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Sample records for spaced sublimation technique

  1. Hg1-xCdxTe vapor deposition on CdZnTe substrates by Closed Space Sublimation technique

    NASA Astrophysics Data System (ADS)

    Rubio, Sandra; Sochinskii, Nikolai V.; Repiso, Eva; Tsybrii, Zinoviia; Sizov, Fiodor; Plaza, Jose Luis; Diéguez, Ernesto

    2017-01-01

    Closed Space Sublimation (CSS) technique has been studied to deposit Hg1-xCdxTe polycrystalline films on CdZnTe substrates at the improved pressure-temperature conditions. The experimental results on film characterization suggest that the CSS optimal conditions are the argon atmospheric pressure (1013 mbar) and the deposition temperature in the range of 500-550 °C. These conditions provide macro-defect free Hg1-xCdxTe films with the uniform size and surface distribution of polycrystals.

  2. Enhanced performance of CdS/CdTe thin-film devices through temperature profiling techniques applied to close-spaced sublimation deposition

    SciTech Connect

    Xiaonan Li; Sheldon, P.; Moutinho, H.; Matson, R.

    1996-05-01

    The authors describe a methodology developed and applied to the close-spaced sublimation technique for thin-film CdTe deposition. The developed temperature profiles consisted of three discrete temperature segments, which the authors called the nucleation, plugging, and annealing temperatures. They have demonstrated that these temperature profiles can be used to grow large-grain material, plug pinholes, and improve CdS/CdTe photovoltaic device performance by about 15%. The improved material and device properties have been obtained while maintaining deposition temperatures compatible with commercially available substrates. This temperature profiling technique can be easily applied to a manufacturing environment by adjusting the temperature as a function of substrate position instead of time.

  3. Optimization of Fast Dissolving Etoricoxib Tablets Prepared by Sublimation Technique

    PubMed Central

    Patel, D. M.; Patel, M. M.

    2008-01-01

    The purpose of this investigation was to develop fast dissolving tablets of etoricoxib. Granules containing etoricoxib, menthol, crospovidone, aspartame and mannitol were prepared by wet granulation technique. Menthol was sublimed from the granules by exposing the granules to vacuum. The porous granules were then compressed in to tablets. Alternatively, tablets were first prepared and later exposed to vacuum. The tablets were evaluated for percentage friability and disintegration time. A 32 full factorial design was applied to investigate the combined effect of 2 formulation variables: amount of menthol and crospovidone. The results of multiple regression analysis indicated that for obtaining fast dissolving tablets; optimum amount of menthol and higher percentage of crospovidone should be used. A surface response plots are also presented to graphically represent the effect of the independent variables on the percentage friability and disintegration time. The validity of a generated mathematical model was tested by preparing a checkpoint batch. Sublimation of menthol from tablets resulted in rapid disintegration as compared with the tablets prepared from granules that were exposed to vacuum. The optimized tablet formulation was compared with conventional marketed tablets for percentage drug dissolved in 30 min (Q30) and dissolution efficiency after 30 min (DE30). From the results, it was concluded that fast dissolving tablets with improved etoricoxib dissolution could be prepared by sublimation of tablets containing suitable subliming agent. PMID:20390084

  4. Determination of surface shear stress with the naphthalene sublimation technique

    NASA Technical Reports Server (NTRS)

    Lee, J. A.; Greeley, Ronald

    1987-01-01

    Aeolian entrainment and transport are functions of surface shear stress and particle characteristics. Measuring surface shear stress is difficult, however, where logarithmic wind profiles are not found, such as regions around large roughness elements. An outline of a method whereby shear stress can be mapped on the surface around an object is presented. The technique involves the sublimation of naphthalene (C10H8) which is a function of surface shear stress and surface temperature. This technique is based on the assumption that the transfer of momentum, heat and mass are analogous (Reynolds analogy). If the Reynolds analogy can be shown to be correct for a given situation, then knowledge of the diffusion of one property allows the determination of the others. The analytical framework and data acquisition for the method are described. The technique was tested in the Planetary Geology Wind Tunnel. Results show that the naphthalene sublimation technique is a reasonably accurate method for determining shear stress, particularly around objects where numerous point values are needed.

  5. Possibility of graphene growth by close space sublimation.

    PubMed

    Sopinskyy, Mykola V; Khomchenko, Viktoriya S; Strelchuk, Viktor V; Nikolenko, Andrii S; Olchovyk, Genadiy P; Vishnyak, Volodymyr V; Stonis, Viktor V

    2014-04-14

    Carbon films on the Si/SiO2 substrate are fabricated using modified method of close space sublimation at atmospheric pressure. The film properties have been characterized by micro-Raman and X-ray photoelectron spectroscopy and monochromatic ellipsometry methods. Ellipsometrical measurements demonstrated an increase of the silicon oxide film thickness in the course of manufacturing process. The XPS survey spectra of the as-prepared samples indicate that the main elements in the near-surface region are carbon, silicon, and oxygen. The narrow-scan spectra of C1s, Si2p, O1s regions indicate that silicon and oxygen are mainly in the SiOx (x ≈ 2) oxide form, whereas the main component of C1s spectrum at 284.4 eV comes from the sp2-hybridized carbon phase. Micro-Raman spectra confirmed the formation of graphene films with the number of layers that depended on the distance between the graphite source and substrate.

  6. Arrays of widely spaced atomic steps on Si(1 1 1) mesas due to sublimation

    NASA Astrophysics Data System (ADS)

    Chang, Kee-Chul; Blakely, Jack M.

    2005-10-01

    Steps with spacings of microns form on top of mesas fabricated on Si(1 1 1) that is annealed at temperatures where sublimation becomes important. Upon annealing, mesas first develop ridges along their edges, effectively creating craters which then become step-free by a step flow process described in the literature [S. Tanaka, C.C. Umbach, J.M. Blakely, R.M. Tromp, M. Mankos, Appl. Phys. Lett. 69 (9) (1996) 1235; Y. Homma, N. Aizawa, T. Ogino, Jpn. J. Appl. Phys. 35 (2B) (1996) L241]. Due to the miscut of the average surface from (1 1 1), ridge breakdown occurs on one edge of each mesa as sublimation proceeds. The breakdown point then acts as a source of steps which spread out over the mesa surface. The distribution of steps in the resulting step train depends on the sublimation rate, direct step-step interaction and the diffusive exchange of atoms among the steps. Insight into the role of these processes on the self-organization of the wide terrace distributions is provided by computer simulations using BCF (Burton, Cabrera and Frank) theory. This shows that step spacing can be controlled by varying the annealing temperature and the deposition flux. Comparison of the experimental and predicted step distributions suggest that the dynamics of the widely spaced steps are sublimation limited.

  7. Deposition of ZnTe thin films by close spaced sublimation: Structural and electrical studies

    SciTech Connect

    Goyal, D.J.; Bilurkar, P.G.; Thorat, S.K.; Mate, N.V.

    1998-12-31

    Zinc telluride has the potential of being a low-cost, environmentally stable, low-resistance and easily manufacturable back contact for CdS/CdTe solar cells. Close Spaced Sublimation (CSS) technique is used to deposit thin films of ZnTe. The results are reported in this study. The effects of substrate temperature and film thickness on the structural properties of the deposited thin films are studied. X-ray diffractograms show that all the films prominently exhibit presence of (111) and (200) orientations. However, the degree of the preferred orientation changes as a function of the film thickness. Increase in film thickness reduces the preferential orientation. The as deposited ZnTe thin films, being that of p-type semiconductor, are highly resistive. In order to effectively use these as contact to CdS/CdTe solar cells, they are made more conductive by doping copper. The doping is effected by dipping the films in alcoholic solution of copper chloride, followed by air annealing at 200 C. The resistivity of all the doped films drops drastically in the initial 10 minutes of annealing. The extent of doping is controlled by varying the dipping time. The effects of substrate temperature, film thickness and doping, on the stoichiometry of the films, are studied using Atomic Absorption Spectroscopy (AAS).

  8. CdZnS thin films sublimated by closed space using mechanical mixing: A new approach

    NASA Astrophysics Data System (ADS)

    Mahmood, Waqar; Shah, Nazar Abbas

    2014-06-01

    Cadmium sulfide (CdS) is a prominent material for its tunable band gap used as a window layer in II-VI semiconductor solar cells. The light trapping capability of window layer is one of the powerful tools to enhance the efficiency of the cell. CdS and zinc (Zn) powders were mixed mechanically with different weight percents to make CdZnS (CZS) powder. CZS was deposited onto an ultrasonically cleaned glass substrate using close spaced sublimation (CSS) technique. CZS as-deposited thin films were characterized for structural, surface morphology with energy dispersive X-rays (EDX) and optical properties for the use of window layer in CdS/CdTe based solar cells. The different Zn concentrations in CZS played a vital role on crystallite size in structural analysis and optical properties e.g. transmission, absorption coefficient and energy band gap, etc. The crystallite size of as-deposited CZS thin films were increased as Zn concentration was increased up to certain value. The energy band gap varies from 2.42 eV to 2.57 eV for as-deposited CZS thin films with increasing Zn concentrations and surface morphology changes also. These changes were occurred due to zinc diffusion in CdS thin films. An angle resolved transmission data was taken to check the behavior of CdS and CZS thin film at different angles. A comparative study was carried out between CdS thin films and CZS thin films for the use of good window layer material.

  9. Induced Recrystallization of CdTe Thin Films Deposited by Close-Spaced Sublimation

    SciTech Connect

    Moutinho, H. R.; Dhere, R. G.; Al-Jassim, M. M.; Levi, D. H.; Kazmerski, L. L.; Mayo, B.

    1998-10-26

    We have deposited CdTe thin films by close-spaced sublimation at two different temperature ranges. The films deposited at the lower temperature partially recrystallized after CdCl2 treatment at 350 C and completely recrystallized after the same treatment at 400 C. The films deposited at higher temperature did not recrystallize at these two temperatures. These results confirmed that the mechanisms responsible for changes in physical properties of CdTe films treated with CdCl2 are recrystallization and grain growth, and provided an alternative method to deposit CSS films using lower temperatures.

  10. Novel Strategy to Fabricate Floating Drug Delivery System Based on Sublimation Technique.

    PubMed

    Huanbutta, Kampanart; Limmatvapirat, Sontaya; Sungthongjeen, Srisagul; Sriamornsak, Pornsak

    2016-06-01

    The present study aims to develop floating drug delivery system by sublimation of ammonium carbonate (AMC). The core tablets contain a model drug, hydrochlorothiazide, and various levels (i.e., 0-50% w/w) of AMC. The tablets were then coated with different amounts of the polyacrylate polymers (i.e., Eudragit® RL100, Eudragit® RS100, and the mixture of Eudragit® RL100 and Eudragit® RS100 at 1:1 ratio). The coated tablets were kept at ambient temperature (25°C) or cured at 70°C for 12 h before further investigation. The floating and drug release behaviors of the tablets were performed in simulated gastric fluid USP without pepsin at 37°C. The results showed that high amount of AMC induced the floating of the tablets. The coated tablets containing 40 and 50% AMC floated longer than 8 h with a time-to-float of about 3 min. The sublimation of AMC from the core tablets decreased the density of system, causing floating of the tablets. The tablets coated with Eudragit® RL100 floated at a faster rate than those of Eudragit® RS100. Even the coating level of polymer did not influence the time-to-float and floating time of coated tablets containing the same amount of AMC, the drug release from the tablets coated with higher coating level of polymer showed slower drug release. The results suggested that the sublimation technique using AMC is promising for the development of floating drug delivery system.

  11. [Research on the polycrystalline CdS thin films prepared by close-spaced sublimation].

    PubMed

    Yang, Ding-Yu; Xia, Geng-Pei; Zheng, Jia-Gui; Feng, Liang-Huan; Cai, Ya-Ping

    2009-01-01

    In the present paper, the factors of influence on the deposition rate of CdS films prepared by close-spaced sublimation (CSS) were first studied systematically, and it was found from the experiments that the deposition rate increased with the raised temperature of sublimation source, while decreased with the raised substrate temperature and the deposition pressure. The structure, morphology and light transmittance of the prepared samples were tested subsequently, and the results show: (1) The CdS films deposited under different oxygen partial pressure all present predominating growth lattice orientation (103), and further more the films will be strengthened after annealed under CdCl2 atmosphere. (2) The AFM images of CdS show that the films are compact and uniform in grain diameter, and the grain size becomes larger with the increased substrate temperature. Along with it, the film roughness was also augmented. (3) The transmittance in the shortwave region of visible light through the CdS films would be enhanced when its thickness is reduced, and that will help improve the shortwave spectral response of CdTe solar cells. Finally, the prepared CdS films were employed to fabricate CdTe solar cells, which have achieved a conversion efficiency of 10.29%, and thus the feasibility of CSS process in the manufacture of CdTe solar cells was validated primarily.

  12. Cadmium sulfide thin films deposited by close spaced sublimation and cadmium sulfide/cadmium telluride solar cells

    NASA Astrophysics Data System (ADS)

    Marinskiy, Dmitriy Nikolaevich

    1998-12-01

    One of the applications of CdS films is as a window layer in CdTe and Cu(In,Ga)Sesb2 solar cells. The study of the optical and structural properties of CdS films deposited by close spaced sublimation as well as their influence on CdS/CdTe solar cell performance is part of the CdTe solar cell program at the University of South Florida. CdS films have been deposited by the close-spaced sublimation technique. The influence of the main process parameters, the substrate and source temperatures, and the ambient in the deposition chamber has been investigated. As-deposited films have been subjected to heat treatments in Hsb2 ambient, in CdClsb2 atmosphere, and in atmosphere with small amounts of oxygen. A special annealing chamber was built to carry out the annealing experiments in the presence of CdClsb2 vapor and oxygen. Several CSS chambers were assembled to study the influence of various process parameters simultaneously and validate the results. Results of scanning electron microscopy and photoluminescence measurements have been used as the primary characterization techniques. X-ray diffraction, electron microprobe analysis, and transmission measurements have also been carried out. It was found that as deposited CdS films have a hexagonal structure independent of the process parameters used. The presence of a CdO phase was detected in the samples grown with the highest oxygen concentration in the ambient. The resistivity of CdS films is controlled by intergrain barriers. Photoluminescence measurements showed the presence of oxygen-acceptor transition and a wide variation in the intensity of deep emission bands. The variation in the intensities was correlated with the variation in the deposition and annealing conditions. However, no correlation was found between the PL intensities of defect bands and cell performance. CdS/CdTe junctions have been fabricated using standard deposition and postgrowth techniques developed in the USF solar cells laboratory. All cells have

  13. In-Situ Growth of Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Opila, Elizabeth J.; Nathal, Michael V.

    2012-01-01

    The compound Yb14MnSb11 is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 C in the vacuum of space. Although Yb14MnSb11 shows the potential to double the value of the thermoelectric figure of merit (zT) over that of Si-Ge at 1000 C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of the present work is to measure the sublimation rate of Yb14MnSb11 and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb14MnSb11 at 1000 C (approximately 3 x 10(exp -3) grams per square centimeter hour) and efforts to reduce the sublimation rate with an in situ grown Yb2O3 layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb14MnSb11, the scales did not prove to be sublimation barriers.

  14. The role of oxygen in CdS/CdTe solar cells deposited by close-spaced sublimation

    SciTech Connect

    Rose, D.H.; Levi, D.H.; Matson, R.J.

    1996-05-01

    The presence of oxygen during close-spaced sublimation (CSS) of CdTe has been previously reported to be essential for high-efficiency CdS/CdTe solar cells because it increases the acceptor density in the absorber. The authors find that the presence of oxygen during CSS increases the nucleation site density of CdTe, thus decreasing pinhole density and grain size. Photoluminescence showed that oxygen decreases material quality in the bulk of the CdTe film, but positively impacts the critical CdS/CdTe interface. Through device characterization the authors were unable to verify an increase in acceptor density with increased oxygen. These results, along with the achievement of high-efficiency cells (13% AM1.5) without the use of oxygen, led the authors to conclude that the use of oxygen during CSS deposition of CdTe can be useful but is not essential.

  15. In-Space Propulsion Engine Architecture Based on Sublimation of Planetary Resources: From Exploration Robots to NED Mitigation

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Mantovani, James G.

    2011-01-01

    Volatile solids occur naturally on most planetary bodies including the Moon, Mars, asteroids and comets. Examples of recent discoveries include water ice, frozen carbon dioxide and hydrocarbons. The ability to utilize readily available resources for in-space propulsion and for powering surface systems during a planetary mission will help minimize the overall cost and extend the op.erational life of a mission. The utilization of volatile solids to achieve these goals is attractive for its simplicity. We have investigated the potential of subliming in situ volatiles and silicate minerals to power propulsion engines for a wide range of in-space applications where environmental conditions are favorable. This paper addresses the' practicality of using planetary solid volatiles as a power source for propulsion and surface systems by presenting results of modeling involving thermodynamic and physical mechanics calculations, and laboratory testing to measure the thrust obtained from ,a volatile solid engine (VSE). Applications of a VSE for planetary exploration are discussed as a means for propulsion and for mechanical actuators and surface mobility platforms.

  16. 12% efficient CdTe/CdS thin film solar cells deposited by low-temperature close space sublimation

    NASA Astrophysics Data System (ADS)

    Schaffner, Judith; Motzko, Markus; Tueschen, Alexander; Swirschuk, Andreas; Schimper, Hermann-Josef; Klein, Andreas; Modes, Thomas; Zywitzki, Olaf; Jaegermann, Wolfram

    2011-09-01

    We report 12% efficient CdS/CdTe thin film solar cells prepared by low temperature close space sublimation (CSS). Both semiconductor films, CdS and CdTe, were deposited by high vacuum CSS in superstrate configuration on glass substrates with fluorine doped tin oxide (FTO) front contact. The CdTe deposition was carried out at a substrate temperature (Tsub) of ≤340 ∘C, which is much lower than that used in conventional processes (>500 ∘C). The CdTe films were treated with the usual CdCl2 activation process. Different optimal annealing times and temperatures were found for low-temperature cells (Tsub≤ 340 ∘C) compared to high-temperature cells (Tsub = 520 ∘C). The influence of the activation step on the morphology of high-temperature and low-temperature CdTe is determined by XRD, AFM, SEM top views, and SEM cross-sections. Grain growth, strong recrystallization, and a reduction of planar defects during the activation step are observed, especially for low-temperature CdTe. Further, the influence of CdS deposition parameters on the solar cell performance is investigated by using three different sets of parameters with different deposition rates and substrate temperatures for the CdS preparation. Efficiencies about 10.9% with a copper-free back contact and 12.0% with a copper-containing back contact were achieved using the low temperature CdTe process.

  17. Characterization of CdMnTe films deposited from polycrystalline powder source using closed-space sublimation method

    SciTech Connect

    Lai, Jianming; Wang, Junnan; Wang, Lin; Ji, Huanhuan; Xu, Run; Zhang, Jijun; Huang, Jian; Shen, Yue; Min, Jiahua; Wang, Linjun Xia, Yiben

    2015-09-15

    CdMnTe films were prepared on quartz substrates by closed-space sublimation of polycrystalline Cd{sub 0.74}Mn{sub 0.26}Te powders. This was performed at different substrate temperatures (T{sub s} = 200, 300, 350, and 400 °C). The interfacial adhesion strength between the films and substrates, when fabricated from polycrystalline powders, was greater than that of films grown using a bulk source. X-ray diffraction studies revealed that the as-deposited films had a zinc blende structure with a preferential (111) orientation. Precipitation of Te occurred in the films deposited at T{sub s} = 200 °C, as confirmed using scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. The growth mode and re-evaporation dependence on the value of T{sub s} of the films were investigated. Our results suggested that materials suitable for radiation detection can be grown from a powder source at lower substrate temperatures then when grown from a bulk source.

  18. Sublimation-assisted graphene transfer technique based on small polyaromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Chen, Mingguang; Stekovic, Dejan; Li, Wangxiang; Arkook, Bassim; Haddon, Robert C.; Bekyarova, Elena

    2017-06-01

    Advances in the chemical vapor deposition (CVD) growth of graphene have made this material a very attractive candidate for a number of applications including transparent conductors, electronics, optoeletronics, biomedical devices and energy storage. The CVD method requires transfer of graphene on a desired substrate and this is most commonly accomplished with polymers. The removal of polymer carriers is achieved with organic solvents or thermal treatment which makes this approach inappropriate for application to plastic thin films such as polyethylene terephthalate substrates. An ultraclean graphene transfer method under mild conditions is highly desired. In this article, we report a naphthalene-assisted graphene transfer technique which provides a reliable route to residue-free transfer of graphene to both hard and flexible substrates. The quality of the transferred graphene was characterized with atomic force microscopy, scanning electron microscopy, and Raman spectroscopy. Field effect transistors, based on the naphthalene-transfered graphene, were fabricated and characterized. This work has the potential to broaden the applications of CVD graphene in fields where ultraclean graphene and mild graphene transfer conditions are required.

  19. A sublimation heat engine.

    PubMed

    Wells, Gary G; Ledesma-Aguilar, Rodrigo; McHale, Glen; Sefiane, Khellil

    2015-03-03

    Heat engines are based on the physical realization of a thermodynamic cycle, most famously the liquid-vapour Rankine cycle used for steam engines. Here we present a sublimation heat engine, which can convert temperature differences into mechanical work via the Leidenfrost effect. Through controlled experiments, quantified by a hydrodynamic model, we show that levitating dry-ice blocks rotate on hot turbine-like surfaces at a rate controlled by the turbine geometry, temperature difference and solid material properties. The rotational motion of the dry-ice loads is converted into electric power by coupling to a magnetic coil system. We extend our concept to liquid loads, generalizing the realization of the new engine to both sublimation and the instantaneous vapourization of liquids. Our results support the feasibility of low-friction in situ energy harvesting from both liquids and ices. Our concept is potentially relevant in challenging situations such as deep drilling, outer space exploration or micro-mechanical manipulation.

  20. A sublimation heat engine

    NASA Astrophysics Data System (ADS)

    Wells, Gary G.; Ledesma-Aguilar, Rodrigo; McHale, Glen; Sefiane, Khellil

    2015-03-01

    Heat engines are based on the physical realization of a thermodynamic cycle, most famously the liquid-vapour Rankine cycle used for steam engines. Here we present a sublimation heat engine, which can convert temperature differences into mechanical work via the Leidenfrost effect. Through controlled experiments, quantified by a hydrodynamic model, we show that levitating dry-ice blocks rotate on hot turbine-like surfaces at a rate controlled by the turbine geometry, temperature difference and solid material properties. The rotational motion of the dry-ice loads is converted into electric power by coupling to a magnetic coil system. We extend our concept to liquid loads, generalizing the realization of the new engine to both sublimation and the instantaneous vapourization of liquids. Our results support the feasibility of low-friction in situ energy harvesting from both liquids and ices. Our concept is potentially relevant in challenging situations such as deep drilling, outer space exploration or micro-mechanical manipulation.

  1. The Sublime and Education

    ERIC Educational Resources Information Center

    Carson, Jamin

    2006-01-01

    The sublime is a theory of aesthetics that reached its highest popularity in British literature during the Romantic period (c. 1785-1832). This article (1) explicates philosophers' different meanings of the sublime; (2) show how the sublime is relevant to education; and (3) show how the sublime "works" in literature by analyzing William Blake's…

  2. The Sublime and Education

    ERIC Educational Resources Information Center

    Carson, Jamin

    2006-01-01

    The sublime is a theory of aesthetics that reached its highest popularity in British literature during the Romantic period (c. 1785-1832). This article (1) explicates philosophers' different meanings of the sublime; (2) show how the sublime is relevant to education; and (3) show how the sublime "works" in literature by analyzing William Blake's…

  3. First-order feasibility analysis of a space suit radiator concept based on estimation of water mass sublimation using Apollo mission data

    NASA Astrophysics Data System (ADS)

    Metts, Jonathan G.; Klaus, David M.

    2012-01-01

    Thermal control of a space suit during extravehicular activity (EVA) is typically accomplished by sublimating water to provide system cooling. Spacecraft, on the other hand, primarily rely on radiators to dissipate heat. Integrating a radiator into a space suit has been proposed as an alternative design that does not require mass consumption for heat transfer. While providing cooling without water loss offers potential benefits for EVA application, it is not currently practical to rely on a directional, fixed-emissivity radiator to maintain thermal equilibrium of a spacesuit where the radiator orientation, environmental temperature, and crew member metabolic heat load fluctuate unpredictably. One approach that might make this feasible, however, is the use of electrochromic devices that are capable of infrared emissivity modulation and can be actively controlled across the entire suit surface to regulate net heat flux for the system. Integrating these devices onto the irregular, compliant space suit material requires that they be fabricated on a flexible substrate, such as Kapton film. An initial assessment of whether or not this candidate technology presents a feasible design option was conducted by first characterizing the mass of water loss from sublimation that could theoretically be saved if an electrochromic suit radiator was employed for thermal control. This is particularly important for lunar surface exploration, where the expense of transporting water from Earth is excessive, but the technology is potentially beneficial for other space missions as well. In order to define a baseline for this analysis by comparison to actual data, historical documents from the Apollo missions were mined for comprehensive, detailed metabolic data from each lunar surface outing, and related data from NASA's more recent "Advanced Lunar Walkback" tests were also analyzed. This metabolic database was then used to validate estimates for sublimator water consumption during surface

  4. A close-space sublimation driven pathway for the manipulation of substrate-supported micro- and nanostructures

    NASA Astrophysics Data System (ADS)

    Sundar, Aarthi

    The ability to fabricate structures and engineer materials on the nanoscale leads to the development of new devices and the study of exciting phenomena. Nanostructures attached to the surface of a substrate, in a manner that renders them immobile, have numerous potential applications in a diverse number of areas. Substrate-supported nanostructures can be fabricated using numerous modalities; however the easiest and most inexpensive technique to create a large area of randomly distributed particles is by the technique of thermal dewetting. In this process a metastable thin film is deposited at room temperature and heated, causing the film to lower its surface energy by agglomerating into droplet-like nanostructures. The main drawbacks of nanostructure fabrication via this technique are the substantial size distributions realized and the lack of control over nanostructure placement. In this doctoral dissertation, a new pathway for imposing order onto the thermal dewetting process and for manipulating the size, placement, shape and composition of preformed templates is described. It sees the confinement of substrate-supported thin films or nanostructure templates by the free surface of a metal film or a second substrate surface. Confining the templates in this manner and heating them to elevated temperatures leads to changes in the characteristics of the nanostructures formed. Three different modalities are demonstrated which alters the preformed structures by: (i) subtracting atoms from the templates, (ii) adding atoms to the template or (iii) simultaneously adding and subtracting atoms. The ability to carry out such processes depends on the choice of the confining surface and the nanostructured templates used. A subtractive process occurs when an electroformed nickel mesh is placed in conformal contact with a continuous gold film while it dewets, resulting in the formation of a periodic array of gold microstructures on an oxide substrate surface. When heated the

  5. A sublimation heat engine

    PubMed Central

    Wells, Gary G.; Ledesma-Aguilar, Rodrigo; McHale, Glen; Sefiane, Khellil

    2015-01-01

    Heat engines are based on the physical realization of a thermodynamic cycle, most famously the liquid–vapour Rankine cycle used for steam engines. Here we present a sublimation heat engine, which can convert temperature differences into mechanical work via the Leidenfrost effect. Through controlled experiments, quantified by a hydrodynamic model, we show that levitating dry-ice blocks rotate on hot turbine-like surfaces at a rate controlled by the turbine geometry, temperature difference and solid material properties. The rotational motion of the dry-ice loads is converted into electric power by coupling to a magnetic coil system. We extend our concept to liquid loads, generalizing the realization of the new engine to both sublimation and the instantaneous vapourization of liquids. Our results support the feasibility of low-friction in situ energy harvesting from both liquids and ices. Our concept is potentially relevant in challenging situations such as deep drilling, outer space exploration or micro-mechanical manipulation. PMID:25731669

  6. Transport phenomena in the close-spaced sublimation deposition process for manufacture of large-area cadmium telluride photovoltaic panels: Modeling and optimization

    NASA Astrophysics Data System (ADS)

    Malhotra, C. P.

    With increasing national and global demand for energy and concerns about the effect of fossil fuels on global climate change, there is an increasing emphasis on the development and use of renewable sources of energy. Solar cells or photovoltaics constitute an important renewable energy technology but the major impediment to their widespread adoption has been their high initial cost. Although thin-film photovoltaic semiconductors such as cadmium sulfide-cadmium telluride (CdS/CdTe) can potentially be inexpensively manufactured using large area deposition techniques such as close-spaced sublimation (CSS), their low stability has prevented them from becoming an alternative to traditional polycrystalline silicon solar cells. A key factor affecting the stability of CdS/CdTe cells is the uniformity of deposition of the thin films. Currently no models exist that can relate the processing parameters in a CSS setup with the film deposition uniformity. Central to the development of these models is a fundamental understanding of the complex transport phenomena which constitute the deposition process which include coupled conduction and radiation as well as transition regime rarefied gas flow. This thesis is aimed at filling these knowledge gaps and thereby leading to the development of the relevant models. The specific process under consideration is the CSS setup developed by the Materials Engineering Group at the Colorado State University (CSU). Initially, a 3-D radiation-conduction model of a single processing station was developed using the commercial finite-element software ABAQUS and validated against data from steady-state experiments carried out at CSU. A simplified model was then optimized for maximizing the steady-state thermal uniformity within the substrate. It was inferred that contrary to traditional top and bottom infrared lamp heating, a lamp configuration that directs heat from the periphery of the sources towards the center results in the minimum temperature

  7. The effect of substrate temperature on material properties and the device performance of close-spaced sublimation deposited CdTe/CdS devices

    NASA Astrophysics Data System (ADS)

    Li, X.; Albin, D.; Asher, S.; Moutinho, H.; Keyes, B.; Matson, R.; Hasoon, F.; Sheldon, P.

    1996-01-01

    High-efficiency polycrystalline CdS/CdTe solar cells have been fabricated using CdTe absorber layers deposited by close-spaced sublimation (CSS). CSS employs high substrate temperatures (Tsub) during film growth, which can promote the formation of larger grains and higher Voc's yielding better device performance. However, as Tsub increases beyond 610 °C, voids or pinholes begin to form in the CdTe layer. When the back contact is applied, these voids serve as shunt paths that effectively lower Voc. In this fashion, benefits associated with higher substrate temperatures are seriously compromised. Concurrent with voiding is the observation that higher temperatures promote interdiffusion at the CdS/CdTe interface such that the effective thickness of the CdS layer is reduced. Variations in processing that correct for these detrimental effects have led to a total-area device efficiency of 12%.

  8. Heat rejection sublimator

    NASA Technical Reports Server (NTRS)

    Dingell, Charles W. (Inventor); Quintana, Clemente E. (Inventor); Le, Suy (Inventor); Clark, Michael R. (Inventor); Cloutier, Robert E. (Inventor); Hafermalz, David Scott (Inventor)

    2009-01-01

    A sublimator includes a sublimation plate having a thermal element disposed adjacent to a feed water channel and a control point disposed between at least a portion of the thermal element and a large pore substrate. The control point includes a sintered metal material. A method of dissipating heat using a sublimator includes a sublimation plate having a thermal element and a control point. The thermal element is disposed adjacent to a feed water channel and the control point is disposed between at least a portion of the thermal element and a large pore substrate. The method includes controlling a flow rate of feed water to the large pore substrate at the control point and supplying heated coolant to the thermal element. Sublimation occurs in the large pore substrate and the controlling of the flow rate of feed water is independent of time. A sublimator includes a sublimation plate having a thermal element disposed adjacent to a feed water channel and a control point disposed between at least a portion of the thermal element and a large pore substrate. The control point restricts a flow rate of feed water from the feed water channel to the large pore substrate independent of time.

  9. Ultrasound Techniques for Space Applications

    NASA Technical Reports Server (NTRS)

    Rooney, James A.

    1985-01-01

    Ultrasound has proven to be a safe non-invasive technique for imaging organs and measuring cardiovascular function. It has unique advantages for application to problems with man in space including evaluation of cardiovascular function both in serial studies and during critical operations. In addition, specialized instrumentation may be capable of detecting the onset of decompression sickness during EVA activities. A spatial location and three-dimensional reconstruction system is being developed to improve the accuracy and reproducibility for serial comparative ultrasound studies of cardiovascular function. The three-dimensional method permits the acquisition of ultrasonic images from many views that can be recombined into a single reconstruction of the heart or vasculature. In addition to conventional imaging and monitoring systems, it is sometimes necessary or desirable to develop instrumentation for special purposes. One example of this type of development is the design of a pulsed-Doppler system to monitor cerebral blood flow during critical operations such as re-entry. A second example is the design of a swept-frequency ultrasound system for the detection of bubbles in the circulatory system and/or soft tissues as an early indication of the onset of decompression sickness during EVA activities. This system exploits the resonant properties of bubbles and can detect both fundamental and second harmonic emissions from the insonified region.

  10. Ultrasound Techniques for Space Applications

    NASA Technical Reports Server (NTRS)

    Rooney, James A.

    1985-01-01

    Ultrasound has proven to be a safe non-invasive technique for imaging organs and measuring cardiovascular function. It has unique advantages for application to problems with man in space including evaluation of cardiovascular function both in serial studies and during critical operations. In addition, specialized instrumentation may be capable of detecting the onset of decompression sickness during EVA activities. A spatial location and three-dimensional reconstruction system is being developed to improve the accuracy and reproducibility for serial comparative ultrasound studies of cardiovascular function. The three-dimensional method permits the acquisition of ultrasonic images from many views that can be recombined into a single reconstruction of the heart or vasculature. In addition to conventional imaging and monitoring systems, it is sometimes necessary or desirable to develop instrumentation for special purposes. One example of this type of development is the design of a pulsed-Doppler system to monitor cerebral blood flow during critical operations such as re-entry. A second example is the design of a swept-frequency ultrasound system for the detection of bubbles in the circulatory system and/or soft tissues as an early indication of the onset of decompression sickness during EVA activities. This system exploits the resonant properties of bubbles and can detect both fundamental and second harmonic emissions from the insonified region.

  11. Experimental Investigation of Transient Sublimator Performance

    NASA Technical Reports Server (NTRS)

    Sheth, Rubik B.; Stephan, Ryan A.; Leimkuehler, Thomas O.

    2012-01-01

    Sublimators have been used as heat rejection devices for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Sublimators typically operate with steady-state feedwater utilization at or near 100%. However, sublimators are currently being considered for operations in a cyclical topping mode, which represents a new mode of operation for sublimators. Sublimators can be used as a supplemental heat rejection device during mission phases where the environmental temperature or heat rejection requirement changes rapidly. This scenario may occur during low lunar orbit, low earth orbit, or other planetary orbits. In these mission phases, the need for supplemental heat rejection will vary between zero and some fraction of the overall heat load. In particular, supplemental heat rejection is required for the portion of the orbit where the radiative sink temperature exceeds the system setpoint temperature. This paper will describe the effects of these transient starts and stops on the feedwater utilization during various feedwater timing scenarios. Experimental data from various scenarios is analyzed to investigate feedwater consumption efficiency under the cyclical conditions. Start up utilization tests were conducted to better understand the transient performance. This paper also provides recommendations for future sublimator design and transient operation.

  12. Coating Thermoelectric Devices To Suppress Sublimation

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeffrey; Caillat, Thierry; Fleurial, Jean-Pierre; Snyder, G. Jeffrey

    2007-01-01

    A technique for suppressing sublimation of key elements from skutterudite compounds in advanced thermoelectric devices has been demonstrated. The essence of the technique is to cover what would otherwise be the exposed skutterudite surface of such a device with a thin, continuous film of a chemically and physically compatible metal. Although similar to other sublimation-suppression techniques, this technique has been specifically tailored for application to skutterudite antimonides. The primary cause of deterioration of most thermoelectric materials is thermal decomposition or sublimation - one or more elements sublime from the hot side of a thermoelectric couple, changing the stoichiometry of the device. Examples of elements that sublime from their respective thermoelectric materials are Ge from SiGe, Te from Pb/Te, and now Sb from skutterudite antimonides. The skutterudite antimonides of primary interest are CoSb3 [electron-donor (n) type] and CeFe(3-x)Co(x)Sb12 [electron-acceptor (p) type]. When these compounds are subjected to typical operating conditions [temperature of 700 C and pressure <10(exp -5) torr (0.0013 Pa)], Sb sublimes from their surfaces, with the result that Sb depletion layers form and advance toward their interiors. As the depletion layer advances in a given device, the change in stoichiometry diminishes the thermal-to-electric conversion efficiency of the device. The problem, then, is to prevent sublimation, or at least reduce it to an acceptably low level. In preparation for an experiment on suppression of sublimation, a specimen of CoSb3 was tightly wrapped in a foil of niobium, which was selected for its chemical stability. In the experiment, the wrapped specimen was heated to a temperature of 700 C in a vacuum of residual pressure <10(exp -5) torr (0.0013 Pa), then cooled and sectioned. Examination of the sectioned specimen revealed that no depletion layer had formed, indicating the niobium foil prevented sublimation of antimony at 700 C

  13. Structural and optical properties of AgAlTe{sub 2} layers grown on sapphire substrates by closed space sublimation method

    SciTech Connect

    Uruno, A. Usui, A.; Kobayashi, M.

    2014-11-14

    AgAlTe{sub 2} layers were grown on a- and c-plane sapphire substrates using a closed space sublimation method. Grown layers were confirmed to be single phase layers of AgAlTe{sub 2} by X-ray diffraction. AgAlTe{sub 2} layers were grown to have a strong preference for the (112) orientation on both kinds of substrates. The variation in the orientation of grown layers was analyzed in detail using the X-ray diffraction pole figure measurement, which revealed that the AgAlTe{sub 2} had a preferential epitaxial relationship with the c-plane sapphire substrate. The atomic arrangement between the (112) AgAlTe{sub 2} layer and sapphire substrates was compared. It was considered that the high order of the lattice arrangement symmetry probably effectively accommodated the lattice mismatch. The optical properties of the grown layer were also evaluated by transmittance measurements. The bandgap energy was found to be around 2.3 eV, which was in agreement with the theoretical bandgap energy of AgAlTe{sub 2}.

  14. Comparison study of close-spaced sublimated and chemical bath deposited CdS films: Effects on CdTe solar cells

    SciTech Connect

    Albin, D.; Rose, D.; Dhere, R.; Levi, D.; Woods, L.; Swartzlander, A.; Sheldon, P.

    1997-12-31

    Close-spaced-sublimated (CSS) CdS films exhibit strong fundamental edge luminescence, high optical absorption, and a bandgap of {approximately}2.41 eV. Structurally, these films show good crystallinity with thickness-dependent grain sizes that vary between 100--400 nm. In contrast, chemical-bath, deposited (CBD) CdS exhibits subband luminescence, lower absorption, and a thickness-dependent bandgap. These films have CdS grains typically less than 50 nm in size and poorer crystallinity. However, CdTe devices fabricated with these lower quality CBD CdS films yield higher V{sub oc}`s and fill factors. Carrier lifetimes in finished CSS CdS devices measured between 100 and 200 ps while lifetimes in CBD CdS devices were much higher (>500 ps). Compositional differences in the Cd/(S+Te) ratio at the interface suggest the possibility of lower CdS doping and higher CdTe compensation as one reason for lower V{sub oc}`s in CSS CdS devices.

  15. Experimental Investigation of Sublimator Performance at Transient Heat Loads

    NASA Technical Reports Server (NTRS)

    Sheth, Rubik B.; Stephen, Ryan A.; Leimkuehler, Thomas O.

    2011-01-01

    Sublimators have been used as heat rejection devices for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Sublimators typically operate with steady-state feedwater utilization at or near 100%. However, sublimators are currently being considered to operate in a cyclical topping mode, which represents a new mode of operation for sublimators. Sublimators can be used as a topper during mission phases such as low lunar or low earth orbit. In these mission phases, the sublimator will be repeatedly started and stopped during each orbit to provide supplemental heat rejection for the portion of the orbit where the radiative sink temperature exceeds the system setpoint temperature. This paper will summarize the effort put into understanding sublimator response under a transient heat load. The performance will be assessed by detailing the changes in feedwater utilization due to transient starts and stops during various feedwater timing scenarios. Sublimator start up utilization will be assessed as a possible relationship to transient performance of a sublimator. This paper will also provide recommendations for future sublimator designs and/or feedwater control.

  16. Modular Porous Plate Sublimator /MPPS/ requires only water supply for coolant

    NASA Technical Reports Server (NTRS)

    Rathbun, R. J.

    1966-01-01

    Modular porous plate sublimators, provided for each location where heat must be dissipated, conserve the battery power of a space vehicle by eliminating the coolant pump. The sublimator requires only a water supply for coolant.

  17. In-Space Propulsion Engine Architecture Based on Sublimation of Planetary Resources: From Exploration Robots to NED Mitigation

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Mantovani, James; Dominquez, Jesus

    2011-01-01

    The purpose of this NIAC study is to identify those volatile and mineral resources that are available on asteroids, comets, moons and planets in the solar system, and investigate methods to transform these resources into forms of power that will expand the capabilities of future robotic and human exploration missions to explore planetary bodies beyond the Moon and will mitigate hazards from NEOs. The sources of power used for deep space probe missions are usually derived from either solar panels for electrical energy, radioisotope thermal generators for thermal energy, or fuel cells and chemical reactions for chemical energy and propulsion.

  18. [Spectral analyzing effects of atmosphere states on the structure and characteristics of CdTe polycrystalline thin films made by close-spaced sublimation].

    PubMed

    Zheng, Hua-jing; Zheng, Jia-gui; Feng, Liang-huan; Zhang, Jing-quan; Xie, Er-qing

    2005-07-01

    The structure and characteristics of CdTe thin films are dependent on the working atmosphere states in close-spaced sublimation. In the present paper, CdTe polycrystalline thin films were deposited by CSS in mixture atmosphere of argon and oxygen. The physical mechanism of CSS was analyzed, and the temperature distribution in CSS system was measured. The dependence of preliminary nucleus creation on the atmosphere states (involving component and pressure) was studied. Transparencies were measured and optic energy gaps were calculated. The results show that: (1) The CdTe films deposited in different atmospheres are cubic structure. With increasing oxygen concentration, a increases and reaches the maximum at 6% oxygen concentration, then reduces, and increases again after passing the point at 12% oxygen concentration. Among them, the sample depositing at 9% oxygen concentration is the best. The optic energy gaps are 1.50-1.51 eV for all CdTe films. (2) The samples depositing at different pressures at 9% oxygen concentration are all cubical structure of CdTe, and the diffraction peaks of CdS and SnO2:F still appear. With the gas pressure increasing, the crystal size of CdTe minishes, the transparency of the thin film goes down, and the absorption side shifts to the short-wave direction. (3) The polycrystalline thin films with high quality deposit in 4 minutes under the depositing condition that the substrate temperature is 550 degrees C, and source temperature is 620 degrees C at 9% oxygen concentration.

  19. EPR techniques for space biodosimetry

    SciTech Connect

    Haskell, E.; Hayes, R.; Kenner, G.; Sholom, S.; Chumak, V.

    1996-12-31

    Retrospective dosimetry of tooth enamel has become an increasingly complex and difficult discipline to undertake while still attaining accuracy. The paper provides a review of the major obstacles, advances and pertinent phenomenon associated with low level retrospective dosimetry of human tooth enamel. Also covered is the many sources of error in EPR dosimetry, their potential solutions, as well as the different analysis and scanning techniques in use with their prospective pros and cons. Prospective directions for new approaches, methods, and instruments are also reviewed.

  20. FPGAs in Space Environment and Design Techniques

    NASA Technical Reports Server (NTRS)

    Katz, Richard B.; Day, John H. (Technical Monitor)

    2001-01-01

    This viewgraph presentation gives an overview of Field Programmable Gate Arrays (FPGA) in the space environment and design techniques. Details are given on the effects of the space radiation environment, total radiation dose, single event upset, single event latchup, single event transient, antifuse technology and gate rupture, proton upsets and sensitivity, and loss of functionality.

  1. Optical Measurement Technique for Space Column Characterization

    NASA Technical Reports Server (NTRS)

    Barrows, Danny A.; Watson, Judith J.; Burner, Alpheus W.; Phelps, James E.

    2004-01-01

    A simple optical technique for the structural characterization of lightweight space columns is presented. The technique is useful for determining the coefficient of thermal expansion during cool down as well as the induced strain during tension and compression testing. The technique is based upon object-to-image plane scaling and does not require any photogrammetric calibrations or computations. Examples of the measurement of the coefficient of thermal expansion are presented for several lightweight space columns. Examples of strain measured during tension and compression testing are presented along with comparisons to results obtained with Linear Variable Differential Transformer (LVDT) position transducers.

  2. Prediction Techniques in Operational Space Weather Forecasting

    NASA Astrophysics Data System (ADS)

    Zhukov, Andrei

    2016-07-01

    The importance of forecasting space weather conditions is steadily increasing as our society is becoming more and more dependent on advanced technologies that may be affected by disturbed space weather. Operational space weather forecasting is still a difficult task that requires the real-time availability of input data and specific prediction techniques that are reviewed in this presentation, with an emphasis on solar and interplanetary weather. Key observations that are essential for operational space weather forecasting are listed. Predictions made on the base of empirical and statistical methods, as well as physical models, are described. Their validation, accuracy, and limitations are discussed in the context of operational forecasting. Several important problems in the scientific basis of predicting space weather are described, and possible ways to overcome them are discussed, including novel space-borne observations that could be available in future.

  3. Tethered propellant resupply technique for space stations

    NASA Technical Reports Server (NTRS)

    Kroll, K. R.

    1984-01-01

    One of the primary functions of the space station is related to the propellant resupply of orbital transfer vehicles, orbital maneuvering vehicles, and satellites. Difficulties arise in the case of an acquisition of cryogenic propellants by means of a use of zero-gravity techniques. The use of the 'tethered propellant resupply technique' is, therefore, considered. A study is being conducted to determine the feasibility, design requirements, and operational limitations of this technique. Attention is given to aspects of gravity feed, transfer method selection, requirements related to the orbital transfer vehicle, hazard clearance, attitude control, depot operations, end mass velocity, the microgravity laboratory, and concept evaluation activities.

  4. Techniques for Measuring Surface Potentials in Space

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Parker, Linda Neergaard

    2015-01-01

    Materials exposed to the space plasma environment charge to a net potential relative to the ambient plasma. The charging process is due to differential currents to the material surface that results in a net surface charge density. While this process is termed "spacecraft surface charging" when applied to aerospace hardware, it also applies to the surfaces of astronomical objects in direct contact with the space plasma environment including a number of planetary bodies, asteroids, and dust particles. The ability to measure surface potentials is important to many techniques used in conducting fundamental heliospheric science, spacecraft engineering operations, and space technology development activities. This presentation provides a survey of current technologies used to measure surface potentials of spacecraft and planetary bodies with examples of their application to space science and technology programs.

  5. EEG source analysis using space mapping techniques

    NASA Astrophysics Data System (ADS)

    Crevecoeur, G.; Hallez, H.; van Hese, P.; D'Asseler, Y.; Dupre, L.; van de Walle, R.

    2008-06-01

    The electroencephalogram (EEG) measures potential differences, generated by electrical activity in brain tissue, between scalp electrodes. The EEG potentials can be calculated by the quasi-static Poisson equation in a certain head model. It is well known that the electrical dipole (source) which best fits the measured EEG potentials is obtained by an inverse problem. The dipole parameters are obtained by finding the global minimum of the relative residual energy (RRE). For the first time, the space mapping technique (SM technique) is used for minimizing the RRE. The SM technique aims at aligning two different simulation models: a fine model, accurate but CPU-time expensive, and a coarse model, computationally fast but less accurate than the fine one. The coarse model is a semi-analytical model, the so-called three-shell concentric sphere model. The fine model numerically solves the Poisson equation in a realistic head model. If we use the aggressive space mapping (ASM) algorithm, the errors on the dipole location are too large. The hybrid aggressive space mapping (HASM) on the other hand has better convergence properties, yielding a reduction in dipole location errors. The computational effort of HASM is greater than ASM but smaller than using direct optimization techniques.

  6. Development and Testing of the Contaminant Insensitive Sublimator

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.; Westheimer, David T.

    2006-01-01

    Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Some of the attractive features of sublimators are that they are compact, lightweight, and self-regulating. One of the drawbacks of previous designs has been sensitivity to non-volatile contamination in the feedwater, which can clog relatively small pores (approx.3-6 microns) in the porous plates where ice forms and sublimates. A new design that is less sensitive to contaminants is being developed at the Johnson Space Center. This paper describes the design, fabrication, and testing of the Contaminant Insensitive Sublimator (CIS) Engineering Development Unit (EDU).

  7. Development and Testing of the Contaminant Insensitive Sublimator

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.

    2007-01-01

    Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Some of the attractive features of sublimators are that they are compact, lightweight, and self-regulating. One of the drawbacks of previous designs has been sensitivity to non-volatile contamination in the feedwater, which can clog relatively small pores (approx. 3-6 micrometers) in the porous plates where ice forms and sublimates. A new design that is less sensitive to contaminants is being developed at the Johnson Space Center (JSC). This paper describes the design, fabrication, and testing of the Contaminant Insensitive Sublimator (CIS) Engineering Development Unit (EDU).

  8. Development and Testing of the Contaminant Insensitive Sublimator

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.; Westheimer, David T.

    2006-01-01

    Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Some of the attractive features of sublimators are that they are compact, lightweight, and self-regulating. One of the drawbacks of previous designs has been sensitivity to non-volatile contamination in the feedwater, which can clog relatively small pores (approx.3-6 microns) in the porous plates where ice forms and sublimates. A new design that is less sensitive to contaminants is being developed at the Johnson Space Center. This paper describes the design, fabrication, and testing of the Contaminant Insensitive Sublimator (CIS) Engineering Development Unit (EDU).

  9. Development and Testing of the Contaminant Insensitive Sublimator

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.

    2007-01-01

    Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Some of the attractive features of sublimators are that they are compact, lightweight, and self-regulating. One of the drawbacks of previous designs has been sensitivity to non-volatile contamination in the feedwater, which can clog relatively small pores (approx. 3-6 micrometers) in the porous plates where ice forms and sublimates. A new design that is less sensitive to contaminants is being developed at the Johnson Space Center (JSC). This paper describes the design, fabrication, and testing of the Contaminant Insensitive Sublimator (CIS) Engineering Development Unit (EDU).

  10. Modelling Sublimation of Carbon Dioxide

    ERIC Educational Resources Information Center

    Winkel, Brian

    2012-01-01

    In this article, the author reports results in their efforts to model sublimation of carbon dioxide and the associated kinetics order and parameter estimation issues in their model. They have offered the reader two sets of data and several approaches to determine the rate of sublimation of a piece of solid dry ice. They presented several models…

  11. Modelling Sublimation of Carbon Dioxide

    ERIC Educational Resources Information Center

    Winkel, Brian

    2012-01-01

    In this article, the author reports results in their efforts to model sublimation of carbon dioxide and the associated kinetics order and parameter estimation issues in their model. They have offered the reader two sets of data and several approaches to determine the rate of sublimation of a piece of solid dry ice. They presented several models…

  12. Space flight operations communications phraseology and techniques

    NASA Technical Reports Server (NTRS)

    Noneman, S. R.

    1986-01-01

    Communications are a critical link in space flight operations. Specific communications phraseology and techniques have been developed to allow rapid and clear transfer of information. Communications will be clear and brief through the use of procedural words and phrases. Communications protocols standardize the required information transferred. The voicing of letters and numbers is discussed. The protocols used in air-to-ground communications are given. A glossary of communications terminology is presented in the appendix.

  13. Sublimation systems and associated methods

    DOEpatents

    Turner, Terry D.; McKellar, Michael G.; Wilding, Bruce M.

    2016-02-09

    A system for vaporizing and sublimating a slurry comprising a fluid including solid particles therein. The system includes a first heat exchanger configured to receive the fluid including solid particles and vaporize the fluid and a second heat exchanger configured to receive the vaporized fluid and solid particles and sublimate the solid particles. A method for vaporizing and sublimating a fluid including solid particles therein is also disclosed. The method includes feeding the fluid including solid particles to a first heat exchanger, vaporizing the fluid, feeding the vaporized fluid and solid particles to a second heat exchanger and sublimating the solid particles. In some embodiments the fluid including solid particles is liquid natural gas or methane including solid carbon dioxide particles.

  14. The Sublime and the Vulgar.

    ERIC Educational Resources Information Center

    Swann, Karen

    1990-01-01

    Explores how Edmund Burke's discourse on the sublime helps illuminate attacks on the vulgarization of culture (as typified by Allan Bloom), both for the presumedly "vulgar" reader and for the champions of high culture. (MG)

  15. High performance techniques for space mission scheduling

    NASA Technical Reports Server (NTRS)

    Smith, Stephen F.

    1994-01-01

    In this paper, we summarize current research at Carnegie Mellon University aimed at development of high performance techniques and tools for space mission scheduling. Similar to prior research in opportunistic scheduling, our approach assumes the use of dynamic analysis of problem constraints as a basis for heuristic focusing of problem solving search. This methodology, however, is grounded in representational assumptions more akin to those adopted in recent temporal planning research, and in a problem solving framework which similarly emphasizes constraint posting in an explicitly maintained solution constraint network. These more general representational assumptions are necessitated by the predominance of state-dependent constraints in space mission planning domains, and the consequent need to integrate resource allocation and plan synthesis processes. First, we review the space mission problems we have considered to date and indicate the results obtained in these application domains. Next, we summarize recent work in constraint posting scheduling procedures, which offer the promise of better future solutions to this class of problems.

  16. Infiltration of CdTe nano crystals into a ZnO wire vertical matrix by using the isothermal closed space technique

    NASA Astrophysics Data System (ADS)

    Larramendi, S.; Vaillant Roca, Lidice; Saint-Gregoire, Pierre; Ferraz Dias, Johnny; Behar, Moni

    2017-10-01

    A ZnO nanorod structure was grown by the hydrothermal method and interpenetrated with CdTe using the isothermal closed space sublimation technique. The obtained structure was studied by using the Rutherford backscattering spectrometry (RBS), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM). The X-ray Diffraction (XRD) technique confirmed the presence of CdTe nanocrystals (NCs) of very small size formed on the surface and in the interspaces between the ZnO nanorods. The RBS observations together with the SEM observations give information on the obtained structure. Finally the photoluminescence studies show a strong energy confinement effect on the grown CdTe NCs.

  17. MALDI Imaging of Lipids after Matrix Sublimation/Deposition

    PubMed Central

    Murphy, Robert C.; Hankin, Joseph A.; Barkley, Robert M.; Zemski Berry, Karin A.

    2011-01-01

    Mass spectrometric techniques have been developed to record mass spectra of biomolecules including lipids as they naturally exist within tissues and thereby permit the generation of images displaying the distribution of specific lipids in tissues, organs, and intact animals. These techniques are based on matrix-assisted laser desorption/ionization (MALDI) that requires matrix application onto the tissue surface prior to analysis. One technique of application that has recently shown significant advantages for lipid analysis is sublimation of matrix followed by vapor deposition directly onto the tissue. Explanations for enhanced sensitivity realized by sublimation/deposition related to sample temperature after a laser pulse and matrix crystal size are presented. Specific examples of sublimation/deposition in lipid imaging of various organs including brain, ocular tissue, and kidney are presented. PMID:21571091

  18. Space optical navigation techniques: an overview

    NASA Astrophysics Data System (ADS)

    Rebordão, J. M.

    2013-11-01

    Optical or vision-based navigation is an enabling technology for satellite autonomous navigation associated to different navigation approaches such as cruising, fly-by, terrain relative navigation, landing, rendezvous and docking between spacecrafts, rigidity of multi-satellite constellations. Since 2001, in many different ESA projects, the author and his team (at INETI and currently at FCUL) have been associated to most of the developments of the optical components of autonomous navigation, in cooperation with space primes or GNC subsystems suppliers. A unique experience related to seemingly simple photonic concepts associated to computational vision, photonic noises, camera tradeoffs and system concepts has emerged, and deserves a synthesis especially because some of these concepts are being implemented in the ESA Proba 3 mission and ESA is currently updating the technology in view of forthcoming planetary missions to Jupiter, Jupiter moons and asteroids. It is important to note that the US have already flown several missions relying on autonomous navigation and that NASA experience is at least one decade old. System approaches, sources of difficulty, some tradeoffs in both (and between) hardware and software, critical interface issues between the imaging and GNC (Guidance, Navigation and Control) subsystems, image processing techniques, utilization of apriori or to be estimated information, uncertainties, simulation of the imaging chain and non-cooperative environments will be addressed synthetically for both passive (optical) and active (lidar) systems.

  19. Enantioenrichment in sublimed amino acid mixtures.

    PubMed

    Viedma, Cristóbal; Ortiz, José E; de Torres, Trinidad; Cintas, Pedro

    2012-04-14

    A real amplification of an initial enantiomeric excess can be detected when two amino acids are sublimed at high temperature, even if one of the components is a racemic compound that does not convert into a conglomerate by sublimation.

  20. Displacement, Substitution, Sublimation: A Bibliography.

    ERIC Educational Resources Information Center

    Pedrini, D. T.; Pedrini, Bonnie C.

    Sigmund Freund worked with the mechanisms of displacement, substitution, and sublimation. These mechanisms have many similarities and have been studied diagnostically and therapeutically. Displacement and substitution seem to fit in well with phobias, hysterias, somatiyations, prejudices, and scapegoating. Phobias, prejudices, and scapegoating…

  1. Eisenhower and the American Sublime

    ERIC Educational Resources Information Center

    O'Gorman, Ned

    2008-01-01

    This essay presents Dwight D. Eisenhower's presidential rhetoric as an iteration of an American synecdochal sublime. Eisenhower's rhetoric sought to re-aim civic sight beyond corporeal objects to the nation's transcendental essence. This rhetoric is intimately connected to prevailing political anxieties and exigencies, especially the problem of…

  2. Eisenhower and the American Sublime

    ERIC Educational Resources Information Center

    O'Gorman, Ned

    2008-01-01

    This essay presents Dwight D. Eisenhower's presidential rhetoric as an iteration of an American synecdochal sublime. Eisenhower's rhetoric sought to re-aim civic sight beyond corporeal objects to the nation's transcendental essence. This rhetoric is intimately connected to prevailing political anxieties and exigencies, especially the problem of…

  3. Membrane evaporator/sublimator investigation

    NASA Technical Reports Server (NTRS)

    Elam, J.; Ruder, J.; Strumpf, H.

    1974-01-01

    Data are presented on a new evaporator/sublimator concept using a hollow fiber membrane unit with a high permeability to liquid water. The aim of the program was to obtain a more reliable, lightweight and simpler Extra Vehicular Life Support System (EVLSS) cooling concept than is currently being used.

  4. Matrix isolation sublimation: An apparatus for producing cryogenic beams of atoms and molecules

    NASA Astrophysics Data System (ADS)

    Sacramento, R. L.; Oliveira, A. N.; Alves, B. X.; Silva, B. A.; Li, M. S.; Wolff, W.; Cesar, C. L.

    2015-07-01

    We describe the apparatus to generate cryogenic beams of atoms and molecules based on matrix isolation sublimation. Isolation matrices of Ne and H2 are hosts for atomic and molecular species which are sublimated into vacuum at cryogenic temperatures. The resulting cryogenic beams are used for high-resolution laser spectroscopy. The technique also aims at loading atomic and molecular traps.

  5. Matrix isolation sublimation: An apparatus for producing cryogenic beams of atoms and molecules

    SciTech Connect

    Sacramento, R. L.; Alves, B. X.; Silva, B. A.; Wolff, W.; Cesar, C. L.; Oliveira, A. N.; Li, M. S.

    2015-07-15

    We describe the apparatus to generate cryogenic beams of atoms and molecules based on matrix isolation sublimation. Isolation matrices of Ne and H{sub 2} are hosts for atomic and molecular species which are sublimated into vacuum at cryogenic temperatures. The resulting cryogenic beams are used for high-resolution laser spectroscopy. The technique also aims at loading atomic and molecular traps.

  6. Matrix isolation sublimation: An apparatus for producing cryogenic beams of atoms and molecules.

    PubMed

    Sacramento, R L; Oliveira, A N; Alves, B X; Silva, B A; Li, M S; Wolff, W; Cesar, C L

    2015-07-01

    We describe the apparatus to generate cryogenic beams of atoms and molecules based on matrix isolation sublimation. Isolation matrices of Ne and H2 are hosts for atomic and molecular species which are sublimated into vacuum at cryogenic temperatures. The resulting cryogenic beams are used for high-resolution laser spectroscopy. The technique also aims at loading atomic and molecular traps.

  7. Space Simulation, 7th. [facilities and testing techniques

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Space simulation facilities and techniques are outlined that encompass thermal scale modeling, computerized simulations, reentry materials, spacecraft contamination, solar simulation, vacuum tests, and heat transfer studies.

  8. Sublimating grains model of cometary coma.

    NASA Astrophysics Data System (ADS)

    Faggi, S.; Tozzi, G. P.; Brucato, J. R.

    Billion years of space weathering produces a crust of organic matter (see e.g. Kanuchova et al. 2012) that will be released when a comet enter for the first time in the inner Solar System. New comets, coming form the Oort Colud at their first passage close to the Sun, are particularly important because they are not differentiated by the Solar radiation and they are supposed to have a large quantity of ice organic matter close to the surface. When a comet approach to the Sun, its activity is driven by the sublimation of these nucleus ices: if the heliocentric distances, R_H , is greater than 3 AU the sublimation of CO and CO_2 ices is the main source of comet activity, otherwise at shorter distances, the sublimation of water become the most important mechanism of activity. These gases, escaping from the nucleus, drag in the coma grains that can be refractory dust (silicates, carbon), water ice and/or organic ices. Oort comets at their first passage in the inner Solar System, should produce an halo of organic or water icy particles. Our group has been monitoring new, inbound, bright Oort comets (C/2011 F1, C/2012 S1, C/2012 K1, C/2013 V5, C/2012 F3, C/2013 US10, C/2013 X1) to search for these icy grains. The method consists in detecting the cloud of sublimating grains in the inner coma by using the Sigma Af function (Tozzi et al. 2007) directly from images. However this over-population of grains, beside the sublimation, can be also due to short time activity (outburst) or too big grains expanding at very slow velocity, as it has been found in comet 67P/C-G (Tozzi eta al, 2011, A&A, 531, 54). To disentangle between the phenomena it is necessary to monitor the comet both at short timescale, for the outbursts (by repeating the observations after few nights), and at long term (weeks-months). If the cloud does not expand with the decreasing of the heliocentric distance there is high probability that we are in presence of organic and/or water ice grains. We can disentangle

  9. Optical Techniques for Space Environment Management

    NASA Astrophysics Data System (ADS)

    Greene, B.; Bennett, J.; Smith, C.

    2016-09-01

    The Space Environment Research Centre (SERC) is a fully-funded multi-national research collaboration for the management and mitigation of space debris using optical technologies. SERC is tasked with developing mitigation strategies for the many debris objects not amenable to space-based interventions. SERC research leverages very accurate information from a new optical space tracking network to develop viable near-term strategies to manage debris using only ground-based infrastructure. SERC has sufficient resources to conduct full-scale on-orbit testing of candidate approaches. We report on SERC progress in astrodynamics, precision catalogs, conjunction processing, adaptive optics and high power lasers as well as the architecture of the research effort.

  10. Cloud Computing Techniques for Space Mission Design

    NASA Technical Reports Server (NTRS)

    Arrieta, Juan; Senent, Juan

    2014-01-01

    The overarching objective of space mission design is to tackle complex problems producing better results, and faster. In developing the methods and tools to fulfill this objective, the user interacts with the different layers of a computing system.

  11. Cloud Computing Techniques for Space Mission Design

    NASA Technical Reports Server (NTRS)

    Arrieta, Juan; Senent, Juan

    2014-01-01

    The overarching objective of space mission design is to tackle complex problems producing better results, and faster. In developing the methods and tools to fulfill this objective, the user interacts with the different layers of a computing system.

  12. Enthalpy of sublimation as measured using a silicon oscillator

    NASA Astrophysics Data System (ADS)

    Shakeel, Hamza; Pomeroy, J. M.

    In this study, we report the enthalpy of sublimation of common gases (nitrogen, oxygen, argon, carbon dioxide, neon, krypton, xenon, and water vapor) using a large area silicon oscillator with a sub-ng (~0.027 ng/cm2) mass sensitivity. The double paddle oscillator design enables high frequency stability (17 ppb) at cryogenic temperatures and provides a consistent technique for enthalpy measurements. The enthalpies of sublimation are derived from the rate of mass loss during programmed thermal desorption and are detected as a change in the resonance frequency of the self-tracking oscillator. These measured enthalpy values show excellent agreement with the accepted literature values.

  13. Sublimation rates of explosive materials : method development and initial results.

    SciTech Connect

    Phelan, James M.; Patton, Robert Thomas

    2004-08-01

    Vapor detection of explosives continues to be a technological basis for security applications. This study began experimental work to measure the chemical emanation rates of pure explosive materials as a basis for determining emanation rates of security threats containing explosives. Sublimation rates for TNT were determined with thermo gravimetric analysis using two different techniques. Data were compared with other literature values to provide sublimation rates from 25 to 70 C. The enthalpy of sublimation for the combined data was found to be 115 kJ/mol, which corresponds well with previously reported data from vapor pressure determinations. A simple Gaussian atmospheric dispersion model was used to estimate downrange concentrations based on continuous, steady-state conditions at 20, 45 and 62 C for a nominal exposed block of TNT under low wind conditions. Recommendations are made for extension of the experimental vapor emanation rate determinations and development of turbulent flow computational fluid dynamics based atmospheric dispersion estimates of standoff vapor concentrations.

  14. Micro-computed tomography observation of sublimation interface and image analysis on sublimation process during freeze-drying.

    PubMed

    Xiao, Xin; Tao, Le-Ren; Hua, Tse-Chao

    2007-01-01

    The freeze-drying process is complicated with complex heat and mass transfer during sublimation. The sublimation interface of freeze-drying has become more attractive and meaningful recently. In this study, apple slices undergoing sublimation were scanned by a Micro-CT scanner. The cross-sectional images were reconstructed with those scanning images respectively. The technique of grey value analysis was used to recognize the procedure. The results showed that, from direct scanning images and 2-D reconstructed images, a 3-D moving mode of sublimation interface which contracted to the centre of the sample could be seen, sublimation process proceeded from edge to center gradually. The grey value of ice crystals was determined to be 154 through gauss calculation. By comparing frozen sample with freeze-dried one, the ice crystals regions in the beginning became the porous regions after drying, grey values increased correspondingly. Samples shrunk slightly after drying for 3 to 7 hours, which could be distinguished by the change in grey values.

  15. APPARATUS FOR CONDENSATION AND SUBLIMATION

    DOEpatents

    Schmidt, R.J.; Fuis, F. Jr.

    1958-10-01

    An apparatus is presented for the sublimation and condensation of uranium compounds in order to obtain an improved crystalline structure of this material. The apparatus comprises a vaporizing chamber and condensing structure connected thereto. There condenser is fitted with a removable liner having a demountable baffle attached to the liner by means of brackets and a removable pin. The baffle is of spiral cross-section and is provided with cooling coils disposed between the surfaces of the baffle for circulation of a temperature controlling liquid within the baffle. The cooling coll provides for controlllng the temperature of the baffle to insure formatlon of a satisfactory condensate, and the removable liner facilitates the removal of condensate formed during tbe sublimation process.

  16. New Techniques in Space Weather Forecasting

    DTIC Science & Technology

    2005-05-01

    during Solar Cycle 23, J. Geophys. Res. (accepted ) 2006. [2] M. Kartalev, M. Dryer , K. Grigorov, E. Stoimenova. Solar wind polytropic index...Magneto Hydrodynamics (MHD) discontinuities that occur due to the solar wind, and its effects on communications. 15. SUBJECT...TERMS EOARD, Communications, Space Weather, Solar Physics 16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON MICHAEL KJ MILLIGAN, Lt Col

  17. Mass wasting triggered by seasonal CO2 sublimation under Martian atmospheric conditions: Laboratory experiments

    NASA Astrophysics Data System (ADS)

    Sylvest, Matthew E.; Conway, Susan J.; Patel, Manish R.; Dixon, John C.; Barnes, Adam

    2016-12-01

    Sublimation is a recognized process by which planetary landscapes can be modified. However, interpretation of whether sublimation is involved in downslope movements on Mars and other bodies is restricted by a lack of empirical data to constrain this mechanism of sediment transport and its influence on landform morphology. Here we present the first set of laboratory experiments under Martian atmospheric conditions which demonstrate that the sublimation of CO2 ice from within the sediment body can trigger failure of unconsolidated, regolith slopes and can measurably alter the landscape. Previous theoretical studies required CO2 slab ice for movements, but we find that only frost is required. Hence, sediment transport by CO2 sublimation could be more widely applicable (in space and time) on Mars than previously thought. This supports recent work suggesting CO2 sublimation could be responsible for recent modification in Martian gullies.

  18. Robotic vision techniques for space operations

    NASA Technical Reports Server (NTRS)

    Krishen, Kumar

    1994-01-01

    Automation and robotics for space applications are being pursued for increased productivity, enhanced reliability, increased flexibility, higher safety, and for the automation of time-consuming tasks and those activities which are beyond the capacity of the crew. One of the key functional elements of an automated robotic system is sensing and perception. As the robotics era dawns in space, vision systems will be required to provide the key sensory data needed for multifaceted intelligent operations. In general, the three-dimensional scene/object description, along with location, orientation, and motion parameters will be needed. In space, the absence of diffused lighting due to a lack of atmosphere gives rise to: (a) high dynamic range (10(exp 8)) of scattered sunlight intensities, resulting in very high contrast between shadowed and specular portions of the scene; (b) intense specular reflections causing target/scene bloom; and (c) loss of portions of the image due to shadowing and presence of stars, Earth, Moon, and other space objects in the scene. In this work, developments for combating the adverse effects described earlier and for enhancing scene definition are discussed. Both active and passive sensors are used. The algorithm for selecting appropriate wavelength, polarization, look angle of vision sensors is based on environmental factors as well as the properties of the target/scene which are to be perceived. The environment is characterized on the basis of sunlight and other illumination incident on the target/scene and the temperature profiles estimated on the basis of the incident illumination. The unknown geometrical and physical parameters are then derived from the fusion of the active and passive microwave, infrared, laser, and optical data.

  19. Space data relay systems. [random access technique

    NASA Technical Reports Server (NTRS)

    Cote, C. E.

    1975-01-01

    Significant progress has been achieved in simplifying platform concepts through random access techniques. This is particularly important in applications such as balloons where weight is critical. In applications, where weight restriction may not be a problem, the concept lends itself to uncomplicated designs and low cost. Nevertheless, ordered systems offer inherent advantages in managing data flow which justifies their use. With continuing improvements in technology, particularly low power receivers, ordered systems should become quite competitive with random systems for many applications.

  20. Direct Isolation of Purines and Pyrimidines from Nucleic Acids Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Schubert, Michael; Bada, Jeffrey L.

    2003-01-01

    A sublimation technique was developed to isolate purines and pyrimidines directly from lambda-deoxyribonucleic acid (lambda-DNA) and Escherichia coli cells. The sublimation of adenine, cytosine, guanine, and thymine from lambda-DNA was tested under reduced pressure (approx. 0.5 Torr) at temperatures of >150 C. With the exception of guanine, approximately 60 -75% of each base was sublimed directly from the lambda-DNA and recovered on a coldfinger of the sublimation apparatus after heating to 450 C. Several nucleobases including adenine, cytosine, thymine, and uracil were also recovered from E. coli bacteria after heating the cells to the same temperature, although some thermal decomposition of the bases also occurred. These results demonstrate the feasibility of using sublimation to isolate purines and pyrimidines from native E. coli DNA and RNA without any chemical treatment of the cells.

  1. Direct Isolation of Purines and Pyrimidines from Nucleic Acids Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Schubert, Michael; Bada, Jeffrey L.

    2003-01-01

    A sublimation technique was developed to isolate purines and pyrimidines directly from lambda-deoxyribonucleic acid (lambda-DNA) and Escherichia coli cells. The sublimation of adenine, cytosine, guanine, and thymine from lambda-DNA was tested under reduced pressure (approx. 0.5 Torr) at temperatures of >150 C. With the exception of guanine, approximately 60 -75% of each base was sublimed directly from the lambda-DNA and recovered on a coldfinger of the sublimation apparatus after heating to 450 C. Several nucleobases including adenine, cytosine, thymine, and uracil were also recovered from E. coli bacteria after heating the cells to the same temperature, although some thermal decomposition of the bases also occurred. These results demonstrate the feasibility of using sublimation to isolate purines and pyrimidines from native E. coli DNA and RNA without any chemical treatment of the cells.

  2. Key-space analysis of double random phase encryption technique

    NASA Astrophysics Data System (ADS)

    Monaghan, David S.; Gopinathan, Unnikrishnan; Naughton, Thomas J.; Sheridan, John T.

    2007-09-01

    We perform a numerical analysis on the double random phase encryption/decryption technique. The key-space of an encryption technique is the set of possible keys that can be used to encode data using that technique. In the case of a strong encryption scheme, many keys must be tried in any brute-force attack on that technique. Traditionally, designers of optical image encryption systems demonstrate only how a small number of arbitrary keys cannot decrypt a chosen encrypted image in their system. However, this type of demonstration does not discuss the properties of the key-space nor refute the feasibility of an efficient brute-force attack. To clarify these issues we present a key-space analysis of the technique. For a range of problem instances we plot the distribution of decryption errors in the key-space indicating the lack of feasibility of a simple brute-force attack.

  3. Tracking techniques for space shuttle rendezvous

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The space shuttle rendezvous radar has a requirement to track cooperative and non-cooperative targets. For this reason the Lunar Module (LM) Rendezvous Radar was modified to incorporate the capability of tracking a non-cooperative target. The modifications are discussed. All modifications except those relating to frequency diversity were completed, and system tests were performed to confirm proper performance in the non-cooperative mode. Frequency diversity was added to the radar and to the special test equipment, and then system tests were performed. This last set of tests included re-running the tests of the non-cooperative mode without frequency diversity, followed by tests with frequency diversity and tests of operation in the original cooperative mode.

  4. Space Shuttle MMOD Threat Mitigation Techniques

    NASA Technical Reports Server (NTRS)

    Hyde, J. L.; Christiansen, E. L.; Lear, D. M.; Kerr, J. H.

    2008-01-01

    Prior to each shuttle mission, threat assessments are performed to determine the risk of critical penetration, payload bay door radiator tube leak and crew module window replacement from Micrometeoroid and Orbital Debris (MMOD). Mission parameters, such as vehicle attitude, exposure time and altitude are used as inputs for the analysis. Ballistic limit equations, based on hypervelocity impact testing of shuttle materials are used to estimate the critical particle diameters of the outer surfaces of the vehicle. The assessments are performed using the BUMPER computer code at the NASA/JSC Hypervelocity Impact Technology Facility (HITF). The most critical involves the calculation of Loss of Crew and Vehicle (LOCV) risk. An overview of significant MMOD impacts on the Payload Bay Door radiators, wing leading edge reinforced carbon-carbon (RCC) panels and crew module windows will be presented, along with a discussion of the techniques NASA has implemented to reduce the risk from MMOD impacts. This paper will describe on-orbit inspection of the RCC regions and the methods used discern hypervelocity impact damage. Impact damage contingency plans and on-orbit repair techniques will also be discussed. The wing leading edge impact detection system (WLEIDS) and it s role in the reduction of on-orbit risk reduction will be presented. Finally, an analysis of alternative shuttle flight attitudes on MMOD risk will be demonstrated.

  5. Space Shuttle MMOD Threat Mitigation Techniques

    NASA Technical Reports Server (NTRS)

    Hyde, Justin L.; Christiansen, Eric L.; Kerr, James H.

    2007-01-01

    Prior to each shuttle mission, threat assessments are performed to determine the risk of critical penetration, payload bay door radiator tube leak and crew module window replacement from Micrometeoroid and Orbital Debris (MMOD). Mission parameters, such as vehicle attitude, exposure time and altitude are used as inputs for the analysis. Ballistic limit equations, based on hypervelocity impact testing of shuttle materials are used to estimate the critical particle diameters of the outer surfaces of the vehicle. The assessments are performed using the BUMPER computer code at the NASA/JSC Hypervelocity Impact Technology Facility (HITF). The most critical involves the calculation of Loss of Crew and Vehicle (LOCV) risk. In recent years, NASA has implemented several techniques to reduce the risk to the Shuttle from MMOD impacts. This paper will describe on-orbit inspection of the reinforced carbon-carbon (RCC) regions and the methods used discern hypervelocity impact damage. Impact damage contingency plans and on-orbit repair techniques will also be discussed. The wing leading edge impact detection system (WLEIDS) and it's role in the reduction of on-orbit risk reduction will be presented. Finally, an analysis of the effectivity of alternative shuttle flight attitudes on MMOD risk will be demonstrated.

  6. Trends and Techniques for Space Base Electronics

    NASA Technical Reports Server (NTRS)

    Trotter, J. D.; Wade, T. E.; Gassaway, J. D.

    1979-01-01

    Simulations of various phosphorus and boron diffusions in SOS were completed and a sputtering system, furnaces, and photolithography related equipment were set up. Double layer metal experiments initially utilized wet chemistry techniques. By incorporating ultrasonic etching of the vias, premetal cleaning a modified buffered HF, phosphorus doped vapox, and extended sintering, yields of 98% were obtained using the standard test pattern. A two dimensional modeling program was written for simulating short channel MOSFETs with nonuniform substrate doping. A key simplifying assumption used is that the majority carriers can be represented by a sheet charge at the silicon dioxide silicon interface. Although the program is incomplete, the two dimensional Poisson equation for the potential distribution was achieved. The status of other Z-D MOSFET simulation programs is summarized.

  7. Techniques for estimating Space Station aerodynamic characteristics

    NASA Technical Reports Server (NTRS)

    Thomas, Richard E.

    1993-01-01

    A method was devised and calculations were performed to determine the effects of reflected molecules on the aerodynamic force and moment coefficients for a body in free molecule flow. A procedure was developed for determining the velocity and temperature distributions of molecules reflected from a surface of arbitrary momentum and energy accommodation. A system of equations, based on momentum and energy balances for the surface, incident, and reflected molecules, was solved by a numerical optimization technique. The minimization of a 'cost' function, developed from the set of equations, resulted in the determination of the defining properties of the flow reflected from the arbitrary surface. The properties used to define both the incident and reflected flows were: average temperature of the molecules in the flow, angle of the flow with respect to a vector normal to the surface, and the molecular speed ratio. The properties of the reflected flow were used to calculate the contribution of multiply reflected molecules to the force and moments on a test body in the flow. The test configuration consisted of two flat plates joined along one edge at a right angle to each other. When force and moment coefficients of this 90 deg concave wedge were compared to results that did not include multiple reflections, it was found that multiple reflections could nearly double lift and drag coefficients, with nearly a 50 percent increase in pitching moment for cases with specular or nearly specular accommodation. The cases of diffuse or nearly diffuse accommodation often had minor reductions in axial and normal forces when multiple reflections were included. There were several cases of intermediate accommodation where the addition of multiple reflection effects more than tripled the lift coefficient over the convex technique.

  8. Offloading techniques for large deployable space structures

    NASA Technical Reports Server (NTRS)

    Caravaggio, Levino; Golob, Alex

    1992-01-01

    The validation and verification of large deployable space structures are continual challenges which face the integration and test engineer today. Spar Aerospace Limited has worked on various programs in which such structure validation was required and faces similar tasks in the future. This testing is reported and the different offloading and deployment methods which were used, as well as the proposed methods which will be used on future programs, are described. Past programs discussed include the Olympus solar array ambient and thermal vacuum deployments, and the Anik-E array and reflector deployments. The proposed MSAT reflector and boom ambient deployment tests, as well as the proposed RADARSAT Synthetic Aperture Radar (SAR) ambient and thermal vacuum deployment tests will also be presented. A series of tests relating to various component parts of the offloading equipment systems was required. These tests included the characterization and understanding of linear bearings and large (180 in-lbf) constant force spring motors in a thermal vacuum environment, and the results from these tests are presented.

  9. Sublimation as a landform-shaping process on Pluto

    NASA Astrophysics Data System (ADS)

    Moore, Jeffrey M.; Howard, Alan D.; Umurhan, Orkan M.; White, Oliver L.; Schenk, Paul M.; Beyer, Ross A.; McKinnon, William B.; Spencer, John R.; Grundy, Will M.; Lauer, Tod R.; Nimmo, Francis; Young, Leslie A.; Stern, S. Alan; Weaver, Harold A.; Olkin, Cathy B.; Ennico, Kimberly; New Horizons Science Team

    2017-05-01

    Fields of pits, both large and small, in Tombaugh Regio (Sputnik Planitia, and the Pitted Uplands to the east), and along the scarp of Piri Rupes, are examples of landscapes on Pluto where we conclude that sublimation drives their formation and evolution. Our heuristic modeling closely mimics the form, spacing, and arrangement of a variety of Tombaugh Regio's pits. Pluto's sublimation modified landforms appear to require a significant role for (diffusive) mass wasting as suggested by our modeling. In our models, the temporal evolution of pitted surfaces is such that initially lots of time passes with little happening, then eventually, very rapid development of relief and rapid sublimation. Small pits on Sputnik Planitia are consistent with their formation in N2-dominated materials. As N2-ice readily flows, some other ``stiffer'' volatile ice may play a role in supporting the relief of sublimation degraded landforms that exhibit several hundred meters of relief. A strong candidate is CH4, which is spectroscopically observed to be associated with these features, but the current state of rheological knowledge for CH4 ice at Pluto conditions is insufficient for a firm assessment.

  10. Modern approach to an old technique: Narrative revision of techniques used to locate the epidural space.

    PubMed

    Brogly, N; Guasch Arévalo, E; Kollmann Camaiora, A; Alsina Marcos, E; García García, C; Gilsanz Rodríguez, F

    2017-03-16

    Since the first description of the epidural technique during the 1920s, the continuous progress of knowledge of the anatomy and physiology of the epidural space has allowed the development of different techniques to locate this space while increasing both the safety and efficacy of the procedure. The most common techniques used today are based on the two main characteristics of the epidural space: the difference in distensibility between the ligamentum flavum and the epidural space, and the existence of negative pressure within the epidural space. However, over recent years, technological advances have allowed the development of new techniques to locate the epidural space based on other physical properties of tissues. Some are still in the experimental phase, but others, like ultrasound-location have reached a clinical phase and are being used increasingly in daily practice.

  11. Gravimetry and Space Techniques Applied to Geodynamics and Ocean Dynamics

    NASA Astrophysics Data System (ADS)

    Schutz, Bob E.; Anderson, Allen; Froidevaux, Claude; Parke, Michael

    The variety of disciplines represented in this volume (including space geodesy, oceanography, geophysics, and celestial mechanics) attest to the interdisciplinary applications of gravimetry and space techniques. The relation to sea level is addressed within some of the papers and the contributions of the techniques to development of global gravity models are discussed. The space technique of satellite altimetry has become a prominent contributor to sea surface topography as well as ocean tide models and determination of gravity, especially in ocean areas. Ocean tides influence the motion of near-Earth satellites and the rotation of the Earth. Modern space geodesy is increasingly relying on the Global Positioning System for measuring geophysical phenomena manifested at the surface through crustal deformations. Furthermore, the geophysical interpretation of gravity anomalies has been facilitated by the introduction of modern techniques. This volume represents only a small "snapshot" of the interdisciplinary research being conducted. Modem space geodesy is one of the common links between the disciplines reflected in this volume. New developments in gravimetry and space techniques will further enhance and foster interdisciplinary work in coming years.

  12. Carbon Dioxide Sublimation on Iapetus: Exploring the Kinetic Possibilities

    NASA Astrophysics Data System (ADS)

    Blackburn, David G.; Rivera-Valentin, E. G.; Ulrich, R.

    2010-10-01

    Although Cassini did not map the northern pole of Iapetus to test the claims of a CO2 polar cap (Palmer and Brown, 2007, Astrophys. Jour., 666, L125-L128), further modeling can determine its likelihood. Recent spectral analysis of the 4.26 micron CO2 absorption feature in the dark material on Iapetus demonstrates that the surface may contain pure, clathrated, or complexed carbon dioxide (Cruikshank et. al., 2010, Icarus, 206, 561-572). We will explore the kinetics behind sublimation from all three possibilities by building upon experimental results of dry ice and CO2 clathrate hydrate sublimation under low temperature and pressure conditions (Leeman et al., 2010, LPSC XLI, 1533; Blackburn et al., 2010, Planet. and Space Sci., 58, 780-791). We will set strict limits on the mass flux of CO2 available from each of these scenarios by applying a new thermal model incorporating albedo from the recent bolometric Bond albedo map that includes coverage of the northern pole from Voyager (Blackburn et al., 2010, Icarus, submitted). While previous sublimation rate estimates have relied on the Langmuir evaporation equation, we contend that this formula sets only the upper limit on the amount of sublimation that can occur. The rate is even further reduced when considering the possibility of CO2 sublimation though an overburden. We will present the implications of this new model on ballistic transport of CO2, stability zones for dry ice, CO2 clathrate hydrate, and complexed CO2, as well as the resident times of a possible CO2 polar cap on Iapetus.

  13. Schopenhauer, Nietzsche, and the Aesthetically Sublime

    ERIC Educational Resources Information Center

    Vandenabeele, Bart

    2003-01-01

    Much has been written on the relationship between Arthur Schopenhauer and Friedrich Nietzsche. Much remains to be said, however, concerning their respective theories of the sublime. In this article, the author first argues against the traditional, dialectical view of Schopenhauer's theory of the sublime that stresses the crucial role the sublime…

  14. Schopenhauer, Nietzsche, and the Aesthetically Sublime

    ERIC Educational Resources Information Center

    Vandenabeele, Bart

    2003-01-01

    Much has been written on the relationship between Arthur Schopenhauer and Friedrich Nietzsche. Much remains to be said, however, concerning their respective theories of the sublime. In this article, the author first argues against the traditional, dialectical view of Schopenhauer's theory of the sublime that stresses the crucial role the sublime…

  15. Surface engineering of SiC via sublimation etching

    NASA Astrophysics Data System (ADS)

    Jokubavicius, Valdas; Yazdi, Gholam R.; Ivanov, Ivan G.; Niu, Yuran; Zakharov, Alexei; Iakimov, Tihomir; Syväjärvi, Mikael; Yakimova, Rositsa

    2016-12-01

    We present a technique for etching of SiC which is based on sublimation and can be used to modify the morphology and reconstruction of silicon carbide surface for subsequent epitaxial growth of various materials, for example graphene. The sublimation etching of 6H-, 4H- and 3C-SiC was explored in vacuum (10-5 mbar) and Ar (700 mbar) ambient using two different etching arrangements which can be considered as Si-C and Si-C-Ta chemical systems exhibiting different vapor phase stoichiometry at a given temperature. The surfaces of different polytypes etched under similar conditions are compared and the etching mechanism is discussed with an emphasis on the role of tantalum as a carbon getter. To demonstrate applicability of such etching process graphene nanoribbons were grown on a 4H-SiC surface that was pre-patterned using the thermal etching technique presented in this study.

  16. A grid spacing control technique for algebraic grid generation methods

    NASA Technical Reports Server (NTRS)

    Smith, R. E.; Kudlinski, R. A.; Everton, E. L.

    1982-01-01

    A technique which controls the spacing of grid points in algebraically defined coordinate transformations is described. The technique is based on the generation of control functions which map a uniformly distributed computational grid onto parametric variables defining the physical grid. The control functions are smoothed cubic splines. Sets of control points are input for each coordinate directions to outline the control functions. Smoothed cubic spline functions are then generated to approximate the input data. The technique works best in an interactive graphics environment where control inputs and grid displays are nearly instantaneous. The technique is illustrated with the two-boundary grid generation algorithm.

  17. Canopy Effects on Macroscale Snow Sublimation

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2015-12-01

    Sublimation of snow cover directly affects snow accumulation, impacting ecosystem processes, soil moisture, soil porosity, biogeochemical processes, wildfire, and water resources. Available energy, the exposed surface area of a snow cover, and exposure time with the atmosphere vary greatly in complex terrain (e.g., aspect, elevation, forest cover), with latitude, and with continentality. It is therefore difficult to scale up results from site specific short term studies. Using the 32-km NARR, the 4-km PRISM, with 30-m terrain and forest cover data, meteorological variables are downscaled to simulate sublimation from canopy intercepted snow and from the snowpack over the Salt River Basin in Arizona for a wet and dry year. Simulations indicate that: (1) total sublimation is highly variable in response to variability in both sublimation rate and snow cover duration; (2) total canopy sublimation is similar for both years while ground sublimation is considerably greater during the wet year; (3) sublimation is a relatively greater contribution to the snow water budget during the dry year (28% vs. 20% of total snowfall); (4) at high elevations, ground sublimation is less in open areas than forested areas during the dry year, while the reverse is evident during the wet year as snowpack lasted longer into spring. While a reduction in leaf area index leads to a reduction of total sublimation due to less interception in both years, ground sublimation increases during the dry year, possibly due to less sheltering from solar radiation and wind. This reduction in sheltering results in a large decrease in snowpack duration (i.e., ten days in spring) at mid-elevations for the wet year, leading to a decrease in ground sublimation. This results in a 500 meter difference in the elevation of maximum sublimation reduction upon reduced leaf area index between the two years. Forest cover properties can vary considerably on short and long time scales through natural (wildfire, bark beetle

  18. Error control techniques for satellite and space communications

    NASA Technical Reports Server (NTRS)

    Costello, Daniel J., Jr.

    1991-01-01

    Research activities related to error control techniques for satellite and space communication are reported. Specific areas of research include: coding gains for bandwidth efficient codes, hardware implementation of a bandwidth efficient coding scheme for the Hubble Space Telescope, construction of long trellis codes for use with sequential decoding, performance analysis of multilevel trellis codes, and M-algorithm decoding of trellis codes. Each topic is discussed in a corresponding paper that appears in the appendices.

  19. Advanced thermal management techniques for space power electronics

    NASA Astrophysics Data System (ADS)

    Reyes, Angel Samuel

    1992-01-01

    Modern electronic systems used in space must be reliable and efficient with thermal management unaffected by outer space constraints. Current thermal management techniques are not sufficient for the increasing waste heat dissipation of novel electronic technologies. Many advanced thermal management techniques have been developed in recent years that have application in high power electronic systems. The benefits and limitations of emerging cooling technologies are discussed. These technologies include: liquid pumped devices, mechanically pumped two-phase cooling, capillary pumped evaporative cooling, and thermoelectric devices. Currently, liquid pumped devices offer the most promising alternative for electronics thermal control.

  20. The Advanced Space Plant Culture Device with Live Imaging Technique

    NASA Astrophysics Data System (ADS)

    Zheng, Weibo; Zhang, Tao; Tong, Guanghui

    The live imaging techniques, including the color and fluorescent imags, are very important and useful for space life science. The advanced space plant culture Device (ASPCD) with live imaging Technique, developed for Chinese Spacecraft, would be introduced in this paper. The ASPCD had two plant experimental chambers. Three cameras (two color cameras and one fluorescent camera) were installed in the two chambers. The fluorescent camera could observe flowering genes, which were labeled by GFP. The lighting, nutrient, temperature controling and water recycling were all independent in each chamber. The ASPCD would beed applied to investigate for the growth and development of the high plant under microgravity conditions on board the Chinese Spacecraft.

  1. Applications notice. [application of space techniques to earth resources, environment management, and space processing

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The discipline programs of the Space and Terrestrial (S&T) Applications Program are described and examples of research areas of current interest are given. Application of space techniques to improve conditions on earth are summarized. Discipline programs discussed include: resource observations; environmental observations; communications; materials processing in space; and applications systems/information systems. Format information on submission of unsolicited proposals for research related to the S&T Applications Program are given.

  2. GINFEST: Geodetic Intercomparison Network for Evaluating Space Techniques

    NASA Astrophysics Data System (ADS)

    Ashkenazi, Vidal

    Details are given of a geodetic network connecting the major radio telescopes and SLR facilities in Western and Central Europe, which is to be used in a co-location exercise involving VLBI, CERI, SLR and GPS observations, with the aim of evaluating the relative accuracies and system biases of these geodetic space observation techniques.

  3. Sublimation in bright spots on (1) Ceres.

    PubMed

    Nathues, A; Hoffmann, M; Schaefer, M; Le Corre, L; Reddy, V; Platz, T; Cloutis, E A; Christensen, U; Kneissl, T; Li, J-Y; Mengel, K; Schmedemann, N; Schaefer, T; Russell, C T; Applin, D M; Buczkowski, D L; Izawa, M R M; Keller, H U; O'Brien, D P; Pieters, C M; Raymond, C A; Ripken, J; Schenk, P M; Schmidt, B E; Sierks, H; Sykes, M V; Thangjam, G S; Vincent, J-B

    2015-12-10

    The dwarf planet (1) Ceres, the largest object in the main asteroid belt with a mean diameter of about 950 kilometres, is located at a mean distance from the Sun of about 2.8 astronomical units (one astronomical unit is the Earth-Sun distance). Thermal evolution models suggest that it is a differentiated body with potential geological activity. Unlike on the icy satellites of Jupiter and Saturn, where tidal forces are responsible for spewing briny water into space, no tidal forces are acting on Ceres. In the absence of such forces, most objects in the main asteroid belt are expected to be geologically inert. The recent discovery of water vapour absorption near Ceres and previous detection of bound water and OH near and on Ceres (refs 5-7) have raised interest in the possible presence of surface ice. Here we report the presence of localized bright areas on Ceres from an orbiting imager. These unusual areas are consistent with hydrated magnesium sulfates mixed with dark background material, although other compositions are possible. Of particular interest is a bright pit on the floor of crater Occator that exhibits probable sublimation of water ice, producing haze clouds inside the crater that appear and disappear with a diurnal rhythm. Slow-moving condensed-ice or dust particles may explain this haze. We conclude that Ceres must have accreted material from beyond the 'snow line', which is the distance from the Sun at which water molecules condense.

  4. Sublimation in bright spots on (1) Ceres

    NASA Astrophysics Data System (ADS)

    Nathues, A.; Hoffmann, M.; Schaefer, M.; Le Corre, L.; Reddy, V.; Platz, T.; Cloutis, E. A.; Christensen, U.; Kneissl, T.; Li, J.-Y.; Mengel, K.; Schmedemann, N.; Schaefer, T.; Russell, C. T.; Applin, D. M.; Buczkowski, D. L.; Izawa, M. R. M.; Keller, H. U.; O'Brien, D. P.; Pieters, C. M.; Raymond, C. A.; Ripken, J.; Schenk, P. M.; Schmidt, B. E.; Sierks, H.; Sykes, M. V.; Thangjam, G. S.; Vincent, J.-B.

    2015-12-01

    The dwarf planet (1) Ceres, the largest object in the main asteroid belt with a mean diameter of about 950 kilometres, is located at a mean distance from the Sun of about 2.8 astronomical units (one astronomical unit is the Earth-Sun distance). Thermal evolution models suggest that it is a differentiated body with potential geological activity. Unlike on the icy satellites of Jupiter and Saturn, where tidal forces are responsible for spewing briny water into space, no tidal forces are acting on Ceres. In the absence of such forces, most objects in the main asteroid belt are expected to be geologically inert. The recent discovery of water vapour absorption near Ceres and previous detection of bound water and OH near and on Ceres (refs 5, 6, 7) have raised interest in the possible presence of surface ice. Here we report the presence of localized bright areas on Ceres from an orbiting imager. These unusual areas are consistent with hydrated magnesium sulfates mixed with dark background material, although other compositions are possible. Of particular interest is a bright pit on the floor of crater Occator that exhibits probable sublimation of water ice, producing haze clouds inside the crater that appear and disappear with a diurnal rhythm. Slow-moving condensed-ice or dust particles may explain this haze. We conclude that Ceres must have accreted material from beyond the ‘snow line’, which is the distance from the Sun at which water molecules condense.

  5. Testing and Model Correlation of Sublimator Driven Coldplate Coupons and EDU

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.

    2009-01-01

    The Sublimator Driven Coldplate (SDC) is a unique piece of thermal control hardware that has several advantages over a more traditional thermal control system. The principal advantage is the possible elimination of a pumped fluid loop, potentially saving mass, power, and complexity. Because this concept relies on evaporative heat rejection techniques, it is primarily useful for short mission durations. Additionally, the concept requires a conductive path between the heat-generating component and the heat rejection device. Therefore, it is mostly a relevant solution for a vehicle with a relatively low heat rejection requirement and/or short transport distances. Tests were performed on coupons and an Engineering Development Unit (EDU) at NASA s Johnson Space Center to better understand the basic operational principles and to validate the analytical methods being used for the SDC development. This paper outlines the results of the SDC tests, the subsequent thermal model correlation, and a description of the SDC Engineering Development Unit test results.

  6. Near-equilibrium growth of thick, high quality beta-SiC by sublimation

    NASA Technical Reports Server (NTRS)

    Shields, Virgil B.; Fekade, Konjit; Spencer, Michael G.

    1993-01-01

    A close spaced near-equilibrium growth technique was used to produce thick, high quality epitaxial layers of beta-silicon carbide. The process utilized a sublimation method to grow morphologically smooth layers. The beta silicon carbide growth layers varied from about 200 to 750 microns in thickness. Chemical vapor deposition grown, 2-10 microns, beta silicon carbide films were used as seeds at 1860 and 1910 C growth temperatures. The respective average growth rates were 20 and 30 microns per hour. The layers are p-type with a 3.1 x 10 exp 17/cu cm carrier concentration. Electrical measurements indicate considerable improvement in the breakdown voltage of Schottky barriers on growth samples. Breakdown values ranged from 25 to 60 V. These measurements represent the highest values reported for 3C-SiC.

  7. Data Compression Techniques for Advanced Space Transportation Systems

    NASA Technical Reports Server (NTRS)

    Bradley, William G.

    1998-01-01

    Advanced space transportation systems, including vehicle state of health systems, will produce large amounts of data which must be stored on board the vehicle and or transmitted to the ground and stored. The cost of storage or transmission of the data could be reduced if the number of bits required to represent the data is reduced by the use of data compression techniques. Most of the work done in this study was rather generic and could apply to many data compression systems, but the first application area to be considered was launch vehicle state of health telemetry systems. Both lossless and lossy compression techniques were considered in this study.

  8. Valence space techniques and QRPA vibrational mass parameters

    NASA Astrophysics Data System (ADS)

    Deloncle, I.; Lechaftois, F.; Péru, S.

    2016-06-01

    The vibrational mass parameters entering the quadrupolar 5DCH Hamiltonian are commonly obtained neglecting beyond mean-field correlations and the dynamical mean-field rearrangement. The Quasiparticle Random Phase Approximation (QRPA) framework would allow to avoid these disadvantages [1], if the computation time, when using density dependent force, was not prohibitive. Here, a significant time reduction is obtained by applying valence space (VS) techniques (energy cut-off and inert core) in QRPA calculations. The VS techniques allow to probe the physical content of the mass parameter. The QRPA mass parameter exhibit robustness toward VS limitations contrarily to the intrinsic QRPA outputs, that show deceptive appearance when an inert core is used. Excited states energy, and associated transition probabilities, should not be considered for optimizing the valence space limits.

  9. Technique for observation derived boundary conditions for Space Weather

    NASA Astrophysics Data System (ADS)

    Pagano, Paolo; Mackay, Duncan; Yeates, Anthony

    2017-04-01

    We propose a new efficient and accurate modelling technique suitable for the next generation of Space Weather predictive tools. Specifically, we put forward an approach that can provide interplanetary Space Weather forecasting models with an accurate time dependent boundary condition of erupting flux ropes in the upper Solar Corona. The unique strength of this technique is that it follows the time evolution of coronal magnetic fields directly driven from observations and captures the full life span of magnetic flux ropes from formation to ejection. To produce accurate and effective boundary conditions we couple two different modelling techniques, MHD simulations with quasi-static non-potential modelling. Our modelling approach uses a time series of observed synoptic magnetograms to drive the non-potential evolution model of the coronal magnetic field to follow the formation and loss of equilibrium of magnetic flux ropes. Following this a MHD simulation captures the dynamic evolution of the ejection phase of the flux rope into interplanetary space. We focus here on the MHD simulation that describes the ejection of two magnetic flux ropes through the solar corona to the outer boundary. At this boundary we then produce time dependent boundary conditions for the magnetic field and plasma that in the future may be applied to interplanetary space weather prediction models. We illustrate that the coupling of observationally derived quasi-static non-potential magnetic field modelling and MHD simulations can significantly reduce the computational time for producing realistic observationally derived boundary conditions at the boundary between the corona and interplanetary space.

  10. Simplified thermal estimation techniques for large space structures

    NASA Technical Reports Server (NTRS)

    Brogren, E. W.; Barclay, D. L.; Straayer, J. W.

    1977-01-01

    A tool for making rapid estimates of the response of space structures to thermal environments encountered in earth orbits is provided for the designer of these structures. Charts giving heating rates and temperatures for certain typical large spacecraft structural elements are provided. Background information for spacecraft thermal design considerations is presented. Environments, requirements, thermal control techniques, design guidelines, and approaches available for more detailed thermal response analysis are discussed.

  11. Active vibration control techniques for flexible space structures

    NASA Technical Reports Server (NTRS)

    Parlos, Alexander G.; Jayasuriya, Suhada

    1990-01-01

    Two proposed control system design techniques for active vibration control in flexible space structures are detailed. Control issues relevant only to flexible-body dynamics are addressed, whereas no attempt was made to integrate the flexible and rigid-body spacecraft dynamics. Both of the proposed approaches revealed encouraging results; however, further investigation of the interaction of the flexible and rigid-body dynamics is warranted.

  12. Mathematical analysis techniques for modeling the space network activities

    NASA Technical Reports Server (NTRS)

    Foster, Lisa M.

    1992-01-01

    The objective of the present work was to explore and identify mathematical analysis techniques, and in particular, the use of linear programming. This topic was then applied to the Tracking and Data Relay Satellite System (TDRSS) in order to understand the space network better. Finally, a small scale version of the system was modeled, variables were identified, data was gathered, and comparisons were made between actual and theoretical data.

  13. Improved Space Surveillance Network (SSN) Scheduling using Artificial Intelligence Techniques

    NASA Astrophysics Data System (ADS)

    Stottler, D.

    There are close to 20,000 cataloged manmade objects in space, the large majority of which are not active, functioning satellites. These are tracked by phased array and mechanical radars and ground and space-based optical telescopes, collectively known as the Space Surveillance Network (SSN). A better SSN schedule of observations could, using exactly the same legacy sensor resources, improve space catalog accuracy through more complementary tracking, provide better responsiveness to real-time changes, better track small debris in low earth orbit (LEO) through efficient use of applicable sensors, efficiently track deep space (DS) frequent revisit objects, handle increased numbers of objects and new types of sensors, and take advantage of future improved communication and control to globally optimize the SSN schedule. We have developed a scheduling algorithm that takes as input the space catalog and the associated covariance matrices and produces a globally optimized schedule for each sensor site as to what objects to observe and when. This algorithm is able to schedule more observations with the same sensor resources and have those observations be more complementary, in terms of the precision with which each orbit metric is known, to produce a satellite observation schedule that, when executed, minimizes the covariances across the entire space object catalog. If used operationally, the results would be significantly increased accuracy of the space catalog with fewer lost objects with the same set of sensor resources. This approach inherently can also trade-off fewer high priority tasks against more lower-priority tasks, when there is benefit in doing so. Currently the project has completed a prototyping and feasibility study, using open source data on the SSN's sensors, that showed significant reduction in orbit metric covariances. The algorithm techniques and results will be discussed along with future directions for the research.

  14. Exploration Challenges: Transferring Ground Repair Techniques to Space Flight Application

    NASA Technical Reports Server (NTRS)

    McLemore, Carole A.; Kennedy, James P.; Rose, Frederick A.; Evans, Brian W.

    2007-01-01

    Fulfilling NASA's Vision for Space Exploration will demand an extended presence in space at distances from our home planet that exceed our current experience in space logistics and maintenance. The ability to perform repairs in lieu of the customary Orbital Replacement Unit (ORU) process where a faulty part is replaced will be elevated from contingency to routine to sustain operations. The use and cost effectiveness of field repairs for ground based operations in industry and the military have advanced with the development of technology in new materials, new repair techniques and new equipment. The unique environments, accessibility constraints and Extra Vehicular Activity (EVA) issues of space operations will require extensive assessment and evolution of these technologies to provide an equivalent and expected level of assurance to mission success. Challenges include the necessity of changes in design philosophy and policy, extremes in thermal cycling, disruptive forces (such as static charge and wind entrainment) on developed methods for control of materials, dramatically increased volatility of chemicals for cleaning and other compounds due to extremely low pressures, the limits imposed on dexterity and maneuverability by current EVA equipment and practices, and the necessity of unique verification methodology. This paper describes these challenges in and discusses the effects on the established ground techniques for repair. The paper also describes the leading repair methodology candidates and their beneficial attributes for resolving these issues with the evolution of technology.

  15. Multi-technique combination of space geodesy observations

    NASA Astrophysics Data System (ADS)

    Zoulida, Myriam; Pollet, Arnaud; Coulot, David; Biancale, Richard; Rebischung, Paul; Collilieux, Xavier

    2014-05-01

    Over the last few years, combination at the observation level (COL) of the different space geodesy techniques has been thoroughly studied. Various studies have shown that this type of combination can take advantage of common parameters. Some of these parameters, such as Zenithal Tropospheric Delays (ZTD), are available on co-location sites, where more than one technique is present. Local ties (LT) are provided for these sites, and act as intra-technique links and allow resulting terrestrial reference frames (TRF) to be homogeneous. However the use of LT can be problematic on weekly calculations, where their geographical distribution can be poor, and there are often differences observed between available LTs and space geodesy results. Similar co-locations can be found on multi-technique satellites, where more than one technique receiver is featured. A great advantage of these space ties (STs) is the densification of co-locations as the orbiting satellite acts as a moving station. The challenge of using space ties relies in the accurate knowledge or estimation of their values, as officially provided values are sometimes not reaching the required level of precision for the solution, due to receivers' or acting forces mismodelings and other factors. Thus, the necessity of an estimation and/or weighting strategy for the STs is introduced. To this day, on subsets of available data, using STs has shown promising results regarding the TRF determination through the stations' positions estimation, on the orbit determination of the GPS constellation and on the GPS antenna Phase Center Offsets and Variations (PCO and PCV) . In this study, results from a multi-technique combination including the Jason-2 satellite and its effect on the GNSS orbit determination during the CONT2011 period are presented, as well as some preliminary results on station positions' determination. Comparing resulting orbits with official solutions provides an assessment of the effect on the orbit

  16. Phase Space Tomography: A Simple, Portable and Accurate Technique to Map Phase Spaces of Beams with Space Charge

    SciTech Connect

    Stratakis, D.; Kishek, R. A.; Bernal, S.; Walter, M.; Haber, I.; Fiorito, R.; Thangaraj, J. C. T.; Quinn, B.; Reiser, M.; O'Shea, P. G.; Li, H.

    2006-11-27

    In order to understand the charged particle dynamics, e.g. the halo formation, emittance growth, x-y energy transfer and coupling, knowledge of the actual phase space is needed. Other the past decade there is an increasing number of articles who use tomography to map the beam phase space and measure the beam emittance. These studies where performed at high energy facilities where the effect of space charge was neglible and therefore not considered in the analysis. This work extends the tomography technique to beams with space charge. In order to simplify the analysis linear forces where assumed. By carefully modeling the tomography process using the particle-in-cell code WARP we test the validity of our assumptions and the accuracy of the reconstructed phase space. Finally, we report experimental results of phase space mapping at the University of Maryland Electron Ring (UMER) using tomography.

  17. Metrics for in-space telescope assembly techniques

    NASA Technical Reports Server (NTRS)

    Stephens, S.; Willenberg, H. J.

    2003-01-01

    Reliable metrics are not yet available for choosing among human and robotic assets for space-based construction and servicing of large space telescopes. Using FAIR-DART as a reference design, we generated example event sequences for telescope assembly scenarios in enough detail to identify infrastructure assumptions and technology requirements. A systems trade among human and robotic techniques (human EVA, on-site telerobotic, ground-in-the- loop robotic, commanded or sequenced robotic, and autonomous/decision-making robotic) helped us to define key metrics in the human-robotic trade space, including quality, time, cost, and risk. Our methodology included examining representative end-member scenarios. Case A treated each step in the assembly sequence as if all other steps have no on-site human involvement, and Case B treated each step as if human EVA is already involved in all other steps. With this trade, we identified key enabling technologies and infrastructure for space-based assembly and servicing of large space telescopes.

  18. Methods and Techniques for Risk Prediction of Space Shuttle Upgrades

    NASA Technical Reports Server (NTRS)

    Hoffman, Chad R.; Pugh, Rich; Safie, Fayssal

    1998-01-01

    Since the Space Shuttle Accident in 1986, NASA has been trying to incorporate probabilistic risk assessment (PRA) in decisions concerning the Space Shuttle and other NASA projects. One major study NASA is currently conducting is in the PRA area in establishing an overall risk model for the Space Shuttle System. The model is intended to provide a tool to predict the Shuttle risk and to perform sensitivity analyses and trade studies including evaluation of upgrades. Marshall Space Flight Center (MSFC) and its prime contractors including Pratt and Whitney (P&W) are part of the NASA team conducting the PRA study. MSFC responsibility involves modeling the External Tank (ET), the Solid Rocket Booster (SRB), the Reusable Solid Rocket Motor (RSRM), and the Space Shuttle Main Engine (SSME). A major challenge that faced the PRA team is modeling the shuttle upgrades. This mainly includes the P&W High Pressure Fuel Turbopump (HPFTP) and the High Pressure Oxidizer Turbopump (HPOTP). The purpose of this paper is to discuss the various methods and techniques used for predicting the risk of the P&W redesigned HPFTP and HPOTP.

  19. Advanced regenerative-cooling techniques for future space transportation systems

    NASA Technical Reports Server (NTRS)

    Wagner, W. R.; Shoji, J. M.

    1975-01-01

    A review of regenerative-cooling techniques applicable to advanced planned engine designs for space booster and orbit transportation systems has developed the status of the key elements of this cooling mode. This work is presented in terms of gas side, coolant side, wall conduction heat transfer, and chamber life fatigue margin considerations. Described are preliminary heat transfer and trade analyses performed using developed techniques combining channel wall construction with advanced, high-strength, high-thermal-conductivity materials (NARloy-Z or Zr-Cu alloys) in high heat flux regions, combined with lightweight steel tubular nozzle wall construction. Advanced cooling techniques such as oxygen cooling and dual-mode hydrocarbon/hydrogen fuel operation and their limitations are indicated for the regenerative cooling approach.

  20. A New Method for Estimating Bacterial Abundances in Natural Samples using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Cleaves, H. James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L.

    2004-01-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert were heated to a temperature of 500 C for several seconds under reduced pressure. The sublimate was collected on a cold finger and the amount of adenine released from the samples then determined by high performance liquid chromatography (HPLC) with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approx. l0(exp 5) to l0(exp 9) E. coli cell equivalents per gram. For most of these samples, the sublimation based cell counts were in agreement with total bacterial counts obtained by traditional DAPI staining. The simplicity and robustness of the sublimation technique compared to the DAPI staining method makes this approach particularly attractive for use by spacecraft instrumentation. NASA is currently planning to send a lander to Mars in 2009 in order to assess whether or not organic compounds, especially those that might be associated with life, are present in Martian surface samples. Based on our analyses of the Atacama Desert soil samples, several million bacterial cells per gam of Martian soil should be detectable using this sublimation technique.

  1. Surveying co-located space geodesy techniques for ITRF computation

    NASA Astrophysics Data System (ADS)

    Sarti, P.; Sillard, P.; Vittuari, L.

    2003-04-01

    We present a comprehensive operational methodology, based on classical geodesy triangulation and trilateration, that allows the determination of reference points of the five space geodesy techniques used in ITRF computation (i.e.: DORIS, GPS, LLR, SLR, VLBI). Most of the times, for a single technique, the reference point is not accessible and measurable directly. Likewise, no mechanically determined ex-center with respect to an external and measurable point is usually given. In these cases, it is not possible to directly measure the sought reference points and it is even less straightforward to obtain the statistical information relating these points for different techniques. We outline the most general practical surveying methodology that permits to recover the reference points of the different techniques regardless of their physical materialization. We also give a detailed analytical approach for less straightforward cases (e.g.: non geodetic VLBI antennae and SLR/LLR systems). We stress the importance of surveying instrumentation and procedure in achieving the best possible results and outline the impact of the information retrieved with our method in ITRF computation. In particular, we will give numerical examples of computation of the reference point of VLBI antennae (Ny Aalesund and Medicina) and the ex-centre vector computation linking co-located VLBI and GPS techniques in Medicina (Italy). A special attention was paid to the rigorous derivation of statistical elements. They will be presented in an other presentation.

  2. Improved Differential Evolution with Shrinking Space Technique for Constrained Optimization

    NASA Astrophysics Data System (ADS)

    Fu, Chunming; Xu, Yadong; Jiang, Chao; Han, Xu; Huang, Zhiliang

    2017-05-01

    Most of the current evolutionary algorithms for constrained optimization algorithm are low computational efficiency. In order to improve efficiency, an improved differential evolution with shrinking space technique and adaptive trade-off model, named ATMDE, is proposed to solve constrained optimization problems. The proposed ATMDE algorithm employs an improved differential evolution as the search optimizer to generate new offspring individuals into evolutionary population. For the constraints, the adaptive trade-off model as one of the most important constraint-handling techniques is employed to select better individuals to retain into the next population, which could effectively handle multiple constraints. Then the shrinking space technique is designed to shrink the search region according to feedback information in order to improve computational efficiency without losing accuracy. The improved DE algorithm introduces three different mutant strategies to generate different offspring into evolutionary population. Moreover, a new mutant strategy called "DE/rand/best/1" is constructed to generate new individuals according to the feasibility proportion of current population. Finally, the effectiveness of the proposed method is verified by a suite of benchmark functions and practical engineering problems. This research presents a constrained evolutionary algorithm with high efficiency and accuracy for constrained optimization problems.

  3. Testing Different Survey Techniques to Model Architectonic Narrow Spaces

    NASA Astrophysics Data System (ADS)

    Mandelli, A.; Fassi, F.; Perfetti, L.; Polari, C.

    2017-08-01

    In the architectural survey field, there has been the spread of a vast number of automated techniques. However, it is important to underline the gap that exists between the technical specification sheet of a particular instrument and its usability, accuracy and level of automation reachable in real cases scenario, especially speaking about Cultural Heritage (CH) field. In fact, even if the technical specifications (range, accuracy and field of view) are known for each instrument, their functioning and features are influenced by the environment, shape and materials of the object. The results depend more on how techniques are employed than the nominal specifications of the instruments. The aim of this article is to evaluate the real usability, for the 1:50 architectonic restitution scale, of common and not so common survey techniques applied to the complex scenario of dark, intricate and narrow spaces such as service areas, corridors and stairs of Milan's cathedral indoors. Tests have shown that the quality of the results is strongly affected by side-issues like the impossibility of following the theoretical ideal methodology when survey such spaces. The tested instruments are: the laser scanner Leica C10, the GeoSLAM ZEB1, the DOT DPI 8 and two photogrammetric setups, a full frame camera with a fisheye lens and the NCTech iSTAR, a panoramic camera. Each instrument presents advantages and limits concerning both the sensors themselves and the acquisition phase.

  4. Experimental determination of ice sublimation energies

    NASA Astrophysics Data System (ADS)

    Luna, R.; Canto, J.; Satorre, M. A.; Domingo, M.

    2011-11-01

    In Astrophysics, the study of ices is important due to the wide range of scenarios in which they are present. Their physical and chemical characteristics play an important role in the study of the interstellar medium (ISM). The assessment of the energy of sublimation allows us to improve our understanding of physical and/or chemical processes that take place where ices are present. The energy of sublimation E_sub is defined as the change of energy between solid and gas phase of certain molecule. This value is important to determinate other thermodynamical parameters such as the reticular energy of ionic compounds, the energy of formation in gas phase from the energy of formation in condensed phase, or to estimate the sublimation rate, which is very important in determining the evolution of surfaces of astrophysical objects.

  5. Artificial intelligence techniques for scheduling Space Shuttle missions

    NASA Technical Reports Server (NTRS)

    Henke, Andrea L.; Stottler, Richard H.

    1994-01-01

    Planning and scheduling of NASA Space Shuttle missions is a complex, labor-intensive process requiring the expertise of experienced mission planners. We have developed a planning and scheduling system using combinations of artificial intelligence knowledge representations and planning techniques to capture mission planning knowledge and automate the multi-mission planning process. Our integrated object oriented and rule-based approach reduces planning time by orders of magnitude and provides planners with the flexibility to easily modify planning knowledge and constraints without requiring programming expertise.

  6. Techniques for assessment of flexible space structure control performance

    NASA Technical Reports Server (NTRS)

    Rowell, Lawrence F.

    1988-01-01

    Several multivariable concepts are presently applied to both the open-loop and closed-loop analysis of a wrap-rib antenna space structure. After evaluating the alternative placements of sensors and actuators by means of controllability, observability, and transmission-zero concepts, the linear quadratic gaussian/loop transfer recovery method is used to synthesize a control law for suppression of the transient vibrations that are typically encountered during maneuvers. The integration of these techniques and associated computer programs into a larger spacecraft design system is also discussed.

  7. Multiclass Bayes error estimation by a feature space sampling technique

    NASA Technical Reports Server (NTRS)

    Mobasseri, B. G.; Mcgillem, C. D.

    1979-01-01

    A general Gaussian M-class N-feature classification problem is defined. An algorithm is developed that requires the class statistics as its only input and computes the minimum probability of error through use of a combined analytical and numerical integration over a sequence simplifying transformations of the feature space. The results are compared with those obtained by conventional techniques applied to a 2-class 4-feature discrimination problem with results previously reported and 4-class 4-feature multispectral scanner Landsat data classified by training and testing of the available data.

  8. Multiclass Bayes error estimation by a feature space sampling technique

    NASA Technical Reports Server (NTRS)

    Mobasseri, B. G.; Mcgillem, C. D.

    1979-01-01

    A general Gaussian M-class N-feature classification problem is defined. An algorithm is developed that requires the class statistics as its only input and computes the minimum probability of error through use of a combined analytical and numerical integration over a sequence simplifying transformations of the feature space. The results are compared with those obtained by conventional techniques applied to a 2-class 4-feature discrimination problem with results previously reported and 4-class 4-feature multispectral scanner Landsat data classified by training and testing of the available data.

  9. A High Performance Image Data Compression Technique for Space Applications

    NASA Technical Reports Server (NTRS)

    Yeh, Pen-Shu; Venbrux, Jack

    2003-01-01

    A highly performing image data compression technique is currently being developed for space science applications under the requirement of high-speed and pushbroom scanning. The technique is also applicable to frame based imaging data. The algorithm combines a two-dimensional transform with a bitplane encoding; this results in an embedded bit string with exact desirable compression rate specified by the user. The compression scheme performs well on a suite of test images acquired from spacecraft instruments. It can also be applied to three-dimensional data cube resulting from hyper-spectral imaging instrument. Flight qualifiable hardware implementations are in development. The implementation is being designed to compress data in excess of 20 Msampledsec and support quantization from 2 to 16 bits. This paper presents the algorithm, its applications and status of development.

  10. Techniques and Tools of NASA's Space Shuttle Columbia Accident Investigation

    NASA Technical Reports Server (NTRS)

    McDanels, Steve J.

    2005-01-01

    The Space Shuttle Columbia accident investigation was a fusion of many disciplines into a single effort. From the recovery and reconstruction of the debris, Figure 1, to the analysis, both destructive and nondestructive, of chemical and metallurgical samples, Figure 2, a multitude of analytical techniques and tools were employed. Destructive and non-destructive testing were utilized in tandem to determine if a breach in the left wing of the Orbiter had occurred, and if so, the path of the resultant high temperature plasma flow. Nondestructive analysis included topometric scanning, laser mapping, and real-time radiography. These techniques were useful in constructing a three dimensional virtual representation of the reconstruction project, specifically the left wing leading edge reinforced carbon/carbon heat protectant panels. Similarly, they were beneficial in determining where sampling should be performed on the debris. Analytic testing included such techniques as Energy Dispersive Electron Microprobe Analysis (EMPA), Electron Spectroscopy Chemical Analysis (ESCA), and X-Ray dot mapping; these techniques related the characteristics of intermetallics deposited on the leading edge of the left wing adjacent to the location of a suspected plasma breach during reentry. The methods and results of the various analyses, along with their implications into the accident, are discussed, along with the findings and recommendations of the Columbia Accident Investigation Board. Likewise, NASA's Return To Flight efforts are highlighted.

  11. System and method for suppressing sublimation using opacified aerogel

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeff S. (Inventor); Snyder, G. Jeffrey (Inventor); Calliat, Thierry (Inventor); Fleurial, Jean-Pierre (Inventor); Jones, Steven M. (Inventor); Palk, Jong-Ah (Inventor)

    2008-01-01

    The present invention relates to a castable, aerogel-based, ultra-low thermal conductivity opacified insulation to suppress sublimation. More specifically, the present invention relates to an aerogel opacified with various opacifying or reflecting constituents to suppress sublimation and provide thermal insulation in thermoelectric modules. The opacifying constituent can be graded within the aerogel for increased sublimation suppression, and the density of the aerogel can similarly be graded to achieve optimal thermal insulation and sublimation suppression.

  12. Heat of Sublimation of I-2.

    ERIC Educational Resources Information Center

    Henderson, Giles; Robarts, Ronald A., Jr.

    1978-01-01

    Describes an inexpensive double-beam laser photometry experiment to determine the molar heat of sublimation of I-2. The experiment employs common laboratory materials and components and gives results with a two percent to three percent accuracy. (Author/GA)

  13. No reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1990-01-01

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with NHCO into a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid.

  14. NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1988-01-01

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with HNCO at a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid.

  15. Heat of Sublimation of I-2.

    ERIC Educational Resources Information Center

    Henderson, Giles; Robarts, Ronald A., Jr.

    1978-01-01

    Describes an inexpensive double-beam laser photometry experiment to determine the molar heat of sublimation of I-2. The experiment employs common laboratory materials and components and gives results with a two percent to three percent accuracy. (Author/GA)

  16. Using space geodetic techniques to estimate climate trends (Invited)

    NASA Astrophysics Data System (ADS)

    Nilsson, T.; Boehm, J.; Elgered, G.; Ning, T.; Schuh, H.

    2010-12-01

    Space geodetic techniques, such as Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI), have proven to be useful for measuring the atmospheric integrated water vapor (IWV). Some VLBI sites now have time series of 30 years while the first established GNSS sites have data for periods exceeding 15 years. Estimating long-term trends in the IWV from these data can be an indicator for climate change. The VLBI technique suffers from less serious systematic errors, while of course the temporal and spatial sampling provided by the growing number of continuously operating GNSS networks is a clear advantage of this technique. We have determined IWV trends using data from the national GNSS networks in Sweden and Finland, as well as from some other GNSS stations in Northern Europe. These trends are validated by comparisons to results from VLBI, radiosondes, and numerical weather models. The possible significance of the results for climate research is assessed through correlation studies between the IWV trends and corresponding trends in other relevant meteorological parameters, such as the ground temperature. We also investigate possible systematic errors that can affect the estimated trends and how such errors can be avoided.

  17. Using Combined SFTA and SFMECA Techniques for Space Critical Software

    NASA Astrophysics Data System (ADS)

    Nicodemos, F. G.; Lahoz, C. H. N.; Abdala, M. A. D.; Saotome, O.

    2012-01-01

    This work addresses the combined Software Fault Tree Analysis (SFTA) and Software Failure Modes, Effects and Criticality Analysis (SFMECA) techniques applied to space critical software of satellite launch vehicles. The combined approach is under research as part of the Verification and Validation (V&V) efforts to increase software dependability and as future application in other projects under development at Instituto de Aeronáutica e Espaço (IAE). The applicability of such approach was conducted on system software specification and applied to a case study based on the Brazilian Satellite Launcher (VLS). The main goal is to identify possible failure causes and obtain compensating provisions that lead to inclusion of new functional and non-functional system software requirements.

  18. Overview of arraying techniques in the deep space network

    NASA Technical Reports Server (NTRS)

    Mileant, A.; Hinedi, S.

    1991-01-01

    Four different arraying schemes that can be used by the Deep Space Network are functionally discussed and compared. These include symbol stream combining (SSC), baseband combining (BC), carrier arraying (CA), and full spectrum combining (FSC). In addition, sibeband aiding (SA) is also included and compared even though it is not an arraying scheme, since it uses a single antenna. Moreover, combinations of these schemes are discussed, such as carrier arraying with sideband aiding and baseband combining (CA/SA/BC) or carrier arraying with symbol stream combining (CA/SSC). Complexity versus performance is traded off and the benefits to the reception of existing spacecraft signals are discussed. Recommendations are made as to the best techniques for particular configurations.

  19. Dispersion analysis techniques within the space vehicle dynamics simulation program

    NASA Technical Reports Server (NTRS)

    Snow, L. S.; Kuhn, A. E.

    1975-01-01

    The Space Vehicle Dynamics Simulation (SVDS) program was evaluated as a dispersion analysis tool. The Linear Error Analysis (LEA) post processor was examined in detail and simulation techniques relative to conducting a dispersion analysis using the SVDS were considered. The LEA processor is a tool for correlating trajectory dispersion data developed by simulating 3 sigma uncertainties as single error source cases. The processor combines trajectory and performance deviations by a root-sum-square (RSS process) and develops a covariance matrix for the deviations. Results are used in dispersion analyses for the baseline reference and orbiter flight test missions. As a part of this study, LEA results were verified as follows: (A) Hand calculating the RSS data and the elements of the covariance matrix for comparison with the LEA processor computed data. (B) Comparing results with previous error analyses. The LEA comparisons and verification are made at main engine cutoff (MECO).

  20. Space Shuttle stability and control flight test techniques

    NASA Technical Reports Server (NTRS)

    Cooke, D. R.

    1980-01-01

    A unique approach for obtaining vehicle aerodynamic characteristics during entry has been developed for the Space Shuttle. This is due to the high cost of Shuttle testing, the need to open constraints for operational flights, and the fact that all flight regimes are flown starting with the first flight. Because of uncertainties associated with predicted aerodynamic coefficients, nine flight conditions have been identified at which control problems could occur. A detailed test plan has been developed for testing at these conditions and is presented. Due to limited testing, precise computer initiated maneuvers are implemented. These maneuvers are designed to optimize the vehicle motion for determining aerodynamic coefficients. Special sensors and atmospheric measurements are required to provide stability and control flight data during an entire entry. The techniques employed in data reduction are proven programs developed and used at NASA/DFRC.

  1. The enthalpy of sublimation and thermodynamic functions of fermium

    SciTech Connect

    Haire, R.G.; Gibson, J.K. , Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6375 )

    1989-12-01

    The enthalpy of sublimation of fermium (Fm), element 100, has now been determined directly by measuring the partial pressure of Fm over alloys, for the temperature range of 642 to 905 K. The partial pressures were determined using Knudsen effusion and target collection techniques. Dilute (10{sup {minus}5}--10{sup {minus}7} atom %) solid alloys of Fm and mixtures of Fm and Es in both Sm and Yb solvents were studied. The presence of Es in two of the alloys allowed a direct comparison of the behavior of Fm and Es, where the latter could be used as a reference. It was possible to calculate enthalpies of sublimation and a hypothetical vapor pressure/temperature relationship for pure Fm metal by selecting Yb as the solvent most likely to form a nearly ideal alloy with Fm. From the experimental vapor pressure data, we derived average Second Law values of 33.8{plus minus}3 kcal/mol and 23.5{plus minus}3 cal/mol deg for the enthalpy and entropy of sublimation of Fm at 298 K. Third Law enthalpy values were also calculated using the experimental partial pressure data and entropies estimated from derived free energy functions and heat capacities for the solid and gaseous forms of Fm. The average Third Law values (34.8 kcal/mol and 25.1 cal/mol deg, respectively, at 298 K) are in agreement with those obtained via the Second Law. These results establish that Fm, like Es (element 99), is a divalent metal. The finding that Fm metal is the second divalent actinide element experimentally establishes the trend towards metallic divalency expected in the second half of the actinide series.

  2. An improved astrometric calibration technique for space debris observation

    NASA Astrophysics Data System (ADS)

    Sun, Rong-Yu; Zhao, Chang-Yin; Lu, Yao

    2016-02-01

    An optical survey is the main technique for detecting space debris. Due to the specific characteristics of observation, the pointing errors and tracking errors of the telescope as well as image degradation may be significant, which make it difficult for astrometric calibration. Here we present an improved method that corrects the pointing and tracking errors, and measures the image position precisely. The pipeline is tested on a number of CCD images obtained from a 1-m telescope administered by Xinjiang Astronomical Observatory while observing a GPS satellite. The results show that the position measurement error of the background stars is around 0.1 pixel, while the time cost for a single frame is about 7.5 s; hence the reliability and accuracy of our method are demonstrated. In addition, our method shows a versatile and feasible way to perform space debris observation utilizing non-dedicated telescopes, which means more sensors could be involved and the ability to perform surveys could be improved.

  3. Vapor pressures and enthalpies of sublimation of polycyclic aromatic hydrocarbons and their derivatives

    SciTech Connect

    Oja, V.; Suuberg, E.M.

    1998-05-01

    The vapor pressures of a series of polycyclic aromatic hydrocarbons (PAH) and heteroatom-containing PAH have been measured using the Knudsen effusion technique. Aromatic hydrocarbons examined included anthracene, phenanthrene, pyrene, 2,3-benzofluorene, naphthacene, perylene, pentacene, and coronene. Heteroatomic aromatic species examined included phenanthridine, perinaphthenone, 3-hydroxy-1-phenalen-1-one, benz[g]isoquinoline-5,10-dione, 1,2-benzodiphenylene sulfide, 1-hydroxypyrene, and 6,11-dihydroxy-5,12-naphthacenedione. The measurements were all made in the solid sublimation regime, and enthalpies of sublimation were calculated from the Clausius-Clapeyron equation.

  4. New method for estimating bacterial cell abundances in natural samples by use of sublimation.

    PubMed

    Glavin, Daniel P; Cleaves, H James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L

    2004-10-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.

  5. Conduction type control from n to p type for organic pigment films purified by reactive sublimation

    NASA Astrophysics Data System (ADS)

    Hiramoto, Masahiro; Ihara, Kiyoaki; Fukusumi, Hiroyuki; Yokoyama, Masaaki

    1995-12-01

    The effects of purification by reactive sublimation technique and bromine doping on the Fermi level and the photovoltaic properties of n-type perylene pigment films were investigated. Photovoltage arisen from the Schottky junction between n-type perylene pigment film and Au increased significantly by repeating the train sublimation under methylamine gas atmosphere. This phenomenon was revealed to be due to the negative shift of the Fermi level resulting from the effective removal of unknown but specific impurity acting as an acceptor by reactive sublimation. On the other hand, by bromine doping, Fermi level of the pigment film shifted largely to a positive direction and reached the nearby valence band, while the direction of photocurrent flow arising from the Schottky junction with Au was reversed. This result is a clear demonstration of alternating the type of conduction from n type to p type. This means that the pn control of organic semiconductors is possible.

  6. New method for estimating bacterial cell abundances in natural samples by use of sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Cleaves, H. James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L.

    2004-01-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.

  7. New method for estimating bacterial cell abundances in natural samples by use of sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Cleaves, H. James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L.

    2004-01-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.

  8. Numerical simulation of drifting snow sublimation in the saltation layer

    PubMed Central

    Dai, Xiaoqing; Huang, Ning

    2014-01-01

    Snow sublimation is an important hydrological process and one of the main causes of the temporal and spatial variation of snow distribution. Compared with surface sublimation, drifting snow sublimation is more effective due to the greater surface exposure area of snow particles in the air. Previous studies of drifting snow sublimation have focused on suspended snow, and few have considered saltating snow, which is the main form of drifting snow. In this study, a numerical model is established to simulate the process of drifting snow sublimation in the saltation layer. The simulated results show 1) the average sublimation rate of drifting snow particles increases linearly with the friction velocity; 2) the sublimation rate gradient with the friction velocity increases with increases in the environmental temperature and the undersaturation of air; 3) when the friction velocity is less than 0.525 m/s, the snowdrift sublimation of saltating particles is greater than that of suspended particles; and 4) the snowdrift sublimation in the saltation layer is less than that of the suspended particles only when the friction velocity is greater than 0.625 m/s. Therefore, the drifting snow sublimation in the saltation layer constitutes a significant portion of the total snow sublimation. PMID:25312383

  9. Undergraduate Laboratory Experiment Facilitating Active Learning of Concepts in Transport Phenomena: Experiment with a Subliming Solid

    ERIC Educational Resources Information Center

    Utgikar, Vivek P.

    2015-01-01

    An experiment based on the sublimation of a solid was introduced in the undergraduate Transport Phenomena course. The experiment required the students to devise their own apparatus and measurement techniques. The theoretical basis, assignment of the experiment, experimental results, and student/instructor observations are described in this paper.…

  10. Undergraduate Laboratory Experiment Facilitating Active Learning of Concepts in Transport Phenomena: Experiment with a Subliming Solid

    ERIC Educational Resources Information Center

    Utgikar, Vivek P.

    2015-01-01

    An experiment based on the sublimation of a solid was introduced in the undergraduate Transport Phenomena course. The experiment required the students to devise their own apparatus and measurement techniques. The theoretical basis, assignment of the experiment, experimental results, and student/instructor observations are described in this paper.…

  11. Objective techniques for psychological assessment, phase 2. [techniques for measuring human performance during space flight stress

    NASA Technical Reports Server (NTRS)

    Wortz, E. C.; Saur, A. J.; Nowlis, D. P.; Kendall, M. P.

    1974-01-01

    Results are presented of an initial experiment in a research program designed to develop objective techniques for psychological assessment of individuals and groups participating in long-duration space flights. Specifically examined is the rationale for utilizing measures of attention as an objective assessment technique. Subjects participating in the experiment performed various tasks (eg, playing matrix games which appeared on a display screen along with auditory stimuli). The psychophysiological reactions of the subjects were measured and are given. Previous research of various performance and psychophysiological methods of measuring attention is also discussed. The experiment design (independent and dependent variables) and apparatus (computers and display devices) are described and shown. Conclusions and recommendations are presented.

  12. A Comparison Between Orion Automated and Space Shuttle Rendezvous Techniques

    NASA Technical Reports Server (NTRS)

    Ruiz, Jose O,; Hart, Jeremy

    2010-01-01

    architecture and contrast it with shuttle rendezvous techniques and circumstances. The shuttle rendezvous profile is timed to take approximately 3 days from orbit insertion to docking at the International Space Station (ISS). This process can be divided into 3 phases: far-field, mid-field and proximity operations. The far-field stage is characterized as the most quiescent phase. The spacecraft is usually too far to navigate using relative sensors and uses the Inertial Measurement Units (IMU s) to numerically solve for its position. The maneuvers are infrequent, roughly twice per day, and are larger than other burns in the profile. The shuttle uses this opportunity to take extensive ground based radar updates and keep high fidelity orbit states on the ground. This state is then periodically uplinked to the shuttle computers. The targeting solutions for burn maneuvers are also computed on the ground and uplinked. During the burn the crew is responsible for setting the shuttle attitude and configuring the propulsion system for ignition. Again this entire process is manually driven by both crew and ground activity. The only automatic processes that occur are associated with the real-time execution of the burn. The Orion automated functionality will seek to relieve the workload of both the crew and ground during this phase

  13. Applications of dynamic scheduling technique to space related problems: Some case studies

    NASA Technical Reports Server (NTRS)

    Nakasuka, Shinichi; Ninomiya, Tetsujiro

    1994-01-01

    The paper discusses the applications of 'Dynamic Scheduling' technique, which has been invented for the scheduling of Flexible Manufacturing System, to two space related scheduling problems: operation scheduling of a future space transportation system, and resource allocation in a space system with limited resources such as space station or space shuttle.

  14. Psychotherapy. Sublimation and the psychodynamics of birding.

    PubMed

    Clemens, Norman A

    2012-07-01

    An adventure in extreme birding prompted the psychoanalyst author to reflect on "why do people do this?" Like myriad human interests, vocations, and avocations, the activity of bird watching is a socially acceptable activity that is the final pathway for multiple motivations that are likely to have a long history in the individual's development. It may have origins in basic survival skills. Various psychological defense mechanisms may be involved, the most mature and successful one being sublimation. Success of a defense-like sublimation may be viewed in terms of freedom from anxiety or from obsessive extremes that interfere with the individual's wellbeing, important relationships, or physical or financial health. The author considers whether the characters in the film The Big Year exemplify such success or the lack of it.

  15. Core-shell-like Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS heterostructure synthesized by super-close-space sublimation for broadband down-conversion

    NASA Astrophysics Data System (ADS)

    Wu, Xiaojie; Zhang, Zhenzhong; Meng, Fanzhi; Yu, Yingning; Han, Lin; Liu, Xiaojuan; Meng, Jian

    2014-04-01

    Combination with semiconductors is a promising approach to the realization of broadband excitation of light conversion materials based on rare earth compounds, to boost the energy efficiency of silicon solar cells. Cd1-xZnxS is a wide bandgap semiconductor with large exciton binding energy. By changing its composition, the bandgap of Cd1-xZnxS can be tuned to match the absorption of trivalent lanthanide (Ln) ions, which makes it a competent energy donor for the Ln3+-Yb3+ couple. In this work, we designed a clean route to a broadband down-converter based on a core-shell-like Y2O3:[(Tb3+-Yb3+), Li+]/Cd0.81Zn0.19S (CdZnS) heterostructure. By hot-pressing and subsequent annealing of a Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS mixture, highly pure CdZnS was sublimated and deposited on the Y2O3:[(Tb3+-Yb3+), Li+] grains while maintaining the original composition of the precursor. The CdZnS shell acted as a light absorber and energy donor for the Tb3+-Yb3+ quantum cutting couple. Because the use of solvents was avoided during the formation of the heterostructures, few impurities were incorporated into the samples, and the non-radiative transition was therefore markedly suppressed. The Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS heterostructures possess strong near-infrared (NIR) luminescence from Yb3+. Broadband down-conversion to the Yb3+ NIR emission was obtained in a wide range of 250-650 nm.

  16. Core-shell-like Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS heterostructure synthesized by super-close-space sublimation for broadband down-conversion.

    PubMed

    Wu, Xiaojie; Zhang, Zhenzhong; Meng, Fanzhi; Yu, Yingning; Han, Lin; Liu, Xiaojuan; Meng, Jian

    2014-05-07

    Combination with semiconductors is a promising approach to the realization of broadband excitation of light conversion materials based on rare earth compounds, to boost the energy efficiency of silicon solar cells. Cd(1-x)Zn(x)S is a wide bandgap semiconductor with large exciton binding energy. By changing its composition, the bandgap of Cd(1-x)Zn(x)S can be tuned to match the absorption of trivalent lanthanide (Ln) ions, which makes it a competent energy donor for the Ln(3+)-Yb(3+) couple. In this work, we designed a clean route to a broadband down-converter based on a core-shell-like Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/Cd0.81Zn0.19S (CdZnS) heterostructure. By hot-pressing and subsequent annealing of a Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/CdZnS mixture, highly pure CdZnS was sublimated and deposited on the Y2O3:[(Tb(3+)-Yb(3+)), Li(+)] grains while maintaining the original composition of the precursor. The CdZnS shell acted as a light absorber and energy donor for the Tb(3+)-Yb(3+) quantum cutting couple. Because the use of solvents was avoided during the formation of the heterostructures, few impurities were incorporated into the samples, and the non-radiative transition was therefore markedly suppressed. The Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/CdZnS heterostructures possess strong near-infrared (NIR) luminescence from Yb(3+). Broadband down-conversion to the Yb(3+) NIR emission was obtained in a wide range of 250-650 nm.

  17. No reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert

    1989-01-01

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with HNCO at a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid and CO or other H-atom generating species is also present or added to the gas stream.

  18. AI techniques for a space application scheduling problem

    NASA Technical Reports Server (NTRS)

    Thalman, N.; Sparn, T.; Jaffres, L.; Gablehouse, D.; Judd, D.; Russell, C.

    1991-01-01

    Scheduling is a very complex optimization problem which can be categorized as an NP-complete problem. NP-complete problems are quite diverse, as are the algorithms used in searching for an optimal solution. In most cases, the best solutions that can be derived for these combinatorial explosive problems are near-optimal solutions. Due to the complexity of the scheduling problem, artificial intelligence (AI) can aid in solving these types of problems. Some of the factors are examined which make space application scheduling problems difficult and presents a fairly new AI-based technique called tabu search as applied to a real scheduling application. the specific problem is concerned with scheduling application. The specific problem is concerned with scheduling solar and stellar observations for the SOLar-STellar Irradiance Comparison Experiment (SOLSTICE) instrument in a constrained environment which produces minimum impact on the other instruments and maximizes target observation times. The SOLSTICE instrument will gly on-board the Upper Atmosphere Research Satellite (UARS) in 1991, and a similar instrument will fly on the earth observing system (Eos).

  19. Sublimation as a Continuous and Transient Source of Water in Europa's Exosphere

    NASA Astrophysics Data System (ADS)

    Hayne, Paul O.

    2016-10-01

    Europa's crust is composed primarily of water ice, which may be vaporized by sputtering and sublimation when exposed to the jovian radiation environment. Models of H2O in Europa's exosphere have focused primarily on the contribution of sputtering by energetic particles, with globally averaged production rates estimated to be ~1015 H2O m-2 s-1. Although sublimation rates at Europa's average dayside temperature of ~106 K are much lower at ~1010 H2O m-2 s-1, surfaces at low- to mid-latitude experiences temperatures in excess of 130 K, with expected sublimation rates of >1015 H2O m-2 s-1 possible. These production rates would be reduced where the surface ice is mixed with impurities, or through development of a non-ice lag deposit. In addition to the continuous flux due to sublimation, transient outgassing may be caused by exposure of fresh ice to direct sunlight, for example by mass wasting on steep slopes. Here, we revisit the process of sublimation on Europa's surface to quantify possible H2O vapor production on a range of spatial and temporal scales.The model includes solar heating, conduction, and vapor diffusion. Temperatures and sublimation rates are calculated by the instantaneous energy budget within each model layer, and outgassing to the exosphere depends on the surface vapor pressure and molecular thermal velocities. Vapor densities and line-of-sight column abundances can be directly compared to observations. Our results show that for surfaces composed of pure ice, sublimation contributes significant quantities to the dayside exosphere. The production rate declines as a sublimation lag develops, with a characteristic timescale of ~1 - 10 kyr at the equator. Freshly exposed ice may produce localized sources. For example, a fresh exposure of ice at 60° latitude with dimension ~2 km would be expected to produce a line-of-sight column abundance of ~1020 H2O m-2 near the limb. However, expansion of the plume would lead to lower column abundance at higher

  20. Numerical Implementation of Surface Catalysis, Reaction, and Sublimation

    DTIC Science & Technology

    2007-07-01

    Sublimation RTO-EN-AVT-142 16 - 13 the pores, the vapor molecule decomposes into smaller molecules. This decomposition process absorbs heat and...less than that to the Galileo Probe. There, not only the sublimation but the eactions, Eqs. (15) and (16) could conceivably become important . Surface...RTO-EN-AVT-142 16 - 1 Park, C. (2007) Numerical Implementation of Surface Catalysis, Reaction, and Sublimation . In Experiment, Modeling and

  1. New Factorization Techniques and Fast Serial and Parrallel Algorithms for Operational Space Control of Robot Manipulators

    NASA Technical Reports Server (NTRS)

    Fijany, Amir; Djouani, Karim; Fried, George; Pontnau, Jean

    1997-01-01

    In this paper a new factorization technique for computation of inverse of mass matrix, and the operational space mass matrix, as arising in implementation of the operational space control scheme, is presented.

  2. Science Sublime: The Philosophy of the Sublime, Dewey's Aesthetics, and Science Education

    ERIC Educational Resources Information Center

    Cavanaugh, Shane

    2014-01-01

    Feelings of awe, wonder, and appreciation have been largely ignored in the working lives of scientists and, in turn, science education has not accurately portrayed science to students. In an effort to bring the affective qualities of science into the classroom, this work draws on the writings of the sublime by Burke, Kant, Emerson, and Wordsworth…

  3. Science Sublime: The Philosophy of the Sublime, Dewey's Aesthetics, and Science Education

    ERIC Educational Resources Information Center

    Cavanaugh, Shane

    2014-01-01

    Feelings of awe, wonder, and appreciation have been largely ignored in the working lives of scientists and, in turn, science education has not accurately portrayed science to students. In an effort to bring the affective qualities of science into the classroom, this work draws on the writings of the sublime by Burke, Kant, Emerson, and Wordsworth…

  4. Sublimation of ice-tholins mixtures: A morphological and spectro-photometric study

    NASA Astrophysics Data System (ADS)

    Poch, Olivier; Pommerol, Antoine; Jost, Bernhard; Carrasco, Nathalie; Szopa, Cyril; Thomas, Nicolas

    2016-03-01

    Sublimation, the direct transition from solid to gas phase, is a process responsible for shaping and changing the reflectance properties of many Solar System surfaces. In this study, we have characterized the evolution of the structure/texture and of the visible and near-infrared (VIS-NIR) spectral reflectance of surfaces made of water ice mixed with analogues of complex extraterrestrial organic matter, named tholins, under low temperature (<-70 °C) and pressure (10-5 mbar) conditions. The experiments were carried out in the SCITEAS simulation setup recently built as part of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern (Pommerol, A. et al. [2015a]. Planet. Space Sci. 109-110, 106-122). As the water ice sublimated, we observed in situ the formation of a sublimation lag deposit made of a water-free porous (>90% porosity) network of organic filaments on top of the ice. The temporal evolution of the tholins and water ice spectral features (reflectance at the absorption bands wavelengths, red slope, from 0.40 to 1.90 μm) are analyzed throughout the sublimation of the samples. We studied how different mixtures of tholins with water (0.1 wt.% tholins as coating or inclusions within the water particles), and different ice particle sizes (4.5 ± 2.5 or 67 ± 31 μm) influence the morphological and spectral evolutions of the samples. The sublimation of the ice below the mantle produces a gas flow responsible for the ejection of mm to cm-sized fragments of the deposit in outbursts-like events. The results show remarkable differences between these samples in term of mantle structure, speed of mantle building, rates and surface area of mantle ejections. These data provide useful references for interpreting remote-sensing observations of icy Solar System surfaces, in particular the activity of comet nuclei where sublimation of organic-rich ices and deposition of organic-dust particles likely play a major role. Consequently, the

  5. Reassessing Aesthetic Appreciation of Nature in the Kantian Sublime

    ERIC Educational Resources Information Center

    Brady, Emily

    2012-01-01

    The sublime has been a relatively neglected topic in recent work in philosophical aesthetics, with existing discussions confined mainly to problems in Kant's theory. Given the revival of interest in his aesthetic theory and the influence of the Kantian sublime compared to other eighteenth-century accounts, this focus is not surprising. Kant's…

  6. Reassessing Aesthetic Appreciation of Nature in the Kantian Sublime

    ERIC Educational Resources Information Center

    Brady, Emily

    2012-01-01

    The sublime has been a relatively neglected topic in recent work in philosophical aesthetics, with existing discussions confined mainly to problems in Kant's theory. Given the revival of interest in his aesthetic theory and the influence of the Kantian sublime compared to other eighteenth-century accounts, this focus is not surprising. Kant's…

  7. Generalized Orbital Projections of a Sublimating Ice Particle

    NASA Technical Reports Server (NTRS)

    Menkin, Evgeny; Bacon, Jack

    2006-01-01

    The issue of orbital debris resulting from human activities in space is a growing concern for the space users' community. Waste generated in Low Earth Orbit (LEO) can stay in orbit for a long time, creating significant hazards for other spacecraft flying at lower intercepting orbits. Many spacecraft, especially crewed vehicles, are required to vent fluids into space. These fluids include propellant, wastewater, excess condensate, and others. It is important to analyze the behavior of particles that result from these activities, since each individual particle is capable of damaging or destroying a spacecraft in a lower, crossing orbit, and such particles are invisible to tracking radar systems on the ground. The deorbit trajectory of an ice particle is complex. It depends on factors including attitude of the vehicle during vent, initial velocities of particles, altitude at which the vent occurred, and numerous evaporation and sublimation factors. These include contamination within the vented water, evolution of bubbles within the clear water, and sun flux factors such as time of the year and current beta angle. The purpose of this study is to examine the influences of these factors on the trajectories of ice particles resulting from condensate water dumps, and to bound the safe trajectories of spacecraft that lie below the venting spacecraft.

  8. Simulation of Ceres water sublimation and thermal state

    NASA Astrophysics Data System (ADS)

    De Sanctis, M.; Formisano, M.; Capria, M.; Capaccioni, F.; Ammannito, E.; Magni, G.; Bockelee-Morvan, D.; Raymond, C.; Russell, C.

    2014-07-01

    body is composed of water ice, dust, and organic materials, in specified proportions. Each dust distribution has different physical and thermal properties and the dust grains are distributed in different size classes. The surface temperature is derived from the balance among solar input, energy re-emitted in space, conducted in the interior and used to sublimate ices. A mesh of quadrilaterals describes the shape. The illumination for each of the facets making up the full shape is calculated by the angle between the local normal and the direction to the Sun. The thermal evolution of each grid surface is calculated by taking into account the solar illumination and the properties of the material on and beneath the surface. The heat diffusion through the porous mixture of ice and dust is computed, determining the water ice phase transition and the sublimation rate of the ices. The temperature is also computed for each element, providing thermal maps at the surface and at depth. We have developed several geophysical and thermal scenarios, changing the proportion of ice and dust, surface albedo, and the presence and absence of ice on (and below) the surface. From this first analysis, it seems that water ice layers located very deep inside the body (>100s meters below the surface) cannot account for such a relatively high flux. For having the water flux seen by [5], the icy layers must be much closer to the surface. The output of the different models is discussed.

  9. In situ transmission electron microscopy of cadmium selenide nanorod sublimation

    SciTech Connect

    Hellebusch, Daniel J.; Manthiram, Karthish; Beberwyck, Brandon J.; Alivisatos, A. Paul

    2015-01-23

    In situ electron microscopy is used to observe the morphological evolution of cadmium selenide nanorods as they sublime under vacuum at a series of elevated temperatures. Mass loss occurs anisotropically along the nanorod’s long axis. At temperatures close to the sublimation threshold, the phase change occurs from both tips of the nanorods and proceeds unevenly with periods of rapid mass loss punctuated by periods of relative stability. At higher temperatures, the nanorods sublime at a faster, more uniform rate, but mass loss occurs from only a single end of the rod. Furthermore, we propose a mechanism that accounts for the observed sublimation behavior based on the terrace–ledge–kink (TLK) model and how the nanorod surface chemical environment influences the kinetic barrier of sublimation.

  10. In situ transmission electron microscopy of cadmium selenide nanorod sublimation

    DOE PAGES

    Hellebusch, Daniel J.; Manthiram, Karthish; Beberwyck, Brandon J.; ...

    2015-01-23

    In situ electron microscopy is used to observe the morphological evolution of cadmium selenide nanorods as they sublime under vacuum at a series of elevated temperatures. Mass loss occurs anisotropically along the nanorod’s long axis. At temperatures close to the sublimation threshold, the phase change occurs from both tips of the nanorods and proceeds unevenly with periods of rapid mass loss punctuated by periods of relative stability. At higher temperatures, the nanorods sublime at a faster, more uniform rate, but mass loss occurs from only a single end of the rod. Furthermore, we propose a mechanism that accounts for themore » observed sublimation behavior based on the terrace–ledge–kink (TLK) model and how the nanorod surface chemical environment influences the kinetic barrier of sublimation.« less

  11. In Situ Transmission Electron Microscopy of Cadmium Selenide Nanorod Sublimation.

    PubMed

    Hellebusch, Daniel J; Manthiram, Karthish; Beberwyck, Brandon J; Alivisatos, A Paul

    2015-02-19

    In situ electron microscopy is used to observe the morphological evolution of cadmium selenide nanorods as they sublime under vacuum at a series of elevated temperatures. Mass loss occurs anisotropically along the nanorod's long axis. At temperatures close to the sublimation threshold, the phase change occurs from both tips of the nanorods and proceeds unevenly with periods of rapid mass loss punctuated by periods of relative stability. At higher temperatures, the nanorods sublime at a faster, more uniform rate, but mass loss occurs from only a single end of the rod. We propose a mechanism that accounts for the observed sublimation behavior based on the terrace-ledge-kink (TLK) model and how the nanorod surface chemical environment influences the kinetic barrier of sublimation.

  12. A study of trends and techniques for space base electronics

    NASA Technical Reports Server (NTRS)

    Trotter, J. D.; Wade, T. E.; Gassaway, J. D.

    1978-01-01

    Furnaces and photolithography related equipment were applied to experiments on double layer metal. The double layer metal activity emphasized wet chemistry techniques. By incorporating the following techniques: (1) ultrasonic etching of the vias; (2) premetal clean using a modified buffered hydrogen fluoride; (3) phosphorus doped vapor; and (4) extended sintering, yields of 98 percent were obtained using the standard test pattern. The two dimensional modeling problems have stemmed from, alternately, instability and too much computation time to achieve convergence.

  13. Improved Space Object Observation Techniques Using CMOS Detectors

    NASA Astrophysics Data System (ADS)

    Schildknecht, T.; Hinze, A.; Schlatter, P.; Silha, J.; Peltonen, J.; Santti, T.; Flohrer, T.

    2013-08-01

    CMOS-sensors, or in general Active Pixel Sensors (APS), are rapidly replacing CCDs in the consumer camera market. Due to significant technological advances during the past years these devices start to compete with CCDs also for demanding scientific imaging applications, in particular in the astronomy community. CMOS detectors offer a series of inherent advantages compared to CCDs, due to the structure of their basic pixel cells, which each contain their own amplifier and readout electronics. The most prominent advantages for space object observations are the extremely fast and flexible readout capabilities, feasibility for electronic shuttering and precise epoch registration, and the potential to perform image processing operations on-chip and in real-time. Presently applied and proposed optical observation strategies for space debris surveys and space surveillance applications had to be analyzed. The major design drivers were identified and potential benefits from using available and future CMOS sensors were assessed. The major challenges and design drivers for ground-based and space-based optical observation strategies have been analyzed. CMOS detector characteristics were critically evaluated and compared with the established CCD technology, especially with respect to the above mentioned observations. Similarly, the desirable on-chip processing functionalities which would further enhance the object detection and image segmentation were identified. Finally, the characteristics of a particular CMOS sensor available at the Zimmerwald observatory were analyzed by performing laboratory test measurements.

  14. Candidate space processing techniques for biomaterials other than preparative electrophoresis

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.

    1976-01-01

    The advantages of performing the partition and countercurrent distribution (CCD) of cells in phase separated aqueous polymer systems under reduced gravity were assessed. Other possible applications considered for the space processing program include the freezing front separation of cells, adsorption of cells at the air-water interface, and the macrophage electrophoretic mobility test for cancer.

  15. GSFC Space Simulation Laboratory Contamination Philosophy: Efficient Space Simulation Chamber Cleaning Techniques

    NASA Technical Reports Server (NTRS)

    Roman, Juan A.; Stitt, George F.; Roman, Felix R.

    1997-01-01

    This paper will provide a general overview of the molecular contamination philosophy of the Space Simulation Test Engineering Section and how the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) space simulation laboratory controls and maintains the cleanliness of all its facilities, thereby, minimizing down time between tests. It will also briefly cover the proper selection and safety precautions needed when using some chemical solvents for wiping, washing, or spraying thermal shrouds when molecular contaminants increase to unacceptable background levels.

  16. Sublime science: Teaching for scientific sublime experiences in middle school classrooms

    NASA Astrophysics Data System (ADS)

    Cavanaugh, Shane

    Due to a historical separation of cognition and emotion, the affective aspects of learning are often seen as trivial in comparison to the more 'essential' cognitive qualities - particularly in the domain of science. As a result of this disconnect, feelings of awe, wonder, and astonishment as well as appreciation have been largely ignored in the working lives of scientists. In turn, I believe that science education has not accurately portrayed the world of science to our students. In an effort to bring the affective qualities of science into the science classroom, I have drawn on past research in the field of aesthetic science teaching and learning as well as works by, Burke, Kant, and Dewey to explore a new construct I have called the "scientific sublime". Scientific sublime experiences represent a sophisticated treatment of the cognitive as well as affective qualities of science learning. The scientific sublime represents feelings of awe, wonder, and appreciation that come from a deep understanding. It is only through this understanding of a phenomenon that we can appreciate its true complexity and intricacies, and these understandings when mixed with the emotions of awe and reverence, are sublime. Scientific sublime experiences are an attempt at the re-integration of cognition and feeling. The goal of this research was twofold: to create and teach a curriculum that fosters scientific sublime experiences in middle school science classes, and to better understand how these experiences are manifested in students. In order to create an approach to teaching for scientific sublime experiences, it was first necessary for me to identify key characteristics of such an experience and a then to create a pedagogical approach, both of which are described in detail in the dissertation. This research was conducted as two studies in two different middle schools. My pedagogical approach was used to create and teach two five-week 7 th grade science units---one on weather

  17. Practical sublimation source for large-scale chromium gettering in fusion devices

    SciTech Connect

    Simpkins, J.E.; Emerson, L.C.; Mioduszewski, P.K.

    1983-01-01

    This paper describes the technique of chromium gettering with a large-scale sublimation source which resembles in its design the VARIAN Ti-Ball. It consists of a hollow chromium sphere with a diameter of approximately 3 cm and an incandescent filament for radiation heating from inside the ball. While the fabrication of the source is described in a companion paper, we discuss here the gettering technique. The experimental arrangement consists of an UHV system instrumented for total- and partial-pressure measurements, a film-thickness monitor, thermocouples, an optical pyrometer, and appropriate instrumentation to measure the heating power. The results show the temperature and corresponding sublimation rate of the Cr-Ball as function of input power. In addition, an example of the total pumping speed of a gettered surface is shown.

  18. Three-dimensional textures and defects of soft material layering revealed by thermal sublimation

    PubMed Central

    Yoon, Dong Ki; Kim, Yun Ho; Kim, Dae Seok; Oh, Seong Dae; Smalyukh, Ivan I.; Clark, Noel A.; Jung, Hee-Tae

    2013-01-01

    Layering is found and exploited in a variety of soft material systems, ranging from complex macromolecular self-assemblies to block copolymer and small-molecule liquid crystals. Because the control of layer structure is required for applications and characterization, and because defects reveal key features of the symmetries of layered phases, a variety of techniques have been developed for the study of soft-layer structure and defects, including X-ray diffraction and visualization using optical transmission and fluorescence confocal polarizing microscopy, atomic force microscopy, and SEM and transmission electron microscopy, including freeze-fracture transmission electron microscopy. Here, it is shown that thermal sublimation can be usefully combined with such techniques to enable visualization of the 3D structure of soft materials. Sequential sublimation removes material in a stepwise fashion, leaving a remnant layer structure largely unchanged and viewable using SEM, as demonstrated here using a lamellar smectic liquid crystal. PMID:24218602

  19. A Space/Fast-Time Adaptive Monopulse Technique

    NASA Astrophysics Data System (ADS)

    Seliktar, Yaron; Williams, Douglas B.; Holder, E. Jeff

    2006-12-01

    Mainbeam jamming poses a particularly difficult challenge for conventional monopulse radars. In such cases spatially adaptive processing provides some interference suppression when the target and jammer are not exactly coaligned. However, as the target angle approaches that of the jammer, mitigation performance is increasingly hampered and distortions are introduced into the resulting beam pattern. Both of these factors limit the reliability of a spatially adaptive monopulse processor. The presence of coherent multipath in the form of terrain-scattered interference (TSI), although normally considered a nuisance, can be exploited to suppress mainbeam jamming with space/fast-time processing. A method is presented offering space/fast-time monopulse processing with distortionless spatial array patterns that can achieve improved angle estimation over spatially adaptive monopulse. Performance results for the monopulse processor are obtained for mountaintop data containing a jammer and TSI, which demonstrate a dramatic improvement in performance over conventional monopulse and spatially adaptive monopulse.

  20. Development of Backscatter X-Ray Imaging Techniques for Space Vehicle Applications

    NASA Technical Reports Server (NTRS)

    Bartha, Bence B.; Hope, Dale; Vona, Paul; Born, Martin; Corak, Tony

    2009-01-01

    This slide presentation reviews the development of backscatter x ray (BSX) imaging techniques to perform inspection of spacecraft components. The techniques are currently being enhanced to advance Non-Destructive Testing (NDT) methods for future space vehicle applications. The presentation includes an overview of x ray techniques, a description of current BSX applications used on the space shuttle, the development for Constellation applications, and the use of the system for foam applications.

  1. Simulation of wind-induced snow transport and sublimation in alpine terrain using a fully coupled snowpack/atmosphere model

    NASA Astrophysics Data System (ADS)

    Vionnet, V.; Martin, E.; Masson, V.; Guyomarc'h, G.; Naaim-Bouvet, F.; Prokop, A.; Durand, Y.; Lac, C.

    2014-03-01

    In alpine regions, wind-induced snow transport strongly influences the spatio-temporal evolution of the snow cover throughout the winter season. To gain understanding on the complex processes that drive the redistribution of snow, a new numerical model is developed. It directly couples the detailed snowpack model Crocus with the atmospheric model Meso-NH. Meso-NH/Crocus simulates snow transport in saltation and in turbulent suspension and includes the sublimation of suspended snow particles. The coupled model is evaluated against data collected around the experimental site of Col du Lac Blanc (2720 m a.s.l., French Alps). First, 1-D simulations show that a detailed representation of the first metres of the atmosphere is required to reproduce strong gradients of blowing snow concentration and compute mass exchange between the snowpack and the atmosphere. Secondly, 3-D simulations of a blowing snow event without concurrent snowfall have been carried out. Results show that the model captures the main structures of atmospheric flow in alpine terrain. However, at 50 m grid spacing, the model reproduces only the patterns of snow erosion and deposition at the ridge scale and misses smaller scale patterns observed by terrestrial laser scanning. When activated, the sublimation of suspended snow particles causes a reduction of deposited snow mass of 5.3% over the calculation domain. Total sublimation (surface + blowing snow) is three times higher than surface sublimation in a simulation neglecting blowing snow sublimation.

  2. Transactional Space: Feedback, Critical Thinking, and Learning Dance Technique

    ERIC Educational Resources Information Center

    Akinleye, Adesola; Payne, Rose

    2016-01-01

    This article explores attitudes about feedback and critical thinking in dance technique classes. The authors discuss an expansion of their teaching practices to include feedback as bidirectional (transactional) and a part of developing critical thinking skills in student dancers. The article was written after the authors undertook research…

  3. Technique to Predict Ultraviolet Radiation Embrittlement of Polymers in Space

    NASA Technical Reports Server (NTRS)

    1996-01-01

    In the low-Earth-orbit environment, solar ultraviolet (UV) radiation embrittles polymer materials through bond breaking and crosslinking. This UV embrittlement increases the surface hardness of the polymer. Before the durability of polymer materials in the low- Earth-orbit environment can be predicted, the extent of UV embrittlement needs to be determined. However, traditional techniques for measuring the microhardness of materials cannot be employed to measure changes in the hardness of UV-embrittled surfaces because traditional techniques measure bulk hardness and are not sensitive enough to surface changes. A unique technique was used at the NASA Lewis Research Center to quantify polymer surface damage that had been induced by UV radiation. The technique uses an atomic force microscope (AFM) to measure surface microhardness. An atomic force microscope measures the repulsive forces between the atoms in a microscopic cantilevered tip and the atoms on the surface of a sample. Typically, an atomic force microscope produces a topographic image of a surface by monitoring the movement of the tip over features of the surface. The force applied to the cantilevered tip, and the indention of the tip into the surface, can be measured. The relationship between force and distance of indentation, the quantity force/distance (newtons/meter), provides a measure of the surface hardness. Under identical operating conditions, direct comparisons of surface hardness values can be made.

  4. Transactional Space: Feedback, Critical Thinking, and Learning Dance Technique

    ERIC Educational Resources Information Center

    Akinleye, Adesola; Payne, Rose

    2016-01-01

    This article explores attitudes about feedback and critical thinking in dance technique classes. The authors discuss an expansion of their teaching practices to include feedback as bidirectional (transactional) and a part of developing critical thinking skills in student dancers. The article was written after the authors undertook research…

  5. Automatic State Space Aggregation Using a Density Based Technique

    DTIC Science & Technology

    2012-05-01

    applying reinforcement learning techniques in continuous environments is challenging because there are infinitely many states to visit in order to...that the abstractions produced by this method on two benchmark reinforcement learning problems can outperform fixed tiling methods in terms of both

  6. High-energy particles in space - Experimental methods and techniques

    NASA Astrophysics Data System (ADS)

    Shafer, Iu. G.

    Topics discussed include the space-time variations of cosmic radiation at the geostationary orbit, the nuclear component of solar cosmic rays, excess radiation at high altitudes above the earth, and electron flux with energies exceeding 150 MeV. Consideration is also given to the scattering of charged particles, a detector for measuring soft background X-rays, and the calculation of a detector's electrostatic field by the separation of variables. Methods are discussed for determining gamma-quantum and cosmic ray electron spectra, and for estimating the upper energy bounds of particles accelerated in the vicinity of a rotating neutron star.

  7. Space shuttle propulsion parameter estimation using optional estimation techniques

    NASA Technical Reports Server (NTRS)

    1983-01-01

    A regression analyses on tabular aerodynamic data provided. A representative aerodynamic model for coefficient estimation. It also reduced the storage requirements for the "normal' model used to check out the estimation algorithms. The results of the regression analyses are presented. The computer routines for the filter portion of the estimation algorithm and the :"bringing-up' of the SRB predictive program on the computer was developed. For the filter program, approximately 54 routines were developed. The routines were highly subsegmented to facilitate overlaying program segments within the partitioned storage space on the computer.

  8. Analysis of space tug operating techniques. Volume 2: Study results

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The design requirements for space tug systems and cost analysis of the refurbishment phases are discussed. The vehicle is an integral propulsion stage using liquid hydrogen and liquid oxygen as propellants and is capable of operating either as a fully or a partially autonomous vehicle. Structural features are an integral liquid hydrogen tank, a liquid oxygen tank, a meteoroid shield, an aft conical docking and structural support ring, and a staged combustion main engine. The vehicle is constructed of major modules for ease of maintenance. Line drawings and block diagrams are included to explain the maintenance requirements for the subsystems.

  9. Space shuttle transportation system techniques for user/use development

    NASA Technical Reports Server (NTRS)

    Gripshover, P. J.

    1974-01-01

    The problem of obtaining new uses for the Shuttle Transportation System (STS) was treated in the same way marketing problems are handled by industrial organizations. Techniques used by industry to obtain new ideas and customers were evaluated and analyzed for their relevance to the STS. Marketing barrier-data were used to develop strategy which called for a middleman organization to assist NASA in achieving its objectives. The importance of prompt initiation of the recommended strategy was established.

  10. The interaction of Io's plumes and sublimation atmosphere

    NASA Astrophysics Data System (ADS)

    McDoniel, William J.; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.

    2017-09-01

    Io's volcanic plumes are the ultimate source of its SO2 atmosphere, but past eruptions have covered the moon in surface frost which sublimates in sunlight. Today, Io's atmosphere is a result of some combination of volcanism and sublimation, but it is unknown exactly how these processes work together to create the observed atmosphere. We use the direct simulation Monte Carlo (DSMC) method to model the interaction of giant plumes with a sublimation atmosphere. Axisymmetric plume/atmosphere simulations demonstrate that the total mass of SO2 above Io's surface is only poorly approximated as the sum of independent volcanic and sublimated components. A simple analytic model is developed to show how variation in the mass of erupting gas above Io's surface can counteract variation in the mass of its hydrostatic atmosphere as surface temperature changes over a Jupiter year. Three-dimensional, unsteady simulations of giant plumes over an Io day are also presented, showing how plume material becomes suspended in the sublimation atmosphere. We find that a plume which produces some total mass above Io's surface at night will cause a net increase in the noon-time atmosphere of only a fraction of the night-time value. However, as much as seven times the night-side mass of the plume will become suspended in the sublimation atmosphere, altering its composition and displacing sublimated material.

  11. The sublime bridge: anatomy and implications in median nerve entrapment.

    PubMed

    Tubbs, R Shane; Marshall, Tyler; Loukas, Marios; Shoja, Mohammadali M; Cohen-Gadol, Aaron A

    2010-07-01

    The sublime bridge is a potential site of entrapment of the median nerve in the forearm. To the authors' knowledge, this structure and its relationship to the median nerve have not been studied. The aim of the present study was to quantitate this structure and elucidate its relationship to the median nerve. Sixty adult cadaveric forearms underwent dissection of the sublime bridge. Relationships of this structure were observed, and measurements of its anatomy were made. The relationship of the median nerve to the sublime bridge was observed with range of motion about the forearm. The sublime bridge was found to be tendinous in the majority (45 [75%]) of specimens and muscular in the remaining forearms (15 [25%]). The maximal mean width of the sublime bridge was 7 cm proximally, and the minimal mean width was 3 cm distally. The mean distance from the medial epicondyle to the apex of the sublime bridge was found to be 8.1 cm. The relation of the median nerve to the bridge was always intimate. On 2 sides (1 left and 1 right) from different male specimens, the median nerve was attached to the deep aspect of the sublime bridge by a strong connective tissue band, thus forming a tunnel on the deep aspect of this structure. With range of motion of the forearm, increased compression of the median nerve by the overlying sublime bridge was seen with extension but no other movement. Based on the authors' study, pronator syndrome is an incorrect term applied to compression of the median nerve at the sublime bridge. This potential site of median nerve compression is distinct and has characteristics that can clinically differentiate it from compression of the median nerve between the heads of the pronator teres. The authors hope that these data will be of use to the surgeon in the evaluation and treatment of patients with proximal median nerve entrapment.

  12. Analytic and interferometric techniques for the Laser Interferometer Space Antenna

    NASA Astrophysics Data System (ADS)

    Pollack, Scott E.

    The Laser Interferometer Space Antenna (LISA) is being designed to detect and study in detail gravitational waves from sources throughout the Universe such as massive black holes. The conceptual formulation of the LISA space-borne gravitational wave detector is now well developed. The interferometric measurements between the sciencecraft remain one of the most important technological and scientific design areas for the mission. Our work has concentrated on developing the interferometric technologies to create a LISA-like optical signal and to measure the phase of that signal using commercially available instruments. One of the most important goals of this research is to demonstrate the LISA phase timing and phase reconstruction for a LISA-like fringe signal, in the case of a high fringe rate and a low signal level. To this end we have constructed a table-top interferometer which produces LISA-like fringe signals. Over the past few years questions have been raised concerning the use of laser communications links between sciencecraft to transmit phase information crucial to the reduction of laser frequency noise in the LISA science measurement. The concern is that applying medium frequency phase modulations to the laser carrier could compromise the phase stability of the LISA fringe signal. We have modified our table-top interferometer by applying a phase modulation to the laser beam in order to evaluate the effects of such modulations on the LISA science fringe signal. We have demonstrated that the phase resolution of the science signal is not degraded by the presence of medium frequency phase modulations. Each spacecraft in LISA houses a proof mass which follows a geodesic through space. Disturbances that change the proof mass position, momentum, and acceleration will appear in the LISA data stream as additive quadratic functions. These data disturbances inhibit signal extraction and must be removed. Much of our analytical work has been focused on discussing the

  13. A Free-Space Measurement Technique of Terahertz Dielectric Properties

    NASA Astrophysics Data System (ADS)

    Zhang, Xiansheng; Chang, Tianying; Cui, Hong-Liang; Sun, Zhonglin; Yang, Chuanfa; Yang, Xiuwei; Liu, Lingyu; Fan, Wei

    2016-11-01

    The free-space method for material dielectric characterization in the microwave band is extended to terahertz frequencies. By analyzing the advantages and disadvantages of the relative permittivity of the transmission/reflection method for non-magnetic materials, a fast calculation method using a transmission-only method is proposed. Based on the convergence analysis of the algorithm, a method to estimate the initial value is also proposed. Finally, through measurements of the permittivity of high-density polyethylene, polystyrene, polypropylene, and polymethyl methacrylate in the 325-500 GHz band, we verify the rationality of the algorithm and demonstrate its applicability. Through the combination of the two methods, the terahertz dielectric properties of a majority of flat non-conducting solid materials and non-polar liquid materials can be measured.

  14. Error control techniques for satellite and space communications

    NASA Technical Reports Server (NTRS)

    Costello, Daniel J., Jr.

    1992-01-01

    Worked performed during the reporting period is summarized. Construction of robustly good trellis codes for use with sequential decoding was developed. The robustly good trellis codes provide a much better trade off between free distance and distance profile. The unequal error protection capabilities of convolutional codes was studied. The problem of finding good large constraint length, low rate convolutional codes for deep space applications is investigated. A formula for computing the free distance of 1/n convolutional codes was discovered. Double memory (DM) codes, codes with two memory units per unit bit position, were studied; a search for optimal DM codes is being conducted. An algorithm for constructing convolutional codes from a given quasi-cyclic code was developed. Papers based on the above work are included in the appendix.

  15. A Free-Space Measurement Technique of Terahertz Dielectric Properties

    NASA Astrophysics Data System (ADS)

    Zhang, Xiansheng; Chang, Tianying; Cui, Hong-Liang; Sun, Zhonglin; Yang, Chuanfa; Yang, Xiuwei; Liu, Lingyu; Fan, Wei

    2017-03-01

    The free-space method for material dielectric characterization in the microwave band is extended to terahertz frequencies. By analyzing the advantages and disadvantages of the relative permittivity of the transmission/reflection method for non-magnetic materials, a fast calculation method using a transmission-only method is proposed. Based on the convergence analysis of the algorithm, a method to estimate the initial value is also proposed. Finally, through measurements of the permittivity of high-density polyethylene, polystyrene, polypropylene, and polymethyl methacrylate in the 325-500 GHz band, we verify the rationality of the algorithm and demonstrate its applicability. Through the combination of the two methods, the terahertz dielectric properties of a majority of flat non-conducting solid materials and non-polar liquid materials can be measured.

  16. A study of trends and techniques for space base electronics

    NASA Technical Reports Server (NTRS)

    Trotter, J. D.; Wade, T. E.; Gassaway, J. D.; Mahmood, Q.

    1978-01-01

    A sputtering system was developed to deposit aluminum and aluminum alloys by the dc sputtering technique. This system is designed for a high level of cleanliness and for monitoring the deposition parameters during film preparation. This system is now ready for studying the deposition and annealing parameters upon double-level metal preparation. A technique recently applied for semiconductor analysis, the finite element method, was studied for use in the computer modeling of two dimensional MOS transistor structures. It was concluded that the method has not been sufficiently well developed for confident use at this time. An algorithm was developed for confident use at this time. An algorithm was developed for implementing a computer study which is based upon the finite difference method. The program which was developed was modified and used to calculate redistribution data for boron and phosphorous which had been predeposited by ion implantation with range and straggle conditions. Data were generated for 111 oriented SOS films with redistribution in N2, dry O2 and steam ambients.

  17. New results and techniques in space radio astronomy.

    NASA Technical Reports Server (NTRS)

    Alexander, J. K.

    1971-01-01

    The methods and results of early space radioastronomy experiments are reviewed, with emphasis on the RAE 1 spacecraft which was designed specifically and exclusively for radio astronomical studies. The RAE 1 carries two gravity-gradient-stabilized 229-m traveling-wave V-antennas, a 37-m dipole antenna, and a number of radiometer systems to provide measurements over the 0.2 to 9.2 MHz frequency range with a time resolution of 0.5 sec and an absolute accuracy of plus or minus 25%. Observations of solar bursts at frequencies down to 0.2 MHz provide new information on the density, plasma velocity, and dynamics of coronal streamers out to distances greater than 50 solar radii. New information on the distribution of the ionized component of the interstellar medium is being obtained from galactic continuum background maps at frequencies around 4 MHz. Cosmic noise background spectra measured down to 0.5 MHz produce new estimates on the interstellar flux of cosmic rays, on magnetic fields in the galactic halo, and on distant extragalactic radio sources.

  18. Error control techniques for satellite and space communications

    NASA Technical Reports Server (NTRS)

    Costello, D. J., Jr.

    1986-01-01

    High rate concatenated coding systems with trellis inner codes and Reed-Solomon (RS) outer codes for application in satellite communication systems are considered. Two types of inner codes are studied: high rate punctured binary convolutional codes which result in overall effective information rates between 1/2 and 1 bit per channel use; and bandwidth efficient signal space trellis codes which can achieve overall effective information rates greater than 1 bit per channel use. Channel capacity calculations with and without side information performed for the concatenated coding system. Concatenated coding schemes are investigated. In Scheme 1, the inner code is decoded with the Viterbi algorithm and the outer RS code performs error-correction only (decoding without side information). In scheme 2, the inner code is decoded with a modified Viterbi algorithm which produces reliability information along with the decoded output. In this algorithm, path metrics are used to estimate the entire information sequence, while branch metrics are used to provide the reliability information on the decoded sequence. This information is used to erase unreliable bits in the decoded output. An errors-and-erasures RS decoder is then used for the outer code. These two schemes are proposed for use on NASA satellite channels. Results indicate that high system reliability can be achieved with little or no bandwidth expansion.

  19. Cryogenic techniques for large superconducting magnets in space

    SciTech Connect

    Green, M.A.

    1988-12-01

    A large superconducting magnet is proposed for use in a particle astrophysics experiment, ASTROMAG, which is to be mounted on the United States Space Station. This experiment will have a two-coil superconducting magnet with coils which are 1.3 to 1.7 meters in diameter. The two-coil magnet will have zero net magnetic dipole moment. The field 15 meters from the magnet will approach earth's field in low earth orbit. The issue of high Tc superconductor will be discussed in the paper. The reasons for using conventional niobium-titanium superconductor cooled with superfluid helium will be presented. Since the purpose of the magnet is to do particle astrophysics, the superconducting coils must be located close to the charged particle detectors. The trade off between the particle physics possible and the cryogenic insulation around the coils is discussed. As a result, the ASTROMAG magnet coils will be operated outside of the superfluid helium storage tank. The fountain effect pumping system which will be used to cool the coil is described in the report. Two methods for extending the operating life of the superfluid helium dewar are discussed. These include: operation with a third shield cooled to 90 K with a sterling cycle cryocooler, and a hybrid cryogenic system where there are three hydrogen-cooled shields and cryostat support heat intercept points. Both of these methods will extend the ASTROMAG cryogenic operating life from 2 years to almost 4 years. 14 refs., 8 figs., 4 tabs.

  20. Space simulation techniques and facilities for SAX STM test campaign

    NASA Astrophysics Data System (ADS)

    Giordano, Pietro; Raimondo, Giacomo; Messidoro, Piero

    1994-11-01

    SAX is a satellite for X-Ray astronomy. It is a major element of the overall basic Science Program of the Italian Space Agency (ASI) and is being developed with the contribution of the Netherlands Agency for Aerospace Programs (NIVR). The scientific objectives of SAX are to carry out systematic and comprehensive observations of celestial X-Ray sources over the 0.1 - 300 KeV energy range with special emphasis on spectral and timing measurements. The satellite will also monitor the X-Ray sky to investigate long-term source variability and to permit localization and study of X-Ray transients. Alenia Spazio is developing the satellite that is intended for launch in the second half of 1995 in a low, near-equatorial Earth orbit. At system level a Structural Thermal Model (STM) has been conceived to verify the environmental requirements by validating the mechanical and thermal analytical models and qualifying satellite structure and thermal control. In particular, the following tests have been carried out in Alenia Spazio, CEA/CESTA and ESTEC facilities: Modal Survey, Centrifuge, Acoustic, Sinusoidal/Random Vibration and Thermal Balance. The paper, after a short introduction of the SAX satellite, summarizes the environmental qualification program performed on the SAX STM. It presents test objectives, methodologies and relevant test configurations. Peculiar aspects of the test campaign are highlighted. Problems encountered and solutions adopted in performing the tests are described as well. Furthermore, test results are presented and assessed.

  1. Action Research to Improve the Learning Space for Diagnostic Techniques.

    PubMed

    Ariel, Ellen; Owens, Leigh

    2015-12-01

    The module described and evaluated here was created in response to perceived learning difficulties in diagnostic test design and interpretation for students in third-year Clinical Microbiology. Previously, the activities in lectures and laboratory classes in the module fell into the lower cognitive operations of "knowledge" and "understanding." The new approach was to exchange part of the traditional activities with elements of interactive learning, where students had the opportunity to engage in deep learning using a variety of learning styles. The effectiveness of the new curriculum was assessed by means of on-course student assessment throughout the module, a final exam, an anonymous questionnaire on student evaluation of the different activities and a focus group of volunteers. Although the new curriculum enabled a major part of the student cohort to achieve higher pass grades (p < 0.001), it did not meet the requirements of the weaker students, and the proportion of the students failing the module remained at 34%. The action research applied here provided a number of valuable suggestions from students on how to improve future curricula from their perspective. Most importantly, an interactive online program that facilitated flexibility in the learning space for the different reagents and their interaction in diagnostic tests was proposed. The methods applied to improve and assess a curriculum refresh by involving students as partners in the process, as well as the outcomes, are discussed. Journal of Microbiology & Biology Education.

  2. Space simulation techniques and facilities for SAX STM test campaign

    NASA Technical Reports Server (NTRS)

    Giordano, Pietro; Raimondo, Giacomo; Messidoro, Piero

    1994-01-01

    SAX is a satellite for X-Ray astronomy. It is a major element of the overall basic Science Program of the Italian Space Agency (ASI) and is being developed with the contribution of the Netherlands Agency for Aerospace Programs (NIVR). The scientific objectives of SAX are to carry out systematic and comprehensive observations of celestial X-Ray sources over the 0.1 - 300 KeV energy range with special emphasis on spectral and timing measurements. The satellite will also monitor the X-Ray sky to investigate long-term source variability and to permit localization and study of X-Ray transients. Alenia Spazio is developing the satellite that is intended for launch in the second half of 1995 in a low, near-equatorial Earth orbit. At system level a Structural Thermal Model (STM) has been conceived to verify the environmental requirements by validating the mechanical and thermal analytical models and qualifying satellite structure and thermal control. In particular, the following tests have been carried out in Alenia Spazio, CEA/CESTA and ESTEC facilities: Modal Survey, Centrifuge, Acoustic, Sinusoidal/Random Vibration and Thermal Balance. The paper, after a short introduction of the SAX satellite, summarizes the environmental qualification program performed on the SAX STM. It presents test objectives, methodologies and relevant test configurations. Peculiar aspects of the test campaign are highlighted. Problems encountered and solutions adopted in performing the tests are described as well. Furthermore, test results are presented and assessed.

  3. Interferometric Techniques for Gravitational Wave Detection in Space

    NASA Technical Reports Server (NTRS)

    Stebbins, Robin T; Bender, Peter L.

    2000-01-01

    The Laser Interferometer Space Antenna (LISA) mission will detect gravitational waves from galactic and extragalactic sources, most importantly those involving supermassive black holes. The primary goal of this project is to investigate stability and robustness issues associated with LISA interferometry. We specifically propose to study systematic errors arising from: optical misalignments, optical surface errors, thermal effects and pointing tolerances. This report covers the first fiscal year of the grant, from January 1st to December 31st 1999. We have employed an optical modeling tool to evaluate the effect of misplaced and misaligned optical components. Preliminary results seem to indicate that positional tolerances of one micron and angular tolerances of 0.6 millirad produce no significant effect on the achievable contrast of the interference pattern. This report also outlines research plans for the second fiscal year of the grant, from January 1st to December 31st 2000. Since the work under NAG5-6880 has gone more rapidly than projected, our test bed interferometer is operational, and can be used for measurements of effects that cause beam motion. Hence, we will design, build and characterize a sensor for measuring beam motion, and then install it. We are also planning a differential wavefront sensor based on a quadrant photodiode as a first generation sensor.

  4. A study of the maximum entropy technique for phase space tomography

    NASA Astrophysics Data System (ADS)

    Hock, K. M.; Ibison, M. G.

    2013-02-01

    We study a problem with the Maximum Entropy Technique (MENT) when applied to tomographic measurements of the transverse phase space of electron beams, and suggest some ways to improve its reliability. We show that the outcome of a phase space reconstruction can be highly sensitive to the choice of projection angles. It is quite likely to obtain reconstructed distributions of the phase space that are obviously different from the actual distributions. We propose a method to obtain a ``good'' choice of projections angles using a normalised phase space. We demonstrate that the resulting reconstructions of the phase space can be significantly improved.

  5. Autonomous space object tracking and azimuth determination using star tracker technique under complex space environment

    NASA Astrophysics Data System (ADS)

    Ye, Tao; Zhou, Fuqiang

    2015-07-01

    Autonomous space object tracking under complex space environment is a popular topic in space engineering research. However, it is a challenging task for measurement equipment, implementing navigation under complex environment, and tracking object with unknown trajectory. An algorithm for space object tracking and azimuth determination using star tracker technology is the first time proposed in this paper. It includes two major steps, star tracking and object tracking. In star tracking stage, a motion-vector algorithm is the first time exploring to track stars in sequence images, which can track stars under complex space environment. With the tracked stars, the star tracker's attitude can be updated in real-time. In object tracking stage, with the obtained attitude of the star tracker, the Kalman filter (KF) model is built to predict the object state. It takes the measured azimuth as observations rather than the object coordinates in CCD plane, which can avoid the computational complexity due to matrix derivations compared to traditional Extend-Kalman filter, and its convergence rate of the filter is improved consequently. The azimuth and the velocity of the object can be updated by the KF prediction process. In addition, different levels of background noise were added to simulate the complex space environment, and an artificial object is also added in frame with non-linear trajectory in CCD plane. The feasibility of the proposed methods is validated using synthesized sequence images which contain object motions. The simulated results show that the algorithm proposed can track stars and object successfully.

  6. Nietzsche's View of Sublimation in the Educational Process

    ERIC Educational Resources Information Center

    Sharp, Ann Margaret

    1975-01-01

    Article outlined Nietzsche's beliefs on the primary aim of education, the conscious production of the free man through the process of sublimation, the active redirecting of one's life energy in the service of creativity. (Editor/RK)

  7. Scanning electron microscope observations of sublimates from Merapi Volcano, Indonesia

    USGS Publications Warehouse

    Symonds, R.

    1993-01-01

    Sublimates were sampled from high-temperature (up to 800??C) fumaroles at Merapi volcano in January 1984. Sampling is accomplished by inserting silica tubes into high-temperature vents. Volcanic glass flows through the tubes and sublimates precipitate on the inner walls in response to the temperature gradient. With decreasing temperature (800-500??C) in the tubes, there are five sublimate zones. Texturally, the sublimate phases grade from large, well-formed crystals at their highest-temperature occurrence to more numerous, smaller crystals that are less perfect at lower temperatures. These changes imply that the crystal nucleation and growth rates increase and decrease, respectively, as temperature decreases. Overall, the textural data suggest that the gas is saturated or slightly super-saturated with the phases at their hottest occurrence, but that the gas becomes increasingly super-saturated with the phases at lower temperatures. -from Author

  8. Dynamics and Mechanisms of Exfoliated Black Phosphorus Sublimation.

    PubMed

    Fortin-Deschênes, Matthieu; Levesque, Pierre L; Martel, Richard; Moutanabbir, Oussama

    2016-05-05

    We report on real time observations of the sublimation of exfoliated black phosphorus layers throughout annealing using in situ low energy electron microscopy. We found that sublimation manifests itself above 375 ± 20 °C through the nucleation and expansion of asymmetric, faceted holes with the long axis aligned along the [100] direction and sharp tips defined by edges consisting of alternating (10) and (11) steps. This thermally activated process repeats itself via successive sublimation of individual layers. Calculations and simulations using density functional theory and kinetic Monte Carlo allowed to determine the involved atomic pathways. Sublimation is found to occur via detachments of phosphorus dimers rather than single atoms. This behavior and the role of defects is described using an analytical model that captures all essential features. This work establishes an atomistic-level understanding of the thermal stability of exfoliated black phosphorus and defines the temperature window available for material and device processing.

  9. Sublimation as a Landform-Shaping Process on Pluto

    NASA Technical Reports Server (NTRS)

    Moore, J. M.; Howard, A. D.; White, O. L.; Umurhan, O. M.; Schenk, P. M.; Beyer, R. A.; McKinnon, W. B.; Singer, K. N.; Spencer, J. R.; Stern, S. A.; hide

    2016-01-01

    Several icy-world surfaces in the solar system exhibit sublimation-driven landform modification erosion, condensation, and mass wasting [1]. In addition to the obvious role of gravity, mass wasting can work in conjunction with internal disaggregation of a landform's relief-supporting material through the loss (or deteriorating alteration) of its cohesive matrix. To give a conspicuous example, Callisto's landscape exhibits widespread erosion from sublimation erosion of slopes, which results in smooth, undulating, low albedo plains composed of lag deposits, with isolated high albedo pinnacles perched on remnants of crater rims due to the re-precipitation of ice on local cold traps [2, 3, 4]. Sublimation-driven mass wasting was anticipated on Pluto prior to the encounter (see refs in [5]). Here we report on several landscapes on Pluto we interpret to be formed, or at least heavily modified, by sublimation erosion.

  10. Sulfur "Concrete" for Lunar Applications - Sublimation Concerns

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Toutanji, Houssam

    2006-01-01

    Melting sulfur and mixing it with an aggregate to form "concrete" is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO2 powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.

  11. Sulfur "Concrete" for Lunar Applications - Sublimation Concerns

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Toutanji, Houssam

    2006-01-01

    Melting sulfur and mixing it with an aggregate to form "concrete" is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO2 powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.

  12. Spacing Techniques in Second Language Vocabulary Acquisition: Short-Term Gains vs. Long-Term Memory

    ERIC Educational Resources Information Center

    Schuetze, Ulf

    2015-01-01

    This article reports the results of two experiments using the spacing technique (Leitner, 1972; Landauer & Bjork, 1978) in second language vocabulary acquisition. In the past, studies in this area have produced mixed results attempting to differentiate between massed, uniform and expanded intervals of spacing (Balota, Duchek, & Logan,…

  13. Spacing Techniques in Second Language Vocabulary Acquisition: Short-Term Gains vs. Long-Term Memory

    ERIC Educational Resources Information Center

    Schuetze, Ulf

    2015-01-01

    This article reports the results of two experiments using the spacing technique (Leitner, 1972; Landauer & Bjork, 1978) in second language vocabulary acquisition. In the past, studies in this area have produced mixed results attempting to differentiate between massed, uniform and expanded intervals of spacing (Balota, Duchek, & Logan,…

  14. Imaging the dust sublimation front of a circumbinary disk

    NASA Astrophysics Data System (ADS)

    Hillen, M.; Kluska, J.; Le Bouquin, J.-B.; Van Winckel, H.; Berger, J.-P.; Kamath, D.; Bujarrabal, V.

    2016-04-01

    Aims: We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust. Methods: A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed by combining the data of all spectral channels using the SPARCO method. Results: We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an unexpected flux signal of ~4% from the secondary star. The energy output from this companion indicates the presence of a compact circum-companion accretion disk, which is likely the origin of the fast outflow detected in Hα. Conclusions: Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program ID 094.D-0865.

  15. Phase transition and surface sublimation of a mobile Potts model.

    PubMed

    Bailly-Reyre, A; Diep, H T; Kaufman, M

    2015-10-01

    We study in this paper the phase transition in a mobile Potts model by the use of Monte Carlo simulation. The mobile Potts model is related to a diluted Potts model, which is also studied here by a mean-field approximation. We consider a lattice where each site is either vacant or occupied by a q-state Potts spin. The Potts spin can move from one site to a nearby vacant site. In order to study the surface sublimation, we consider a system of Potts spins contained in a recipient with a concentration c defined as the ratio of the number of Potts spins N(s) to the total number of lattice sites N(L)=N(x)×N(y)×N(z). Taking into account the attractive interaction between the nearest-neighboring Potts spins, we study the phase transitions as functions of various physical parameters such as the temperature, the shape of the recipient, and the spin concentration. We show that as the temperature increases, surface spins are detached from the solid phase to form a gas in the empty space. Surface order parameters indicate different behaviors depending on the distance to the surface. At high temperatures, if the concentration is high enough, the interior spins undergo a first-order phase transition to an orientationally disordered phase. The mean-field results are shown as functions of temperature, pressure, and chemical potential, which confirm in particular the first-order character of the transition.

  16. Are the Sublimation Thermodynamics of Organic Molecules Predictable?

    PubMed

    McDonagh, James L; Palmer, David S; Mourik, Tanja van; Mitchell, John B O

    2016-11-28

    We compare a range of computational methods for the prediction of sublimation thermodynamics (enthalpy, entropy, and free energy of sublimation). These include a model from theoretical chemistry that utilizes crystal lattice energy minimization (with the DMACRYS program) and quantitative structure property relationship (QSPR) models generated by both machine learning (random forest and support vector machines) and regression (partial least squares) methods. Using these methods we investigate the predictability of the enthalpy, entropy and free energy of sublimation, with consideration of whether such a method may be able to improve solubility prediction schemes. Previous work has suggested that the major source of error in solubility prediction schemes involving a thermodynamic cycle via the solid state is in the modeling of the free energy change away from the solid state. Yet contrary to this conclusion other work has found that the inclusion of terms such as the enthalpy of sublimation in QSPR methods does not improve the predictions of solubility. We suggest the use of theoretical chemistry terms, detailed explicitly in the Methods section, as descriptors for the prediction of the enthalpy and free energy of sublimation. A data set of 158 molecules with experimental sublimation thermodynamics values and some CSD refcodes has been collected from the literature and is provided with their original source references.

  17. Sublimation of cometary ices in the presence of organic volatiles

    NASA Astrophysics Data System (ADS)

    Kossacki, Konrad J.; Leliwa-Kopystynski, Jacek; Witek, Piotr; Jasiak, Aleksander; Dubiel, Adrian

    2017-09-01

    Evolution of the surfaces of cometary nuclei is determined by the sublimation of ice. The rate of sublimation is commonly calculated using the simple Hertz-Knudsen formula, which should be corrected by a temperature dependent sublimation coefficient αs (Kossacki et al., 1999; Gundlach et al., 2011; Kossacki and Leliwa-Kopystynski, 2014). In this work influence of C3H6O (acetone), and CH3OH (methanol) present in cometary ice on the sublimation coefficient is investigated. We have found, that the mass fraction of admixtures ≤ 2% in water ice is sufficient for an increase of αs by a factor about 5, depending on the temperature. The sublimation coefficient is sensitive to very small concentrations of admixtures. When the admixture is acetone and the mass fraction f = 0.005 is αs(215 K) ∼ 0.46 instead of ∼ 0.18 for pure water ice. When f = 0.01 is αs(215 K) ∼ 0.74, and when f = 0.02 is αs(215 K) ∼ 0.78. The presence of 0.01 mass fraction of methanol has similar influence on the sublimation coefficient as the presence of 0.01 mass fraction of acetone. At temperatures T > 235 K for all investigated compositions of ice αs ∼ 0.15.

  18. Sublimity and beauty: A view from nursing aesthetics.

    PubMed

    Siles-González, José; Solano-Ruiz, Carmen

    2016-03-01

    Several authors have focused on the aesthetics of nursing care from diverse perspectives; however, there are few studies about the sublime and the beautiful in nursing. To identify beautiful and sublime moments in the context of the aesthetics of nursing care. A theoretical reflection has been contemplated about sublime and beautiful values in the context of the aesthetics of nursing care from the cultural history perspective. For that purpose, a revision of this issue has been completed. The terms 'beautiful' and 'sublime' have been analysed to identify the characteristics of both in the context of nursing care. We have followed all ethical requirements regarding the sources, conducting research and authorship. There is no conflict of interest in this paper. With aesthetic knowledge, the nurse expresses the artistic nature of nursing care by appreciating the act of caring for individuals. The sublime is a complex phenomenon, since apparently contrary feelings are interwoven. Nursing care is an art with an anthropological object-subject on which the 'artist' applies their prior knowledge and skills. Feelings and emotions that develop during the clinical nursing practice - especially at times sublime and beautiful, aesthetic - constitute experiences which are professionally significant. © The Author(s) 2015.

  19. Microthermogravimetric analysis as a useful tool for in-situ planetary space missions

    NASA Astrophysics Data System (ADS)

    Palomba, E.; Zinzi, A.; Longobardo, A.; Bellucci, G.; Zampetti, E.; Pantalei, S.; Bearzotti, A.; Macagnano, A.

    2008-09-01

    Thermo gravimetric analysis (TGA) is a widely used technique to investigate condensation/sublimation and absorption/desorption processes of volatile compounds in different environments. TGA analyzers are used to investigate outgassing contamination in Space, dehydration and organic decomposition in minerals, as well as to measure moisture content in foods or develop temperature profiles for firing ceramics. TGA is often coupled with other analytical techniques (e.g., mass spectroscopy and FTIR) in order to determine the specific off-gas materials.

  20. Equivalence and Differences between Structural Equation Modeling and State-Space Modeling Techniques

    ERIC Educational Resources Information Center

    Chow, Sy-Miin; Ho, Moon-ho R.; Hamaker, Ellen L.; Dolan, Conor V.

    2010-01-01

    State-space modeling techniques have been compared to structural equation modeling (SEM) techniques in various contexts but their unique strengths have often been overshadowed by their similarities to SEM. In this article, we provide a comprehensive discussion of these 2 approaches' similarities and differences through analytic comparisons and…

  1. Equivalence and Differences between Structural Equation Modeling and State-Space Modeling Techniques

    ERIC Educational Resources Information Center

    Chow, Sy-Miin; Ho, Moon-ho R.; Hamaker, Ellen L.; Dolan, Conor V.

    2010-01-01

    State-space modeling techniques have been compared to structural equation modeling (SEM) techniques in various contexts but their unique strengths have often been overshadowed by their similarities to SEM. In this article, we provide a comprehensive discussion of these 2 approaches' similarities and differences through analytic comparisons and…

  2. Characterization of Sulfur and Nanostructured Sulfur Battery Cathodes in Electron Microscopy Without Sublimation Artifacts.

    PubMed

    Levin, Barnaby D A; Zachman, Michael J; Werner, Jörg G; Sahore, Ritu; Nguyen, Kayla X; Han, Yimo; Xie, Baoquan; Ma, Lin; Archer, Lynden A; Giannelis, Emmanuel P; Wiesner, Ulrich; Kourkoutis, Lena F; Muller, David A

    2017-02-01

    Lithium sulfur (Li-S) batteries have the potential to provide higher energy storage density at lower cost than conventional lithium ion batteries. A key challenge for Li-S batteries is the loss of sulfur to the electrolyte during cycling. This loss can be mitigated by sequestering the sulfur in nanostructured carbon-sulfur composites. The nanoscale characterization of the sulfur distribution within these complex nanostructured electrodes is normally performed by electron microscopy, but sulfur sublimates and redistributes in the high-vacuum conditions of conventional electron microscopes. The resulting sublimation artifacts render characterization of sulfur in conventional electron microscopes problematic and unreliable. Here, we demonstrate two techniques, cryogenic transmission electron microscopy (cryo-TEM) and scanning electron microscopy in air (airSEM), that enable the reliable characterization of sulfur across multiple length scales by suppressing sulfur sublimation. We use cryo-TEM and airSEM to examine carbon-sulfur composites synthesized for use as Li-S battery cathodes, noting several cases where the commonly employed sulfur melt infusion method is highly inefficient at infiltrating sulfur into porous carbon hosts.

  3. Deviations from Ideal Sublimation Vapor Pressure Behavior in Mixtures of Polycyclic Aromatic Compounds with Interacting Heteroatoms.

    PubMed

    Goldfarb, Jillian L; Suuberg, Eric M

    2010-08-01

    Despite the relatively small atomic fraction of a given heteroatom in a binary mixture of polycyclic aromatic compounds (PAC), the inclusion of heteroatomic substituted compounds can significantly impact mixture vapor pressure behavior over a wide range of temperatures. The vapor pressures of several binary PAC mixtures containing various heteroatoms show varying behavior, from practically ideal behavior following Raoult's law to significant deviations from ideality depending on the heteroatom(s) present in the mixture. Mixtures were synthesized using the quench-cool technique with equimolar amounts of two PAC, both containing heteroatoms such as aldehyde, carboxyl, nitrogen, and sulfur substituent groups. For some mixtures, deviation from ideality is inversely related to temperature, though in other cases we see deviations from ideality increasing with temperature, whereas some appear independent of temperature. Most commonly we see lower vapor pressures than predicted by Raoult's law, which indicates that the interacting heteroatoms prefer the solid mixture phase as opposed to the vapor phase. Although negative deviations predominate from Raoult's Law, the varying mixtures investigated show both higher and lower enthalpies and entropies of sublimation than predicted. In each mixture, a higher enthalpy of sublimation leads to higher entropy of sublimation than predicted, and vice versa.

  4. Spectroscopy of lithium atoms sublimated from isolation matrix of solid Ne

    NASA Astrophysics Data System (ADS)

    Sacramento, R. L.; Scudeller, L. A.; Lambo, R.; Crivelli, P.; Cesar, C. L.

    2011-10-01

    We have studied, via laser absorption spectroscopy, the velocity distribution of 7Li atoms released from a solid neon matrix at cryogenic temperatures. The Li atoms are implanted into the Ne matrix by laser ablation of a solid Li precursor. A heat pulse is then applied to the sapphire substrate sublimating the matrix together with the isolated atoms at around 12 K. We find interesting differences in the velocity distribution of the released Li atoms from the model developed for our previous experiment with Cr [R. Lambo, C. C. Rodegheri, D. M. Silveira, and C. L. Cesar, Phys. Rev. A 76, 061401-R (2007)], 10.1103/PhysRevA.76.061401. This may be due to the sublimation regime, which is at much lower flux for the Li experiment than for the Cr experiment, as well as to the different collisional cross sections between those species to the Ne gas. We find a drift velocity compatible with Li being thermally sublimated at 11-13 K, while the velocity dispersion around this drift velocity is low, around 5-7 K. With a slow sublimation of the matrix we can determine the penetration depth of the laser ablated Li atoms into the Ne matrix, an important information that is not usually available in most matrix isolation spectroscopy setups. The present results with Li, together with the previous results with Cr suggest this to be a general technique for obtaining cryogenic atoms, for spectroscopic studies, as well as for trap loading. The release of the isolated atoms is also a useful tool to study and confirm details of the matrix isolated atoms which are masked or poorly understood in the solid.

  5. Spectroscopy of lithium atoms sublimated from isolation matrix of solid Ne.

    PubMed

    Sacramento, R L; Scudeller, L A; Lambo, R; Crivelli, P; Cesar, C L

    2011-10-07

    We have studied, via laser absorption spectroscopy, the velocity distribution of (7)Li atoms released from a solid neon matrix at cryogenic temperatures. The Li atoms are implanted into the Ne matrix by laser ablation of a solid Li precursor. A heat pulse is then applied to the sapphire substrate sublimating the matrix together with the isolated atoms at around 12 K. We find interesting differences in the velocity distribution of the released Li atoms from the model developed for our previous experiment with Cr [R. Lambo, C. C. Rodegheri, D. M. Silveira, and C. L. Cesar, Phys. Rev. A 76, 061401(R) (2007)]. This may be due to the sublimation regime, which is at much lower flux for the Li experiment than for the Cr experiment, as well as to the different collisional cross sections between those species to the Ne gas. We find a drift velocity compatible with Li being thermally sublimated at 11-13 K, while the velocity dispersion around this drift velocity is low, around 5-7 K. With a slow sublimation of the matrix we can determine the penetration depth of the laser ablated Li atoms into the Ne matrix, an important information that is not usually available in most matrix isolation spectroscopy setups. The present results with Li, together with the previous results with Cr suggest this to be a general technique for obtaining cryogenic atoms, for spectroscopic studies, as well as for trap loading. The release of the isolated atoms is also a useful tool to study and confirm details of the matrix isolated atoms which are masked or poorly understood in the solid.

  6. Sublimation-Condensation of Multiscale Tellurium Structures

    SciTech Connect

    Riley, Brian J.; Johnson, Bradley R.; Schaef, Herbert T.; Sundaram, S. K.

    2013-03-11

    This paper presents a simple technique for making tellurium (Te) nano and microtubes of widely varying dimensions with Multi-Scale Processing (MSP). In this process, the Te metal is placed in a reaction vessel (e.g., borosilicate or fused quartz), the vessel is evacuated, and then sealed under vacuum with a torch. The vessel is heat-treated in a temperature gradient where a portion of the tube that can also contain an additional substrate, is under a decreasing temperature gradient. Scanning and transmission electron microscopies have shown that multifaceted crystalline tubes have been formed extending from nano- up to micron-scale with diameters ranging from 51.2 ± 5.9 to 1042 ± 134 nm between temperatures of 157 and 224 °C, respectively. One-dimensional tubular features are seen at lower temperatures, while three-dimensional features, at the higher temperatures. These features have been characterized with X-ray diffraction and found to be trigonal Te with space group P3121. Our results show that the MSP can adequately be described using a simple Arrhenius equation.

  7. Simulation verification techniques study: Simulation performance validation techniques document. [for the space shuttle system

    NASA Technical Reports Server (NTRS)

    Duncan, L. M.; Reddell, J. P.; Schoonmaker, P. B.

    1975-01-01

    Techniques and support software for the efficient performance of simulation validation are discussed. Overall validation software structure, the performance of validation at various levels of simulation integration, guidelines for check case formulation, methods for real time acquisition and formatting of data from an all up operational simulator, and methods and criteria for comparison and evaluation of simulation data are included. Vehicle subsystems modules, module integration, special test requirements, and reference data formats are also described.

  8. Interpolation/extrapolation technique with application to hypervelocity impact of space debris

    NASA Technical Reports Server (NTRS)

    Rule, William K.

    1992-01-01

    A new technique for the interpolation/extrapolation of engineering data is described. The technique easily allows for the incorporation of additional independent variables, and the most suitable data in the data base is automatically used for each prediction. The technique provides diagnostics for assessing the reliability of the prediction. Two sets of predictions made for known 5-degree-of-freedom, 15-parameter functions using the new technique produced an average coefficient of determination of 0.949. Here, the technique is applied to the prediction of damage to the Space Station from hypervelocity impact of space debris. A new set of impact data is presented for this purpose. Reasonable predictions for bumper damage were obtained, but predictions of pressure wall and multilayer insulation damage were poor.

  9. Innovative Techniques to Model, Analyze and Monitor Space Effects on Air Force Space-Based Systems

    DTIC Science & Technology

    2010-03-20

    of Comets in the Heliosphere as Observed by SMEI 4 2.8. Zodiacal Light Observations and Modeling 5 2.9. Space Weather Forecasting Lab (SWFL...returned. SMEI is a proof-of- principle experiment for providing an early warning of 1-3 days of the arrival at Earth of a coronal mass ejection (CME...Air Force. Its 1 primary mission was to detect and track Coronal Mass Ejections (CMEs) en route to Earth and to design and test technology that

  10. Retroperitoneal Laparoscopy in Dogs: Access Technique, Working Space, and Surgical Anatomy

    PubMed Central

    Jeong, Junemoe; Ko, Jonghyeok; Lim, Hyunjoo; Kweon, Oh‐Kyeong

    2016-01-01

    Objective To develop and describe a laparoscopic retroperitoneal access technique, investigate working space establishment, and describe the surgical anatomy in the retroperitoneal space as an initial step for clinical application of retroperitoneal laparoscopy in dogs. Study Design Cadaveric and experimental study. Animals Cadaveric (n=8) and healthy (n=6) adult dogs. Methods The retroperitoneal access technique was developed in 3 cadavers based on the human technique and transperitoneal observation. Its application and working space establishment with carbon dioxide (CO2) insufflation alone was evaluated in 5 cadavers by observing with a transperitoneal telescope and in 6 live dogs by repeated computed tomography (CT) scans at pressure of 0, 5, 10, and 15 mmHg. Recordings of retroperitoneoscopy as well as working space volume and linear dimensions measured on CT images were analyzed. Results Retroperitoneal access and working space establishment with CO2 insufflation alone were successfully performed in all 6 live dogs. The only complication observed was in 1 dog that developed subclinical pneumomediastinum. As pressure increased, working space was established from the ipsilateral to the contralateral side, and peritoneal tearing eventually developed. Working space volume increased significantly from 5 mmHg and linear dimensions increased significantly from 0 to 10 mmHg. With pneumo‐retroperitoneum above 5 mmHg, retroperitoneal organs, including kidneys and adrenal glands, were easily visualized. Conclusion The retroperitoneal access technique and working space establishment with CO2 insufflation starting with 5 mmHg and increasing to 10 mmHg provided adequate working space and visualization of retroperitoneal organs, which may allow direct access for retroperitoneal laparoscopy in dogs. PMID:27731512

  11. Retroperitoneal Laparoscopy in Dogs: Access Technique, Working Space, and Surgical Anatomy.

    PubMed

    Jeong, Junemoe; Ko, Jonghyeok; Lim, Hyunjoo; Kweon, Oh-Kyeong; Kim, Wan Hee

    2016-11-01

    To develop and describe a laparoscopic retroperitoneal access technique, investigate working space establishment, and describe the surgical anatomy in the retroperitoneal space as an initial step for clinical application of retroperitoneal laparoscopy in dogs. Cadaveric and experimental study. Cadaveric (n=8) and healthy (n=6) adult dogs. The retroperitoneal access technique was developed in 3 cadavers based on the human technique and transperitoneal observation. Its application and working space establishment with carbon dioxide (CO2 ) insufflation alone was evaluated in 5 cadavers by observing with a transperitoneal telescope and in 6 live dogs by repeated computed tomography (CT) scans at pressure of 0, 5, 10, and 15 mmHg. Recordings of retroperitoneoscopy as well as working space volume and linear dimensions measured on CT images were analyzed. Retroperitoneal access and working space establishment with CO2 insufflation alone were successfully performed in all 6 live dogs. The only complication observed was in 1 dog that developed subclinical pneumomediastinum. As pressure increased, working space was established from the ipsilateral to the contralateral side, and peritoneal tearing eventually developed. Working space volume increased significantly from 5 mmHg and linear dimensions increased significantly from 0 to 10 mmHg. With pneumo-retroperitoneum above 5 mmHg, retroperitoneal organs, including kidneys and adrenal glands, were easily visualized. The retroperitoneal access technique and working space establishment with CO2 insufflation starting with 5 mmHg and increasing to 10 mmHg provided adequate working space and visualization of retroperitoneal organs, which may allow direct access for retroperitoneal laparoscopy in dogs. © 2016 The Authors. Veterinary Surgery published by Wiley Periodicals, Inc., on behalf of The American College of Veterinary Surgeons.

  12. Surface and snowdrift sublimation at Princess Elisabeth station, East Antarctica

    NASA Astrophysics Data System (ADS)

    Thiery, W.; Gorodetskaya, I. V.; Bintanja, R.; Van Lipzig, N. P. M.; Van den Broeke, M. R.; Reijmer, C. H.; Kuipers Munneke, P.

    2012-08-01

    In the near-coastal regions of Antarctica, a significant fraction of the snow precipitating onto the surface is removed again through sublimation - either directly from the surface or from drifting snow particles. Meteorological observations from an Automatic Weather Station (AWS) near the Belgian research station Princess Elisabeth in Dronning Maud Land, East-Antarctica, are used to study surface and snowdrift sublimation and to assess their impacts on both the surface mass balance and the surface energy balance during 2009 and 2010. Comparison to three other AWSs in Dronning Maud Land with 11 to 13 yr of observations shows that sublimation has a significant influence on the surface mass balance at katabatic locations by removing 10-23% of their total precipitation, but at the same time reveals anomalously low surface and snowdrift sublimation rates at Princess Elisabeth (17 mm w.e. yr-1 compared to 42 mm w.e. yr-1 at Svea Cross and 52 mm w.e. yr-1 at Wasa/Aboa). This anomaly is attributed to local topography, which shields the station from strong katabatic influence, and, therefore, on the one hand allows for a strong surface inversion to persist throughout most of the year and on the other hand causes a lower probability of occurrence of intermediately strong winds. This wind speed class turns out to contribute most to the total snowdrift sublimation mass flux, given its ability to lift a high number of particles while still allowing for considerable undersaturation.

  13. Novel techniques for the thermal management of space-based, high-power microwave tubes

    NASA Astrophysics Data System (ADS)

    Rose, M. F.; Hyder, Anthony K.; Askew, R. F.; Chow, L.; Gilmour, A. S., Jr.; Faghri, A.

    1991-10-01

    This work is based in part on a study by the authors to determine the applicability of several concepts to the cooling of high-power linear microwave tubes operating in space under a variety of conditions. The authors focus on: direct radiation to space, beam exit to space, thermal storage, secondary coolant loops/heat pipes, and the use of supercritical hydrogen as a coolant with subsequent ejection to space. Each of these techniques is evaluated within the framework of a neutral particle beam weapons system or other limited duty cycle device which might lay dormant for long periods of time, come to life, and function reliably for a specified time. System impact for each technique is estimated in terms of impact on weight, volume, spacecraft interaction, and ease of implementation.

  14. Modeling the Variability and Importance of Snow Sublimation in the North-Central Colorado Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Sexstone, G. A.; Clow, D. W.; Fassnacht, S. R.; Liston, G. E.; Hiemstra, C. A.; Knowles, J. F.

    2016-12-01

    In the western United States, where seasonal snowmelt is a critical water resource for ecological and anthropological needs, snow sublimation (sublimation) has been suggested by many studies to be an important component of the snow cover mass balance. However, few studies have evaluated the spatial and temporal variability of sublimation in complex mountainous environments. In this study, we use a process-based snow model (SnowModel) and eddy covariance (EC) measurements to evaluate the variability and importance of sublimation across the north-central Colorado Rocky Mountains for 5 water years (WY 2011 - WY 2015). In-situ EC observations of sublimation compare well with modeled sublimation at sites dominated by surface and canopy components of sublimation, but model verification of blowing sublimation in alpine areas was not feasible because these fluxes often occur when snow is in turbulent suspension, which cannot always be resolved by EC instrumentation. Model simulations showed substantial spatial and temporal variability of sublimation across the study domain. Sublimation rates were found to exhibit differences across landscape characteristics such as elevation and land cover. Land cover type was an important driver of snow sublimation variability, with substantial sublimation occurring in alpine and forested areas, and relatively lower sublimation occurring in open areas below treeline. Sublimation from forested areas accounted for the majority of modeled sublimation losses across the study domain and highlights the importance of sublimation from snow stored in the forest canopy in this region. Additionally, the interannual differences in total sublimation were strongly linked with seasonal snowfall amounts. Results from this study suggest that snow sublimation is a significant component of the winter water balance and have important implications for future water management and decision making.

  15. Search of the Na in the Region of the Sublimation of the Near-Sun Dust

    NASA Astrophysics Data System (ADS)

    Delone, A. B.; Divlekeev, M. I.; Suchanov, E. A.; Gulyaev, R. A.; Yakunina, G. V.; Porfir'eva, G. A.

    An evaluation of the Na number in the sublimation zone of the near-Sun interplanetary dust, based on a comparison with the intensity of the radiation of the Na in the Earth atmosphere, has been obtained. The abundance of the Na in the column along the line of sight is less than 2 x 108atom cm-2. This result is compared with the values, determined on the base of the brightness of the zodiacal light, F-corona and by direct measurements of the dust density with space experiments.

  16. Sublimating grains in the coma of new comets originating from the Oort Cloud

    NASA Astrophysics Data System (ADS)

    Faggi, S.; Tozzi, G.; Brucato, J.; Bruni, I.; Licandro, J.; Mazzotta Epifani, E.; Meech, K.; Mottola, S.

    2014-07-01

    It is expected that a billion of years of space weathering (see, e.g., Kanuchova et al., 2012, Icarus, 221, 12) produces a crust of organic matter that will be released when a comet enters, for the first time, in the inner Solar System. When approaching to the Sun, a comet is at heliocentric distances r_h greater than 3 au, the sublimation of CO and CO_2 is the main source of cometary activity. At shorter distances, the sublimation of water becomes the most important mechanism of activity. The gases escaping from the nucleus cause drag for the coma grains that can be refractory dust (silicates, carbon), water ice, and/or organic ices. Oort comets at their first passage in the inner Solar System, should produce an halo of organic or water ice particles. Recently, our group started to monitor new, inbound, bright Oort comets (C/2011 F1, C/2012 S1, C/2012 K1, C/2013 V5, C/2012 F3) to search for these grains. The method consists of detecting the cloud of sublimating grains in the inner coma by using the ΣAf(ρ) function (Tozzi et al., 2007, A&A, 476, 979). However, this over-population of grains, beside the sublimation, can be also due to short-time activity (outburst) or too large grains expanding at very slow velocity, as it has been found in comet 67P/C-G (Tozzi et al., 2011, A&A, 531, 54). To discriminate between the phenomena, it is necessary to monitor the comet both at short timescales for the outbursts (by repeating the observations after a few nights), and in a longer term (weeks to months). If the cloud does not expand with decreasing heliocentric distance, there is a high probability that organic and/or water-ice grains are present. We can discriminate between organic and water-ice grains by measuring their color and spectra. In this work, we will present the results obtained from the observations of C/2011 F1 (LINEAR) and C/2012 S1 (ISON). The comparison between data and theoretical simulations, obtained with a simple model assuming sublimating grains

  17. Adaptive Switching Technique for Space-Time/Frequency Coded OFDM Systems

    NASA Astrophysics Data System (ADS)

    Change, Namseok; Gil, Gye-Tae; Kang, Joonhyuk; Yu, Gangyoul

    In this letter, a switched transmission technique is presented that can provide the orthogonal frequency division multiplexing (OFDM) systems with additional diversity gain. The space-time block coding (STBC) and space-frequency block coding (SFBC) are considered for the transmission of the OFDM signals. A proper coding scheme is selected based on the estimated normalized delay spread and normalized Doppler spread. The selection criterion is derived empirically. It is shown through computer simulations that the proposed switching technique can improve the bit error rate (BER) performance of an OFDM system when the corresponding wireless channel has some time variation of time selectivity as well as frequency selectivity.

  18. Simple linear technique for the measurement of space-time coupling in ultrashort optical pulses.

    PubMed

    Dorrer, Christophe; Walmsley, Ian A

    2002-11-01

    We demonstrate a simple sensitive linear technique that quantifies the spatiotemporal coupling in the electric field of an ultrashort optical pulse. The space-time uniformity of the field can be determined with only time-stationary filters and square-law integrating detectors, even if it is impossible to measure the temporal electric field in this way. A degree of spatiotemporal uniformity is defined and can be used with the demonstrated diagnostic to quantify space-time coupling. Experimental measurements of space-time coupling due to linear and nonlinear focusing, refraction, and diffraction are presented.

  19. Study of ceramic products and processing techniques in space. [using computerized simulation

    NASA Technical Reports Server (NTRS)

    Markworth, A. J.; Oldfield, W.

    1974-01-01

    An analysis of the solidification kinetics of beta alumina in a zero-gravity environment was carried out, using computer-simulation techniques, in order to assess the feasibility of producing high-quality single crystals of this material in space. The two coupled transport processes included were movement of the solid-liquid interface and diffusion of sodium atoms in the melt. Results of the simulation indicate that appreciable crystal-growth rates can be attained in space. Considerations were also made of the advantages offered by high-quality single crystals of beta alumina for use as a solid electrolyte; these clearly indicate that space-grown materials are superior in many respects to analogous terrestrially-grown crystals. Likewise, economic considerations, based on the rapidly expanding technological applications for beta alumina and related fast ionic conductors, reveal that the many superior qualities of space-grown material justify the added expense and experimental detail associated with space processing.

  20. Formation of filamentary sublimate residues (FSR) from mineral grains

    SciTech Connect

    Storrs, A.D.; Fanale, F.P.; Saunders, R.S.; Stephens, J.B.

    1988-12-01

    The significant interparticle forces observed between solar system dust grains upon desorption or sublimation of excess volatiles in simulated Martian or cometary environments are presently investigated, in order to more precisely define these mechanisms and to simulate the types of deposits thereby formed. Some classes of phyllosilicate mineral grains are noted to bond together to form a highly porous filamentary sublimate residue (FSR) exhibiting an exceptionally high tensile strength for its density; this may be important in its control of erosion and sublimation in Martian and cometary environments. It is concluded that FSR formation from clean mineral grains in water ice may be important in the formation of the Martian polar layered terrain. 41 references.

  1. On the interaction of sublimating gas with cometary bodies

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan K.

    Sublimation of volatiles is a defining process of comet nuclei, and profoundly affects their dynamics, structure, and appearance. Central to understanding the processes by which comets formed and subsequently evolved is a careful computation of this sublimation pressure as a function of heliocentric distance. Unlike previous efforts, I develop a thermodynamic method to numerically compute the sublimation pressure of any species from limited knowledge of its physical properties. I then describe a novel cometary disruption mechanism in which this sublimation pressure induces differential stresses within the body of the nucleus that exceed its material strength, resulting in structural failure and breakup of the nucleus. I show that this mechanism is consistent with the behavior of Comet ISON (C/2012 S1), and use it to estimate the cohesive strength of ISON's nucleus, a first for a Long-Period Comet. Sublimating volatiles can also generate sublimative torques that alter the rotation state of the nucleus. However, computing these torques requires high-resolution information on the shape and activity of the nucleus, which is available only for the few nuclei visited by spacecraft. To remedy this, I develop a novel framework based on the YORP Effect (the torques asteroids experience by emitting thermal photons from their asymmetric shapes) to study the effects of sublimative torques on populations of cometary bodies. I take advantage of the similar manner in which surfaces emit both thermal photons and sublimating molecules to derive numerical relationships that describe sublimative torques by appropriately scaling the YORP torque equations. I then use this framework to explain the formation of dust striae (long linear features in the tails of Long-Period Comets that align with the Sun), which has remained an enigma for more than a century. I show that the observed ˜10-100 m chunks ejected from comet nuclei experience sublimative torques that spin them up to the point

  2. Canopy effects on snow sublimation from a central Arizona Basin

    NASA Astrophysics Data System (ADS)

    Svoma, Bohumil M.

    2017-01-01

    Guided by 30 m terrain and forest cover data, snow sublimation from the Salt River basin in the Southwest U.S. is simulated for years 2008 (wet year) and 2007 (dry year). Downscaled meteorological input correlates well (r 0.80) with independent observations at AmeriFlux sites. Additionally, model correlation and bias with eddy-covariance vapor flux observations is comparable to previous localized modeling efforts. Upon a 30% reduction in effective leaf area index, canopy sublimation decreases by 1.29 mm (27.0%) and 1.05 mm (23.0%) at the basin scale for the 2008 and 2007 simulations, respectively. Ground sublimation decreases 0.72 mm (4.75%) in 2008 and only 0.17 mm (1.5%) in 2007. Canopy snow-holding capacity and frequent unloading events at lower elevations limit the variability in canopy sublimation from wet year to dry year at the basin scale. The greater decrease in snowpack sublimation in the wet year is partly due to decreased longwave radiation from the canopy reduction over a more extensive snowpack than the dry year. This decrease overcomes the increased solar radiation and wind speed during winter. A second factor is that a greater extent of the snowpack persisted into spring in 2008 than 2007, and the large increase in shortwave flux upon canopy reduction increases melt rates, reducing duration. Only in heavily forested high elevations (>2900 m above sea level) in 2008 does the snowpack persist long enough into spring to result in increased ground sublimation upon canopy reduction. As forest cover change can occur rapidly, these results are critical from water resource and ecosystem function perspectives.

  3. Robust control of seismic structures using independent modal-space techniques

    NASA Astrophysics Data System (ADS)

    Martin, Kerry S.; Rao, Vittal S.; Cheng, Franklin Y.

    1996-04-01

    Active robust structural controls have been utilized in the control of aerospace structures for many years but they have only been recently investigated in the context of control for civil engineering structures. The results of an investigation of the utilization of these methods on building-like structures are presented in this paper. The closed-loop systems take into account the limited available actuation force and are inherently insensitive to parameter variations and modeling uncertainties. Independent modal-space control (IMSC) is a structural control technique where the multi-input-multi-output configuration-space system is transformed into a set of uncoupled single-input-single-output modal-space systems. A modal controller is designed for each modal-space system and the set of modal controllers is transformed back into configuration-space. By combining IMSC with robust control techniques such as LQG/LTR or H(infinity ), a robust structural control design technique is proposed in this paper. Robust IMSC techniques are employed for control of seismic structures where a small number of actuators are used to control the first few modes of the structure. We have designed and implemented robust IMSC controllers on an experimental building-like structure. This structure utilizes torque motor driven active tendons as actuators and rests on a shaking table which is capable of providing one dimensional base excitation similar to earthquake ground motion. A three input-three output model of the structure, including the torque motor actuators, was developed using experimental data. The experimental structural identification technique, based on standard modal analysis methods, provides the mathematical model that describes the behavior of the structure. An H(infinity ) based IMSC controller has been designed and implemented on this structure using a dSPACE control development system. The results show that the performance of the system is satisfactory in the presence of

  4. A technique for revealing scale-dependent patterns in fracture spacing data

    NASA Astrophysics Data System (ADS)

    Roy, Ankur; Perfect, Edmund; Dunne, William M.; McKay, Larry D.

    2014-07-01

    Data on fracture spacing along scan lines have been widely analyzed for the purposes of characterization. Most of these studies, however, either consider the cumulative frequency of spacing data without regard to the actual sequence of the spacing values or compute an average spacing that may not work for clustered fractures. The coefficient of variation parameter is often used to differentiate between clustered, random, and anticlustered fractures in a scan line but does not address the issue of scale-dependent variations in spacing. Lacunarity is a parameter that has been previously used for delineating scale-dependent clustering in fracture networks with similar fractal dimensions. This technique has the further capability of identifying scales at which different patterns emerge within the same data set. Lacunarity can also delineate possible fractal behavior. This paper tests the ability of lacunarity to find patterns (fractal/uniform/random) within synthetic and natural fracture clusters. A set of four model scan lines (uniformly spaced fractures, periodically spaced fracture clusters, fractal fracture clusters, and random fractures) was considered. The first derivative of the lacunarity curves of these models was used to find the intercluster distance and organization of fractures within the clusters. The same technique was then applied to a set of two natural fracture scan line data, one with fracture clusters with fractal organization within and the other with randomly spaced fractures. It was found that the proposed technique could discriminate between the random and clustered patterns, find the intercluster distance, and identify the type of spatial organization within the clusters.

  5. Alumina Paste Sublimation Suppression Barrier for Thermoelectric Device

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah (Inventor); Caillat, Thierry (Inventor)

    2014-01-01

    Alumina as a sublimation suppression barrier for a Zintl thermoelectric material in a thermoelectric power generation device operating at high temperature, e.g. at or above 1000K, is disclosed. The Zintl thermoelectric material may comprise Yb.sub.14MnSb.sub.11. The alumina may be applied as an adhesive paste dried and cured on a substantially oxide free surface of the Zintl thermoelectric material and polished to a final thickness. The sublimation suppression barrier may be finalized by baking out the alumina layer on the Zintl thermoelectric material until it becomes substantially clogged with ytterbia.

  6. Drifting snow and its sublimation in turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Li, Guang; Huang, Ning; Wang, Zhengshi

    2017-04-01

    Drifting snow is a special process of mass-energy transport in hydrological cycle especially in alpine region. It can not only change the snow distribution, but also result in phase change of ice crystal into water vapour, which is so called drifting snow sublimation. Thus drifting snow is of glaciological and hydrological importance in cold regions. In this paper, recent research on drifting snow and its sublimation is reviewed, and some new progresses by our research team in Lanzhou University are also introduced.

  7. Sublimation and Irradiation of Glycolaldehyde/Water Ices

    NASA Astrophysics Data System (ADS)

    Burke, Daren; Brown, W. A.; Viti, S.; Woods, P. M.; Slater, B.

    2012-05-01

    There is currently great interest among astronomers and astrobiologists in the inventory of organic molecules in space, in particular in star and planet-forming regions. Observations towards the Galactic Centre have revealed a rich and complex chemistry, from simple organic molecules such as methane (CH4) and methanol (CH3OH) to the recent detection of ethyl formate (C2H5OCHO) and n-propyl cyanide (C3H7CN). Amongst the most important organic species detected in space is glycolaldehyde (CH2OHCHO), an isomer of methyl formate (HCOOCH3) and acetic acid (CH3COOH). Glycolaldehyde is the simplest of the monosaccharide sugars and it reacts with propenal to form ribose, a central constituent of RNA. As a consequence, it is thought that glycolaldehyde may have a role in the origins of life in our universe. We present a detailed investigation of the adsorption and desorption of glycolaldehyde and methyl formate using temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS) under ultra-high vacuum. The sublimation of glycolaldehyde/water and methyl formate/water containing ices from a model carbonaceous grain surface (graphite) will be presented, along with kinetic parameters for desorption (such as the binding energy, order of desorption and desorption pre-exponential factor) derived from analysis of TPD. These experimental parameters will be incorporated into astronomical models of star-forming regions. Additional experiments investigating the stability of glycolaldehyde/water containing ices to electron/UV irradiation will also be discussed. Electron irradiation (simulating the effect of cosmic ray ionisation, which produces electrons) and UV irradiation (over a range of wavelengths) is used to examine competing routes for non-thermal desorption, decomposition and formation. RAIRS and TPD will be used to identify any reaction products and to monitor the desorption/decomposition of glycolaldehyde as a function of irradiation time. This

  8. Advancing IM-CW Lidar Modulation Techniques for ASCENDS CO2 Column Measurements from Space

    NASA Astrophysics Data System (ADS)

    Campbell, J. F.; Lin, B.; Nehrir, A. R.; Harrison, F. W.; Chen, S.; Obland, M. D.

    2013-12-01

    Global atmospheric carbon dioxide (CO2) measurements through the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) decadal survey recommended space mission are critical for improving our understanding of CO2 sources and sinks. IM-CW (Intensity Modulated Continuous Wave) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS science requirements. In previous laboratory and flight experiments we have successfully used linear swept frequency modulation to discriminate surface lidar returns from intermediate aerosol and cloud contamination. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate clouds, which is a requirement for the inversion of the CO2 column mixing ratio from the instrument optical depth measurements, has been demonstrated with the linear swept frequency modulation technique. We are concurrently investigating advanced techniques to help improve the auto-correlation properties of the transmitted waveform implemented through physical hardware to make cloud rejection more robust in special restricted scenarios. Several different modulation techniques are compared including orthogonal linear swept, orthogonal non-linear swept, time shifted PN, sine wave modulated PN, and sine wave pulsed PN. Different PN code techniques are presented that are appropriate for different types of lidar hardware, including our current ASCENDS IM-CW concept space hardware. These techniques have excellent auto-correlation properties without sidelobes while possessing a finite bandwidth (by way of a new cyclic digital filter), which will reduce bias error in the presence of multiple scatterers. Our analyses show that the studied modulation techniques can increase the accuracy of CO2 column measurements from space.

  9. COMPARISON OF MEASUREMENT TECHNIQUES FOR QUANTIFYING SELECTED ORGANIC EMISSIONS FROM KEROSENE SPACE HEATERS

    EPA Science Inventory

    The report goes results of (1) a comparison the hood and chamber techniques for quantifying pollutant emission rates from unvented combustion appliances, and (2) an assessment of the semivolatile and nonvolatile organic-compound emissions from unvented kerosene space heaters. In ...

  10. Measurement of complex terahertz dielectric properties of polymers using an improved free-space technique

    NASA Astrophysics Data System (ADS)

    Chang, Tianying; Zhang, Xiansheng; Yang, Chuanfa; Sun, Zhonglin; Cui, Hong-Liang

    2017-04-01

    The complex dielectric properties of non-polar solid polymer materials were measured in the terahertz (THz) band by a free-space technique employing a frequency-extended vector network analyzer (VNA), and by THz time-domain spectroscopy (TDS). Mindful of THz wave’s unique characteristics, the free-space method for measurement of material dielectric properties in the microwave band was expanded and improved for application in the THz frequency region. To ascertain the soundness and utility of the proposed method, measurements of the complex dielectric properties of a variety of polymers were carried out, including polytetrafluoroethylene (PTFE, known also by the brand name Teflon), polypropylene (PP), polyethylene (PE), and glass fiber resin (Composite Stone). The free-space method relies on the determination of electromagnetic scattering parameters (S-parameters) of the sample, with the gated-reflect-line (GRL) calibration technique commonly employed using a VNA. Subsequently, based on the S-parameters, the dielectric constant and loss characteristic of the sample were calculated by using a Newtonian iterative algorithm. To verify the calculated results, THz TDS technique, which produced Fresnel parameters such as reflection and transmission coefficients, was also used to independently determine the dielectric properties of these polymer samples, with results satisfactorily corroborating those obtained by the free-space extended microwave technique.

  11. Nondestructive Inspection Techniques for Friction Stir Weld Verification on the Space Shuttle External Tank

    NASA Technical Reports Server (NTRS)

    Suits, Michael W.; Leak, Jeffery; Bryson, Craig

    2003-01-01

    Friction Stir Welding (FSW) has gained wide acceptance as a reliable joining process for aerospace hardware as witnessed by its recent incorporation into the Delta Launch vehicle cryotanks. This paper describes the development of nondestructive evaluation methods and techniques used to verify the FSW process for NASA's Space Shuttle.

  12. Analysis of space tug operating techniques supplemental report (study 2.4)

    NASA Technical Reports Server (NTRS)

    1972-01-01

    An analysis of space tug operating techniques is presented. The subjects discussed are: (1) sustaining engineering requirements, (2) off-site facility requirements, (3) evaluation of tug checkout alternatives, and (4) spares provisioning. Tables of data are included to clarify the written presentation.

  13. COMPARISON OF MEASUREMENT TECHNIQUES FOR QUANTIFYING SELECTED ORGANIC EMISSIONS FROM KEROSENE SPACE HEATERS

    EPA Science Inventory

    The report goes results of (1) a comparison the hood and chamber techniques for quantifying pollutant emission rates from unvented combustion appliances, and (2) an assessment of the semivolatile and nonvolatile organic-compound emissions from unvented kerosene space heaters. In ...

  14. Sublimation of Ices Containing Organics and/or Minerals and Implications for Icy Bodies Surface Structure and Spectral Properties

    NASA Astrophysics Data System (ADS)

    Poch, O.; Pommerol, A.; Jost, B.; Yoldi, Z.; Carrasco, N.; Szopa, C.; Thomas, N.

    2015-12-01

    The surfaces of many objects in the Solar System comprise substantial quantities of water ice either in pure form or mixed with minerals and/or organic molecules. Sublimation is a process responsible for shaping and changing the reflectance properties of these objects. We present laboratory data on the evolution of the structure and the visible and near-infrared spectral reflectance of icy surfaces made of mixtures of water ice and non-volatile components (complex organic matter and silicates), as they undergo sublimation of the water ice under low temperature and pressure conditions (Poch et al., under review). We prepared icy surfaces which are potential analogues of ices found on comets, icy satellites or trans-neptunian objects (TNOs). The experiments were carried out in the SCITEAS simulation setup recently built as part of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern (Pommerol et al., 2015a). As the water ice sublimated, we observed in situ the formation of a sublimation lag deposit, or sublimation mantle, made of the non-volatiles at the top of the samples. The texture (porosity, internal cohesiveness etc.), the activity (outbursts and ejection of mantle fragments) and the spectro-photometric properties of this mantle are found to differ strongly depending on the chemical nature of the non-volatiles, the size of their particles, the way they are mixed with the volatile component and the dust/ice mass ratio. The results also indicate how the band depths of the sub-surface water ice evolve during the build-up of the sublimation mantle. These data provide useful references for interpreting remote-sensing observations of Rosetta (see Pommerol et al., 2015b), and also New Horizons. Poch, O., et al., under review in IcarusPommerol, A., et al., 2015a, Planet. Space Sci. 109-110, 106-122. http://dx.doi.org/10.1016/j.pss.2015.02.004Pommerol, A., et al., 2015b, Astronomy and Astrophysics, in press. http://dx.doi.org/10.1051/0004-6361/201525977

  15. Large antenna experiments aboard the space shuttle: Application of nonuniform sampling techniques

    NASA Technical Reports Server (NTRS)

    Rahmatsamii, Y.

    1988-01-01

    Future satellite communication and scientific spacecraft will utilize antennas with dimensions as large as 20 meters. In order to commercially use these large, low sidelobe and multiple beam antennas, a high level of confidence must be established as to their performance in the 0-g and space environment. Furthermore, it will be desirable to demonstrate the applicability of surface compensation techniques for slowly varying surface distortions which could result from thermal effects. An overview of recent advances in performing RF measurements on large antennas is presented with emphasis given to the application of a space based far-field range utilizing the Space Shuttle and the concept of a newly developed nonuniform sampling technique.

  16. Application of Soft Computing Techniques to Experimental Space Plasma Turbulence Observations - Genetic Algorithms

    NASA Astrophysics Data System (ADS)

    Bates, I.; Lawton, A.; Breikin, T.; Dunlop, M.

    Space Systems Group, University of Sheffield, U.K. Automatic Control and Systems Engineering, University of Sheffield, U.K. 3 Imperial College, London, U.K.A Genetic Algorithm (GA) approach is presented to solve a problem for turbulent space plasma system modelling in the form of Generalised Frequency Response Functions (GFRFs), using in-situ multi-satellite magnetic field measurements of the plasma turbulence. Soft Computing techniques have now been used for many years in Industry for nonlinear system identification. These techniques approach the problem of understanding a system, e.g. a chemical plant or a jet engine, by model structure selection and fitting parameters of the chosen model for the system using measured inputs and outputs of the system, which can then be used to determine physical characteristics of the system. GAs are one such technique that has been developed, providing essentially a series of solutions that evolve in a way to improve the model. Experimental space plasma turbulence studies have benefited from these System Identification techniques. Multi-point satellite observations provide input and output measurements of the turbulent plasma system. In previous work it was found natural to fit parameters to GFRFs, which derive from Volterra series and lead to quantitative measurements of linear wave-field growth and higher order wave-wave interactions. In previous work these techniques were applied using a Least Squares (LS) parameter fit. Results using GAs are compared to results obtained from the LS approach.

  17. Analysis of High Contrast Imaging Techniques for Space Based Direct Planetary Imaging

    NASA Technical Reports Server (NTRS)

    Lyon, Richard G.; Gezari, Dan Y.; Nisenson, P.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We report on our ongoing investigations of a number of techniques for direct detection and imaging of Earth-like planets around nearby stellar sources. Herein, we give a quantitative analysis of these techniques and compare and contrast them via computer simulations. The techniques we will be reporting on are Bracewell Interferometry, Nisenson Apodized Square Aperture, and Coronagraphic masking techniques. We parameterize our results with respect to wavelength, aperture size, effects of mirror speckle, both mid- and high-spatial frequency, detector and photon noise as well pointing error. The recent numerous detections of Jupiter and Saturn like planets has driven a resurgence in research of space based high contrast imaging techniques for direct planetary imaging. Work is currently ongoing for concepts for NASA's Terrestrial Planet Finder mission and a number of study teams have been funded. The authors are members of one team.

  18. Signal Detection Techniques for Diagnostic Monitoring of Space Shuttle Main Engine Turbomachinery

    NASA Technical Reports Server (NTRS)

    Coffin, Thomas; Jong, Jen-Yi

    1986-01-01

    An investigation to develop, implement, and evaluate signal analysis techniques for the detection and classification of incipient mechanical failures in turbomachinery is reviewed. A brief description of the Space Shuttle Main Engine (SSME) test/measurement program is presented. Signal analysis techniques available to describe dynamic measurement characteristics are reviewed. Time domain and spectral methods are described, and statistical classification in terms of moments is discussed. Several of these waveform analysis techniques have been implemented on a computer and applied to dynamc signals. A laboratory evaluation of the methods with respect to signal detection capability is described. A unique coherence function (the hyper-coherence) was developed through the course of this investigation, which appears promising as a diagnostic tool. This technique and several other non-linear methods of signal analysis are presented and illustrated by application. Software for application of these techniques has been installed on the signal processing system at the NASA/MSFC Systems Dynamics Laboratory.

  19. Alumina Paste Layer as a Sublimation Suppression Barrier for Yb14MnSb11

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah; Caillat, Thierry

    2010-01-01

    Sublimation is a major cause of degradation of thermoelectric power generation systems. Most thermoelectric materials tend to have peak values at the temperature where sublimation occurs. A sublimation barrier is needed that is stable at operating temperatures, inert against thermoelectric materials, and able to withstand thermal cycling stress. A porous alumina paste layer is suitable as a sublimation barrier for Yb14MnSb11. It can accommodate stress generated by the thermal expansion discrepancy between the suppression layer and thermoelectric materials. Sublimation suppression is achieved by filling pores naturally with YbO2, a natural byproduct of sublimation. YbO2 generated during the sublimation of Yb14MnSb11 fills the porous structure of the alumina paste, causing sublimation to decrease with time as the pores become filled.

  20. A new technique for in situ measurement of the composition of neutral gas in interplanetary space

    NASA Technical Reports Server (NTRS)

    Gruntman, Michael A.

    1993-01-01

    Neutral atoms in interplanetary space play an important role in many processes relevant to the formation and evolution of the Solar System. An experimental approach is proposed for in situ atom detection based on the conversion of neutral atoms to negative ions at a specially prepared sensitive surface. Negative ions are subsequently analyzed and detected in an essentially noise-free mode. The use of the technique for in situ study of the composition of neutral interstellar atoms is considered. It is shown that interstellar H, D, and O atoms and possibly H2 molecules can be measured by the proposed technique. The experiment can be performed from a high-apogee Earth-orbiting satellite or from a deep space probe. Possible applications of the technique are discussed.

  1. Techniques used for limiting degradation products of polymeric materials for use in the space environment

    NASA Technical Reports Server (NTRS)

    Vest, C. E.; Park, J. J.

    1978-01-01

    Techniques are discussed for limiting or controlling the degradation products (outgassing) of polymeric materials in the space environment. One technique, now ASTM E-595-77, is used to screen out those materials which lose greater than 1% Total Mass Loss when in vacuum for 24 hours at 125 C and which have more than 0.10% Collected Volatile Condensable Materials condensing on a collector surface at 25 C. Examples of silicone materials which are high and low in outgassing are given. The numerous mechanical motions in spacecraft experiments require liquid lubricants which also might degrade in space. Labyrinth seals and barrier films are utilized to limit the degradation of or from these lubricants. A recoverable in-flight experiment has been proposed for making definitive measurements of how effective these techniques are in limiting the amounts and escape paths of outgassed molecules.

  2. Surgical technique: The intercostal space approach to the internal mammary vessels in 463 microvascular breast reconstructions.

    PubMed

    Darcy, Catharine M; Smit, Jeroen M; Audolfsson, Thorir; Acosta, Rafael

    2011-01-01

    The internal mammary vessels are one of the most frequently used recipient sites for microsurgical free-flap breast reconstruction, and an accepted technique to expose these vessels involves removal of a segment of costal cartilage of the rib. However, in some patients, cartilage removal may result in a visible medial chest-wall depression that requires corrective procedures. We, therefore, use an intercostal space approach to the internal mammary vessels, as there is minimal disturbance of the costal cartilage with this technique. We have developed and performed our technique over an 8-year period in 463 microvascular breast reconstructions, and present it here as it contains modifications not previously described that may be of interest to other surgeons. There was no serious morbidity associated with the intercostal space approach, the internal mammary vessels were reliably and safely exposed in all these cases and the flap success rate was 95.8%. Copyright © 2010. Published by Elsevier Ltd.

  3. Multi-Technique Reprocessing and Combination using “Space-Ties”

    NASA Astrophysics Data System (ADS)

    Springer, T.; Dilssner, F.; Escobar, D.; Flohrer, C.; Otten, M.; Romero, I.; Dow, J. M.

    2009-12-01

    During 2008 and 2009 ESOC has reprocessed the historic data from the IDS, IGS, and ILRS! Our 3 solution were computed with one and the same software running on the same machine and using, as far as possible, identical settings, a unique achievement. Any systematic differences between the technique dependent reference frame solutions must therefore be caused by the techniques itself, and not because of model differences or errors! Our three technique dependent solutions should give us a very good understanding of the technique dependent effects. In the ITRF reference frame realisations the reference frame solutions from the individual techniques are combined using the local ties as measured at the stations. Besides possible errors and inaccuracies in these site-ties, this approach also suffers from the fact that the ILRS and IVS both offer very few stations with a far from global homogeneous distribution. At ESOC we have now made a small but significant step forward by including the SLR observations of the GNSS (GPS and GLONASS) satellites in our GNSS solutions. This allows to combine the ILRS and IGS reference frames by, besides using the site-ties at the stations, also using the “Space-Ties”. With space-ties we mean the vector between the position of the optical phase centre of the SLR laser reflector array and the GPS transmit antenna. Of course these “space-ties” are also not perfectly known but nevertheless they allow a much more rigorous combination of the two reference frames. And, very important for the GNSS technique, they allow the direct estimation of the GNSS satellite transmitter phase centre offset. In our presentation will give an overview of our IDS, IGS, and ILRS reprocessing efforts. We will conclude our presentation by demonstrating the benefits of “Space-Ties”.

  4. Design and development of correlation techniques to maintain a space surveillance system catalogue

    NASA Astrophysics Data System (ADS)

    Olmedo, E.; Sánchez Ortiz, Noelia; Lerate, Mercedes; Belló-Mora, Miguel; Klinkrad, H.

    2009-10-01

    A growing interest exists in a future, autonomous European Space Surveillance System (ESSS). Currently, most of the knowledge about Earth-orbiting space objects is based on information provided by the USASPACECOM. This paper presents the required initial orbit determination (IOD) and correlation techniques to process optical measurements. Former studies were focused on the handling of radar measurements, which are summarised with the aim of describing a global procedure for processing hybrid measurement types (combination of radar and optic data for catalogue maintenance). The introduction of manoeuvres are presented due to their importance in the space object catalogue maintenance. The detection of uncatalogued objects and the successful correlation of already catalogued objects involve two different tasks for telescopes: survey and tasking. Assumptions for both strategies are developed on the basis of the previous work developed at the University of Berne (see [T. Flohrer, T. Schildknecht, R. Musci, E. Stöveken, Performance estimation for GEO space surveillance, Advances in Space Research 35 (2005). [1]; T. Flohrer, T. Schildknecht, R. Musci, Proposed strategies for optical observations in a future European Space Surveillance Network, presented in the 36th COSPAR Scientific Assembly (2006). [2]; R. Musci, T. Schildknecht, M. Ploner, Orbit improvement for GEO objects using follow-up observations, Advances in Space Research 34 (2004). [3]; R. Musci, T. Schildknecht, M. Ploner, G. Beutler, Orbit improvement for GTO objects using follow-up observations, Advances in Space Research 35 (2005). [4]; R. Musci, T. Schildknecht, T. Flohrer, G. Beutler, Concept for a catalogue of space debris in GEO, Proceedings of the Fourth European Conference on Space Debris, (ESA SP-587, 2005). [5

  5. The Digital Sublime: Lessons from Kelli Connell's "Double Life"

    ERIC Educational Resources Information Center

    Huang, Yi-hui

    2012-01-01

    The digital sublime refers to digital-composite photography that presents "the existence of something unpresentable" and that renders a matchless look a sophisticated fabrication, a perfect and clean composition, a maximum color saturation, a multiple-point perspective, and stunning or newfangled content. Abandoning the traditional one-shot mode…

  6. Modeling the development of martian sublimation thermokarst landforms

    USGS Publications Warehouse

    Dundas, Colin M.; Byrne, Shane; McEwen, Alfred S.

    2015-01-01

    Sublimation-thermokarst landforms result from collapse of the surface when ice is lost from the subsurface. On Mars, scalloped landforms with scales of decameters to kilometers are observed in the mid-latitudes and considered likely thermokarst features. We describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation. Over periods of tens of thousands of Mars years under conditions similar to the present, the model produces scallop-like features similar to those on the Martian surface, starting from much smaller initial disturbances. The model also indicates crater expansion when impacts occur in surfaces underlain by excess ice to some depth, with morphologies similar to observed landforms on the Martian northern plains. In order to produce these landforms by sublimation, substantial quantities of excess ice are required, at least comparable to the vertical extent of the landform, and such ice must remain in adjacent terrain to support the non-deflated surface. We suggest that Martian thermokarst features are consistent with formation by sublimation, without melting, and that significant thicknesses of very clean excess ice (up to many tens of meters, the depth of some scalloped depressions) are locally present in the Martian mid-latitudes. Climate conditions leading to melting at significant depth are not required.

  7. System for NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, R.A.

    1989-01-24

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with HNCO at a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid. 1 fig.

  8. Vapor transport and sublimation on Mullins Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Lamp, J. L.; Marchant, D. R.

    2017-05-01

    We utilize an environmental chamber capable of recreating the extreme polar conditions of the McMurdo Dry Valleys (MDV) of Antarctica to investigate the sublimation rate of the Mullins Valley debris-covered glacier (hereafter Mullins Glacier), reportedly one of the oldest debris-covered alpine glaciers in the world. We measure ice loss via sublimation beneath sediment thicknesses ranging from 0 to 69 mm; from this, we determine an effective diffusivity for Fickian vapor transport through Mullins till of (5.2 ± 0.3) ×10-6 m2s-1 at -10 °C. We use this value, coupled with micrometeorological data from Mullins Valley (atmospheric temperature, relative humidity, and soil temperature) to model the sublimation rate of buried glacier ice near the terminus of Mullins Glacier, where the overlying till thickness approaches 70 cm. We find that the ice-lowering rate during the modeled year (2011) was 0.066 mm under 70 cm of till, a value which is in line with previous estimates for exceedingly slow rates of ice sublimation. These results provide further evidence supporting the probable antiquity of Mullins Glacier ice and overall landscape stability in upland regions of the MDV.

  9. The Digital Sublime: Lessons from Kelli Connell's "Double Life"

    ERIC Educational Resources Information Center

    Huang, Yi-hui

    2012-01-01

    The digital sublime refers to digital-composite photography that presents "the existence of something unpresentable" and that renders a matchless look a sophisticated fabrication, a perfect and clean composition, a maximum color saturation, a multiple-point perspective, and stunning or newfangled content. Abandoning the traditional one-shot mode…

  10. Isotopic Fractionation of Water-Ice from Sublimation

    NASA Astrophysics Data System (ADS)

    Christensen, E.; Boyer, C.; Park, M.; Gormally, J.; Benitez, E.; Dominguez, G.

    2015-12-01

    Elizabeth Christensen, Charisa Boyer, Manesseh Park, Ezra Benitez, Gerardo Dominguez Understanding the multi-isotopic fractionation of water-ice that results from its sublimation may be important for understanding the isotopic composition of cometary ices. Here we describe an experimental setup whose purpose is to understand the effects of various astrophysical processes on the δD and δ18O and δ17O composition of water-ices. Our setup consists of an ultrahigh vacuum (UHV) chamber with oil free pumping, a closed cycle He cryostat to achieve low temperatures (capable of reaching 6K), and a vacuum line connected to the chamber via a UHV feed-through. Water isotopologues H216O, H218O, H217O, and HD16O samples can be measured after sublimation of water-ice with a cavity ring-down spectrometer (Picarro L2120-i) that is connected to the vacuum line. To perform these experiments, ambient water vapor was introduced into, frozen, and purified inside the UHV chamber (T< 150 K). Water-ice samples were sublimated for varying amounts of time to collect various fractions of the original reservoir. We will present the first results on the oxygen and deuterium isotopic fractionation of water-ice sublimation and discuss their implications for interpreting the isotopic compositions of cometary ices.

  11. Literary Study, Measurement, and the Sublime: Disciplinary Assessment

    ERIC Educational Resources Information Center

    Heiland, Donna, Ed.; Rosenthal, Laura J., Ed.

    2011-01-01

    This collection of essays, "Literary Study, Measurement, and the Sublime: Disciplinary Assessment," edited by Donna Heiland and Laura J. Rosenthal, represents an important new venture in the Foundation's communication program. The book is the product of many authors, including the editors, both of whom have written essays for it. But it…

  12. Modeling the development of martian sublimation thermokarst landforms

    NASA Astrophysics Data System (ADS)

    Dundas, Colin M.; Byrne, Shane; McEwen, Alfred S.

    2015-12-01

    Sublimation-thermokarst landforms result from collapse of the surface when ice is lost from the subsurface. On Mars, scalloped landforms with scales of decameters to kilometers are observed in the mid-latitudes and considered likely thermokarst features. We describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation. Over periods of tens of thousands of Mars years under conditions similar to the present, the model produces scallop-like features similar to those on the martian surface, starting from much smaller initial disturbances. The model also indicates crater expansion when impacts occur in surfaces underlain by excess ice to some depth, with morphologies similar to observed landforms on the martian northern plains. In order to produce these landforms by sublimation, substantial quantities of excess ice are required, at least comparable to the vertical extent of the landform, and such ice must remain in adjacent terrain to support the non-deflated surface. We suggest that martian thermokarst features are consistent with formation by sublimation, without melting, and that significant thicknesses of very clean excess ice (up to many tens of meters, the depth of some scalloped depressions) are locally present in the martian mid-latitudes. Climate conditions leading to melting at significant depth are not required.

  13. System for NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1989-01-01

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with HNCO at a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid.

  14. Differential Sublimation of Terrestrial Permafrost and the Ramifications for Terrain Features on Mars

    NASA Astrophysics Data System (ADS)

    Douglas, T. A.; Mellon, M. T.

    2016-09-01

    Sublimation loss of ice wedge ice in CRREL Permafrost Tunnel in Alaska (2.8 mm) is linear over 386 days, while ice cemented silt sublimation follows a decreasing relationship with time over 51 years with little sublimation over the past 20 years.

  15. Relationship between molecular descriptors and the enthalpies of sublimation of natural amino acids

    NASA Astrophysics Data System (ADS)

    Badelin, V. G.; Tyunina, V. V.; Girichev, G. V.; Tyunina, E. Yu.

    2016-07-01

    A multiparameter correlation between the enthalpies of sublimation and molecular descriptors of natural amino acids is proposed, based on generalized experimental and literature data on the heat effects of sublimation. The contributions from Van der Waals interactions, hydrogen bond formation, and electrostatic effects into enthalpy of sublimation has been evaluated using regression coefficients.

  16. A new technique to expose the hypopharyngeal space: The modified Killian's method.

    PubMed

    Sakai, Akihiro; Okami, Kenji; Sugimoto, Ryousuke; Ebisumoto, Koji; Yamamoto, Hikaru; Maki, Daisuke; Saito, Kosuke; Iida, Masahiro

    2014-04-01

    Recent remarkable progress in endoscopic technology has enabled the detection of superficial cancers that were undetectable in the past. However, even though advanced endoscopic technology can detect early lesions, it is useless unless it can provide wide exposure of an area. By modifying the Killian position, it is possible to observe a wider range of the hypopharyngeal space than is possible with conventional head positions. We report a revolutionary method that uses a new head position to widely open the hypopharynx. The technique is named "the Modified Killian's method." The patient is initially placed in the Killian position and then bent further forward from the original position (i.e., the modified Killian position). While in this position, the patient's head is turned and the Valsalva maneuver is applied. These additional maneuvers constitute the Modified Killian's method and widely expands the hypopharyngeal space. The conventional head position cannot open the hypopharyngeal space sufficiently; however, the Modified Killian's method opens the hypopharyngeal space very widely. The Modified Killian's method enables observation of the entire circumference of the hypopharyngeal space and the cervical esophageal entry. The Modified Killian's method may become an indispensable technique for observing the hypopharynx and detecting hypopharyngeal cancers. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  17. Sublimation of amino acids with enantiomeric excess amplification

    NASA Astrophysics Data System (ADS)

    Guillemin, Jean-Claude; Guillemin, Jean-Claude; Bellec, Aurelien

    The notion of chirality was first reported in 1848 by Pasteur, when he mechanically separated the two enantiomers of tartrate salts.[1] Amino acids are considered as the most important building blocks of life with sugars. On the Earth, the living systems are only composed of L- amino acids and D-sugars. Nowadays, the origin of homochirality on Earth is still unknown, and there are many theories trying to explain this phenomenon. Recently Cooks [2] and Feringa [3] reported that the sublimation of small amounts of L and D amino acid mixtures containing an excess of one of them leads to a huge enantiomeric excess (ee) enhancement of the sublimate. We reinvestigated these experiments to determine the rules leading to this enhancement. Starting from mixtures of L- and DL leucine we observed increasing and decreasing of the ee in function of the starting ratios. By the use of 13C derivatives, the origin of the sublimed enantiomers has been precised. Various parameters (L and D, or L and DL mixtures, dissolution in water before sublimation, . . . ) were studied. We also took into consideration the recently proposed hypothesis of the role played by the eutectic ee in the sublimation. [4] The application of these results to find an explanation of the enantiomeric excess in meteorites or in the Primitive Earth scenarios will be discussed. 1 Pasteur, L. Ann. Phys., 1848, 24, 442. 2 R. H. Perry, C. Wu, M. Nefliu, R. G. Cooks, Chem. Commun., 2007, 1071-1073. 3 S. P. Fletcher, R. B. C. Jagt, B. L. Feringa, Chem. Commun., 2007, 2578-2580. 4 D. G. Blackmond, M. Klussmannb Chem. Commun., 2007, 3990-3996.

  18. Aerosol volatility and enthalpy of sublimation of carboxylic acids.

    PubMed

    Salo, Kent; Jonsson, Asa M; Andersson, Patrik U; Hallquist, Mattias

    2010-04-08

    The enthalpy of sublimation has been determined for nine carboxylic acids, two cyclic (pinonic and pinic acid) and seven straight-chain dicarboxylic acids (C(4) to C(10)). The enthalpy of sublimation was determined from volatility measurements of nano aerosol particles using a volatility tandem differential mobility analyzer (VTDMA) set-up. Compared to the previous use of a VTDMA, this novel method gives enthalpy of sublimation determined over an extended temperature range (DeltaT approximately 40 K). The determined enthalpy of sublimation for the straight-chain dicarboxylic acids ranged from 96 to 161 kJ mol(-1), and the calculated vapor pressures at 298 K are in the range of 10(-6)-10(-3) Pa. These values indicate that dicarboxylic acids can take part in gas-to-particle partitioning at ambient conditions and may contribute to atmospheric nucleation, even though homogeneous nucleation is unlikely. To obtain consistent results, some experimental complications in producing nanosized crystalline aerosol particles were addressed. It was demonstrated that pinonic acid "used as received" needed a further purification step before being suspended as a nanoparticle aerosol. Furthermore, it was noted from distinct differences in thermal properties that aerosols generated from pimelic acid solutions gave two types of particles. These two types were attributed to crystalline and amorphous configurations, and based on measured thermal properties, the enthalpy of vaporization was 127 kJ mol(-1) and that of sublimation was 161 kJ mol(-1). This paper describes a new method that is complementary to other similar methods and provides an extension of existing experimental data on physical properties of atmospherically relevant compounds.

  19. Advances in sublimation studies for particles of explosives

    NASA Astrophysics Data System (ADS)

    Furstenberg, Robert; Nguyen, Viet; Fischer, Thomas; Abrishami, Tara; Papantonakis, Michael; Kendziora, Chris; Mott, David R.; McGill, R. Andrew

    2015-05-01

    When handling explosives, or related surfaces, the hands routinely become contaminated with particles of explosives and related materials. Subsequent contact with a solid surface results in particle crushing and deposition. These particles provide an evidentiary trail which is useful for security applications. As such, the opto-physico-chemical characteristics of these particles are critical to trace explosives detection applications in DOD or DHS arenas. As the persistence of these particles is vital to their forensic exploitation, it is important to understand which factors influence their persistence. The longevity or stability of explosives particles on a substrate is a function of several environmental parameters or particle properties including: Vapor pressure, particle geometry, airflow, particle field size, substrate topography, humidity, reactivity, adlayers, admixtures, particle areal density, and temperature. In this work we deposited particles of 2,4-dinitrotoluene on standard microscopy glass slides by particle sieving and studied their sublimation as a function of airflow velocity, areal particle density and particle field size. Analysis of 2D microscopic images was used to compute and track particle size and geometrical characteristics. The humidity, temperature and substrate type were kept constant for each experiment. A custom airflow cell, using standard microscopy glass slide, allowed in-situ photomicroscopy. Areal particle densities and airflow velocities were selected to provide relevant loadings and flow velocities for a range of potential applications. For a chemical of interest, we define the radial sublimation velocity (RSV) for the equivalent sphere of a particle as the parameter to characterize the sublimation rate. The RSV is a useful parameter because it is independent of particle size. The sublimation rate for an ensemble of particles was found to significantly depend on airflow velocity, the areal density of the particles, and the

  20. Piezoelectric crystal microbalance measurements of enthalpy of sublimation of C2-C9 dicarboxylic acids

    NASA Astrophysics Data System (ADS)

    Dirri, F.; Palomba, E.; Longobardo, A.; Zampetti, E.

    2016-02-01

    We present here a novel experimental set-up that is able to measure the enthalpy of sublimation of a given compound by means of piezoelectric crystal microbalances (PCMs). The PCM sensors have already been used for space measurements, such as for the detection of organic and non-organic volatile species and refractory materials in planetary environments. In Earth atmospherics applications, PCMs can be also used to obtain some physical-chemical processes concerning the volatile organic compounds (VOCs) present in atmospheric environments. The experimental set-up has been developed and tested on dicarboxylic acids. In this work, a temperature-controlled effusion cell was used to sublimate VOC, creating a molecular flux that was collimated onto a cold PCM. The VOC recondensed onto the PCM quartz crystal, allowing the determination of the deposition rate. From the measurements of deposition rates, it has been possible to infer the enthalpy of sublimation of adipic acid, i.e. ΔHsub : 141.6 ± 0.8 kJ mol-1, succinic acid, i.e. 113.3 ± 1.3 kJ mol-1, oxalic acid, i.e. 62.5 ± 3.1 kJ mol-1, and azelaic acid, i.e. 124.2 ± 1.2 kJ mol-1. The results obtained show an accuracy of 1 % for succinic, adipic, and azelaic acid and within 5 % for oxalic acid and are in very good agreement with previous works (within 6 % for adipic, succinic, and oxalic acid and within 11 % or larger for azelaic acid).

  1. Piezoelectric crystal microbalance measurements of enthalpy of sublimation of C2-C9 dicarboxylic acids

    NASA Astrophysics Data System (ADS)

    Dirri, F.; Palomba, E.; Longobardo, A.; Zampetti, E.

    2015-07-01

    We present here a novel experimental setup able to measure the enthalpy of sublimation of a given compound by means of Piezoelectric Crystal Microbalances (PCM). This experiment was performed in the TG-Lab facility in IAPS-INAF, dedicated to the development of TGA sensors for space measurements, such as detection of organic and non-organic volatile species and refractory materials in planetary environments. In order to study physical-chemical processes concerning the Volatile Organic Compounds (VOC) present in atmospheric environments, the setup has been tested on Dicarboxylic acids. Acids with low molecular weight are among the components of organic fraction of particulate matter in the atmosphere, coming from different sources (biogenic and anthropogenic). Considering their relative abundance, it is useful to consider Dicarboxylic acid as "markers" to define the biogenic or anthropogenic origin of the aerosol, thus obtaining some information of the emission sources. In this work, a temperature controlled effusion cell was used to sublimate VOC, creating a molecular flux that was collimated onto a cold PCM. The VOC re-condensed onto the PCM quartz crystal allowing the determination of the deposition rate. From the measurements of deposition rates, it was possible to infer the enthalpy of sublimation of Adipic acid, i.e. Δ Hsub: 141.6 ± 0.8 kJ mol-1, Succinic acid, i.e. 113.3 ± 1.3 kJ mol-1, Oxalic acid, i.e. 62.5 ± 3.1 kJ mol-1 and Azelaic acid, i.e. 124.2 ± 1.2 kJ mol-1 (weight average values). The results obtained are in very good agreement with literature within 10 % for the Adipic, Succinic and Oxalic acid.

  2. Sublimation-driven erosion on Hyperion: Topographic analysis and landform simulation model tests

    NASA Astrophysics Data System (ADS)

    Howard, Alan D.; Moore, Jeffrey M.; Schenk, Paul M.; White, Oliver L.; Spencer, John

    2012-07-01

    The unique appearance of Hyperion can be explained in part by the loss to space of ballistic ejecta during impact events, as was proposed by Thomas et al. (Thomas, P.C. et al. [2007a]. Icarus 190, 573-584). We conclude that such loss is a partial explanation, accounting for the lack of appreciable intercrater plains on a saturation-cratered surface. In order to create the smooth surfaces and the reticulate, honeycomb pattern of narrow divides between old craters, appreciable subsequent modification of crater morphology must occur through mass-wasting processes accompanied by sublimation, probably facilitated by the loss of CO2 as a component of the relief-supporting matrix of the bedrock. During early stages of crater degradation, steep, crenulate bedrock slopes occupy the upper crater walls with abrupt transitions downslope onto smooth slopes near the angle of repose mantled by mass wasting debris, as can be seen within young craters. Long-continued mass wasting eventually results in slopes totally mantled with particulate debris. This mass wasting effectively destroys small craters, at least in part accounting for the paucity of sub-kilometer craters on Hyperion. Surface temperatures measured by Cassini CIRS range from 58 K to 127 K and imply a surface thermal inertia of 11 ± 2 J m-2 K-1 s-1/2 and bolometric albedo ranging from 0.05 to 0.33. Resulting H2O sublimation rates are only tens of cm per billion years for most of the surface, so the evolution of the observed landforms is likely to require sublimation of more volatile species such as CO2.

  3. Generalized separable parameter space techniques for fitting 1K-5K serial compartment models

    PubMed Central

    Kadrmas, Dan J.; Oktay, M. Bugrahan

    2013-01-01

    Purpose: Kinetic modeling is widely used to analyze dynamic imaging data, estimating kinetic parameters that quantify functional or physiologic processes in vivo. Typical kinetic models give rise to nonlinear solution equations in multiple dimensions, presenting a complex fitting environment. This work generalizes previously described separable nonlinear least-squares techniques for fitting serial compartment models with up to three tissue compartments and five rate parameters. Methods: The approach maximally separates the linear and nonlinear aspects of the modeling equations, using a formulation modified from previous basis function methods to avoid a potential mathematical degeneracy. A fast and robust algorithm for solving the linear subproblem with full user-defined constraints is also presented. The generalized separable parameter space technique effectively reduces the dimensionality of the nonlinear fitting problem to one dimension for 2K-3K compartment models, and to two dimensions for 4K-5K models. Results: Exhaustive search fits, which guarantee identification of the true global minimum fit, required approximately 10 ms for 2K-3K and 1.1 s for 4K-5K models, respectively. The technique is also amenable to fast gradient-descent iterative fitting algorithms, where the reduced dimensionality offers improved convergence properties. The objective function for the separable parameter space nonlinear subproblem was characterized and found to be generally well-behaved with a well-defined global minimum. Separable parameter space fits with the Levenberg-Marquardt algorithm required fewer iterations than comparable fits for conventional model formulations, averaging 1 and 7 ms for 2K-3K and 4K-5K models, respectively. Sensitivity to initial conditions was likewise reduced. Conclusions: The separable parameter space techniques described herein generalize previously described techniques to encompass 1K-5K compartment models, enable robust solution of the linear

  4. Generalized separable parameter space techniques for fitting 1K-5K serial compartment models.

    PubMed

    Kadrmas, Dan J; Oktay, M Bugrahan

    2013-07-01

    Kinetic modeling is widely used to analyze dynamic imaging data, estimating kinetic parameters that quantify functional or physiologic processes in vivo. Typical kinetic models give rise to nonlinear solution equations in multiple dimensions, presenting a complex fitting environment. This work generalizes previously described separable nonlinear least-squares techniques for fitting serial compartment models with up to three tissue compartments and five rate parameters. The approach maximally separates the linear and nonlinear aspects of the modeling equations, using a formulation modified from previous basis function methods to avoid a potential mathematical degeneracy. A fast and robust algorithm for solving the linear subproblem with full user-defined constraints is also presented. The generalized separable parameter space technique effectively reduces the dimensionality of the nonlinear fitting problem to one dimension for 2K-3K compartment models, and to two dimensions for 4K-5K models. Exhaustive search fits, which guarantee identification of the true global minimum fit, required approximately 10 ms for 2K-3K and 1.1 s for 4K-5K models, respectively. The technique is also amenable to fast gradient-descent iterative fitting algorithms, where the reduced dimensionality offers improved convergence properties. The objective function for the separable parameter space nonlinear subproblem was characterized and found to be generally well-behaved with a well-defined global minimum. Separable parameter space fits with the Levenberg-Marquardt algorithm required fewer iterations than comparable fits for conventional model formulations, averaging 1 and 7 ms for 2K-3K and 4K-5K models, respectively. Sensitivity to initial conditions was likewise reduced. The separable parameter space techniques described herein generalize previously described techniques to encompass 1K-5K compartment models, enable robust solution of the linear subproblem with full user-defined constraints

  5. Use of reduced basis technique in the inverse dynamics of large space cranes

    NASA Technical Reports Server (NTRS)

    Das, S. K.; Utku, S.; Wada, B. K.

    1990-01-01

    The inverse dynamics of adaptive structures used as space cranes can prove computationally expensive in the case of large structures, due to the large number of degrees of freedom involved. Consequently, reduced basis techniques (reduction techniques) are frequently used to reduce the problem size to a time manageable level (for possible use in real time control). A reduced basis technique is proposed which is different from, but related to, the path-derivatives reduction technique. A linearly independent set of deflection n-tuples is used, chosen at the beginning of the time range in which it is wished to reduce the equations, in whose subspace it is assumed that the deflection vectors of the unreduced problem will lie (approximately).

  6. Evaluation of nondestructive testing techniques for the space shuttle nonmetallic thermal protection system

    NASA Technical Reports Server (NTRS)

    Tiede, D. A.

    1972-01-01

    A program was conducted to evaluate nondestructive analysis techniques for the detection of defects in rigidized surface insulation (a candidate material for the Space Shuttle thermal protection system). Uncoated, coated, and coated and bonded samples with internal defects (voids, cracks, delaminations, density variations, and moisture content), coating defects (holes, cracks, thickness variations, and loss of adhesion), and bondline defects (voids and unbonds) were inspected by X-ray radiography, acoustic, microwave, high-frequency ultrasonic, beta backscatter, thermal, holographic, and visual techniques. The detectability of each type of defect was determined for each technique (when applicable). A possible relationship between microwave reflection measurements (or X-ray-radiography density measurements) and the tensile strength was established. A possible approach for in-process inspection using a combination of X-ray radiography, acoustic, microwave, and holographic techniques was recommended.

  7. Laparoscopic nerve-sparing radical hysterectomy with fascia space dissection technique for cervical cancer: description of technique and outcomes.

    PubMed

    Liang, Zhiqing; Chen, Yong; Xu, Huicheng; Li, Yuyan; Wang, Dan

    2010-11-01

    The objectives of this study were to describe our laparoscopic nerve-sparing radical hysterectomy (LNSRH) technique and to assess the feasibility and safety of the procedure, as well as its impact on voiding function. We introduce a fascia space dissection technique in order to preserve the pelvic splanchnic nerve, the hypogastric nerve and the bladder branch of the inferior hypogastric plexus under magnification (×10.5) during laparoscopic radical hysterectomy (LRH) with pelvic lymphadenectomy. From October 2006 to November 2009, 163 consecutive patients with cervical cancer underwent laparoscopic radical hysterectomy (LRH) and pelvic lymphadenectomy, with 82 women undergoing LNSRH with fascia space dissection technique (LNSRH group) and 81 undergoing LRH (LRH group). Data from 163 patients were prospectively collected and compared. Post-operative assessment of bladder function included the following: the time to recover the ability to void spontaneously and to achieve a post-void residual urine (PVR) volume of less than 50 ml, with urination function graded. The laparoscopic nerve-sparing radical hysterectomy procedure was completed successfully and was conducted safely in all of the patients. There were no conversions to open surgery in the two groups. The median operative duration in the LNSRH and the LRH groups were 163.52±34.47 min and 132.13±31.42 min, respectively. Blood loss was 142.12±62.38 ml and 187.69±68.63 ml, respectively. The time taken to obtain a post-void residual urine volume of less than 50 ml after removal of the urethral catheter was 7.42±2.35 d (5-18 d) in LNSRH group and was 16.75±7.73 d (5-35 d) in LRH group (P<0.05). The bladder void function recovery to Grades 0-I was 76 (92.7%) for the LNSRH group and 59 (72.8%) for the LRH group. A mean follow-up of 22.3 (5-42) months was adhered to, and no patient had a recurrence or metastasis. The technique described in this preliminary study appears to be safe, feasible, and easy in our

  8. Application Of Metric Space Technique (mst) In 2-d And 3-d To Sdss Dr5

    NASA Astrophysics Data System (ADS)

    Wu, Yongfeng; Batuski, D. J.; Khalil, A.

    2009-01-01

    The Metric Space Technique (MST) is a 2-D analysis method using multiple measures for quantitative analysis of any type of structure in an `image'. All potential values of the measures for such distributions are thus coordinates in a multi-parameter space, and the analysis is based on considering a sample's measures (called `output functions'), and their distance from the origin, which corresponds to the measures of the observed SDSS sample, in this multi-parameter space. Applications of this method to thin (approximately 2-D) slices of SDSS DR5 have yielded a detailed comparison of numerical models (Berlind et al. 2006, Croton et al. 2005) against the SDSS galaxy 2-D distribution structure in multi-parameter space. We present those results, including discussion of the effects of transforming from physical space to redshift space on the statistics at different scales. We also extended this 2-D method into 3-D, and we present comparisons of the SDSS galaxy 3-D distribution versus the same numerical simulations.

  9. A Real-Time High Performance Data Compression Technique For Space Applications

    NASA Technical Reports Server (NTRS)

    Yeh, Pen-Shu; Venbrux, Jack; Bhatia, Prakash; Miller, Warner H.

    2000-01-01

    A high performance lossy data compression technique is currently being developed for space science applications under the requirement of high-speed push-broom scanning. The technique is also error-resilient in that error propagation is contained within a few scan lines. The algorithm is based on block-transform combined with bit-plane encoding; this combination results in an embedded bit string with exactly the desirable compression rate. The lossy coder is described. The compression scheme performs well on a suite of test images typical of images from spacecraft instruments. Hardware implementations are in development; a functional chip set is expected by the end of 2001.

  10. Application of Satellite Laser Ranging Techniques for Space Situational Awareness Efforts

    NASA Astrophysics Data System (ADS)

    Shappirio, M.; McGarry, J. F.; Bufton, J.; Cheek, J. W.; Coyle, D. B.; Hull, S. M.; Stysley, P. R.; Sun, X.; Young, R. P.; Zagwodzki, T.

    2016-09-01

    With the numbers of conjunction avoidance maneuvers for the International Space Station and other Low Earth Orbit satellites rising and likely to continue to increase, the need to develop methods to produce accurate 72+ hour orbital predictions is becoming critical. One emerging solution is to utilize satellite laser ranging techniques to range to debris and refine the initial positions to improve the orbital predictions for objects predicted to experience a close approach. Some stations in Europe have already demonstrated that this technique is possible, but it has not been employed to refine the likelihood of collision. We will present a notional architecture for laser ranging to debris utilizing existing satellite laser ranging or visual tracking facilities. We will also discuss the capabilities of laser ranging for Space Situational Awareness and provide a direct comparison to current visual and radar tracking methods.

  11. General-Purpose Stereo Imaging Velocimetry Technique Developed for Space and Industrial Applications

    NASA Technical Reports Server (NTRS)

    McDowell, Mark

    2004-01-01

    A new three-dimensional, full-field analysis technique has been developed for industrial and space applications. Stereo Imaging Velocimetry (SIV) will provide full-field analysis for three-dimensional flow data from any optically transparent fluid that can be seeded with tracer particles. The goal of SIV is to provide a means to measure three-dimensional fluid velocities quantitatively and qualitatively at many points. SIV is applicable to any optically transparent fluid experiment. Except for the tracer particles, this measurement technique is nonintrusive. Velocity accuracies are on the order of 95 to 99 percent of fullfield. The system components of SIV include camera calibration, centroid determination, overlap decomposition, particle tracking, stereo matching, and three-dimensional velocity analysis. SIV has been used successfully for space shuttle experiments as well as for fluid flow applications for business and industry.

  12. Measuring Enthalpy of Sublimation of Volatiles by Means of Piezoelectric Crystal Microbalances.

    PubMed

    Dirri, Fabrizio; Palomba, Ernesto; Longobardo, Andrea; Zampetti, Emiliano

    2016-09-15

    Piezoelectric Crystal Microbalances (PCM's) are widely used to study the chemical processes involving volatile compounds in any environment, such as condensation process. Since PCM's are miniaturized sensor, they are very suitable for planetary in situ missions, where can be used to detect and to measure the mass amount of astrobiologically significant compounds, such as water and organics. This work focuses on the realization and testing of a new experimental setup, able to characterize volatiles which can be found in a planetary environment. In particular the enthalpy of sublimation of some dicarboxylic acids has been measured. The importance of dicarboxylic acids in planetology and astrobiology is due to the fact that they have been detected in carbonaceous chondritic material (e.g. Murchinson), among the most pristine material present in our Solar System. In this work, a sample of acid was heated in an effusion cell up to its sublimation. For a set of temperatures (from 30 °C to 75 °C), the deposition rate on the PCM surface has been measured. From these measurements, it has been possible to infer the enthalpy of sublimation of Adipic acid, i.e. ΔH = 141.6 ± 0.8 kJ/mol and Succinic acid, i.e. ΔH = 113.3 ± 1.3 kJ/mol. This technique has so demonstrated to be a good choice to recognise a single compound or a mixture (with an analysis upstream) even if some improvements concerning the thermal stabilization of the system will be implemented in order to enhance the results' accuracy. The experiment has been performed in support of the VISTA (Volatile In Situ Thermogravimetry Analyzer) project, which is included in the scientific payload of the ESA MarcoPolo-R mission study.

  13. Measuring Enthalpy of Sublimation of Volatiles by Means of Piezoelectric Crystal Microbalances

    NASA Astrophysics Data System (ADS)

    Dirri, Fabrizio; Palomba, Ernesto; Longobardo, Andrea; Zampetti, Emiliano

    2016-09-01

    Piezoelectric Crystal Microbalances (PCM's) are widely used to study the chemical processes involving volatile compounds in any environment, such as condensation process. Since PCM's are miniaturized sensor, they are very suitable for planetary in situ missions, where can be used to detect and to measure the mass amount of astrobiologically significant compounds, such as water and organics. This work focuses on the realization and testing of a new experimental setup, able to characterize volatiles which can be found in a planetary environment. In particular the enthalpy of sublimation of some dicarboxylic acids has been measured. The importance of dicarboxylic acids in planetology and astrobiology is due to the fact that they have been detected in carbonaceous chondritic material (e.g. Murchinson), among the most pristine material present in our Solar System. In this work, a sample of acid was heated in an effusion cell up to its sublimation. For a set of temperatures (from 30 °C to 75 °C), the deposition rate on the PCM surface has been measured. From these measurements, it has been possible to infer the enthalpy of sublimation of Adipic acid, i.e. ΔH = 141.6 ± 0.8 kJ/mol and Succinic acid, i.e. ΔH = 113.3 ± 1.3 kJ/mol. This technique has so demonstrated to be a good choice to recognise a single compound or a mixture (with an analysis upstream) even if some improvements concerning the thermal stabilization of the system will be implemented in order to enhance the results' accuracy. The experiment has been performed in support of the VISTA (Volatile In Situ Thermogravimetry Analyzer) project, which is included in the scientific payload of the ESA MarcoPolo-R mission study.

  14. Advanced techniques for free-space optical quantum cryptography over water

    NASA Astrophysics Data System (ADS)

    Hill, Alexander D.; Christensen, Bradley; Kwiat, Paul G.

    2016-03-01

    Free-space quantum key distribution (QKD) over water (e.g., ship to ship) may be limited by ship motion and atmospheric effects, such as mode distortion and beam wander due to turbulence. We report on a technique which reduces noise by excluding spatial modes which are less likely to contain QKD signal photons and experimentally demonstrate an improvement in QKD key generation rates in various noise and turbulence regimes.

  15. Coarse-Grain Bandwidth Estimation Techniques for Large-Scale Space Network

    NASA Technical Reports Server (NTRS)

    Cheung, Kar-Ming; Jennings, Esther

    2013-01-01

    In this paper, we describe a top-down analysis and simulation approach to size the bandwidths of a store-andforward network for a given network topology, a mission traffic scenario, and a set of data types with different latency requirements. We use these techniques to estimate the wide area network (WAN) bandwidths of the ground links for different architecture options of the proposed Integrated Space Communication and Navigation (SCaN) Network.

  16. Subjective refraction techniques in the frame of the three-dimensional dioptric space.

    PubMed

    Muñoz-Escrivá, L; Furlan, W D

    2001-02-01

    A novel heuristic approach to the well-known representation of the dioptric power in a three-dimensional space is presented. It is shown how this theoretical framework is ideal for discussing the principles of several subjective refraction methods. In particular, this formalism is used to justify the stenopaic slit refraction, the Barnes subjective refraction technique, and the Jackson cross-cylinder procedure. In view of this analysis, some modifications to the traditional procedures are proposed.

  17. A Summary of the International Workshops on Space Solar Cell Calibration and Measurement Techniques

    NASA Technical Reports Server (NTRS)

    Brinker, D. J.; Curtis, H. B.; Flood, D. J.; Jenkins, P.; Scheiman, D. A.

    1995-01-01

    The first two of a planned series of international workshops concerning space solar cell calibration and measurement techniques have been held within the past year. The need for these workshops arose from the increasing complexity of space solar cells coupled with the growing international nature of the market for space cells and arrays. The workshops, jointly sponsored by NASDA, ESA and NASA, have the objective of obtaining international agreement on standardized values for the AM0 spectrum and constant, recommendations for laboratory measurement practices and the establishment of a set of protocols for making interlaboratory comparison measurements. The results of the first two workshops, held in Waikiki, Hawaii, USA in 1994 and Madrid, Spain in 1995, are presented.

  18. Measurements of strain at plate boundaries using space based geodetic techniques

    NASA Technical Reports Server (NTRS)

    Robaudo, Stefano; Harrison, Christopher G. A.

    1993-01-01

    We have used the space based geodetic techniques of Satellite Laser Ranging (SLR) and VLBI to study strain along subduction and transform plate boundaries and have interpreted the results using a simple elastic dislocation model. Six stations located behind island arcs were analyzed as representative of subduction zones while 13 sites located on either side of the San Andreas fault were used for the transcurrent zones. The length deformation scale was then calculated for both tectonic margins by fitting the relative strain to an exponentially decreasing function of distance from the plate boundary. Results show that space-based data for the transcurrent boundary along the San Andreas fault help to define better the deformation length scale in the area while fitting nicely the elastic half-space earth model. For subduction type bonndaries the analysis indicates that there is no single scale length which uniquely describes the deformation. This is mainly due to the difference in subduction characteristics for the different areas.

  19. Acoustic levitation technique for containerless processing at high temperatures in space

    NASA Technical Reports Server (NTRS)

    Rey, Charles A.; Merkley, Dennis R.; Hammarlund, Gregory R.; Danley, Thomas J.

    1988-01-01

    High temperature processing of a small specimen without a container has been demonstrated in a set of experiments using an acoustic levitation furnace in the microgravity of space. This processing technique includes the positioning, heating, melting, cooling, and solidification of a material supported without physical contact with container or other surface. The specimen is supported in a potential energy well, created by an acoustic field, which is sufficiently strong to position the specimen in the microgravity environment of space. This containerless processing apparatus has been successfully tested on the Space Shuttle during the STS-61A mission. In that experiment, three samples wer successfully levitated and processed at temperatures from 600 to 1500 C. Experiment data and results are presented.

  20. Utilization of artificial intelligence techniques for the Space Station power system

    NASA Technical Reports Server (NTRS)

    Evatt, Thomas C.; Gholdston, Edward W.

    1988-01-01

    Due to the complexity of the Space Station Electrical Power System (EPS) as currently envisioned, artificial intelligence/expert system techniques are being investigated to automate operations, maintenance, and diagnostic functions. A study was conducted to investigate this technology as it applies to failure detection, isolation, and reconfiguration (FDIR) and health monitoring of power system components and of the total system. Control system utilization of expert systems for load scheduling and shedding operations was also researched. A discussion of the utilization of artificial intelligence/expert systems for Initial Operating Capability (IOC) for the Space Station effort is presented along with future plans at Rocketdyne for the utilization of this technology for enhanced Space Station power capability.

  1. Utilization of artificial intelligence techniques for the Space Station power system

    NASA Technical Reports Server (NTRS)

    Evatt, Thomas C.; Gholdston, Edward W.

    1988-01-01

    Due to the complexity of the Space Station Electrical Power System (EPS) as currently envisioned, artificial intelligence/expert system techniques are being investigated to automate operations, maintenance, and diagnostic functions. A study was conducted to investigate this technology as it applies to failure detection, isolation, and reconfiguration (FDIR) and health monitoring of power system components and of the total system. Control system utilization of expert systems for load scheduling and shedding operations was also researched. A discussion of the utilization of artificial intelligence/expert systems for Initial Operating Capability (IOC) for the Space Station effort is presented along with future plans at Rocketdyne for the utilization of this technology for enhanced Space Station power capability.

  2. Coordinate space translation technique for simulation of electronic process in the ion-atom collision.

    PubMed

    Wang, Feng; Hong, Xuhai; Wang, Jian; Kim, Kwang S

    2011-04-21

    Recently we developed a theoretical model of ion-atom collisions, which was made on the basis of a time-dependent density functional theory description of the electron dynamics and a classical treatment of the heavy particle motion. Taking advantage of the real-space grid method, we introduce a "coordinate space translation" technique to allow one to focus on a certain space of interest such as the region around the projectile or the target. Benchmark calculations are given for collisions between proton and oxygen over a wide range of impact energy. To extract the probability of charge transfer, the formulation of Lüdde and Dreizler [J. Phys. B 16, 3973 (1983)] has been generalized to ensemble-averaging application in the particular case of O((3)P). Charge transfer total cross sections are calculated, showing fairly good agreements between experimental data and present theoretical results.

  3. Coordinate space translation technique for simulation of electronic process in the ion-atom collision

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Hong, Xuhai; Wang, Jian; Kim, Kwang S.

    2011-04-01

    Recently we developed a theoretical model of ion-atom collisions, which was made on the basis of a time-dependent density functional theory description of the electron dynamics and a classical treatment of the heavy particle motion. Taking advantage of the real-space grid method, we introduce a "coordinate space translation" technique to allow one to focus on a certain space of interest such as the region around the projectile or the target. Benchmark calculations are given for collisions between proton and oxygen over a wide range of impact energy. To extract the probability of charge transfer, the formulation of Lüdde and Dreizler [J. Phys. B 16, 3973 (1983)] has been generalized to ensemble-averaging application in the particular case of O(3P). Charge transfer total cross sections are calculated, showing fairly good agreements between experimental data and present theoretical results.

  4. A Summary of the International Workshops on Space Solar Cell Calibration and Measurement Techniques

    NASA Technical Reports Server (NTRS)

    Brinker, D. J.; Curtis, H. B.; Flood, D. J.; Jenkins, P.; Scheiman, D. A.

    1995-01-01

    The first two of a planned series of international workshops concerning space solar cell calibration and measurement techniques have been held within the past year. The need for these workshops arose from the increasing complexity of space solar cells coupled with the growing international nature of the market for space cells and arrays. The workshops, jointly sponsored by NASDA, ESA and NASA, have the objective of obtaining international agreement on standardized values for the AM0 spectrum and constant, recommendations for laboratory measurement practices and the establishment of a set of protocols for making interlaboratory comparison measurements. The results of the first two workshops, held in Waikiki, Hawaii, USA in 1994 and Madrid, Spain in 1995, are presented.

  5. Acoustic levitation technique for containerless processing at high temperatures in space

    NASA Technical Reports Server (NTRS)

    Rey, Charles A.; Merkley, Dennis R.; Hammarlund, Gregory R.; Danley, Thomas J.

    1988-01-01

    High temperature processing of a small specimen without a container has been demonstrated in a set of experiments using an acoustic levitation furnace in the microgravity of space. This processing technique includes the positioning, heating, melting, cooling, and solidification of a material supported without physical contact with container or other surface. The specimen is supported in a potential energy well, created by an acoustic field, which is sufficiently strong to position the specimen in the microgravity environment of space. This containerless processing apparatus has been successfully tested on the Space Shuttle during the STS-61A mission. In that experiment, three samples wer successfully levitated and processed at temperatures from 600 to 1500 C. Experiment data and results are presented.

  6. Computer Vision Techniques Applied to Space Object Detect, Track, ID, Characterize

    NASA Astrophysics Data System (ADS)

    Flewelling, B.

    2014-09-01

    Space-based object detection and tracking represents a fundamental step necessary for detailed analysis of space objects. Initial observations of a resident space object (RSO) may result from careful sensor tasking to observe an object with well understood dynamics, or measurements-of-opportunity on an object with poorly understood dynamics. Dim and eccentric objects present a particular challenge which requires more dynamic use of imaging systems. As a result of more stressing data acquisition strategies, advanced techniques for the accurate processing of both point and streaking sources are needed. This paper will focus on two key methods in computer vision used to determine interest points within imagery. The Harris Corner method and the method of Phase Congruency can be used to effectively extract static and streaking point sources and to indicate when apparent motion is present within an observation. The geometric inferences which can be made from the resulting detections will be discussed, including a method to evaluate the localization uncertainty of the extracted detections which is based on the computation of the Hessian of the detector response. Finally a technique which exploits the additional information found in detected streak endpoints to provide a better centroid in the presence of curved streaks is explained and additional applications for the presented techniques are discussed.

  7. On the estimation of the current density in space plasmas: Multi- versus single-point techniques

    NASA Astrophysics Data System (ADS)

    Perri, Silvia; Valentini, Francesco; Sorriso-Valvo, Luca; Reda, Antonio; Malara, Francesco

    2017-06-01

    Thanks to multi-spacecraft mission, it has recently been possible to directly estimate the current density in space plasmas, by using magnetic field time series from four satellites flying in a quasi perfect tetrahedron configuration. The technique developed, commonly called ;curlometer; permits a good estimation of the current density when the magnetic field time series vary linearly in space. This approximation is generally valid for small spacecraft separation. The recent space missions Cluster and Magnetospheric Multiscale (MMS) have provided high resolution measurements with inter-spacecraft separation up to 100 km and 10 km, respectively. The former scale corresponds to the proton gyroradius/ion skin depth in ;typical; solar wind conditions, while the latter to sub-proton scale. However, some works have highlighted an underestimation of the current density via the curlometer technique with respect to the current computed directly from the velocity distribution functions, measured at sub-proton scales resolution with MMS. In this paper we explore the limit of the curlometer technique studying synthetic data sets associated to a cluster of four artificial satellites allowed to fly in a static turbulent field, spanning a wide range of relative separation. This study tries to address the relative importance of measuring plasma moments at very high resolution from a single spacecraft with respect to the multi-spacecraft missions in the current density evaluation.

  8. Acoustic puncture assist device versus loss of resistance technique for epidural space identification.

    PubMed

    Mittal, Amit Kumar; Goel, Nitesh; Chowdhury, Itee; Shah, Shagun Bhatia; Singh, Brijesh Pratap; Jakhar, Pradeep

    2016-05-01

    The conventional techniques of epidural space (EDS) identification based on loss of resistance (LOR) have a higher chance of complications, patchy analgesia and epidural failure, which can be minimised by objective confirmation of space before catheter placement. Acoustic puncture assist device (APAD) technique objectively confirms EDS, thus enhancing success, with lesser complications. This study was planned with the objective to evaluate the APAD technique and compare it to LOR technique for EDS identification and its correlation with ultrasound guided EDS depth. In this prospective study, the lumbar vertebral spaces were scanned by the ultrasound for measuring depth of the EDS and later correlated with procedural depth measured by either of the technique (APAD or LOR). The data were subjected to descriptive statistics; the concordance correlation coefficient and Bland-Altman analysis with 95% confidence limits. Acoustic dip in pitch and descent in pressure tracing on EDS localisation was observed among the patients of APAD group. Analysis of concordance correlation between the ultrasonography (USG) depth and APAD or LOR depth was significant (r ≥ 0.97 in both groups). Bland-Altman analysis revealed a mean difference of 0.171cm in group APAD and 0.154 cm in group LOR. The 95% limits of agreement for the difference between the two measurements were - 0.569 and 0.226 cm in APAD and - 0.530 to 0.222 cm in LOR group. We found APAD to be a precise tool for objective localisation of the EDS, co-relating well with the pre-procedural USG depth of EDS.

  9. Sublimation's impact on temporal change of albedo dichotomy on Iapetus

    NASA Astrophysics Data System (ADS)

    Kimura, Jun; Kawamura, Taichi; Morito, Hisataka; Morota, Tomokatsu; Honda, Chikatoshi; Kuramoto, Kiyoshi; Okada, Tatsuaki

    2011-08-01

    Iapetus, one of the saturnian moons, has an extreme albedo contrast between the leading and trailing hemispheres. The origin of this albedo dichotomy has led to several hypotheses, however it remains controversial. To clarify the origin of the dichotomy, the key approach is to investigate the detailed distribution of the dark material. Recent studies of impact craters and surface temperature from Cassini spacecraft data implied that sublimation of H 2O ice can occur on Iapetus' surface. This ice sublimation can change the albedo distribution on the moon with time. In this study, we evaluate the effect of ice sublimation and simulate the temporal change of surface albedo. We assume the dark material and the bright ice on the surface to be uniformly mixed with a certain volume fraction, and the initial albedo distribution to incorporate the dark material deposits on the surface. That is, the albedo at the apex is lowest and concentrically increases in a sinusoidal pattern. This situation simulates that dark materials existed around the Iapetus' orbit billions of years ago, and the synchronously rotating Iapetus swept the material and then deposited it on its surface. The evolution of the surface albedo during 4.0 Gyr is simulated by estimating the surface temperature from the insolation energy on Iapetus including the effect of Saturn's eccentricity and Iapetus' obliquity precession, and evaluating the sublimation rate of H 2O ice from the Iapetus' surface. As a result, we found that the distribution of the surface albedo changed dramatically after 4.0 Gyr of evolution. The sublimation has three important effects on the resultant surface albedo. First, the albedo in the leading hemisphere has significantly decreased to approach the minimum value. Second, the albedo distribution has been elongated along the equator. Third, the edge of the low albedo region has become clear. Considering the effect of ice sublimation, the current albedo distribution can be reconstructed

  10. Characterization of Carbon Dioxide Washout Measurement Techniques in the Mark-III Space Suit

    NASA Technical Reports Server (NTRS)

    Meginnis, I; Norcross, J.; Bekdash, O.

    2016-01-01

    techniques for future CO2 washout limits in space suits

  11. Application of separable parameter space techniques to multi-tracer PET compartment modeling

    PubMed Central

    Zhang, Jeff L; Morey, A Michael; Kadrmas, Dan J

    2016-01-01

    Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg–Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models. PMID:26788888

  12. Demonstration of a High-Fidelity Predictive/Preview Display Technique for Telerobotic Servicing in Space

    NASA Technical Reports Server (NTRS)

    Kim, Won S.; Bejczy, Antal K.

    1993-01-01

    A highly effective predictive/preview display technique for telerobotic servicing in space under several seconds communication time delay has been demonstrated on a large laboratory scale in May 1993, involving the Jet Propulsion Laboratory as the simulated ground control station and, 2500 miles away, the Goddard Space Flight Center as the simulated satellite servicing set-up. The technique is based on a high-fidelity calibration procedure that enables a high-fidelity overlay of 3-D graphics robot arm and object models over given 2-D TV camera images of robot arm and objects. To generate robot arm motions, the operator can confidently interact in real time with the graphics models of the robot arm and objects overlaid on an actual camera view of the remote work site. The technique also enables the operator to generate high-fidelity synthetic TV camera views showing motion events that are hidden in a given TV camera view or for which no TV camera views are available. The positioning accuracy achieved by this technique for a zoomed-in camera setting was about +/-5 mm, well within the allowable +/-12 mm error margin at the insertion of a 45 cm long tool in the servicing task.

  13. Sublimator Driven Coldplate Engineering Development Unit Test Results and Development of Second Generation SDC

    NASA Technical Reports Server (NTRS)

    Stephan, Ryan A.; Sheth, Rubik B.

    2009-01-01

    The Sublimator Driven Coldplate (SDC) is a unique piece of thermal control hardware that has several advantages over a traditional thermal control scheme. The principal advantage is the possible elimination of a pumped fluid loop, potentially increasing reliability and reducing complexity while saving both mass and power. Furthermore, the Integrated Sublimator Driven Coldplate (ISDC) concept couples a coolant loop with the previously described SDC hardware. This combination allows the SDC to be used as a traditional coldplate during long mission phases. The previously developed SDC technology cannot be used for long mission phases due to the fact that it requires a consumable feedwater for heat rejection. Adding a coolant loop also provides for dissimilar redundancy on the Altair Lander ascent module thermal control system, which is the target application for this technology. Tests were performed on an Engineering Development Unit at NASA s Johnson Space Center to quantify and assess the performance of the SDC. Correlated thermal math models were developed to help explain the test data. The paper also outlines the preliminary results of an ISDC concept being developed.

  14. Laboratory experiments to investigate sublimation rates of water ice in nighttime lunar regolith

    NASA Astrophysics Data System (ADS)

    Piquette, Marcus; Horányi, Mihály; Stern, S. Alan

    2017-09-01

    The existence of water ice on the lunar surface has been a long-standing topic with implications for both lunar science and in-situ resource utilization (ISRU). Cold traps on the lunar surface may have conditions necessary to retain water ice, but no laboratory experiments have been conducted to verify modeling results. We present an experiment testing the ability to thermally control bulk samples of lunar regolith simulant mixed with water ice under vacuum in an effort to constrain sublimation rates. The simulant used was JSC-1A lunar regolith simulant developed by NASA's Johnson Space Center. Samples with varying ratios of water ice and JSC-1A regolith simulant, totally about 1 kg, were placed under vacuum and cooled to 100 K to simulate conditions in lunar cold traps. The resulting sublimation of water ice over an approximately five-day period was measured by comparing the mass of the samples before and after the experimental run. Our results indicate that water ice in lunar cold traps is stable on timescales comparable to the lunar night, and should continue to be studied as possible resources for future utilization. This experiment also gauges the efficacy of the synthetic lunar atmosphere mission (SLAM) as a low-cost water resupply mission to lunar outposts.

  15. Sublimator Driven Coldplate Engineering Development Unit Test Results and Development of Second Generation SDC

    NASA Technical Reports Server (NTRS)

    Stephan, Ryan A.; Sheth, Rubik B.

    2009-01-01

    The Sublimator Driven Coldplate (SDC) is a unique piece of thermal control hardware that has several advantages over a traditional thermal control scheme. The principal advantage is the possible elimination of a pumped fluid loop, potentially increasing reliability and reducing complexity while saving both mass and power. Furthermore, the Integrated Sublimator Driven Coldplate (ISDC) concept couples a coolant loop with the previously described SDC hardware. This combination allows the SDC to be used as a traditional coldplate during long mission phases. The previously developed SDC technology cannot be used for long mission phases due to the fact that it requires a consumable feedwater for heat rejection. Adding a coolant loop also provides for dissimilar redundancy on the Altair Lander ascent module thermal control system, which is the target application for this technology. Tests were performed on an Engineering Development Unit at NASA s Johnson Space Center to quantify and assess the performance of the SDC. Correlated thermal math models were developed to help explain the test data. The paper also outlines the preliminary results of an ISDC concept being developed.

  16. Statistical theory of noble-gas crystals and the phenomenon of sublimation

    NASA Astrophysics Data System (ADS)

    Bondarev, V. N.

    2005-05-01

    We propose a consistent (without any fitting parameters) statistical theory of classical noble-gas crystals with pair interaction between atoms. Using the equation for the single-particle distribution function of the statistical system, we demonstrate the existence of an infinite number of exact sum rules for the amplitudes of the space-periodic solutions. Even the first sum rule leads to the solution which turns into the exact one at the absolute zero temperature. For the pair distribution function, we obtained the physically correct solution using the well-known exact relation for the compressibility as the self-consistent condition. As a result, we succeeded in recovering the equation of state of the crystal, and starting from the Lennard-Jones potential with the “gaseous” parameters, we calculated the temperature dependencies of the lattice constant and the isothermal compressibility of the crystal at the sublimation line. These calculations (including the form of the sublimation line itself) agree rather well with the corresponding experimental data for the argon-type media in the “classical” temperature region. The question about the bifurcation of the solutions is considered. Ways to further develop the theory are discussed.

  17. A high-resolution multi-slit phase space measurement technique for low-emittance beams

    SciTech Connect

    Thangaraj, J. C. T.; Piot, P.

    2012-12-21

    Precise measurement of transverse phase space of a high-brightness electron beamis of fundamental importance in modern accelerators and free-electron lasers. Often, the transverse phase space of a high-brightness, space-charge-dominated electron beam is measured using a multi-slit method. In this method, a transverse mask (slit/pepperpot) samples the beaminto a set of beamlets, which are then analyzed on to a screen downstream. The resolution in this method is limited by the type of screen used which is typically around 20 {mu}m for a high-sensitivity Yttrium Aluminum Garnet screen. Accurate measurement of sub-micron transverse emittance using this method would require a long drift space between the multi-slit mask and observation screen. In this paper, we explore a variation of the technique that incorporates quadrupole magnets between the multi-slit mask and the screen. It is shown that this arrangement can improve the resolution of the transverse-phase-space measurement with in a short footprint.

  18. Micrometeoroid and Orbital Debris Threat Mitigation Techniques for the Space Shuttle Orbiter

    NASA Technical Reports Server (NTRS)

    Hyde, James L.; Christiansen, Eric L.; Lear, Dana M.; Kerr, Justin H.

    2009-01-01

    An overview of significant Micrometeoroid and Orbital Debris (MMOD) impacts on the Payload Bay Door radiators, wing leading edge reinforced carbon-carbon panels and crew module windows will be presented, along with a discussion of the techniques NASA has implemented to reduce the risk from MMOD impacts. The concept of "Late Inspection" of the Nose Cap and Wing leading Edge (WLE) Reinforced Carbon Carbon (RCC) regions will be introduced. An alternative mated attitude with the International Space Station (ISS) on shuttle MMOD risk will also be presented. The significant threat mitigation effect of these two techniques will be demonstrated. The wing leading edge impact detection system, on-orbit repair techniques and disabled vehicle contingency plans will also be discussed.

  19. Micrometeoroid and Orbital Debris Threat Mitigation Techniques for the Space Shuttle Orbiter

    NASA Astrophysics Data System (ADS)

    Hyde, James L.; Christiansen, Eric L.; Lear, Dana M.; Kerr, Justin H.

    2009-03-01

    An overview of significant Micrometeoroid and Orbital Debris (MMOD) impacts on the Payload Bay Door radiators, wing leading edge reinforced carbon-carbon panels and crew module windows will be presented, along with a discussion of the techniques NASA has implemented to reduce the risk from MMOD impacts. The concept of "Late Inspection" of the Nose Cap and Wing Leading Edge (WLE) Reinforced Carbon Carbon (RCC) regions will be introduced. An alternative mated attitude with the International Space Station (ISS) on shuttle MMOD risk will also be presented. The significant threat mitigation effect of these two techniques will be demonstrated. The wing leading edge impact detection system, on-orbit repair techniques and disabled vehicle contingency plans will also be discussed.

  20. Spaced retrieval technique--a cognitive tool for social workers and their clients.

    PubMed

    Vance, David E; Struzick, Tom; Farr, Kenneth

    2010-02-01

    Social workers frequently work with clients who have cognitive deficits that impair their ability to perform instrumental activities of daily living and reduce their quality of life. Borrowing from the cognitive aging literature, the Spaced Retrieval Technique can be used by social workers to help their clients retain information needed for more autonomous functioning. This technique consists of recalling information over progressively longer periods of time until the information is successfully consolidated into long-term memory. The retained information may include adhering to medication regimens, keeping doctor's appointments, and remembering to pay bills. This technique is established and employed in early Alzheimer's disease, traumatic brain injury, and HIV. Implications for social work practice are posited.

  1. Sublimator Driven Coldplate Engineering Development Unit Test Results

    NASA Technical Reports Server (NTRS)

    Sheth, Rubik B.; Stephan, Ryan A.; Leimkuehler, Thomas O.

    2010-01-01

    The Sublimator Driven Coldplate (SDC) is a unique piece of thermal control hardware that has several advantages over a traditional thermal control scheme. The principal advantage is the possible elimination of a pumped fluid loop, potentially increasing reliability and reducing complexity while saving both mass and power. Because the SDC requires a consumable feedwater, it can only be used for short mission durations. Additionally, the SDC is ideal for a vehicle with small transport distances and low heat rejection requirements. An SDC Engineering Development Unit was designed and fabricated. Performance tests were performed in a vacuum chamber to quantify and assess the performance of the SDC. The test data was then used to develop correlated thermal math models. Nonetheless, an Integrated Sublimator Driven Coldplate (ISDC) concept is being developed. The ISDC couples a coolant loop with the previously described SDC hardware. This combination allows the SDC to be used as a traditional coldplate during long mission phases and provides for dissimilar system redundancy

  2. Effects of varying obliquity on Martian sublimation thermokarst landforms

    USGS Publications Warehouse

    Dundas, Colin M.

    2017-01-01

    Scalloped depressions in the Martian mid-latitudes are likely formed by sublimation of ice-rich ground. The stability of subsurface ice changes with the planetary obliquity, generally becoming less stable at lower axial tilt. As a result, the relative rates of sublimation and creep change over time. A landscape evolution model shows that these variations produce internal structure in scalloped depressions, commonly in the form of arcuate ridges, which emerge as depressions resume growth after pausing or slowing. In other scenarios, the formation of internal structure is minimal. Significant uncertainties in past climate and model parameters permit a range of scenarios. Ridges observed in some Martian scalloped depressions could date from obliquity lows or periods of low ice stability occurring <5 Ma, suggesting that the pits are young features and may be actively evolving.

  3. Comparing And Combining Space and Terrestrial Geodetic Techniques To Monitor Crustal Deformation

    NASA Astrophysics Data System (ADS)

    Zerbini, S.; Cecconi, G.; Colombo, D.; Matonti, F.; Richter, B.; Rocca, F.; Wilmes, H.

    2004-12-01

    It is of particular importance to define and establish appropriate observational strategies characterized by the ability to measure, with high accuracy, spatially and time continuous deformations of the land surface. An ensemble of space, airborne and terrestrial techniques can be adopted by taking advantage of the complementary strengths of the different observations. We present a network encompassing northeastern Italy, which extends from the Apennines to the southeastern Po Plain and, along the Adriatic coast, to the Venice area and Trieste. First results mainly concern a study of land subsidence performed by comparing and combining different space and terrestrial techniques, which were co-located in several stations of the network. High-accuracy knowledge of subsidence rates is of particular importance in the Venice area for the re-organization of the lagoon territory and for building an adequate protection from increasing sea level and extreme events. Examples are provided for the stations in the network such as Medicina, Bologna and Marina di Ravenna where the available data series are several years long. At Medicina, the results of CGPS, superconducting and absolute gravimeter and InSAR observations, in combination with several meteoclimatic data series, are compared and combined. At the Bologna station, CGPS, absolute gravity and InSAR data are acquired while at Marina di Ravenna, on the Adriatic coast, CGPS and InSAR observations are available. All InSAR data are processed by means of the PS technique. The ensemble of adopted space and terrestrial techniques will make it possible to acquire a thorough understanding of seasonal, long-term regional/local geophysical phenomena as well as climate-related impacts affecting the station motions.

  4. Measuring Tropospheric Winds from Space Using a Coherent Doppler Lidar Technique

    NASA Technical Reports Server (NTRS)

    Miller, Timothy L.; Kavaya, Michael J.; Emmitt, G. David

    1999-01-01

    The global measurement of tropospheric wind profiles has been cited by the operational meteorological community as the most important missing element in the present and planned observing system. The most practical and economical method for obtaining this measurement is from low earth orbit, utilizing a Doppler lidar (laser radar) technique. Specifically, this paper will describe the coherent Doppler wind lidar (CDWL) technique, the design and progress of a current space flight project to fly such a system on the Space Shuttle, and plans for future flights of similar instruments. The SPARCLE (SPAce Readiness Coherent Lidar Experiment) is a Shuttle-based instrument whose flight is targeted for March, 2001. The objectives of SPARCLE are three-fold: Confirm that the coherent Doppler lidar technique can measure line-of-sight winds to within 1-2 m/s accuracy; Collect data to permit validation and improvement of instrument performance models to enable better design of future missions; and Collect wind and backscatter data for future mission optimization and for atmospheric studies. These objectives reflect the nature of the experiment and its program sponsor, NASA's New Millennium Program. The experiment is a technology validation mission whose primary purpose is to provide a space flight validation of this particular technology. (It should be noted that the CDWL technique has successfully been implemented from ground-based and aircraft-based platforms for a number of years.) Since the conduct of the SPARCLE mission is tied to future decisions on the choice of technology for free-flying, operational missions, the collection of data is intrinsically tied to the validation and improvement of instrument performance models that predict the sensitivity and accuracy of any particular present or future instrument system. The challenges unique to space flight for an instrument such as SPARCLE and follow-ons include: Obtaining the required lidar sensitivity from the long distance

  5. Vapor pressures and enthalpies of sublimation of D-glucose, D-xylose, cellobiose, and levoglucosan

    SciTech Connect

    Oja, V.; Suuberg, E.M.

    1999-01-01

    The vapor pressures of {alpha}-D-glucose (or dextrose), D-xylose, D-cellobiose (or 4-{beta}-D-glucopyranosyl-D-glucopyranose), and levoglucosan (or 1,6-anhydro-{beta}-D-glucopyranose) have been measured using the Knudsen effusion technique, in the range of temperatures from 344 to 488 K. The measurements were all made in the solid sublimation regime, and enthalpies of sublimation were calculated from the Clausius-Claperon equation. The vapor pressures may be correlated by ln(P/Pa) = A {minus} B/(T/K), where A = 53.16, B = 23.382 ({+-}600) for D-glucose (395--406 K), A = 46.29 and B = 19,006 ({+-} 375) for D-xylose (370--395 K), and A = 70.30 and B = 36,264 ({+-} 5,220) for cellobiose (474--488 K). Levoglucosan displayed a solid phase transition at approximately 386 K, and its vapor pressure was affected accordingly. For this material, A = 38.96 and B = 15,049 ({+-} 123) in the temperature range 344--386 K and A = 31.19 and B = 12,066 ({+-} 709) in the temperature range 386--405 K.

  6. A new technique of bone cement augmentation via the disc space for percutaneous pedicle screw fixation.

    PubMed

    Park, Chang Kyu; Park, Choon Keun; Lee, Dong Chan; Lee, Dong Geun

    2016-01-01

    In elderly patients with severe osteoporosis, instrumented lumbar interbody fusion may result in fixation failure or nonunion because of decreased pedicle screw pullout strength or increased interbody graft subsidence risk. Thus, given its many advantages, percutaneous pedicle screw fixation with cement augmentation can be an effective method to use in elderly patients. The authors report on an easy, safe, and economical technique for bone cement augmentation using a bone biopsy needle inserted into the disc space in 2 osteoporotic patients who were treated with posterior interbody fusion and percutaneous pedicle screw fixation. Two elderly patients who complained of back pain and intermittent neurological claudication underwent posterior interbody fusion with percutaneous pedicle screw fixation. After routinely assembling rods on the screws, a bone biopsy needle was inserted into the disc space via the operative field; the needle was then placed around the tips of the screws using fluoroscopic radiography for guidance. Bone cement was injected through the bone biopsy needle, also under fluoroscopic radiography guidance. Both patients' symptoms improved after the operation, and there was no evidence of cage subsidence or screw loosening at the 4-month follow-up. The indirect technique of bone cement augmentation via the disc space for percutaneous screw fixation could be an easy, safe, and economical method.

  7. Investigation of bone changes in microgravity during long and short duration space flight: comparison of techniques.

    PubMed

    McCarthy, I; Goodship, A; Herzog, R; Oganov, V; Stussi, E; Vahlensieck, M

    2000-12-01

    Loss of bone mass is a continuing problem in long-term space flight. Although counter-measure programmes have been developed, effective assessment of these programmes is hampered by a lack of monitoring techniques that can be used in-flight. Three techniques were used to evaluate changes in bone during two missions of 180 and 20 days to the MIR space station, involving three subjects. Dual energy X-ray absorptiometry (DXA) was used before and after flight to measure whole body and regional bone mineral density (BMD). Ultrasonic measurements of velocity (SOS) and broadband attenuation (BUA) of the calcaneus were measured during the 180 day mission and before and after the 20 day mission. Phase velocity of flexural waves in the tibia was also measured on the same days as the ultrasonic measurements of the calcaneus. DXA measurements demonstrated significant variation between different sites in the body for changes in BMD, with the greatest changes occurring in the lumbar spine and proximal femur. There was a trend for increasing phase velocity in the tibia during the 180 mission, but this was not significant. BUA and SOS measurements of the calcaneus showed consistent but divergent patterns of changes during the mission. Although in-flight measurements of bone using ultrasound or phase velocity may provide information on the kinetics of bone loss in space flight, the heterogeneity of response in the skeleton means that it is difficult to predict overall bone loss from measurements at one particular site.

  8. Interferometric and nonlinear-optical spectral-imaging techniques for outer space and live cells

    NASA Astrophysics Data System (ADS)

    Itoh, Kazuyoshi

    2015-12-01

    Multidimensional signals such as the spectral images allow us to have deeper insights into the natures of objects. In this paper the spectral imaging techniques that are based on optical interferometry and nonlinear optics are presented. The interferometric imaging technique is based on the unified theory of Van Cittert-Zernike and Wiener-Khintchine theorems and allows us to retrieve a spectral image of an object in the far zone from the 3D spatial coherence function. The retrieval principle is explained using a very simple object. The promising applications to space interferometers for astronomy that are currently in progress will also be briefly touched on. An interesting extension of interferometric spectral imaging is a 3D and spectral imaging technique that records 4D information of objects where the 3D and spectral information is retrieved from the cross-spectral density function of optical field. The 3D imaging is realized via the numerical inverse propagation of the cross-spectral density. A few techniques suggested recently are introduced. The nonlinear optical technique that utilizes stimulated Raman scattering (SRS) for spectral imaging of biomedical targets is presented lastly. The strong signals of SRS permit us to get vibrational information of molecules in the live cell or tissue in real time. The vibrational information of unstained or unlabeled molecules is crucial especially for medical applications. The 3D information due to the optical nonlinearity is also the attractive feature of SRS spectral microscopy.

  9. Coding techniques to mitigate fading on free-space optical communication links

    NASA Astrophysics Data System (ADS)

    Henniger, Hennes; Epple, Bernhard; Milner, Stuart D.; Davis, Christopher C.

    2008-08-01

    Free-space directional communication links (FSO) experience short-term link outages or fades because of atmospheric turbulence, and longer term link outages because of obscuration resulting from either atmospheric conditions, beam pointing errors, or temporary line-of-sight obstructions for links from mobile or static nodes. Various approaches can be used to mitigate these effects. Physical-layer techniques, such as dynamic thresholding, time delayed diversity, and data encoding can significantly reduce the effects of short term (millisecond scale) outages caused by deep turbulenceinduced fades. Outages on a longer term (second scale) producing large data loss can be mitigated by packet-layer largeblock, error protection techniques. In this paper, we will first introduce physical-layer mitigation techniques. Second we present experimental data comparing the latencies and throughput of different means of packet-based error protection techniques. We will discuss the influence of error protection techniques to quality of service issues like error probability and delay and further compare this with service requirements given by the application.

  10. Impact of nonintentional Al impurity to carrier lifetime and diffusion in sublimation grown 3C heterostructures

    NASA Astrophysics Data System (ADS)

    Ščajev, P.; Jarašiunas, K.; Kadys, A.; Storasta, J.; Abramov, P. L.; Lebedev, S. P.; Lebedev, A. A.

    2010-11-01

    Using optical techniques, we analyzed an impact of non-intentional Al mpurity and twin boundaries to photoelectrical properties of sublimation-grown 3C heterostructures. Differential transmission techniques revealed Al related contribution to probe beam absorption with cross-section σAl = (1.8±0.5)×10-17 cm2 at 1064 nm, being four times stronger that the free-carrier absorption cross-section at given wavelength. Temperature dependent carrier recombination rates provided trap activation energy of 170 and 210 meV in two samples with different Al concentration. Saturation of probe beam absorption with excitation allowed determination of electrically active Al concentration, not gettered at grain boundaries. Increase of room-temperature mobility with injection in the highly defective layer and the corresponding lifetime decrease pointed out contribution of point and structural defects to carrier scattering.

  11. VCM-OFDM technique for advanced space communications system with high spectral efficiency

    NASA Astrophysics Data System (ADS)

    Li, Jionghui; Zhou, Qing; Xiong, Weiming; Zhang, Ying; Yao, Chen

    2016-11-01

    The development of precise scientific payloads brings higher demand on the efficiency of space communications system to transmit the increasing volume of scientific data. Aiming to this issue, Orthogonal Frequency Division Multiplexing (OFDM) is chosen for its inherent capability of high-rate data transmission. Further, considering the dynamic link condition due to satellite orbital motion, we propose a new technique which combines Variable Coding Modulation (VCM) with OFDM to enhance the communication link spectral efficiency with required transmission reliability. With VCM-OFDM technique, the channel coding and modulation mode can be variable with time according to the link conditions, in order to fit the link budget curve and maintain a relatively fixed link margin. Hence, link resource waste can be reduced and throughput can be remarkably improved. Considering that OFDM-based systems are sensitive to Doppler shifts/spread, the coding and modulation mode (CODMOD) selection should be optimized subject to this scenario. This paper introduces the architecture of near-earth space data transmission system based on VCM-OFDM technique. The Doppler influence is analyzed through simulation and the CODMOD selection algorithm is discussed. The results prove the high performance on spectral efficiency enhancement of VCM-OFDM by comparison with several existing alternative methods.

  12. Coupled fluid-thermal analysis of low-pressure sublimation and condensation with application to freeze-drying

    NASA Astrophysics Data System (ADS)

    Ganguly, Arnab

    Freeze-drying is a low-pressure, low-temperature condensation pumping process widely used in the manufacture of bio-pharmaceuticals for removal of solvents by sublimation. The goal of the process is to provide a stable dosage form by removing the solvent in such a way that the sensitive molecular structure of the active substance is least disturbed. The vacuum environment presents unique challenges for understanding and controlling heat and mass transfer in the process. As a result, the design of equipment and associated processes has been largely empirical, slow and inefficient. A comprehensive simulation framework to predict both, process and equipment performance is critical to improve current practice. A part of the dissertation is aimed at performing coupled fluid-thermal analysis of low-pressure sublimation-condensation processes typical of freeze-drying technologies. Both, experimental and computational models are used to first understand the key heat transfer modes during the process. A modeling and computational framework, validated with experiments for analysis of sublimation, water-vapor flow and condensation in application to pharmaceutical freeze-drying is developed. Augmented with computational fluid dynamics modeling, the simulation framework presented here allows to predict for the first time, dynamic product/process conditions taking into consideration specifics of equipment design. Moreover, by applying the modeling framework to process design based on a design-space approach, it has demonstrated that there is a viable alternative to empiricism.

  13. Properties of filamentary sublimation residues from dispersions of clay in ice. [on Martian poles, comet nuclei, and icy satellites

    NASA Technical Reports Server (NTRS)

    Saunders, R. S.; Parker, T. J.; Stephens, J. B.; Fanale, F. P.; Sutton, S.

    1986-01-01

    Results are reported from experimental studies of the formation of ice mixed with mineral particles in an effort to simulate similar processes on natural surfaces such as at the Martian poles, on comet nuclei and on icy satellites. The study consisted of low-pressure, low-temperature sublimations of water ice from dilutions of water-clay (montmorillonite and Cabosil) dispersions of various component ratios. Liquid dispersions were sprayed into liquid nitrogen to form droplets at about -50 C. Both clay-water dispersions left a filamentary residue on the bottom of the Dewar after the water ice had sublimated off. The residue was studied with optical and SEM microscopy, the latter method revealing a high electrical conductivity in the residue. The results suggest that the sublimation of the water ice can leave a surface crust, which may be analogous to processes at the Martian poles and on comet nuclei. The process could proceed by the attachment of water molecules to salt crystals during the hottest part of the Martian year. The residue remaining was found to remain stable up to 370 C, be porous, and remain resilient, which could allow it to insulate ice bodies such as comets in space.

  14. Recursive Techniques for Computing Gluon Scattering in Anti-de-Sitter Space

    NASA Astrophysics Data System (ADS)

    Shyaka, Claude; Kharel, Savan

    2016-03-01

    The anti-de Sitter/conformal field theory correspondence is a relationship between two kinds of physical theories. On one side of the duality are special type of quantum (conformal) field theories known as the Yang-Mills theory. These quantum field theories are known to be equivalent to theories of gravity in Anti-de Sitter (AdS) space. The physical observables in the theory are the correlation functions that live in the boundary of AdS space. In general correlation functions are computed using configuration space and the expressions are extremely complicated. Using momentum basis and recursive techniques developed by Raju, we extend tree level correlation functions for four and five-point correlation functions in Yang-Mills theory in Anti-de Sitter space. In addition, we show that for certain external helicity, the correlation functions have simple analytic structure. Finally, we discuss how one can generalize these results to n-point functions. Hendrix college odyssey Grant.

  15. Quantum-field-theoretical approach to phase-space techniques: Generalizing the positive-P representation

    SciTech Connect

    Plimak, L.I.; Fleischhauer, M.; Olsen, M.K.; Collett, M.J.

    2003-01-01

    We present an introduction to phase-space techniques (PST) based on a quantum-field-theoretical (QFT) approach. In addition to bridging the gap between PST and QFT, our approach results in a number of generalizations of the PST. First, for problems where the usual PST do not result in a genuine Fokker-Planck equation (even after phase-space doubling) and hence fail to produce a stochastic differential equation (SDE), we show how the system in question may be approximated via stochastic difference equations (S{delta}E). Second, we show that introducing sources into the SDE's (or S{delta}E's) generalizes them to a full quantum nonlinear stochastic response problem (thus generalizing Kubo's linear reaction theory to a quantum nonlinear stochastic response theory). Third, we establish general relations linking quantum response properties of the system in question to averages of operator products ordered in a way different from time normal. This extends PST to a much wider assemblage of operator products than are usually considered in phase-space approaches. In all cases, our approach yields a very simple and straightforward way of deriving stochastic equations in phase space.

  16. State Space Composition Technique for Intelligent Wheel Chair Adapting to Environment.

    NASA Astrophysics Data System (ADS)

    Hamagami, Tomoki; Hirata, Hironori

    This paper describes a state space composition technique for the adaptation to environment in the autonomous behavior of intelligent wheel chair (IWC).In the product like IWC with actual sensors, composing state space is difficult problem since environmental information can not be observed sufficiently from restricted sensor inputs.A lot of states observed from same environment position raise the fail of the learning and adaptation with active learning approach.In order to compensate for the effects of the sensor configuration, that is sensor position, angle and precision, a normalization processing of position detector is introduced.In sensor normalization process, IWC scans present environment via range sensors with executing spot-turn, and prepare scan-patterns of each sensor.Then the normalization process adjusts the phase and dynamic range of each pattern to the reference sensor scan-pattern, analyzing phase differences and scale factors of each pattern against reference pattern.Using phase difference and scale factors, automated state space composition is possible.From the simulation experiment with both artificial and real-worlddraft, the automated state space construction is confirmed as a practical approach for pre-processing for environment learning and adaptation.

  17. Visualization of hot flows of tall space fires in model experiments with Schlieren Photography technique.

    PubMed

    Su, ChungHwei; Wang, ShiuanCheng; Shih, ChiaYuan; Yang, YungChang

    2016-01-01

    The natural smoke exhaust system for tall spaces is more advantageous than the mechanical type of exhaust. In Taiwan, the effectiveness of natural smoke exhaust systems is inspected only by checking the vent area size. However, the air flow field in a tall space is very complicated, both at ordinary times or during fires. This study used Schlieren Photography technique, on the principle that light rays are refracted when penetrating materials of different densities, to test and simulate the dynamic measurement of hot air in tall space model. A single-mirror Schlieren system, including an 838 mm (H) × 736 mm (W) square concave mirror, as well as the focal length of 3100 mm was adopted. The experimental process of six smokeless candles were used for 1/12.5 model experiment to record the dynamic distribution and accumulation of air flow in the abovementioned space. FDS software was used to simulate various fire scenarios. The different locations of openings in some cases were studied with the maximum temperature scales of 40 and 45 °C, separately. The simulation results and experimental images showed highly similar hot air flow patterns. Schlieren Photography was proved capable of recording and visualizing the dynamic flow of hot air immediately, directly and accurately.

  18. Semantic definitions of space flight control center languages using the hierarchical graph technique

    NASA Technical Reports Server (NTRS)

    Zaghloul, M. E.; Truszkowski, W.

    1981-01-01

    In this paper a method is described by which the semantic definitions of the Goddard Space Flight Control Center Command Languages can be specified. The semantic modeling facility used is an extension of the hierarchical graph technique, which has a major benefit of supporting a variety of data structures and a variety of control structures. It is particularly suited for the semantic descriptions of such types of languages where the detailed separation between the underlying operating system and the command language system is system dependent. These definitions were used in the definition of the Systems Test and Operation Language (STOL) of the Goddard Space Flight Center which is a command language that provides means for the user to communicate with payloads, application programs, and other ground system elements.

  19. Space shuttle active-pogo-suppressor control design using linear quadratic regulator techniques

    NASA Technical Reports Server (NTRS)

    Lehtinen, B.; Lorenz, C. F.

    1979-01-01

    Two methods of active pogo suppression (stabilization) for the space shuttle vehicle were studied analytically. The basis for both approaches was the linear quadratic regulator, state space technique. The first approach minimized root-mean-square pump inlet pressure by using either fullstate feedback, partial-state feedback, or output feedback with a Kalman filter. The second approach increased the modal damping associated with the critical structural modes by using either full-state feedback or reconstructed state feedback. A number of implementable controls were found by both approaches. The designs were analyzed with respect to sensitivity, complexity, and controller energy requirements, as well as controller performance. Practical controllers resulting from the two design approaches tended to use pressure and flow as feedback variables for the minimum-rms method and structural accelerations or velocities for the modal control method. Both approaches are suitable for the design of active pogo-suppression controllers.

  20. Semantic definitions of space flight control center languages using the hierarchical graph technique

    NASA Technical Reports Server (NTRS)

    Zaghloul, M. E.; Truszkowski, W.

    1981-01-01

    In this paper a method is described by which the semantic definitions of the Goddard Space Flight Control Center Command Languages can be specified. The semantic modeling facility used is an extension of the hierarchical graph technique, which has a major benefit of supporting a variety of data structures and a variety of control structures. It is particularly suited for the semantic descriptions of such types of languages where the detailed separation between the underlying operating system and the command language system is system dependent. These definitions were used in the definition of the Systems Test and Operation Language (STOL) of the Goddard Space Flight Center which is a command language that provides means for the user to communicate with payloads, application programs, and other ground system elements.

  1. Evaluation of radioisotope tracer and activation analysis techniques for contamination monitoring in space environment simulation chambers

    NASA Technical Reports Server (NTRS)

    Smathers, J. B.; Kuykendall, W. E., Jr.; Wright, R. E., Jr.; Marshall, J. R.

    1973-01-01

    Radioisotope measurement techniques and neutron activation analysis are evaluated for use in identifying and locating contamination sources in space environment simulation chambers. The alpha range method allows the determination of total contaminant concentration in vapor state and condensate state. A Cf-252 neutron activation analysis system for detecting oils and greases tagged with stable elements is described. While neutron activation analysis of tagged contaminants offers specificity, an on-site system is extremely costly to implement and provides only marginal detection sensitivity under even the most favorable conditions.

  2. Space diversity performance prediction for earth-satellite paths using radar modeling techniques

    NASA Technical Reports Server (NTRS)

    Goldhirsh, J.

    1982-01-01

    Space diversity performance is examined on the basis of radar modeling techniques. Radar-derived joint probability distributions are calculated for determining path attenuation and statistical formulation. The computational aspects of the model are discussed in terms of the data base, determining path length and converting statistics to other path angles. The results are presented in terms of prediction accuracy, predicted joint probability distributions, diversity gain, and the autocorrection function. When compared to other models, this model's rain-derived relative diversity gain shows good agreement.

  3. Coherent uplink arraying techniques for next generation space communications and planetary radar systems

    NASA Astrophysics Data System (ADS)

    Geldzahler, B. J.

    2011-06-01

    For several years, NASA has been pursuing demonstrations and development of coherent uplink arraying techniques for the next generation space communications and planetary radar systems. In addition radio science experiments would benefit with a 1000 times increase in signal to noise over current systems. I shall describe the three methods of uplink arraying NASA has pursued, all successful, and share the vision for going forward from laboratory demonstrations to the proposed implementation and deployment of a dedicated multi-purpose facility to infuse an amalgam of these methods into a system that enhances NASA's missions.

  4. Technique of fiber optics used to localize epidural space in piglets.

    PubMed

    Ting, Chien-Kun; Chang, Yin

    2010-05-24

    Technique of loss-of-resistance in epidural block is commonly used for epidural anesthesia in humans with approximately 90% successful rate. However, it may be one of the most difficult procedures to learn for anesthesia residents in hospital. A two-wavelength (650 nm and 532 nm) fiber-optical method has been developed according to the characteristic reflectance spectra of ex-vivo porcine tissues, which are associated with the needle insertion to localize the epidural space (ES). In an in-vivo study in piglets showed that the reflected lights from ES and its surrounding tissue ligamentum flavum (LF) are highly distinguishable. This indicates that this technique has potential to localize the ES on the spot without the help of additional guiding assistance.

  5. Towards a novel continuous sublimation extraction/laser spectroscopy method for greenhouse gas measurements in the oldest ice

    NASA Astrophysics Data System (ADS)

    Bereiter, Bernhard; Maechler, Lars; Schmitt, Jochen; Walther, Remo; Tuzson, Béla; Scheidegger, Philipp; Emmenegger, Lukas; Fischer, Hubertus

    2017-04-01

    Ice cores are unique archives of ancient air providing the only direct record of past greenhouse gases - key in reconstructing the roles of greenhouse gases in past climate changes. The European Partnership in Ice Core Sciences (EuroPICS) plans to drill an ice core extending over 1.5 Ma, nearly doubling the time span of the existing greenhouse record and covering the time period of the Mid Pleistocene Transition. The ice covering the time interval from 1-1.5 Ma is expected to be close to the bedrock and, due to glacial flow, extremely thinned. A 10,000 yr glacial/interglacial transition can be compressed in 1 m of ice. The targeted 100 yr resolution therefore constrains the sample size to 15-30 g containing only 1-2ml STP air. Within the deepSlice project we aim to unlock such atmospheric archives in extremely thinned ice by developing a novel coupled semi-continuous sublimation extraction/laser spectroscopy system. Vacuum sublimation, with an infrared source, has been chosen as extraction method as it allows 100% gas extraction of all gas species from ice without changing the isotopic composition of CO2. In order to reduce ice waste and accelerate sample throughput, we are building a sublimation extraction system that is able to continuously sublimate an ice-core section and subsequently collect discrete full air samples. For the gas analytics, we develop a custom-made mid-infrared laser spectrometer allowing simultaneous measurement of the CO2, CH4 and N2O concentrations as well as the isotopic composition of CO2 on air samples of only 1-2 ml STP. The two systems will be coupled via cryo-trapping of the sample air in dip tubes, followed by expansion of the sample air into the laser spectrometer. Due to the nondestructive laser technique, the air sample can be recollected and reused for further analytics.

  6. An atomic beam of 6Li — 7Li for high resolution spectroscopy from matrix isolation sublimation

    NASA Astrophysics Data System (ADS)

    Oliveira, A. N.; Sacramento, R. L.; Silva, B. A.; Uhlmann, F. O.; Wolff, W.; Cesar, C. L.

    2016-07-01

    We propose the Matrix Isolation Sublimation (MlSu) technique for generating cold lithium atoms for the measurement of the 6Li - 7Li isotope shift in D1 and D2 transitions. The technique is capable of generating cold 6Li and 7Li beams at 4 K with forward velocity of 125 m/s. Using this beam we offer a distinguished source of lithium atoms for transitions measurements, adding a new possibility to make high resolution spectroscopy towards improving the experimental checks of the theory.

  7. Applications of Low Density Flow Techniques and Catalytic Recombination at the Johnson Space Center

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.

    2000-01-01

    The talk presents a brief background on defInitions of catalysis and effects associated with chemically nonequilibrium and low-density flows of aerospace interest. Applications of catalytic recombination on surfaces in dissociated flow are given, including aero heating on reentry spacecraft thermal protection surfaces and reflection of plume flow on pressure distributions associated with the space station. Examples include aero heating predictions for the X-38 test vehicle, the inlet of a proposed gas-sampling probe used in high enthalpy test facilities, and a parabolic body at angle of attack. The effect of accommodation coefficients on thruster induced pressure distributions is also included. Examples of tools used include simple aero heating formulas based on boundary layer solutions, an engineering approximation that uses axisymmetric viscous shock layer flow to simulate full three dimensional flow, full computational fluid dynamics, and direct simulation Monte-Carlo calculations. Methods of determining catalytic recombination rates in arc jet flow are discus ed. An area of catalysis not fully understood is the formation of single-wall carbon nanotubes (SWNT) with gas phase or nano-size metal particles. The Johnson Space Center is making SWNTs using both a laser ablation technique and an electric arc vaporization technique.

  8. Petascale Kinetic Simulations in Space Sciences: New Simulations and Data Discovery Techniques and Physics Results

    NASA Astrophysics Data System (ADS)

    Karimabadi, Homa

    2012-03-01

    Recent advances in simulation technology and hardware are enabling breakthrough science where many longstanding problems can now be addressed for the first time. In this talk, we focus on kinetic simulations of the Earth's magnetosphere and magnetic reconnection process which is the key mechanism that breaks the protective shield of the Earth's dipole field, allowing the solar wind to enter the Earth's magnetosphere. This leads to the so-called space weather where storms on the Sun can affect space-borne and ground-based technological systems on Earth. The talk will consist of three parts: (a) overview of a new multi-scale simulation technique where each computational grid is updated based on its own unique timestep, (b) Presentation of a new approach to data analysis that we refer to as Physics Mining which entails combining data mining and computer vision algorithms with scientific visualization to extract physics from the resulting massive data sets. (c) Presentation of several recent discoveries in studies of space plasmas including the role of vortex formation and resulting turbulence in magnetized plasmas.

  9. Correlation techniques as applied to pose estimation in space station docking

    NASA Astrophysics Data System (ADS)

    Rollins, John M.; Juday, Richard D.; Monroe, Stanley E., Jr.

    2002-08-01

    The telerobotic assembly of space-station components has become the method of choice for the International Space Station (ISS) because it offers a safe alternative to the more hazardous option of space walks. The disadvantage of telerobotic assembly is that it does not necessarily provide for direct arbitrary views of mating interfaces for the teleoperator. Unless cameras are present very close to the interface positions, such views must be generated graphically, based on calculated pose relationships derived from images. To assist in this photogrammetric pose estimation, circular targets, or spots, of high contrast have been affixed on each connecting module at carefully surveyed positions. The appearance of a subset of spots must form a constellation of specific relative positions in the incoming image stream in order for the docking to proceed. Spot positions are expressed in terms of their apparent centroids in an image. The precision of centroid estimation is required to be as fine as 1/20th pixel, in some cases. This paper presents an approach to spot centroid estimation using cross correlation between spot images and synthetic spot models of precise centration. Techniques for obtaining sub-pixel accuracy and for shadow and lighting irregularity compensation are discussed.

  10. Non-Intrusive Techniques of Inspections During the Pre-Launch Phase of Space Vehicle

    NASA Technical Reports Server (NTRS)

    Thirumalainambi, Rejkumar; Bardina, Jorge E.

    2005-01-01

    This paper addresses a method of non-intrusive local inspection of surface and sub-surface conditions, interfaces, laminations and seals in both space vehicle and ground operations with an integrated suite of imaging sensors during pre-launch operations. It employs an advanced Raman spectrophotometer with additional spectrophotometers and lidar mounted on a flying robot to constantly monitor the space hardware as well as inner surface of the vehicle and ground operations hardware. This paper addresses a team of micro flying robots with necessary sensors and photometers to monitor the entire space vehicle internally and externally. The micro flying robots can reach altitude with least amount of energy, where astronauts have difficulty in reaching and monitoring the materials and subsurface faults. The micro flying robot has an embedded fault detection system which acts as an advisory system and in many cases micro flying robots act as a Supervisor to fix the problems. As missions expand to a sustainable presence in the Moon, and extend for durations longer than one year in lunar outpost, the effectiveness of the instrumentation and hardware has to be revolutionized if NASA is to meet high levels of mission safety, reliability, and overall success. The micro flying robot uses contra-rotating propellers powered by an ultra-thin, ultrasonic motor with currently the world's highest power weight ratio, and is balanced in mid-air by means of the world's first stabilizing mechanism using a linear actuator. The essence of micromechatronics has been brought together in high-density mounting technology to minimize the size and weight. The robot can take suitable payloads of photometers, embedded chips for image analysis and micro pumps for sealing cracks or fixing other material problems. This paper also highlights advantages that this type of non-intrusive techniques offer over costly and monolithic traditional techniques.

  11. Nonintrusive techniques of inspections during the pre-launch phase of space vehicle

    NASA Astrophysics Data System (ADS)

    Thirumalainambi, Rajkumar; Bardina, Jorge E.; Miyazawa, Osamu

    2005-05-01

    As missions expand to a sustainable presence in the Moon, and extend for durations longer than one year in lunar outpost, the effectiveness of the instrumentation and hardware has to be revolutionized if NASA is to meet high levels of mission safety, reliability, and overall success. This paper addresses a method of non-intrusive local inspection of surface and sub-surface conditions, interfaces, laminations and seals in both space vehicle and ground operations with an integrated suite of imaging sensors during pre-launch operations. It employs an advanced Raman spectrometer with additional spectrometers and lidar mounted on a flying robot to constantly monitor the space hardware as well as inner surface of the vehicle and ground operations hardware. A team of micro flying robots with necessary sensors and photometers is required to internally and externally monitor the entire space vehicle. The micro flying robots should reach an altitude with least amount of energy, where astronauts have difficulty in reaching and monitoring the materials and subsurface faults. The micro flying robots have an embedded fault detection system which acts as an advisory system and in many cases micro flying robots act as a `Supervisor' to fix the problems. The micro flying robot uses contra-rotating propellers powered by an ultra-thin, ultrasonic motor with currently the world's highest power weight ratio, and is balanced in mid-air by means of the world's first stabilizing mechanism using a linear actuator. The essence of micromechatronics has been brought together in high-density mounting technology to minimize the size and weight. Each robot can take suitable payloads of photometers, embedded chips for image analysis and micro pumps for sealing cracks or fixing other material problems. This paper also highlights advantages that this type of non-intrusive techniques offer over costly and monolithic traditional techniques.

  12. Low-Complexity, High-Performance Bandwidth Efficient Coding and Coded Modulation Techniques for Satellite and Space Communications

    NASA Technical Reports Server (NTRS)

    Costello, Daniel J., Jr.

    1993-01-01

    The semi-annual progress report for NASA grant NAG5-557 is presented. The report contains three papers concerning bandwidth efficient coding and coded modulation techniques for satellite and space communications.

  13. Problems at the Leading Edge of Space Weathering as Revealed by TEM Combined with Surface Science Techniques

    NASA Astrophysics Data System (ADS)

    Christoffersen, R.; Dukes, C. A.; Keller, L. P.; Rahman, Z.; Baragiola, R. A.

    2015-11-01

    Analytical field-emission TEM techniques cross-correlated with surface analyses by X-ray photoelectron spectroscopy (XPS) provides a unique two-prong approach for characterizing how solar wind ion processing contributes to space weathering.

  14. Preparation of 2:1 urea-succinic acid cocrystals by sublimation

    NASA Astrophysics Data System (ADS)

    Zhang, Tian; Yu, Qiushuo; Li, Xiaorui; Ma, Xiaoxun

    2017-07-01

    The aim of this study is to introduce a sublimation method for preparing cocrystals. The 2:1 urea-succinic acid cocrystals were generated by a simple sublimation apparatus, analyzed by Powder X-ray Diffraction (PXRD), Transmission Fourier Transform Infrared (FTIR) and Differential Scanning Calorimetry (DCS). The role of supersaturations in vapor crystallization was also discussed in detail. This work showed sublimation was a promising method for cocrystallization.

  15. Sublimation measurements and analysis of high temperature thermoelectric materials and devices

    NASA Technical Reports Server (NTRS)

    Shields, V.; Noon, L.

    1983-01-01

    High temperature thermoelectric device sublimation effects are compared for rare earth sulfides, selenides, and state-of-the-art Si-Ge alloys. Although rare earth calcogenides can potentially exhibit superior sublimation characteristics, the state-of-the-art Si-Ge alloy with silicon nitride sublimation-inhibitive coating has been tested to 1000 C. Attention is given to the ceramic electrolyte cells, forming within electrical and thermal insulation, which affect leakage conductance measurements in Si-Ge thermoelectric generators.

  16. New minimally invasive discectomy technique through the interlaminar space using a percutaneous endoscope.

    PubMed

    Dezawa, A; Sairyo, K

    2011-05-01

    The serial dilating technique used to access herniated discs at the L5-S1 space using percutaneous endoscopic discectomy (PED) via an 8 mm skin incision can possibly injure the S1 nerve root. In this paper, we describe in detail a new surgical procedure to safely access the disc and to avoid the nerve root damage. This small-incision endoscopic technique, small-incision microendoscopic discectomy (sMED), mimics microendoscopic discectomy and applies PED. The sMED approach is similar to the well-established microendoscopic discectomy technique. To secure the surgical field, a duckbill-type PED cannula is used. Following laminotomy of L5 using a high-speed drill, the ligamentum flavum is partially removed using the Kerrison rongeur. Using the curved nerve root retractor, the S1 nerve root is gradually and gently moved caudally. Following the compete retraction of the S1 nerve root to the caudal side of the herniated nucleus pulposus (HNP), the nerve root is retracted safely medially and caudally using the bill side of the duckbill PED cannula. Next, using the HNP rongeur for PED, the HNP is removed piece by piece until the nerve root is decompressed. A total of 30 patients with HNP at the L5-S1 level underwent sMED. In all cases, HNP was successfully removed and patients showed improvement following surgery. Only one patient complained of moderate radiculopathy at the final visit. No complications were encountered. We introduced a minimally invasive technique to safely remove HNP at the L5-S1 level. sMED is possibly the least invasive technique for HNP removal at the L5-S1 level. © 2011 Japan Society for Endoscopic Surgery, Asia Endosurgery Task Force and Blackwell Publishing Asia Pty Ltd.

  17. Combining various space geodetic techniques for regional modeling of ionospheric electron density over Iran

    NASA Astrophysics Data System (ADS)

    Zare, Saeed; Alizadeh, M. Mahdi; Schuh, Harald

    2017-04-01

    Ionosphere is a layer of the upper atmosphere, between the thermosphere and the exosphere, distinguished because it is ionized by solar radiation. As an important part of human living environment, ionosphere affects our modern society in many ways. International broadcasters use this medium to reflect radio signals back toward the Earth. Ionosphere provides long range capabilities for commercial ship-to-shore communications, for trans-oceanic aircraft links, and for military communication and surveillance systems. Space geodetic techniques have turned into a capable tool for studying the ionosphere in the last decades. Up to now, two dimensional (2-D) models of vertical TEC (VTEC) have been widely developed and used by different communities; however, due to the fact that these models provide information about the integral of the whole electron content along the vertical or slant ray path, these maps are not useful when information about the ionosphere at different altitude is required. The aim of this study is to develop three dimensional (3-D) regional model of electron density by using combination of various space geodetic techniques. B-Spline basis functions are used for longitude and latitude variations of the electron density and Chapman profile function for altitude variations. The National Cartographic Center of Iran (NCC) has established a network of one hundred GPS stations: The Iranian Permanent GPS Network for Geodynamics (IPGN). The main task of the GPS stations is to collect and store raw GPS data and send it to Tehran processing center on a daily basis for final processing. The required data for our investigation are ground based measurements of permanent GPS stations over Iran and radio occultation data from Formosat-3/Cosmic for region of interest. We expect to increase accuracy and reliability of final model by integrating different observation techniques.

  18. Slow ground state molecules from matrix isolation sublimation

    NASA Astrophysics Data System (ADS)

    Oliveira, A. N.; Sacramento, R. L.; Alves, B. X.; Silva, B. A.; Wolff, W.; Cesar, C. L.

    2014-12-01

    We describe the generation and properties of a cryogenic beam of 7Li2 dimers from sublimation of a neon matrix where lithium atoms have been implanted via laser ablation of solid precursors of metallic lithium or lithium hydride (LiH). Different sublimation regimes lead to pulsed molecular beams with different temperatures, densities and forward velocities. With laser absorption spectroscopy these parameters were measured using the molecular 7Li2 (R) transitions A1Σ u+(v\\prime =4,J\\prime =J\\prime\\prime +1) ≤ftarrow X 1Σ g+(v\\prime\\prime =0,J\\prime\\prime =0,1,3). In a typical regime, sublimating a matrix at 16 K, translational temperatures of 6-8 K with a drift velocity of 130 m s-1 in a free expanding pulsed beam with molecular density of 109 cm-3, averaged along the laser axis, were observed. Rotational temperatures around 5-7 K were obtained. In recent experiments we were able to monitor the atomic Li signal—in the D2 line—concomitantly with the molecular signal in order to compare them as a function of the number of ablation pulses. Based on the data and a simple model, we discuss the possibility that a fraction of these molecules are being formed in the matrix, by mating atoms from different ablation pulses, which would open up the way to formation of other more interesting and difficult molecules to be studied at low temperatures. Such a source of cryogenic molecules have possible applications encompassing fundamental physics tests, quantum information studies, cold collisions, chemistry, and trapping.

  19. Sublimation of ices of astrophysical interest: A bibliographic review

    NASA Astrophysics Data System (ADS)

    Fray, N.; Schmitt, B.

    2009-12-01

    The sublimation and condensation of ices play a very important role in the formation of planetary systems, in the evolution of some solar system bodies as well as in the equilibrium and matter exchanges between surface and atmosphere of most planets and satellites. The precise knowledge of vapour pressure of molecular solids at all relevant temperatures is mandatory, but the published sublimation relations are not always accurate enough. All published experimental measurements, and empirical and thermodynamical relations for the vapour pressure of 53 different species in their pure solid phases are reviewed. For several species, we also calculate the vapour pressure with accurate thermodynamic formulae from the triple point down to low temperatures. For 27 species (H 2O, O 2, O 3, CO, CO 2, CH 3OH, HCOOH, CH 4, C 2H 2, C 2H 4, C 2H 6, C 6H 6, HCN, HC 3N, C 2N 2, C 4N 2, N 2, NH 3, NO, N 2O, H 2S, SO 2, AsH 3, Ne, Ar, Kr, and Xe) we are able to propose vapour pressure relations, either empirical or theoretical, valid over a large range of temperatures, representative of astrophysical environments. All these relations are more accurate than those currently used in the astrophysical literature. In particular, most of the relations commonly used in the astrophysical literature are based on the data reported by Lide (2006) in the CRC Handbook of Chemistry and Physics, which are inaccurate for several compounds. The most problematic case is CO ice, for which a sublimation relation extrapolated from the liquid-gas equilibrium ( Fanale and Salvail, 1990) is used in most of the models simulating the activity of comet nuclei.

  20. Application of Space Geodetic Techniques and GIS for Crustal Deformation Monitoring in Turkey

    NASA Astrophysics Data System (ADS)

    Ozener, H.; Garagon Dogru, A.; Turgut, B.; Sabuncu, A.

    2011-12-01

    There are number of geodetic techniques for detecting crustal movements. Space-based InSAR technique measures the phase change between two phase measurements of the same ground pixel of the Earth's surface and provides a method to determine crustal deformation. The results are verified by ground-based data obtained from GPS and other seismological studies. The North Anatolian Fault (NAF), particularly western segment of it, has been investigated over two decades by means of GPS technique. It is one of the most seismically active structures in the eastern Mediterranean with a slip rate of 22 mm/year. In this study, current displacement rates obtained from sparse micro-geodetic networks at western part of NAF are presented and then we investigate the potential of InSAR to monitor crustal movements at our study regions. GPS results validate the information coming from InSAR observations. On the other hand,we have some errors due to discrepancy between the GPS and interferometric observations since they are not defining crustal deformation at the same time intervals. After quality control and processing, all datasets integrated into GIS for mapping and analysis.

  1. GGOS-D: A German project on the integration of space geodetic techniques

    NASA Astrophysics Data System (ADS)

    Nothnagel, A.; Rothacher, M.; Angermann, D.; Artz, T.; Bökmann, S.; et al.

    2008-04-01

    Since September 2005 the German Ministry for Research and Education has been funding a group of scientists at GeoForschungsZentrum (GFZ Potsdam), Deutsches Geod¨tisches Forschungsinstitut (DGFI a Munich), Bundesamt f¨ r Kartographie und Geod¨sie (BKG Frankfurt am Main) and Institut f¨ r Geod¨sie u a u a und Geoinformation der Universit¨t Bonn (IGGB Bonn) in a project related to the integration of space a geodetic techniques. These groups comprise experience in GPS, SLR, and VLBI observing techniques as well as in satellite altimetry, global gravity field investigations and large scale combinations. They cooperate with the aim to investigate the production of reference frames and related time series which are consistent across techniques by adapting software packages to common standards and by refining combination procedures. Since the aims of the project closely resemble the general ideas of the GGOS initiative (Global Geodetic Observing System) by the International Association of Geodesy (IAG), the group has gathered under the acronym GGOS-D.

  2. Adhesive coated electrical apparatus having sublimable protective covering and an assembly method

    DOEpatents

    Wootton, Roy E.

    1982-01-01

    Electrical apparatus including an enclosure, an electrode disposed within the enclosure, and supports for insulatably supporting the electrode within the enclosure has a permanently sticky adhesive material which is disposed on the interior surface of the outer enclosure. A high-vapor-pressure sublimable material is disposed on the permanently sticky adhesive material, with the sublimable material capable of subliming away in the presence of a vacuum. The presence of the sublimable material enables the apparatus to be non-sticky during assembly and handling operations, while being rendered sticky upon commissioning of the apparatus.

  3. Latent fingermark visualisation using reduced-pressure sublimation of copper phthalocyanine.

    PubMed

    Williams, Geraint; ap Llwyd Dafydd, Hefin; Watts, Alun; McMurray, Neil

    2011-01-30

    The sublimation of copper phthalocyanine (CuPc) at a temperature of 400°C under conditions of reduced pressure is shown to be an effective method of developing latent fingermarks on certain types of surface. Preliminary experiments on a limited selection of surfaces including paper, plastic and ceramic tiles were carried out using a simple apparatus consisting of a vacuum desiccator and a resistive heater. CuPc from the gas phase condenses preferentially on fingermark deposits, revealing deep blue patterns with excellent ridge detail clarity on light coloured surfaces. The technique is shown to be most effective on porous surfaces such as paper, but relatively ineffective on non-porous ceramic and plastic surfaces.

  4. The Durability of Various Crucible Materials for Aluminum Nitride Crystal growth by Sublimation

    SciTech Connect

    Liu,B.; Edgar, J.; Gu, Z.; Zhuang, D.; Raghothamachar, B.; Dudley, M.; Sarua, A.; Kuball, M.; Meyer, H.

    2004-01-01

    Producing high purity aluminum nitride crystals by the sublimation-recondensation technique is difficult due to the inherently reactive crystal growth environment, normally at temperature in excess of 2100 C. The durability of the furnace fixture materials (crucibles, retorts, etc.) at such a high temperature remains a critical problem. In the present study, the suitability of several refractory materials for AlN crystal growth is investigated, including tantalum carbide, niobium carbide, tungsten, graphite, and hot-pressed boron nitride. The thermal and chemical properties and performance of these materials in inert gas, as well as under AlN crystal growth conditions are discussed. TaC and NbC are the most stable crucible materials with very low elemental vapor pressures in the crystal growth system. Compared with refractory material coated graphite crucibles, HPBN crucible is better for AlN self-seeded growth, as crystals tend to nucleate in thin colorless platelets with low dislocation density.

  5. Sublimation via virtual melting inside an elastoplastic material

    NASA Astrophysics Data System (ADS)

    Levitas, Valery I.; Altukhova, Nataliya

    2009-06-01

    Thermodynamic, kinetic, and mechanical approaches for sublimation inside elastoplastic material via intermediate (virtual) melting under tensile pressure are developed for a spherical nucleus. Virtual melting represents the appearance of subcritical liquid drop that immediately transforms to gas bubble. The variety of mechanisms and transformation paths are revealed in different pressure ranges. The radius of the critical gas nucleus differs from the classical one because elastic energy of melt is size dependent due to surface tension. Our developed approach can be extended for various structural changes in nanoparticles within a void inside elastoplastic material and two-stage and multistage nucleation processes. Universal mechanical gas bubble instability is revealed.

  6. Research on the space-borne coherent wind lidar technique and the prototype experiment

    NASA Astrophysics Data System (ADS)

    Gao, Long; Tao, Yuliang; An, Chao; Yang, Jukui; Du, Guojun; Zheng, Yongchao

    2016-10-01

    Space-borne coherent wind lidar technique is considered as one of the most promising and appropriate remote Sensing methods for successfully measuring the whole global vector wind profile between the lower atmosphere and the middle atmosphere. Compared with other traditional methods, the space-borne coherent wind lidar has some advantages, such as, the all-day operation; many lidar systems can be integrated into the same satellite because of the light-weight and the small size, eye-safe wavelength, and being insensitive to the background light. Therefore, this coherent lidar could be widely applied into the earth climate research, disaster monitoring, numerical weather forecast, environment protection. In this paper, the 2μm space-borne coherent wind lidar system for measuring the vector wind profile is proposed. And the technical parameters about the sub-system of the coherent wind lidar are simulated and the all sub-system schemes are proposed. For sake of validating the technical parameters of the space-borne coherent wind lidar system and the optical off-axis telescope, the weak laser signal detection technique, etc. The proto-type coherent wind lidar is produced and the experiments for checking the performance of this proto-type coherent wind lidar are finished with the hard-target and the soft target, and the horizontal wind and the vertical wind profile are measured and calibrated, respectively. For this proto-type coherent wind lidar, the wavelength is 1.54μm, the pulse energy 80μJ, the pulse width 300ns, the diameter of the off-axis telescope 120mm, the single wedge for cone scanning with the 40°angle, and the two dualbalanced InGaAs detector modules are used. The experiment results are well consisted with the simulation process, and these results show that the wind profile between the vertical altitude 4km can be measured, the accuracy of the wind velocity and the wind direction are better than 1m/s and +/-10°, respectively.

  7. Meteorological conditions associated to high sublimation amounts in semiarid high-elevation Andes decrease the performance of empirical melt models

    NASA Astrophysics Data System (ADS)

    Ayala, Alvaro; Pellicciotti, Francesca; MacDonell, Shelley; McPhee, James; Burlando, Paolo

    2015-04-01

    Empirical melt (EM) models are often preferred to surface energy balance (SEB) models to calculate melt amounts of snow and ice in hydrological modelling of high-elevation catchments. The most common reasons to support this decision are that, in comparison to SEB models, EM models require lower levels of meteorological data, complexity and computational costs. However, EM models assume that melt can be characterized by means of a few index variables only, and their results strongly depend on the transferability in space and time of the calibrated empirical parameters. In addition, they are intrinsically limited in accounting for specific process components, the complexity of which cannot be easily reconciled with the empirical nature of the model. As an example of an EM model, in this study we use the Enhanced Temperature Index (ETI) model, which calculates melt amounts using air temperature and the shortwave radiation balance as index variables. We evaluate the performance of the ETI model on dry high-elevation sites where sublimation amounts - that are not explicitly accounted for the EM model - represent a relevant percentage of total ablation (1.1 to 8.7%). We analyse a data set of four Automatic Weather Stations (AWS), which were collected during the ablation season 2013-14, at elevations between 3466 and 4775 m asl, on the glaciers El Tapado, San Francisco, Bello and El Yeso, which are located in the semiarid Andes of central Chile. We complement our analysis using data from past studies in Juncal Norte Glacier (Chile) and Haut Glacier d'Arolla (Switzerland), during the ablation seasons 2008-09 and 2006, respectively. We use the results of a SEB model, applied to each study site, along the entire season, to calibrate the ETI model. The ETI model was not designed to calculate sublimation amounts, however, results show that their ability is low also to simulate melt amounts at sites where sublimation represents larger percentages of total ablation. In fact, we

  8. Air versus saline in the loss of resistance technique for identification of the epidural space.

    PubMed

    Antibas, Pedro L; do Nascimento Junior, Paulo; Braz, Leandro G; Vitor Pereira Doles, João; Módolo, Norma S P; El Dib, Regina

    2014-07-18

    The success of epidural anaesthesia depends on correct identification of the epidural space. For several decades, the decision of whether to use air or physiological saline during the loss of resistance technique for identification of the epidural space has been governed by the personal experience of the anaesthesiologist. Epidural block remains one of the main regional anaesthesia techniques. It is used for surgical anaesthesia, obstetrical analgesia, postoperative analgesia and treatment of chronic pain and as a complement to general anaesthesia. The sensation felt by the anaesthesiologist from the syringe plunger with loss of resistance is different when air is compared with saline (fluid). Frequently fluid allows a rapid change from resistance to non-resistance and increased movement of the plunger. However, the ideal technique for identification of the epidural space remains unclear. • To evaluate the efficacy and safety of both air and saline in the loss of resistance technique for identification of the epidural space.• To evaluate complications related to the air or saline injected. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 9), MEDLINE, EMBASE and the Latin American and Caribbean Health Science Information Database (LILACS) (from inception to September 2013). We applied no language restrictions. The date of the most recent search was 7 September 2013. We included randomized controlled trials (RCTs) and quasi-randomized controlled trials (quasi-RCTs) on air and saline in the loss of resistance technique for identification of the epidural space. Two review authors independently assessed trial quality and extracted data. We included in the review seven studies with a total of 852 participants. The methodological quality of the included studies was generally ranked as showing low risk of bias in most domains, with the exception of one study, which did not mask participants. We were able to include data from 838

  9. Fresnel zone and reflectarray antennas for space missions: Concepts, computational techniques and characterizations

    NASA Astrophysics Data System (ADS)

    Khayatian, Behrouz

    Reflector antennas generally employ parabolic shaped main reflectors and have found a wide range of applications for both earth stations and satellite systems. Increasingly, one may find many advantages in minimizing antenna shaping requirement and weight as well as more compact designs by employing flat reflectors (either on the main reflector or on the subreflector) which can achieve a desired set of criteria for antenna performance. Two electrically large antennas which use flat min reflectors are Fresnel Zone (FZ) and reflectarray antennas which are being addressed in this dissertation. Analytical techniques are proposed, implemented, and verified to analyze these reflector geometries. A two dimensional (2-D) multi-scatterer analysis is formulated and implemented using various electromagnetic scattering techniques such as Physical Optics (PO), Method of Moments (MoM), and Geometrical Theory of Diffraction (GTD). The capability of the 2-D technique is further extended for dual reflector analysis with flat subreflector panels as well as design and analysis of FZ antennas with a proposed space missions application in solar sailing. FZ antenna design is based on establishing regions of quasi-uniform phases according to the PO current on the reflector face. The concepts extracted from the 2-D analysis of FZ reflectors is carried to the three dimensional (3-D) cases and incorporated into a multi reflector code, which has been widely used in variety of reflector applications. Like FZ antennas, reflectarrays work according to a similar set of principals by achieving a uniform phase current on the flat reflectarray surface. Accordingly, an analytical methodology is proposed and implemented within the structure of the multi-reflector code to analyze and give design criteria for both single and dual reflectarray configurations. This technique is compared to measured results published for single reflectarrays and is investigated for near-field Gregorian reflectarrays with

  10. Contamination of Outer Surfaces of International Space Station Studied by Non-Destructive Techniques

    NASA Astrophysics Data System (ADS)

    Borisov, V. A.; Naumov, S. F.; Sokolova, S. P.; Kurilenok, A. O.; Skurat, V. E.; Zhigach, A. N.; Beriozkina, N. G.; Leipunsky, I. O.; Pshechenkov, P. A.; Zotova, E. S.; Volkov, I. O.; Naumkin, A. V.; Artemov, V. V.

    The aim of this work is to study non -volatile components of contamination deposits on outer surfaces of International Space Station (Russian segment) by a complex of non-destructive techniques - X-ray photoelectron spectroscopy (XPS), diffuse reflection infrared spectroscopy, scanning electron microscopy and local X-ray microanalysis (LXMA). These methods were used for investigation of 40 samples of materials and coatings after their exposure to residual atmosphere of Earth and external conditions of spacecraft. Elemental and chemical composition of surface and sub-surface layers is varied in very broad limits due to concurrence of many processes changing the sample composition. Contamination deposits contain nitrogenous components besides ubiquitous carbonaceous and siliceous components that are typical for spacecraft surface contamination.

  11. Filtered linear forcing: a technique for simulating high Reynolds number turbulence in physical space

    NASA Astrophysics Data System (ADS)

    Palmore, John; Desjardins, Olivier

    2014-11-01

    Low waveshell spectral forcing has been proven to be a simple and effective manner to generate isotropic turbulence in a periodic domain. This simplicity is lost for flow problems with complex boundary conditions such as resolved particle flows, fluid-fluid flows with interfaces, and wall-bounded flows. Lundgren's linear forcing in physical space is a straightforward and easy-to-implement method to tackle these problems; however, the use of this method results in a halving of the large turbulence length scale. The technique that will be presented in this talk applies a low-pass filter to the source term used in linear forcing. It is shown to recover the scale resolution of low waveshell spectral forcing which translates to an approximately 60 percent increase in the attainable Reynolds number for a given computation domain. The characteristics of homogeneous isotropic turbulence generated using filtered linear forcing will be discussed. Finally, extension of this idea to scalar forcing will be presented.

  12. The Application of Electron Microscopy Techniques to the Space Shuttle Columbia Accident Investigation

    NASA Technical Reports Server (NTRS)

    Shah, Sandeep; Jerman, Greg

    2005-01-01

    The Space Shuttle Columbia was returning from a 16-day research mission, STS- 107, with nominal system performance prior to the beginning of the entry interface into earth's upper atmosphere. Approximately one minute and twenty four seconds into the peak heating region of the entry interface, an off-nominal temperature rise was observed in the left main landing gear brake line. Nearly seven minutes later, all contact was lost with Columbia. Debris was observed periodically exiting the Shuttle's flight path throughout the reentry profile over California, Nevada, and New Mexico, until its final breakup over Texas. During the subsequent investigation, electron microscopy techniques were crucial in revealing the location of the fatal damage that resulted in the loss of Columbia and her crew.

  13. A scale space feature based registration technique for fusion of satellite imagery

    NASA Technical Reports Server (NTRS)

    Raghavan, Srini; Cromp, Robert F.; Campbell, William C.

    1997-01-01

    Feature based registration is one of the most reliable methods to register multi-sensor images (both active and passive imagery) since features are often more reliable than intensity or radiometric values. The only situation where a feature based approach will fail is when the scene is completely homogenous or densely textural in which case a combination of feature and intensity based methods may yield better results. In this paper, we present some preliminary results of testing our scale space feature based registration technique, a modified version of feature based method developed earlier for classification of multi-sensor imagery. The proposed approach removes the sensitivity in parameter selection experienced in the earlier version as explained later.

  14. Three-Class EEG-Based Motor Imagery Classification Using Phase-Space Reconstruction Technique

    PubMed Central

    Djemal, Ridha; Bazyed, Ayad G.; Belwafi, Kais; Gannouni, Sofien; Kaaniche, Walid

    2016-01-01

    Over the last few decades, brain signals have been significantly exploited for brain-computer interface (BCI) applications. In this paper, we study the extraction of features using event-related desynchronization/synchronization techniques to improve the classification accuracy for three-class motor imagery (MI) BCI. The classification approach is based on combining the features of the phase and amplitude of the brain signals using fast Fourier transform (FFT) and autoregressive (AR) modeling of the reconstructed phase space as well as the modification of the BCI parameters (trial length, trial frequency band, classification method). We report interesting results compared with those present in the literature by utilizing sequential forward floating selection (SFFS) and a multi-class linear discriminant analysis (LDA), our findings showed superior classification results, a classification accuracy of 86.06% and 93% for two BCI competition datasets, with respect to results from previous studies. PMID:27563927

  15. Planning and scheduling the Hubble Space Telescope: Practical application of advanced techniques

    NASA Technical Reports Server (NTRS)

    Miller, Glenn E.

    1994-01-01

    NASA's Hubble Space Telescope (HST) is a major astronomical facility that was launched in April, 1990. In late 1993, the first of several planned servicing missions refurbished the telescope, including corrections for a manufacturing flaw in the primary mirror. Orbiting above the distorting effects of the Earth's atmosphere, the HST provides an unrivaled combination of sensitivity, spectral coverage and angular resolution. The HST is arguably the most complex scientific observatory ever constructed and effective use of this valuable resource required novel approaches to astronomical observation and the development of advanced software systems including techniques to represent scheduling preferences and constraints, a constraint satisfaction problem (CSP) based scheduler and a rule based planning system. This paper presents a discussion of these systems and the lessons learned from operational experience.

  16. Active cleaning technique for removing contamination from optical surfaces in space

    NASA Technical Reports Server (NTRS)

    Shannon, R. L.; Gillette, R. B.; Cruz, G. A.

    1973-01-01

    An active cleaning technique for removing contaminants from optical surfaces in space was investigated with emphasis on the feasibility of using plasma exposure as a means of in-situ cleaning. The major work accomplished includes: (1) development of an in-situ reflectometer for use in conjunction with the contaminant film deposition/cleaning facility; (2) completion of Apollo Telescope Mount (ATM) filter treatment experiments to assess the effects of plasma exposure on the UV transmittance; (3) attempts to correlate the atomic oxygen flux with cleaning rate; (4) completion of in-situ butadien contamination/plasma cleaning/UV reflectance measurement experiments; (5) carbon cleaning experiments using various gases; (6) completion of silicone contamination/cleaning experiments; and (7) experiments conducted at low chamber pressures to determine cleaning rate distribution and contamination of surfaces adjacent to those being cleaned.

  17. Two Novel Space-Time Coding Techniques Designed for UWB MISO Systems Based on Wavelet Transform.

    PubMed

    Zaki, Amira Ibrahim; Badran, Ehab F; El-Khamy, Said E

    2016-01-01

    In this paper two novel space-time coding multi-input single-output (STC MISO) schemes, designed especially for Ultra-Wideband (UWB) systems, are introduced. The proposed schemes are referred to as wavelet space-time coding (WSTC) schemes. The WSTC schemes are based on two types of multiplexing, spatial and wavelet domain multiplexing. In WSTC schemes, four symbols are transmitted on the same UWB transmission pulse with the same bandwidth, symbol duration, and number of transmitting antennas of the conventional STC MISO scheme. The used mother wavelet (MW) is selected to be highly correlated with transmitted pulse shape and such that the multiplexed signal has almost the same spectral characteristics as those of the original UWB pulse. The two WSTC techniques increase the data rate to four times that of the conventional STC. The first WSTC scheme increases the data rate with a simple combination process. The second scheme achieves the increase in the data rate with a less complex receiver and better performance than the first scheme due to the spatial diversity introduced by the structure of its transmitter and receiver. The two schemes use Rake receivers to collect the energy in the dense multipath channel components. The simulation results show that the proposed WSTC schemes have better performance than the conventional scheme in addition to increasing the data rate to four times that of the conventional STC scheme.

  18. Two Novel Space-Time Coding Techniques Designed for UWB MISO Systems Based on Wavelet Transform

    PubMed Central

    Zaki, Amira Ibrahim; El-Khamy, Said E.

    2016-01-01

    In this paper two novel space-time coding multi-input single-output (STC MISO) schemes, designed especially for Ultra-Wideband (UWB) systems, are introduced. The proposed schemes are referred to as wavelet space-time coding (WSTC) schemes. The WSTC schemes are based on two types of multiplexing, spatial and wavelet domain multiplexing. In WSTC schemes, four symbols are transmitted on the same UWB transmission pulse with the same bandwidth, symbol duration, and number of transmitting antennas of the conventional STC MISO scheme. The used mother wavelet (MW) is selected to be highly correlated with transmitted pulse shape and such that the multiplexed signal has almost the same spectral characteristics as those of the original UWB pulse. The two WSTC techniques increase the data rate to four times that of the conventional STC. The first WSTC scheme increases the data rate with a simple combination process. The second scheme achieves the increase in the data rate with a less complex receiver and better performance than the first scheme due to the spatial diversity introduced by the structure of its transmitter and receiver. The two schemes use Rake receivers to collect the energy in the dense multipath channel components. The simulation results show that the proposed WSTC schemes have better performance than the conventional scheme in addition to increasing the data rate to four times that of the conventional STC scheme. PMID:27959939

  19. An in-flight technique for wind measurement in support of the space shuttle program

    NASA Technical Reports Server (NTRS)

    Bjarke, Lisa J.; Ehernberger, L. J.

    1989-01-01

    A technique to use an aircraft to measure wind profiles in the altitude range of 1,500 to 18,200 m was demonstrated at NASA Ames-Dryden. This demonstration was initiated to determine if an aircraft could measure wind profiles in support of space shuttle launches. The Jimsphere balloon is currently the device used to measure pre-launch wind profiles for the space shuttle. However, it takes approximately an hour for the Jimsphere to travel through the altitudes of interest. If these wind instruments could be taken with an aircraft closer to launch in a more timely manner and with the same accuracy as a Jimsphere balloon, some uncertainties in the measurements could be removed. The aircraft used for this investigation was an F-104G which is capable of flight above 18,000 m. It had conventional research instrumentation to provide air data and flow angles along with a ring laser gyro inertial navigation system (INS) to provide inertial and Euler angle data. During the course of 17 flights, wind profiles were measured in 21 climbs and 18 descents. Preliminary comparisons between aircraft measured wind profiles and Jimsphere measured profiles show reasonable agreement (within 3 m/sec). Most large differences between the profiles can usually be explained by large spatial or time differences between the Jimsphere and aircraft measurements, the fact that the aircraft is not in a wings-level attitude, or INS shifts caused by aircraft maneuvering.

  20. Evaluation of available analytical techniques for monitoring the quality of space station potable water

    NASA Technical Reports Server (NTRS)

    Geer, Richard D.

    1989-01-01

    To assure the quality of potable water (PW) on the Space Station (SS) a number of chemical and physical tests must be conducted routinely. After reviewing the requirements for potable water, both direct and indirect analytical methods are evaluated that could make the required tests and improvements compatible with the Space Station operation. A variety of suggestions are made to improve the analytical techniques for SS operation. The most important recommendations are: (1) the silver/silver chloride electrode (SB) method of removing I sub 2/I (-) biocide from the water, since it may interfere with analytical procedures for PW and also its end uses; (2) the orbital reactor (OR) method of carrying out chemistry and electrochemistry in microgravity by using a disk shaped reactor on an orbital table to impart artificial G force to the contents, allowing solution mixing and separation of gases and liquids; and (3) a simple ultra low volume highly sensitive electrochemical/conductivity detector for use with a capillary zone electrophoresis apparatus. It is also recommended, since several different conductivity and resistance measurements are made during the analysis of PW, that the bipolar pulse measuring circuit be used in all these applications for maximum compatibility and redundancy of equipment.

  1. The simulated hospital environment: a qualitative study applying space industry techniques.

    PubMed

    Ayers, Constance J; Binder, Brenda K; Lyon, Karen C; Montgomery, Diane; Koci, Anne; Foster, William A

    2015-01-01

    Patterned after the integrated simulation approach utilized in the space industry, we report results of an innovative simulation in nursing, a 96-hour continuous simulated hospital environment. Training objectives for our study emphasized the integrative and critical thinking skills needed by new graduate nurses. The purpose of this study was to determine the process for development and the experience of participating in a simulated hospital environment. We sought to (a) translate space industry-integrated simulation techniques into development of a simulated hospital environment and (b) determine the experience of participating in an integrated simulation experience among undergraduate (UG) and graduate nursing students and nursing faculty. We used a qualitative mixed-methods design. Data were collected from participant focus groups, debriefing sessions, research team field notes, and electronic health record documentation. The sample, 72 student focus group participants, consisted of 12 baccalaureate-level soon-to-graduate students and 60 graduate nurse practitioner students as patient actors and providers. Important themes emerged from the project. We were able to design a simulated hospital environment that was true to life. Notably, student knowledge-practice gap was a major theme of the study, consistent with studies of employer concerns of new graduate nurses. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Investigation of Techniques for Simulating Communications and Tracking Subsystems on Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Deacetis, Louis A.

    1991-01-01

    The need to reduce the costs of Space Station Freedom has resulted in a major redesign and downsizing of the Station in general, and its Communications and Tracking (C&T) components in particular. Earlier models and simulations of the C&T Space-to-Ground Subsystem (SGS) in particular are no longer valid. There thus exists a general need for updated, high fidelity simulations of C&T subsystems. This project explored simulation techniques and methods that might be used in developing new simulations of C&T subsystems, including the SGS. Three requirements were placed on the simulations to be developed: (1) they run on IBM PC/XT/AT compatible computers; (2) they be written in Ada as much as possible; and (3) since control and monitoring of the C&T subsystems will involve communication via a MIL-STD-1553B serial bus, that the possibility of commanding the simulator and monitoring its sensors via that bus be included in the design of the simulator. The result of the project is a prototype of a simulation of the Assembly/Contingency Transponder of the SGS, written in Ada, which can be controlled from another PC via a MIL-STD-1553B bus.

  3. Measuring enthalpy of sublimation of volatiles by means of micro-thermogravimetry for the study of water and organic in planetary environments

    NASA Astrophysics Data System (ADS)

    Dirri, F.; Palomba, E.; Longobardo, A.; Zampetti, E.; Biondi, D.; Boccaccini, A.; Pantalei, S.; Zinzi, A.

    In this work, we present a new experimental set up to infer the enthalpy of sublimation for a known specie of dicarboxylic acid, i.e. adipic acid. This type of acids, with various concentrations are present in different environments (e.g. marine, rural, urban). The experiment is performed in the framework of the VISTA (Volatile In Situ Thermogravimetry Analyser) project, an instrument currently under study for the ESA Cosmic Vision proposed mission MarcoPolo-R. The enthalpy of sublimation of adipic acid was measured by means of micro-thermogravimetric analysis (mu -TGA), a widely used technique to investigate condensation/sublimation and absorption/desorption processes of volatile compounds. The measurements were performed with a 10 MHz temperature controlled piezoelectric crystal microbalance (PCM), placed in a vacuum chamber (10-6 mbar). The obtained enthalpy of sublimation is (123±16) kJ× mol-1, a value in good agreement with literature within 10%. This result (connected to the deposition rate curve, from 30 o to 75 oC), demonstrates the capability of our device to perform this kind of measurements.

  4. D/H fractionation during the sublimation of water ice

    NASA Astrophysics Data System (ADS)

    Lécuyer, Christophe; Royer, Aurélien; Fourel, François; Seris, Magali; Simon, Laurent; Robert, François

    2017-03-01

    Experiments of sublimation of pure water ice have been performed in the temperature range -105 °C to -30 °C and atmospheric partial pressures ranging from 10-6 to 10-1 mb. Sampling of both vapour and residual ice fractions has been performed with the use of a vacuum line designed for the extraction and purification of gases before the measurement of their D/H ratios. Sublimation was responsible for sizable isotopic fractionation factors in the range 0.969-1.123 for temperatures lying between -105 °C and -30 °C. The fractionation factor exhibits a cross-over at temperatures around -50 °C with the water vapour fraction being D-depleted relative to the residual ice fraction at T < -50 °C (αice-vapour = 0.969-0.995). This cross-over has implications for the understanding of the atmospheric water cycle of some terrestrial planets such as the Earth or Mars. The magnitude of deuterium enrichment or depletion between ice and water vapour cannot explain the differences in the D/H ratios amongst Jupiter comets and long-period comets families nor those that have been documented between Earth's and cometary water.

  5. Dynamic sublimation pressure and the catastrophic breakup of Comet ISON

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan K.; Johnson, Brandon C.; Bowling, Timothy; Jay Melosh, H.; Minton, David; Lisse, Carey M.; Battams, Karl

    2015-09-01

    Previously proposed mechanisms have difficulty explaining the disruption of Comet C/2012 S1 (ISON) as it approached the Sun. We describe a novel cometary disruption mechanism whereby comet nuclei fragment and disperse through dynamic sublimation pressure, which induces differential stresses within the interior of the nucleus. When these differential stresses exceed its material strength, the nucleus breaks into fragments. We model the sublimation process thermodynamically and propose that it is responsible for the disruption of Comet ISON. We estimate the bulk unconfined crushing strength of Comet ISON's nucleus and the resulting fragments to be 0.5 Pa and 1-9 Pa, respectively, assuming typical Jupiter Family Comet (JFC) albedos. However, if Comet ISON has an albedo similar to Pluto, this strength estimate drops to 0.2 Pa for the intact nucleus and 0.6-4 Pa for its fragments. Regardless of assumed albedo, these are similar to previous strength estimates of JFCs. This suggests that, if Comet ISON is representative of dynamically new comets, then low bulk strength is a primordial property of some comet nuclei, and not due to thermal processing during migration into the Jupiter Family.

  6. The Heat of Sublimation of Solid Ethylene and Acetylene

    NASA Astrophysics Data System (ADS)

    Nelson, R. N.; Allen, J. E., Jr.

    2002-09-01

    The atmospheres of the outer planets and their satellites include trace, but chemically important, amounts of small hydrocarbon molecules. These molecules also appear in solid form in clouds within the atmospheres and as surface layers on the planet or on haze particles in the atmosphere. The modeling of the composition and photochemistry of these atmospheres depends critically on accurate values of the vapor pressure of these hydrocarbons, which in turn requires accurately measured data. It is important to acquire these data over as much of the temperature and pressure range of interest as possible to reduce the need to extrapolate since this can introduce major errors in vapor pressure. In addition to vapor pressures, study of the behavior of solid-vapor equilibrium for small particles, and especially of surface layers, requires information on the heat of sublimation of the solid phases. Ethylene (C2H4) and acetylene (C2H2) are present in the atmospheres of Saturn and Titan, so we previously measured the solid phase vapor pressure of the former from 69 to 97 K (Nelson, Allen, and Harris 1997) and of the latter from 84 to 124 K (Nelson and Allen 1998). We have now refined those data and used them to evaluate the heats of sublimation of these molecules over the same temperature ranges. Nelson, R. N., Allen, J. E., Jr., and Harris, B. C., Jr., 1997, B.A.A.S. 29, 1009 Nelson, R. N. and Allen, J. E., Jr., 1997, B.A.A.S. 30, 1101

  7. Cerium Tetrafluoride: Sublimation, Thermolysis, and Atomic Fluorine Migration.

    PubMed

    Chilingarov, N S; Knot'ko, A V; Shlyapnikov, I M; Mazej, Z; Kristl, M; Sidorov, L N

    2015-08-06

    Saturated vapor pressure p° and enthalpy of sublimation (ΔsH°) of cerium tetrafluoride CeF4 were determined by means of Knudsen effusion mass spectrometry in the range of 750-920 K. It was discovered that sublimation of cerium tetrafluoride from a platinum effusion cell competes with thermal decomposition to CeF3 in the solid phase, but no accompanying release of fluorine to the gas phase occurs. Thus, fluorine atoms migrate within the surface layer of CeF4(s) to the regions of their irreversible drain. We used scanning electron microscopy to study the distribution of the residual CeF3(s) across the inner surface of the effusion cell after complete evaporation of CeF4(s). It was observed that CeF3 accumulates near the edge of the effusion orifice and near the junction of the lid and the body of the cell, that is, in those regions where the fluorine atoms can migrate to a free platinum surface and thus be depleted from the system. Distribution of CeF3(s) solid particles indicates the ways of fluorine atoms migration providing CeF3(s) formation inside the CeF4(s) surface layer.

  8. The effect of plasma heating on sublimation-driven flow in Io's atmosphere

    NASA Technical Reports Server (NTRS)

    Wong, Mau C.; Johnson, Robert E.

    1995-01-01

    The atmospheric flow on Io is numerically computed in a flat 2-D axisymmetric geometry for a sublimation atmosphere on the trailing hemisphere subjected to plasma bombardment, UV heating, and IR cooling. Calculations are performed for subsolar vapor pressures of approximately 6.5 x 10(exp -3) Pa (approximately 3 x 10(exp 18) SO2/sq cm) and 6.8 x 10(exp -4) Pa (approximately 4 x 10(exp 17) SO2/sq cm); the latter approximates the vapor pressure of F. P. Fanale et al. (1982). The amount of plasma energy deposited in the atmosphere is 20% of the plasma flow energy due to corotation (J. A. Linker et al., 1988). It is found that plasma heating significantly inflates the upper atmosphere, increasing both the exobase altitude and the amount of surface covered by more than an exospheric column of gas. This in turn controls the supply of the Io plasma torus (M. A. McGrath and R. E. Johnson, 1987). The horizontal flow of mass and energy is also important in determining the exobase altitude; and it is shown that IR cooling can be important, although our use of the equilibrium, cool-to-space approximation for a pure SO2 gas (E. Lellouch et al., 1992) may overestimate this effect. The calculated exobase altitudes are somewhat lower than those suggested by McGrath and Johnson (1987) for supplying the torus, indicating the details of the plasma energy deposition and sputter ejection rate near the exobase, as well as the IR emission from this region need to be examined. In addition, the molecules sublimed (or sputtered) from the surface are transported to the exobase in times short compared to the molecular photodissociation time. Therefore, the exobase is dominated by molecular species and the exobase is supplied by a small region of the surface.

  9. Study of Ice Particle Formation and Lifetime in Space Environment

    NASA Technical Reports Server (NTRS)

    Jeng, D.

    1972-01-01

    The ice particles are formed when liquid and/or humid gases vent to the space. These submicroscopic ice particles are potential contamination sources of the environments during Skylab operations. The critical size of ice particle and its nucleation rate based on the theory of homogeneous and heterogeneous nucleation by sublimation are analyzed. The equations which are pertinent for studying the growth and evaporation of the ice particles are formulated. The mechanisms affecting the lifetime of ice particle are discussed. The gas dynamic techniques for experimental study of ice particle formation are proposed.

  10. Expansion Techniques of Embedding Audio Watermark Data Rate for Constructing Ubiquitous Acoustic Spaces

    NASA Astrophysics Data System (ADS)

    Modegi, Toshio

    We are proposing “Ubiquitous Acoustic Spaces”, where each sound source can emit some address information with audio signals and make us automatically access to its related cyber space, using handheld devices such as cellphones. In order to realize this concept, we have considered three types of extraction methods, which were an acoustic modulation, an audio fingerprint, and an audio watermark technique. Then we have proposed a novel audio watermarking technique, which enables contactless asynchronous detection of embedded audio watermarks through speaker and microphone devices. However its embedding data rate was around 10 [bps], which was not sufficient for embedding generally used URL address texts. Therefore, we have extended the embedding frequency range and proposed a duplicated embedding algorithm, which uses both previously proposed frequency division method and temporal division method together. By these improvements, possible embedding data rate could be extended to 61.5 [bps], and we could extract watermarks through public telephone networks, even from a cell phone sound source. In this paper, we describe abstracts of our improved watermark embedding and extracting algorithms, and experimental results of watermark extraction precision on several audio signal capturing conditions.

  11. Laboratory instrumentation and techniques for characterizing multi-junction solar cells for space applications

    NASA Technical Reports Server (NTRS)

    Woodyard, James R.

    1995-01-01

    Multi-junction solar cells are attractive for space applications because they can be designed to convert a larger fraction of AMO into electrical power at a lower cost than single-junction cells. The performance of multi-junction cells is much more sensitive to the spectral irradiance of the illuminating source than single-junction cells. The design of high efficiency multi-junction cells for space applications requires matching the optoelectronic properties of the junctions to AMO spectral irradiance. Unlike single-junction cells, it is not possible to carry out quantum efficiency measurements using only a monochromatic probe beam and determining the cell short-circuit current assuming linearity of the quantum efficiency. Additionally, current-voltage characteristics can not be calculated from measurements under non-AMO light sources using spectral-correction methods. There are reports in the literature on characterizing the performance of multi junction cells by measuring and convoluting the quantum efficiency of each junction with the spectral irradiance; the technique is of limited value for the characterization of cell performance under AMO power-generating conditions. We report the results of research to develop instrumentation and techniques for characterizing multi junction solar cells for space . An integrated system is described which consists of a standard lamp, spectral radiometer, dual-source solar simulator, and personal computer based current-voltage and quantum efficiency equipment. The spectral radiometer is calibrated regularly using the tungsten-halogen standard lamp which has a calibration based on NIST scales. The solar simulator produces the light bias beam for current-voltage and cell quantum efficiency measurements. The calibrated spectral radiometer is used to 'fit' the spectral irradiance of the dual-source solar simulator to WRL AMO data. The quantum efficiency apparatus includes a monochromatic probe beam for measuring the absolute cell

  12. Development of a nondestructive vibration technique for bond assessment of Space Shuttle tiles

    NASA Technical Reports Server (NTRS)

    Moslehy, Faissal A.

    1994-01-01

    This final report describes the achievements of the above titled project. The project is funded by NASA-KSC (Grant No. NAG 10-0117) for the period of 1 Jan. to 31 Dec. 1993. The purpose of this project was to develop a nondestructive, noncontact technique based on 'vibration signature' of tile systems to quantify the bond conditions of the thermal protection system) tiles of Space Shuttle orbiters. The technique uses a laser rapid scan system, modal measurements, and finite element modeling. Finite element models were developed for tiles bonded to both clamped and deformable integrated skin-stringer orbiter mid-fuselage. Results showed that the size and location of a disbonded tile can be determined from frequency and mode shape information. Moreover, a frequency response survey was used to quickly identify the disbonded tiles. The finite element results were compared with experimentally determined frequency responses of a 17-tile test panel, where a rapidscan laser system was employed. An excellent degree of correlation between the mathematical simulation and experimental results was realized. An inverse solution for single-tile assemblies was also derived and is being implemented into a computer program that can interact with the modal testing software. The output of the program displays the size and location of disbond. This program has been tested with simulated input (i.e., finite element data), and excellent agreement between predicted and simulated disbonds was shown. Finally, laser vibration imaging and acoustic emission techniques were shown to be well suited for detecting and monitoring the progressive damage in Graphite/Epoxy composite materials.

  13. Long-term crustal deformation monitored by gravity and space geodetic techniques at Medicina

    NASA Astrophysics Data System (ADS)

    Richter, B.; Zerbini, S.; Lago, L.; Romagnoli, C.; Simon, D.

    2003-04-01

    In the framework of an international collaboration, during 1996, at Medicina, Italy, a continuous GPS (CGPS) and a superconducting gravimeter (SG) were installed by the University of Bologna and the Bundesamt fuer Kartographie und Geodaesie, Frankfurt, respectively. The main purpose of the research was the establishment and the demonstration of an observational procedure leading to a reliable estimate of height variations and to interpret gravity variations/changes in conjunction with mass variations/changes within and above the Earth's crust. To fulfill the stated objectives, additional information is needed. In particular, continuous registrations of meteoclimatic parameters such as sacrificial water table level, electrical conductivity and temperature, deep well levels, rainfall, air pressure and temperature and balloon radio sonde data. A comparison, performed over a period of more than six years of data, between the CGPS and SG series has shed light on the existence of relevant seasonal fluctuations in both data sets, quite similar in amplitude and phase. They were interpreted and modeled as the sum of various environmental loadings for the height and gravity series and the Newtonian attraction components for gravity alone. The removal of the observed oscillations is most important in order to estimate properly the long-term trends, which characterize the CGPS and SG series. Moreover, the combination of SG and repeated absolute gravity measurements shows the capability of both techniques to determine the long-term trend in gravity. Just the combined view allows a significant trend analysis. In addition, the CGPS measurements are compared with other geodetic space techniques available at the Medicina station. In total, a strategy has been developed demonstrating how the present day available techniques should be combined to monitor crustal deformations and achieve relevant information for possible causes.

  14. Cylindrical and spherical space equivalents to the plane wave expansion technique of Maxwell's wave equations

    NASA Astrophysics Data System (ADS)

    Gauthier, Robert C.; Alzahrani, Mohammed A.; Jafari, Seyed Hamed

    2015-02-01

    The plane wave expansion (PWM) technique applied to Maxwell's wave equations provides researchers with a supply of information regarding the optical properties of dielectric structures. The technique is well suited for structures that display a linear periodicity. When the focus is directed towards optical resonators and structures that lack linear periodicity the eigen-process can easily exceed computational resources and time constraints. In the case of dielectric structures which display cylindrical or spherical symmetry, a coordinate system specific set of basis functions have been employed to cast Maxwell's wave equations into an eigen-matrix formulation from which the resonator states associated with the dielectric profile can be obtained. As for PWM, the inverse of the dielectric and field components are expanded in the basis functions (Fourier-Fourier-Bessel, FFB, in cylindrical and Fourier- Bessel-Legendre, BLF, in spherical) and orthogonality is employed to form the matrix expressions. The theoretical development details will be presented indicating how certain mathematical complications in the process have been overcome and how the eigen-matrix can be tuned to a specific mode type. The similarities and differences in PWM, FFB and BLF are presented. In the case of structures possessing axial cylindrical symmetry, the inclusion of the z axis component of propagation constant makes the technique applicable to photonic crystal fibers and other waveguide structures. Computational results will be presented for a number of different dielectric geometries including Bragg ring resonators, cylindrical space slot channel waveguides and bottle resonators. Steps to further enhance the computation process will be reported.

  15. Thermodynamic investigations of nitroxoline sublimation by simultaneous DSC-FTIR method and isothermal TG analysis.

    PubMed

    Gao, Gau-Yi; Lin, Shan-Yang

    2010-01-01

    To investigate the physicochemical characteristics, thermodynamics, possible sublimation process and kinetics of nitroxoline, differential scanning calorimetry (DSC), isothermal thermogravimetry (TG), and Fourier transform infrared (FTIR) microspectroscopy equipped with a micro hot-stage of DSC microscopy assembly (simultaneous DSC-FTIR method) were used. The DSC result indicates that nitroxoline exhibited a sharp endothermic peak at 182 degrees C with enthalpy of 103.1 J/g due to the melting point of nitroxoline. A sublimation behavior of nitroxoline was found from 129 degrees C by gradual weight loss in TG curve. However, the nonisothermal DSC-FTIR method reveals that the temperature at 95 degrees C was the onset temperature of nitroxoline sublimation. A significant difference between DSC-FTIR method and TG analysis suggests that the simultaneous DSC-FTIR method was more sensitive than that of the TG analysis to detect the beginning temperature of nitroxoline sublimation. The sublimation kinetics of nitroxoline determined by isothermal TG analysis evidenced that the zero-order kinetics was followed over the sublimation time. The sublimation enthalpy correction was also carried out by a group additivity approach for the estimation of heat capacity. The enthalpy of nitroxoline sublimation estimated was 86.14 KJ/mol at 298.15 K.

  16. Laboratory studies of the growth, sublimation, and light- scattering properties of single levitated ice particles

    NASA Astrophysics Data System (ADS)

    Bacon, Neil Julian

    2001-12-01

    I describe experiments to investigate the properties of microscopic ice particles. The goal of the work was to measure parameters that are important in cloud processes and radiative transfer, using a novel technique that avoids the use of substrates. The experiments were conducted in two separate electrodynamic balance chambers. Single, charged ice particles were formed from frost particles or from droplets frozen either homogeneously or heteroge neously with a bionucleant. The particles were trapped at temperatures between -38°C and -4°C and grown or sublimated according to the temperature gradient in the cham ber. I describe observations of breakup of sublimating frost particles, measurements of light scattering by hexagonal crystals, and observations of the morphology of ice particles grown from frozen water droplets and frost particles. The breaking strength of frost particles was an order of magnitude less than that of bulk ice. Light scattering features not previously observed were analyzed and related to crystal dimension. Initial results from a computer model failed to reproduce these features. The widths of scattering peaks suggest that surface roughness may play a role in determining the angular distribution of scattered light. Ice particle mass evolution was found to be consistent with diffusion- limited growth. Crystals grown slowly from frozen droplets adopted isometric habits, while faster growth resulted in thin side-planes, although there was not an exact correspondence between growth conditions and particle morphology. From the morphological transition, I infer lower limits for the critical supersaturation for layer nucleation on the prism face of 2.4% at -15°C, 4.4% at -20°C, and 3.1% at -25°C. Analytic expressions for the size dependence of facet stability are developed, indicating a strong dependence of stability on both crystal size and surface kinetics, and compared with data. I discuss the role of complex particle morphologies in

  17. Mining potential biomarkers associated with space flight in Caenorhabditis elegans experienced Shenzhou-8 mission with multiple feature selection techniques.

    PubMed

    Zhao, Lei; Gao, Ying; Mi, Dong; Sun, Yeqing

    To identify the potential biomarkers associated with space flight, a combined algorithm, which integrates the feature selection techniques, was used to deal with the microarray datasets of Caenorhabditis elegans obtained in the Shenzhou-8 mission. Compared with the ground control treatment, a total of 86 differentially expressed (DE) genes in responses to space synthetic environment or space radiation environment were identified by two filter methods. And then the top 30 ranking genes were selected by the random forest algorithm. Gene Ontology annotation and functional enrichment analyses showed that these genes were mainly associated with metabolism process. Furthermore, clustering analysis showed that 17 genes among these are positive, including 9 for space synthetic environment and 8 for space radiation environment only. These genes could be used as the biomarkers to reflect the space environment stresses. In addition, we also found that microgravity is the main stress factor to change the expression patterns of biomarkers for the short-duration spaceflight.

  18. Evaluation of hydrocephalus patients with 3D-SPACE technique using variant FA mode at 3T.

    PubMed

    Algin, Oktay

    2017-09-26

    The major advantages of three-dimensional sampling perfection with application optimized contrasts using different flip-angle evolution (3D-SPACE) technique are its high resistance to artifacts that occurs as a result of radiofrequency or static field, the ability of providing images with sub-millimeter voxel size which allows obtaining reformatted images in any plane due to isotropic three-dimensional data with lower specific absorption rate values. That is crucial during examination of cerebrospinal-fluid containing complex structures, and the acquisition time, which is approximately 5 min for scanning of entire cranium. Recent data revealed that T2-weighted (T2W) 3D-SPACE with variant flip-angle mode (VFAM) imaging allows fast and accurate evaluation of the hydrocephalus patients during both pre- and post-operative period for monitoring the treatment. For a better assessment of these patients; radiologists and neurosurgeons should be aware of the details and implications regarding to the 3D-SPACE technique, and they should follow the updates in this field. There could be a misconception about the difference between T2W-VFAM and routine heavily T2W 3D-SPACE images. T2W 3D-SPACE with VFAM imaging is only a subtype of 3D-SPACE technique. In this review, we described the details of T2W 3D-SPACE with VFAM imaging and comprehensively reviewed its recent applications.

  19. HiRISE Images of the Sublimation of the Southern Seasonal Polar Cap of Mars

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; McEwen, A. S.; Okubo, C.; Byrne, S.; Becker, T.; Kieffer, H.; Mellon, M.; HiRISE Team

    2007-12-01

    The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) has returned images with unprecedented resolution of Mars southern seasonal CO2 polar cap. Several high latitude sites were selected for systematic monitoring throughout the spring as the seasonal cap sublimed away. The capability of MRO to turn off-nadir enabled acquisition of stereo pairs to study the topography. HiRISE color capability distinguishes processes involving dust and frost. Color images show evidence of localized migration of frost as dark spots sublimate. Unique landforms are found in the cryptic terrain[1] region of Mars polar cap. These unusual landforms have narrow channels emanating radially, dubbed spiders[2]. Fans of dust blown by the prevailing wind are hypothesized to come from gas jets of CO2 subliming beneath translucent seasonal ice [3]. HiRISE images show a wide variety of morphologies of narrow channels. In some regions deep narrow channels converge radially, while in others the high channel density is more akin to lace. A smooth evolution of one form to another has been observed. Channels converge dendritically, often uphill, consistent with formation by flowing gas, not liquid. More dust fans are observed in regions of spiders than in lace, suggesting that the sublimating gas under the seasonal ice builds up more pressure and can entrain more dust in spidery areas. These differing terrain types are found within a single 6 x 10 km image, which has presumably homogeneous weather, thus a uniform layer of ice and exposure to atmospheric dust. HiRiSE images show that the dust fans tend to emerge from low spots, where the subsurface is accessed, then are blown up and out onto the surface of the seasonal ice. The fans evolve from a thin diffuse covering to thick blankets filling in the narrow channels. We hypothesize that dust collects in the channels, and that these relatively more permeable dust-filled channels form pathways for the next seasons

  20. Calculational criticality analyses of 10- and 20-MW UF[sub 6] freezer/sublimer vessels

    SciTech Connect

    Jordan, W.C.

    1993-02-01

    Calculational criticality analyses have been performed for 10- and 20-MW UF[sub 6] freezer/sublimer vessels. The freezer/sublimers have been analyzed over a range of conditions that encompass normal operation and abnormal conditions. The effects of HF moderation of the UF[sub 6] in each vessel have been considered for uranium enriched between 2 and 5 wt % [sup 235]U. The results indicate that the nuclearly safe enrichments originally established for the operation of a 10-MW freezer/sublimer, based on a hydrogen-to-uranium moderation ratio of 0.33, are acceptable. If strict moderation control can be demonstrated for hydrogen-to-uranium moderation ratios that are less than 0.33, then the enrichment limits for the 10-MW freezer/sublimer may be increased slightly. The calculations performed also allow safe enrichment limits to be established for a 20-NM freezer/sublimer under moderation control.

  1. The SCITEAS experiment: Optical characterizations of sublimating icy planetary analogues

    NASA Astrophysics Data System (ADS)

    Pommerol, A.; Jost, B.; Poch, O.; El-Maarry, M. R.; Vuitel, B.; Thomas, N.

    2015-05-01

    We have designed and built a laboratory facility to investigate the spectro-photometric and morphologic properties of different types of ice-bearing planetary surface analogs and follow their evolution upon exposure to a low pressure and low temperature environment. The results obtained with this experiment are used to verify and improve our interpretations of current optical remote-sensing datasets. They also provide valuable information for the development and operation of future optical instruments. The Simulation Chamber for Imaging the Temporal Evolution of Analogue Samples (SCITEAS) is a small thermal vacuum chamber equipped with a variety of ports and feedthroughs that permit both in-situ and remote characterizations as well as interacting with the sample. A large quartz window located directly above the sample is used to observe its surface from outside with a set of visible and near-infrared cameras. The sample holder can be easily and quickly inserted and removed from the chamber and is compatible with the other measurement facilities of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern. We report here on the results of two of the first experiments performed in the SCITEAS chamber. In the first experiment, fine-grained water ice mixed with dark organic and mineral matter was left to sublime in vacuum and at low temperature, simulating the evolution of the surface of a comet nucleus approaching the Sun. We observed and characterized the formation and evolution of a crust of refractory organic and mineral matter at the surface of the sample and linked the evolution of its structure and texture to its spectro-photometric properties. In the second experiment, a frozen soil was prepared by freezing a mixture of smectite mineral and water. The sample was then left to sublime for 6 h to simulate the loss of volatiles from icy soil at high latitudes on Mars. Colour images were produced using the definitions of the

  2. A centre-triggered magnesium fuelled cathodic arc thruster uses sublimation to deliver a record high specific impulse

    NASA Astrophysics Data System (ADS)

    Neumann, Patrick R. C.; Bilek, Marcela; McKenzie, David R.

    2016-08-01

    The cathodic arc is a high current, low voltage discharge that operates in vacuum and provides a stream of highly ionised plasma from a solid conducting cathode. The high ion velocities, together with the high ionisation fraction and the quasineutrality of the exhaust stream, make the cathodic arc an attractive plasma source for spacecraft propulsion applications. The specific impulse of the cathodic arc thruster is substantially increased when the emission of neutral species is reduced. Here, we demonstrate a reduction of neutral emission by exploiting sublimation in cathode spots and enhanced ionisation of the plasma in short, high-current pulses. This, combined with the enhanced directionality due to the efficient erosion profiles created by centre-triggering, substantially increases the specific impulse. We present experimentally measured specific impulses and jet power efficiencies for titanium and magnesium fuels. Our Mg fuelled source provides the highest reported specific impulse for a gridless ion thruster and is competitive with all flight rated ion thrusters. We present a model based on cathode sublimation and melting at the cathodic arc spot explaining the outstanding performance of the Mg fuelled source. A further significant advantage of an Mg-fuelled thruster is the abundance of Mg in asteroidal material and in space junk, providing an opportunity for utilising these resources in space.

  3. A millimeter wave technique for measuring ice thickness on the Space Shuttle's external tank

    NASA Astrophysics Data System (ADS)

    Kendra, John E.; Ulaby, Fawwaz T.; Wu, Steve

    1991-12-01

    The external fueltank of the Space Shuttle contains extremely lowtemperature propellents. A layer of material known as SOFI (Spray-On Foam Insulation) covering the outside of the fueltank provides thermal insulation between the aluminum surface of the fueltank and the ambient air. In spite of this insulation, under certain conditions ice formation will occur on the surface of the SOFI. Ice on the external fueltank can be detrimental to the launch and it is important to detect its presence and measure its thickness. This paper describes the design of a millimeter-wave radiometer technique developed for this purpose. The design is based on model calculations and measurements of the emission properties of a panel from the external fueltank performed at 35, 94 and 140 GHz. Two sets of measurements were performed, one for the unmodified rough-surface SOFI panel and another for a panel whose surface was sanded down to produce a smooth surface interface with the ice cover. The latter was used to evaluate the results of radiative transfer calculations which are much easier to perform for multilayer structures with plane boundaries. We present experimental evidence demonstrating that the technique developed can accurately predict ice thickness in the case of the smooth-surface SOFI panel. For the original (rough-surface) panel, the emission levels observed were considerably higher than predicted by the model. Both cases however exhibited comparable sensitivities to ice thickness (˜ K/mm at 35 GHz, 4 K/mm at 94 GHz, and 5 K/mm at 140 GHz).

  4. Uranium hexaflouride freezer/sublimer process simulator/trainer

    SciTech Connect

    Carnal, C.L. ); Belcher, J.D.; Tapp, P.A.; Ruppel, F.R.; Wells, J.C. )

    1991-01-01

    This paper describes a software and hardware simulation of a freezer/sublimer unit used in gaseous diffusion processing of uranium hexafluoride (UF{sub 6}). The objective of the project was to build a plant simulator that reads control signals and produces plant signals to mimic the behavior of an actual plant. The model is based on physical principles and process data. Advanced Continuous Simulation Language (ACSL) was used to develop the model. Once the simulation was validated with actual plant process data, the ACSL model was translated into Advanced Communication and Control Oriented Language (ACCOL). A Bristol Babcock Distributed Process Controller (DPC) Model 3330 was the hardware platform used to host the ACCOL model and process the real world signals. The DPC will be used as a surrogate plant to debug control system hardware/software and to train operators to use the new distributed control system without disturbing the process. 2 refs., 4 figs.

  5. Methods of conveying fluids and methods of sublimating solid particles

    DOEpatents

    Turner, Terry D; Wilding, Bruce M

    2013-10-01

    A heat exchanger and associated methods for sublimating solid particles therein, for conveying fluids therethrough, or both. The heat exchanger includes a chamber and a porous member having a porous wall having pores in communication with the chamber and with an interior of the porous member. A first fluid is conveyed into the porous member while a second fluid is conveyed into the porous member through the porous wall. The second fluid may form a positive flow boundary layer along the porous wall to reduce or eliminate substantial contact between the first fluid and the interior of the porous wall. The combined first and second fluids are conveyed out of the porous member. Additionally, the first fluid and the second fluid may each be conveyed into the porous member at different temperatures and may exit the porous member at substantially the same temperature.

  6. Sublimation Model for Formation of Martian Residual Cap Depressions

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Ingersoll, A. P.

    2000-10-01

    In an effort for explain the formation of the 'Swiss-cheese' terrain visible on the southern residual cap of Mars, we have developed a radiative model to follow the growth/decay of an initial depression due to sublimation/condensation of carbon dioxide. The pits making up this terrain have many distinctive features, they are shallow ( 10m deep), with steep walls and flat floors and contain an interior moat which runs along the bottom of the walls. They have lateral sizes ranging from a few 10's of meters to a kilometer and are quasi-circular. The model accounts for incident sunlight, emitted thermal radiation, and scattered short and long wave radiation. We have investigated many cases involving pure dry-ice with constant albedo, albedo as a function of insolation, and differing albedo for fresh and residual frost (the latter has lower albedo). The last case mentioned shows the most promising results to date. With these conditions it is possible for the depressions to grow and develop flat central portions although they still lack the observed steep walls of the pits. In the other cases mentioned the initial depressions heal themselves and disappear into the surrounding terrain. Other processes or materials could be responsible for the remainder of the observed features. Water ice stored a few meters under a carbon dioxide covering would have dramatic effects on the growth of any depression which encounters it, both due to its low sublimation rate and its ability to store heat. We will extend the current model to include a water ice layer and account for the subsequent heat storage which could possibly follow. For water ice models, a challenge is to reproduce the low brightness temperatures that persist throughout the summer at the residual south polar cap.

  7. Estimating surface sublimation losses from snowpacks in a mountain catchment using eddy covariance and turbulent transfer calculations

    USDA-ARS?s Scientific Manuscript database

    Sublimation is a critical component of the snow cover mass balance. While sublimation can be directly measured using eddy covariance (EC), such measurements are relatively uncommon in complex mountainous environments. EC measurements of surface snowpack sublimation from three consecutive winter sea...

  8. GPT2: Empirical slant delay model for radio space geodetic techniques

    NASA Astrophysics Data System (ADS)

    Lagler, K.; Schindelegger, M.; BöHm, J.; KráSná, H.; Nilsson, T.

    2013-03-01

    Up to now, state-of-the-art empirical slant delay modeling for processing observations from radio space geodetic techniques has been provided by a combination of two empirical models. These are GPT (Global Pressure and Temperature) and GMF (Global Mapping Function), both operating on the basis of long-term averages of surface values from numerical weather models. Weaknesses in GPT/GMF, specifically their limited spatial and temporal variability, are largely eradicated by a new, combined model GPT2, which provides pressure, temperature, lapse rate, water vapor pressure, and mapping function coefficients at any site, resting upon a global 5° grid of mean values, annual, and semi-annual variations in all parameters. Built on ERA-Interim data, GPT2 brings forth improved empirical slant delays for geophysical studies. Compared to GPT/GMF, GPT2 yields a 40% reduction of annual and semi-annual amplitude differences in station heights with respect to a solution based on instantaneous local pressure values and the Vienna mapping functions 1, as shown with a series of global VLBI (Very Long Baseline Interferometry) solutions.

  9. Application of GFP technique for cytoskeleton visualization onboard the International Space Station

    NASA Astrophysics Data System (ADS)

    Kordyum, E. L.; Shevchenko, G. V.; Yemets, A. I.; Nyporko, A. I.; Blume, Ya. B.

    2005-03-01

    Cytoskeleton recently attracted wide attention of cell and molecular biologists due to its crucial role in gravity sensing and trunsduction. Most of cytoskeletal research is conducted by the means of immunohistochemical reactions, different modifications of which are beneficial for the ground-based experiments. But for the performance onboard the space vehicles, they represent quite complicated technique which requires time and special skills for astronauts. In addition, immunocytochemistry provides only static images of the cytoskeleton arrangement in fixed cells while its localization in living cells is needed for the better understanding of cytoskeletal function. In this connection, we propose a new approach for cytoskeletal visualization onboard the ISS, namely, application of green fluorescent protein (GFP) from Aequorea victoria, which has the unique properties as a marker for protein localization in vivo. The creation of chimerical protein-GFP gene constructs, obtaining the transformed plant cells possessed protein-GFP in their cytoskeletal composition will allow receiving a simple and efficient model for screening of the cytoskeleton functional status in microgravity.

  10. Application of GFP technique for cytoskeleton visualization onboard the International Space Station.

    PubMed

    Kordyum, E L; Shevchenko, G V; Yemets, A I; Nyporko, A I; Blume, Ya B

    2005-03-01

    Cytoskeleton recently attracted wide attention of cell and molecular biologists due to its crucial role in gravity sensing and trunsduction. Most of cytoskeletal research is conducted by the means of immunohistochemical reactions, different modifications of which are beneficial for the ground-based experiments. But for the performance onboard the space vehicles, they represent quite complicated technique which requires time and special skills for astronauts. In addition, immunocytochemistry provides only static images of the cytoskeleton arrangement in fixed cells while its localization in living cells is needed for the better understanding of cytoskeletal function. In this connection, we propose a new approach for cytoskeletal visualization onboard the ISS, namely, application of green fluorescent protein (GFP) from Aequorea victoria, which has the unique properties as a marker for protein localization in vivo. The creation of chimerical protein-GFP gene constructs, obtaining the transformed plant cells possessed protein-GFP in their cytoskeletal composition will allow receiving a simple and efficient model for screening of the cytoskeleton functional status in microgravity.

  11. Evaluation of the soil moisture prediction accuracy of a space radar using simulation techniques. [Kansas

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T. (Principal Investigator); Dobson, M. C.; Stiles, J. A.; Moore, R. K.; Holtzman, J. C.

    1981-01-01

    Image simulation techniques were employed to generate synthetic aperture radar images of a 17.7 km x 19.3 km test site located east of Lawrence, Kansas. The simulations were performed for a space SAR at an orbital altitude of 600 km, with the following sensor parameters: frequency = 4.75 GHz, polarization = HH, and angle of incidence range = 7 deg to 22 deg from nadir. Three sets of images were produced corresponding to three different spatial resolutions; 20 m x 20 m with 12 looks, 100 m x 100 m with 23 looks, and 1 km x 1 km with 1000 looks. Each set consisted of images for four different soil moisture distributions across the test site. Results indicate that, for the agricultural portion of the test site, the soil moisture in about 90% of the pixels can be predicted with an accuracy of = + or - 20% of field capacity. Among the three spatial resolutions, the 1 km x 1 km resolution gave the best results for most cases, however, for very dry soil conditions, the 100 m x 100 m resolution was slightly superior.

  12. Assessing Hurricane Katrina Vegetation Damage at Stennis Space Center using IKONOS Image Classification Techniques

    NASA Technical Reports Server (NTRS)

    Spruce, Joseph P.; Ross, Kenton W.; Graham, William D.

    2006-01-01

    Hurricane Katrina inflicted widespread damage to vegetation in southwestern coastal Mississippi upon landfall on August 29, 2005. Storm damage to surface vegetation types at the NASA John C. Stennis Space Center (SSC) was mapped and quantified using IKONOS data originally acquired on September 2, 2005, and later obtained via a Department of Defense ClearView contract. NASA SSC management required an assessment of the hurricane s impact to the 125,000-acre buffer zone used to mitigate rocket engine testing noise and vibration impacts and to manage forestry and fire risk. This study employed ERDAS IMAGINE software to apply traditional classification techniques to the IKONOS data. Spectral signatures were collected from multiple ISODATA classifications of subset areas across the entire region and then appended to a master file representative of major targeted cover type conditions. The master file was subsequently used with the IKONOS data and with a maximum likelihood algorithm to produce a supervised classification later refined using GIS-based editing. The final results enabled mapped, quantitative areal estimates of hurricane-induced damage according to general surface cover type. The IKONOS classification accuracy was assessed using higher resolution aerial imagery and field survey data. In-situ data and GIS analysis indicate that the results compare well to FEMA maps of flooding extent. The IKONOS classification also mapped open areas with woody storm debris. The detection of such storm damage categories is potentially useful for government officials responsible for hurricane disaster mitigation.

  13. Assessing Hurricane Katrina Vegetation Damage at Stennis Space Center using IKONOS Image Classification Techniques

    NASA Technical Reports Server (NTRS)

    Spruce, Joseph P.; Ross, Kenton W.; Graham, William D.

    2006-01-01

    Hurricane Katrina inflicted widespread damage to vegetation in southwestern coastal Mississippi upon landfall on August 29, 2005. Storm damage to surface vegetation types at the NASA John C. Stennis Space Center (SSC) was mapped and quantified using IKONOS data originally acquired on September 2, 2005, and later obtained via a Department of Defense ClearView contract. NASA SSC management required an assessment of the hurricane s impact to the 125,000-acre buffer zone used to mitigate rocket engine testing noise and vibration impacts and to manage forestry and fire risk. This study employed ERDAS IMAGINE software to apply traditional classification techniques to the IKONOS data. Spectral signatures were collected from multiple ISODATA classifications of subset areas across the entire region and then appended to a master file representative of major targeted cover type conditions. The master file was subsequently used with the IKONOS data and with a maximum likelihood algorithm to produce a supervised classification later refined using GIS-based editing. The final results enabled mapped, quantitative areal estimates of hurricane-induced damage according to general surface cover type. The IKONOS classification accuracy was assessed using higher resolution aerial imagery and field survey data. In-situ data and GIS analysis indicate that the results compare well to FEMA maps of flooding extent. The IKONOS classification also mapped open areas with woody storm debris. The detection of such storm damage categories is potentially useful for government officials responsible for hurricane disaster mitigation.

  14. New Algorithms for Estimating Spacecraft Position Using Scanning Techniques for Deep Space Network Antennas

    NASA Technical Reports Server (NTRS)

    Chen, Lingli; Fathpour, Nanaz; Mehra, Raman K.

    2005-01-01

    As more and more nonlinear estimation techniques become available, our interest is in finding out what performance improvement, if any, they can provide for practical nonlinear problems that have been traditionally solved using linear methods. In this paper we examine the problem of estimating spacecraft position using conical scan (conscan) for NASA's Deep Space Network antennas. We show that for additive disturbances on antenna power measurement, the problem can be transformed into a linear one, and we present a general solution to this problem, with the least square solution reported in literature as a special case. We also show that for additive disturbances on antenna position, the problem is a truly nonlinear one, and we present two approximate solutions based on linearization and Unscented Transformation respectively, and one 'exact' solution based on Markov Chain Monte Carlo (MCMC) method. Simulations show that, with the amount of data collected in practice, linear methods perform almost the same as MCMC methods. It is only when we artificially reduce the amount of collected data and increase the level of noise that nonlinear methods show significantly better accuracy than that achieved by linear methods, at the expense of more computation.

  15. The Deflection Plate Analyzer: A Technique for Space Plasma Measurements Under Highly Disturbed Conditions

    NASA Technical Reports Server (NTRS)

    Wright, Kenneth H., Jr.; Dutton, Ken; Martinez, Nelson; Smith, Dennis; Stone, Nobie H.

    2004-01-01

    A technique has been developed to measure the characteristics of space plasmas under highly disturbed conditions; e.g., non-Maxwellian plasmas with strong drifting populations and plasmas contaminated by spacecraft outgassing. The present method is an extension of the capabilities of the Differential Ion Flux Probe (DIFP) to include a mass measurement that does not include either high voltage or contamination sensitive devices such as channeltron electron multipliers or microchannel plates. This reduces the complexity and expense of instrument fabrication, testing, and integration of flight hardware as compared to classical mass analyzers. The new instrument design is called the Deflection Plate Analyzer (DPA) and can deconvolve multiple ion streams and analyze each stream for ion flux intensity (density), velocity (including direction of motion), mass, and temperature (or energy distribution). The basic functionality of the DPA is discussed. The performance characteristics of a flight instrument as built for an electrodynamic tether mission, the Propulsive Small Expendable Deployer System (ProSEDS), and the instrument s role in measuring key experimental conditions are also discussed.

  16. New Algorithms for Estimating Spacecraft Position Using Scanning Techniques for Deep Space Network Antennas

    NASA Technical Reports Server (NTRS)

    Chen, Lingli; Fathpour, Nanaz; Mehra, Raman K.

    2005-01-01

    As more and more nonlinear estimation techniques become available, our interest is in finding out what performance improvement, if any, they can provide for practical nonlinear problems that have been traditionally solved using linear methods. In this paper we examine the problem of estimating spacecraft position using conical scan (conscan) for NASA's Deep Space Network antennas. We show that for additive disturbances on antenna power measurement, the problem can be transformed into a linear one, and we present a general solution to this problem, with the least square solution reported in literature as a special case. We also show that for additive disturbances on antenna position, the problem is a truly nonlinear one, and we present two approximate solutions based on linearization and Unscented Transformation respectively, and one 'exact' solution based on Markov Chain Monte Carlo (MCMC) method. Simulations show that, with the amount of data collected in practice, linear methods perform almost the same as MCMC methods. It is only when we artificially reduce the amount of collected data and increase the level of noise that nonlinear methods show significantly better accuracy than that achieved by linear methods, at the expense of more computation.

  17. Space Shuttle propulsion parameter estimation using optimal estimation techniques, volume 1

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The mathematical developments and their computer program implementation for the Space Shuttle propulsion parameter estimation project are summarized. The estimation approach chosen is the extended Kalman filtering with a modified Bryson-Frazier smoother. Its use here is motivated by the objective of obtaining better estimates than those available from filtering and to eliminate the lag associated with filtering. The estimation technique uses as the dynamical process the six degree equations-of-motion resulting in twelve state vector elements. In addition to these are mass and solid propellant burn depth as the ""system'' state elements. The ""parameter'' state elements can include aerodynamic coefficient, inertia, center-of-gravity, atmospheric wind, etc. deviations from referenced values. Propulsion parameter state elements have been included not as options just discussed but as the main parameter states to be estimated. The mathematical developments were completed for all these parameters. Since the systems dynamics and measurement processes are non-linear functions of the states, the mathematical developments are taken up almost entirely by the linearization of these equations as required by the estimation algorithms.

  18. Novel Electric Nucleation Technique for Growing Large Single Crystal in Space

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin; Frazier, Donald O.

    1999-01-01

    We present, herein, an electrical model for growing crystals without a seed which might not be free of defects and thereby still hinder the growth of a perfect crystal in space. The system is designed to confine nucleation to a single site automatically in an under saturated solution to avoid multiple nucleation. The technique is based on the effect of electrostriction, which is the tendency of a material to become more compressed in the presence of an electric field. The system is designed to create an electrical potential well between two hyperboloid electrodes with applied voltage at low frequency. The induced potential well between the electrodes oscillates at low frequency and attracts the solute and condenses it into the region of maximum field intensity. The alternating voltage prevents molecules with intrinsic charge from being attracted to the electrodes. The continuous presence of the electric field during the duration of the experiment, provides a continuous migration of the molecules toward the trapping site. This will eliminate the creation of a depletion region around the nucleation center and will enhance the crystal growth rate. Aside from the above mentioned advantages, the system is compact, safe to operate, and inexpensive to build.

  19. Operational modal analysis via image based technique of very flexible space structures

    NASA Astrophysics Data System (ADS)

    Sabatini, Marco; Gasbarri, Paolo; Palmerini, Giovanni B.; Monti, Riccardo

    2013-08-01

    Vibrations represent one of the most important topics of the engineering design relevant to flexible structures. The importance of this problem increases when a very flexible system is considered, and this is often the case of space structures. In order to identify the modal characteristics, in terms of natural frequencies and relevant modal parameters, ground tests are performed. However, these parameters could vary due to the operative conditions of the system. In order to continuously monitor the modal characteristics during the satellite lifetime, an operational modal analysis is mandatory. This kind of analysis is usually performed by using classical accelerometers or strain gauges and by properly analyzing the acquired output. In this paper a different approach for the vibrations data acquisition will be performed via image-based technique. In order to simulate a flexible satellite, a free flying platform is used; the problem is furthermore complicated by the fact that the overall system, constituted by a highly rigid bus and very flexible panels, must necessarily be modeled as a multibody system. In the experimental campaign, the camera, placed on the bus, will be used to identify the eigenfrequencies of the vibrating structure; in this case aluminum thin plates simulate very flexible solar panels. The structure is excited by a hammer or studied during a fast attitude maneuver. The results of the experimental activity will be investigated and compared with respect to the numerical simulation obtained via a FEM-multibody software and the relevant results will be proposed and discussed.

  20. A Space-Filling Visualization Technique for Multivariate Small World Graphs

    SciTech Connect

    Wong, Pak C.; Foote, Harlan P.; Mackey, Patrick S.; Chin, George; Huang, Zhenyu; Thomas, James J.

    2012-03-15

    We introduce an information visualization technique, known as GreenCurve, for large sparse graphs that exhibit small world properties. Our fractal-based design approach uses spatial cues to approximate the node connections and thus eliminates the links between the nodes in the visualization. The paper describes a sophisticated algorithm to order the neighboring nodes of a large sparse graph by solving the Fiedler vector of its graph Laplacian, and then fold the graph nodes into a space-filling fractal curve based on the Fiedler vector. The result is a highly compact visualization that gives a succinct overview of the graph with guaranteed visibility of every graph node. We show in the paper that the GreenCurve technology is (1) theoretically sustainable by introducing an error estimation metric to measure the fidelity of the new graph representation, (2) empirically rigorous by conducting a usability study to investigate its strengths and weaknesses against the traditional graph layout, and (3) pragmatically feasible by applying it to analyze stressed conditions of the large scale electric power grid on the west coast.

  1. GPT2: Empirical slant delay model for radio space geodetic techniques

    PubMed Central

    Lagler, K; Schindelegger, M; Böhm, J; Krásná, H; Nilsson, T

    2013-01-01

    Up to now, state-of-the-art empirical slant delay modeling for processing observations from radio space geodetic techniques has been provided by a combination of two empirical models. These are GPT (Global Pressure and Temperature) and GMF (Global Mapping Function), both operating on the basis of long-term averages of surface values from numerical weather models. Weaknesses in GPT/GMF, specifically their limited spatial and temporal variability, are largely eradicated by a new, combined model GPT2, which provides pressure, temperature, lapse rate, water vapor pressure, and mapping function coefficients at any site, resting upon a global 5° grid of mean values, annual, and semi-annual variations in all parameters. Built on ERA-Interim data, GPT2 brings forth improved empirical slant delays for geophysical studies. Compared to GPT/GMF, GPT2 yields a 40% reduction of annual and semi-annual amplitude differences in station heights with respect to a solution based on instantaneous local pressure values and the Vienna mapping functions 1, as shown with a series of global VLBI (Very Long Baseline Interferometry) solutions. PMID:25821263

  2. Novel Electric Nucleation Technique for Growing Large Single Crystal in Space

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin; Frazier, Donald O.

    1999-01-01

    We present, herein, an electrical model for growing crystals without a seed which might not be free of defects and thereby still hinder the growth of a perfect crystal in space. The system is designed to confine nucleation to a single site automatically in an under saturated solution to avoid multiple nucleation. The technique is based on the effect of electrostriction, which is the tendency of a material to become more compressed in the presence of an electric field. The system is designed to create an electrical potential well between two hyperboloid electrodes with applied voltage at low frequency. The induced potential well between the electrodes oscillates at low frequency and attracts the solute and condenses it into the region of maximum field intensity. The alternating voltage prevents molecules with intrinsic charge from being attracted to the electrodes. The continuous presence of the electric field during the duration of the experiment, provides a continuous migration of the molecules toward the trapping site. This will eliminate the creation of a depletion region around the nucleation center and will enhance the crystal growth rate. Aside from the above mentioned advantages, the system is compact, safe to operate, and inexpensive to build.

  3. Enhancement of security for free space optics based on reconfigurable chaotic technique

    NASA Astrophysics Data System (ADS)

    Abdulameer, Lwaa F.; Jignesh, Jokhakar D.; Sripati, U.; Kulkarni, Murlidhar

    2013-01-01

    Free Space Optical (FSO) technology offers highly directional, high bandwidth communication channels. This technology can provide fiber-like data rate over short distances. In order to improve security associated with data transmission in FSO networks, a secure communication method based on chaotic technique is presented. In this paper, we have turned our focus on a specific class of piece wise linear one-dimensional chaotic maps. Simulation results indicate that this approach has the advantage of possessing excellent correlation property. In this paper we examine the security vulnerabilities of single FSO links and propose a solution to this problem by implementing the chaotic signal generator "reconfigurable tent map". As synchronization between transmitter and receiver is essential for the correct operation of such schemes, we have also attempted to determine parameters such as auto- and cross-correlation that determine the ease with which synchronization between transmitter and receiver can be achieved. It is demonstrated that cross correlation is very close to zero and auto-correlation is 􀟜-like. The overall system is implemented in the MATLAB Simulink DSP Builder.

  4. Monitoring the Microgravity Environment Quality On-Board the International Space Station Using Soft Computing Techniques

    NASA Technical Reports Server (NTRS)

    Jules, Kenol; Lin, Paul P.

    2001-01-01

    This paper presents an artificial intelligence monitoring system developed by the NASA Glenn Principal Investigator Microgravity Services project to help the principal investigator teams identify the primary vibratory disturbance sources that are active, at any moment in time, on-board the International Space Station, which might impact the microgravity environment their experiments are exposed to. From the Principal Investigator Microgravity Services' web site, the principal investigator teams can monitor via a graphical display, in near real time, which event(s) is/are on, such as crew activities, pumps, fans, centrifuges, compressor, crew exercise, platform structural modes, etc., and decide whether or not to run their experiments based on the acceleration environment associated with a specific event. This monitoring system is focused primarily on detecting the vibratory disturbance sources, but could be used as well to detect some of the transient disturbance sources, depending on the events duration. The system has built-in capability to detect both known and unknown vibratory disturbance sources. Several soft computing techniques such as Kohonen's Self-Organizing Feature Map, Learning Vector Quantization, Back-Propagation Neural Networks, and Fuzzy Logic were used to design the system.

  5. Comparison of loss of resistance technique between Epidrum® and conventional method for identifying the epidural space

    PubMed Central

    Kim, Seon Wook; Kim, Young Mi; Kim, Soo Hwan; Chung, Mi Hwa; Choi, Young Ryong

    2012-01-01

    Background Epidrum® is a recently developed, air operated, loss of resistance (LOR) device for identifying the epidural space. We investigated the usefulness of Epidrum® by comparing it with the conventional LOR technique for identifying the epidural space. Methods One hundred eight American Society of Anesthesiologists (ASA) physical status I or II patients between the ages of 17 and 68 years old and who were scheduled for elective surgery under combined spinal-epidural anesthesia were enrolled in this study. The patients were randomized into two groups: one group received epidural anesthesia by the conventional LOR technique (C group) and the second group received epidural anesthesia using Epidrum® (ED group). While performing epidural anesthesia, the values of variables were recorded, including the number of failures, more than 2 attempts, the incidence of dural puncture, the time needed to locate the epidural space, the distance from the skin to the epidural space and ease of performance, and the satisfaction scores. Results The ED group showed a lower failure rate, fewer cases of more than 2 attempts, a lesser time to identify the epidural space, and better ease and satisfaction scores of procedure than the C group, with statistical significance. Conclusions Using Epidrum® compared to the conventional LOR technique is an easy, rapid, and reliable method for identifying the epidural space. PMID:22558497

  6. Comparison of Epidrum, Epi-Jet, and Loss of Resistance syringe techniques for identifying the epidural space in obstetric patients.

    PubMed

    Kartal, S; Kösem, B; Kılınç, H; Köşker, H; Karabayırlı, S; Çimen, N K; Demircioğlu, R I

    2017-08-01

    Identifying the epidural space is essential during epidural anesthesia (EA). Pressure of the epidural space in pregnancy is higher than that in nonpregnant woman. Loss of resistance (LOR) method is the most commonly preferred method for identifying the epidural space. Epidrum and Epi-Jet are recently innovated supporting devices that facilitate identifying process for epidural space. In this study we aimed to compare Epidrum, Epi-Jet, and LOR methods in identifying the epidural space, feasibility of technique. Two hundred and forty pregnant women who were scheduled for caesarian section surgery under lumbar EA or combined spinal epidural anesthesia (CSEA) were randomized into three groups (Group I Epidrum, n = 80), Group II (Epi-Jet, n = 80), and Group III (LOR, n = 80). We recorded the time required to identify the epidural space and deflation of Epidrum balloon and Epi-Jet syringe, number of attempts, additional methods used to identify epidural space, usefulness of methods, accuracy of identification of epidural space, and outcomes of epidural catheterization. There were no significant differences between the groups with respect to demographic data, duration of deflation of Epidrum balloon and Epi-Jet syringe and distance between skin and epidural space. The mean time required to enter epidural space in Group I was shorter than that in Group II (P = 0.031). Feasibility of Epi-Jet was easier than that of Epidrum (P = 0.015). Number of uncertainties of epidural space identification was higher in Group I than that in Group II (P = 0.009). Also, the requirement for LOR to confirm epidural space and failure rates was higher in Group I than Group II (P < 0.001). We suggest that Epi-Jet is superior to Epidrum in pregnant patients in terms of clarity of epidural space identification, usefulness, and success rates of EA or CSEA.

  7. Modeling the Neutral-Atmosphere Propagation Delay in Radiometric Space Techniques

    NASA Astrophysics Data System (ADS)

    Mendes, Virgilio De Brito

    The propagation delay induced by the electrically-neutral atmosphere has been recognized as the most problematic modeling error for radiometric space geodetic techniques. A mismodeling of this propagation delay affects significantly the height component of position and constitutes therefore a matter of concern in space-geodesy applications, such as sea-level monitoring, postglacial rebound measurement, earthquake-hazard mitigation, and tectonic-plate-margin deformation studies. The neutral-atmosphere propagation delay is commonly considered as composed of two components: a ``hydrostatic'' component, due essentially to the dry gases of the atmosphere, and a ``non-hydrostatic'' component, due to water vapor. Each one can be described as the product of the delay at the zenith and a mapping function, which models the elevation angle dependence of the propagation delay. This dissertation discusses primarily the accuracy of zenith delay prediction models and mapping functions found in the scientific literature. This performance evaluation is based on a comparison against 32,467 benchmark values, obtained by ray tracing one-year's worth of radiosonde profiles from 50 stations distributed worldwide, and comprised different phases: ray-tracing accuracy assessment, model development, and model accuracy assessment. We have studied the sensitivity of the ray-tracing technique to the choice of physical models, processing strategies, and radiosonde instrumentation accuracy. We have concluded that errors in ray tracing can amount to a few centimetres, under special circumstances, but they largely average out for each station's time series of profiles. In order to optimize the performance of the models, we have established databases of the temperature-profile parameters using 50 additional sites, for a total of 100 radiosonde stations. Based on these large databases, we have developed models for lapse rate and tropopause height determination, which have improved significantly the

  8. Characterization of Carbon Dioxide Washout Measurement Techniques in the Mark-III Space Suit

    NASA Technical Reports Server (NTRS)

    Norcross, J.; Bekdash, O.; Meginnis, I.

    2016-01-01

    Providing adequate carbon dioxide (CO2) washout is essential to the reduction of risk in performing suited operations. Long term CO2 exposure can lead to symptoms such as headache, lethargy, dizziness, and in severe cases can lead to unconsciousness and death. Thus maintaining adequate CO2 washout in both ground testing and during in flight EVAs is a requirement of current and future suit designs. It is necessary to understand the inspired CO2 of suit wearers such that future requirements for space suits appropriately address the risk of inadequate washout. Testing conducted by the EVA Physiology Laboratory at the NASA Johnson Space Center aimed to characterize a method for noninvasively measuring inspired oronasal CO2 under pressurized suited conditions in order to better inform requirements definition and verification techniques for future CO2 washout limits in space suits. Prior work conducted by the EPL examined several different wearable, respirator style, masks that could be used to sample air from the vicinity surround the nose and mouth of a suited test subject. Previously published studies utilized these masks, some being commercial products and some novel designs, to monitor CO2 under various exercise and flow conditions with mixed results for repeatability and/or consistency between subjects. Based on a meta-analysis of those studies it was decided to test a nasal cannula as it is a commercially available device that is placed directly in the flow path of the user as they breathe. A nasal cannula was used to sample air inhaled by the test subjects during both rest and exercise conditions. Eight subjects were tasked with walking on a treadmill or operating an arm ergometer to reach target metabolic rates of 1000, 2000, and 3000 BTU/hr. Suit pressure was maintained at 4.3 psid for all tests, with supply flow rates of 6, 4, and 2 actual cubic feet per minute depending on the test condition. Each test configuration was conducted twice with subjects breathing

  9. Assessment of third ventriculostomy patency with the 3D-SPACE technique: a preliminary multicenter research study.

    PubMed

    Algin, Oktay; Ucar, Murat; Ozmen, Evrim; Borcek, Alp Ozgun; Ozisik, Pinar; Ocakoglu, Gokhan; Tali, E Turgut

    2015-06-01

    The goal of this study was to determine the value of the 3D sampling perfection with application-optimized contrasts using different flip-angle evolutions (3D-SPACE) technique in the evaluation of endoscopic third ventriculostomy (ETV) patency. Twenty-six patients with ETV were examined using 3-T MRI units. Sagittal-plane 3D-SPACE with variant flip-angle mode, 3D T1-weighted (T1W), and 3D heavily T2-weighted (T2W) images were obtained with isotropic voxel sizes. Also, sagittal-axial plane phase-contrast cine (PC)-MR images were obtained. The following findings were evaluated: diameters of stoma and third ventricle, flow-void sign on 3D-SPACE and PC-MR images, integrity of the third ventricle on heavily T2W images, and quantitative PC-MRI parameters of the stoma. Obtained sequences were evaluated singly, in combination with one another, and all together. The mean area, flow, and velocity values measured at the level of stoma in patients with patent stoma were significantly higher than those measured in patients with closed stoma (p < 0.05). There was significant correlation among PC-MRI, 3D-SPACE, and 3D heavily T2W techniques regarding assessment of ETV patency (p < 0.001). The 3D-SPACE technique provided the lowest rate of ambiguous results. The 3D-SPACE technique seems to be the most efficient one for determination of ETV patency. The authors suggest the use of 3D-SPACE as a stand-alone first-line sequence in addition to routine brain MRI protocols in assessing patients with ETV, thereby decreasing scan time and reserving the use of a combination of additional sequences such as PC-MRI and 3D heavily T2W images in suspicious or complex cases.

  10. Broadband strong motion simulation in layered half-space using stochastic Green's function technique

    NASA Astrophysics Data System (ADS)

    Hisada, Y.

    2008-04-01

    The stochastic Green’s function method, which simulates one component of the far-field S-waves from an extended fault plane at high frequencies (Kamae et al., J Struct Constr Eng Trans AIJ, 430:1 9, 1991), is extended to simulate the three components of the full waveform in layered half-spaces for broadband frequency range. The method firstly computes ground motions from small earthquakes, which correspond to the ruptures of sub-faults on a fault plane of a large earthquake, and secondly constructs the strong motions of the large earthquake by superposing the small ground motions using the empirical Green’s function technique (e.g., Irikura, Proc 7th Japan Earthq Eng Symp, 151 156, 1986). The broadband stochastic omega-square model is proposed as the moment rate functions of the small earthquakes, in which random and zero phases are used at higher and lower frequencies, respectively. The zero phases are introduced to simulate a smooth ramp function of the moment function with the duration of 1/fc s (fc: the corner frequency) and to reproduce coherent strong motions at low frequencies (i.e., the directivity pulse). As for the radiation coefficients, the theoretical values of double couple sources for lower frequencies and the theoretical isotropic values for the P-, SV-, and SH-waves (Onishi and Horike, J Struct Constr Eng Trans AIJ, 586:37 44, 2004) for high frequencies are used. The proposed method uses the theoretical Green’s functions of layered half-spaces instead of the far-field S-waves, which reproduce the complete waves including the direct and reflected P- and S-waves and surface waves at broadband frequencies. Finally, the proposed method is applied to the 1994 Northridge earthquake, and results show excellent agreement with the observation records at broadband frequencies. At the same time, the method still needs improvements especially because it underestimates the high-frequency vertical components in the near fault range. Nonetheless, the method

  11. Spatial Field Variability Mapping of Rice Crop using Clustering Technique from Space Borne Hyperspectral Data

    NASA Astrophysics Data System (ADS)

    Moharana, S.; Dutta, S.

    2015-12-01

    Precision farming refers to field-specific management of an agricultural crop at a spatial scale with an aim to get the highest achievable yield and to achieve this spatial information on field variability is essential. The difficulty in mapping of spatial variability occurring within an agriculture field can be revealed by employing spectral techniques in hyperspectral imagery rather than multispectral imagery. However an advanced algorithm needs to be developed to fully make use of the rich information content in hyperspectral data. In the present study, potential of hyperspectral data acquired from space platform was examined to map the field variation of paddy crop and its species discrimination. This high dimensional data comprising 242 spectral narrow bands with 30m ground resolution Hyperion L1R product acquired for Assam, India (30th Sept and 3rd Oct, 2014) were allowed for necessary pre-processing steps followed by geometric correction using Hyperion L1GST product. Finally an atmospherically corrected and spatially deduced image consisting of 112 band was obtained. By employing an advanced clustering algorithm, 12 different clusters of spectral waveforms of the crop were generated from six paddy fields for each images. The findings showed that, some clusters were well discriminated representing specific rice genotypes and some clusters were mixed treating as a single rice genotype. As vegetation index (VI) is the best indicator of vegetation mapping, three ratio based VI maps were also generated and unsupervised classification was performed for it. The so obtained 12 clusters of paddy crop were mapped spatially to the derived VI maps. From these findings, the existence of heterogeneity was clearly captured in one of the 6 rice plots (rice plot no. 1) while heterogeneity was observed in rest of the 5 rice plots. The degree of heterogeneous was found more in rice plot no.6 as compared to other plots. Subsequently, spatial variability of paddy field was

  12. Sublimation characterization and vapor pressure estimation of an HIV nonnucleoside reverse transcriptase inhibitor using thermogravimetric analysis.

    PubMed

    Xie, Minli; Ziemba, Theresa M; Maurin, Michael B

    2003-01-01

    The purpose of this research is to investigate the sublimation process of DPC 963, a second-generation nonnucleoside reverse transcriptase inhibitor for HIV-1 retrovirus, and to better understand the effect of sublimation during active pharmaceutical ingredient (API) manufacture and formulation development, especially the drying processes. Sublimation of DPC 963 at 150 degrees C and above was determined by thermogravimetric analysis-Fourier transform infrared (TGA-FTIR). The rates of sublimation at different temperatures were measured using isothermal TGA. Condensed material was collected and analyzed by differential scanning calorimetry (DSC), x-ray powder diffraction (XRPD), and infrared (IR) spectrometry. Benzoic acid was used as a reference standard to derive a linear logarithmic relationship between sublimation/evaporation rate and vapor pressure specific to the TGA system used in this study. Sublimation and evaporation of DPC 963 were found to follow apparent zero-order kinetics. Using the Eyring equation, the enthalpy and entropy of the sublimation and evaporation processes were obtained. The enthalpies of sublimation and evaporation were found to be 29 and 22 kcal/mol, respectively. The condensed material from the vapor phase was found to exist in 2 physical forms, amorphous and crystalline. Using benzoic acid as a reference standard, vapor pressure of DPC 963 at different temperatures was calculated using the linear logarithmic relationship obtained. DPC 963 undergoes sublimation at appreciable rates at 150 degrees C and above but this is not likely to pose a serious issue during the manufacturing process. Vapor pressure estimation using thermogravimetric analysis provided sufficient accuracy to be used as a fast, simple, and safe alternative to the traditional methods of vapor pressure determination.

  13. Explorations of Space-Charge Limits in Parallel-Plate Diodes and Associated Techniques for Automation

    NASA Astrophysics Data System (ADS)

    Ragan-Kelley, Benjamin

    Space-charge limited flow is a topic of much interest and varied application. We extend existing understanding of space-charge limits by simulations, and develop new tools and techniques for doing these simulations along the way. The Child-Langmuir limit is a simple analytic solution for space-charge limited current density in a one-dimensional diode. It has been previously extended to two dimensions by numerical calculation in planar geometries. By considering an axisymmetric cylindrical system with axial emission from a circular cathode of finite radius r and outer drift tube R > r and gap length L, we further examine the space charge limit in two dimensions. We simulate a two-dimensional axisymmetric parallel plate diode of various aspect ratios (r/L), and develop a scaling law for the measured two-dimensional space-charge limit (2DSCL) relative to the Child-Langmuir limit as a function of the aspect ratio of the diode. These simulations are done with a large (100T) longitudinal magnetic field to restrict electron motion to 1D, with the two-dimensional particle-in-cell simulation code OOPIC. We find a scaling law that is a monotonically decreasing function of this aspect ratio, and the one-dimensional result is recovered in the limit as r >> L. The result is in good agreement with prior results in planar geometry, where the emission area is proportional to the cathode width. We find a weak contribution from the effects of the drift tube for current at the beam edge, and a strong contribution of high current-density "wings" at the outer-edge of the beam, with a very large relative contribution when the beam is narrow. Mechanisms for enhancing current beyond the Child-Langmuir limit remain a matter of great importance. We analyze the enhancement effects of upstream ion injection on the transmitted current in a one-dimensional parallel plate diode. Electrons are field-emitted at the cathode, and ions are injected at a controlled current from the anode. An analytic

  14. Inspection of Space Station Cold Plate Using Visual and Automated Holographic Techniques

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.; Melis, Matthew E.; Weiland, Kenneth E.

    1999-01-01

    Real-time holography has been used to confirm the presence of non-uniformity in the construction of an International Space Station cold plate. Ultrasonic C-scans have previously shown suspected areas of cooling fin disbonds. But both neural-net processed and visual holography did not evidence any progressive permanent changes resulting from 3000 pressurization and relaxation cycles of a Dash 8 cold plate. Neural-net and visual inspections were performed of characteristic patterns generated from electronic time-average holograms of the vibrating cold plate. Normal modes of vibration were excited at very low amplitudes for this purpose, The neural nets were trained to flag very small changes in the mode shapes as encoded in the characteristic patterns. Both the whole cold plate and a zoomed region were inspected. The inspections were conducted before, after, and during pressurization and relaxation cycles of the cold plate. A water-filled cold plate was pressurized to 120 psig (827 kPa) and relaxed for each cycle. Each cycle required 5 seconds. Both the artificial neural networks and the inspectors were unable to detect changes in the mode shapes of the relaxed cold plate. The cold plate was also inspected visually using real-time holography and double-exposure holography. Regions of non-uniformity correlating with the C-scans were apparent, but the interference patterns did not change after 3000 pressurization and relaxation cycles. These tests constituted the first practical application of a neural-net inspection technique developed originally with support from the Director's Discretionary Fund at the Glenn Research Center at Lewis Field.

  15. Conquering space with matter: a technical study of Alberto Burri's materials and techniques

    NASA Astrophysics Data System (ADS)

    Pozzi, Federica; Arslanoglu, Julie; Carò, Federico; Stringari, Carol

    2016-10-01

    Alberto Burri (1915-1995) was a pioneering Italian painter and sculptor. Born in Città di Castello, a small town in the region of Umbria, he earned a medical degree from the University of Perugia. While serving in the Ethiopian campaign and in World War II, first as a frontline soldier and then as a physician, he was captured and sent to a prisoner-of-war camp in Hereford, Texas. It was there that Burri disavowed the medical profession and began to paint. He held a pivotal position in the modern post-war era, exhibiting in Rome and New York in the early 1950s. The present article describes an in-depth scientific investigation of a selection of 14 paintings by Burri, each belonging to one of his series: Sacchi (sacks), Bianchi (whites), Catrami (tars), Muffe (molds), Gobbi (hunchbacks), Legni (woods), Combustioni plastiche (plastic combustions), Ferri (irons), Cretti (monochromatic fields of induced craquelure), and Cellotex (compositions on flayed fiberboard). Elemental information obtained non-invasively via X-ray fluorescence (XRF) spectroscopy was here combined with detailed characterization of the pigments, extenders, binders, and plastics by means of micro-invasive techniques, including pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), Fourier-transform infrared (FTIR) and Raman spectroscopies, and scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) spectroscopy. Through the joint use of traditional artists' materials along with industrial products newly introduced to the market, Burri appears to have encapsulated space into highly dramatic compositions at the boundaries between painting and relief sculpture.

  16. Ice sublimation and rheology - Implications for the Martian polar layered deposits

    NASA Technical Reports Server (NTRS)

    Hofstadter, Mark D.; Murray, Bruce C.

    1990-01-01

    If the sublimation and creep of water ice are important processes in the Martian polar layered deposits, ice-rich scenario formation and evolution schemes must invoke a mechanism for the inhibition of sublimation, such as a dust layer derived from the residue of the sublimating deposits. This layer could be of the order of 1 m in thickness. If the deposits are ice-rich, flows of more than 1 km should have occurred. It is noted that the dust particles in question may be cemented by such ice that may be present, but that impurities may also have served to cement dust particles together even in the absence of ice.

  17. Contamination Effects of Getter Ion and Titanium Sublimation Pumped Systems on Optical Surfaces

    NASA Technical Reports Server (NTRS)

    Visentine, James T.; Richmond, Robert G.

    1973-01-01

    Previous studies have indicated that ultraclean vacuum can be produced when titanium sublimation pumps are used in conjunction with getter-ion pumps. Experiments are described in which the degrees of cleanliness of a typical getter-ion, titanium sublimation-pumped system were monitored by measuring the effects of surface contamination on the reflectance of evaporated vacuum ultraviolet mirrors. Results are presented which indicate that severe reflectance losses occurred when startup of a getter-ion pump was initiated at too high a chamber pressure. Significant reflectance losses also occurred as a result of titanium sublimation-pump operation. These data are reviewed and recommendations for improved system performance are presented.

  18. Sublimation rates of carbon monoxide and carbon dioxide from comets at large heliocentric distances

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    1992-01-01

    Using a simple model for outgassing from a small flat surface area, the sublimation rates of carbon monoxide and carbon dioxide, two species more volatile than water ice that are known to be present in comets, are calculated for a suddenly activated discrete source on the rotating nucleus. The instantaneous sublimation rate depends upon the comet's heliocentric distance and the Sun's zenith angle at the location of the source. The values are derived for the constants of CO and CO2 in an expression that yields the local rotation-averaged sublimation rate as a function of the comet's spin parameters and the source's cometocentric latitude.

  19. Ice sublimation and rheology - Implications for the Martian polar layered deposits

    NASA Technical Reports Server (NTRS)

    Hofstadter, Mark D.; Murray, Bruce C.

    1990-01-01

    If the sublimation and creep of water ice are important processes in the Martian polar layered deposits, ice-rich scenario formation and evolution schemes must invoke a mechanism for the inhibition of sublimation, such as a dust layer derived from the residue of the sublimating deposits. This layer could be of the order of 1 m in thickness. If the deposits are ice-rich, flows of more than 1 km should have occurred. It is noted that the dust particles in question may be cemented by such ice that may be present, but that impurities may also have served to cement dust particles together even in the absence of ice.

  20. Contamination Effects of Getter Ion and Titanium Sublimation Pumped Systems on Optical Surfaces

    NASA Technical Reports Server (NTRS)

    Visentine, James T.; Richmond, Robert G.

    1973-01-01

    Previous studies have indicated that ultraclean vacuum can be produced when titanium sublimation pumps are used in conjunction with getter-ion pumps. Experiments are described in which the degrees of cleanliness of a typical getter-ion, titanium sublimation-pumped system were monitored by measuring the effects of surface contamination on the reflectance of evaporated vacuum ultraviolet mirrors. Results are presented which indicate that severe reflectance losses occurred when startup of a getter-ion pump was initiated at too high a chamber pressure. Significant reflectance losses also occurred as a result of titanium sublimation-pump operation. These data are reviewed and recommendations for improved system performance are presented.

  1. Multiple-image encryption by space multiplexing based on compressive sensing and the double-random phase-encoding technique.

    PubMed

    Deepan, B; Quan, C; Wang, Y; Tay, C J

    2014-07-10

    In this paper, a new multiple-image encryption and decryption technique that utilizes the compressive sensing (CS) concept along with a double-random phase encryption (DRPE) has been proposed. The space multiplexing method is employed for integrating multiple-image data. The method, which results in a nonlinear encryption system, is able to overcome the vulnerability of classical DRPE. The CS technique and space multiplexing are able to provide additional key space in the proposed method. A numerical experiment of the proposed method is implemented and the results show that the proposed method has good accuracy and is more robust than classical DRPE. The proposed system is also employed against chosen-plaintext attacks and it is found that the inclusion of compressive sensing enhances robustness against the attacks.

  2. Generalizing the Faddeev-Jackiw Technique to Curved Spacetimes to Study Bose-Einstein Condensates in Space

    NASA Astrophysics Data System (ADS)

    Prescod-Weinstein, Chanda; Bertschinger, Edmund

    2014-03-01

    Motivated by the desire to fully understand Bose-Einstein condensates in curved spacetimes, we present a generalization of the Faddeev-Jackiw technique for constraint reduction that simplifies calculating the Poisson brackets for gauge field theories in curved backgrounds. The Faddeev-Jackiw technique is a symplectic approach to phase space coordinate reduction on singular Lagrangians which offers an alternative to the Dirac technique. This approach was generalized by Barcelos-Nieto and Wotzasek to make its application easier. We find that the technique is a useful tool that avoids some of the subtle complications of the Dirac approach to constraints. A major difference between our work and previous formulations is that we do not explicitly construct the symplectic matrix, as that is not necessary. We apply this formulation to the Ginzburg-Landau action and calculate its Poisson brackets in a curved spacetime. We sketch out steps to apply the technique to a Bose field in the gauge theory General Relativity.

  3. KENNEDY SPACE CENTER, FLA. - Jeff Thon, an SRB mechanic with United Space Alliance, tests a technique for vertical solid rocket booster propellant grain inspection. The inspection of segments is required as part of safety analysis.

    NASA Image and Video Library

    2003-09-11

    KENNEDY SPACE CENTER, FLA. - Jeff Thon, an SRB mechanic with United Space Alliance, tests a technique for vertical solid rocket booster propellant grain inspection. The inspection of segments is required as part of safety analysis.

  4. Vascular Spaces in Compact Bone: A Technique to Correct a Common Misinterpretation of Structure

    ERIC Educational Resources Information Center

    Locke, M.; Dean, Rob L.

    2003-01-01

    Old bones are often discolored by the grime that infiltrates spaces in the matrix once occupied by blood vessels. This suggested that allowing dry bone to absorb colorants might be a useful way to show the three dimensional complexity of bone vascularization. The authors have developed a simple way to show blood vessels spaces in bone at a glance…

  5. Vascular Spaces in Compact Bone: A Technique to Correct a Common Misinterpretation of Structure

    ERIC Educational Resources Information Center

    Locke, M.; Dean, Rob L.

    2003-01-01

    Old bones are often discolored by the grime that infiltrates spaces in the matrix once occupied by blood vessels. This suggested that allowing dry bone to absorb colorants might be a useful way to show the three dimensional complexity of bone vascularization. The authors have developed a simple way to show blood vessels spaces in bone at a glance…

  6. The Application of Advanced Cultivation Techniques in the Long Term Maintenance of Space Flight Plant Biological Systems

    NASA Technical Reports Server (NTRS)

    Heyenga, A. G.

    2003-01-01

    The development of the International Space Station (ISS) presents extensive opportunities for the implementation of long duration space life sciences studies. Continued attention has been placed in the development of plant growth chamber facilities capable of supporting the cultivation of plants in space flight microgravity conditions. The success of these facilities is largely dependent on their capacity to support the various growth requirements of test plant species. The cultivation requirements for higher plant species are generally complex, requiring specific levels of illumination, temperature, humidity, water, nutrients, and gas composition in order to achieve normal physiological growth and development. The supply of water, nutrients, and oxygen to the plant root system is a factor, which has proven to be particularly challenging in a microgravity space flight environment. The resolution of this issue is particularly important for the more intensive crop cultivation of plants envisaged in Nasa's advanced life support initiative. BioServe Space Technologies is a NASA, Research Partnership Center (RPC) at the University of Colorado, Boulder. BioServe has designed and operated various space flight plant habitat systems, and placed specific emphasis on the development and enhanced performance of subsystem components such as water and nutrient delivery, illumination, gas exchange and atmosphere control, temperature and humidity control. The further development and application of these subsystems to next generation habitats is of significant benefit and contribution towards the development of both the Space Plant biology and the Advanced Life Support Programs. The cooperative agreement between NASA Ames Research center and BioServe was established to support the further implementation of advanced cultivation techniques and protocols to plant habitat systems being coordinated at NASA Ames Research Center. Emphasis was placed on the implementation of passive

  7. The Application of Advanced Cultivation Techniques in the Long Term Maintenance of Space Flight Plant Biological Systems

    NASA Technical Reports Server (NTRS)

    Heyenga, A. G.

    2003-01-01

    The development of the International Space Station (ISS) presents extensive opportunities for the implementation of long duration space life sciences studies. Continued attention has been placed in the development of plant growth chamber facilities capable of supporting the cultivation of plants in space flight microgravity conditions. The success of these facilities is largely dependent on their capacity to support the various growth requirements of test plant species. The cultivation requirements for higher plant species are generally complex, requiring specific levels of illumination, temperature, humidity, water, nutrients, and gas composition in order to achieve normal physiological growth and development. The supply of water, nutrients, and oxygen to the plant root system is a factor, which has proven to be particularly challenging in a microgravity space flight environment. The resolution of this issue is particularly important for the more intensive crop cultivation of plants envisaged in Nasa's advanced life support initiative. BioServe Space Technologies is a NASA, Research Partnership Center (RPC) at the University of Colorado, Boulder. BioServe has designed and operated various space flight plant habitat systems, and placed specific emphasis on the development and enhanced performance of subsystem components such as water and nutrient delivery, illumination, gas exchange and atmosphere control, temperature and humidity control. The further development and application of these subsystems to next generation habitats is of significant benefit and contribution towards the development of both the Space Plant biology and the Advanced Life Support Programs. The cooperative agreement between NASA Ames Research center and BioServe was established to support the further implementation of advanced cultivation techniques and protocols to plant habitat systems being coordinated at NASA Ames Research Center. Emphasis was placed on the implementation of passive

  8. Schiller Goes to the Movies: Locating the Sublime in "Thelma and Louise."

    ERIC Educational Resources Information Center

    Hoyng, Peter

    1997-01-01

    Endeavors to make students aware of similarities between today's movie culture and the theater of the 18th century; parallels between a traditional drama and a movie script; and Schiller's understanding of the sublime. (36 references) (Author/CK)

  9. A Comparison of IM-CW Lidar Modulation Techniques for ASCENDS CO2 Column Measurements from Space

    NASA Astrophysics Data System (ADS)

    Campbell, Joel; Lin, Bing; Nehrir, Amin; Harrison, Fenton; Obland, Michael; Ismail, Syed

    2014-05-01

    Global atmospheric carbon dioxide (CO2) measurements through the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) Decadal Survey recommended space mission are critical for improving our understanding of CO2 sources and sinks. IM-CW (Intensity Modulated Continuous Wave) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS science requirements. In previous laboratory and flight experiments we have successfully used linear swept frequency modulation to discriminate surface lidar returns from intermediate aerosol and cloud contamination. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate clouds, which is a requirement for the inversion of the CO2 column-mixing ratio from the instrument optical depth measurements, has been demonstrated with the linear swept frequency modulation technique. We are concurrently investigating advanced techniques to help improve the auto-correlation properties of the transmitted waveform implemented through physical hardware to make cloud rejection more robust in special restricted scenarios. Several different carrier based modulation techniques are compared including orthogonal linear swept, orthogonal non-linear swept, and Binary Phase Shift Keying (BPSK). Techniques are investigated that reduce or eliminate sidelobes. These techniques have excellent auto-correlation properties while possessing a finite bandwidth (by way of a new cyclic digital filter), which will reduce bias error in the presence of multiple scatterers. Our analyses show that the studied modulation techniques can increase the accuracy of CO2 column measurements from space. A comparison of various properties such as signal to noise ratio (SNR) and time-bandwidth product are discussed.

  10. A Comparison of Potential IM-CW Lidar Modulation Techniques for ASCENDS CO2 Column Measurements From Space

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.; Harrison, F. Wallace; Obland, Michael D.; Ismail, Syed

    2014-01-01

    Global atmospheric carbon dioxide (CO2) measurements through the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) Decadal Survey recommended space mission are critical for improving our understanding of CO2 sources and sinks. IM-CW (Intensity Modulated Continuous Wave) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS science requirements. In previous laboratory and flight experiments we have successfully used linear swept frequency modulation to discriminate surface lidar returns from intermediate aerosol and cloud contamination. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate clouds, which is a requirement for the inversion of the CO2 column-mixing ratio from the instrument optical depth measurements, has been demonstrated with the linear swept frequency modulation technique. We are concurrently investigating advanced techniques to help improve the auto-correlation properties of the transmitted waveform implemented through physical hardware to make cloud rejection more robust in special restricted scenarios. Several different carrier based modulation techniques are compared including orthogonal linear swept, orthogonal non-linear swept, and Binary Phase Shift Keying (BPSK). Techniques are investigated that reduce or eliminate sidelobes. These techniques have excellent auto-correlation properties while possessing a finite bandwidth (by way of a new cyclic digital filter), which will reduce bias error in the presence of multiple scatterers. Our analyses show that the studied modulation techniques can increase the accuracy of CO2 column measurements from space. A comparison of various properties such as signal to noise ratio (SNR) and time-bandwidth product are discussed.

  11. Sublimation TiN Coating of RF Power Components

    NASA Astrophysics Data System (ADS)

    Lorkiewicz, J.; Kula, J.; Pszona, S.; Sobczak, J.; Bilinski, A.

    2008-03-01

    Titanium evaporation in a reactive atmosphere of ammonia has been chosen to deposit thin (up to 10 nm) protective surface layers containing titanium nitride and titanium oxinitrides which suppress secondary electron emission. The coating procedure, applied by the author in DESY (Hamburg) for TESLA couplers anti-multipactor protection, has been recently implemented in The Andrzej Soltan Institute for Nuclear Studies (IPJ) where a new coating device is used, equipped with a special titanium sublimation setup in a 100 1 vacuum chamber. Several arrays of cylindrical and coaxial RF coupler windows have been coated so far after optimizing the processing parameters. A check of the obtained surface layers ability to attenuate secondary electron emission has been performed; measurements of the secondary electron yield from TiN layers deposited on alumina samples were done in IPJ on as-delivered coated samples, then after vacuum bake-out and finally after additional electron bombardment of their surfaces. Also chemical composition of the surface layers has been studied using XPS in the Institute of Physical Chemistry (IChF).

  12. Rare earths behaviour during the deposition of volcanic sublimates

    NASA Astrophysics Data System (ADS)

    Censi, P.; Sortino, F.; Zuddas, P.; Saiano, F.; Brusca, L.; Chiavetta, S.; Falcone, E. E.

    2017-02-01

    In this study, the REE distribution between volcanic fluids and related solids in fumaroles with temperatures ranging from approximately 100 to 421 °C was investigated in different geological scenarios. The treatment of geochemical REE data was carried out by calculating the REE enrichment factors (EFREE) relative to the volcanic host rocks in studied sites under the assumption that the REE transport takes place as silicate aerosol in volcanic fluids. Shale-normalised REE concentrations in these fluids have been assessed to investigate whether the REE transport as aqueous complexes in water-saturated volcanic gas is reasonable. The REE behaviour in alkaline condensates according to the above mentioned treatments of geochemical data is very similar, being characterised by positive Ce and Gd anomalies and significant W-type tetrad effects. These evidences suggest that the geochemical behaviour of REE in fumarolic fluids is firstly influenced by the sublimate deposition along the fumarolic conduit or around the vents rather than by the transport mechanism of these elements in volcanic fluids.

  13. Bion and the sublime: the origins of an aesthetic paradigm.

    PubMed

    Civitarese, Giuseppe

    2014-12-01

    In constructing his theory Bion drew on a number of symbolic matrices: psychoanalysis, philosophy, mathematics, literature, aesthetics. The least investigated of these is the last. True, we know that Bion cites many authors of the Romantic period, such as Coleridge, Keats, Blake and Wordsworth, as well as others who were held in high esteem in the Romantic period, such as Milton. However, less is known about the influence exerted on him by the aesthetics of the sublime, which while chronologically preceding Romanticism is in fact one of its components. My working hypothesis is that tracing a number of Bion's concepts back to this secret model can serve several purposes: firstly, it contributes to the study of the sources, and, secondly, it makes these concepts appear much less occasional and idiosyncratic than we might believe, being as they are mostly those less immediately understandable but not less important (O, negative capability, nameless dread, the infinite, the language of achievement, unison etc.). Finally, connecting these notions to a matrix, that is, disclosing the meaning of elements that are not simply juxtaposed but dynamically interrelated, in my view significantly increases not only their theoretical intelligibility but also their usefulness in clinical practice. In conclusion, one could legitimately argue that Bion gradually subsumed all the other paradigms he drew on within the aesthetic paradigm.

  14. Transformation of Polar Ice Sublimate Residue into Martian Circumpolar Sand

    NASA Technical Reports Server (NTRS)

    Saunders, R. S.; Parker, T. J.; Stephens, J. B.; Laue, E. G.; Fanale, F. P.

    1985-01-01

    The experimental demonstration that a credible Martian sand may be formed from dust-bearing ice provides a new set of possible explanations for some of the observed Martian aeolian landforms. It is hypothesized that a light-weight fluffy rind is formed on the polar caps. This could provide material easily entrainable by Martian winds, which generally blow equatorward from the poles. These winds would peel the fluffy rind from the surface of the sublimating summer polar caps and from the equatorward slopes of the polar troughs. These pieces of material would then be rolled into lumps (of high sailarea/mass ratio) by the wind. They would become pigmented as they saltate across the surface, perhaps gathering carbonaceous meteoritic dust or other impurities on their surfaces, or through chemical reactions with the ice-free environment away from their point of origin. Once they became trapped in topographic wind shadows, they would form dune structures because they are hydraulically equivalent to sand particles.

  15. Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica.

    USGS Publications Warehouse

    Clow, G.D.; McKay, C.P.; Simmons, G.M.; Wharton, R.A.

    1988-01-01

    In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, we report on the first year-round observations available for any site in Taylor Valley. This dataset augments the year-round data obtained at Lake Vanda (Wright Valley) by winter-over crews during the late 1960s and early 1970s. The mean annual solar flux at Lake Hoare was 92 W m-2 during 1986, the mean air temperature -17.3 degrees C, and the mean 3-m wind speed 3.3 m s-1. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year. Temperature increases of 20 degrees-30 degrees C are frequently observed during the winter due to strong fo??hn winds descending from the Polar Plateau. A model incorporating nonsteady molecular diffusion into Kolmogorov-scale eddies in the interfacial layer and similarity-theory flux-profiles in the surface sublayer, is used to determine the rate of ice sublimation from the acquired meteorological data. Despite the frequent occurrence of strong winter fo??hns, the bulk of the annual ablation occurs during the summer due to elevated temperatures and persistent moderate winds. The annual ablation from Lake Hoare is estimated to have been 35.0 +/- 6.3 cm for 1986.

  16. Development of porous titanium for biomedical applications: A comparison between loose sintering and space-holder techniques.

    PubMed

    Torres, Yadir; Lascano, Sheila; Bris, Jorge; Pavón, Juan; Rodriguez, José A

    2014-04-01

    One of the most important concerns in long-term prostheses is bone resorption as a result of the stress shielding due to stiffness mismatch between bone and implant. The aim of this study was to obtain porous titanium with stiffness values similar to that exhibited by cortical bone. Porous samples of commercial pure titanium grade-4 were obtained by following both loose-sintering processing and space-holder technique with NaCl between 40 and 70% in volume fraction. Both mechanical properties and porosity morphology were assessed. Young's modulus was measured using uniaxial compression testing, as well as ultrasound methodology. Complete characterization and mechanical testing results allowed us to determine some important findings: (i) optimal parameters for both processing routes; (ii) better mechanical response was obtained by using space-holder technique; (iii) pore geometry of loose sintering samples becomes more regular with increasing sintering temperature; in the case of the space-holder technique that trend was observed for decreasing volume fraction; (iv) most reliable Young's modulus measurements were achieved by ultrasound technique. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. The Application of Structural Reliability Techniques to Plume Impingement Loading of the Space Station Freedom Photovoltaic Array

    NASA Technical Reports Server (NTRS)

    Yunis, Isam S.; Carney, Kelly S.

    1993-01-01

    A new aerospace application of structural reliability techniques is presented, where the applied forces depend on many probabilistic variables. This application is the plume impingement loading of the Space Station Freedom Photovoltaic Arrays. When the space shuttle berths with Space Station Freedom it must brake and maneuver towards the berthing point using its primary jets. The jet exhaust, or plume, may cause high loads on the photovoltaic arrays. The many parameters governing this problem are highly uncertain and random. An approach, using techniques from structural reliability, as opposed to the accepted deterministic methods, is presented which assesses the probability of failure of the array mast due to plume impingement loading. A Monte Carlo simulation of the berthing approach is used to determine the probability distribution of the loading. A probability distribution is also determined for the strength of the array. Structural reliability techniques are then used to assess the array mast design. These techniques are found to be superior to the standard deterministic dynamic transient analysis, for this class of problem. The results show that the probability of failure of the current array mast design, during its 15 year life, is minute.

  18. The application of structural reliability techniques to plume impingement loading of the Space Station Freedom Photovoltaic Array

    NASA Technical Reports Server (NTRS)

    Yunis, Isam S.; Carney, Kelly S.

    1993-01-01

    A new aerospace application of structural reliability techniques is presented, where the applied forces depend on many probabilistic variables. This application is the plume impingement loading of the Space Station Freedom Photovoltaic Arrays. When the space shuttle berths with Space Station Freedom it must brake and maneuver towards the berthing point using its primary jets. The jet exhaust, or plume, may cause high loads on the photovoltaic arrays. The many parameters governing this problem are highly uncertain and random. An approach, using techniques from structural reliability, as opposed to the accepted deterministic methods, is presented which assesses the probability of failure of the array mast due to plume impingement loading. A Monte Carlo simulation of the berthing approach is used to determine the probability distribution of the loading. A probability distribution is also determined for the strength of the array. Structural reliability techniques are then used to assess the array mast design. These techniques are found to be superior to the standard deterministic dynamic transient analysis, for this class of problem. The results show that the probability of failure of the current array mast design, during its 15 year life, is minute.

  19. Thermal alteration in carbonaceous chondrites and implications for sublimation in rock comets

    NASA Astrophysics Data System (ADS)

    Springmann, Alessondra; Lauretta, Dante S.; Steckloff, Jordan K.

    2015-11-01

    Rock comets are small solar system bodies in Sun-skirting orbits (perihelion q < ~0.15 AU) that form comae rich in mineral sublimation products, but lack typical cometary ice sublimation products (H2O, CO2, etc.). B-class asteroid (3200) Phaethon, considered to be the parent body of the Geminid meteor shower, is the only rock comet currently known to periodically eject dust and form a coma. Thermal fracturing or thermal decomposition of surface materials may be driving Phaethon’s cometary activity (Li & Jewitt, 2013). Phaethon-like asteroids have dynamically unstable orbits, and their perihelia can change rapidly over their ~10 Myr lifetimes (de León et al., 2010), raising the possibility that other asteroids may have been rock comets in the past. Here, we propose using spectroscopic observations of mercury (Hg) as a tracer of an asteroid’s thermal metamorphic history, and therefore as a constraint on its minimum achieved perihelion distance.B-class asteroids such as Phaethon have an initial composition similar to aqueously altered primitive meteorites such as CI- or CM-type meteorites (Clark et al., 2010). Laboratory heating experiments of ~mm sized samples of carbonaceous chondrite meteorites from 300K to 1200K at a rate of 15K/minute show mobilization and volatilization of various labile elements at temperatures that could be reached by Mercury-crossing asteroids. Samples became rapidly depleted in labile elements and, in particular, lost ~75% of their Hg content when heated from ~500-700 K, which corresponds to heliocentric distances of ~0.15-0.3 au, consistent with our thermal models. Mercury has strong emission lines in the UV (~ 185 nm) and thus its presence (or absence) relative to carbonaceous chondrite abundances would indicate if these bodies had perihelia in their dynamical histories inside of 0.15 AU, and therefore may have previously been Phaethon-like rock comets. Future space telescopes or balloon-borne observing platforms equipped with a UV

  20. Precipitation, sublimation, and snow drift in the Antarctic Peninsula region from a regional atmospheric model

    NASA Astrophysics Data System (ADS)

    van Lipzig, N. P. M.; King, J. C.; Lachlan-Cope, T. A.; van den Broeke, M. R.

    2004-12-01

    A regional atmospheric model, with a horizontal grid spacing (Δx) of 14 km, is used to study the surface mass balance components (precipitation, sublimation, and snow drift) in the region of the Antarctic Peninsula (AP). An integration is performed for the 7-year period 1987-1993, using a realistic forcing at the lateral model boundaries and at the sea surface. Output from this integration indicates that the precipitation reaches its maximum value on the northwestern slope of the AP, where the upward motion in the atmosphere is largest. Uplift occurs upstream of the barrier, affecting the precipitation distribution over sea. The effect of the barrier on the precipitation distribution over the Bellingshausen Sea might have important implications for the ocean circulation in this region. The mean precipitation over the grounded ice of the AP (1.20 m water eq yr-1) is 6 times larger than the mean value over all the grounded ice of Antarctica. Our estimates for the surface sublimation and wind transport of snow over the grounding line toward the sea are 9% and 6 ± 1% of the precipitation, respectively. In situ data of the wind distribution at three coastal sites located on the northern, eastern, and western sides of the AP are used to evaluate the modeled wind field, which is important for the snow drift calculations. For two of the three sites considered, the prevailing wind direction and bimodal wind distribution are correctly represented by the model. The calculated distribution of accumulation and ablation due to snow drift shows a complex pattern. The wind removes snow from the spine of the AP, where the near-surface flow field diverges, whereas deposition occurs mainly on the eastern slopes, where the near-surface flow field converges. An intercomparison between two 7-year integrations at different horizontal resolution (Δx = 14 km and Δx = 55 km) shows that the precipitation on the northwestern slope is very sensitive to the model resolution: In the Δx = 14

  1. Comparison of methods for quantifying surface sublimation over seasonally snow-covered terrain

    USGS Publications Warehouse

    Sexstone, Graham A.; Clow, David W.; Stannard, David I.; Fassnacht, Steven R.

    2016-01-01

    Snow sublimation can be an important component of the snow-cover mass balance, and there is considerable interest in quantifying the role of this process within the water and energy balance of snow-covered regions. In recent years, robust eddy covariance (EC) instrumentation has been used to quantify snow sublimation over snow-covered surfaces in complex mountainous terrain. However, EC can be challenging for monitoring turbulent fluxes in snow-covered environments because of intensive data, power, and fetch requirements, and alternative methods of estimating snow sublimation are often relied upon. To evaluate the relative merits of methods for quantifying surface sublimation, fluxes calculated by the EC, Bowen ratio–energy balance (BR), bulk aerodynamic flux (BF), and aerodynamic profile (AP) methods and their associated uncertainty were compared at two forested openings in the Colorado Rocky Mountains. Biases between methods are evaluated over a range of environmental conditions, and limitations of each method are discussed. Mean surface sublimation rates from both sites ranged from 0.33 to 0.36 mm day−1, 0.14 to 0.37 mm day−1, 0.10 to 0.17 mm day−1, and 0.03 to 0.10 mm day−1 for the EC, BR, BF and AP methods, respectively. The EC and/or BF methods are concluded to be superior for estimating surface sublimation in snow-covered forested openings. The surface sublimation rates quantified in this study are generally smaller in magnitude compared with previously published studies in this region and help to refine sublimation estimates for forested openings in the Colorado Rocky Mountains.

  2. Uptake of Mg and K on ice: Effect of sublimation and energetic particle bombardment

    NASA Astrophysics Data System (ADS)

    Mangan, T.; Frankland, V.; Plane, J. M. C.

    2016-12-01

    Uptake of metals on water ice can occur in polar mesospheric clouds (PMCs) in the mesosphere of Earth, on icy bodies in space and in the interstellar medium (ISM). Uptake of metals on icy particles could have implications for the surface and gas phase chemistry of the mesosphere. While in the ISM, the interactions of metals with water ice could affect processes relating to the agglomeration of matter into planets. In this study we experimentally investigate Mg and K embedded in water ice. Mg and K dosed ice films were prepared under ultra-high vacuum conditions in the laboratory at temperatures ≤ 140 K. Metal dosed ice films were subjected to temperature programmed desorption (TPD) and energetic ion bombardment (Ar+ and Kr+). TPD experiments revealed that negligible Mg and K containing species were co-desorbed with the ice film. This was also previously observed for Fe and suggests that metals contained within sublimating PMC particles in the mesosphere (or Icy particles in the ISM) may not be released into the gas phase. Instead, the metallic species could coalesce leading to the formation of residual particles. Energetic sputtering of metal dosed ice layers by 500 eV energy Ar+ and Kr+ efficiently removed the metals and highlighted significant differences between the two regarding their distribution within the ice layer.

  3. Two imaging techniques for 3D quantification of pre-cementation space for CAD/CAM crowns.

    PubMed

    Rungruanganunt, Patchanee; Kelly, J Robert; Adams, Douglas J

    2010-12-01

    Internal three-dimensional (3D) "fit" of prostheses to prepared teeth is likely more important clinically than "fit" judged only at the level of the margin (i.e. marginal "opening"). This work evaluates two techniques for quantitatively defining 3D "fit", both using pre-cementation space impressions: X-ray microcomputed tomography (micro-CT) and quantitative optical analysis. Both techniques are of interest for comparison of CAD/CAM system capabilities and for documenting "fit" as part of clinical studies. Pre-cementation space impressions were taken of a single zirconia coping on its die using a low viscosity poly(vinyl siloxane) impression material. Calibration specimens of this material were fabricated between the measuring platens of a micrometre. Both calibration curves and pre-cementation space impression data sets were obtained by examination using micro-CT and quantitative optical analysis. Regression analysis was used to compare calibration curves with calibration sets. Micro-CT calibration data showed tighter 95% confidence intervals and was able to measure over a wider thickness range than for the optical technique. Regions of interest (e.g., lingual, cervical) were more easily analysed with optical image analysis and this technique was more suitable for extremely thin impression walls (<10-15μm). Specimen preparation is easier for micro-CT and segmentation parameters appeared to capture dimensions accurately. Both micro-CT and the optical method can be used to quantify the thickness of pre-cementation space impressions. Each has advantages and limitations but either technique has the potential for use as part of clinical studies or CAD/CAM protocol optimization. Copyright © 2010 Elsevier Ltd. All rights reserved.

  4. Adaptive/learning control of large space structures - System identification techniques. [for multi-configuration flexible spacecraft

    NASA Technical Reports Server (NTRS)

    Thau, F. E.; Montgomery, R. C.

    1980-01-01

    Techniques developed for the control of aircraft under changing operating conditions are used to develop a learning control system structure for a multi-configuration, flexible space vehicle. A configuration identification subsystem that is to be used with a learning algorithm and a memory and control process subsystem is developed. Adaptive gain adjustments can be achieved by this learning approach without prestoring of large blocks of parameter data and without dither signal inputs which will be suppressed during operations for which they are not compatible. The Space Shuttle Solar Electric Propulsion (SEP) experiment is used as a sample problem for the testing of adaptive/learning control system algorithms.

  5. Analysis of space radiation effects in gallium arsenide and cadmium selenide semiconductor samples using luminescence spectroscopic techniques. Master's thesis

    SciTech Connect

    Shaffer, B.L.

    1990-12-01

    Analysis of space radiation effects in gallium arsenide and cadmium selenide semiconductor samples using luminescence spectroscopic techniques. The M0006 semiconductor samples were placed into a 28.5 degree inclination, 480 km altitude, near-circular orbit aboard the Long Duration Exposure Facility satellite and exposed to direct space environment for a period of 11 months, and were shielded by 0.313 inches of aluminum for another 58 months. The samples were examined for changes using cathodoluminescence and photoluminescence in various wavelength regions from 0.5 to 1.8 micrometers. Samples were cooled to approximately 10 degrees Kelvin in a vacuum of 10-8. (JS)

  6. Space Shuttle photographic/television analysis project - An overview of image analysis techniques

    NASA Technical Reports Server (NTRS)

    Dailey, Christine L.; Rovinelli, Elizabeth R.; Pitts, David E.

    1992-01-01

    The Space Shuttle photographic and television analysis project (SSPTAP) at the Johnson Space Center (JSC) is described. The films and videos of every Space Shuttle launch and landing are scrutinized for information on the vehicle's condition and performance which can only be obtained by photographic means when necessary. On-orbit video is used to assess problems. The photographic information is used with various other data sources to develop feasible scenarios for particular events. The data and methods used to analyze the state of the Shuttle launch vehicle are analyzed, and examples are given of some of the studies that have been conducted.

  7. Space Shuttle photographic/television analysis project - An overview of image analysis techniques

    NASA Technical Reports Server (NTRS)

    Dailey, Christine L.; Rovinelli, Elizabeth R.; Pitts, David E.

    1992-01-01

    The Space Shuttle photographic and television analysis project (SSPTAP) at the Johnson Space Center (JSC) is described. The films and videos of every Space Shuttle launch and landing are scrutinized for information on the vehicle's condition and performance which can only be obtained by photographic means when necessary. On-orbit video is used to assess problems. The photographic information is used with various other data sources to develop feasible scenarios for particular events. The data and methods used to analyze the state of the Shuttle launch vehicle are analyzed, and examples are given of some of the studies that have been conducted.

  8. Collection-efficient, axisymmetric vacuum sublimation module for the purification of solid materials

    NASA Astrophysics Data System (ADS)

    May, Michael; Paul, Elizabeth; Katovic, Vladimir

    2015-11-01

    A vacuum sublimation module of axisymmetric geometry was developed and employed to purify solid-phase materials. The module provides certain practical advantages and it comprises: a metering valve, glass collector, glass lower body, main seal, threaded bushing, and glass internal cartridge (the latter to contain starting material). A complementary process was developed to de-solvate, sublime, weigh, and collect solid chemical materials exemplified by oxalic acid, ferrocene, pentachlorobenzene, chrysene, and urea. The oxalic acid sublimate was analyzed by titration, melting range, Fourier Transform Infrared (FT-IR) Spectroscopy, cyclic voltammetry, and its (aqueous phase) electrolytically generated gas. The analytical data were consistent with a high-purity, anhydrous oxalic acid sublimate. Cyclic voltammograms of 0.11 mol. % oxalic acid in water displayed a 2.1 V window on glassy carbon electrode beyond which electrolytic decomposition occurs. During module testing, fifteen relatively pure materials were sublimed with (energy efficient) passive cooling and the solid-phase recovery averaged 95 mass %. Key module design features include: compact vertical geometry, low-angle conical collector, uniformly compressed main seal, modest power consumption, transparency, glovebox compatibility, cooling options, and preferential conductive heat transfer. To help evaluate the structural (module) heat transfer, vertical temperature profiles along the dynamically evacuated lower body were measured versus electric heater power: for example, an input of 18.6 W generated a temperature 443-K at the bottom. Experimental results and engineering calculations indicate that during sublimation, solid conduction is the primary mode of heat transfer to the starting material.

  9. Collection-efficient, axisymmetric vacuum sublimation module for the purification of solid materials.

    PubMed

    May, Michael; Paul, Elizabeth; Katovic, Vladimir

    2015-11-01

    A vacuum sublimation module of axisymmetric geometry was developed and employed to purify solid-phase materials. The module provides certain practical advantages and it comprises: a metering valve, glass collector, glass lower body, main seal, threaded bushing, and glass internal cartridge (the latter to contain starting material). A complementary process was developed to de-solvate, sublime, weigh, and collect solid chemical materials exemplified by oxalic acid, ferrocene, pentachlorobenzene, chrysene, and urea. The oxalic acid sublimate was analyzed by titration, melting range, Fourier Transform Infrared (FT-IR) Spectroscopy, cyclic voltammetry, and its (aqueous phase) electrolytically generated gas. The analytical data were consistent with a high-purity, anhydrous oxalic acid sublimate. Cyclic voltammograms of 0.11 mol. % oxalic acid in water displayed a 2.1 V window on glassy carbon electrode beyond which electrolytic decomposition occurs. During module testing, fifteen relatively pure materials were sublimed with (energy efficient) passive cooling and the solid-phase recovery averaged 95 mass %. Key module design features include: compact vertical geometry, low-angle conical collector, uniformly compressed main seal, modest power consumption, transparency, glovebox compatibility, cooling options, and preferential conductive heat transfer. To help evaluate the structural (module) heat transfer, vertical temperature profiles along the dynamically evacuated lower body were measured versus electric heater power: for example, an input of 18.6 W generated a temperature 443-K at the bottom. Experimental results and engineering calculations indicate that during sublimation, solid conduction is the primary mode of heat transfer to the starting material.

  10. Residual and suppressed-carrier arraying techniques for deep-space communications

    NASA Technical Reports Server (NTRS)

    Shihabi, M.; Shah, B.; Hinedi, S.; Million, S.

    1995-01-01

    Three techniques that use carrier information from multiple antennas to enhance carrier acquisition and tracking are presented. These techniques in combination with baseband combining are analyzed and simulated for residual and suppressed-carrier modulation. It is shown that the carrier arraying using a single carrier loop technique can acquire and track the carrier even when any single antenna in the array cannot do so by itself. The carrier aiding and carrier arraying using multiple carrier loop techniques, on the other hand, are shown to lock on the carrier only when one of the array elements has sufficient margin to acquire the carrier on its own.

  11. An evaluation of some special techniques for nuclear waste disposal in space

    NASA Technical Reports Server (NTRS)

    Mackay, J. S.

    1973-01-01

    A preliminary examination is reported of several special ways for space disposal of nuclear waste material which utilize the radioactive heat in the waste to assist in the propulsion for deep space trajectories. These include use of the wastes in a thermoelectric generator (RTG) which operates an electric propulsion device and a radioisotope - thermal thruster which uses hydrogen or ammonia as the propellant. These propulsive devices are compared to the space tug and the space tug/solar electric propulsion combination for disposal of waste on a solar system escape trajectory. Such comparisons indicate that the waste-RTG approach has considerable potential provided the combined specific mass of the waste container - RTG system does not exceed approximately 150 kg/kw sub e. Several exploratory numerical calculations have been made for high earth orbit and Earth escape destinations.

  12. Subpicosecond electron bunch train production using a phase-space exchange technique

    SciTech Connect

    Sun, Y.-E.; Piot, P.; Johnson, A.S.; Lumpkin, A.H.; Maxwell, T.J.; Ruan, J.; Thurman-Keup, R.M.; /Fermilab

    2011-03-01

    Our recent experimental demonstration of a photoinjector electron bunch train with sub-picosecond structures is reported in this paper. The experiment is accomplished by converting an initially horizontal beam intensity modulation into a longitudinal phase space modulation, via a beamline capable of exchanging phase-space coordinates between the horizontal and longitudinal degrees of freedom. The initial transverse modulation is produced by intercepting the beam with a multislit mask prior to the exchange. We also compare our experimental results with numerical simulations.

  13. A stable and accurate relaxation technique using multiple penalty terms in space and time

    NASA Astrophysics Data System (ADS)

    Frenander, Hannes; Nordström, Jan

    2017-09-01

    A new method for data relaxation based on weak imposition of external data is introduced. The technique is simple, easy to implement, and the resulting numerical scheme is unconditionally stable. Numerical experiments show that the error growth naturally present in long term simulations can be prevented by using the new technique.

  14. Problems at the Leading Edge of Space Weathering as Revealed by TEM Combined with Surface Science Techniques

    NASA Technical Reports Server (NTRS)

    Christoffersen, R.; Dukes, C. A.; Keller, L. P.; Rahman, Z.; Baragiola, R. A.

    2015-01-01

    Both transmission electron micros-copy (TEM) and surface analysis techniques such as X-ray photoelectron spectroscopy (XPS) were instrumen-tal in making the first characterizations of material generated by space weathering in lunar samples [1,2]. Without them, the nature of nanophase metallic Fe (npFe0) correlated with the surface of lunar regolith grains would have taken much longer to become rec-ognized and understood. Our groups at JSC and UVa have been using both techniques in a cross-correlated way to investigate how the solar wind contributes to space weathering [e.g., 3]. These efforts have identified a number of ongoing problems and knowledge gaps. Key insights made by UVa group leader Raul Barag-iola during this work are gratefully remembered.

  15. Isolation of Purines and Pyrimidines from the Murchison Meteorite Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Bada, J. L.

    2004-01-01

    The origin of life on Earth, and possibly on other planets such as Mars, would have required the presence of liquid water and a continuous supply of prebiotic organic compounds. The exogenous delivery of organic matter by asteroids, comets, and carbonaceous meteorites could have contributed to the early Earth s prebiotic inventory by seeding the planet with biologically important organic compounds. A wide variety of prebiotic organic compounds have previously been detected in the Murchison CM type carbonaceous chondrite including amino acids, purines and pyrimidines. These compounds dominate terrestrial biochemistry and are integral components of proteins, DNA and RNA. Several purines including adenine, guanine, hypoxanthine, and xanthine, as well as the pyrimidine uracil, have previously been detected in water or formic acid extracts of Murchison using ion-exclusion chromatography and ultraviolet spectroscopy. However, even after purification of these extracts, the accurate identification and quantification of nucleobases is difficult due to interfering UV absorbing compounds. In order to reduce these effects, we have developed an extraction technique using sublimation to isolate purines and pyrimidines from other non-volatile organic compounds in Murchison acid extracts.

  16. Isolation of Purines and Pyrimidines from the Murchison Meteorite Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Bada, J. L.

    2004-01-01

    The origin of life on Earth, and possibly on other planets such as Mars, would have required the presence of liquid water and a continuous supply of prebiotic organic compounds. The exogenous delivery of organic matter by asteroids, comets, and carbonaceous meteorites could have contributed to the early Earth s prebiotic inventory by seeding the planet with biologically important organic compounds. A wide variety of prebiotic organic compounds have previously been detected in the Murchison CM type carbonaceous chondrite including amino acids, purines and pyrimidines. These compounds dominate terrestrial biochemistry and are integral components of proteins, DNA and RNA. Several purines including adenine, guanine, hypoxanthine, and xanthine, as well as the pyrimidine uracil, have previously been detected in water or formic acid extracts of Murchison using ion-exclusion chromatography and ultraviolet spectroscopy. However, even after purification of these extracts, the accurate identification and quantification of nucleobases is difficult due to interfering UV absorbing compounds. In order to reduce these effects, we have developed an extraction technique using sublimation to isolate purines and pyrimidines from other non-volatile organic compounds in Murchison acid extracts.

  17. Desorption and sublimation kinetics for fluorinated aluminum nitride surfaces

    SciTech Connect

    King, Sean W. Davis, Robert F.; Nemanich, Robert J.

    2014-09-01

    an additional high temperature peak at 910 °C with E{sub d} = 370 ± 10 kJ/mol that is consistent with both the dehydrogenation of surface AlOH species and H{sub 2} assisted sublimation of AlN. Similarly, N{sub 2} exhibited a similar higher temperature desorption peak with E{sub d} = 535 ± 40 kJ/mol that is consistent with the activation energy for direct sublimation of AlN.

  18. Estimates of the Volume of Snowpack Sublimation in Arizona's Salt River Watershed

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2012-12-01

    The liquid equivalent volumes of snowpack sublimation, melt, and snowfall over the Salt River watershed, a major source of water for the Phoenix metropolitan area, will be estimated using the National Operational Hydrologic Remote Sensing Center's Snow Data Assimilation System (SNODAS) for the nine water years on record (i.e., 2004-2012). SNODAS integrates data from satellites, aircraft, and ground stations with downscaled output from numerical weather prediction models and an energy/mass balance snowpack model. The SNODAS dataset contains daily values of sublimation, snow water equivalent, snowfall, and melt, among other variables, at high (< 1 km2) resolution providing the opportunity to accurately estimate the volumes of snowpack balance variables for regions with complex topography. Snowpack ablation consists of sublimation and melting. Snow particles at sub-freezing temperatures will sublimate rather than melt if surrounded by air that is below the equilibrium water vapor pressure with respect to ice. When sublimation occurs, there is a direct loss of water from the given drainage basin when the vapor is carried away by the prevailing atmospheric flow. Preliminary analyses of water years 2005 (wet El Niño), 2007 (dry El Niño), 2008 (wet La Niña), and 2012 (dry La Niña) suggest that there is a substantial amount of sublimation over the Salt River watershed. From October 1 to April 30, approximately 16 percent of snowfall sublimated during the four years, ranging from approximately 98 million cubic meters (79,884 acre-feet) in water year 2005 to approximately 208 million cubic meters (168,726 acre-feet) in water year 2012. Sublimation is the most prevalent at the highest elevations of the watershed with more than 30 percent of snowfall sublimating at elevations above 2,744 meters above sea level. Of the four years analyzed, the sublimation to snowfall ratio was the highest for the two water years with anomalously high precipitation (i.e, 2005 and 2008). This

  19. Oxidation and sublimation of porous graphite during fiber laser irradiation

    NASA Astrophysics Data System (ADS)

    Phillips, Grady T.; Bauer, William A.; Gonzales, Ashley E.; Herr, Nicholas C.; Perram, Glen P.

    2017-02-01

    Porous graphite plates, cylinders and cones with densities of 1.55-1.82 g/cm3 were irradiated by a 10 kW fiber laser at 0.075 -3.525 kW/cm2 for 120 s to study mass removal and crater formation. Surface temperatures reached steady state values as high as 3767 K. The total decrease in sample mass ranged from 0.06 to 6.29 g, with crater volumes of 0.52 - 838 mm3, and penetration times for 12.7 mm thick plates as short as 38 s. Minor contaminants in the graphite samples produced calcium and iron oxide to be re-deposited on the graphite surface. Significantly increased porosity of the sample is observed even outside of the laser-irradiated region. Total mass removed increases with deposited laser energy at a rate of 4.83 g/MJ for medium extruded graphite with an apparent threshold of 0.15 MJ. Visible emission spectroscopy reveals C2 Swan and CN red, CN violet bands and Li, Na, and K 2P3/2,1/2 - 2S1/2 doublets. The reacting boundary layer is observed using a mid-wave imaging Fourier transform spectrometer (IFTS) at 2 cm-1 spectral resolution, 0.5 mm/pixel spatial resolution, and 0.75 Hz data cube rate. A two-layer radiative transfer model was used to determine plume temperature, CO, and CO2 concentrations from spectral signatures. The new understanding of graphite combustion and sublimation during laser irradiation is vital to the more complex behavior of carbon composites.

  20. Application of Different Statistical Techniques in Integrated Logistics Support of the International Space Station Alpha

    NASA Technical Reports Server (NTRS)

    Sepehry-Fard, F.; Coulthard, Maurice H.

    1995-01-01

    The process to predict the values of the maintenance time dependent variable parameters such as mean time between failures (MTBF) over time must be one that will not in turn introduce uncontrolled deviation in the results of the ILS analysis such as life cycle cost spares calculation, etc. A minor deviation in the values of the maintenance time dependent variable parameters such as MTBF over time will have a significant impact on the logistics resources demands, International Space Station availability, and maintenance support costs. It is the objective of this report to identify the magnitude of the expected enhancement in the accuracy of the results for the International Space Station reliability and maintainability data packages by providing examples. These examples partially portray the necessary information hy evaluating the impact of the said enhancements on the life cycle cost and the availability of the International Space Station.

  1. Application of Different Statistical Techniques in Integrated Logistics Support of the International Space Station Alpha

    NASA Technical Reports Server (NTRS)

    Sepehry-Fard, F.; Coulthard, Maurice H.

    1995-01-01

    The process to predict the values of the maintenance time dependent variable parameters such as mean time between failures (MTBF) over time must be one that will not in turn introduce uncontrolled deviation in the results of the ILS analysis such as life cycle cost spares calculation, etc. A minor deviation in the values of the maintenance time dependent variable parameters such as MTBF over time will have a significant impact on the logistics resources demands, International Space Station availability, and maintenance support costs. It is the objective of this report to identify the magnitude of the expected enhancement in the accuracy of the results for the International Space Station reliability and maintainability data packages by providing examples. These examples partially portray the necessary information hy evaluating the impact of the said enhancements on the life cycle cost and the availability of the International Space Station.

  2. Ni-625 Superalloy Foam Processed by Powder Space-Holder Technique

    NASA Astrophysics Data System (ADS)

    Unver, Ismail; Gulsoy, H. Ozkan; Aydemir, Bulent

    2013-12-01

    In this work, porous Ni-625 superalloys were produced by use of a water soluble pore forming agent prior to sintering. Carbamide particles were used as the space-holder materials. After mixing and compaction, the space-holder particles were extracted using warm water leaching over a range of temperatures. The porous green parts were subsequently thermally debinding to remove the paraffin wax under a pure Argon atmosphere, and subsequently sintered at high vacuum. The effects of volume fraction of space-holder particles on density, porosity, and elastic modulus were investigated. Microstructures were captured using optical and scanning electron microscopy. Pore size was quantified using image analysis software integral to the scanning electron microscopy. In addition, compression tests were conducted on the sintered samples.

  3. Research on technique of measuring space position change of equipment action part

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Deng, Shijie; Wang, Ping

    2008-12-01

    At present, a large number of electronic machinery and equipment was launched into military or civilian field. Such kind of equipments can rotates and moves precisely under control of micro-electronics device. It is an important task how to measure space position change of the mechanical parts. And it only can be proved by test that whether the space position change value of action parts meted the specification requirements. And the test must satisfy some accuracy requirements. In response to the test demand, we have developed out a system based on of photoelectricity theodolite. The system belongs to non-touched device, it is convenient and precise to use. In large-scale Space position changes with high-precision demand test mission, We think this method is the most feasible so far.

  4. Executive summary. [application of laser oriented and radio frequency techniques for space communication

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The scope of Technology Forecasting for Space Communications is very wide, covering virtually every technology that can directly or indirectly affect space communications. The assigned effort, however, was directed toward a series of studies which individually examined important aspects of space communications and which collectively was interrelated. The contributions of the individual tasks and their interrelationship are indicated. The total effort of the tasks was fairly evenly divided between laser oriented and radio frequency tasks. The investigations show that laser communications have a current state of the art which would allow operational systems to be implemented in the 1975 to 1980 time frame. Further, these systems, when operated over ranges in the order of synchronous ranges (42,000 km)and transmitting data rates of 10 to the 8th power 10 to the 9th power bits per second will have a smaller total weight impact on a spacecraft than do radio systems.

  5. Accelerated simulation study of space charge effects in quadrupole ion traps using GPU techniques.

    PubMed

    Xiong, Xingchuang; Xu, Wei; Fang, Xiang; Deng, Yulin; Ouyang, Zheng

    2012-10-01

    Space charge effects play important roles in the performance of various types of mass analyzers. Simulation of space charge effects is often limited by the computation capability. In this study, we evaluate the method of using graphics processing unit (GPU) to accelerate ion trajectory simulation. Simulation using GPU has been compared with multi-core central processing unit (CPU), and an acceleration of about 390 times have been obtained using a single computer for simulation of up to 10(5) ions in quadrupole ion traps. Characteristics of trapped ions can be investigated at detailed levels within a reasonable simulation time. Space charge effects on the trapping capacities of linear and 3D ion traps, ion cloud shapes, ion motion frequency shift, mass spectrum peak coalescence effects between two ion clouds of close m/z are studied with the ion trajectory simulation using GPU.

  6. Accelerated Simulation Study of Space Charge Effects in Quadrupole Ion Traps Using GPU Techniques

    NASA Astrophysics Data System (ADS)

    Xiong, Xingchuang; Xu, Wei; Fang, Xiang; Deng, Yulin; Ouyang, Zheng

    2012-10-01

    Space charge effects play important roles in the performance of various types of mass analyzers. Simulation of space charge effects is often limited by the computation capability. In this study, we evaluate the method of using graphics processing unit (GPU) to accelerate ion trajectory simulation. Simulation using GPU has been compared with multi-core central processing unit (CPU), and an acceleration of about 390 times have been obtained using a single computer for simulation of up to 105 ions in quadrupole ion traps. Characteristics of trapped ions can be investigated at detailed levels within a reasonable simulation time. Space charge effects on the trapping capacities of linear and 3D ion traps, ion cloud shapes, ion motion frequency shift, mass spectrum peak coalescence effects between two ion clouds of close m/z are studied with the ion trajectory simulation using GPU.

  7. Advanced space power requirements and techniques. Task 1: Mission projections and requirements. Volume 1: Technical report

    NASA Technical Reports Server (NTRS)

    Wolfe, M. G.

    1978-01-01

    The objectives of this study were to: (1) develop projections of the NASA, DoD, and civil space power requirements for the 1980-1995 time period; (2) identify specific areas of application and space power subsystem type needs for each prospective user; (3) document the supporting and historical base, including relevant cost related measures of performance; and (4) quantify the benefits of specific technology projection advancements. The initial scope of the study included: (1) construction of likely models for NASA, DoD, and civil space systems; (2) generation of a number of future scenarios; (3) extraction of time phased technology requirements based on the scenarios; and (4) cost/benefit analyses of some of the technologies identified.

  8. Constructive techniques for zeros of monotone mappings in certain Banach spaces.

    PubMed

    Diop, C; Sow, T M M; Djitte, N; Chidume, C E

    2015-01-01

    Let E be a 2-uniformly convex real Banach space with uniformly Gâteaux differentiable norm, and [Formula: see text] its dual space. Let [Formula: see text] be a bounded strongly monotone mapping such that [Formula: see text] For given [Formula: see text] let [Formula: see text] be generated by the algorithm: [Formula: see text]where J is the normalized duality mapping from E into [Formula: see text] and [Formula: see text] is a real sequence in (0, 1) satisfying suitable conditions. Then it is proved that [Formula: see text] converges strongly to the unique point [Formula: see text] Finally, our theorems are applied to the convex minimization problem.

  9. AdS/QCD, Light-Front Holography, and Sublimated Gluons

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    The gauge/gravity duality leads to a simple analytical and phenomenologically compelling nonperturbative approximation to the full light-front QCD Hamiltonian - 'Light-Front Holography', which provides a Lorentz-invariant first-approximation to QCD, and successfully describes the spectroscopy of light-quark meson and baryons, their elastic and transition form factors, and other hadronic properties. The bound-state Schroedinger and Dirac equations of the soft-wall AdS/QCD model predict linear Regge trajectories which have the same slope in orbital angular momentum L and radial quantum number n for both mesons and baryons. Light-front holography connects the fifth-dimensional coordinate of AdS space z to an invariant impact separation variable {zeta} in 3+1 space at fixed light-front time. A key feature is the determination of the frame-independent light-front wavefunctions of hadrons - the relativistic analogs of the Schroedinger wavefunctions of atomic physics which allow one to compute form factors, transversity distributions, spin properties of the valence quarks, jet hadronization, and other hadronic observables. One thus obtains a one-parameter color-confining model for hadron physics at the amplitude level. AdS/QCD also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function with an infrared fixed point which agrees with the effective coupling a{sub g1} (Q{sup 2}) extracted from measurements of the Bjorken sum rule below Q{sup 2} < 1 GeV{sup 2}. This is consistent with a flux-tube interpretation of QCD where soft gluons with virtualities Q{sup 2} < 1 GeV{sup 2} are sublimated into a color-confining potential for quarks. We discuss a number of phenomenological hadronic properties which support this picture.

  10. Development and comparison of projection and image space 3D nodule insertion techniques

    NASA Astrophysics Data System (ADS)

    Robins, Marthony; Solomon, Justin; Sahbaee, Pooyan; Samei, Ehsan

    2016-04-01

    This study aimed to develop and compare two methods of inserting computerized virtual lesions into CT datasets. 24 physical (synthetic) nodules of three sizes and four morphologies were inserted into an anthropomorphic chest phantom (LUNGMAN, KYOTO KAGAKU). The phantom was scanned (Somatom Definition Flash, Siemens Healthcare) with and without nodules present, and images were reconstructed with filtered back projection and iterative reconstruction (SAFIRE) at 0.6 mm slice thickness using a standard thoracic CT protocol at multiple dose settings. Virtual 3D CAD models based on the physical nodules were virtually inserted (accounting for the system MTF) into the nodule-free CT data using two techniques. These techniques include projection-based and image-based insertion. Nodule volumes were estimated using a commercial segmentation tool (iNtuition, TeraRecon, Inc.). Differences were tested using paired t-tests and R2 goodness of fit between the virtually and physically inserted nodules. Both insertion techniques resulted in nodule volumes very similar to the real nodules (<3% difference) and in most cases the differences were not statistically significant. Also, R2 values were all <0.97 for both insertion techniques. These data imply that these techniques can confidently be used as a means of inserting virtual nodules in CT datasets. These techniques can be instrumental in building hybrid CT datasets composed of patient images with virtually inserted nodules.

  11. Fabrication technique of large-scale lightweight SiC space mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Ge; Zhao, Rucheng; Zhao, Wenxing

    2007-12-01

    Silicon carbide (SiC) is a new type candidate material for large-scale lightweight space mirror. Its low thermal distortion, high stiffness, high optical quality, and its dimensional stability are better than other traditional optical substrate materials such as ULE, Zerodure, Beryllium (Be) and so on. In this paper, the lightweight silicon carbide space mirror blank was fabricated by reaction sintering. As a space born mirror material, silicon carbide must be an optical grade ceramic. So we prepared the silicon carbide green body with gel-casting method. Then some carbon materials were supplemented into the green body which will bring reaction-sintering with silicon in a vacuum furnace during 1500-1600°C, ultimately the reaction bonded silicon carbide was made. The diameter of SiC space mirror blank we have made is 680mm. If expanding the size of the vacuum furnace, bigger mirror blank can be obtained. The test results show that the mechanical and thermal properties of RB-SiC are excellent with bending strength of 350MPa, fracture toughness of 4.1 MPaÂ.m1/2 and coefficient of thermal expansion(CET) of 2.67×10-6/K. The surface roughness(RMS) could be better than 3nm.

  12. Development and Implementation of Joint Programs in Laser Ranging and Other Space Geodetic Techniques

    NASA Technical Reports Server (NTRS)

    Pearlman, Michael R.; Carter, David (Technical Monitor)

    2004-01-01

    This progress report discusses the status and progress made in joint international programs including: 1) WEGENER; 2) Arabian Peninsula program; 3) Asia-Pacific Space Geodynamics (APSG) program; 4) the Fourteenth International Workshop on Laser Ranging; 5) the International Laser Ranging Service; and 6) current support for the NASA network.

  13. From detection to deflection: Mitigation techniques for hidden global threats of natural space objects with short warning time

    NASA Astrophysics Data System (ADS)

    Hussein, Alaa; Rozenheck, Oshri; Entrena Utrilla, Carlos Manuel

    2016-09-01

    Throughout recorded history, hundreds of Earth impacts have been reported, with some catastrophic localized consequences. Based on the International Space University (ISU) Planetary Defense project named READI, we address the impact event problem by giving recommendations for the development of a planetary defense program. This paper reviews the current detection and tracking techniques and gives a set of recommendations for a better preparation to shield Earth from asteroid and cometary impacts. We also extend the use of current deflection techniques and propose a new compilation of those to deflect medium-sized potentially hazardous objects (PHOs). Using an array of techniques from high-energy lasers to defensive missiles, we present a set of protective layers to defend our planet. The paper focused on threats with a short warning period from discovery to impact with Earth, within few years.

  14. A modified SAG technique for the fabrication of DWDM DFB laser arrays with highly uniform wavelength spacings.

    PubMed

    Zhang, Can; Liang, Song; Zhu, Hongliang; Wang, Baojun; Wang, Wei

    2012-12-31

    A modified selective area growth (SAG) technique, in which the effective index of only the upper separate confinement heterostructure (SCH) layer are modulated to obtain different emission wavelengths, is reported for the fabrication of dense wavelength division multiplexing (DWDM) multi-wavelength laser arrays (MWLAs). InP based 1.5 μm distributed feedback (DFB) laser arrays with 0.8 nm, 0.42 nm, and 0.19 nm channel separations are demonstrated, all showing highly uniform wavelength spacings. The standard deviation of the distribution of the wavelength residues with respect to the corresponding linear fitting values is 0.0672 nm, which is a lot smaller than those of the MWLAs fabricated by other techniques including electron beam lithography. These results indicate that our SAG technique which needs only a simple procedure is promising for the fabrication of low cost DWDM MWLAs.

  15. A model-based 3D template matching technique for pose acquisition of an uncooperative space object.

    PubMed

    Opromolla, Roberto; Fasano, Giancarmine; Rufino, Giancarlo; Grassi, Michele

    2015-03-16

    This paper presents a customized three-dimensional template matching technique for autonomous pose determination of uncooperative targets. This topic is relevant to advanced space applications, like active debris removal and on-orbit servicing. The proposed technique is model-based and produces estimates of the target pose without any prior pose information, by processing three-dimensional point clouds provided by a LIDAR. These estimates are then used to initialize a pose tracking algorithm. Peculiar features of the proposed approach are the use of a reduced number of templates and the idea of building the database of templates on-line, thus significantly reducing the amount of on-board stored data with respect to traditional techniques. An algorithm variant is also introduced aimed at further accelerating the pose acquisition time and reducing the computational cost. Technique performance is investigated within a realistic numerical simulation environment comprising a target model, LIDAR operation and various target-chaser relative dynamics scenarios, relevant to close-proximity flight operations. Specifically, the capability of the proposed techniques to provide a pose solution suitable to initialize the tracking algorithm is demonstrated, as well as their robustness against highly variable pose conditions determined by the relative dynamics. Finally, a criterion for autonomous failure detection of the presented techniques is presented.

  16. A Model-Based 3D Template Matching Technique for Pose Acquisition of an Uncooperative Space Object

    PubMed Central

    Opromolla, Roberto; Fasano, Giancarmine; Rufino, Giancarlo; Grassi, Michele

    2015-01-01

    This paper presents a customized three-dimensional template matching technique for autonomous pose determination of uncooperative targets. This topic is relevant to advanced space applications, like active debris removal and on-orbit servicing. The proposed technique is model-based and produces estimates of the target pose without any prior pose information, by processing three-dimensional point clouds provided by a LIDAR. These estimates are then used to initialize a pose tracking algorithm. Peculiar features of the proposed approach are the use of a reduced number of templates and the idea of building the database of templates on-line, thus significantly reducing the amount of on-board stored data with respect to traditional techniques. An algorithm variant is also introduced aimed at further accelerating the pose acquisition time and reducing the computational cost. Technique performance is investigated within a realistic numerical simulation environment comprising a target model, LIDAR operation and various target-chaser relative dynamics scenarios, relevant to close-proximity flight operations. Specifically, the capability of the proposed techniques to provide a pose solution suitable to initialize the tracking algorithm is demonstrated, as well as their robustness against highly variable pose conditions determined by the relative dynamics. Finally, a criterion for autonomous failure detection of the presented techniques is presented. PMID:25785309

  17. Extraterrestrial Hemorrhage Control: Terrestrial Developments in Technique, Technology, and Philosophy with Applicability to Traumatic Hemorrhage in Space

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, Andrew; Dawson, David; Campbell, Mark; Jones, Jeff; Ball, Chad G.; Hamilton, Douglas R.; Dulchavsky, Scott; McBeth, Paul; Holcomb, John

    2004-01-01

    Managing injury and illness during long duration space flight limits efforts to explore beyond low earths orbit. Traumatic injury may be expected to occur in space and is a frequent cause of preventable deaths, often related to uncontrolled or ongoing hemorrhage (H). Such bleeding causes 40% of terrestrial injury mortality. Current guidelines emphasize early control of H compared to intravenous infusions. Recent advances in surgical and critical care may be applicable to trauma care in space, with appropriate considerations of the extreme logistical and personnel limitations. Methods: Recent developments in technique, resuscitation fluids, hemoglobin (Hb) substitutes, hemostatic agents, interventional angiography, damage control principles, and concepts related to suspended animation were reviewed. Results: H associated with instability frequently requires definitive intervention. Direct pressure should be applied to all compressible bleeding, but novel approaches are required for intracavitary noncompressible bleeding. Intravenous hemostatic agents such as recombinant Factor VII may facilitate hemostasis especially when combined with a controlled hypotension approach. Both open and laparoscopic techniques could be used in weightlessness, but require technical expertise not likely to be available. Specific rehearsed invasive techniques such as laparotomy with packing, or arterial catherterization with with robotic intravascular embolization might be considered . Hemodynamic support, thermal manipulation, or pharmacologic induction of a state of metabolic down regulation for whole body preservation may be appropriate. Hypertonic saline, with or without dextran, may temporize vascular support and decrease reperfusion injury, with less mass than other solutions. Hb substitutes have other theoretical advantages. Conclusions: Terrestrial developments suggest potential novel strategies to control H in space, but will required a coordinated program of evaluation and

  18. Inversion technique for IR heterodyne sounding of stratospheric constituents from space platforms

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Shapiro, G. L.; Alvarez, J. M.

    1981-01-01

    The techniques which have been employed for inversion of IR heterodyne measurements for remote sounding of stratospheric trace constituents usually rely on either geometric effects based on limb-scan observations (i.e., onion peel techniques) or spectral effects by using weighting functions corresponding to different frequencies of an IR spectral line. An experimental approach and inversion technique are discussed which optimize the retrieval of concentration profiles by combining the geometric and the spectral effects in an IR heterodyne receiver. The results of inversions of some synthetic CIO spectral lines corresponding to solar occultation limb scans of the stratosphere are presented, indicating considerable improvement in the accuracy of the retrieved profiles. The effects of noise on the accuracy of retrievals are discussed for realistic situations.

  19. Validation of attitude/deformation sensing techniques for space flexible manipulators

    NASA Astrophysics Data System (ADS)

    Gasbarri, Paolo; Palmerini, Giovanni B.; Coppotelli, Giuliano; Toglia, Chiara

    2009-01-01

    This paper proposes an approach that makes use of two different techniques to sense and identify both the rigid attitude motion and the flexible dynamics of a manipulator. With the first technique, an accurate attitude motion determination, based on the use of a global navigation satellite systems (GNSS) signals, is performed. For this purpose, some antennas are placed on the manipulator in order to obtain the observable phase of the GNSS signal. The second technique, based on the use of accelerometer sensors, is used in order to identify the dynamic signature during the motion of the flexible link. Specifically, the modal parameters are estimated using data recorded from accelerometers, conveniently placed on the structure, by means of an output-only based approach. The developed algorithms used for both the attitude estimation and the output-only modal analysis are validated by experimental activities carried out on an in-house testbed representing a two flexible arm manipulator.

  20. Reducing wrong patient selection errors: exploring the design space of user interface techniques.

    PubMed

    Sopan, Awalin; Plaisant, Catherine; Powsner, Seth; Shneiderman, Ben

    2014-01-01

    Wrong patient selection errors are a major issue for patient safety; from ordering medication to performing surgery, the stakes are high. Widespread adoption of Electronic Health Record (EHR) and Computerized Provider Order Entry (CPOE) systems makes patient selection using a computer screen a frequent task for clinicians. Careful design of the user interface can help mitigate the problem by helping providers recall their patients' identities, accurately select their names, and spot errors before orders are submitted. We propose a catalog of twenty seven distinct user interface techniques, organized according to a task analysis. An associated video demonstrates eighteen of those techniques. EHR designers who consider a wider range of human-computer interaction techniques could reduce selection errors, but verification of efficacy is still needed.