impact and gradual reduction of the impacts in number and time in the falling tests. Maximum impact and number of weaker impacts in rolling tests.