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Sample records for discrete hypoechoic ring

  1. Discrete breathers for a discrete nonlinear Schrödinger ring coupled to a central site.

    PubMed

    Jason, Peter; Johansson, Magnus

    2016-01-01

    We examine the existence and properties of certain discrete breathers for a discrete nonlinear Schrödinger model where all but one site are placed in a ring and coupled to the additional central site. The discrete breathers we focus on are stationary solutions mainly localized on one or a few of the ring sites and possibly also the central site. By numerical methods, we trace out and study the continuous families the discrete breathers belong to. Our main result is the discovery of a split bifurcation at a critical value of the coupling between neighboring ring sites. Below this critical value, families form closed loops in a certain parameter space, implying that discrete breathers with and without central-site occupation belong to the same family. Above the split bifurcation the families split up into several separate ones, which bifurcate with solutions with constant ring amplitudes. For symmetry reasons, the families have different properties below the split bifurcation for even and odd numbers of sites. It is also determined under which conditions the discrete breathers are linearly stable. The dynamics of some simpler initial conditions that approximate the discrete breathers are also studied and the parameter regimes where the dynamics remain localized close to the initially excited ring site are related to the linear stability of the exact discrete breathers.

  2. Spring flood reconstruction from continuous and discrete tree ring series

    NASA Astrophysics Data System (ADS)

    Boucher, ÉTienne; Ouarda, Taha B. M. J.; BéGin, Yves; Nicault, Antoine

    2011-07-01

    This study proposes a method to reconstruct past spring flood discharge from continuous and discrete tree ring chronologies, since both have their respective strengths and weaknesses in northern environments. Ring width or density series provide uninterrupted records that are indirectly linked to regional discharge through a concomitant effect of climate on tree growth and streamflow. Conversely, discrete event chronologies constitute conspicuous records of past high water levels since they are constructed from trees that are directly damaged by the flood. However, the uncertainty of discrete series increases toward the past, and their relationships with spring discharge are often nonlinear. To take advantage of these two sources of information, we introduce a new transfer model technique on the basis of generalized additive model (GAM) theory. The incorporation of discrete predictors and the evaluation of the robustness of the nonlinear relationships are assessed using a jackknife procedure. We exemplify our approach in a reconstruction of May water supplies to the Caniapiscau hydroelectric reservoir in northern Quebec, Canada. We used earlywood density measurements as continuous variables and ice-scar dates around Lake Montausier in the James Bay area as a discrete variable. Strong calibration (0.57 < 0.61 < 0.75) and validation (0.27 < 0.44 < 0.58) R2 statistics were obtained, thus highlighting the usefulness of the model. Our reconstruction suggests that, since ˜1965, spring floods have become more intense and variable in comparison with the last 150 years. We argue that a similar procedure can be used in each case where discrete and continuous tree ring proxies are used together to reconstruct past spring floods.

  3. Discrete Element Model for Suppression of Coffee-Ring Effect

    PubMed Central

    Xu, Ting; Lam, Miu Ling; Chen, Ting-Hsuan

    2017-01-01

    When a sessile droplet evaporates, coffee-ring effect drives the suspended particulate matters to the droplet edge, eventually forming a ring-shaped deposition. Because it causes a non-uniform distribution of solid contents, which is undesired in many applications, attempts have been made to eliminate the coffee-ring effect. Recent reports indicated that the coffee-ring effect can be suppressed by a mixture of spherical and non-spherical particles with enhanced particle-particle interaction at air-water interface. However, a model to comprehend the inter-particulate activities has been lacking. Here, we report a discrete element model (particle system) to investigate the phenomenon. The modeled dynamics included particle traveling following the capillary flow with Brownian motion, and its resultant 3D hexagonal close packing of particles along the contact line. For particles being adsorbed by air-water interface, we modeled cluster growth, cluster deformation, and cluster combination. We found that the suppression of coffee-ring effect does not require a circulatory flow driven by an inward Marangoni flow at air-water interface. Instead, the number of new cluster formation, which can be enhanced by increasing the ratio of non-spherical particles and the overall number of microspheres, is more dominant in the suppression process. Together, this model provides a useful platform elucidating insights for suppressing coffee-ring effect for practical applications in the future. PMID:28216639

  4. Discrete Element Model for Suppression of Coffee-Ring Effect

    NASA Astrophysics Data System (ADS)

    Xu, Ting; Lam, Miu Ling; Chen, Ting-Hsuan

    2017-02-01

    When a sessile droplet evaporates, coffee-ring effect drives the suspended particulate matters to the droplet edge, eventually forming a ring-shaped deposition. Because it causes a non-uniform distribution of solid contents, which is undesired in many applications, attempts have been made to eliminate the coffee-ring effect. Recent reports indicated that the coffee-ring effect can be suppressed by a mixture of spherical and non-spherical particles with enhanced particle-particle interaction at air-water interface. However, a model to comprehend the inter-particulate activities has been lacking. Here, we report a discrete element model (particle system) to investigate the phenomenon. The modeled dynamics included particle traveling following the capillary flow with Brownian motion, and its resultant 3D hexagonal close packing of particles along the contact line. For particles being adsorbed by air-water interface, we modeled cluster growth, cluster deformation, and cluster combination. We found that the suppression of coffee-ring effect does not require a circulatory flow driven by an inward Marangoni flow at air-water interface. Instead, the number of new cluster formation, which can be enhanced by increasing the ratio of non-spherical particles and the overall number of microspheres, is more dominant in the suppression process. Together, this model provides a useful platform elucidating insights for suppressing coffee-ring effect for practical applications in the future.

  5. Thermal depinning of fluxons in discrete Josephson rings

    SciTech Connect

    Mazo, J. J.; Naranjo, F.; Segall, K.

    2008-11-01

    We study the thermal depinning of single fluxons in rings made of Josephson junctions. Due to thermal fluctuations a fluxon can be excited from its energy minima and move through the array, causing a voltage across each junction. We find that for the initial depinning, the fluxon behaves as a single particle and follows a Kramers-type escape law. However, under some conditions this single-particle description breaks down. At low values of the discreteness parameter and low values of the damping, the depinning rate is larger than what the single-particle result would suggest. In addition, for some values of the parameters the fluxon can undergo low-voltage diffusion before switching to the high-voltage whirling mode. This type of diffusion is similar to phase diffusion in a single junction but occurs without frequency-dependent damping. We study the switching to the whirling state as well.

  6. Energy transfer, orbital angular momentum, and discrete current in a double-ring fiber array

    SciTech Connect

    Alexeyev, C. N.; Volyar, A. V.; Yavorsky, M. A.

    2011-12-15

    We study energy transfer and orbital angular momentum of supermodes in a double-ring array of evanescently coupled monomode optical fibers. The structure of supermodes and the spectra of their propagation constants are obtained. The geometrical parameters of the array, at which the energy is mostly confined within the layers, are determined. The developed method for finding the supermodes of concentric arrays is generalized for the case of multiring arrays. The orbital angular momentum carried by a supermode of a double-ring array is calculated. The discrete lattice current is introduced. It is shown that the sum of discrete currents over the array is a conserved quantity. The connection of the total discrete current with orbital angular momentum of discrete optical vortices is made.

  7. Ring discretization of the wave spectrum for sea surface simulation.

    PubMed

    Varela, Jose Miguel; Guedes Soares, Carlos

    2014-01-01

    Although interactive computer-generated ocean scenes based on real wave spectra are impressively realistic, they usually don't exhibit the original sea state's statistical properties. This might be unacceptable for applications in which the sea surface height field's correctness is important, such as 3D ship simulators for training professionals. Researchers have developed a discretization of the wave spectrum that obtains a sea state statistically more equivalent to the original. This method can also improve the scene's visual realism and real-time performance.

  8. Direct and inverse problems in radiation of sound from discrete random sources on two coaxial rings

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    1979-01-01

    An analytical model consisting of two ring sources of sound is developed to study the direct radiation in terms of correlation, coherence, and phase and also to aid in solving the inverse-radiation problem of determining the noise source in terms of farfield measurements. The rings consist of discrete sources which are either monopoles or quadrupoles with Gaussian autocorrelations. Only adjacent sources, both within and between the rings, are correlated. Results show that from the farfield information one can determine when the sources are compact or noncompact with respect to the acoustic wavelength and distinguish between the types of sources. In addition, from the inverse-radiation approach one can recover the center of mass, the location and separation distance of the ring, and the respective diameters.

  9. Direct and inverse problems in radiation of sound from discrete random sources on two coaxial rings

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    1979-01-01

    An analytical model consisting of two ring sources of sound is developed to study the direct radiation in terms of correlation, coherence, and phase and also to aid in solving the inverse-radiation problem of determining the noise source in terms of farfield measurements. The rings consist of discrete sources which are either monopoles or quadrupoles with Gaussian autocorrelations. Only adjacent sources, both within and between the rings, are correlated. Results show that from the farfield information one can determine when the sources are compact or noncompact with respect to the acoustic wavelength and distinguish between the types of sources. In addition, from the inverse-radiation approach one can recover the center of mass, the location and separation distance of the ring, and the respective diameters.

  10. Hypoechoic media: a landmark for intravascular ultrasonic imaging

    NASA Astrophysics Data System (ADS)

    Gussenhoven, Elma J.; Bom, Nicolaas; Li, Wenguang; van Urk, Hero; Pietermann, Herman; van Suylen, Robert J.; Salem, H. K.

    1991-05-01

    This paper describes the in vitro (40 MHz) and in vivo (30 MHz) results of studies performed on human vessels using a mechanically rotated single element ultrasonic imaging system. The in vitro images were matched with the corresponding histologic cross-sections. Morphology of vessels and possibility to determine the extent of atherosclerosis were assessed by two blinded observers. Echographic images with an echolucent zone were seen to correspond with muscular type of arteries. The echographic images showing no echographic distinction between the various layers were seen to correspond with either elastic type of arteries, veins, veins used for bypass, or bypass Goretex grafts. The extent of atherosclerosis could only be assessed in the muscular type of artery. The data showed close correlation with histology (r = 0.89). In vivo studies (30 patients) revealed a characteristic three-layered appearance of the distal iliac and femoral artery. Normal cross-sections were readily differentiated from non- obstructive and obstructive lesions. In all these patients the hypoechoic muscular media served as an important landmark.

  11. Distribution of Ejecta in Analog Tephra Rings from Discrete Single and Multiple Subsurface Explosions

    NASA Astrophysics Data System (ADS)

    Graettinger, A. H.; Valentine, G. A.; Sonder, I.; Ross, P. S.; White, J. D. L.

    2015-12-01

    Buried-explosion experiments were used to investigate the spatial and volumetric distribution of extra-crater ejecta resulting from a range of explosion configurations with and without a crater present. Explosion configuration is defined in terms of scaled depth, the relationship between depth of burial and the cube root of explosion energy, where an optimal scaled depth explosion produces the largest crater diameter for a given energy. The multiple explosion experiments provide an analog for the formation of maar-diatreme ejecta deposits and the deposits of discrete explosions through existing conduits and hydrothermal systems. Experiments produced meter-sized craters with ejecta distributed between three major facies based on morphology and distance from the crater center. The proximal deposits form a constructional steep-sided ring that extends no more than two-times the crater radius away from center. The medial deposits form a low-angle continuous blanket that transitions with distance into the isolated clasts of the distal ejecta. Single explosion experiments produce a trend of increasing volume proportion of proximal ejecta as scaled depth increases (from 20-90% vol.). Multiple explosion experiments are dominated by proximal deposits (>90% vol.) for all but optimal scaled depth conditions (40-70% vol.). In addition to scaled depth, the presence of a crater influences jet shape and how the jet collapses, resulting in two end-member depositional mechanisms that produce distinctive facies. The experiments use one well-constrained explosion mechanism and, consequently, the variations in depositional facies and distribution are the result of conditions independent of that mechanism. Previous interpretations have invoked variations in fragmentation as the cause of this variability, but these experiments should help with a more complete reconstruction of the configuration and number of explosions that produce a tephra ring.

  12. Hypoechoic renal pyramids: sonographic visualization in older children and young adults.

    PubMed

    Einstein, D M; Singer, A A; Paushter, D M; Nasif, A; Nally, J V

    1992-01-01

    The frequency and degree of visualization of medullary pyramids in a normal population, aged 10-29 years, was analyzed. Hypoechoic pyramids were visualized in 42% of right kidneys in subjects aged 10-18 years and in 27% of subjects aged 19-29 years. Prominently hypoechoic pyramids, mimicking the appearance of neonatal kidneys, were seen in an additional 34% of subjects aged 10-18 years and in 16% aged 19-29 years. Prominent pyramids were present in 50% of subjects with renal cortical echogenicity (RCE) equal to liver, but also in 21% of subjects with RCE less than liver. Our study expands the age at which prominently hypoechoic medullary pyramids can be considered a normal finding. This may relate to recent improvements in ultrasound technology.

  13. Two-dimensionally stacked heterometallic layers hosting a discrete chair dodecameric ring of water clusters: synthesis and structural study.

    PubMed

    Kenfack Tsobnang, Patrice; Wenger, Emmanuel; Biache, Coralie; Lambi Ngolui, John; Ponou, Siméon; Dahaoui, Slimane; Lecomte, Claude

    2014-10-01

    The stacked two-dimensional supramolecular compound catena-{Co(amp)3Cr(ox)3·6H2O} (amp = 2-picolylamine, ox = oxalate) has been synthesized from the bimolecular approach using hydrogen bonds. It is built from layers in which both Co(amp)(3+) (D) and Cr(ox)(3-) (A) ions are bonded in a repeating DADADA… pattern along the a and c axes by multiple hydrogen bonds. These layers host a well resolved R12 dodecameric discrete ring of water clusters built by six independent molecules located around the 2c centrosymmetric Wyckoff positions of the P21/n space group in which the compound crystallizes. These clusters are ranged along the [001] direction, occupy 733.5 Å(3) (22.0%) of the unit cell and have a chair conformation via 12 hydrogen bonds. The water molecules of the cluster are linked with stronger hydrogen bonds than those between the cluster and its host, which explains the single continuous step of the dehydration process of the compound.

  14. Histotype differentiation of hypo-echoic renal tumors on CEUS: usefulness of enhancement homogeneity and intensity.

    PubMed

    Lu, Qing; Xue, Li-yun; Huang, Bei-jian; Wang, Wen-ping; Li, Cui-xian

    2015-08-01

    The purpose of this study is to evaluate qualitative and quantitative analysis of contrast-enhanced ultrasound (CEUS) in differential diagnoses of hypo-echoic renal tumor histotypes. Our study cohort comprised 103 clear cell renal cell carcinomas (ccRCCs), 24 papillary renal cell carcinomas (pRCCs), 28 chromophobe renal cell carcinomas (cRCCs), and 34 angiomyolipomas (AMLs), hypo-echoic on ultrasound, and imaged between January 2011 and December 2013. Enhancement homogeneity and tumor-to-cortex intensity ratio (TOC ratio) were retrospectively analyzed. Overall, heterogeneous enhancement was more common in ccRCCs than AMLs, pRCCs, and cRCCs. TOC ratio showed the trend ccRCC > AML > pRCC = cRCC. Similar trends were seen in tumors <4 cm. Using heterogeneous enhancement or TOC ratio >107.5% to differentiate ccRCC from other histotypes, the sensitivity, specificity, positive and negative predictive values were 93.1%, 74.5%, 84.8%, and 87.5%, respectively. Tumors >4 cm exhibited considerable overlap in enhancement homogeneity among different histotypes. TOC ratios were similar between homo- and heterogeneously enhancing tumors for ccRCCs and for pRCCs and cRCCs, but higher in homogeneously enhancing than heterogeneously enhancing AMLs. In homo- and heterogeneously enhancing tumors, TOC ratios followed the trends ccRCCs > AMLs > pRCCs = cRCCs and ccRCCs > AMLs = pRCCs = cRCCs, respectively. With TOC ratio >105.81% and >72.37% to differentiate homo- and heterogeneously enhancing ccRCCs from other histotypes in tumors >4 cm with same enhancement homogeneity, the sensitivity, specificity, positive and negative predictive values were 70.0%, 85.7%, 70.0%, 85.7%, and 91.7%, 94.4%, 95.7%, 89.5%, respectively. CEUS homogeneity and TOC ratio are helpful in differential diagnosis of hypo-echoic renal tumor histotypes. Diameter and enhancement homogeneity should be considered when deciding the diagnostic TOC ratio cutoff.

  15. The size of juxtaluminal hypoechoic area in ultrasound images of asymptomatic carotid plaques predicts the occurrence of stroke.

    PubMed

    Kakkos, Stavros K; Griffin, Maura B; Nicolaides, Andrew N; Kyriacou, Efthyvoulos; Sabetai, Michael M; Tegos, Thomas; Makris, Gregory C; Thomas, Dafydd J; Geroulakos, George

    2013-03-01

    To test the hypothesis that the size of a juxtaluminal black (hypoechoic) area (JBA) in ultrasound images of asymptomatic carotid artery plaques predicts future ipsilateral ischemic stroke. A JBA was defined as an area of pixels with a grayscale value <25 adjacent to the lumen without a visible echogenic cap after image normalization. The size of a JBA was measured in the carotid plaque images of 1121 patients with asymptomatic carotid stenosis 50% to 99% in relation to the bulb (Asymptomatic Carotid Stenosis and Risk of Stroke study); the patients were followed for up to 8 years. The JBA had a linear association with future stroke rate. The area under the receiver-operating characteristic curve was 0.816. Using Kaplan-Meier curves, the mean annual stroke rate was 0.4% in 706 patients with a JBA <4 mm(2), 1.4% in 171 patients with a JBA 4 to 8 mm(2), 3.2% in 46 patients with a JBA 8 to 10 mm(2), and 5% in 198 patients with a JBA >10 mm(2) (P < .001). In a Cox model with ipsilateral ischemic events (amaurosis fugax, transient ischemic attack [TIA], or stroke) as the dependent variable, the JBA (<4 mm(2), 4-8 mm(2), >8 mm(2)) was still significant after adjusting for other plaque features known to be associated with increased risk, including stenosis, grayscale median, presence of discrete white areas without acoustic shadowing indicating neovascularization, plaque area, and history of contralateral TIA or stroke. Plaque area and grayscale median were not significant. Using the significant variables (stenosis, discrete white areas without acoustic shadowing, JBA, and history of contralateral TIA or stroke), this model predicted the annual risk of stroke for each patient (range, 0.1%-10.0%). The average annual stroke risk was <1% in 734 patients, 1% to 1.9% in 94 patients, 2% to 3.9% in 134 patients, 4% to 5.9% in 125 patients, and 6% to 10% in 34 patients. The size of a JBA is linearly related to the risk of stroke and can be used in risk stratification models

  16. Should Hypoechoic Lesions on Transrectal Ultrasound Be Sampled During Magnetic Resonance Imaging-targeted Prostate Biopsy?

    PubMed

    Shakir, Nabeel A; Siddiqui, M Minhaj; George, Arvin K; Kongnyuy, Michael; Ho, Richard; Fascelli, Michele; Merino, Maria J; Turkbey, Baris; Choyke, Peter L; Wood, Bradford J; Pinto, Peter A

    2017-07-01

    To determine whether supplemental biopsy of hypoechoic ultrasound lesions (HUL) incidentally found during magnetic resonance imaging (MRI)-transrectal ultrasound (TRUS) fusion-targeted prostate biopsy results in improved prostate cancer (PCa) detection. Patients underwent MRI-TRUS-targeted biopsy as part of an ongoing prospective trial from August 2007 to February 2015. For men with HUL, the biopsy pathology of HUL and MRI lesions was classified according to the updated 2014 International Society of Urological Pathology (ISUP) grading system. The detection of PCa by MRI-targeted biopsy with and without HUL biopsy was compared. Of 1260 men in the trial, 106 underwent biopsy of 119 HULs. PCa was diagnosed in 52 out of 106 men (49%) by biopsy of either MRI lesions or HUL. Biopsy of HUL in addition to MRI lesions resulted in 4 additional diagnoses of high-grade (ISUP grades 3-5) PCa versus biopsy of MRI lesions alone (20 vs 16 men, P = .046). Three of these cases were upgraded from lower grade (ISUP grades 1-2) PCa on MRI-guided biopsy alone, and only 1 case (1% of cohort) was diagnosed that would have been missed by MRI-guided biopsy alone. Supplemental biopsy of HUL did not change the PCa risk category in 96% (102 out of 106) of men with HUL. Supplemental biopsy of HUL yields a small increase in the detection of higher grade PCa as compared with biopsy of MRI lesions alone. As upgrading is rare, routinely screening for HUL during MRI-targeted biopsy remains controversial. Copyright © 2016. Published by Elsevier Inc.

  17. In vivo observation of the hypo-echoic "black hole" phenomenon in rat arterial bloodstream: a preliminary Study.

    PubMed

    Nam, Kweon-Ho; Paeng, Dong-Guk

    2014-07-01

    The "black hole," a hypo-echoic hole at the center of the bloodstream surrounded by a hyper-echoic zone in cross-sectional views, has been observed in ultrasound backscattering measurements of blood with red blood cell aggregation in in vitro studies. We investigated whether the phenomenon occurs in the in vivo arterial bloodstream of rats using a high-frequency ultrasound imaging system. Longitudinal and cross-sectional ultrasound images of the rat common carotid artery (CCA) and abdominal aorta were obtained using a 40-MHz ultrasound system. A high-frame-rate retrospective imaging mode was employed to precisely examine the dynamic changes in blood echogenicity in the arteries. When the imaging was performed with non-invasive scanning, blood echogenicity was very low in the CCA as compared with the surrounding tissues, exhibiting no hypo-echoic zone at the center of the vessel. Invasive imaging of the CCA by incising the skin and subcutaneous tissues at the imaging area provided clearer and brighter blood echo images, showing the "black hole" phenomenon near the center of the vessel in longitudinal view. The "black hole" was also observed in the abdominal aorta under direct imaging after laparotomy. The aortic "black hole" was clearly observed in both longitudinal and cross-sectional views. Although the "black hole" was always observed near the center of the arteries during the diastolic phase, it dissipated or was off-center along with the asymmetric arterial wall dilation at systole. In conclusion, we report the first in vivo observation of the hypo-echoic "black hole" caused by the radial variation of red blood cell aggregation in arterial bloodstream.

  18. Patellar tendon ultrasonography in asymptomatic active athletes reveals hypoechoic regions: a study of 320 tendons. Victorian Institute of Sport Tendon Study Group.

    PubMed

    Cook, J L; Khan, K M; Harcourt, P R; Kiss, Z S; Fehrmann, M W; Griffiths, L; Wark, J D

    1998-04-01

    To compare patellar tendon sonographic findings in active, currently asymptomatic, elite athletes with those in nonathletic controls. Cross-sectional cohort study with convenience control sample. The Victorian Institute of Sport Tendon Study Group, an institutional elite athlete study group in Australia. Two hundred elite male and female athletes from the sports of basketball, cricket, netball, and Australian rules football. Forty athletes who had current symptoms of jumper's knee were excluded from analysis, leaving 320 subject tendons in athletes who were currently asymptomatic. Twenty-seven nonathletic individuals served as controls. Sonographic patellar tendon appearance. We measured the dimensions of subject tendons and noted the presence or absence of hypoechoic regions and tendon calcification. Dimensions of hypoechoic regions were measured, and approximate cross-sectional areas were calculated. Chi-squared analysis was used to test the prevalence of hypoechoic regions in subjects and controls and men and women. In currently asymptomatic subjects, hypoechoic regions were more prevalent in athlete tendons (22%) than in controls (4%), in male subject tendons (30%) than in female subjects (14%), and in basketball players (32%) than in other athletes (9%) (all p < 0.01). Bilateral tendon abnormalities were equally prevalent in men and women but more prevalent in basketball players (15%) than in other athletes (3%) (p < 0.05). Sonographic hypoechoic regions were present in 35 of 250 (14%) patellar tendons in athletes who had never had anterior knee pain. Patellar tendon sonographic hypoechoic areas were present in asymptomatic patellar tendons of a proportion of elite athletes but rarely present in controls. This has implications for clinicians managing athletes with anterior knee pain.

  19. Solid hypo-echoic thyroid nodules on ultrasound: the diagnostic value of acoustic radiation force impulse elastography.

    PubMed

    Xu, Jun-Mei; Xu, Hui-Xiong; Xu, Xiao-Hong; Liu, Chang; Zhang, Yi-Feng; Guo, Le-Hang; Liu, Lin-Na; Zhang, Jin

    2014-09-01

    The aim of the study described here was to evaluate the diagnostic performance of acoustic radiation force impulse (ARFI) elastography in the differential diagnosis between benign and malignant solid hypo-echoic thyroid nodules (SHTNs) on ultrasound. In this retrospective study, 183 histologically proven SHTNs in 159 patients were enrolled. Conventional US, as well as Virtual Touch tissue imaging (VTI) and Virtual Touch tissue quantification (VTQ) of ARFI elastography, was performed on each nodule. The VTI features of SHTNs were divided into six grades, where higher grades represent harder tissue. VTQ was expressed as shear wave velocity, where higher shear wave velocity values indicate stiffer tissue. The sensitivity, specificity, accuracy, positive predictive value, negative predictive value and Youden index for ultrasound and ARFI were assessed. The 183 pathologically proven SHTNs included 117 benign and 66 malignant lesions. Nodules classified as VTI grades IV to VI were more frequently malignant (49/66, 74.2%) than benign (10/117, 8.5%) (p < 0.001). The mean shear wave velocity of VTQ for malignant SHTNs (mean ± standard deviation, 4.65 ± 2.68 m/s; range, 1.36-9 m/s) was significantly higher than that for benign SHTNs (2.34 ± 0.85 m/s, 0-5.7 m/s) (p < 0.001). The sensitivity, specificity, accuracy, positive predictive value, negative predictive value and Youden index were 27.3%-84.8%, 13.7%-89.7%, 39.3%-69.4%, 35.7%-60%, 61.5%-78.5%, and -0.015 to 0.37 for ultrasound; 68.2%, 76.9%, 73.8%, 62.5%, 81.1% and 0.451 for VTQ; and 74.2%, 91.5%, 85.2%, 83.1%, 86.3% and 0.657 for VTI, respectively. ARFI elastography performed at a superior level, compared with conventional ultrasound, in the differential diagnosis between malignant and benign SHTNs. The diagnostic performance of VTI is higher than that of VTQ.

  20. Emission of Discrete Vortex Rings by a Vibrating Grid In Superfluid {sup 3}He-B: A Precursor to Quantum Turbulence

    SciTech Connect

    Bradley, D.I.; Clubb, D.O.; Fisher, S.N.; Guenault, A.M.; Haley, R.P.; Matthews, C.J.; Pickett, G.R.; Tsepelin, V.; Zaki, K.

    2005-07-15

    We report a transition in the vorticity generated by a grid moving in the B phase of superfluid {sup 3}He at T<ring production at low grid velocities to quantum turbulence at higher velocities and that independent isolated vortex rings provide the precursors to the developed turbulence. Furthermore we believe that this may be a feature of all quantum turbulence arising from repetitive mechanical agitation.

  1. Discrete dislocations in graphene

    NASA Astrophysics Data System (ADS)

    Ariza, M. P.; Ortiz, M.

    2010-05-01

    In this work, we present an application of the theory of discrete dislocations of Ariza and Ortiz (2005) to the analysis of dislocations in graphene. Specifically, we discuss the specialization of the theory to graphene and its further specialization to the force-constant model of Aizawa et al. (1990). The ability of the discrete-dislocation theory to predict dislocation core structures and energies is critically assessed for periodic arrangements of dislocation dipoles and quadrupoles. We show that, with the aid of the discrete Fourier transform, those problems are amenable to exact solution within the discrete-dislocation theory, which confers the theory a distinct advantage over conventional atomistic models. The discrete dislocations exhibit 5-7 ring core structures that are consistent with observation and result in dislocation energies that fall within the range of prediction of other models. The asymptotic behavior of dilute distributions of dislocations is characterized analytically in terms of a discrete prelogarithmic energy tensor. Explicit expressions for this discrete prelogarithmic energy tensor are provided up to quadratures.

  2. Ba4KFe3O9: A Novel Ferrite Containing Discrete Six-member Rings of Corner-sharing FeO4 Tetrahedra

    PubMed Central

    Zhao, Qingbiao; Nellutla, Saritha; Son, Won-Joon; Vaughn, Shae A.; Ye, Longfei; Smith, Mark D.; Caignaert, Vincent; Lufaso, Michael; Pekarek, Thomas M.; Smirnov, Alex I.; Whangbo, Myung-Hwan

    2011-01-01

    Single crystals of a new iron containing oxide, Ba4KFe3O9, were grown from a hydroxide melt and the crystal structure was determined by single crystal x-ray diffraction. This ferrite represents the first complex oxide containing isolated 6-member rings of corner sharing FeO4 tetrahedra. Mössbauer measurements are indicative of two tetrahedral high-spin Fe3+ coordination environments. The observed magnetic moment (~3.9 BM) at 400 K is significantly lower than the calculated spin-only (~5.2 BM) value indicating the presence of strong antiferromagnetic interactions in the oxide. Our density functional calculations confirm the strong antiferromagnetic coupling between adjacent Fe3+ sites within each 6-member ring and estimate the nearest neighbor spin exchange integral as ~200 K; next nearest neighbor interactions are shown to be negligible. The lower than expected effective moment for Ba4KFe3O9 calculated from χT data is explained as resulting from the occupation of lower lying magnetic states in which more spins are paired. X-band (9.5 GHz) electron paramagnetic resonance (EPR) spectra of powder sample consist of a single line at g~2.01 that is characteristic of Fe3+ ions in a tetrahedral environment, thus, confirming the Mössbauer results. Further analysis of the EPR line shape reveals the presence of two types of Fe6 magnetic species with an intensity ratio of ~1:9. Both species have Lorentzian line shapes and indistinguishable g-factors but differ in the peak-to-peak line widths (δBpp). The line width ratio δBpp(major)/δBpp(minor) ~ 3.6 correlates well with the ratio of the Weiss constants, θminor/θmajor ~ 4. PMID:21905756

  3. Ba4KFe3O9: a novel ferrite containing discrete 6-membered rings of corner-sharing FeO4 tetrahedra.

    PubMed

    Zhao, Qingbiao; Nellutla, Saritha; Son, Won-Joon; Vaughn, Shae A; Ye, Longfei; Smith, Mark D; Caignaert, Vincent; Lufaso, Michael; Pekarek, Thomas M; Smirnov, Alex I; Whangbo, Myung-Hwan; zur Loye, Hans-Conrad

    2011-10-17

    Single crystals of a new iron-containing oxide, Ba(4)KFe(3)O(9), were grown from a hydroxide melt, and the crystal structure was determined by single-crystal X-ray diffraction. This ferrite represents the first complex oxide containing isolated 6-membered rings of corner-sharing FeO(4) tetrahedra. Mössbauer measurements are indicative of two tetrahedral high-spin Fe(3+) coordination environments. The observed magnetic moment (~3.9 μ(B)) at 400 K is significantly lower than the calculated spin-only (~5.2 μ(B)) value, indicating the presence of strong antiferromagnetic interactions in the oxide. Our density functional theory calculations confirm the strong antiferromagnetic coupling between adjacent Fe(3+) sites within each 6-membered ring and estimate the nearest-neighbor spin-exchange integral as ~200 K; next-nearest-neighbor interactions are shown to be negligible. The lower than expected effective magnetic moment for Ba(4)KFe(3)O(9) calculated from χT data is explained as resulting from the occupation of lower-lying magnetic states in which more spins are paired. X-band (9.5 GHz) electron paramagnetic resonance (EPR) spectra of a powder sample consist of a single line at g ~ 2.01 that is characteristic of Fe(3+) ions in a tetrahedral environment, thus confirming the Mössbauer results. Further analysis of the EPR line shape reveals the presence of two types of Fe(6) magnetic species with an intensity ratio of ~1:9. Both species have Lorentzian line shapes and indistinguishable g factors but differ in their peak-to-peak line widths (δB(pp)). The line-width ratio δB(pp)(major)/δB(pp)(minor) ~ 3.6 correlates well with the ratio of the Weiss constants, θ(minor)/θ(major) ~ 4.

  4. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Esposito, Larry

    2014-03-01

    Preface: a personal view of planetary rings; 1. Introduction: the allure of the ringed planets; 2. Studies of planetary rings 1610-2013; 3. Diversity of planetary rings; 4. Individual ring particles and their collisions; 5. Large-scale ring evolution; 6. Moons confine and sculpt rings; 7. Explaining ring phenomena; 8. N-body simulations; 9. Stochastic models; 10. Age and evolution of rings; 11. Saturn's mysterious F ring; 12. Uranus' rings and moons; 13. Neptune's partial rings; 14. Jupiter's ring-moon system after Galileo and New Horizons; 15. Ring photometry; 16. Dusty rings; 17. Concluding remarks; Afterword; Glossary; References; Index.

  5. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Esposito, Larry W.

    2011-07-01

    Preface; 1. Introduction: the allure of ringed planets; 2. Studies of planetary rings 1610-2004; 3. Diversity of planetary rings; 4. Individual ring particles and their collisions; 5. Large-scale ring evolution; 6. Moons confine and sculpt rings; 7. Explaining ring phenomena; 8. N-Body simulations; 9. Stochastic models; 10. Age and evolution of rings; 11. Saturn's mysterious F ring; 12. Neptune's partial rings; 13. Jupiter's ring-moon system after Galileo; 14. Ring photometry; 15. Dusty rings; 16. Cassini observations; 17. Summary: the big questions; Glossary; References; Index.

  6. Lectures on algebraic system theory: Linear systems over rings

    NASA Technical Reports Server (NTRS)

    Kamen, E. W.

    1978-01-01

    The presentation centers on four classes of systems that can be treated as linear systems over a ring. These are: (1) discrete-time systems over a ring of scalars such as the integers; (2) continuous-time systems containing time delays; (3) large-scale discrete-time systems; and (4) time-varying discrete-time systems.

  7. Discrete breathers in nonlinear magnetic metamaterials.

    PubMed

    Lazarides, N; Eleftheriou, M; Tsironis, G P

    2006-10-13

    Magnetic metamaterials composed of split-ring resonators or U-type elements may exhibit discreteness effects in THz and optical frequencies due to weak coupling. We consider a model one-dimensional metamaterial formed by a discrete array of nonlinear split-ring resonators where each ring interacts with its nearest neighbors. On-site nonlinearity and weak coupling among the individual array elements result in the appearance of discrete breather excitations or intrinsic localized modes, both in the energy-conserved and the dissipative system. We analyze discrete single and multibreather excitations, as well as a special breather configuration forming a magnetization domain wall and investigate their mobility and the magnetic properties their presence induces in the system.

  8. Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Cuzzi, J. N.

    2014-12-01

    The rings are changing before our eyes; structure varies on all timescales and unexpected things have been discovered. Many questions have been answered, but some answers remain elusive (see Cuzzi et al 2010 for a review). Here we highlight the major ring science progress over the mission to date, and describe new observations planned for Cassini's final three years. Ring Composition and particle sizes: The rings are nearly all water ice with no other ices - so why are they reddish? The C Ring and Cassini Division are "dirtier" than the more massive B and A Rings, as shown by near-IR and, recently, microwave observations. Particle sizes, from stellar and radio occultations, vary from place to place. Ring structure, micro and macro: numerous spiral density waves and ubiquitous "self-gravity wakes" reveal processes which fostered planet formation in the solar system and elsewhere. However, big puzzles remain regarding the main ring divisions, the C Ring plateau structures, and the B Ring irregular structure. Moonlets, inside and out, seen and unseen: Two gaps contain sizeable moonlets, but more gaps seem to contain none; even smaller embedded "propeller" objects wander, systematically or randomly, through the A ring. Rubble pile ringmoons just outside the rings may escaped from the rings, and the recently discovered "Peggy" may be trying this as we watch. Impact bombardment of the rings: Comet fragments set the rings to rippling on century-timescales, and boulders crash through hourly; meanwhile, the constant hail of infalling Kuiper belt material has a lower mass flux than previously thought. Origin and Age of the Rings: The ring mass and bombardment play key roles. The ring mass is well known everywhere but in the B Ring (where most of it is). New models suggest how tidal breakup of evolving moons may have formed massive ancient rings, of which the current ring is just a shadow. During its last three years, the Cassini tour profile will allow entirely new

  9. Neptune's rings

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This 591-second exposure of the rings of Neptune were taken with the clear filter by the Voyager 2 wide-angle camera. The two main rings are clearly visible and appear complete over the region imaged. Also visible in this image is the inner faint ring and the faint band which extends smoothly from the ring roughly halfway between the two bright rings. Both of these newly discovered rings are broad and much fainter than the two narrow rings. The bright glare is due to over-exposure of the crescent on Neptune. Numerous bright stars are evident in the background. Both bright rings have material throughout their entire orbit, and are therefore continuous. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.

  10. Ring World

    NASA Image and Video Library

    2007-03-01

    Our robotic emissary, flying high above Saturn, captured this view of an alien copper-colored ring world. The overexposed planet has deliberately been removed to show the unlit rings alone, seen from an elevation of 60 degrees

  11. Neptune Rings

    NASA Image and Video Library

    1999-10-29

    This 591-second exposure of the rings of Neptune were taken with the clear filter by NASA Voyager 2 wide-angle camera. The two main rings are clearly visible and appear complete over the region imaged.

  12. Ring Backdrop

    NASA Image and Video Library

    2011-01-03

    Saturn moon Enceladus brightly reflects sunlight before a backdrop of the planet rings and the rings shadows cast onto the planet. NASA Cassini spacecraft captured this snapshot during its flyby of the moon on Nov. 30, 2010.

  13. Ultrasound findings of diffuse metastasis of gastric signet-ring-cell carcinoma to the thyroid gland.

    PubMed

    Morita, Koji; Sakamoto, Takahiko; Ota, Shuji; Masugi, Hideo; Chikuta, Ikumi; Mashimo, Yamato; Edo, Naoki; Tokairin, Takuo; Seki, Nobuhiko; Ishikawa, Toshio

    2017-01-01

    It has been shown that metastases to the thyroid from extrathyroidal malignancies occur as solitary or multiple nodules, or may involve the whole thyroid gland diffusely. However, diffuse metastasis of gastric cancer to the thyroid is extremely rare. Here, we report a case of a 74-year-old woman with diffuse infiltration of gastric adenocarcinoma (signet-ring-cell carcinoma/poorly differentiated adenocarcinoma) cells in the thyroid. The pathological diagnosis was made based on upper gastrointestinal endoscopy with biopsy and fine-needle aspiration cytology of the thyroid. An 18F-FDG PET/CT revealed multiple lesions with increased uptake, including the bilateral thyroid gland. On thyroid ultrasound examination, diffuse enlargement with internal heterogeneity and hypoechoic reticular lines was observed. On color Doppler imaging, a blood-flow signal was not detected in these hypoechoic lines. These findings were similar to those of diffuse metastases caused by other primary cancers, such as lung cancer, as reported earlier. Therefore, the presence of hypoechoic reticular lines without blood-flow signals is probably common to diffuse thyroid metastasis from any origin and an important diagnostic finding. This is the first report to show detailed ultrasound findings of diffuse gastric cancer metastasis to the thyroid gland using color Doppler.

  14. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.

    Planetary rings are the only nearby astrophysical disks and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 10- 7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close range and in real time in planetary rings.We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk) and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally confined arcs at Neptune, Saturn, and Jupiter. Finally, every known ring system includes a substantial component of diffuse dusty rings.Planetary rings have shown themselves to be useful as detectors of planetary processes around them, including the planetary magnetic field and interplanetary impactors as well as the gravity of nearby perturbing moons. Experimental rings science has made great progress in recent decades, especially numerical simulations of self-gravity wakes and other processes but also laboratory investigations of coefficient of restitution and spectroscopic ground truth. The age of self-sustained ring systems is a matter of

  15. Vortex rings

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Leonard, Anthony

    1992-01-01

    The vortex-ring problem in fluid mechanics is examined generally in terms of formation, the steady state, the duration of the rings, and vortex interactions. The formation is studied by examining the generation of laminar and turbulent vortex rings and their resulting structures with attention given to the three stages of laminar ring development. Inviscid dynamics is addressed to show how core dynamics affects overall ring motion, and laminar vortex structures are described in two dimensions. Viscous and inviscid structures are related in terms of 'leapfrogging', head-on collisions, and collisions with a no-slip wall. Linear instability theory is shown to successfully describe observational data, although late stages in the breakdown are not completely understood. This study of vortex rings has important implications for key aerodynamic issues including sound generation, transport and mixing, and vortex interactions.

  16. Translucent Rings

    NASA Image and Video Library

    2014-12-08

    Although solid-looking in many images, Saturn's rings are actually translucent. In this picture, we can glimpse the shadow of the rings on the planet through (and below) the A and C rings themselves, towards the lower right hand corner. For centuries people have studied Saturn's rings, but questions about the structure and composition of the rings lingered. It was only in 1857 when the physicist James Clerk Maxwell demonstrated that the rings must be composed of many small particles and not solid rings around the planet, and not until the 1970s that spectroscopic evidence definitively showed that the rings are composed mostly of water ice. This view looks toward the sunlit side of the rings from about 17 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on Aug. 12, 2014 in near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 1.4 million miles (2.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 24 degrees. Image scale is 85 miles (136 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18295

  17. Widening Rings

    NASA Image and Video Library

    2010-03-18

    Saturn rings and its moon Rhea are imaged before a crescent of the planet in this image captured by NASA Cassini spacecraft. The shadows of the rings continue to grow wider after their disappearing act during the planet August 2009 equinox.

  18. Planetary Rings

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.

    1994-01-01

    Just over two decades ago, Jim Pollack made a critical contribution to our understanding of planetary ring particle properties, and resolved a major apparent paradox between radar reflection and radio emission observations. At the time, particle properties were about all there were to study about planetary rings, and the fundamental questions were, why is Saturn the only planet with rings, how big are the particles, and what are they made of? Since then, we have received an avalanche of observations of planetary ring systems, both from spacecraft and from Earth. Meanwhile, we have seen steady progress in our understanding of the myriad ways in which gravity, fluid and statistical mechanics, and electromagnetism can combine to shape the distribution of the submicron-to-several-meter size particles which comprise ring systems into the complex webs of structure that we now know them to display. Insights gained from studies of these giant dynamical analogs have carried over into improved understanding of the formation of the planets themselves from particle disks, a subject very close to Jim's heart. The now-complete reconnaissance of the gas giant planets by spacecraft has revealed that ring systems are invariably found in association with families of regular satellites, and there is ark emerging perspective that they are not only physically but causally linked. There is also mounting evidence that many features or aspects of all planetary ring systems, if not the ring systems themselves, are considerably younger than the solar system

  19. Ring Slicer

    NASA Image and Video Library

    2015-07-06

    Saturn's moon Prometheus, seen here looking suspiciously blade-like, is captured near some of its sculpting in the F ring. Prometheus' (53 miles or 86 kilometers across) orbit sometimes takes it into the F ring. When it enters the ring, it leaves a gore where its gravitational influence clears out some of the smaller ring particles. Below Prometheus, the dark lanes interior to the F ring's bright core provide examples of previous ring-moon interactions. This view looks toward the unilluminated side of the rings from about 7 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 15, 2015. The view was obtained at a distance of approximately 286,000 miles (461,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 115 degrees. Image scale is 1.7 miles (2.8 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18324

  20. Planetary Rings

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.

    1994-01-01

    Just over two decades ago, Jim Pollack made a critical contribution to our understanding of planetary ring particle properties, and resolved a major apparent paradox between radar reflection and radio emission observations. At the time, particle properties were about all there were to study about planetary rings, and the fundamental questions were, why is Saturn the only planet with rings, how big are the particles, and what are they made of? Since then, we have received an avalanche of observations of planetary ring systems, both from spacecraft and from Earth. Meanwhile, we have seen steady progress in our understanding of the myriad ways in which gravity, fluid and statistical mechanics, and electromagnetism can combine to shape the distribution of the submicron-to-several-meter size particles which comprise ring systems into the complex webs of structure that we now know them to display. Insights gained from studies of these giant dynamical analogs have carried over into improved understanding of the formation of the planets themselves from particle disks, a subject very close to Jim's heart. The now-complete reconnaissance of the gas giant planets by spacecraft has revealed that ring systems are invariably found in association with families of regular satellites, and there is ark emerging perspective that they are not only physically but causally linked. There is also mounting evidence that many features or aspects of all planetary ring systems, if not the ring systems themselves, are considerably younger than the solar system

  1. Ring King

    NASA Image and Video Library

    2014-08-18

    Saturn reigns supreme, encircled by its retinue of rings. Although all four giant planets have ring systems, Saturn's is by far the most massive and impressive. Scientists are trying to understand why by studying how the rings have formed and how they have evolved over time. Also seen in this image is Saturn's famous north polar vortex and hexagon. This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on May 4, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was acquired at a distance of approximately 2 million miles (3 million kilometers) from Saturn. Image scale is 110 miles (180 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18278

  2. Vascular rings.

    PubMed

    Backer, Carl L; Mongé, Michael C; Popescu, Andrada R; Eltayeb, Osama M; Rastatter, Jeffrey C; Rigsby, Cynthia K

    2016-06-01

    The term vascular ring refers to congenital vascular anomalies of the aortic arch system that compress the esophagus and trachea, causing symptoms related to those two structures. The most common vascular rings are double aortic arch and right aortic arch with left ligamentum. Pulmonary artery sling is rare and these patients need to be carefully evaluated for frequently associated tracheal stenosis. Another cause of tracheal compression occurring only in infants is the innominate artery compression syndrome. In the current era, the diagnosis of a vascular ring is best established by CT imaging that can accurately delineate the anatomy of the vascular ring and associated tracheal pathology. For patients with a right aortic arch there recently has been an increased recognition of a structure called a Kommerell diverticulum which may require resection and transfer of the left subclavian artery to the left carotid artery. A very rare vascular ring is the circumflex aorta that is now treated with the aortic uncrossing operation. Patients with vascular rings should all have an echocardiogram because of the incidence of associated congenital heart disease. We also recommend bronchoscopy to assess for additional tracheal pathology and provide an assessment of the degree of tracheomalacia and bronchomalacia. The outcomes of surgical intervention are excellent and most patients have complete resolution of symptoms over a period of time. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Saturn Ring

    NASA Image and Video Library

    2007-12-12

    Like Earth, Saturn has an invisible ring of energetic ions trapped in its magnetic field. This feature is known as a "ring current." This ring current has been imaged with a special camera on Cassini sensitive to energetic neutral atoms. This is a false color map of the intensity of the energetic neutral atoms emitted from the ring current through a processed called charged exchange. In this process a trapped energetic ion steals and electron from cold gas atoms and becomes neutral and escapes the magnetic field. The Cassini Magnetospheric Imaging Instrument's ion and neutral camera records the intensity of the escaping particles, which provides a map of the ring current. In this image, the colors represent the intensity of the neutral emission, which is a reflection of the trapped ions. This "ring" is much farther from Saturn (roughly five times farther) than Saturn's famous icy rings. Red in the image represents the higher intensity of the particles, while blue is less intense. Saturn's ring current had not been mapped before on a global scale, only "snippets" or areas were mapped previously but not in this detail. This instrument allows scientists to produce movies (see PIA10083) that show how this ring changes over time. These movies reveal a dynamic system, which is usually not as uniform as depicted in this image. The ring current is doughnut shaped but in some instances it appears as if someone took a bite out of it. This image was obtained on March 19, 2007, at a latitude of about 54.5 degrees and radial distance 1.5 million kilometres (920,000 miles). Saturn is at the center, and the dotted circles represent the orbits of the moon's Rhea and Titan. The Z axis points parallel to Saturn's spin axis, the X axis points roughly sunward in the sun-spin axis plane, and the Y axis completes the system, pointing roughly toward dusk. The ion and neutral camera's field of view is marked by the white line and accounts for the cut-off of the image on the left. The

  4. Fiber Ring Optical Gyroscope (FROG)

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The design, construction, and testing of a one meter diameter fiber ring optical gyro, using 1.57 kilometers of single mode fiber, are described. The various noise components: electronic, thermal, mechanical, and optical, were evaluated. Both dc and ac methods were used. An attempt was made to measure the Earth rotation rate; however, the results were questionable because of the optical and electronic noise present. It was concluded that fiber ring optical gyroscopes using all discrete components have many serious problems that can only be overcome by discarding the discrete approach and adapting an all integrated optic technique that has the laser source, modulator, detector, beamsplitters, and bias element on a single chip.

  5. Luminescent Rings

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This view shows the unlit face of Saturn's rings, visible via scattered and transmitted light. In these views, dark regions represent gaps and areas of higher particle densities, while brighter regions are filled with less dense concentrations of ring particles.

    The dim right side of the image contains nearly the entire C ring. The brighter region in the middle is the inner B ring, while the darkest part represents the dense outer B Ring. The Cassini Division and the innermost part of the A ring are at the upper-left.

    Saturn's shadow carves a dark triangle out of the lower right corner of this image.

    The image was taken in visible light with the Cassini spacecraft wide-angle camera on June 8, 2005, at a distance of approximately 433,000 kilometers (269,000 miles) from Saturn. The image scale is 22 kilometers (14 miles) per pixel.

    The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

    For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

  6. Cave Rings

    DTIC Science & Technology

    2010-10-13

    hypothesis, that cave rings are formed in the same manner as coffee rings[3], that is, due to the enhanced deposition at the edges of sessile drops ...Literature The ‘splash ring’ conjecture is described in [5]. It is claimed that 45◦ is the most probable angle for secondary drops to be ejected at, and that...ring’ is the deposit formed when a sessile drop of a solution containing dissolved particles, such as coffee or salt, dries. This was investigated by

  7. Principles of Discrete Time Mechanics

    NASA Astrophysics Data System (ADS)

    Jaroszkiewicz, George

    2014-04-01

    1. Introduction; 2. The physics of discreteness; 3. The road to calculus; 4. Temporal discretization; 5. Discrete time dynamics architecture; 6. Some models; 7. Classical cellular automata; 8. The action sum; 9. Worked examples; 10. Lee's approach to discrete time mechanics; 11. Elliptic billiards; 12. The construction of system functions; 13. The classical discrete time oscillator; 14. Type 2 temporal discretization; 15. Intermission; 16. Discrete time quantum mechanics; 17. The quantized discrete time oscillator; 18. Path integrals; 19. Quantum encoding; 20. Discrete time classical field equations; 21. The discrete time Schrodinger equation; 22. The discrete time Klein-Gordon equation; 23. The discrete time Dirac equation; 24. Discrete time Maxwell's equations; 25. The discrete time Skyrme model; 26. Discrete time quantum field theory; 27. Interacting discrete time scalar fields; 28. Space, time and gravitation; 29. Causality and observation; 30. Concluding remarks; Appendix A. Coherent states; Appendix B. The time-dependent oscillator; Appendix C. Quaternions; Appendix D. Quantum registers; References; Index.

  8. Discrete stacking of aromatic oligoamide macrocycles.

    PubMed

    Wu, Xiangxiang; Liu, Rui; Sathyamoorthy, Bharathwaj; Yamato, Kazuhiro; Liang, Guoxing; Shen, Lin; Ma, Sufang; Sukumaran, Dinesh K; Szyperski, Thomas; Fang, Weihai; He, Lan; Chen, Xuebo; Gong, Bing

    2015-05-13

    Unlike the precise structural control typical of closed assemblies, curbing the stacking of disc- and ring-shaped molecules is quite challenging. Here we report the discrete stacking of rigid aromatic oligoamide macrocycles 1. With increasing concentration, the aggregation of 1 quickly plateaus, forming a discrete oligomer, as suggested by 1D (1)H, 2D nuclear Overhauser effect, and diffusion-ordered NMR spectroscopy. Quantum-chemical calculations indicate that the tetramer of 1 is the most stable among oligomeric stacks. X-ray crystallography revealed a tetrameric stack containing identical molecules adopting two different conformations. With a defined length and an inner pore capable of accommodating distinctly different guests, the tetramers of 1 densely pack into 2D layers. Besides being a rare system of conformation-regulated supramolecular oligomerization, the discrete stacks of 1, along with their higher-order assemblies, may offer new nanotechnological applications.

  9. RADIOGRAPHIC AND ULTRASONOGRAPHIC ABDOMINAL ANATOMY IN CAPTIVE RING-TAILED LEMURS (LEMUR CATTA).

    PubMed

    Makungu, Modesta; du Plessis, Wencke M; Barrows, Michelle; Groenewald, Hermanus B; Koeppel, Katja N

    2016-06-01

    The ring-tailed lemur (Lemur catta) is primarily distributed in south and southwestern Madagascar. It is classified as an endangered species by the International Union for Conservation of Nature. Various abdominal diseases, such as hepatic lipidosis, intestinal ulcers, cystitis, urinary tract obstruction, and neoplasia (e.g., colonic adenocarcinoma and cholangiocarcinoma), have been reported in this species. The aim of this study was to describe the normal radiographic and ultrasonographic abdominal anatomy in captive ring-tailed lemurs to provide guidance for clinical use. Radiography of the abdomen and ultrasonography of the liver, spleen, kidneys, and urinary bladder were performed in 13 and 9 healthy captive ring-tailed lemurs, respectively, during their annual health examinations. Normal radiographic and ultrasonographic reference ranges for abdominal organs were established and ratios were calculated. The majority (12/13) of animals had seven lumbar vertebrae. The sacrum had mainly (12/13) three segments. Abdominal serosal detail was excellent in all animals, and hypaxial muscles were conspicuous in the majority (11/13) of animals. The spleen was frequently (12/13) seen on the ventrodorsal (VD) view and rarely (3/13) on the right lateral (RL) view. The liver was less prominent and well contained within the ribcage. The pylorus was mostly (11/13) located to the right of the midline. The right and left kidneys were visible on the RL and VD views, with the right kidney positioned more cranial and dorsal to the left kidney. On ultrasonography, the kidneys appeared ovoid on transverse and longitudinal views. The medulla was hypoechoic to the renal cortex. The renal cortex was frequently (8/9) isoechoic and rarely (1/9) hyperechoic to the splenic parenchyma. The liver parenchyma was hypoechoic (5/5) to the renal cortex. Knowledge of the normal radiographic and ultrasonographic abdominal anatomy of ring-tailed lemurs may be useful in the diagnosis of diseases and in

  10. Ringing wormholes

    SciTech Connect

    Konoplya, R.A.; Molina, C.

    2005-06-15

    We investigate the response of traversable wormholes to external perturbations through finding their characteristic frequencies and time-domain profiles. The considered solution describes traversable wormholes between the branes in the two brane Randall-Sundrum model and was previously found within Einstein gravity with a conformally coupled scalar field. The evolution of perturbations of a wormhole is similar to that of a black hole and represents damped oscillations (ringing) at intermediately late times, which are suppressed by power-law tails (proportional to t{sup -2} for monopole perturbations) at asymptotically late times.

  11. Simulation of Rings about Ellipsoidal Bodies

    NASA Astrophysics Data System (ADS)

    Gupta, Akash; Nadkarni-Ghosh, Sharvari; Sharma, Ishan

    2016-10-01

    Recent discovery of rings around Chariklo, a centaur orbiting the Sun (F. Braga-Ribas et al., 2014) and speculations of rings around minor planet, Chiron (Ortiz et al., 2015), Saturn's satellites, Rhea (Jones et al., 2008; Schenk et al., 2011), Iapetus (Ip, 2006) or exoplanets, suggest that rings about non-spherical bodies is perhaps a more general phenomenon than anticipated. As a first step towards understanding such systems, we examine the dynamical behavior of rings around similar bodies using N-body simulations. Our code employs the `local simulation method' (Wisdom & Tremaine, 1988; Salo, 1995) and accounts for particle interactions via collisions using Discrete Element Method (Cundall & Strack, 1978; Bhateja et al., 2016) and mutual gravitation. The central body has been modeled as an axisymmetric ellipsoid characterized by its axis ratio, or defined via characteristic frequencies (circular, vertical and epicyclic frequency) representing the gravitational field of an axisymmetric body. We vary the central body's characterizing parameter and observe the change in various ring properties like the granular temperature, impact frequency, radial width and vertical thickness. We also look into the effect on ring properties upon variation in the size of the central body-ring system. Further, we investigate the role of characteristic frequencies in dictating the ring dynamics, and how this could help in qualitatively estimating the ring dynamics about any arbitrary central body with symmetry about the equatorial plane and the axis normal to it.

  12. Semiconductor single crystal external ring resonator cavity laser and gyroscope

    SciTech Connect

    Spitzer, M.P.

    1993-08-31

    A ring laser is described comprising: a semiconductor single crystal external ring resonator cavity having a plurality of reflecting surfaces defined by the planes of the crystal and establishing a closed optical path; and a discrete laser medium disposed in said semiconductor single crystal external ring resonator cavity for generating coherent light in said cavity, wherein said resonator cavity is decoupled from the laser medium.

  13. Discrete Gauge Theories

    NASA Astrophysics Data System (ADS)

    Alford, Mark G.; March-Russell, John

    In this review we discuss the formulation and distinguishing characteristics of discrete gauge theories, and describe several important applications of the concept. For the abelian (ℤN) discrete gauge theories, we consider the construction of the discrete charge operator F(Σ*) and the associated gauge-invariant order parameter that distinguishes different Higgs phases of a spontaneously broken U(1) gauge theory. We sketch some of the important thermodynamic consequences of the resultant discrete quantum hair on black holes. We further show that, as a consequence of unbroken discrete gauge symmetries, Grand Unified cosmic strings generically exhibit a Callan-Rubakov effect. For non-abelian discrete gauge theories we discuss in some detail the charge measurement process, and in the context of a lattice formulation we construct the non-abelian generalization of F(Σ*). This enables us to build the order parameter that distinguishes the different Higgs phases of a non-abelian discrete lattice gauge theory with matter. We also describe some of the fascinating phenomena associated with non-abelian gauge vortices. For example, we argue that a loop of Alice string, or any non-abelian string, is super-conducting by virtue of charged zero modes whose charge cannot be localized anywhere on or around the string (“Cheshire charge”). Finally, we discuss the relationship between discrete gauge theories and the existence of excitations possessing exotic spin and statistics (and more generally excitations whose interactions are purely “topological”).

  14. Discrete Element Modeling

    SciTech Connect

    Morris, J; Johnson, S

    2007-12-03

    The Distinct Element Method (also frequently referred to as the Discrete Element Method) (DEM) is a Lagrangian numerical technique where the computational domain consists of discrete solid elements which interact via compliant contacts. This can be contrasted with Finite Element Methods where the computational domain is assumed to represent a continuum (although many modern implementations of the FEM can accommodate some Distinct Element capabilities). Often the terms Discrete Element Method and Distinct Element Method are used interchangeably in the literature, although Cundall and Hart (1992) suggested that Discrete Element Methods should be a more inclusive term covering Distinct Element Methods, Displacement Discontinuity Analysis and Modal Methods. In this work, DEM specifically refers to the Distinct Element Method, where the discrete elements interact via compliant contacts, in contrast with Displacement Discontinuity Analysis where the contacts are rigid and all compliance is taken up by the adjacent intact material.

  15. Synchronous Discrete Harmonic Oscillator

    SciTech Connect

    Antippa, Adel F.; Dubois, Daniel M.

    2008-10-17

    We introduce the synchronous discrete harmonic oscillator, and present an analytical, numerical and graphical study of its characteristics. The oscillator is synchronous when the time T for one revolution covering an angle of 2{pi} in phase space, is an integral multiple N of the discrete time step {delta}t. It is fully synchronous when N is even. It is pseudo-synchronous when T/{delta}t is rational. In the energy conserving hyperincursive representation, the phase space trajectories are perfectly stable at all time scales, and in both synchronous and pseudo-synchronous modes they cycle through a finite number of phase space points. Consequently, both the synchronous and the pseudo-synchronous hyperincursive modes of time-discretization provide a physically realistic and mathematically coherent, procedure for dynamic, background independent, discretization of spacetime. The procedure is applicable to any stable periodic dynamical system, and provokes an intrinsic correlation between space and time, whereby space-discretization is a direct consequence of background-independent time-discretization. Hence, synchronous discretization moves the formalism of classical mechanics towards that of special relativity. The frequency of the hyperincursive discrete harmonic oscillator is ''blue shifted'' relative to its continuum counterpart. The frequency shift has the precise value needed to make the speed of the system point in phase space independent of the discretizing time interval {delta}t. That is the speed of the system point is the same on the polygonal (in the discrete case) and the circular (in the continuum case) phase space trajectories.

  16. Kinetics of ring formation

    NASA Astrophysics Data System (ADS)

    Ben-Naim, E.; Krapivsky, P. L.

    2011-06-01

    We study reversible polymerization of rings. In this stochastic process, two monomers bond and, as a consequence, two disjoint rings may merge into a compound ring or a single ring may split into two fragment rings. This aggregation-fragmentation process exhibits a percolation transition with a finite-ring phase in which all rings have microscopic length and a giant-ring phase where macroscopic rings account for a finite fraction of the entire mass. Interestingly, while the total mass of the giant rings is a deterministic quantity, their total number and their sizes are stochastic quantities. The size distribution of the macroscopic rings is universal, although the span of this distribution increases with time. Moreover, the average number of giant rings scales logarithmically with system size. We introduce a card-shuffling algorithm for efficient simulation of the ring formation process and we present numerical verification of the theoretical predictions.

  17. Ringing in an HNBody Upgrade

    NASA Astrophysics Data System (ADS)

    Rimlinger, Thomas; Hamilton, Douglas; Hahn, Joseph M.

    2017-06-01

    We are in the process of developing a useful extension to the N-body integrator HNBody (Rauch & Hamilton 2002), enabling it to simulate a viscous, self-gravitating ring orbiting an oblate body. Our algorithm follows that used in the symplectic integrator epi_int (Hahn & Spitale 2013), in which the ring is simulated as many (~100) interacting, elliptic, confocal streamlines. This idea was first introduced in an analytic context by Goldreich & Tremaine (1979) and enabled rapid progress in the theory of ring evolution; since then, such discretization has been standard in the literature. While we adopt epi_int’s streamline formalism, we nevertheless improve upon its design in several ways. Epi_int uses epicyclic elements in its drift step; approximating these elements introduces small, systematic errors that build up with time. We sidestep this problem by instead using the more traditional Keplerian osculating elements. In addition, epi_int uses several particles per wire to effectively calculate the inter-gravitational forces everywhere along each streamline. We replicate this ability but can often gain a speed boost by using a single tracer particle per streamline; while this restricts us to simulating rings dominated by the m = 1 mode, this is typical of most observed narrow eccentric ringlets. We have also extended epi_int’s two dimensional algorithm into 3D. Finally, whereas epi_int is written in IDL, HNBody is written in C, which yields considerably faster integrations.Braga-Ribas et al. (2014) reported a set of narrow rings orbiting the Centaur Chariklo, but neither their investigation nor that of Pan & Wu (2016) yielded a satisfactory origin and evolution scenario. Eschewing the assumption that such rings must be short-lived, we instead argue (as in Rimlinger et al. 2016) that sufficiently eccentric rings can self-confine for hundreds of millions of years while circularizing. In this case, Chariklo may have formed rings as a KBO. We are working towards

  18. The Discrete Hanging Cable

    ERIC Educational Resources Information Center

    Peters, James V.

    2004-01-01

    Using the methods of finite difference equations the discrete analogue of the parabolic and catenary cable are analysed. The fibonacci numbers and the golden ratio arise in the treatment of the catenary.

  19. The Discrete Hanging Cable

    ERIC Educational Resources Information Center

    Peters, James V.

    2004-01-01

    Using the methods of finite difference equations the discrete analogue of the parabolic and catenary cable are analysed. The fibonacci numbers and the golden ratio arise in the treatment of the catenary.

  20. Idea Exchange: On Discrete.

    ERIC Educational Resources Information Center

    Crisler, Nancy; Froelich, Gary

    1990-01-01

    Discussed are summary recommendations concerning the integration of some aspects of discrete mathematics into existing secondary mathematics courses. Outlines of course activities are grouped into the three levels of prealgebra, algebra, and geometry. Some sample problems are included. (JJK)

  1. Ringing phenomenon of the fiber ring resonator.

    PubMed

    Ying, Diqing; Ma, Huilian; Jin, Zhonghe

    2007-08-01

    A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well.

  2. The Ring Sculptor

    NASA Image and Video Library

    2006-09-08

    Prometheus zooms across the Cassini spacecraft field of view, attended by faint streamers and deep gores in the F ring. This movie sequence of five images shows the F ring shepherd moon shaping the ring inner edge

  3. Beyond Bright Rings

    NASA Image and Video Library

    2009-12-30

    The tiny moon Pandora appears beyond the bright disk of Saturn rings in this image taken by NASA Cassini spacecraft. Pandora orbits outside the F ring and, in this image, is farther from Cassini than the rings are.

  4. Asymmetric dipolar ring

    DOEpatents

    Prosandeev, Sergey A.; Ponomareva, Inna V.; Kornev, Igor A.; Bellaiche, Laurent M.

    2010-11-16

    A device having a dipolar ring surrounding an interior region that is disposed asymmetrically on the ring. The dipolar ring generates a toroidal moment switchable between at least two stable states by a homogeneous field applied to the dipolar ring in the plane of the ring. The ring may be made of ferroelectric or magnetic material. In the former case, the homogeneous field is an electric field and in the latter case, the homogeneous field is a magnetic field.

  5. Saturn's Spectacular Ring System

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack J.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    Saturn's beautiful rings have fascinated astronomers since they were first observed by Galileo in 1610. The main rings consist of solid particles mostly in the 1 cm - 10 m range, composed primarily of water ice. The ring disk is exceptionally thin - the typical local thickness of the bright rings is tens of meters, whereas the diameter of the main rings is 250,000 km! The main rings exhibit substantial radial variations "ringlets", many of which are actively maintained via gravitational perturbations from Saturn's moons. Exterior to the main rings lie tenuous dust rings, which have little mass but occupy a very large volume of space. This seminar will emphasize the physics of ring-moon interactions, recent advances in our understanding of various aspects of the rings obtained from observations taken during 1995 when the rings appeared edge-on to the Earth and then to the Sun, and observations in subsequent years from HST.

  6. Depression: discrete or continuous?

    PubMed

    Bowins, Brad

    2015-01-01

    Elucidating the true structure of depression is necessary if we are to advance our understanding and treatment options. Central to the issue of structure is whether depression represents discrete types or occurs on a continuum. Nature almost universally operates on the basis of continuums, whereas human perception favors discrete categories. This reality might be formalized into a 'continuum principle': natural phenomena tend to occur on a continuum, and any instance of hypothesized discreteness requires unassailable proof. Research evidence for discrete types falls far short of this standard, with most evidence supporting a continuum. However, quantitative variation can yield qualitative differences as an emergent property, fostering the appearance of discreteness. Depression as a continuum is best characterized by duration and severity dimensions, with the latter understood in terms of depressive inhibition. In the absence of some degree of cognitive, emotional, social, and physical inhibition, depression should not be diagnosed. Combining the dimensions of duration and severity provides an optimal way to characterize the quantitative and related qualitative aspects of depression and to describe the overall degree of dysfunction. The presence of other symptom types occurs when anxiety, hypomanic/manic, psychotic, and personality continuums interface with the depression continuum.

  7. Breast metastases of gastric signet-ring cell carcinoma: a report of two cases and review of the literature.

    PubMed

    Iesato, Asumi; Oba, Takaaki; Ono, Mayu; Hanamura, Toru; Watanabe, Takayuki; Ito, Tokiko; Kanai, Toshiharu; Maeno, Kazuma; Ishizaka, Katsuhiko; Kitabatake, Hiroyuki; Takeuchi, Daisuke; Suzuki, Akira; Nakayama, Jun; Ito, Ken-Ichi

    2015-01-01

    It is occasionally difficult to diagnose breast metastasis of gastric carcinoma because of its rarity. However, to appropriately treat patients with breast tumors without delay, it is important to distinguish metastatic cancer from primary breast cancer. We report two cases of breast metastasis of gastric carcinoma and review the literature. The first case was a 41-year-old female diagnosed with bilateral pelvic tumors who visited the outpatient clinic because of pain and enlargement of both breasts. Ultrasonography showed diffuse hypoechoic lesions, which were enhanced on gadolinium-enhanced magnetic resonance imaging in the bilateral mammary gland. Core needle biopsy of the right breast revealed signet-ring cells, which were also identified in the resected bilateral pelvic tumors. Subsequent upper gastrointestinal endoscopy revealed signet-ring cell carcinoma in the stomach, and the bilateral breast lesions were diagnosed as metastases of gastric carcinoma. The second case was a 34-year-old female diagnosed with cervical metastasis of signet-ring cell carcinoma who was referred to the breast cancer clinic because of a nodule in the left breast detected by computed tomography. Ultrasonography showed a hypoechoic nodule that was enhanced on gadolinium-enhanced magnetic resonance imaging. Because the pathologic findings for the left breast nodule were quite similar to those of gastric cancer and its cervical metastasis, the breast nodule was diagnosed as a metastasis of gastric carcinoma. When a breast tumor is suspected to have metastasized from a primary tumor in another organ, particularly if signet-ring cells are found, the possibility that gastric cancer is present should be considered.

  8. Discrete Newtonian cosmology: perturbations

    NASA Astrophysics Data System (ADS)

    Ellis, George F. R.; Gibbons, Gary W.

    2015-03-01

    In a previous paper (Gibbons and Ellis 2014 Discrete Newtonian cosmology Class. Quantum Grav. 31 025003), we showed how a finite system of discrete particles interacting with each other via Newtonian gravitational attraction would lead to precisely the same dynamical equations for homothetic motion as in the case of the pressure-free Friedmann-Lemaître-Robertson-Walker cosmological models of general relativity theory, provided the distribution of particles obeys the central configuration equation. In this paper we show that one can obtain perturbed such Newtonian solutions that give the same linearized structure growth equations as in the general relativity case. We also obtain the Dmitriev-Zel’dovich equations for subsystems in this discrete gravitational model, and show how it leads to the conclusion that voids have an apparent negative mass.

  9. Discrete Driver Assistance

    NASA Astrophysics Data System (ADS)

    Klette, Reinhard; Jiang, Ruyi; Morales, Sandino; Vaudrey, Tobi

    Applying computer technology, such as computer vision in driver assistance, implies that processes and data are modeled as being discretized rather than being continuous. The area of stereo vision provides various examples how concepts known in discrete mathematics (e.g., pixel adjacency graphs, belief propagation, dynamic programming, max-flow/min-cut, or digital straight lines) are applied when aiming for efficient and accurate pixel correspondence solutions. The paper reviews such developments for a reader in discrete mathematics who is interested in applied research (in particular, in vision-based driver assistance). As a second subject, the paper also discusses lane detection and tracking, which is a particular task in driver assistance; recently the Euclidean distance transform proved to be a very appropriate tool for obtaining a fairly robust solution.

  10. Uranus Tenth Ring

    NASA Image and Video Library

    1996-01-29

    On Jan. 23, 1986, NASA Voyager 2 discovered a tenth ring orbiting Uranus. The tenth ring is about midway between the bright, outermost epsilon ring and the next ring down, called delta. http://photojournal.jpl.nasa.gov/catalog/PIA00035

  11. Stirling engine piston ring

    DOEpatents

    Howarth, Roy B.

    1983-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  12. Birth Control Ring

    MedlinePlus

    ... Loss Surgery? A Week of Healthy Breakfasts Shyness Birth Control Ring KidsHealth > For Teens > Birth Control Ring Print A A A What's in this ... español Anillo vaginal anticonceptivo What Is It? The birth control ring is a soft, flexible, doughnut-shaped ring ...

  13. Discrete breathers in crystals

    NASA Astrophysics Data System (ADS)

    Dmitriev, S. V.; Korznikova, E. A.; Baimova, Yu A.; Velarde, M. G.

    2016-05-01

    It is well known that periodic discrete defect-containing systems, in addition to traveling waves, support vibrational defect-localized modes. It turned out that if a periodic discrete system is nonlinear, it can support spatially localized vibrational modes as exact solutions even in the absence of defects. Since the nodes of the system are all on equal footing, it is only through the special choice of initial conditions that a group of nodes can be found on which such a mode, called a discrete breather (DB), will be excited. The DB frequency must be outside the frequency range of the small-amplitude traveling waves. Not resonating with and expending no energy on the excitation of traveling waves, a DB can theoretically conserve its vibrational energy forever provided no thermal vibrations or other perturbations are present. Crystals are nonlinear discrete systems, and the discovery in them of DBs was only a matter of time. It is well known that periodic discrete defect-containing systems support both traveling waves and vibrational defect-localized modes. It turns out that if a periodic discrete system is nonlinear, it can support spatially localized vibrational modes as exact solutions even in the absence of defects. Because the nodes of the system are all on equal footing, only a special choice of the initial conditions allows selecting a group of nodes on which such a mode, called a discrete breather (DB), can be excited. The DB frequency must be outside the frequency range of small-amplitude traveling waves. Not resonating with and expending no energy on the excitation of traveling waves, a DB can theoretically preserve its vibrational energy forever if no thermal vibrations or other perturbations are present. Crystals are nonlinear discrete systems, and the discovery of DBs in them was only a matter of time. Experimental studies of DBs encounter major technical difficulties, leaving atomistic computer simulations as the primary investigation tool. Despite

  14. New Dust Belts of Uranus: One Ring, Two Ring, Red Ring, Blue Ring

    SciTech Connect

    de Pater, I; Hammel, H B; Gibbard, S G; Showalter, M R

    2006-02-02

    We compare near-infrared observations of the recently discovered outer rings of Uranus with HST results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced via impacts into the embedded moon Mab, which apparently orbits at a location where non-gravitational perturbations favor the survival and spreading of sub-micron sized dust. R/2003 U 2 more closely resembles Saturn's G ring.

  15. Basin-ring spacing on the Moon, Mercury, and Mars

    USGS Publications Warehouse

    Pike, R.J.; Spudis, P.D.

    1987-01-01

    Radial spacing between concentric rings of impact basins that lack central peaks is statistically similar and nonrandom on the Moon, Mercury, and Mars, both inside and outside the main ring. One spacing interval, (2.0 ?? 0.3)0.5D, or an integer multiple of it, dominates most basin rings. Three analytical approaches yield similar results from 296 remapped or newly mapped rings of 67 multi-ringed basins: least-squares of rank-grouped rings, least-squares of rank and ring diameter for each basin, and averaged ratios of adjacent rings. Analysis of 106 rings of 53 two-ring basins by the first and third methods yields an integer multiple (2 ??) of 2.00.5D. There are two exceptions: (1) Rings adjacent to the main ring of multi-ring basins are consistently spaced at a slightly, but significantly, larger interval, (2.1 ?? 0.3)0.5D; (2) The 88 rings of 44 protobasins (large peak-plus-inner-ring craters) are spaced at an entirely different interval (3.3 ?? 0.6)0.5D. The statistically constant and target-invariant spacing of so many rings suggests that this characteristic may constrain formational models of impact basins on the terrestrial planets. The key elements of such a constraint include: (1) ring positions may not have been located by the same process(es) that formed ring topography; (2) ring location and emplacement of ring topography need not be coeval; (3) ring location, but not necessarily the mode of ring emplacement, reflects one process that operated at the time of impact; and (4) the process yields similarly-disposed topographic features that are spatially discrete at 20.5D intervals, or some multiple, rather than continuous. These four elements suggest that some type of wave mechanism dominates the location, but not necessarily the formation, of basin rings. The waves may be standing, rather than travelling. The ring topography itself may be emplaced at impact by this and/or other mechanisms and may reflect additional, including post-impact, influences. ?? 1987

  16. Discrete surface solitons.

    PubMed

    Makris, Konstantinos G; Suntsov, Sergiy; Christodoulides, Demetrios N; Stegeman, George I; Hache, Alain

    2005-09-15

    It is theoretically shown that discrete nonlinear surface waves are possible in waveguide lattices. These self-trapped states are located at the edge of the array and can exist only above a certain power threshold. The excitation characteristics and stability properties of these surface waves are systematically investigated.

  17. Localized Perturbations in Saturn's C Ring

    NASA Astrophysics Data System (ADS)

    Spitale, Joseph N.; Tiscareno, Matthew S.

    2016-10-01

    Years of high-resolution imaging of Saturn's rings have revealed many examples of perturbations arising from local causes. For example, the presence of 100-m-scale and smaller moonlets is inferred in the A ring based on the propeller-shaped disturbances that they create (Tiscareno et al. 2006, 2010); the F ring is shaped by regular collisions with its shepherd Prometheus, as well as with other smaller bodies orbiting in the vicinity (Murray et al. 2005, 2008); the "wisps" on the outer edge of the Keeler gap (Porco et al. 2005) may mark the locations of small moonlets that have emerged from the A ring (Tiscareno and Arnault 2015); wakes in the Huygens ringlet imply the presence of two multi-km bodies, and the irregular shape of its inner edge suggests the presence of many smaller bodies (Spitale and Hahn 2016); based on shadow measurements, the B ring contains an embedded 300-m object that produces a small propeller-shaped disturbance (Spitale and Porco 2010; Spitale and Tiscareno 2012).Here, we present evidence for localized perturbations in the C ring. The ringlet embedded in the Bond gap, near 1.470 Saturn radii, shows discrete clumps orbiting at the Keplerian rate in images spanning about eight years. The clumps are not detected in all image sequences at the expected longitudes. The Dawes ringlet, near 1.495 Saturn radii, has an irregular edge that does not appear as a simple superposition of low-wavenumber normal modes.

  18. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  19. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  20. Discrete Variational Optimal Control

    NASA Astrophysics Data System (ADS)

    Jiménez, Fernando; Kobilarov, Marin; Martín de Diego, David

    2013-06-01

    This paper develops numerical methods for optimal control of mechanical systems in the Lagrangian setting. It extends the theory of discrete mechanics to enable the solutions of optimal control problems through the discretization of variational principles. The key point is to solve the optimal control problem as a variational integrator of a specially constructed higher dimensional system. The developed framework applies to systems on tangent bundles, Lie groups, and underactuated and nonholonomic systems with symmetries, and can approximate either smooth or discontinuous control inputs. The resulting methods inherit the preservation properties of variational integrators and result in numerically robust and easily implementable algorithms. Several theoretical examples and a practical one, the control of an underwater vehicle, illustrate the application of the proposed approach.

  1. Discrete minimal flavor violation

    SciTech Connect

    Zwicky, Roman; Fischbacher, Thomas

    2009-10-01

    We investigate the consequences of replacing the global flavor symmetry of minimal flavor violation (MFV) SU(3){sub Q}xSU(3){sub U}xSU(3){sub D}x{center_dot}{center_dot}{center_dot} by a discrete D{sub Q}xD{sub U}xD{sub D}x{center_dot}{center_dot}{center_dot} symmetry. Goldstone bosons resulting from the breaking of the flavor symmetry generically lead to bounds on new flavor structure many orders of magnitude above the TeV scale. The absence of Goldstone bosons for discrete symmetries constitute the primary motivation of our work. Less symmetry implies further invariants and renders the mass-flavor basis transformation observable in principle and calls for a hierarchy in the Yukawa matrix expansion. We show, through the dimension of the representations, that the (discrete) symmetry in principle does allow for additional {delta}F=2 operators. If though the {delta}F=2 transitions are generated by two subsequent {delta}F=1 processes, as, for example, in the standard model, then the four crystal-like groups {sigma}(168){approx_equal}PSL(2,F{sub 7}), {sigma}(72{phi}), {sigma}(216{phi}) and especially {sigma}(360{phi}) do provide enough protection for a TeV-scale discrete MFV scenario. Models where this is not the case have to be investigated case by case. Interestingly {sigma}(216{phi}) has a (nonfaithful) representation corresponding to an A{sub 4} symmetry. Moreover we argue that the, apparently often omitted, (D) groups are subgroups of an appropriate {delta}(6g{sup 2}). We would like to stress that we do not provide an actual model that realizes the MFV scenario nor any other theory of flavor.

  2. The Discrete Wavelet Transform

    DTIC Science & Technology

    1991-06-01

    Split- Band Coding," Proc. ICASSP, May 1977, pp 191-195. 12. Vetterli, M. "A Theory of Multirate Filter Banks ," IEEE Trans. ASSP, 35, March 1987, pp 356...both special cases of a single filter bank structure, the discrete wavelet transform, the behavior of which is governed by one’s choice of filters . In...B-1 ,.iii FIGURES 1.1 A wavelet filter bank structure ..................................... 2 2.1 Diagram illustrating the dialation and

  3. Steerable Discrete Fourier Transform

    NASA Astrophysics Data System (ADS)

    Fracastoro, Giulia; Magli, Enrico

    2017-03-01

    Directional transforms have recently raised a lot of interest thanks to their numerous applications in signal compression and analysis. In this letter, we introduce a generalization of the discrete Fourier transform, called steerable DFT (SDFT). Since the DFT is used in numerous fields, it may be of interest in a wide range of applications. Moreover, we also show that the SDFT is highly related to other well-known transforms, such as the Fourier sine and cosine transforms and the Hilbert transforms.

  4. New dust belts of Uranus: one ring, two ring, red ring, blue ring.

    PubMed

    de Pater, Imke; Hammel, Heidi B; Gibbard, Seran G; Showalter, Mark R

    2006-04-07

    We compared near-infrared observations of the recently discovered outer rings of Uranus with Hubble Space Telescope results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced by impacts into the embedded moon Mab, which apparently orbits at a location where nongravitational perturbations favor the survival and spreading of submicron-sized dust. R/2003 U 2 more closely resembles Saturn's G ring, which is red, a typical color for dusty rings.

  5. Rings Through Atmosphere

    NASA Image and Video Library

    2010-05-26

    NASA Cassini spacecraft looks toward the limb of Saturn and, on the right of this image, views part of the rings through the planet atmosphere. Saturn atmosphere can distort the view of the rings from some angles.

  6. Wavy, Wiggly Ring

    NASA Image and Video Library

    2012-04-23

    The constant change in Saturn wavy, wiggly F ring is on display in this image obtained by NASA Cassini spacecraft. The image shows a view looking directly down onto the ring with the planet removed from the center.

  7. Saturn Rings in Infrared

    NASA Image and Video Library

    2006-10-11

    This mosaic of Saturn rings was acquired by NASA Cassini visual and infrared mapping spectrometer instrument on Sept. 15, 2006, while the spacecraft was in the shadow of the planet looking back towards the rings

  8. The Inner Rings

    NASA Image and Video Library

    2007-02-01

    The Cassini spacecraft looks toward the innermost region of Saturn rings, capturing from right to left the C and B rings. The dark, inner edge of the Cassini Division is just visible in the lower left corner

  9. A paradigm for discrete physics

    SciTech Connect

    Noyes, H.P.; McGoveran, D.; Etter, T.; Manthey, M.J.; Gefwert, C.

    1987-01-01

    An example is outlined for constructing a discrete physics using as a starting point the insight from quantum physics that events are discrete, indivisible and non-local. Initial postulates are finiteness, discreteness, finite computability, absolute nonuniqueness (i.e., homogeneity in the absence of specific cause) and additivity.

  10. Saturn's F-Ring

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This narrow-angle camera image of Saturn's F Ring was taken through the Clear filter while at a distance of 6.9 million km from Saturn on 8 November 1980. The brightness variations of this tightly-constrained ring shown here indicate that the ring is less uniform in makeup than the larger rings. JPL managed the Voyager Project for NASA's Office of Space Science

  11. Saturn's F-Ring

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This narrow-angle camera image of Saturn's F Ring was taken through the Clear filter while at a distance of 6.9 million km from Saturn on 8 November 1980. The brightness variations of this tightly-constrained ring shown here indicate that the ring is less uniform in makeup than the larger rings. JPL managed the Voyager Project for NASA's Office of Space Science

  12. Modules over hereditary rings

    SciTech Connect

    Tuganbaev, A A

    1998-04-30

    Let A be a hereditary Noetherian prime ring that is not right primitive. A complete description of {pi}-injective A-modules is obtained. Conditions under which the classical ring of quotients of A is a {pi}-projective A-module are determined. A criterion for a right hereditary right Noetherian prime ring to be serial is obtained.

  13. Rings Around Uranus

    ERIC Educational Resources Information Center

    Maran, Stephen P.

    1977-01-01

    Events leading up to the discovery of the rings of Uranus are described. The methods used and the logic behind the methods are explained. Data collected to prove the existence of the rings are outlined and theories concerning the presence of planetary rings are presented. (AJ)

  14. Rings Around Uranus

    ERIC Educational Resources Information Center

    Maran, Stephen P.

    1977-01-01

    Events leading up to the discovery of the rings of Uranus are described. The methods used and the logic behind the methods are explained. Data collected to prove the existence of the rings are outlined and theories concerning the presence of planetary rings are presented. (AJ)

  15. Eyeing the E Ring

    NASA Image and Video Library

    2009-12-24

    NASA Cassini spacecraft takes a look at Saturn diffuse E ring which is formed from icy material spewing out of the south pole of the moon Enceladus. The E ring is seen nearly edge-on from slightly above the northern side of Saturn ring plane.

  16. The Jumping Ring Experiment

    ERIC Educational Resources Information Center

    Baylie, M.; Ford, P. J.; Mathlin, G. P.; Palmer, C.

    2009-01-01

    The jumping ring experiment has become central to liquid nitrogen shows given as part of the outreach and open day activities carried out within the University of Bath. The basic principles of the experiment are described as well as the effect of changing the geometry of the rings and their metallurgical state. In general, aluminium rings are…

  17. The Jumping Ring Experiment

    ERIC Educational Resources Information Center

    Baylie, M.; Ford, P. J.; Mathlin, G. P.; Palmer, C.

    2009-01-01

    The jumping ring experiment has become central to liquid nitrogen shows given as part of the outreach and open day activities carried out within the University of Bath. The basic principles of the experiment are described as well as the effect of changing the geometry of the rings and their metallurgical state. In general, aluminium rings are…

  18. Dusty D Ring

    NASA Image and Video Library

    2014-02-24

    Saturn D ring is easy to overlook since it trapped between the brighter C ring and the planet itself. In this view from NASA Cassini spacecraft, all that can be seen of the D ring is the faint and narrow arc as it stretches from top right of the ima

  19. On certain Hecke rings

    PubMed Central

    Evens, Sam; Bressler, Paul

    1987-01-01

    We examine rings that embed into the smash product of the group algebra of the Weyl group with the field of meromorphic functions on the Cartan subalgebra and are generated by elements that satisfy braid relations. We prove that every such ring is isomorphic to either the Hecke algebra, the nil Hecke ring, or the group algebra of the Weyl group. PMID:16593804

  20. Soft normed rings.

    PubMed

    Uluçay, Vakkas; Şahin, Mehmet; Olgun, Necati

    2016-01-01

    Molodtsov introduced the concept of soft sets, which can be seen as a new mathematical tool for dealing with uncertainty. In this paper, we initiate the study of soft normed rings by soft set theory. The notions of soft normed rings, soft normed ideals, soft complete normed rings are introduced and also several related properties and examples are given.

  1. Mapping magnetoelastic response of terfenol-D ring structure

    NASA Astrophysics Data System (ADS)

    Youssef, George; Newacheck, Scott; Lopez, Mario

    2017-05-01

    The magneto-elastic response of a Terfenol-D (Tb.3Dy.7Fe1.92) ring has been experimentally investigated and analyzed. Ring structures give rise to complex behavior based on the interaction of the magnetic field with the material, which is further compounded with anisotropies associated with mechanical and magnetic properties. Discrete strain measurements were used to construct magnetostriction maps, which are used to elucidate the non-uniformity of the strain distribution due to geometrical factors and magnetic field interactions, namely, magnetic shielding and stable onion state in the ring structure.

  2. Discrete epidemic models.

    PubMed

    Brauer, Fred; Feng, Zhilan; Castillo-Chavez, Carlos

    2010-01-01

    The mathematical theory of single outbreak epidemic models really began with the work of Kermack and Mackendrick about decades ago. This gave a simple answer to the long-standing question of why epidemics woould appear suddenly and then disappear just as suddenly without having infected an entire population. Therefore it seemed natural to expect that theoreticians would immediately proceed to expand this mathematical framework both because the need to handle recurrent single infectious disease outbreaks has always been a priority for public health officials and because theoreticians often try to push the limits of exiting theories. However, the expansion of the theory via the inclusion of refined epidemiological classifications or through the incorporation of categories that are essential for the evaluation of intervention strategies, in the context of ongoing epidemic outbreaks, did not materialize. It was the global threat posed by SARS in that caused theoreticians to expand the Kermack-McKendrick single-outbreak framework. Most recently, efforts to connect theoretical work to data have exploded as attempts to deal with the threat of emergent and re-emergent diseases including the most recent H1N1 influenza pandemic, have marched to the forefront of our global priorities. Since data are collected and/or reported over discrete units of time, developing single outbreak models that fit collected data naturally is relevant. In this note, we introduce a discrete-epidemic framework and highlight, through our analyses, the similarities between single-outbreak comparable classical continuous-time epidemic models and the discrete-time models introduced in this note. The emphasis is on comparisons driven by expressions for the final epidemic size.

  3. Saturn's largest ring.

    PubMed

    Verbiscer, Anne J; Skrutskie, Michael F; Hamilton, Douglas P

    2009-10-22

    Most planetary rings in the Solar System lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. The best known exceptions are Jupiter's gossamer rings and Saturn's E ring, broad sheets of dust that extend outward until they fade from view at five to ten planetary radii. Source satellites continuously supply the dust, which is subsequently lost in collisions or by radial transport. Here we report that Saturn has an enormous ring associated with its outer moon Phoebe, extending from at least 128R(S) to 207R(S) (Saturn's radius R(S) is 60,330 km). The ring's vertical thickness of 40R(S) matches the range of vertical motion of Phoebe along its orbit. Dynamical considerations argue that these ring particles span the Saturnian system from the main rings to the edges of interplanetary space. The ring's normal optical depth of approximately 2 x 10(-8) is comparable to that of Jupiter's faintest gossamer ring, although its particle number density is several hundred times smaller. Repeated impacts on Phoebe, from both interplanetary and circumplanetary particle populations, probably keep the ring populated with material. Ring particles smaller than centimetres in size slowly migrate inward and many of them ultimately strike the dark leading face of Iapetus.

  4. Discrete BPS skyrmions

    NASA Astrophysics Data System (ADS)

    Agaoglou, M.; Charalampidis, E. G.; Ioannidou, T. A.; Kevrekidis, P. G.

    2017-09-01

    A discrete analogue of the extended Bogomolny-Prasad-Sommerfeld (BPS) Skyrme model that admits time-dependent solutions is presented. Using the spacing h of adjacent lattice nodes as a parameter, we identify the spatial profile of the solution and the continuation of the relevant branch of solutions over the lattice spacing for different values of the potential (free) parameter α . In particular, we explore the dynamics and stability of the obtained solutions, finding that, while they generally seem to be prone to instabilities, for suitable values of the lattice spacing and for sufficiently large values of α , they may be long-lived in direct numerical simulations.

  5. Discrete Dynamics Lab

    NASA Astrophysics Data System (ADS)

    Wuensche, Andrew

    DDLab is interactive graphics software for creating, visualizing, and analyzing many aspects of Cellular Automata, Random Boolean Networks, and Discrete Dynamical Networks in general and studying their behavior, both from the time-series perspective — space-time patterns, and from the state-space perspective — attractor basins. DDLab is relevant to research, applications, and education in the fields of complexity, self-organization, emergent phenomena, chaos, collision-based computing, neural networks, content addressable memory, genetic regulatory networks, dynamical encryption, generative art and music, and the study of the abstract mathematical/physical/dynamical phenomena in their own right.

  6. On the solar dust ring(s)

    NASA Astrophysics Data System (ADS)

    Mukai, T.

    Based on a mechanism to form the solar dust ring, it is proved that the observed peak in infrared F-corona cannot be explained by silicate type grains alone. Preliminary analysis on the recent infrared data of the F-corona by Maihara et al. (1984) has suggested that the ring particles have different physical properties compared with the dust grains, which produce the background F-corona.

  7. Planetary rings: Of doughnuts and shepherds

    NASA Astrophysics Data System (ADS)

    Katzoff, Judith A.

    Voyager 2's recent encounter with Uranus has brought about a renewed interest in the nature of planetary rings. It has been difficult to explain, for example, how such rings can remain narrow and discrete and not expand as a result of the dissipation of energy from collisions of particles within them. A paper in the May issue of Geophysical Research Letters offers an enthusiastic restatement of one view on this question, first proposed in 1981. Advocates of the “shepherd satellite” idea, however, are far from swayed.The new paper, by F. Curtis Michel of Rice University (Houston, Tex.), restates his idea that particles in rings may exhibit a “coherent, rolling-type motion” such that significant collisions do not occur. Michel suggests that the ring “particles” (probably better visualized as boulders) may be so densely packed that they may be treated as a fluid. In Michel's model, each individual particle would follow an inclined, elliptical orbit that would not intersect with any other such orbit. Together, the motions of all the particles would generate a toroidal surface (Figure 1). The absence of collisions would account for the apparent paucity of small particles in the rings of Uranus, Michel says.

  8. Oscillating pendulum decay by emission of vortex rings

    NASA Astrophysics Data System (ADS)

    Bolster, Diogo; Hershberger, Robert E.; Donnelly, Russell J.

    2010-04-01

    We have studied oscillation of a pendulum in water using spherical bobs. By measuring the loss in potential energy, we estimate the drag coefficient on the sphere and compare to data from liquid-helium experiments. The drag coefficients compare very favorably illustrating the true scaling behavior of this phenomenon. We also studied the decay of amplitude of the pendulum over time. As observed previously, at small amplitudes, the drag on the bob is given by the linear Stokes drag and the decay is exponential. For larger amplitudes, the pendulum bob sheds vortex rings as it reverses direction. The momentum imparted to these vortex rings results in an additional discrete drag on the bob. We present experiments and a theoretical estimate of this vortex-ring-induced drag. We analytically derive an estimate for a critical amplitude beyond which vortex ring shedding will occur as well as an estimate of the radius of the ring as a function of amplitude.

  9. A ring-source model for jet noise

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    1978-01-01

    A model consisting of two ring sources was developed to study the direct radiation of jet noise in terms of correlation, coherence, and phase and also to aid in solving the inverse radiation problem of determining the noise source in terms of far-field measurements. The rings consist of discrete sources which are either monopoles or quadrupoles with Gaussian profiles. Only adjacent sources, both within the rings and between rings, are correlated. Results show that from the far-field information can be used to determine when the sources are compact or noncompact with respect to the acoustic wavelength and to distinguish between the types of sources. In addition, from the inverse radiation approach, the center of mass, the location and separation distance of the ring, and the diameters can be recovered.

  10. The Structure of Saturn's F Ring

    NASA Astrophysics Data System (ADS)

    Murray, C. D.; Attree, N. O.; Cooper, N. J.; Williams, G. A.

    2012-04-01

    In stark contrast to the ordered regularity of the planet's main rings, Cassini images of Saturn's F ring show a diversity of structures on a variety of scales. The ring is located ~3000km beyond the edge of the A ring and Cassini ISS images reveal a core (radial width ~50km) with localised radial distortions (~50km), as well as occasional spiral strands that can extend to ~200km on either side. High-resolution images also show discrete structures on smaller scales (~10km) in addition to several types of clumps in or around the core and the strands. Despite this the F ring can still be modelled as a uniformly precessing, eccentric, inclined ring suggesting that it has sufficient mass for the effects of self-gravity or collisions to be important in maintaining this configuration. The perturbing effect of the nearby satellite Prometheus is now well understood (Murray et al., 2005) as is its role in producing clumps of material which then interact with the ring and strands (Beurle et al., 2010). The production of the largest strands is linked to collisions between the ring's core and the object S/2004 S 6 (Murray et al., 2008) although additional objects may be involved. Such collisions produce "jets" of material that subsequently undergo Keplerian shear to produce the spiral strands. Cassini images have now provided direct evidence for the existence of a population of small objects (radius <1km) colliding with the ring. The impact velocities are ~ 5 m/s implying a source of objects with orbits similar to that of the F ring; this is consistent with what might be expected for objects formed in the core and perturbed by Prometheus. It is now possible to understand the morphology and dynamic nature of the F ring as being due to the gravitational and collisional effects of a variety of nearby objects, ranging in size from Prometheus (mean radius ~40km) down to sub-km objects orbiting close to the core.

  11. Dust and Planetary Rings

    NASA Astrophysics Data System (ADS)

    Siddiqui, Muddassir

    ABSTRACT Space is not empty it has comic radiations (CMBR), dust etc. Cosmic dust is that type of dust which is composed of particles in space which vary from few molecules to 0.1micro metres in size. This type of dust is made up of heavier atoms born in the heart of stars and supernova. Mainly it contains dust grains and when these dust grains starts compacting then it turns to dense clouds, planetary ring dust and circumstellar dust. Dust grains are mainly silicate particles. Dust plays a major role in our solar system, for example in zodiacal light, Saturn's B ring spokes, planetary rings at Jovian planets and comets. Observations and measurements of cosmic dust in different regions of universe provide an important insight into the Universe's recycling processes. Astronomers consider dust in its most recycled state. Cosmic dust have radiative properties by which they can be detected. Cosmic dusts are classified as intergalactic dusts, interstellar dusts and planetary rings. A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in flat disc shape. All of the Jovian planets in our solar system have rings. But the most notable one is the Saturn's ring which is the brightest one. In March 2008 a report suggested that the Saturn's moon Rhea may have its own tenuous ring system. The ring swirling around Saturn consists of chunks of ice and dust. Most rings were thought to be unstable and to dissipate over course of tens or hundreds of millions of years but it now appears that Saturn's rings might be older than that. The dust particles in the ring collide with each other and are subjected to forces other than gravity of its own planet. Such collisions and extra forces tend to spread out the rings. Pluto is not known to have any ring system but some Astronomers believe that New Horizons probe might find a ring system when it visits in 2015.It is also predicted that Phobos, a moon of Mars will break up and form into a planetary ring

  12. Surge in the Ring

    NASA Image and Video Library

    2016-08-29

    An ethereal, glowing spot appears on Saturn's B ring in this view from NASA's Cassini spacecraft. There is nothing particular about that place in the rings that produces the glowing effect -- instead, it is an example of an "opposition surge" making that area on the rings appear extra bright. An opposition surge occurs when the Sun is directly behind the observer looking toward the rings. The particular geometry of this observation makes the point in the rings appear much, much brighter than would otherwise be expected. This view looks toward the sunlit side of the rings from about 28 degrees above the ring plane. The image was taken in visible light with the Cassini wide-angle camera on June 26, 2016. The view was acquired at a distance of approximately 940,000 miles (1.5 million kilometers) from the rings and at a Sun-ring-spacecraft, or phase, angle of 0 degrees. Image scale on the rings at center is 56 miles (90 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20496

  13. Traceable Ring Signature

    NASA Astrophysics Data System (ADS)

    Fujisaki, Eiichiro; Suzuki, Koutarou

    The ring signature allows a signer to leak secrets anonymously, without the risk of identity escrow. At the same time, the ring signature provides great flexibility: No group manager, no special setup, and the dynamics of group choice. The ring signature is, however, vulnerable to malicious or irresponsible signers in some applications, because of its anonymity. In this paper, we propose a traceable ring signature scheme. A traceable ring scheme is a ring signature except that it can restrict “excessive” anonymity. The traceable ring signature has a tag that consists of a list of ring members and an issue that refers to, for instance, a social affair or an election. A ring member can make any signed but anonymous opinion regarding the issue, but only once (per tag). If the member submits another signed opinion, possibly pretending to be another person who supports the first opinion, the identity of the member is immediately revealed. If the member submits the same opinion, for instance, voting “yes” regarding the same issue twice, everyone can see that these two are linked. The traceable ring signature can suit to many applications, such as an anonymous voting on a BBS. We formalize the security definitions for this primitive and show an efficient and simple construction in the random oracle model.

  14. Slowing of Vortex Rings

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell; Bolster, Diogo; Hershberger, Robert

    2008-11-01

    We have investigated the slowing of vortex rings in water which are created with very thin cores. We find that these rings propagate with no measurable change in diameter or core size. The drag appears to be the result of viscous forces on the core. A simple model for this drag describes experimental data in terms of a drag coefficient, which depends only on Reynolds number. Barenghi's group at Newcastle found that the translational velocity of a ring in an inviscid fluid perturbed by Kelvin waves decreases with increasing amplitude of Kelvin waves. This suggests that the velocity of vortex rings in a viscous fluid may well depend on the amplitude of Kelvin waves at the time of formation. Rings with substantial amplitude of Kelvin waves will be expected to move more slowly than rings with little or no Kelvin wave amplitude. We present experimental data confirming this suggestion.

  15. Ring Details on Display

    NASA Image and Video Library

    2016-11-07

    This view from NASA's Cassini spacecraft showcases some of the amazingly detailed structure of Saturn's rings. The rings are made up of many smaller ringlets that blur together when seen from a distance. But when imaged up close, the rings' structures display quite a bit of variation. Ring scientists are debating the nature of these features -- whether they have always appeared this way or if their appearance has evolved over time. This view looks toward the sunlit side of the rings from about 4 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Sept. 24, 2016. The view was acquired at a distance of approximately 283,000 miles (456,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 32 degrees. Image scale is 17 miles (27 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20506

  16. Integrable discrete PT symmetric model.

    PubMed

    Ablowitz, Mark J; Musslimani, Ziad H

    2014-09-01

    An exactly solvable discrete PT invariant nonlinear Schrödinger-like model is introduced. It is an integrable Hamiltonian system that exhibits a nontrivial nonlinear PT symmetry. A discrete one-soliton solution is constructed using a left-right Riemann-Hilbert formulation. It is shown that this pure soliton exhibits unique features such as power oscillations and singularity formation. The proposed model can be viewed as a discretization of a recently obtained integrable nonlocal nonlinear Schrödinger equation.

  17. Discrete spectrum of inflationary fluctuations

    SciTech Connect

    Hogan, Craig J.

    2004-10-15

    It is conjectured that inflation, taking account of quantum gravity, leads to a discrete spectrum of cosmological perturbations, instead of the continuous Gaussian spectrum predicted by standard field theory in an unquantized background. Heuristic models of discrete spectra are discussed, based on an inflaton mode with self-gravity, a lattice of amplitude states, an entangled ensemble of modes, and the holographic or covariant entropy bound. Estimates are given for the discreteness observable in cosmic background anisotropy, galaxy clustering, and gravitational wave backgrounds.

  18. Nonintegrable Schrodinger discrete breathers.

    PubMed

    Gómez-Gardeñes, J; Floría, L M; Peyrard, M; Bishop, A R

    2004-12-01

    In an extensive numerical investigation of nonintegrable translational motion of discrete breathers in nonlinear Schrödinger lattices, we have used a regularized Newton algorithm to continue these solutions from the limit of the integrable Ablowitz-Ladik lattice. These solutions are shown to be a superposition of a localized moving core and an excited extended state (background) to which the localized moving pulse is spatially asymptotic. The background is a linear combination of small amplitude nonlinear resonant plane waves and it plays an essential role in the energy balance governing the translational motion of the localized core. Perturbative collective variable theory predictions are critically analyzed in the light of the numerical results.

  19. Discrete bisoliton fiber laser

    PubMed Central

    Liu, X. M.; Han, X. X.; Yao, X. K.

    2016-01-01

    Dissipative solitons, which result from the intricate balance between dispersion and nonlinearity as well as gain and loss, are of the fundamental scientific interest and numerous important applications. Here, we report a fiber laser that generates bisoliton – two consecutive dissipative solitons that preserve a fixed separation between them. Deviations from this separation result in its restoration. It is also found that these bisolitons have multiple discrete equilibrium distances with the quantized separations, as is confirmed by the theoretical analysis and the experimental observations. The main feature of our laser is the anomalous dispersion that is increased by an order of magnitude in comparison to previous studies. Then the spectral filtering effect plays a significant role in pulse-shaping. The proposed laser has the potential applications in optical communications and high-resolution optics for coding and transmission of information in higher-level modulation formats. PMID:27767075

  20. Discrete anti-gravity

    NASA Astrophysics Data System (ADS)

    Noyes, H. Pierre; Starson, Scott

    1991-03-01

    Discrete physics, because it replaces time evolution generated by the energy operator with a global bit-string generator (program universe) and replaces fields with the relativistic Wheeler-Feynman action at a distance, allows the consistent formulation of the concept of signed gravitational charge for massive particles. The resulting prediction made by this version of the theory is that free anti-particles near the surface of the earth will fall up with the same acceleration that the corresponding particles fall down. So far as we can see, no current experimental information is in conflict with this prediction of our theory. The experiment crusis will be one of the anti-proton or anti-hydrogen experiments at CERN. Our prediction should be much easier to test than the small effects which those experiments are currently designed to detect or bound.

  1. Discrete bisoliton fiber laser

    NASA Astrophysics Data System (ADS)

    Liu, X. M.; Han, X. X.; Yao, X. K.

    2016-10-01

    Dissipative solitons, which result from the intricate balance between dispersion and nonlinearity as well as gain and loss, are of the fundamental scientific interest and numerous important applications. Here, we report a fiber laser that generates bisoliton – two consecutive dissipative solitons that preserve a fixed separation between them. Deviations from this separation result in its restoration. It is also found that these bisolitons have multiple discrete equilibrium distances with the quantized separations, as is confirmed by the theoretical analysis and the experimental observations. The main feature of our laser is the anomalous dispersion that is increased by an order of magnitude in comparison to previous studies. Then the spectral filtering effect plays a significant role in pulse-shaping. The proposed laser has the potential applications in optical communications and high-resolution optics for coding and transmission of information in higher-level modulation formats.

  2. Steerable Discrete Cosine Transform

    NASA Astrophysics Data System (ADS)

    Fracastoro, Giulia; Fosson, Sophie M.; Magli, Enrico

    2017-01-01

    In image compression, classical block-based separable transforms tend to be inefficient when image blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, namely a discrete cosine transform (DCT) that can be steered in any chosen direction. Such transform, called steerable DCT (SDCT), allows to rotate in a flexible way pairs of basis vectors, and enables precise matching of directionality in each image block, achieving improved coding efficiency. The optimal rotation angles for SDCT can be represented as solution of a suitable rate-distortion (RD) problem. We propose iterative methods to search such solution, and we develop a fully fledged image encoder to practically compare our techniques with other competing transforms. Analytical and numerical results prove that SDCT outperforms both DCT and state-of-the-art directional transforms.

  3. Steerable Discrete Cosine Transform.

    PubMed

    Fracastoro, Giulia; Fosson, Sophie M; Magli, Enrico

    2017-01-01

    In image compression, classical block-based separable transforms tend to be inefficient when image blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, namely, a discrete cosine transform (DCT) that can be steered in any chosen direction. Such transform, called steerable DCT (SDCT), allows to rotate in a flexible way pairs of basis vectors, and enables precise matching of directionality in each image block, achieving improved coding efficiency. The optimal rotation angles for SDCT can be represented as solution of a suitable rate-distortion (RD) problem. We propose iterative methods to search such solution, and we develop a fully fledged image encoder to practically compare our techniques with other competing transforms. Analytical and numerical results prove that SDCT outperforms both DCT and state-of-the-art directional transforms.

  4. Discrete anti-gravity

    SciTech Connect

    Noyes, H.P. ); Starson, S. )

    1991-03-01

    Discrete physics, because it replaces time evolution generated by the energy operator with a global bit-string generator (program universe) and replaces fields'' with the relativistic Wheeler-Feynman action at a distance,'' allows the consistent formulation of the concept of signed gravitational charge for massive particles. The resulting prediction made by this version of the theory is that free anti-particles near the surface of the earth will fall'' up with the same acceleration that the corresponding particles fall down. So far as we can see, no current experimental information is in conflict with this prediction of our theory. The experiment crusis will be one of the anti-proton or anti-hydrogen experiments at CERN. Our prediction should be much easier to test than the small effects which those experiments are currently designed to detect or bound. 23 refs.

  5. Discrete Pearson distributions

    SciTech Connect

    Bowman, K.O.; Shenton, L.R.; Kastenbaum, M.A.

    1991-11-01

    These distributions are generated by a first order recursive scheme which equates the ratio of successive probabilities to the ratio of two corresponding quadratics. The use of a linearized form of this model will produce equations in the unknowns matched by an appropriate set of moments (assumed to exist). Given the moments we may find valid solutions. These are two cases; (1) distributions defined on the non-negative integers (finite or infinite) and (2) distributions defined on negative integers as well. For (1), given the first four moments, it is possible to set this up as equations of finite or infinite degree in the probability of a zero occurrence, the sth component being a product of s ratios of linear forms in this probability in general. For (2) the equation for the zero probability is purely linear but may involve slowly converging series; here a particular case is the discrete normal. Regions of validity are being studied. 11 refs.

  6. Discrete Reliability Projection

    DTIC Science & Technology

    2014-12-01

    Defense, Handbook MIL - HDBK -189C, 2011 Hall, J. B., Methodology for Evaluating Reliability Growth Programs of Discrete Systems, Ph.D. thesis, University...pk,i ] · [ 1− (1− θ̆k) · ( N k · T )]k−m , (2.13) 5 2 Hall’s Model where m is the number of observed failure modes and d∗i estimates di (either based...Mode Failures FEF Ni d ∗ i 1 1 0.95 2 1 0.70 3 1 0.90 4 1 0.90 5 4 0.95 6 2 0.70 7 1 0.80 Using equations 2.1 and 2.2 we can calculate the failure

  7. Immigration and Prosecutorial Discretion.

    PubMed

    Apollonio, Dorie; Lochner, Todd; Heddens, Myriah

    Immigration has become an increasingly salient national issue in the US, and the Department of Justice recently increased federal efforts to prosecute immigration offenses. This shift, however, relies on the cooperation of US attorneys and their assistants. Traditionally federal prosecutors have enjoyed enormous discretion and have been responsive to local concerns. To consider how the centralized goal of immigration enforcement may have influenced federal prosecutors in regional offices, we review their prosecution of immigration offenses in California using over a decade's worth of data. Our findings suggest that although centralizing forces influence immigration prosecutions, individual US attorneys' offices retain distinct characteristics. Local factors influence federal prosecutors' behavior in different ways depending on the office. Contrary to expectations, unemployment rates did not affect prosecutors' willingness to pursue immigration offenses, nor did local popular opinion about illegal immigration.

  8. Discrete Minimal Surface Algebras

    NASA Astrophysics Data System (ADS)

    Arnlind, Joakim; Hoppe, Jens

    2010-05-01

    We consider discrete minimal surface algebras (DMSA) as generalized noncommutative analogues of minimal surfaces in higher dimensional spheres. These algebras appear naturally in membrane theory, where sequences of their representations are used as a regularization. After showing that the defining relations of the algebra are consistent, and that one can compute a basis of the enveloping algebra, we give several explicit examples of DMSAs in terms of subsets of sln (any semi-simple Lie algebra providing a trivial example by itself). A special class of DMSAs are Yang-Mills algebras. The representation graph is introduced to study representations of DMSAs of dimension d ≤ 4, and properties of representations are related to properties of graphs. The representation graph of a tensor product is (generically) the Cartesian product of the corresponding graphs. We provide explicit examples of irreducible representations and, for coinciding eigenvalues, classify all the unitary representations of the corresponding algebras.

  9. Immigration and Prosecutorial Discretion

    PubMed Central

    Apollonio, Dorie; Lochner, Todd; Heddens, Myriah

    2015-01-01

    Immigration has become an increasingly salient national issue in the US, and the Department of Justice recently increased federal efforts to prosecute immigration offenses. This shift, however, relies on the cooperation of US attorneys and their assistants. Traditionally federal prosecutors have enjoyed enormous discretion and have been responsive to local concerns. To consider how the centralized goal of immigration enforcement may have influenced federal prosecutors in regional offices, we review their prosecution of immigration offenses in California using over a decade's worth of data. Our findings suggest that although centralizing forces influence immigration prosecutions, individual US attorneys' offices retain distinct characteristics. Local factors influence federal prosecutors' behavior in different ways depending on the office. Contrary to expectations, unemployment rates did not affect prosecutors' willingness to pursue immigration offenses, nor did local popular opinion about illegal immigration. PMID:26146530

  10. Saturn's rings - an overview

    NASA Astrophysics Data System (ADS)

    Cuzzi, J. N.

    2005-08-01

    Saturn's rings embody in their diversity the entire spectrum of ring properties seen across the outer solar system, and remain unique in fundamental ways. The Voyager flybys revealed their complexity in 1980-1981, while groundbased and HST observations have provided important new insights since that time. Since July 2004, when it skimmed only tens of thousands of km over the unlit face of the rings - collecting unique remote and in-situ observations as it entered orbit - Cassini has been fulfilling the long-held dream of understanding Saturn's rings in depth. As of this meeting, if all continues as planned, seven orbits designed specifically with ring observations in mind will have been completed - each providing even better geometric opportunities than an entire Voyager flyby (to a spacecraft with far more powerful instruments than Voyager). Even these represent only a fraction of what the complete mission will tell us about the rings. This talk will review the key properties of the rings, highlight the themes and new insights emerging from recent studies, and serve as a context for new results presented at the meeting. The key properties include the relationship of the rings to their close-in and embedded moons; the composition of the rings and its spatial variation; and the complex radial and vertical structure of the rings, as related to local particle sizes and mass density. The main themes are that several evolutionary processes cause all these to vary - we think substantially - with time, and that the rings may be much younger than Saturn. To achieve our goal of understanding the origin of the rings, we must start from an in-depth characterization of their current state, and peer back through their extensive evolution. Cassini observations, and their theoretical analysis, will ultimately make this possible.

  11. Radioactive gold ring dermatitis

    SciTech Connect

    Miller, R.A.; Aldrich, J.E. )

    1990-08-01

    A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy.

  12. Thermodynamics of discrete quantum processes

    NASA Astrophysics Data System (ADS)

    Anders, Janet; Giovannetti, Vittorio

    2013-03-01

    We define thermodynamic configurations and identify two primitives of discrete quantum processes between configurations for which heat and work can be defined in a natural way. This allows us to uncover a general second law for any discrete trajectory that consists of a sequence of these primitives, linking both equilibrium and non-equilibrium configurations. Moreover, in the limit of a discrete trajectory that passes through an infinite number of configurations, i.e. in the reversible limit, we recover the saturation of the second law. Finally, we show that for a discrete Carnot cycle operating between four configurations one recovers Carnot's thermal efficiency.

  13. Tiny Mimas, Huge Rings

    NASA Image and Video Library

    2016-11-28

    Saturn's icy moon Mimas is dwarfed by the planet's enormous rings. Because Mimas (near lower left) appears tiny by comparison, it might seem that the rings would be far more massive, but this is not the case. Scientists think the rings are no more than a few times as massive as Mimas, or perhaps just a fraction of Mimas' mass. Cassini is expected to determine the mass of Saturn's rings to within just a few hundredths of Mimas' mass as the mission winds down by tracking radio signals from the spacecraft as it flies close to the rings. The rings, which are made of small, icy particles spread over a vast area, are extremely thin -- generally no thicker than the height of a house. Thus, despite their giant proportions, the rings contain a surprisingly small amount of material. Mimas is 246 miles (396 kilometers) wide. This view looks toward the sunlit side of the rings from about 6 degrees above the ring plane. The image was taken in red light with the Cassini spacecraft wide-angle camera on July 21, 2016. The view was obtained at a distance of approximately 564,000 miles (907,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 31 degrees. Image scale is 34 miles (54 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20509

  14. Faint D Ring

    NASA Image and Video Library

    2015-04-27

    Not all of Saturn's rings are created equal: here the C and D rings appear side-by-side, but the C ring, which occupies the bottom half of this image, clearly outshines its neighbor. The D ring appears fainter than the C ring because it is comprised of less material. However, even rings as thin as the D ring can pose hazards to spacecraft. Given the high speeds at which Cassini travels, impacts with particles just fractions of a millimeter in size have the potential to damage key spacecraft components and instruments. Nonetheless, near the end of Cassini's mission, navigators plan to thread the spacecraft's orbit through the narrow region between the D ring and the top of Saturn's atmosphere. This view looks toward the unilluminated side of the rings from about 12 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 11, 2015. The view was acquired at a distance of approximately 372,000 miles (599,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 133 degrees. Image scale is 2.2 miles (3.6 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/pia18313

  15. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  16. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  17. Saturn's E ring revisited

    NASA Astrophysics Data System (ADS)

    Feibelman, W. A.; Klinglesmith, D. A.

    1980-07-01

    Images of the E ring of Saturn obtained by the image processing of photographs of the 1966 edge-on presentation of the planet's ring plane are presented. Two methods of image enhancement were used: scanning with an image quantizer operated in the derivative mode to enhance contrast and computerized subtraction of a circularly symmetric image of the overexposed Saturn disk. Further photographic and CCD observation confirming the existence of the ring extending to twice the diameter of the A ring, which was not detected by the Pioneer 11 imaging photopolarimeter, is indicated.

  18. Jupiter Ring Halo

    NASA Image and Video Library

    1998-03-26

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age. Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal "halo" is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest being

  19. Viscosity in Saturn's rings

    NASA Technical Reports Server (NTRS)

    Lissauer, J. J.; Shu, F. H.; Cuzzi, J. N.

    1982-01-01

    The technique of estimating the viscosity in Saturn's rings from the damping rate of waves observed to be propagating within the rings is discussed. The wavetrains of attempts using spiral density waves as a diagnostic suffer significant complications that compromise the interpretations. A method that considers the damping of spiral bending waves was used to deduce a kinematic viscosity of 260 (+150, -100) sqcm/sec for the middle of the A ring where bending waves are excited by the 5:3 vertical resonance with Mimas. This value implies upper limits on the particle velocity dispersion and local ring thickness of 0.4 cm/sec and 30 m, respectively.

  20. Pattern Formation in Spatially Discrete Systems

    NASA Astrophysics Data System (ADS)

    Méndez, Vicenç; Fedotov, Sergei; Horsthemke, Werner

    The preceding chapters have dealt with the spatiotemporal behavior of spatially continuous systems. We now turn our attention to the dynamical behavior and stability properties of spatially discrete systems. A wide variety of phenomena in chemistry, biology, physics, and other fields involve the coupling between nonlinear, discrete units. Examples include arrays of Josephson junctions, chains of coupled diode resonators, coupled chemical or biochemical reactors, myelinated nerve fibers, neuronal networks, and patchy ecosystems. Such networks of coupled nonlinear units often combine dynamical and structural complexity [422]. Cells in living tissues, for example, are arranged in a variety of geometries. One-dimensional rings of cells were already considered by Turing [440]. Other types of lattices, such as open-ended linear arrays, tubes, rectangular and hexagonal arrays, and irregular arrangements in two or three dimensions are also found, see for example [5]. Cells interact with adjacent cells in various distinct ways. For example, signaling between cells may occur via diffusion through gap junctions [352, 230] or by membrane-bound proteins, juxtacrine signaling [339, 340, 471].

  1. Modified spiral wound retaining ring

    NASA Technical Reports Server (NTRS)

    Lawson, A. G. (Inventor)

    1980-01-01

    A spiral wound retaining ring with angled ends is described. The ring is crimped at the same angle as the ring ends to maintain a constant thickness dimension. The angling of the ends of the ring and crimp allow the ends to be positioned closer together while maintaining enough clearance to enable insertion and removal of the ring. By reducing the separation distance between the ends a stronger ring results since the double layer area of the ring is maximized.

  2. Discrete Mathematics and Its Applications

    ERIC Educational Resources Information Center

    Oxley, Alan

    2010-01-01

    The article gives ideas that lecturers of undergraduate Discrete Mathematics courses can use in order to make the subject more interesting for students and encourage them to undertake further studies in the subject. It is possible to teach Discrete Mathematics with little or no reference to computing. However, students are more likely to be…

  3. Discrete Mathematics and Its Applications

    ERIC Educational Resources Information Center

    Oxley, Alan

    2010-01-01

    The article gives ideas that lecturers of undergraduate Discrete Mathematics courses can use in order to make the subject more interesting for students and encourage them to undertake further studies in the subject. It is possible to teach Discrete Mathematics with little or no reference to computing. However, students are more likely to be…

  4. Inner B Ring Terminus

    NASA Image and Video Library

    2009-09-21

    This mosaic, part of a larger mosaic of images captured by NASA Cassini Orbiter just hours before exact equinox at Saturn, shows that the spiral corrugation in the planet’s inner rings continues right up to the inner B ring.

  5. Neptune's ring system.

    NASA Astrophysics Data System (ADS)

    Porco, C. C.; Nicholson, P. D.; Cuzzi, J. N.; Lissauer, J. J.; Esposito, L. W.

    The authors review the current state of knowledge regarding the structure, particle properties, kinematics, dynamics, origin, and evolution of the Neptune rings derived from Earth-based and Voyager data. Neptune has a diverse system of five continuous rings - 2 broad (Galle and Lassell) and 3 narrow (Adams, Le Verrier, and Arago) - plus a narrow discontinuous ring sharing the orbit of one of its ring-region satellites, Galatea. The outermost Adams ring contains the only arcs observed so far in Voyager images. The five arcs vary in angular extent from ≡1° to ≡10°, and exhibit internal azimuthal structure with typical spatial scales of ≡0.5°. All five lie within ≡40° of longitude. Dust is present throughout the Neptune system and measureable quantities of it were detected over Neptune's north pole. The Adams ring (including the arcs) and the Le Verrier ring contain a significant fraction of dust. The Neptune ring particles are probably red, and may consist of ice "dirtied" with silicates and/or some carbon-bearing material. A kinematic model for the arcs derived from Voyager data, the arcs' physical characteristics, and their orbital geometry and phasing are all roughly in accord with single-satellite arc shepherding by Galatea, though the presence of small kilometer-sized bodies embedded either within the arcs or placed at their Lagrange points may explain some inconsistencies with this model.

  6. EBT ring physics

    SciTech Connect

    Uckan, N.A.

    1980-04-01

    This workshop attempted to evaluate the status of the current experimental and theoretical understanding of hot electron ring properties. The dominant physical processes that influence ring formation, scaling, and their optimal behavior are also studied. Separate abstracts were prepared for each of the 27 included papers. (MOW)

  7. Uranus Ring System

    NASA Image and Video Library

    1996-01-29

    This image captured by NASA's Voyager 2 in 1986 revealed a continuous distribution of small particles throughout the Uranus ring system. This unique geometry, the highest phase angle at which Voyager imaged the rings, allowed us to see lanes of fine dust. http://photojournal.jpl.nasa.gov/catalog/PIA00142

  8. Smoke Ring Physics

    NASA Astrophysics Data System (ADS)

    Huggins, Elisha

    2011-11-01

    The behavior of smoke rings, tornados, and quantized vortex rings in superfluid helium has many features in common. These features can be described by the same mathematics we use when introducing Ampère's law in an introductory physics course. We discuss these common features.

  9. Smoke Ring Physics

    ERIC Educational Resources Information Center

    Huggins, Elisha

    2011-01-01

    The behavior of smoke rings, tornados, and quantized vortex rings in superfluid helium has many features in common. These features can be described by the same mathematics we use when introducing Ampere's law in an introductory physics course. We discuss these common features. (Contains 7 figures.)

  10. Steroidal contraceptive vaginal rings.

    PubMed

    Sarkar, N N

    2003-06-01

    The development of steroid-releasing vaginal rings over the past three decades is reviewed to illustrate the role of this device as an effective hormonal contraceptive for women. Vaginal rings are made of polysiloxane rubber or ethylene-vinyl-acetate copolymer with an outer diameter of 54-60 mm and a cross-sectional diameter of 4-9.5 mm and contain progestogen only or a combination of progestogen and oestrogen. The soft flexible combined ring is inserted in the vagina for three weeks and removed for seven days to allow withdrawal bleeding. Progesterone/progestogen-only rings are kept in for varying periods and replaced without a ring-free period. Rings are in various stages of research and development but a few, such as NuvaRing, have reached the market in some countries. Women find this method easy to use, effective, well tolerated and acceptable with no serious side-effects. Though the contraceptive efficacy of these vaginal rings is high, acceptability is yet to be established.

  11. Smoke Ring Physics

    ERIC Educational Resources Information Center

    Huggins, Elisha

    2011-01-01

    The behavior of smoke rings, tornados, and quantized vortex rings in superfluid helium has many features in common. These features can be described by the same mathematics we use when introducing Ampere's law in an introductory physics course. We discuss these common features. (Contains 7 figures.)

  12. The Fermilab recycler ring

    SciTech Connect

    Martin Hu

    2001-07-24

    The Fermilab Recycler is a permanent magnet storage ring for the accumulation of antiprotons from the Antiproton Source, and the recovery and cooling of the antiprotons remaining at the end of a Tevatron store. It is an integral part of the Fermilab III luminosity upgrade. The following paper describes the design features, operational and commissioning status of the Recycler Ring.

  13. Lower esophageal ring (Schatzki)

    MedlinePlus

    ... narrowed area to stretch the ring. Sometimes, a balloon is placed in the area and inflated, to help widen the ring. Outlook (Prognosis) Swallowing problems may return. You may need repeat treatment. When to Contact a Medical Professional Call your health care provider if you ...

  14. Contactless Magnetic Slip Ring

    NASA Technical Reports Server (NTRS)

    Kumagai, Hiroyuki (Inventor); Deardon, Joe D. (Inventor)

    1997-01-01

    A contactless magnetic slip ring is disclosed having a primary coil and a secondary coil. The primary and secondary coils are preferably magnetically coupled together, in a highly reliable efficient manner, by a magnetic layered core. One of the secondary and primary coils is rotatable and the contactless magnetic slip ring provides a substantially constant output.

  15. Rings of Neptune

    NASA Image and Video Library

    1999-07-25

    These two 591-second exposures of the rings of Neptune were taken with the clear filter by the NASA Voyager 2 wide-angle camera on Aug. 26, 1989. The two main rings are clearly visible and appear complete over the region imaged.

  16. Illustration of Saturn's Rings

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This illustration shows a close-up of Saturn's rings. These rings are thought to have formed from material that was unable to form into a Moon because of tidal forces from Saturn, or from a Moon that was broken up by Saturn's tidal forces.

  17. Birth Control Ring

    MedlinePlus

    ... It? The birth control ring is a soft, flexible, doughnut-shaped ring about 2 inches (5 centimeters) in diameter. It is inserted into the vagina, where it slowly releases hormones — the chemicals the body makes to control organ function — through the vaginal wall into the ...

  18. A-ring Propeller

    NASA Image and Video Library

    2010-08-26

    A propeller-shaped structure, created by an unseen moon, can be seen in Saturn A ring and looks like a small, dark line interrupting the bright surrounding ring material in the upper left of this image taken by NASA Cassini spacecraft.

  19. Telemetry carrier ring and support

    NASA Technical Reports Server (NTRS)

    Wakeman, Thomas G. (Inventor)

    1992-01-01

    A telemetry carrier ring for use in a gas turbine engine includes an annular support ring connected to the engine and an annular carrier ring coupled to the support ring, each ring exhibiting different growth characteristics in response to thermal and mechanical loading. The carrier ring is coupled to the support ring by a plurality of circumferentially spaced web members which are relatively thin in an engine radial direction to provide a predetermined degree of radial flexibility. the web members have a circumferential width and straight axial line of action selected to transfer torque and thrust between the support ring and the carrier ring without substantial deflection. The use of the web members with radial flexibility provides compensation between the support ring and the carrier ring since the carrier ring grows at a different rate than the supporting ring.

  20. Jupiter's Gossamer Rings Explained.

    NASA Astrophysics Data System (ADS)

    Hamilton, D. P.

    2003-05-01

    Over the past several years, Galileo measurements and groundbased imaging have drastically improved our knowledge of Jupiter's faint ring system. We now recognize that the ring consists of four components: a main ring 7000km wide, whose inner edge blossoms into a vertically-extended halo, and a pair of more tenuous Gossamer rings, one associated with each of the small moons Thebe and Amalthea. When viewed edge on, the Gossamer rings appear as diaphanous disks whose thicknesses agree with the vertical excursions of the inclined satellites from the equatorial plane. In addition, the brightness of each Gossamer ring drops off sharply outside the satellite orbits. These correlations allowed Burns etal (1999, Science, 284, 1146) to argue convincingly that the satellites act as sources of the dusty ring material. In addition, since most material is seen inside the orbits of the source satellites, an inwardly-acting dissipative force such as Poynting-Robertson drag is implicated. The most serious problem with this simple and elegant picture is that it is unable to explain the existence of a faint swath of material that extends half a jovian radius outward from Thebe. A key constraint is that this material has the same thickness as the rest of the Thebe ring. In this work, we identify the mechanism responsible for the outward extension: it is a shadow resonance, first investigated by Horanyi and Burns (1991, JGR, 96, 19283). When a dust grain enters Jupiter's shadow, photoelectric processes shut down and the grain's electric charge becomes more negative. The electromagnetic forces associated with the varying charge cause periodic oscillations in the orbital eccentricity and semimajor axis as the orbital pericenter precesses. This results in a ring which spreads both inward and outward of its source satellite while preserving its vertical thickness - just as is observed for the Thebe ring. Predictions of the model are: i) gaps of micron-sized material interior to Thebe and

  1. Jupiter's Rings: Sharpest View

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The New Horizons spacecraft took the best images of Jupiter's charcoal-black rings as it approached and then looked back at Jupiter. The top image was taken on approach, showing three well-defined lanes of gravel- to boulder-sized material composing the bulk of the rings, as well as lesser amounts of material between the rings. New Horizons snapped the lower image after it had passed Jupiter on February 28, 2007, and looked back in a direction toward the sun. The image is sharply focused, though it appears fuzzy due to the cloud of dust-sized particles enveloping the rings. The dust is brightly illuminated in the same way the dust on a dirty windshield lights up when you drive toward a 'low' sun. The narrow rings are confined in their orbits by small 'shepherding' moons.

  2. Jupiter Ring, With Orion

    NASA Image and Video Library

    2017-05-25

    As NASA's Juno spacecraft flew through the narrow gap between Jupiter's radiation belts and the planet during its first science flyby, Perijove 1, on August 27, 2016, the Stellar Reference Unit (SRU-1) star camera collected the first image of Jupiter's ring taken from the inside looking out. The bright bands in the center of the image are the main ring of Jupiter's ring system. While taking the ring image, the SRU was viewing the constellation Orion. The bright star above the main ring is Betelgeuse, and Orion's belt can be seen in the lower right. Juno's Radiation Monitoring Investigation actively retrieves and analyzes the noise signatures from penetrating radiation in the images of the spacecraft's star cameras and science instruments at Jupiter. https://photojournal.jpl.nasa.gov/catalog/PIA21644

  3. STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED ...

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

    STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED BY ARCHITECTURAL FINISH. TENSION RING ROLLER SUPPORT AT COLUMN OBSCURED BY COLUMN COVERINGS. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  4. Discreteness inducing coexistence

    NASA Astrophysics Data System (ADS)

    dos Santos, Renato Vieira

    2013-12-01

    Consider two species that diffuse through space. Consider further that they differ only in initial densities and, possibly, in diffusion constants. Otherwise they are identical. What happens if they compete with each other in the same environment? What is the influence of the discrete nature of the interactions on the final destination? And what are the influence of diffusion and additive fluctuations corresponding to random migration and immigration of individuals? This paper aims to answer these questions for a particular competition model that incorporates intra and interspecific competition between the species. Based on mean field theory, the model has a stationary state dependent on the initial density conditions. We investigate how this initial density dependence is affected by the presence of demographic multiplicative noise and additive noise in space and time. There are three main conclusions: (1) Additive noise favors denser populations at the expense of the less dense, ratifying the competitive exclusion principle. (2) Demographic noise, on the other hand, favors less dense populations at the expense of the denser ones, inducing equal densities at the quasi-stationary state, violating the aforementioned principle. (3) The slower species always suffers the more deleterious effects of statistical fluctuations in a homogeneous medium.

  5. Uranus - Discrete Cloud

    NASA Technical Reports Server (NTRS)

    1986-01-01

    This false-color Voyager picture of Uranus shows a discrete cloud seen as a bright streak near the planet's limb. The picture is a highly processed composite of three images obtained Jan. 14, 1986, when the spacecraft was 12.9 million kilometers (8.0 million miles) from the planet. The cloud visible here is the most prominent feature seen in a series of Voyager images designed to track atmospheric motions. (The occasional donut-shaped features, including one at the bottom, are shadows cast by dust in the camera optics; the processing necessary to bring out the faint features on the planet also brings out these camera blemishes.) Three separate images were shuttered through violet, blue and orange filters. Each color image showed the cloud to a different degree; because they were not exposed at exactly the same time, the images were processed to provide a correction for a good spatial match. In a true-color image, the cloud would be barely discernible; the false color helps bring out additional details. The different colors imply variations in vertical structure, but as yet is not possible to be specific about such differences. One possibility is that the Uranian atmosphere contains smog-like constituents, in which case some color differences may represent differences in how these molecules are distributed. The Voyager project is managed for NASA by the Jet Propulsion Laboratory.

  6. The Enceladus Ring

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] The Enceladus Ring (labeled)

    This excellent view of the faint E ring -- a ring feature now known to be created by Enceladus -- also shows two of Saturn's small moons that orbit within the ring, among a field of stars in the background.

    The E ring extends from three to eight Saturn radii -- about 180,000 kilometers (118,000 miles) to 482,000 kilometers (300,000 miles). Its full extent is not visible in this view.

    Calypso (22 kilometers, or 14 miles across) and Helene (32 kilometers, or 20 miles across) orbit within the E ring's expanse. Helene skirts the outer parts of the E ring, but here it is projected in front of a region deeper within the ring.

    Calypso and Helene are trojan satellites, or moons that orbit 60 degrees in front or behind a larger moon. Calypso is a Tethys trojan and Helene is a trojan of Dione.

    An interesting feature of note in this image is the double-banded appearance of the E-ring, which is created because the ring is somewhat fainter in the ringplane than it is 500-1,000 kilometers (300-600 miles) above and below the ringplane. This appearance implies that the particles in this part of the ring have nonzero inclinations (a similar affect is seen in Jupiter's gossamer ring). An object with a nonzero inclination does not orbit exactly at Saturn's ringplane. Instead, its orbit takes it above and below the ringplane. Scientists are not entirely sure why the particles should have such inclinations, but they are fairly certain that the reason involves Enceladus.

    One possible explanation is that all the E ring particles come from the plume of icy material that is shooting due south out of the moon's pole. This means all of the particles are created with a certain velocity out of the ringplane, and then they orbit above and below that plane.

    Another possible explanation is that Enceladus produces particles with a range of speeds, but the moon gravitationally

  7. The Enceladus Ring

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] The Enceladus Ring (labeled)

    This excellent view of the faint E ring -- a ring feature now known to be created by Enceladus -- also shows two of Saturn's small moons that orbit within the ring, among a field of stars in the background.

    The E ring extends from three to eight Saturn radii -- about 180,000 kilometers (118,000 miles) to 482,000 kilometers (300,000 miles). Its full extent is not visible in this view.

    Calypso (22 kilometers, or 14 miles across) and Helene (32 kilometers, or 20 miles across) orbit within the E ring's expanse. Helene skirts the outer parts of the E ring, but here it is projected in front of a region deeper within the ring.

    Calypso and Helene are trojan satellites, or moons that orbit 60 degrees in front or behind a larger moon. Calypso is a Tethys trojan and Helene is a trojan of Dione.

    An interesting feature of note in this image is the double-banded appearance of the E-ring, which is created because the ring is somewhat fainter in the ringplane than it is 500-1,000 kilometers (300-600 miles) above and below the ringplane. This appearance implies that the particles in this part of the ring have nonzero inclinations (a similar affect is seen in Jupiter's gossamer ring). An object with a nonzero inclination does not orbit exactly at Saturn's ringplane. Instead, its orbit takes it above and below the ringplane. Scientists are not entirely sure why the particles should have such inclinations, but they are fairly certain that the reason involves Enceladus.

    One possible explanation is that all the E ring particles come from the plume of icy material that is shooting due south out of the moon's pole. This means all of the particles are created with a certain velocity out of the ringplane, and then they orbit above and below that plane.

    Another possible explanation is that Enceladus produces particles with a range of speeds, but the moon gravitationally

  8. Earth: A Ringed Planet?

    NASA Astrophysics Data System (ADS)

    Hancock, L. O.; Povenmire, H.

    2010-12-01

    Among the most beautiful findings of the Space Age have been the discoveries of planetary rings. Not only Saturn but also Jupiter, Uranus and Neptune have rings; Saturn’s ring system has structures newly discovered; even Saturn's moon Rhea itself has a ring. All these are apparently supplied by material from the planetary moons (Rhea's ring by Rhea itself). The question naturally arises, why should the Earth not have a ring, and on the other hand, if it does, why has it not been observed? No rings have yet been observed in the inner solar system, but after all, rings in the inner solar system might simply tend to be fainter and more transient than those of the outer solar system: the inner solar system is more affected by the solar wind, and the Sun’s perturbing gravitational influence is greater. J.A. O’Keefe first suggested (1980) that Earth might have a ring system of its own. An Earth ring could account for some climate events. O’Keefe remarked that formation or thickening of a ring system in Earth’s equatorial plane could drive glaciation by deepening the chill of the winter hemisphere. (It is very well established that volcanic dust is an effective agent for the extinction of sunlight; this factor can be overwhelmingly apparent in eclipse observations.) O’Keefe died in 2000 and the speculation was not pursued, but the idea of an Earth ring has a prima facie reasonableness that calls for its renewed consideration. The program of this note is to hypothesize that, as O’Keefe proposed: (a) an Earth ring system exists; (b) it affects Earth's weather and climate; (c) the tektite strewn fields comprise filaments of the ring fallen to Earth's surface on various occasions of disturbance by comets or asteroids. On this basis, and drawing on the world's weather records, together with the Twentieth Century Reanalysis by NCEP/CIRES covering the period 1870-2010 and the geology of the tektite strewn fields, we herein propose the hypothesized Earth ring

  9. Quantized levitation states of superconducting multiple-ring systems

    SciTech Connect

    Haley, S.B.; Fink, H.J.

    1996-02-01

    The quantized levitation, trapped, and suspension states of a magnetic microsphere held in equilibrium by two fixed superconducting (SC) microrings are calculated by minimizing the free energy of the system. Each state is a discrete function of two independent fluxoid quantum numbers of the rings. When the radii of the SC rings are of the same order as the Ginzburg-Landau coherence length {xi}({ital T}), the system exhibits a small set of gravity and temperature-dependent levels. The levels of a weakly magnetized particle are sensitive functions of the gravitational field, indicating potential application as an accelerometer, and for trapping small magnetic particles in outer space or on Earth. The equilibrium states of a SC ring levitated by another SC ring are also calculated. {copyright} {ital 1996 The American Physical Society.}

  10. Hot piston ring tests

    NASA Technical Reports Server (NTRS)

    Allen, David J.; Tomazic, William A.

    1987-01-01

    As part of the DOE/NASA Automotive Stirling Engine Project, tests were made at NASA Lewis Research Center to determine whether appendix gap losses could be reduced and Stirling engine performance increased by installing an additional piston ring near the top of each piston dome. An MTI-designed upgraded Mod I Automotive Stirling Engine was used. Unlike the conventional rings at the bottom of the piston, these hot rings operated in a high temperature environment (700 C). They were made of a high temperature alloy (Stellite 6B) and a high temperature solid lubricant coating (NASA Lewis-developed PS-200) was applied to the cylinder walls. Engine tests were run at 5, 10, and 15 MPa operating pressure over a range of operating speeds. Tests were run both with hot rings and without to provide a baseline for comparison. Minimum data to assess the potential of both the hot rings and high temperature low friction coating was obtained. Results indicated a slight increase in power and efficiency, an increase over and above the friction loss introduced by the hot rings. Seal leakage measurements showed a significant reduction. Wear on both rings and coating was low.

  11. Seal ring installation tool

    NASA Technical Reports Server (NTRS)

    Haselmaier, L. Haynes (Inventor)

    2004-01-01

    A seal ring tool that allows an installer to position a primary seal ring between hub ends of pipe flanges that are being assembled together. The tool includes a pivoting handle member and extension arms attached to the pivoting handle member. The ends of the arms have side indentation type longitudinal grooves angled toward one another for holding the primary seal ring in place between the hubs of respective pipes that are to be attached together. The arms of the tool can also have flat sides that can be used to abut against an optional second larger seal that is supported within a groove in one of the hub ends so that the second hub end can then be moved against the other side of the primary seal ring. Once the seal ring is positioned between the pipe hubs, the pipe hubs can be moved about the seal ring due to the flat sides of the arms of the tool. The tool eliminates the chances of damaging and contaminating seal rings being installed within pipe hubs that are being attached to one another.

  12. Gored of the Rings

    NASA Image and Video Library

    2014-06-09

    Prometheus is caught in the act of creating gores and streamers in the F ring. Scientists believe that Prometheus and its partner-moon Pandora are responsible for much of the structure in the F ring as shown by NASA Cassini spacecraft. The orbit of Prometheus (53 miles, or 86 kilometers across) regularly brings it into the F ring. When this happens, it creates gores, or channels, in the ring where it entered. Prometheus then draws ring material with it as it exits the ring, leaving streamers in its wake. This process creates the pattern of structures seen in this image. This process is described in detail, along with a movie of Prometheus creating one of the streamer/channel features, in PIA08397. This view looks toward the sunlit side of the rings from about 8.6 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 11, 2014. The view was acquired at a distance of approximately 1.3 million miles (2.1 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 147 degrees. Image scale is 8 miles (13 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18270

  13. Dynamics of the Uranian Rings

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.

    1984-01-01

    Some of the problems of the shepherding satellite model of Goldreich ant tremaine are discussed. The following topics are studied: (1) optical depths of the all the observed narrow rings; (2) satellite and ring separation timescales; (3) ring edge sharpness; (4) shock formation in narrow rings; (5) the existence of small satellites near the Uranian rings; and (6) the apse and node alignments of the eccentric and inclined rings.

  14. Dynamics of the Uranian Rings

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.

    1984-01-01

    Some of the problems of the shepherding satellite model of Goldreich ant tremaine are discussed. The following topics are studied: (1) optical depths of the all the observed narrow rings; (2) satellite and ring separation timescales; (3) ring edge sharpness; (4) shock formation in narrow rings; (5) the existence of small satellites near the Uranian rings; and (6) the apse and node alignments of the eccentric and inclined rings.

  15. Dynamics of planetary rings

    NASA Astrophysics Data System (ADS)

    Araki, S.

    1991-02-01

    The modeling of the dynamics of particle collisions within planetary rings is discussed. Particles in the rings collide with one another because they have small random motions in addition to their orbital velocity. The orbital speed is roughly 10 km/s, while the random motions have an average speed of about a tenth of a millimeter per second. As a result, the particle collisions are very gentle. Numerical analysis and simulation of the ring dynamics, performed with the aid of a supercomputer, is outlined.

  16. Theodolite Ring Lights

    NASA Technical Reports Server (NTRS)

    Clark, David

    2006-01-01

    Theodolite ring lights have been invented to ease a difficulty encountered in the well-established optical-metrology practice of using highly reflective spherical tooling balls as position references. A theodolite ring light produces a more easily visible reflection and eliminates the need for an autocollimating device. A theodolite ring light is a very bright light source that is well centered on the optical axis of the instrument. It can be fabricated, easily and inexpensively, for use on a theodolite or telescope of any diameter.

  17. Heavy ion storage rings

    SciTech Connect

    Schuch, R.

    1987-01-01

    A brief overview of synchrotron storage rings for heavy ions, which are presently under construction in different accelerator laboratories is given. Ions ranging from protons up to uranium ions at MeV/nucleon energies will be injected into these rings using multiturn injection from the accelerators available or being built in these laboratories. After injection, it is planned to cool the phase space distribution of the ions by merging them with cold electron beams or laser beams, or by using stochastic cooling. Some atomic physics experiments planned for these rings are presented.

  18. Alternative parallel ring protocols

    NASA Technical Reports Server (NTRS)

    Mukkamala, R.; Foudriat, E. C.; Maly, Kurt J.; Kale, V.

    1990-01-01

    Communication protocols are know to influence the utilization and performance of communication network. The effect of two token ring protocols on a gigabit network with multiple ring structure is investigated. In the first protocol, a mode sends at most one message on receiving a token. In the second protocol, a mode sends all the waiting messages when a token is received. The behavior of these protocols is shown to be highly dependent on the number of rings as well as the load in the network.

  19. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025870 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  20. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025872 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  1. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025866 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  2. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025868 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  3. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025879 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  4. Parametric instability of spinning elastic rings excited by fluctuating space-fixed stiffnesses

    NASA Astrophysics Data System (ADS)

    Liu, Chunguang; Cooley, Christopher G.; Parker, Robert G.

    2017-07-01

    This study investigates the vibration of rotating elastic rings that are dynamically excited by an arbitrary number of space-fixed discrete stiffnesses with periodically fluctuating stiffnesses. The rotating, elastic ring is modeled using thin-ring theory with radial and tangential deformations. Primary and combination instability regions are determined in closed-form using the method of multiple scales. The ratio of peak-to-peak fluctuation to average discrete stiffness is used as the perturbation parameter, so the resulting perturbation analysis is not limited to small mean values of discrete stiffnesses. The natural frequencies and vibration modes are determined by discretizing the governing equations using Galerkin's method. Results are demonstrated for compliant gear applications. The perturbation results are validated by direct numerical integration of the equations of motion and Floquet theory. The bandwidths of the instability regions correlate with the fractional strain energy stored in the discrete stiffnesses. For rings with multiple discrete stiffnesses, the phase differences between them can eliminate large amplitude response under certain conditions.

  5. Ring-resonator-integrated tunable external cavity laser employing EAM and SOA.

    PubMed

    Yoon, Ki-Hong; Kwon, O-Kyun; Kim, Ki Soo; Choi, Byung-Seok; Oh, Su Hwan; Kim, Hyun Su; Sim, Jae-Sik; Kim, Chul Soo

    2011-12-05

    We propose and demonstrate a tunable external cavity laser (ECL) composed of a polymer Bragg reflector (PBR) and integrated gain chip with gain, a ring resonator, an electro-absorption modulator (EAM), and a semiconductor optical amplifier (SOA). The cavity of the laser is composed of the PBR, gain, and ring resonator. The ring resonator reflects the predetermined wavelengths into the gain region and transmits the output signal into integrated devices such as the EAM and SOA. The output wavelength of the tunable laser is discretely tuned in steps of about 0.8 nm through the thermal-optic effect of the PBR and predetermined mode spacing of the ring resonator.

  6. Scintillating C Ring

    NASA Image and Video Library

    2007-01-16

    Both luminous and translucent, the C ring sweeps out of the darkness of Saturn's shadow and obscures the planet at lower left. The ring is characterized by broad, isolated bright areas, or "plateaus," surrounded by fainter material. This view looks toward the unlit side of the rings from about 19 degrees above the ringplane. North on Saturn is up. The dark, inner B ring is seen at lower right. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Dec. 15, 2006 at a distance of approximately 632,000 kilometers (393,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 56 degrees. Image scale is 34 kilometers (21 miles) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA08855

  7. Ring of Stellar Fire

    NASA Image and Video Library

    2014-10-22

    This image from NASA Spitzer Space Telescope shows where the action is taking place in galaxy NGC 1291. The outer ring, colored red, is filled with new stars that are igniting and heating up dust that glows with infrared light.

  8. Obscured by Rings

    NASA Image and Video Library

    2012-08-29

    Saturn rings obscure part of Titan colorful visage in this image from NASA Cassini spacecraft. The south polar vortex that first appeared in Titan atmosphere in 2012 is visible at the bottom of this view.

  9. Outer B Ring Edge

    NASA Image and Video Library

    2004-12-03

    This image NASA Cassini spacecraft shows subtle, wavelike patterns, hundreds of narrow features resembling a record grooves in Saturn outer B-ring, and a noticeable abrupt change in overall brightness beyond the dark gap near the right.

  10. A-Ring Structures

    NASA Image and Video Library

    2010-09-23

    Several structures in Saturn A ring are exposed near the Encke Gap in this image captured by NASA Cassini spacecraft. A peculiar kink can be seen in one particularly bright ringlet at the bottom right.

  11. Ring Shadows on Janus

    NASA Image and Video Library

    2009-12-23

    Sunlight passing through the Cassini Division between Saturn A and B rings sweeps across and illuminates the surface of the moon Janus in this image captured by NASA Cassini spacecraft. Go to the Photojournal to view the animation.

  12. View of Saturn Rings

    NASA Image and Video Library

    1999-01-18

    This view shows some detail and differences in the complex system of rings. This was one of the first pictures obtained once NASA Voyager 2 resumed returning images Aug. 29, 1979 after its scan platform was commanded to view Saturn.

  13. Rings and Waves

    NASA Image and Video Library

    2013-09-30

    Saturn A ring is decorated with several kinds of waves. NASA Cassini spacecraft has captured a host of density waves, a bending wave, and the edge waves on the edge of the Keeler gap caused by the small moon Daphnis.

  14. Wisps Under the Rings

    NASA Image and Video Library

    2015-12-28

    Dione beautiful wispy terrain is brightly lit alongside Saturn elegant rings in this image captured by NASA Cassini spacecraft. The wisps are relatively young fractures on the trailing hemisphere of Dione icy surface.

  15. Warm core rings

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    Gulf stream phenomena have been the focus of numerous studies by U.S. and Canadian oceanographic laboratories. Two years ago, observations of warm core rings associated with the Gulf Stream were reported in The Oceanography Report, (November 2, 1982, p. 834). It was noted then that the structure of warm core rings can undergo rapid transformation. Recently, a multidisciplinary group of physical and biological oceanographic institutions has examined the evolution of warm core rings in detail [Nature, 308, pp. 837-840, 1984]. The study has involved research vessels Endeavor, Atlantis II, and Albatross IV for surface measurements of temperature, salinity, and for measurement surface pigments to assess the concentration of marine plants. The results are that even though warm core rings are often very stable, undergoing only slow changes, it turns out that major alterations in structure can and do occur in short periods of 2-5 days.

  16. Microscopic derivation of discrete hydrodynamics.

    PubMed

    Español, Pep; Anero, Jesús G; Zúñiga, Ignacio

    2009-12-28

    By using the standard theory of coarse graining based on Zwanzig's projection operator, we derive the dynamic equations for discrete hydrodynamic variables. These hydrodynamic variables are defined in terms of the Delaunay triangulation. The resulting microscopically derived equations can be understood, a posteriori, as a discretization on an arbitrary irregular grid of the Navier-Stokes equations. The microscopic derivation provides a set of discrete equations that exactly conserves mass, momentum, and energy and the dissipative part of the dynamics produces strict entropy increase. In addition, the microscopic derivation provides a practical implementation of thermal fluctuations in a way that the fluctuation-dissipation theorem is satisfied exactly. This paper points toward a close connection between coarse-graining procedures from microscopic dynamics and discretization schemes for partial differential equations.

  17. Chaos in Periodic Discrete Systems

    NASA Astrophysics Data System (ADS)

    Shi, Yuming; Zhang, Lijuan; Yu, Panpan; Huang, Qiuling

    This paper focuses on chaos in periodic discrete systems, whose state space may vary with time. Some close relationships between some chaotic dynamical behaviors of a periodic discrete system and its autonomous induced system are given. Based on these relationships, several criteria of chaos are established and some sufficient conditions for no chaos are given for periodic discrete systems. Further, it is shown that a finite-dimensional linear periodic discrete system is not chaotic in the sense of Li-Yorke or Wiggins. In particular, an interesting problem of whether nonchaotic rules may generate a chaotic system is studied, with some examples provided, one of which surprisingly shows that a composition of globally asymptotically stable maps can be chaotic. In addition, some properties of sign pattern matrices of non-negative square matrices are given for convenience of the study.

  18. Saturn's dynamic D ring

    USGS Publications Warehouse

    Hedman, M.M.; Burns, J.A.; Showalter, M.R.; Porco, C.C.; Nicholson, P.D.; Bosh, A.S.; Tiscareno, M.S.; Brown, R.H.; Buratti, B.J.; Baines, K.H.; Clark, R.

    2007-01-01

    The Cassini spacecraft has provided the first clear images of the D ring since the Voyager missions. These observations show that the structure of the D ring has undergone significant changes over the last 25 years. The brightest of the three ringlets seen in the Voyager images (named D72), has transformed from a narrow, <40-km wide ringlet to a much broader and more diffuse 250-km wide feature. In addition, its center of light has shifted inwards by over 200 km relative to other features in the D ring. Cassini also finds that the locations of other narrow features in the D ring and the structure of the diffuse material in the D ring differ from those measured by Voyager. Furthermore, Cassini has detected additional ringlets and structures in the D ring that were not observed by Voyager. These include a sheet of material just interior to the inner edge of the C ring that is only observable at phase angles below about 60??. New photometric and spectroscopic data from the ISS (Imaging Science Subsystem) and VIMS (Visual and Infrared Mapping Spectrometer) instruments onboard Cassini show the D ring contains a variety of different particle populations with typical particle sizes ranging from 1 to 100 microns. High-resolution images reveal fine-scale structures in the D ring that appear to be variable in time and/or longitude. Particularly interesting is a remarkably regular, periodic structure with a wavelength of ??? 30 ?? km extending between orbital radii of 73,200 and 74,000 km. A similar structure was previously observed in 1995 during the occultation of the star GSC5249-01240, at which time it had a wavelength of ??? 60 ?? km. We interpret this structure as a periodic vertical corrugation in the D ring produced by differential nodal regression of an initially inclined ring. We speculate that this structure may have formed in response to an impact with a comet or meteoroid in early 1984. ?? 2006 Elsevier Inc. All rights reserved.

  19. Ultrasonic Newton's rings

    SciTech Connect

    Hsu, D.K. ); Dayal, V. )

    1992-03-09

    Interference fringes due to bondline thickness variation were observed in ultrasonic scans of the reflected echo amplitude from the bondline of adhesively joined aluminum skins. To demonstrate that full-field interference patterns are observable in point-by-point ultrasonic scans, an optical setup for Newton's rings was scanned ultrasonically in a water immersion tank. The ultrasonic scan showed distinct Newton's rings whose radii were in excellent agreement with the prediction.

  20. Discrete solitons in graphene metamaterials

    NASA Astrophysics Data System (ADS)

    Bludov, Yu. V.; Smirnova, D. A.; Kivshar, Yu. S.; Peres, N. M. R.; Vasilevskiy, M. I.

    2015-01-01

    We study nonlinear properties of multilayer metamaterials created by graphene sheets separated by dielectric layers. We demonstrate that such structures can support localized nonlinear modes described by the discrete nonlinear Schrödinger equation and that its solutions are associated with stable discrete plasmon solitons. We also analyze the nonlinear surface modes in truncated graphene metamaterials being a nonlinear analog of surface Tamm states.

  1. Concurrency and discrete event control

    NASA Technical Reports Server (NTRS)

    Heymann, Michael

    1990-01-01

    Much of discrete event control theory has been developed within the framework of automata and formal languages. An alternative approach inspired by the theories of process-algebra as developed in the computer science literature is presented. The framework, which rests on a new formalism of concurrency, can adequately handle nondeterminism and can be used for analysis of a wide range of discrete event phenomena.

  2. Bending the Rings

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Saturn's rings appear strangely warped in this view of the rings seen through the upper Saturn atmosphere.

    The atmosphere acts like a lens in refracting (bending) the light reflected from the rings. As the rings pass behind the overexposed limb (edge) of Saturn as seen from Cassini, the ring structure appears to curve downward due to the bending of the light as it passes through the upper atmosphere.

    This image was obtained using a near-infrared filter. The filter samples a wavelength where methane gas does not absorb light, thus making the far-off rings visible through the upper atmosphere.

    By comparing this image to similar ones taken using filters where methane gas does absorb, scientists can estimate the vertical profile of haze and the abundance of methane in Saturn's high atmosphere.

    The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 14, 2005, through a filter sensitive to wavelengths of infrared light centered at 938 nanometers and at a distance of approximately 197,000 kilometers (123,000 miles) from Saturn. The image scale is 820 meters (2,680 feet) per pixel.

  3. Nardo Ring, Italy

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Nardo Ring is a striking visual feature from space, and astronauts have photographed it several times. The Ring is a race car test track; it is 12.5 kilometers long and steeply banked to reduce the amount of active steering needed by drivers. The Nardo Ring lies in a remote area on the heel of Italy's 'boot,' 50 kilometers east of the naval port of Taranto. The Ring encompasses a number of active (green) and fallow (brown to dark brown) agricultural fields. In this zone of intensive agriculture, farmers gain access to their fields through the Ring via a series of underpasses. Winding features within the southern section of the Ring appear to be smaller, unused race tracks.

    The image covers an area of 18.8 x 16.4 km, was acquired on August 17. 2007, and is located at 49.3 degrees north latitude, 17.8 degrees east longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  4. Barely Bisected Rings

    NASA Image and Video Library

    2016-09-12

    Saturn's shadow stretched beyond the edge of its rings for many years after Cassini first arrived at Saturn, casting an ever-lengthening shadow that reached its maximum extent at the planet's 2009 equinox. This image captured the moment in 2015 when the shrinking shadow just barely reached across the entire main ring system. The shadow will continue to shrink until the planet's northern summer solstice, at which point it will once again start lengthening across the rings, reaching across them in 2019. Like Earth, Saturn is tilted on its axis. And, just as on Earth, as the sun climbs higher in the sky, shadows get shorter. The projection of the planet's shadow onto the rings shrinks and grows over the course of its 29-year-long orbit, as the angle of the sun changes with respect to Saturn's equator. This view looks toward the sunlit side of the rings from about 11 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Jan. 16, 2015. The view was obtained at a distance of approximately 1.6 million miles (2.5 million kilometers) from Saturn. Image scale is about 90 miles (150 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20498

  5. Review of finite fields: Applications to discrete Fourier, transforms and Reed-Solomon coding

    NASA Technical Reports Server (NTRS)

    Wong, J. S. L.; Truong, T. K.; Benjauthrit, B.; Mulhall, B. D. L.; Reed, I. S.

    1977-01-01

    An attempt is made to provide a step-by-step approach to the subject of finite fields. Rigorous proofs and highly theoretical materials are avoided. The simple concepts of groups, rings, and fields are discussed and developed more or less heuristically. Examples are used liberally to illustrate the meaning of definitions and theories. Applications include discrete Fourier transforms and Reed-Solomon coding.

  6. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2014-04-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings [5, 8]. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~ 100m in size) have been identified in Saturn's A ring through their propeller signature in the images [10, 7, 9, 11]. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring [6, 2]. In this paper we present our new results about by now classical A ring propellers and more enigmatic B ring population. Due to the presence of self-gravity wakes the analysis of propeller brightness in ISS images always bears some ambiguity [7, 9] and consequently the exact morphology of propellers is not a settled issue. In 2008 we obtained a fortunate Cassini Ultraviolet Imaging Spectrograph (UVIS) occultation of the largest A ring propeller Bleriot. Utilizing Cassini ISS images we obtain Bleriot orbit and demonstrate that UVIS Persei Rev42 occultation did cut across Bleriot about 100km downstream from the center. The occultation itself shows a prominent partial gap and higher density outer flanking wakes, while their orientation is consistent with a downstream cut. While in the UVIS occultation the partial gap is more prominent than the flanking wakes, the features mostly seen in Bleriot images are actually flanking wakes. One of the most interesting aspects of the A ring propellers are their wanderings, or longitudinal deviations from a pure circular orbit [11]. We numerically investigated the possibility of simple moon

  7. Directed self-assembly of proteins into discrete radial patterns

    PubMed Central

    Thakur, Garima; Prashanthi, Kovur; Thundat, Thomas

    2013-01-01

    Unlike physical patterning of materials at nanometer scale, manipulating soft matter such as biomolecules into patterns is still in its infancy. Self-assembled monolayer (SAM) with surface density gradient has the capability to drive biomolecules in specific directions to create hierarchical and discrete structures. Here, we report on a two-step process of self-assembly of the human serum albumin (HSA) protein into discrete ring structures based on density gradient of SAM. The methodology involves first creating a 2-dimensional (2D) polyethylene glycol (PEG) islands with responsive carboxyl functionalities. Incubation of proteins on such pre-patterned surfaces results in direct self-assembly of protein molecules around PEG islands. Immobilization and adsorption of protein on such structures over time evolve into the self-assembled patterns. PMID:23719678

  8. Ring correlations in random networks

    NASA Astrophysics Data System (ADS)

    Sadjadi, Mahdi; Thorpe, M. F.

    2016-12-01

    We examine the correlations between rings in random network glasses in two dimensions as a function of their separation. Initially, we use the topological separation (measured by the number of intervening rings), but this leads to pseudo-long-range correlations due to a lack of topological charge neutrality in the shells surrounding a central ring. This effect is associated with the noncircular nature of the shells. It is, therefore, necessary to use the geometrical distance between ring centers. Hence we find a generalization of the Aboav-Weaire law out to larger distances, with the correlations between rings decaying away when two rings are more than about three rings apart.

  9. DC-Powered Jumping Ring

    NASA Astrophysics Data System (ADS)

    Jeffery, Rondo N.; Amiri, Farhang

    2016-02-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant differences from the AC case. In particular, the ring does not fly off the core but rises a short distance and then falls back. If the ring jumps high enough, the rising and the falling motion of the ring does not follow simple vertical motion of a projectile. This indicates that there are additional forces on the ring in each part of its motion. Four possible stages of the motion of the ring with DC are identified, which result from the ring current changing directions during the jump in response to a changing magnetic flux through the moving ring.

  10. Thermodynamic black di-rings

    SciTech Connect

    Iguchi, Hideo; Mishima, Takashi

    2010-10-15

    Previously the five dimensional S{sup 1}-rotating black rings have been superposed in a concentric way by some solitonic methods, and regular systems of two S{sup 1}-rotating black rings were constructed by the authors and then Evslin and Krishnan (we called these solutions 'black di-rings'). In this place we show some characteristics of the solutions of five dimensional black di-rings, especially in thermodynamic equilibrium. After the summary of the di-ring expressions and their physical quantities, first we comment on the equivalence of the two different solution sets of the black di-rings. Then the existence of thermodynamic black di-rings is shown, in which both isothermality and isorotation between the inner black ring and the outer black ring are realized. We also give detailed analysis of peculiar properties of the thermodynamic black di-ring including discussion about a certain kind of thermodynamic stability (instability) of the system.

  11. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2013-12-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~<500m in size) have been indirectly identified in Saturn's A ring through their propeller signature in the images. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring. In this paper we present evidence for the existence of propellers in Saturn's B ring by combining data from Cassini Ultraviolet Imaging Spectrograph (UVIS) and Imaging Science Subsystem (ISS) experiments. We show evidence that B ring seems to harbor two distinct populations of propellers: "big" propellers covering tens of degrees in azimuth situated in the densest part of B ring, and "small" propellers in less dense inner B ring that are similar in size and shape to known A ring propellers. The population of "big" propellers is exemplified with a single object which is observed for 5 years of Cassini data. The object is seen as a very elongated bright stripe (40 degrees wide) in unlit Cassini images, and dark stripe in lit geometries. In total we report observing the feature in images at 18 different epochs between 2005 and 2010. In UVIS occultations we observe this feature as an optical depth depletion in 14 out of 93 occultation cuts at corrotating longitudes compatible with imaging data. Combining the available Cassini data we infer that the object is a partial gap located at r=112,921km embedded in the high optical depth region of the B

  12. Stacked Corrugated Horn Rings

    NASA Technical Reports Server (NTRS)

    Sosnowski, John B.

    2010-01-01

    This Brief describes a method of machining and assembly when the depth of corrugations far exceeds the width and conventional machining is not practical. The horn is divided into easily machined, individual rings with shoulders to control the depth. In this specific instance, each of the corrugations is identical in profile, and only differs in diameter and outer profile. The horn is segmented into rings that are cut with an interference fit (zero clearance with all machining errors biased toward contact). The interference faces can be cut with a reverse taper to increase the holding strength of the joint. The taper is a compromise between the interference fit and the clearance of the two faces during assembly. Each internal ring is dipped in liquid nitrogen, then nested in the previous, larger ring. The ring is rotated in the nest until the temperature of the two parts equalizes and the pieces lock together. The resulting assay is stable, strong, and has an internal finish that cannot be achieved through other methods.

  13. Piston Ring Pressure Distribution

    NASA Technical Reports Server (NTRS)

    Kuhn, M.

    1943-01-01

    The discovery and introduction of the internal combustion engine has resulted in a very rapid development in machines utilizing the action of a piston. Design has been limited by the internal components of the engine, which has been subjected to ever increasing thermal and mechanical stresses, Of these internal engine components, the piston and piston rings are of particular importance and the momentary position of engine development is not seldom dependent upon the development of both of the components, The piston ring is a well-known component and has been used in its present shape in the steam engine of the last century, Corresponding to its importance, the piston ring has been a rich field for creative activity and it is noteworthy that in spite of this the ring has maintained its shape through the many years. From the many and complicated designs which have been suggested as a packing between piston and cylinder wall hardly one suggestion has remained which does not resemble the original design of cast iron rectangular ring.

  14. Two F Ring Views

    NASA Technical Reports Server (NTRS)

    2005-01-01

    These views, taken two hours apart, demonstrate the dramatic variability in the structure of Saturn's intriguing F ring.

    In the image at the left, ringlets in the F ring and Encke Gap display distinctive kinks, and there is a bright patch of material on the F ring's inner edge. Saturn's moon Janus (181 kilometers, or 113 miles across) is shown here, partly illuminated by reflected light from the planet.

    At the right, Prometheus (102 kilometers, or 63 miles across) orbits ahead of the radial striations in the F ring, called 'drapes' by scientists. The drapes appear to be caused by successive passes of Prometheus as it reaches the greatest distance (apoapse) in its orbit of Saturn. Also in this image, the outermost ringlet visible in the Encke Gap displays distinctive bright patches.

    These views were obtained from about three degrees below the ring plane.

    The images were taken in visible light with the Cassini spacecraft narrow-angle camera on June 29, 2005, when Cassini was about 1.5 million kilometers (900,000 miles) from Saturn. The image scale is about 9 kilometers (6 miles) per pixel.

  15. Ring solitons on vortices.

    PubMed

    Kevrekidis, P G; Nistazakis, H E; Frantzeskakis, D J; Malomed, B A; Bishop, A R

    2001-12-01

    Interaction of a ring dark or antidark soliton (RDS and RADS, respectively) with a vortex is considered in the defocusing nonlinear Schrödinger equation with cubic (for RDS) or saturable (for RADS) nonlinearities. By means of direct simulations, it is found that the interaction gives rise to either an almost isotropic or a spiral-like pattern. A transition between them occurs at a critical value of the RDS or RADS amplitude, the spiral pattern appearing if the amplitude exceeds the critical value. An initial ring soliton created on top of the vortex splits into a pair of rings moving inward and outward. In the subcritical case, the inbound ring reverses its polarity, bouncing from the vortex core, without conspicuous effect on the core. In the transcritical case, the bounced ring soliton suffers a spiral deformation, while the vortex changes its position and structure and also loses its axial symmetry. Through a variational-type approach to the system's Hamiltonian, we additionally find that the vortex-RDS and vortex-RADS interactions are, respectively, attractive and repulsive. Simulations with the vortex placed eccentrically with respect to the RDS or RADS reveal the generation of strongly localized multispot dark and/or antidark coherent structures. The occurrence of spiral-like patterns in many numerical experiments prompted an attempt to generate a spiral dark soliton, but the latter is found to suffer a core instability that converts it into a rotating dipole emitting waves in the outward direction.

  16. Distributed Relaxation for Conservative Discretizations

    NASA Technical Reports Server (NTRS)

    Diskin, Boris; Thomas, James L.

    2001-01-01

    A multigrid method is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work that is a small (less than 10) multiple of the operation count in one target-grid residual evaluation. The way to achieve this efficiency is the distributed relaxation approach. TME solvers employing distributed relaxation have already been demonstrated for nonconservative formulations of high-Reynolds-number viscous incompressible and subsonic compressible flow regimes. The purpose of this paper is to provide foundations for applications of distributed relaxation to conservative discretizations. A direct correspondence between the primitive variable interpolations for calculating fluxes in conservative finite-volume discretizations and stencils of the discretized derivatives in the nonconservative formulation has been established. Based on this correspondence, one can arrive at a conservative discretization which is very efficiently solved with a nonconservative relaxation scheme and this is demonstrated for conservative discretization of the quasi one-dimensional Euler equations. Formulations for both staggered and collocated grid arrangements are considered and extensions of the general procedure to multiple dimensions are discussed.

  17. Rings in the solar system

    SciTech Connect

    Pollack, J.B.; Cuzzi, J.N.

    1981-11-01

    Saturn, Jupiter, and Uranus have rings with different structure and composition. The rings consist of tiny masses in independent orbits. Photographs and data obtained by the Voyager project have aided in the understanding of Saturn's rings. Spokes have been found in B ring and boards, knots, and twist in F ring. Particles on the order of a micrometer in size are believed to occur in F, B, and A rings. The dominant component is water ice. The rings of Uranus are narrow and separated by broad empty regions. The technique used to study them has been stellar occulation. Nothing is known of particle size. The dominant component is believed to be silicates rich in compounds that absorb sunlight. Jupiter's rings consist of 3 main parts: a bright ring, a diffuse disk, and a halo. Use of Pioneer 10 data and other techniques have indicated particle sizes on the order of several micrometers and some at least a centimeter in diameter. The architecture of the ring system results from the interplay of a number of forces. These include gravitational forces due to moons outside the rings and moonlets embedded in them, electromagnetic forces due to the planet's rotating magnetic field, and even the gentle forces exerted by the dilute gaseous medium in which the rings rotate. Each of these forces is discussed. Several alternative explanations of how the rings arose are considered. The primary difference in these hypotheses is the account of the relationship between the ring particles of today and the primordial ring material. (SC)

  18. Physics of planetary rings

    NASA Astrophysics Data System (ADS)

    Gorkavyi, N.

    2007-08-01

    It is difficult to enumerate all the surprises presented by the planetary rings. The Saturnian rings are stratified into thousands of ringlets and the Uranian rings are compressed into narrow streams, which for some reason or other differ from circular orbits like the wheel of an old bicycle. The edge of the rings is jagged and the rings themselves are pegged down under the gravitational pressure of the satellites, bending like a ship's wake. There are spiral waves, elliptical rings, strange interlacing of narrow ringlets, and to cap it all one has observed in the Neptunian ring system three dense, bright arcs - like bunches of sausages on a transparent string. For celestial mechanics this is a spectacle as unnatural as a bear's tooth in the necklace of the English queen. In the dynamics of planetary rings the physics of collective interaction was supplemented by taking collisions between particles into account. One was led to study a kinetic equation with a rather complex collision integral - because the collisions are inelastic - which later on made it possible, both by using the Chapman-Enskog method and by using the solution of the kinetic equation for a plasma in a magnetic field, to reduce it to a closed set of (hydrodynamical) moment equations [1]. The hydrodynamical instabilities lead to the growth of short-wavelength waves and large-scale structures of the Saturnian rings [1]. We have shown that the formation of the existing dense Uranian rings is connected with the capture of positively drifting ring particles in inner Lindblad resonances which arrest this drift [1]. After the formation of dense rings at the positions of satellite resonances the collective interaction between resonant particles is amplified and the rings can leave the resonance and drift away from the planet and the parent resonance. We can expect in the C ring an appreciable positive ballistic particle drift caused by the erosion of the B ring by micrometeorites. It is therefore natural

  19. Stuck on the Rings

    NASA Image and Video Library

    2014-10-13

    Like a drop of dew hanging on a leaf, Tethys appears to be stuck to the A and F rings from this perspective. Tethys (660 miles, or 1,062 kilometers across), like the ring particles, is composed primarily of ice. The gap in the A ring through which Tethys is visible is the Keeler gap, which is kept clear by the small moon Daphnis (not visible here). This view looks toward the Saturn-facing hemisphere of Tethys. North on Tethys is up and rotated 43 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 14, 2014. The view was acquired at a distance of approximately 1.1 million miles (1.8 million kilometers) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 22 degrees. Image scale is 7 miles (11 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18284

  20. Ring-Bow

    NASA Image and Video Library

    2017-07-24

    Although the rings lack the many colors of the rainbow, they arc across the sky of Saturn. From equatorial locations on the planet, they'd appear very thin since they would be seen edge-on. Closer to the poles, the rings would appear much wider; in some locations (for parts of the Saturn's year), they would even block the sun for part of each day. This view looks toward the sunlit side of the rings from about 19 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on April 10, 2017. The view was obtained at a distance of approximately 680,000 miles (1.1 million kilometers) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 128 degrees. Image scale is 43 miles (69 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21339

  1. Deployable Fresnel Rings

    NASA Technical Reports Server (NTRS)

    Kennedy, Timothy F.; Fink, Patrick W.; Chu, Andrew W.; Lin, Gregory Y.

    2014-01-01

    Deployable Fresnel rings (DFRs) significantly enhance the realizable gain of an antenna. This innovation is intended to be used in combination with another antenna element, as the DFR itself acts as a focusing or microwave lens element for a primary antenna. This method is completely passive, and is also completely wireless in that it requires neither a cable, nor a connector from the antenna port of the primary antenna to the DFR. The technology improves upon the previous NASA technology called a Tri-Sector Deployable Array Antenna in at least three critical aspects. In contrast to the previous technology, this innovation requires no connector, cable, or other physical interface to the primary communication radio or sensor device. The achievable improvement in terms of antenna gain is significantly higher than has been achieved with the previous technology. Also, where previous embodiments of the Tri-Sector antenna have been constructed with combinations of conventional (e.g., printed circuit board) and conductive fabric materials, this innovation is realized using only conductive and non-conductive fabric (i.e., "e-textile") materials, with the possible exception of a spring-like deployment ring. Conceptually, a DFR operates by canceling the out-of-phase radiation at a plane by insertion of a conducting ring or rings of a specific size and distance from the source antenna, defined by Fresnel zones. Design of DFRs follow similar procedures to those outlined for conventional Fresnel zone rings. Gain enhancement using a single ring is verified experimentally and through computational simulation. The experimental test setup involves a microstrip patch antenna that is directly behind a single-ring DFR and is radiating towards a second microstrip patch antenna. The first patch antenna and DFR are shown. At 2.42 GHz, the DFR improves the transmit antenna gain by 8.6 dB, as shown in Figure 2, relative to the wireless link without the DFR. A figure illustrates the

  2. Rings dominate western Gulf

    NASA Astrophysics Data System (ADS)

    Vidal L., Francisco V.; Vidal L., Victor M. V.; Molero, José María Pérez

    Surface and deep circulation of the central and western Gulf of Mexico is controlled by interactions of rings of water pinched from the gulf's Loop Current. The discovery was made by Mexican oceanographers who are preparing a full-color, 8-volume oceanographic atlas of the gulf.Anticyclonic warm-core rings pinch off the Loop Current at a rate of about one to two per year, the scientists of the Grupo de Estudios Oceanográficos of the Instituto de Investigaciones Eléctricas (GEO-IIE) found. The rings migrate west until they collide with the continental shelf break of the western gulf, almost always between 22° and 23°N latitude. On their westward travel they transfer angular momentum and vorticity to the surrounding water, generating cyclonic circulations and vortex pairs that completely dominate the entire surface and deep circulation of the central and western gulf.

  3. Minisuperspace models of discrete systems

    NASA Astrophysics Data System (ADS)

    Baytaş, Bekir; Bojowald, Martin

    2017-04-01

    A discrete quantum spin system is presented in which several modern methods of canonical quantum gravity can be tested with promising results. In particular, features of interacting dynamics are analyzed with an emphasis on homogeneous configurations and the dynamical building-up and stability of long-range correlations. Different types of homogeneous minisuperspace models are introduced for the system, including one based on condensate states, and shown to capture different aspects of the discrete system. They are evaluated with effective methods and by means of continuum limits, showing good agreement with operator calculations whenever the latter are available. As a possibly quite general result, it is concluded that an analysis of the building-up of long-range correlations in discrete systems requires nonperturbative solutions of the dynamical equations. Some questions related to stability can be analyzed perturbatively but suggest that matter couplings may be relevant for this question in the context of quantum cosmology.

  4. Discretization errors in particle tracking

    NASA Astrophysics Data System (ADS)

    Carmon, G.; Mamman, N.; Feingold, M.

    2007-03-01

    High precision video tracking of microscopic particles is limited by systematic and random errors. Systematic errors are partly due to the discretization process both in position and in intensity. We study the behavior of such errors in a simple tracking algorithm designed for the case of symmetric particles. This symmetry algorithm uses interpolation to estimate the value of the intensity at arbitrary points in the image plane. We show that the discretization error is composed of two parts: (1) the error due to the discretization of the intensity, bD and (2) that due to interpolation, bI. While bD behaves asymptotically like N-1 where N is the number of intensity gray levels, bI is small when using cubic spline interpolation.

  5. Saturn's rings - high resolution

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Voyager 2 obtained this high-resolution picture of Saturn's rings Aug. 22, when the spacecraft was 4 million kilometers (2.5 million miles) away. Evident here are the numerous 'spoke' features, in the B-ring; their very sharp, narrow appearance suggests short formation times. Scientists think electromagnetic forces are responsible in some way for these features, but no detailed theory has been worked out. Pictures such as this and analyses of Voyager 2's spoke movies may reveal more clues about the origins of these complex structures. The Voyager project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.

  6. Unidirectional ring lasers

    DOEpatents

    Hohimer, J.P.; Craft, D.C.

    1994-09-20

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity is disclosed. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction. 21 figs.

  7. Unidirectional ring lasers

    DOEpatents

    Hohimer, John P.; Craft, David C.

    1994-01-01

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction.

  8. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  9. Satellite Rings Movie

    NASA Image and Video Library

    2000-12-30

    This brief movie clip (of which the release image is a still frame), taken by NASA's Cassini spacecraft as it approached Jupiter, shows the motions, over a 16 hour-period, of two satellites embedded in Jupiter's ring. The moon Adrastea is the fainter of the two, and Metis the brighter. Images such as these will be used to refine the orbits of the two bodies. The movie was made from images taken during a 40-hour sequence of the Jovian ring on December 11, 2000. http://photojournal.jpl.nasa.gov/catalog/PIA02872

  10. Ring laser gyroscope anode

    SciTech Connect

    Ljung, B.H.

    1981-03-17

    An anode for a ring laser gyroscope which provides improved current stability in the glow discharge path is disclosed. The anode of this invention permits operation at lower currents thereby allowing a reduction of heat dissipation in the ring laser gyroscope. The anode of one embodiment of this invention is characterized by a thumbtack appearance with a spherical end where the normal sharp end of the thumbtack would be located. The stem of the anode extends from the outside of the gyroscope structure to the interior of the structure such that the spherical end is substantially adjacent to the laser beam.

  11. Integrable structure in discrete shell membrane theory

    PubMed Central

    Schief, W. K.

    2014-01-01

    We present natural discrete analogues of two integrable classes of shell membranes. By construction, these discrete shell membranes are in equilibrium with respect to suitably chosen internal stresses and external forces. The integrability of the underlying equilibrium equations is proved by relating the geometry of the discrete shell membranes to discrete O surface theory. We establish connections with generalized barycentric coordinates and nine-point centres and identify a discrete version of the classical Gauss equation of surface theory. PMID:24808755

  12. Single ring vs multiple ring determination of Super Kamiokande

    NASA Astrophysics Data System (ADS)

    O'Malley, Patrick; Messier, Mark

    2004-10-01

    Super Kamiokande houses the world's largest Cherenkov detector and whose primary goal is to detect and study neutrino interactions. My purpose in the project was to write a program to enhance the accuracy the ring counting. Currently, ring counting is the largest single source of systematic uncertainty in the single ring event rate, contributing an uncertainty of 5-8This article presents an algorithm the single ring selection efficiency based on a statistical test of azimuthal symmetry of the event topology. With the aid of my advisor, Dr. Mark Messier, I was able to write a program that enhanced the decision between single-ring and multiple ring events by 35

  13. Saturn's Rings, the Yarkovsky Effects, and the Ring of Fire

    NASA Technical Reports Server (NTRS)

    Rubincam, David Parry

    2004-01-01

    The dimensions of Saturn's A and B rings may be determined by the seasonal Yarkovsky effect and the Yarkovsky-Schach effect; the two effects confine the rings between approximately 1.68 and approximately 2.23 Saturn radii, in reasonable agreement with the observed values of 1.525 and 2.267. The C ring may be sparsely populated because its particles are transients on their way to Saturn; the infall may create a luminous Ring of Fire around Saturn's equator. The ring system may be young: in the past heat flow from Saturn's interior much above its present value would not permit rings to exist.

  14. Synchrotron radiation masking in the PEP-II high-energy ring

    SciTech Connect

    Nordby, M.; Hodgson, J.; Fong, M.

    1994-06-01

    The high current, large bending radius, and high photon flux of the PEP-II high-energy ring dictate the use of both distributed and discrete synchrotron radiation (SR) absorbers. This combined masking design is presented, and thermal and structural analyses are discussed Analysis results show how the Oxygen-Free Electronic (OFE) copper chamber will reliably absorb the distributed radiation load, while high-strength Glidcop successfully withstands the higher thermal stresses of the discrete masks. Implications for fabrication are discussed.

  15. Stable discrete surface light bullets.

    PubMed

    Mihalache, Dumitru; Mazilu, Dumitru; Lederer, Falk; Kivshar, Yuri S

    2007-01-22

    We analyze spatiotemporal light localization near the edge of a semi-infinite array of weakly coupled nonlinear optical waveguides and demonstrate the existence of a novel class of continuous-discrete spatiotemporal solitons, the so-called discrete surface light bullets. We show that their properties are strongly affected by the presence of the surface. To this end the crossover between surface and quasi-bulk bullets is studied by analyzing the families of solitons propagating at different distances from the edge of the waveguide array.

  16. Discrete cloud structure on Neptune

    NASA Technical Reports Server (NTRS)

    Hammel, H. B.

    1989-01-01

    Recent CCD imaging data for the discrete cloud structure of Neptune shows that while cloud features at CH4-band wavelengths are manifest in the southern hemisphere, they have not been encountered in the northern hemisphere since 1986. A literature search has shown the reflected CH4-band light from the planet to have come from a single discrete feature at least twice in the last 10 years. Disk-integrated photometry derived from the imaging has demonstrated that a bright cloud feature was responsible for the observed 8900 A diurnal variation in 1986 and 1987.

  17. The elusive rings of Neptune

    NASA Astrophysics Data System (ADS)

    Porco, C. C.

    1992-04-01

    An overview of investigations of Neptune's rings is presented in which the recent data and findings from the Voyager 2 mission are emphasized. The evolving interpretation of the ring arcs is outlined, and the concept of resonance in the rings is described. Illustrations of the rings, the moons of Neptune, and the interactions between the two are given, and attention is given to the development of the rings by means of the catastrophic breakup of a planetary satellite. The very large crater on the Mimas satellite is given as evidence of potentially catastrophic impacts, and the implications of further breakup are discussed. A total of four rings are identified which include 3 pronounced rings and one ring that is more diaphanous. Clumps in the arcs are discussed in terms of the possible existence of large objects within the rings, and interparticle collisions are theorized to account for the large arc dust content.

  18. Interaction of multiple co-axial co-rotating vortex rings

    NASA Astrophysics Data System (ADS)

    Qin, Suyang; Liu, Hong; Liu, Xiaoyu; Xiang, Yang

    2015-11-01

    Fish and birds gain hydrodynamic force from a wake of discrete or linked vortex chain, which is the existence form of vortex rings in nature. Vortex rings with the same formation time are generated successively with different time interval by a piston-cylinder arrangement, and the velocity fields are measured using DPIV. The motion of multiple interacting vortex rings is first reported in laboratorial experiments. Besides the most attracting leapfrogging phenomenon, two other phenomena, suction and weak influence, are also clearly presented using the method of Lagrangian coherent structures. Due to the induced effect of wake vortex rings, the formation process of the forming vortex rings is different from that of a single isolated vortex ring, indicating that another distinct timescale exists, together with formation number proposed by Gharib (1998 JFM), determining the mechanisms of vortex rings. When the rear vortex ring leapfrogs, the limiting case is that the rear contracting ring is axis-touching. If an axis-touching ring is further squeezed by the wake vortex, the vortex structure will collapse, which can be explained by Kelvin-Benjamin variational principle. According to this principle, it is impossible for two optimal formed vortex rings to leapfrog. Financial support from the State Key Development Program of Basic Research of China (2014CB744802) is gratefully acknowledged.

  19. Making Molecular Borromean Rings

    ERIC Educational Resources Information Center

    Pentecost, Cari D.; Tangchaivang, Nichol; Cantrill, Stuart J.; Chichak, Kelly S.; Peters, Andrea J.; Stoddart, Fraser J.

    2007-01-01

    A procedure that requires seven 4-hour blocks of time to allow undergraduate students to prepare the molecular Borromean rings (BRs) on a gram-scale in 90% yield is described. The experiment would serve as a nice capstone project to culminate any comprehensive organic laboratory course and expose students to fundamental concepts, symmetry point…

  20. Exotic damping ring lattices

    SciTech Connect

    Palmer, R.B.

    1987-05-01

    This paper looks at, and compares three types of damping ring lattices: conventional, wiggler lattice with finite ..cap alpha.., wiggler lattice with ..cap alpha.. = 0, and observes the attainable equilibrium emittances for the three cases assuming a constraint on the attainable longitudinal impedance of 0.2 ohms. The emittance obtained are roughly in the ratio 4:2:1 for these cases.

  1. Reading, Writing, and Rings!

    ERIC Educational Resources Information Center

    Aschbacher, Pamela; Li, Erika; Hammon, Art

    2008-01-01

    "Reading, Writing, and Rings!" was created by a team of elementary teachers, literacy experts, and scientists in order to integrate science and literacy. These free units bring students inside NASA's Cassini-Huygens mission to Saturn. The authors--a science teacher and education outreach specialist and two evaluators of educational programs--have…

  2. Reading, Writing, and Rings!

    ERIC Educational Resources Information Center

    Aschbacher, Pamela; Li, Erika; Hammon, Art

    2008-01-01

    "Reading, Writing, and Rings!" was created by a team of elementary teachers, literacy experts, and scientists in order to integrate science and literacy. These free units bring students inside NASA's Cassini-Huygens mission to Saturn. The authors--a science teacher and education outreach specialist and two evaluators of educational programs--have…

  3. Making Molecular Borromean Rings

    ERIC Educational Resources Information Center

    Pentecost, Cari D.; Tangchaivang, Nichol; Cantrill, Stuart J.; Chichak, Kelly S.; Peters, Andrea J.; Stoddart, Fraser J.

    2007-01-01

    A procedure that requires seven 4-hour blocks of time to allow undergraduate students to prepare the molecular Borromean rings (BRs) on a gram-scale in 90% yield is described. The experiment would serve as a nice capstone project to culminate any comprehensive organic laboratory course and expose students to fundamental concepts, symmetry point…

  4. Ring of Stellar Death

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image from NASA's Spitzer Space Telescope shows a dying star (center) surrounded by a cloud of glowing gas and dust. Thanks to Spitzer's dust-piercing infrared eyes, the new image also highlights a never-before-seen feature -- a giant ring of material (red) slightly offset from the cloud's core. This clumpy ring consists of material that was expelled from the aging star.

    The star and its cloud halo constitute a 'planetary nebula' called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

    In this image, the expelled gases appear green, and the ring of expelled material appears red. Astronomers believe the ring is likely made of hydrogen molecules that were ejected from the star in the form of atoms, then cooled to make hydrogen pairs. The new data will help explain how planetary nebulas take shape, and how they nourish future generations of stars.

    This image composite was taken on Dec. 6, 2003, by Spitzer's infrared array camera, and is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

  5. Ring of Stellar Death

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image from NASA's Spitzer Space Telescope shows a dying star (center) surrounded by a cloud of glowing gas and dust. Thanks to Spitzer's dust-piercing infrared eyes, the new image also highlights a never-before-seen feature -- a giant ring of material (red) slightly offset from the cloud's core. This clumpy ring consists of material that was expelled from the aging star.

    The star and its cloud halo constitute a 'planetary nebula' called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

    In this image, the expelled gases appear green, and the ring of expelled material appears red. Astronomers believe the ring is likely made of hydrogen molecules that were ejected from the star in the form of atoms, then cooled to make hydrogen pairs. The new data will help explain how planetary nebulas take shape, and how they nourish future generations of stars.

    This image composite was taken on Dec. 6, 2003, by Spitzer's infrared array camera, and is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

  6. Crescent Moon with Rings

    NASA Image and Video Library

    2006-04-14

    This poetic scene shows the giant, smog-enshrouded moon Titan behind Saturn nearly edge-on rings. Much smaller Epimetheus 116 kilometers, or 72 miles across is just visible to the left of Titan 5,150 kilometers, or 3,200 miles across

  7. Epimetheus Above the Rings

    NASA Image and Video Library

    2015-11-09

    Although Epimetheus appears to be lurking above the rings here, it's actually just an illusion resulting from the viewing angle. In reality, Epimetheus and the rings both orbit in Saturn's equatorial plane. Inner moons and rings orbit very near the equatorial plane of each of the four giant planets in our solar system, but more distant moons can have orbits wildly out of the equatorial plane. It has been theorized that the highly inclined orbits of the outer, distant moons are remnants of the random directions from which they approached the planets they orbit. This view looks toward the unilluminated side of the rings from about -0.3 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 26, 2015. The view was obtained at a distance of approximately 500,000 miles (800,000 kilometers) from Epimetheus and at a Sun-Epimetheus-spacecraft, or phase, angle of 62 degrees. Image scale is 3 miles (5 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18342

  8. Rings In Between

    NASA Image and Video Library

    2011-12-05

    Saturn rings lie between a pair of moons in this view from NASA Cassini spacecraft that features Mimas and Prometheus. Mimas is the more noticeable of the two moons at top left, Prometheus is near the center of image and closest to Cassini.

  9. Ring laser scatterometer

    DOEpatents

    Ackermann, Mark; Diels, Jean-Claude

    2005-06-28

    A scatterometer utilizes the dead zone resulting from lockup caused by scatter from a sample located in the optical path of a ring laser at a location where counter-rotating pulses cross. The frequency of one pulse relative to the other is varied across the lockup dead zone.

  10. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  11. Rings from Close Encounters

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-09-01

    Weve recently discovered narrow sets of rings around two minor planets orbiting in our solar system. How did these rings form? A new study shows that they could be a result of close encounters between the minor planets and giants like Jupiter or Neptune.Unexpected Ring SystemsPositions of the centaurs in our solar system (green). Giant planets (red), Jupiter trojans (grey), scattered disk objects (tan) and Kuiper belt objects (blue) are also shown. [WilyD]Centaurs are minor planets in our solar system that orbit between Jupiter and Neptune. These bodies of which there are roughly 44,000 with diameters larger than 1 km have dynamically unstable orbits that cross paths with those of one or more giant planets.Recent occultation observations of two centaurs, 10199 Chariklo and 2060 Chiron, revealed that these bodies both host narrow ring systems. Besides our four giant planets, Chariklo and Chiron are the only other bodies in the solar system known to have rings. But how did these rings form?Scientists have proposed several models, implicating collisions, disruption of a primordial satellite, or dusty outgassing. But a team of scientists led by Ryuki Hyodo (Paris Institute of Earth Physics, Kobe University) has recently proposed an alternative scenario: what if the rings were formed from partial disruption of the centaur itself, after it crossed just a little too close to a giant planet?Tidal Forces from a GiantHyodo and collaborators first used past studies of centaur orbits to estimate that roughly 10% of centaurs experience close encounters (passing within a distance of ~2x the planetary radius) with a giant planet during their million-year lifetime. The team then performed a series of simulations of close encounters between a giant planet and a differentiated centaur a body in which the rocky material has sunk to form a dense silicate core, surrounded by an icy mantle.Some snapshots of simulation outcomes (click for a closer look!) for different initial states of

  12. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  13. Analytical and experimental studies of natural vibrations modes of ring-stiffened truncated-cone shells with variable theoretical ring fixity

    NASA Technical Reports Server (NTRS)

    Naumann, E. C.; Catherines, D. S.; Walton, W. C., Jr.

    1971-01-01

    Experimental and analytical investigations of the vibratory behavior of ring-stiffened truncated-cone shells are described. Vibration tests were conducted on 60 deg conical shells having up to four ring stiffeners and for free-free and clamped-free edge constraints and 9 deg conical shells, for two thicknesses, each with two angle rings and for free-free, free-clamped, and clamped-clamped edge constraints. The analytical method is based on linear thin shell theory, employing the Rayleigh-Ritz method. Discrete rings are represented as composed of one or more segments, each of which is a short truncated-cone shell of uniform thickness. Equations of constraint are used to join a ring and shell along a circumferential line connection. Excellent agreement was obtained for comparisons of experimental and calculated frequencies.

  14. Reduced discretization error in HZETRN

    SciTech Connect

    Slaba, Tony C.; Blattnig, Steve R.; Tweed, John

    2013-02-01

    The deterministic particle transport code HZETRN is an efficient analysis tool for studying the effects of space radiation on humans, electronics, and shielding materials. In a previous work, numerical methods in the code were reviewed, and new methods were developed that further improved efficiency and reduced overall discretization error. It was also shown that the remaining discretization error could be attributed to low energy light ions (A < 4) with residual ranges smaller than the physical step-size taken by the code. Accurately resolving the spectrum of low energy light particles is important in assessing risk associated with astronaut radiation exposure. In this work, modifications to the light particle transport formalism are presented that accurately resolve the spectrum of low energy light ion target fragments. The modified formalism is shown to significantly reduce overall discretization error and allows a physical approximation to be removed. For typical step-sizes and energy grids used in HZETRN, discretization errors for the revised light particle transport algorithms are shown to be less than 4% for aluminum and water shielding thicknesses as large as 100 g/cm{sup 2} exposed to both solar particle event and galactic cosmic ray environments.

  15. Police Discretion: A Selected Bibliography.

    ERIC Educational Resources Information Center

    Brenner, Robert N.; Kravitz, Marjorie

    This bibliography was compiled with two goals. The first goal is to provide police administrators and officers with an overview of the issues involved in developing guidelines for police discretion and a discussion of the options available. The second goal is to demonstrate the need for continuing dialogue and interaction between lawmakers, law…

  16. Reduced discretization error in HZETRN

    NASA Astrophysics Data System (ADS)

    Slaba, Tony C.; Blattnig, Steve R.; Tweed, John

    2013-02-01

    The deterministic particle transport code HZETRN is an efficient analysis tool for studying the effects of space radiation on humans, electronics, and shielding materials. In a previous work, numerical methods in the code were reviewed, and new methods were developed that further improved efficiency and reduced overall discretization error. It was also shown that the remaining discretization error could be attributed to low energy light ions (A < 4) with residual ranges smaller than the physical step-size taken by the code. Accurately resolving the spectrum of low energy light particles is important in assessing risk associated with astronaut radiation exposure. In this work, modifications to the light particle transport formalism are presented that accurately resolve the spectrum of low energy light ion target fragments. The modified formalism is shown to significantly reduce overall discretization error and allows a physical approximation to be removed. For typical step-sizes and energy grids used in HZETRN, discretization errors for the revised light particle transport algorithms are shown to be less than 4% for aluminum and water shielding thicknesses as large as 100 g/cm2 exposed to both solar particle event and galactic cosmic ray environments.

  17. Professional Discretion and Teacher Satisfaction.

    ERIC Educational Resources Information Center

    Sweeney, Jim

    1981-01-01

    Reports a survey of 1,295 teachers in large Iowa high schools on their needs (following Maslow's categories) in relation to age, sex, and student ability level taught, plus their overall job satisfaction and its relationship to their professional discretion, participation in decision making, and reciprocal trust. (Author/SJL)

  18. Discrete tomography in neutron radiography

    NASA Astrophysics Data System (ADS)

    Kuba, Attila; Rodek, Lajos; Kiss, Zoltán; Ruskó, László; Nagy, Antal; Balaskó, Márton

    2005-04-01

    Discrete tomography (DT) is an imaging technique for reconstructing discrete images from their projections using the knowledge that the object to be reconstructed contains only a few homogeneous materials characterized by known discrete absorption values. One of the main reasons for applying DT is that we will hopefully require relatively few projections. Using discreteness and some a priori information (such as an approximate shape of the object) we can apply two DT methods in neutron imaging by reducing the problem to an optimization task. The first method is a special one because it is only suitable if the object is composed of cylinders and sphere shapes. The second method is a general one in the sense that it can be used for reconstructing objects of any shape. Software was developed and physical experiments performed in order to investigate the effects of several reconstruction parameters: the number of projections, noise levels, and complexity of the object to be reconstructed. We give a summary of the experimental results and make a comparison of the results obtained using a classical reconstruction technique (FBP). The programs we developed are available in our DT reconstruction program package DIRECT.

  19. The gravitational interaction between inclined, elliptical rings. [Uranus rings

    NASA Technical Reports Server (NTRS)

    Yoder, C. F.

    1982-01-01

    An expression for the potential for two elliptical, inclined rings is derived from a model in which the gravitational torque between two wide rings or within a ring of finite width can prevent differential precession caused by planetary oblateness. The model was proposed to explain the observed eccentricity and width variations of the Uranian epsilon ring. The stationary solutions and stability of this system are examined.

  20. Discrete implementations of scale transform

    NASA Astrophysics Data System (ADS)

    Djurdjanovic, Dragan; Williams, William J.; Koh, Christopher K.

    1999-11-01

    Scale as a physical quantity is a recently developed concept. The scale transform can be viewed as a special case of the more general Mellin transform and its mathematical properties are very applicable in the analysis and interpretation of the signals subject to scale changes. A number of single-dimensional applications of scale concept have been made in speech analysis, processing of biological signals, machine vibration analysis and other areas. Recently, the scale transform was also applied in multi-dimensional signal processing and used for image filtering and denoising. Discrete implementation of the scale transform can be carried out using logarithmic sampling and the well-known fast Fourier transform. Nevertheless, in the case of the uniformly sampled signals, this implementation involves resampling. An algorithm not involving resampling of the uniformly sampled signals has been derived too. In this paper, a modification of the later algorithm for discrete implementation of the direct scale transform is presented. In addition, similar concept was used to improve a recently introduced discrete implementation of the inverse scale transform. Estimation of the absolute discretization errors showed that the modified algorithms have a desirable property of yielding a smaller region of possible error magnitudes. Experimental results are obtained using artificial signals as well as signals evoked from the temporomandibular joint. In addition, discrete implementations for the separable two-dimensional direct and inverse scale transforms are derived. Experiments with image restoration and scaling through two-dimensional scale domain using the novel implementation of the separable two-dimensional scale transform pair are presented.

  1. Discrete space charge affected field emission: Flat and hemisphere emitters

    SciTech Connect

    Jensen, Kevin L.; Shiffler, Donald A.; Tang, Wilkin; Rittersdorf, Ian M.; Lebowitz, Joel L.; Harris, John R.; Lau, Y. Y.; Petillo, John J.; Luginsland, John W.

    2015-05-21

    Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models proposed here treat the meso-scale diode region separate from the micro-scale regions characteristic of the emission sites. The consequences of discrete emission events are given for both one-dimensional (sheets of charge) and three dimensional (rings of charge) models: in the former, results converge to steady state conditions found by theory (e.g., Rokhlenko et al. [J. Appl. Phys. 107, 014904 (2010)]) but show oscillatory structure as they do. Surface roughness or geometric features are handled using a ring of charge model, from which the image charges are found and used to modify the apex field and emitted current. The roughness model is shown to have additional constraints related to the discrete nature of electron charge. The ability of a unit cell model to treat field emitter structures and incorporate surface roughness effects inside a beam optics code is assessed.

  2. Oscillations at B Ring Edge

    NASA Image and Video Library

    2010-11-01

    This image obtained by NASA Cassini spacecraft of the outer edge of Saturn?s B ring, reveals the combined effects of a tugging moon and oscillations that can naturally occur in disks like Saturn rings and spiral galaxies.

  3. Inorganic glass ceramic slip rings

    NASA Technical Reports Server (NTRS)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  4. Ring autosomes: some unexpected findings.

    PubMed

    Caba, L; Rusu, C; Plăiaşu; Gug, G; Grămescu, M; Bujoran, C; Ochiană, D; Voloşciuc, M; Popescu, R; Braha, E; Pânzaru, M; Butnariu, L; Sireteanu, A; Covic, M; Gorduza, Ev

    2012-12-01

    Ring chromosomes are rare entities, usually associated with phenotypic abnormalities in correlation with the loss of genetic material. There are various breakpoints and sometimes there is a dynamic mosaicism that is reflected in clinical features. Most of the ring chromosomes are de novo occurrences. Our study reflects the experience of three Romanian cytogenetic laboratories in the field of ring chromosomes. We present six cases with ring chromosomes involving chromosomes 5, 13, 18, and 21. All ring chromosomes were identified after birth in children with plurimalformative syndromes. The ring chromosome was present in mosaic form in three cases, and this feature reflects the ring's instability. In case of ring chromosome 5, we report a possible association with oculo-auriculo-vertebral spectrum.

  5. Planetary rings: Structure and history

    NASA Astrophysics Data System (ADS)

    Esposito, L.

    The composition and structure of planetary rings provide the key evidence to understand their origin and evolution. Before the first space observations, we were able to maintain an idealized view of the rings around Saturn, the only known ring system at that time. Rings were then discovered around Jupiter, Uranus and Neptune. Saturn's F ring was discovered by Pioneer 11. Our ideal view of circular, planar, symmetric and unchanging rings was shattered by observations of inclined, eccentric rings, waves and wavy edges, and numerous processes acting at rates that give timescales much younger than the solar system. Moons within and near the rings sculpt them and are the likely progenitors of future rings. The moonlet lifetimes are much less than Saturn's age. The old idea of ancient rings gave rise to youthful rings, that are recently created by erosion and destruction of small nearby moons. Although this explanation may work well for most rings, Saturn's massive ring system provides a problem. It is extremely improbable that Saturn's rings were recently created by the destruction of a moon as large as Mimas, or even by the breakup of a large comet that passed too close to Saturn. The history of Saturn's rings has been a difficult problem, now made even more challenging by the close-up Cassini measurements. Cassini observations show unexpected ring variability in time and space. Time variations are seen in ring edges, in the thinner D and F rings, and in the neutral oxygen cloud, which outweighs the E ring in the same region around Saturn. The rings are inhomogeneous, with structures on all scales, sharp gradients and edges. Compositional gradients are sharper than expected, but nonetheless cross structural boundaries. This is evidence for ballistic transport that has not gone to completion. The autocovariance maximizes in the middle of the A ring, with smaller structure near the main rings' outer edge. Density wave locations have a fresher ice composition. The

  6. Discrete gauge symmetries in discrete MSSM-like orientifolds

    NASA Astrophysics Data System (ADS)

    Ibáñez, L. E.; Schellekens, A. N.; Uranga, A. M.

    2012-12-01

    Motivated by the necessity of discrete ZN symmetries in the MSSM to insure baryon stability, we study the origin of discrete gauge symmetries from open string sector U(1)'s in orientifolds based on rational conformal field theory. By means of an explicit construction, we find an integral basis for the couplings of axions and U(1) factors for all simple current MIPFs and orientifolds of all 168 Gepner models, a total of 32 990 distinct cases. We discuss how the presence of discrete symmetries surviving as a subgroup of broken U(1)'s can be derived using this basis. We apply this procedure to models with MSSM chiral spectrum, concretely to all known U(3)×U(2)×U(1)×U(1) and U(3)×Sp(2)×U(1)×U(1) configurations with chiral bi-fundamentals, but no chiral tensors, as well as some SU(5) GUT models. We find examples of models with Z2 (R-parity) and Z3 symmetries that forbid certain B and/or L violating MSSM couplings. Their presence is however relatively rare, at the level of a few percent of all cases.

  7. RINGED ACCRETION DISKS: EQUILIBRIUM CONFIGURATIONS

    SciTech Connect

    Pugliese, D.; Stuchlík, Z. E-mail: zdenek.stuchlik@physics.cz

    2015-12-15

    We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

  8. Uranus Rings and Two Moons

    NASA Image and Video Library

    1999-06-19

    Voyager 2 has discovered two hepherd satellites associated with the rings of Uranus. The two moons, designated 1986U7 and 1986U8, are seen here on either side of the bright epsilon ring; all nine of the known Uranian rings are visible.

  9. Uranus: the rings are black.

    PubMed

    Sinton, W M

    1977-11-04

    An upper limit of 0.05 is established for the geometric albedo of the newly discovered rings of Uranus. In view of this very low albedo, the particles of the rings cannot be ice-covered as are those of rings A and B of Saturn.

  10. Ring closure in actin polymers

    NASA Astrophysics Data System (ADS)

    Sinha, Supurna; Chattopadhyay, Sebanti

    2017-03-01

    We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers.

  11. DC-Powered Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  12. DC-Powered Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  13. Investigations of planetary ring phenomena

    NASA Technical Reports Server (NTRS)

    Burns, Joseph A.

    1987-01-01

    Faint planetary rings, their dynamical behavior and physical properties, were the main focus of the research efforts. The motion of weakly-charged dust through the gravitational and magnetic fields of Jupiter were examined. Several topics concerning features of Saturn's rings were addressed. The origin and fate of the Uranian ring dust is presently being studied.

  14. Mimas Against the Rings

    NASA Image and Video Library

    2005-08-05

    During its close flyby of Saturn's moon Mimas on Aug. 2, 2005, Cassini caught a glimpse of Mimas against the broad expanse of Saturn's rings. The Keeler Gap in the outer A ring, in which Cassini spied a never-before-seen small moon (see PIA06237), is at the upper right. The ancient, almost asteroid-like surface of Mimas is evident in its crater-upon-crater appearance. Even the material which has slumped down into the bottom of some of its craters bears the marks of later impacts. This image was taken through the clear filter of the Cassini spacecraft narrow-angle camera at a distance of 68,000 kilometers (42,500 miles) from Mimas and very near closest approach. The smallest features seen on the moon are about 400 meters wide (440 yards); the Sun-Mimas-Cassini angle is 44 degrees. http://photojournal.jpl.nasa.gov/catalog/PIA06412

  15. Saturn Ring Observer

    NASA Technical Reports Server (NTRS)

    Spilker, T. R.

    2001-01-01

    Answering fundamental questions about ring particle characteristics, and individual and group behavior, appears to require close-proximity (a few km) observations. Saturn's magnificent example of a ring system offers a full range of particle sizes, densities, and behaviors for study, so it is a natural choice for such detailed investigation. Missions implementing these observations require post-approach Delta(V) of approximately 10 km/s or more, so past mission concepts called upon Nuclear Electric Propulsion. The concept described here reduces the propulsive Delta(V) requirement to as little as 3.5 km/s, difficult but not impossible for high-performance chemical propulsion systems. Additional information is contained in the original extended abstract.

  16. Satellite Rings Movie

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This brief movie clip (of which the release image is a still frame), taken by NASA's Cassini spacecraft as it approached Jupiter, shows the motions, over a 16 hour-period, of two satellites embedded in Jupiter's ring. The moon Adrastea is the fainter of the two, and Metis the brighter. Images such as these will be used to refine the orbits of the two bodies.

    The movie was made from images taken during a 40-hour sequence of the Jovian ring on December 11, 2000.

    Cassini is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages Cassini for NASA's Office of Space Science, Washington, D.C.

  17. Satellite Rings Movie

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This brief movie clip (of which the release image is a still frame), taken by NASA's Cassini spacecraft as it approached Jupiter, shows the motions, over a 16 hour-period, of two satellites embedded in Jupiter's ring. The moon Adrastea is the fainter of the two, and Metis the brighter. Images such as these will be used to refine the orbits of the two bodies.

    The movie was made from images taken during a 40-hour sequence of the Jovian ring on December 11, 2000.

    Cassini is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages Cassini for NASA's Office of Space Science, Washington, D.C.

  18. Strained Ring Energetic Binders

    DTIC Science & Technology

    1993-08-27

    polyhomobenzvalene ( PHBV ). PHBV was not found to have the mechanical instability problems of PBV, but was still thermally unstable (Tonset - 660C, Tmax - 1090C...DISCUSSION 4 Polybenzvalene (PBV) 4 Polyhomobenzvalene ( PHBV ) 6 Chain-Transfer Studies 11 CONCLUSIONS 15 EXPERIMENTAL PROCEDURES 16 .F 4E 19 APPENDICES A...strained ring polymers similar to PBV are known. The investigation of one of these polymers, polyhomobenzvalene ( PHBV ), is also described in this report

  19. Which Ringed Planet...!?

    NASA Astrophysics Data System (ADS)

    2002-12-01

    Don't worry - you are not the only one who thought this was a nice amateur photo of planet Saturn, Lord of the Rings in our Solar System! But then the relative brightness and positions of the moons may appear somewhat unfamiliar... and the ring system does look unusually bright when compared to the planetary disk...?? Well, it is not Saturn, but Uranus , the next giant planet further out, located at a distance of about 3,000 million km, or 20 times the distance between the Sun and the Earth. The photo shows Uranus surrounded by its rings and some of the moons, as they appear on a near-infrared image that was obtained in the K s -band (at wavelength 2.2 µm) with the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile) . The exposure was made on November 19, 2002 (03:00 hrs UT) during a planetary research programme. The observing conditions were excellent (seeing 0.5 arcsec) and the exposure lasted 5 min. The angular diameter of Uranus is about 3.5 arcsec. The observers at ISAAC were Emmanuel Lellouch and Thérése Encrenaz of the Observatoire de Paris (France) and Jean-Gabriel Cuby and Andreas Jaunsen (both ESO-Chile). The rings The rings of Uranus were discovered in 1977, from observations during a stellar occultation event by astronomer teams at the Kuiper Airborne Observatory (KAO) and the Perth Observatory (Australia). Just before and after the planet moved in front of the (occulted) star, the surrounding rings caused the starlight to dim for short intervals of time. Photos obtained from the Voyager-2 spacecraft in 1986 showed a multitude of very tenuous rings. These rings are almost undetectable from the Earth in visible light. However, on the present VLT near-infrared picture, the contrast between the rings and the planet is strongly enhanced. At the particular wavelength at which this observation was made, the infalling sunlight is almost completely absorbed by gaseous methane present in the planetary atmosphere

  20. Precooler Ring Vacuum System

    SciTech Connect

    Moenich, J.

    1980-10-02

    The precooler vacuum system, as proposed by FNAL, is based on a suitable modification of the existing Electron Cooling Ring System. Because of the magnetic cycle of the bending magnets, distributed ion pumping, as exists in the Electron Cooling Ring, is not applicable. Instead, the proposed pumping will be done with commercial appendage ion pumps mounted approximately every two meters around the circumference of the ring. The loss of effective pumping speed and non-uniformity of system pressure with appendage pumps may not be major considerations but the large number required does effect experimental and analytical equipment placement considerations. There is a distributed pumping technique available which: (1) is not affected by the magnetic cycle of the bending magnets; (2) will provide a minimum of four times the hydrogen pumping speed of the proposed appendage ion pumps; (3) will require no power during pumping after the strip is activated; (4) will provide the heat source for bakeout; (5) is easily replaceable; and (6) can be purchased, installed, and operated at a generous economic advantage over the presently proposed ion pumped system. The pumping technique referred to is non-evaporable gettering with ST101 Zr/Al pumping strip. A technical description of this pumping strip is given on Data Sheet 1 and 2 attached to this report.

  1. Swarming rings of bacteria.

    NASA Astrophysics Data System (ADS)

    Brenner, M. P.; Levitov, L. S.

    1996-03-01

    The behavior of bacterii controlled by chemotaxis can lead to a complicated spatial organization, producing swarming rings, and steady or moving aggregates( E. O. Budrene, and H. C. Berg, Complex patterns formed by motile cells of Escherichia coli. Nature 349, 630-633 (1991). ). We present a simple theory that explains the experimentally observed structures, by solving analytically two coupled differential equations, for the densities of bacterii and of chemoattractant. The equations have an interesting relation to the exactly solvable Burgers equation, and admit soliton-like solutions, that can be steady or moving. In addition, we find that there are singular solutions to the equations in which the bacterial density diverges. The theory agrees very well with the experiment: the solitons correspond to the observed travelling rings, the singularities describe formation of aggregates. In particular, the theory explains why the velocity of swarming rings decreases with the increase of the food concentration, the fact apparently not accounted by other existing approaches( L. Tsimring et. al., Phys. Rev. Lett., 75, 1859 (1995); Woodward, et al, Biophysical Journal, 68, 2181-2189 (1995). ).

  2. Saturn's ``Gossamer'' Ring: The F Ring's Inner Sheet

    NASA Astrophysics Data System (ADS)

    Showalter, M. R.; Burns, J. A.; Hamilton, D. P.

    1998-09-01

    Recent Galileo and Earth-based images have revealed for the first time that Jupiter's ``gossamer'' ring is actually composed of two rings, one bounded at the outer edge by Amalthea and the other bounded by Thebe. Dynamical models suggest that these rings are composed of dust grains ejected off the surfaces of the two moons, which then evolve inward under Poynting-Robertson drag. A very faint sheet of material filling the region between Saturn's A and F Rings reported by Burns et al. (BAAS 15, 1013--1014, 1983) may be a dynamically analogous system, in which dust escapes from the F Ring and evolves inward to the A Ring. Unlike Jupiter's gossamer rings, however, the inner sheet of Saturn's F Ring has been well observed from a large range of phase angles and visual wavelengths by Voyager. Voyager images reveal that this faint ring shows a tenfold increase in brightness between phase angles of 125(deg) and 165(deg) , indicating that it is composed of fine dust microns in size. Preliminary estimates of the normal optical depth fall in the range 1--2*E(-4) , depending on the dust size distribution assumed. Initial spectrophotometry reveals that the ring is neutral in color. The ring is uniform in brightness over the entire region between the two rings, with no evidence for internal structure associated with Prometheus and Atlas, suggesting that neither of these embedded moons acts as either a source or a sink. We will refine the aforementioned measurements and develop photometric models to better constrain the properties of the dust in this ring. This will enable us to relate the dust population to that in the F Ring proper, and to better explore the dynamical processes at work.

  3. Spatial data discretization methods for geocomputation

    NASA Astrophysics Data System (ADS)

    Cao, Feng; Ge, Yong; Wang, Jinfeng

    2014-02-01

    Geocomputation provides solutions to complex geographic problems. Continuous and discrete spatial data are involved in the geocomputational process; however, geocomputational methods for discrete spatial data cannot be directly applied to continuous or mixed spatial data. Therefore, discretization methods for continuous or mixed spatial data are involved in the process. Since spatial data has spatial features, such as association, heterogeneity and spatial structure, these features cannot be handled by traditional discretization methods. Therefore, this work develops feature-based spatial data discretization methods that achieve optimal discretization results for spatial data using spatial information implicit in those features. Two discretization methods considering the features of spatial data are presented. One is an unsupervised method considering autocorrelation of spatial data and the other is a supervised method considering spatial heterogeneity. Discretization processes of the two methods are exemplified using neural tube defects (NTD) for Heshun County in Shanxi Province, China. Effectiveness is also assessed.

  4. Physical properties of Uranian delta ring from a possible density wave

    NASA Technical Reports Server (NTRS)

    Horn, L. J.; Lane, A. L.; Yanamandra-Fisher, P. A.; Esposito, L. W.

    1988-01-01

    On the basis of wavelength and amplitude behavior, as well as observed feature morphology, that are indicative of a density wave, the presently studied Voyager PPS stellar occultation observations of the Uranus delta ring are held to indicate the presence of a moonlet interior to the delta ring. Lindblad resonances are calculated for all 65 discrete possible locations for this moonlet; the locations are labeled by azimuth number of the resonance associated with each location that would excite the observed density wave in the delta ring.

  5. Systoles in discrete dynamical systems

    NASA Astrophysics Data System (ADS)

    Fernandes, Sara; Grácio, Clara; Ramos, Carlos Correia

    2013-01-01

    The fruitful relationship between Geometry and Graph Theory has been explored by several authors benefiting also the Theory of discrete dynamical systems seen as Markov chains in graphs. In this work we will further explore the relation between these areas, giving a geometrical interpretation of notions from dynamical systems. In particular, we relate the topological entropy with the systole, here defined in the context of discrete dynamical systems. We show that for continuous interval maps the systole is trivial; however, for the class of interval maps with one discontinuity point the systole acquires relevance from the point of view of the dynamical behavior. Moreover, we define the geodesic length spectrum associated to a Markov interval map and we compute the referred spectrum in several examples.

  6. Dark energy from discrete spacetime.

    PubMed

    Trout, Aaron D

    2013-01-01

    Dark energy accounts for most of the matter-energy content of our universe, yet current theories of its origin rely on radical physical assumptions such as the holographic principle or controversial anthropic arguments. We give a better motivated explanation for dark energy, claiming that it arises from a small negative scalar-curvature present even in empty spacetime. The vacuum has this curvature because spacetime is fundamentally discrete and there are more ways for a discrete geometry to have negative curvature than positive. We explicitly compute this effect using a variant of the well known dynamical-triangulations (DT) model for quantum gravity. Our model predicts a time-varying non-zero cosmological constant with a current value, [Formula: see text] in natural units, in agreement with observation. This calculation is made possible by a novel characterization of the possible DT action values combined with numerical evidence concerning their degeneracies.

  7. Dark Energy from Discrete Spacetime

    PubMed Central

    Trout, Aaron D.

    2013-01-01

    Dark energy accounts for most of the matter-energy content of our universe, yet current theories of its origin rely on radical physical assumptions such as the holographic principle or controversial anthropic arguments. We give a better motivated explanation for dark energy, claiming that it arises from a small negative scalar-curvature present even in empty spacetime. The vacuum has this curvature because spacetime is fundamentally discrete and there are more ways for a discrete geometry to have negative curvature than positive. We explicitly compute this effect using a variant of the well known dynamical-triangulations (DT) model for quantum gravity. Our model predicts a time-varying non-zero cosmological constant with a current value, in natural units, in agreement with observation. This calculation is made possible by a novel characterization of the possible DT action values combined with numerical evidence concerning their degeneracies. PMID:24312502

  8. Observability of discretized partial differential equations

    NASA Technical Reports Server (NTRS)

    Cohn, Stephen E.; Dee, Dick P.

    1988-01-01

    It is shown that complete observability of the discrete model used to assimilate data from a linear partial differential equation (PDE) system is necessary and sufficient for asymptotic stability of the data assimilation process. The observability theory for discrete systems is reviewed and applied to obtain simple observability tests for discretized constant-coefficient PDEs. Examples are used to show how numerical dispersion can result in discrete dynamics with multiple eigenvalues, thereby detracting from observability.

  9. Helmet latching and attaching ring

    NASA Technical Reports Server (NTRS)

    Chase, E. W.; Viikinsalo, S. J. (Inventor)

    1970-01-01

    A neck ring releasably secured to a pressurized garment carries an open-ended ring normally in the engagement position fitted into an annular groove and adapted to fit into a complementary annular groove formed in a helmet. Camming means formed on the inner surface at the end of the helmet engages the open-ended ring to retract the same and allow for one motion donning even when the garment is pressurized. A projection on the end of the split ring is engageable to physically retract the split ring.

  10. Planetary ring dynamics and morphology

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Durisen, Richard H.; Shu, Frank H.

    1987-01-01

    Evidence for a moonlet belt in the region between Saturn's close-in moonrings Pandora and Prometheus is discussed. It is argued that little-known observations of magnetospheric electron density by Pioneer 11 imply substantial, ongoing injections of mass into the 2000 km region which surrounds the F ring. A hypothesis is presented that these events result naturally from interparticle collisions between the smaller members of an optically thin belt of moonlets. Also discussed is work on Uranus ring structure and photometry, image processing and analysis of the Jonian ring strucure, photometric and structural studies of the A ring of Saturn, and improvements to an image processing system for ring studies.

  11. Interference in discrete Wigner functions

    SciTech Connect

    Cormick, Cecilia; Paz, Juan Pablo

    2006-12-15

    We analyze some features of the class of discrete Wigner functions that was recently introduced by Gibbons et al. [Phys. Rev. A 70, 062101 (2004)] to represent quantum states of systems with power-of-prime dimensional Hilbert spaces. We consider ''cat'' states obtained as coherent superpositions of states with positive Wigner function; for such states we show that the oscillations of the discrete Wigner function typically spread over the entire discrete phase space (including the regions where the two interfering states are localized). This is a generic property, which is in sharp contrast with the usual attributes of Wigner functions that make them useful candidates to display the existence of quantum coherence through oscillations. However, it is possible to find subsets of cat states with a natural phase-space representation, in which the oscillatory regions remain localized. We show that this can be done for interesting families of stabilizer states used in quantum error-correcting codes, and illustrate this by analyzing the phase-space representation of the five-qubit error-correcting code.

  12. Umbral Deformations on Discrete SPACE TIME

    NASA Astrophysics Data System (ADS)

    Zachos, Cosmas K.

    Given a minimum measurable length underlying spacetime, the latter may be effectively regarded as discrete, at scales of order the Planck length. A systematic discretization of continuum physics may be effected most efficiently through the umbral deformation. General functionals yielding such deformations at the level of solutions are furnished and illustrated, and broad features of discrete oscillations and wave propagation are outlined.

  13. Discrete Optimization in Chemical Space Reference Manual

    DTIC Science & Technology

    2012-10-01

    Discrete Optimization in Chemical Space Reference Manual by B. C. Rinderspacher ARL-TR-6202 October 2012...2012 Discrete Optimization in Chemical Space Reference Manual B. C. Rinderspacher Weapons and Materials Research Directorate, ARL...2011 4. TITLE AND SUBTITLE Discrete Optimization in Chemical Space Reference Manual 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  14. Ring Autosomes: Some Unexpected Findings

    PubMed Central

    Caba, L; Rusu, C; Plăiaşu; Gug, G; Grămescu, M; Bujoran, C; Ochiană, D; Voloşciuc, M; Popescu, R; Braha, E; Pânzaru, M; Butnariu, L; Sireteanu, A; Covic, M; Gorduza, EV

    2012-01-01

    Ring chromosomes are rare entities, usually associated with phenotypic abnormalities in correlation with the loss of genetic material. There are various breakpoints and sometimes there is a dynamic mosaicism that is reflected in clinical features. Most of the ring chromosomes are de novo occurrences. Our study reflects the experience of three Romanian cytogenetic laboratories in the field of ring chromosomes. We present six cases with ring chromosomes involving chromosomes 5, 13, 18, and 21. All ring chromosomes were identified after birth in children with plurimalformative syndromes. The ring chromosome was present in mosaic form in three cases, and this feature reflects the ring’s instability. In case of ring chromosome 5, we report a possible association with oculo-auriculo-vertebral spectrum. PMID:24052730

  15. Mass of Saturn's A ring

    NASA Technical Reports Server (NTRS)

    Horn, L. J.; Russell, C. T.

    1993-01-01

    The mass of Saturn's A ring is reestimated using the behavior of spiral density waves embedded in the ring. The Voyager photopolarimeter (PPS) observed the star delta-Scorpii as it was occulted by Saturn's rings during the Voyager 2 flyby of Saturn in 1981 producing a radial profile of the rings. We examined forty spiral density waves in the Voyager PPS data of the A ring including 10 weaker waves that have not been previously analyzed by means of an autoregressive power spectral technique called Burg. The strengths of this new method for ring studies are that weaker, less extended waves are easily detected and characterized. This method is also the first one which does not require precise knowledge of the resonance location and phase of the wave in order to calculate the surface mass density. Uncertainties of up to 3 km are present in the currently available radial scales for Saturn's rings.

  16. A season in Saturn's rings: Cycling, recycling and ring history

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Meinke, B. K.; Albers, N.; Sremcevic, M.

    2012-04-01

    Cassini experiments have watched Saturn's ring system evolve before our eyes. Images and occultations show changes and transient events. The rings are a dynamic and complex geophysical system, incompletely modeled as a single-phase fluid. Key Cassini observations: High resolution images show straw, propellers, embedded moonlets, and F ring objects. Multiple UVIS, RSS and VIMS occutlations indicate multimodal ringlet and edge structure, including free and forced modes along with stochastic perturbations that are most likely caused by nearby mass concentrations. Vertical excursions are evident at ring edges and in other perturbed regions. The rings are occasionally hit by meteorites that leave a signature that may last centuries; meteoritic dust pollutes the rings. Temperature, reflectance and transmission spectra are influenced by the dynamical state of the ring particles. Saturn's Equinox 2009: Oblique lighting exposed vertical structure and embedded objects. The rings were the coldest ever. Images inspired new occultation and spectral analysis that show abundant structure in the perturbed regions. The rings are more variable and complex than we had expected prior to this seasonal viewing geometry. Sub-kilometer structure in power spectral analysis: Wavelet analysis shows features in the strongest density waves and at the shepherded outer edge of the B ring. Edges are variable as shown by multiple occultations and occultations of double stars. F ring kittens: 25 features seen in the first 102 occultations show a weak correlation with Prometheus location. We interpret these features as temporary aggregations. Simulation results indicate that accretion must be enhanced to match the kittens' size distribution. Images show that Prometheus triggers the formation of transient objects. Propellers and ghosts: Occulations and images provide evidence for small moonlets in the A, B and C rings. These indicate accretion occurs inside the classical Roche limit. Implications

  17. New Views of Jupiter's Rings

    NASA Astrophysics Data System (ADS)

    Burns, J. A.

    1998-09-01

    Jupiter's rings are the archetype of ethereal planetary rings (very-low optical-depth bands containing micron-sized "dust"). As a result of much improved observations by Galileo (Ockert-Bell* -- most citations are et al. and Icarus in press* or this meeting) and Keck (de Pater*), we now understand the nature of such rings. The ring has three components: a 104 km-thick toroidal halo (1.4-1.7 RJ; normal optical depth t = 10-6), a thin main ring (1.7-1.8 RJ; t = 10-6), and a pair of exterior gossamer rings (1.8-3.5RJ; t = 10-7). The main ring has patchy ( 20-30 percent) brightness. The ring is reddish and its particles satisfy a -2.5 differential power-law size distribution. Because particle lifetimes are brief, the rings must be continually regenerated, by collisions into parent bodies, which may be unseen or may be the known small ring-moons (Thomas*, Simonelli). The gossamer ring seems to be collisional ejecta derived from the ring-moons Amalthea and Thebe, and evolving inward by Poynting-Robertson drag (Burns). The particles drift through many electromagnetic resonances, clustering around synchronous orbit, which produce jumps in the particles' inclinations (Hamilton). The main ring is probably debris from Adrastea and Metis, which orbit in the equatorial plane. The halo particles are driven vertically by electromagnetic forces, which may be resonant (Schaffer & Burns) or not (Horanyi & Cravens). When halo orbits become highly distorted, particles are lost into Jupiter. Similar faint rings may be attendant to all small, close-in satellites (Showalter).

  18. Tree Rings: Timekeepers of the Past.

    ERIC Educational Resources Information Center

    Phipps, R. L.; McGowan, J.

    One of a series of general interest publications on science issues, this booklet describes the uses of tree rings in historical and biological recordkeeping. Separate sections cover the following topics: dating of tree rings, dating with tree rings, tree ring formation, tree ring identification, sample collections, tree ring cross dating, tree…

  19. On equivalence of discrete-discrete and continuum-discrete design sensitivity analysis

    NASA Technical Reports Server (NTRS)

    Choi, Kyung K.; Twu, Sung-Ling

    1989-01-01

    Developments in design sensitivity analysis (DSA) method have been made using two fundamentally different approaches as shown. In the first approach, a discretized structural finite element model is used to carry out DSA. There are three different methods in the discrete DSA approach: finite difference, semi-analytical, and analytical methods. The finite difference method is a popular one due to its simplicity, but a serious shortcoming of the method is the uncertainty in the choice of a perturbation step size of design variables. In the semi-analytical method, the derivatives of stiffness matrix is computed by finite differences, whereas in the analytical method, the derivatives are obtained analytically. For the shape design variable, computation of analytical derivative of stiffness matrix is quite costly. Because of this, the semi-analytical method is a popular choice in discrete shape DSA approach. However, recently, Barthelemy and Haftka presented that the semi-analytical method can have serious accuracy problems for shape design variables in structures modeled by beam, plate, truss, frame, and solid elements. They found that accuracy problems occur even for a simple cantilever beam. In the second approach, a continuum model of the structure is used to carry out DSA.

  20. Ring currents in azulene

    NASA Astrophysics Data System (ADS)

    Paxton, A. T.; Todorov, T. N.; Elena, A. M.

    2009-11-01

    We propose a self consistent polarisable ion tight binding theory for the study of push-pull processes in aromatic molecules. We find that the method quantitatively reproduces ab initio calculations of dipole moments and polarisability. We apply the scheme in a simulation which solves the time dependent Schrödinger equation to follow the relaxation of azulene from the second excited to the ground states. We observe rather spectacular oscillating ring currents which we explain in terms of interference between the HOMO and LUMO states.

  1. Wave structure in planetary rings

    NASA Astrophysics Data System (ADS)

    Horn, Linda Joyce

    1992-01-01

    Planetary rings contain a wealth of wavelike structure that is driven by gravitational resonance interactions with nearby satellites. Wave behavior is a powerful tool for estimating physical ring parameters that are key to our understanding of ring origin and evolution. A new technique, utilizing the Burg autoregressive power spectral algorithm, was developed for probing the physical characteristics of rings and for detecting waves that are not otherwise visible. Data from the Voyager photopolarimeter (PPS) stellar occultations by the rings of Saturn, Uranus, and Neptune and the Voyager radio science (RSS) occultation by Saturn's rings were used. Local surface mass density estimates are obtained from the dispersion of 40 spiral density waves in Saturn's A ring, including 10 weaker waves not previously analyzed. Surface mass densities vary from 20 to 60 gm sq cm. Increasing optical depth is not correlated with increasing surface mass density, especially after the Keeler gap, suggesting that ring particle size and composition are not uniform throughout the A ring. Saturn's A ring mass is reestimated using the surface mass densities and is 5.2 +/- 1.3 x 1021 gm. The wakes of Saturn's satellite Pan are not short timescale phenomena because the effects of Pan's gravitational perturbations persist for more than one Pan encounter. Four additional Pan wakes were discovered at longitudes greater than 360 deg. Collective effects such as collisions modify the wake dispersion more extensively at greater longitudes. Pan is the dominant mass in the Encke gap. A spiral density wave was detected inside the Uranian delta ring. Upper and lower bounds were estimated for the surface mass density of the delta ring 5 less than or equal to sigma less than or equal to 10 gm/sq cm, the viscosity 10 less than or equal to nu less than or equal to 40 sq cm/sec, and the local ring height 7 less than or equal to h less than or equal to 20 m. These values are comparable to the corresponding

  2. Orbits of nine Uranian rings

    NASA Technical Reports Server (NTRS)

    Elliot, J. L.; French, R. G.; Frogel, J. A.; Elias, J. H.; Mink, D. J.; Liller, W.

    1981-01-01

    Observations of a stellar occultation by Uranus and its nine rings are presented and used to examine the structures and kinematics of the rings. The observations of the occultation of the K giant star KM 12 were obtained in the K band with the 4-m CTIO telescope at a signal-to-noise ratio higher than any previously obtained. Ring occultation profiles reveal the alpha ring to possibly have a double structure and less abrupt boundaries than the gamma ring, which exhibits diffraction fringes, while the eta ring is a broad ring with an unresolved narrow component at its inner edge. The present timing data, as well as previous occultation timings, are fit to a kinematic model in which all nine rings are treated as coplanar eclipses of zero inclination, precessing due to the zonal harmonics of the Uranian gravitational potential to obtain solutions for the ring orbits. Analysis of the residuals from the fitted orbits reveals that the proposed model is a good representation of ring kinematics. The reference system defined by the orbit solutions has also been used to obtain a value of 0.022 + or - 0.003 for the ellipticity of Uranus and a Uranian rotation period of 15.5 h.

  3. The Charging of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Graps, Amara L.; Horanyi, M.; Havnes, O.; Gruen, E.

    2008-09-01

    Planetary rings have an undeniable aesthetic appeal, resulting in media icons of ringed planets as descriptive of the planetary sciences field as a whole. Such far-reaching symbolism might not be misplaced, however, because planetary rings represent a fundamental class of planetary structure that invites interdisciplinary investigations from specialists in dust, gravitational, plasma, collisional, and radiative transfer physics, due to: its sub-micron to meters-sized particles, its immersion in the planet's magnetic field, its embedded moonlets and its close proximity to the ringed planet's ionosphere and innermost moons. As such, planetary rings are a metaphoric bridge through a wide range of planetary physical processes. Processes to charge ring particles have different relative dynamical effects, dependent upon the rings' particle sizes, and the ring's plasma, magnetic and gravitational environments. This presentation will review what is known about the charging parameters and processes of planetary rings, in particular the sum of the individual currents from the time-varying charge dQ/dt, of the planetary ring particle. The individual currents depend on the environmental plasma conditions: number density, flow speed, temperature, and mass for the currents: electron and ion capture from the plasma, ion currents to a moving grain, photoelectron emission, secondary electron emission, thermionic effects, with stochastic charging influencing all of the above. Since rings are an ensemble of particles, ("cloud" Ring), we will define an ensemble, and consider the above currents, including those for the smallest ring particles, the dust particles, to arrive at a table giving charge potential and other relevant parameters.

  4. Ring artifacts removal from synchrotron CT image slices

    NASA Astrophysics Data System (ADS)

    Wei, Zhouping; Wiebe, Sheldon; Chapman, Dean

    2013-06-01

    Ring artifacts can occur in reconstructed images from x-ray Computerized Tomography (CT) as full or partial concentric rings superimposed on the scanned structures. Due to the data corruption by those ring artifacts in CT images, qualitative and quantitative analysis of these images are compromised. In this paper, we propose to correct the ring artifacts on the reconstructed synchrotron radiation (SR) CT image slices. The proposed correction procedure includes the following steps: (1). transform the reconstructed CT images into polar coordinates; (2) apply discrete two-dimensional (2D) wavelet transform to the polar image to decompose it into four image components: low pass band image component, as well as the components from horizontal, vertical and diagonal details bands; (3). apply 2D Fourier transform to the vertical details band image component only, since the ring artifacts become vertical lines in the polar coordinates; (4). apply Gaussian filtering in Fourier domain along the abscissa direction to suppress the vertical lines, since the information of the vertical lines in Fourier domain is completely condensed to that direction; (5). perform inverse Fourier transform to get the corrected vertical details band image component; (6). perform inverse wavelet transform to get the corrected polar image; (7). transform the corrected polar image back to Cartesian coordinates to get the CT image slice with reduced ring artifacts. This approach has been successfully used on CT data acquired from the Biomedical Imaging and Therapy (BMIT) beamline in Canadian Light Source (CLS), and the results show that the ring artifacts in original SR CT images have been effectively suppressed with all the structure information in the image preserved.

  5. Mechanical supporting ring structure

    NASA Astrophysics Data System (ADS)

    Tserodze, Sh.; Medzmariashvili, E.; Tusishvili, O.; Tsignadze, N.; Santiago-Prowald, J.; ‘t Klooster, C. G. M.; Medzmariashvili, N.

    2013-12-01

    Large deployable antenna reflectors are commonly employed for space missions. Scientific, telecommunications and earth observation applications are enabled due to the antenna gain provided by the large apertures (8-25 m). The most relevant requirements that drive the design are the size of the stowed package diameter (0.4-1.50 m), the mass (18-160 kg), the control of the deployment process, the accuracy and stability of the surface and the RF performance requirements. In this paper a new architecture of conical ring reflector is described, with the objective of providing a response to the mentioned requirements. The projected aperture range of 8-25 m is addressed, enabling to create offset reflectors of elliptical rim. The configuration is based on a double pantograph conical ring. It is an architecture suitable for reflector-based radar in LEO missions from P to C band, although the expected stiffness and stability can be seen as an asset for higher operational frequencies. The configuration of the structure is new and has been preliminarily discussed in the paper. Further investigations might well be of interest.

  6. Storage ring injection

    SciTech Connect

    Burke, R.J.

    1980-01-01

    Some basic issues involved in injecting the beam into storage rings with the principal parameters of those studied at the workshop have been considered. The main conclusion is that straightforward adjustments of the storage ring parameters makes injection easy. The largest number of injected turns is fourteen, and the phase space dilution allowance seems adequate to ensure very small beam loss during injection. The adjustments also result in lower bending magnet fields, and high field superconducting magnets (e.g., 5 Tesla) are not necessary. The design changes do not necessarily affect the Keil-Schnell criterion for stability of the longitudinal microwave instability, although that criterion appears to be irrelevant. Because the beams are expected to be unstable, but with slow growth rates, the vacuum chamber impedances required to give equal risetimes for the various designs are compared for systems posing various degrees of difficulty for injection. Finally, the impact of the parameters on cost is noted, and a system is considered that cuts the length of the linac in half by using doubly charged ions.

  7. Vortex and Rings

    NASA Image and Video Library

    2014-07-07

    NASA Cassini spacecraft captures three magnificent sights at once: Saturn north polar vortex and hexagon along with its expansive rings. The hexagon, which is wider than two Earths, owes its appearance to the jet stream that forms its perimeter. The jet stream forms a six-lobed, stationary wave which wraps around the north polar regions at a latitude of roughly 77 degrees North. This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on April 2, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 1.4 million miles (2.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 43 degrees. Image scale is 81 miles (131 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18274

  8. Buoyant Norbury's vortex rings

    NASA Astrophysics Data System (ADS)

    Blyth, Mark; Rodriguez-Rodriguez, Javier; Salman, Hayder

    2014-11-01

    Norbury's vortices are a one-parameter family of axisymmetric vortex rings that are exact solutions to the Euler equations. Due to their relative simplicity, they are extensively used to model the behavior of real vortex rings found in experiments and in Nature. In this work, we extend the original formulation of the problem to include buoyancy effects for the case where the fluid that lies within the vortex has a different density to that of the ambient. In this modified formulation, buoyancy effects enter the problem through the baroclinic term of the vorticity equation. This permits an efficient numerical solution of the governing equation of motion in terms of a vortex contour method that tracks the evolution of the boundary of the vortex. Finally, we compare our numerical results with the theoretical analysis of the short-time evolution of a buoyant vortex. Funded by the Spanish Ministry of Economy and Competitiveness through grant DPI2011-28356-C03-02 and by the London Mathematical Society.

  9. Ring Image Analyzer

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry V.

    2012-01-01

    Ring Image Analyzer software analyzes images to recognize elliptical patterns. It determines the ellipse parameters (axes ratio, centroid coordinate, tilt angle). The program attempts to recognize elliptical fringes (e.g., Newton Rings) on a photograph and determine their centroid position, the short-to-long-axis ratio, and the angle of rotation of the long axis relative to the horizontal direction on the photograph. These capabilities are important in interferometric imaging and control of surfaces. In particular, this program has been developed and applied for determining the rim shape of precision-machined optical whispering gallery mode resonators. The program relies on a unique image recognition algorithm aimed at recognizing elliptical shapes, but can be easily adapted to other geometric shapes. It is robust against non-elliptical details of the image and against noise. Interferometric analysis of precision-machined surfaces remains an important technological instrument in hardware development and quality analysis. This software automates and increases the accuracy of this technique. The software has been developed for the needs of an R&TD-funded project and has become an important asset for the future research proposal to NASA as well as other agencies.

  10. Discrete Boltzmann equation for microfluidics.

    PubMed

    Li, Baoming; Kwok, Daniel Y

    2003-03-28

    We propose a discrete Boltzmann model for microfluidics based on the Boltzmann equation with external forces using a single relaxation time collision model. Considering the electrostatic interactions in microfluidics systems, we introduce an equilibrium distribution function that differs from the Maxwell-Boltzmann distribution by an exponential factor to represent the action of an external force field. A statistical mechanical approach is applied to derive the equivalent external acceleration force exerting on the lattice particles based on a mean-field approximation, resulting from the electro-static potential energy and intermolecular potential energy between fluid-fluid and fluid-substrate interactions.

  11. Invariants of broken discrete symmetries.

    PubMed

    Kalozoumis, P A; Morfonios, C; Diakonos, F K; Schmelcher, P

    2014-08-01

    The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries in one dimension are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying, in particular, to acoustic, optical, and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.

  12. Invariants of Broken Discrete Symmetries

    NASA Astrophysics Data System (ADS)

    Kalozoumis, P. A.; Morfonios, C.; Diakonos, F. K.; Schmelcher, P.

    2014-08-01

    The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries in one dimension are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying, in particular, to acoustic, optical, and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.

  13. Saturn's rings - A new survey

    NASA Technical Reports Server (NTRS)

    Cook, A. F.; Franklin, F. A.

    1977-01-01

    Observations of radar returns from Saturn's rings, together with radio interferometry of their absorption of radiation from the disk, combine to require an effective radius of ring particles of about 6 cm or larger. It is suggested that the ring particles may also include, in addition to the known ice constituent, a mixture of the clathrated hydrate of methane and ammonia hydrate. A two-density model for ring particles is possible in which a matrix of low density contains many nodules of higher-density ice particles; in this case, radii nearly as large as the observed ring thickness would be possible. Improved resolution in radio observations at 21 cm or, if necessary, at longer wavelengths for narrow ring openings is perhaps the most useful method for determining upper limits on the particle size.

  14. Ring current and radiation belts

    NASA Technical Reports Server (NTRS)

    Williams, D. J.

    1987-01-01

    Studies performed during 1983-1986 on the ring current, the injection boundary model, and the radiation belts are discussed. The results of these studies yielded the first observations on the composition and charge state of the ring current throughout the ring-current energy range, and strong observational support for an injection-boundary model accounting for the origins of radiation-belt particles, the ring current, and substorm particles observed at R less than about 7 earth radii. In addition, the results have demonstrated that the detection of energetic neutral atoms generated by charge-exchange interactions between the ring current and the hydrogen geocorona can provide global images of the earth's ring current and its spatial and temporal evolution.

  15. Reversible Rings with Involutions and Some Minimalities

    PubMed Central

    Fakieh, W. M.; Nauman, S. K.

    2013-01-01

    In continuation of the recent developments on extended reversibilities on rings, we initiate here a study on reversible rings with involutions, or, in short, ∗-reversible rings. These rings are symmetric, reversible, reflexive, and semicommutative. In this note we will study some properties and examples of ∗-reversible rings. It is proved here that the polynomial rings of ∗-reversible rings may not be ∗-reversible. A criterion for rings which cannot adhere to any involution is developed and it is observed that a minimal noninvolutary ring is of order 4 and that a minimal noncommutative ∗-reversible ring is of order 16. PMID:24489510

  16. Discrete cyclic porphyrin arrays as artificial light-harvesting antenna.

    PubMed

    Aratani, Naoki; Kim, Dongho; Osuka, Atsuhiro

    2009-12-21

    The importance of photosynthesis has driven researchers to seek ways to mimic its fundamental features in simplified systems. The absorption of a photon by light-harvesting (antenna) complexes made up of a large number of protein-embedded pigments initiates photosynthesis. Subsequently the many pigments within the antenna system shuttle that photon via an efficient excitation energy transfer (EET) until it encounters a reaction center. Since the 1995 discovery of the circularly arranged chromophoric assemblies in the crystal structure of light-harvesting antenna complex LH2 of purple bacteria Rps. Acidophila, many designs of light-harvesting antenna systems have focused on cyclic porphyrin wheels that allow for efficient EET. In this Account, we review recent research in our laboratories in the synthesis of covalently and noncovalently linked discrete cyclic porphyrin arrays as models of the photosynthetic light-harvesting antenna complexes. On the basis of the silver(I)-promoted oxidative coupling strategy, we have prepared a series of extremely long yet discrete meso-meso-linked porphyrin arrays and covalently linked large porphyrin rings. We examined the photophysical properties of these molecules using steady-state absorption, fluorescence, fluorescence lifetime, fluorescence anisotropy decay, and transient absorption measurements. Both the pump-power dependence on the femtosecond transient absorption and the transient absorption anisotropy decay profiles are directly related to the EET processes within the porphyrin rings. Within these structures, the exciton-exciton annihilation time and the polarization anisotropy rise time are well-described in terms of the Forster-type incoherent energy hopping model. In noncoordinating solvents such as CHCl(3), meso-pyridine-appended zinc(II) porphyrins and their meso-meso-linked dimers spontaneously assemble to form tetrameric porphyrin squares and porphyrin boxes, respectively. In the latter case, we have demonstrated

  17. Saturn's rings and associated ring plasma cavity: Evidence for slow ring erosion

    NASA Astrophysics Data System (ADS)

    Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Persoon, A. M.; MacDowall, R. J.

    2017-08-01

    We re-examine the radio and plasma wave observations obtained during the Cassini Saturn orbit insertion period, as the spacecraft flew over the northern ring surface into a radial distance of 1.3 Rs (over the C-ring). Voyager era studies suggest the rings are a source of micro-meteoroid generated plasma and dust, with theorized peak impact-created plasma outflows over the densest portion of the rings (central B-ring). In sharp contrast, the Cassini Radio and Plasma Wave System (RPWS) observations identify the presence of a ring-plasma cavity located in the central portion of the B-ring, with little evidence of impact-related plasma. While previous Voyager era studies have predicted unstable ion orbits over the C-ring, leading to field-aligned plasma transport to Saturn's ionosphere, the Cassini RPWS observations do not reveal evidence for such instability-created plasma 'fountains'. Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend >109 years, and that there is limited evidence for prompt destruction (loss in <100 Myrs).

  18. Saturn's Rings and Associated Ring Plasma Cavity: Evidence for Slow Ring Erosion

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Persoon, A. M.; MacDowall, R. J.

    2017-01-01

    We re-examine the radio and plasma wave observations obtained during the Cassini Saturn orbit insertion period, as the spacecraft flew over the northern ring surface into a radial distance of 1.3 Rs (over the C-ring). Voyager era studies suggest the rings are a source of micro-meteoroid generated plasma and dust, with theorized peak impact-created plasma outflows over the densest portion of the rings (central B-ring). In sharp contrast, the Cassini Radio and Plasma Wave System (RPWS) observations identify the presence of a ring-plasma cavity located in the central portion of the B-ring, with little evidence of impact-related plasma. While previous Voyager era studies have predicted unstable ion orbits over the C- ring, leading to field-aligned plasma transport to Saturns ionosphere, the Cassini RPWS observations do not reveal evidence for such instability-created plasma fountains. Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend >10(exp 9) years, and that there is limited evidence for prompt destruction (loss in <100 Myrs).

  19. Entwinement in discretely gauged theories

    NASA Astrophysics Data System (ADS)

    Balasubramanian, V.; Bernamonti, A.; Craps, B.; De Jonckheere, T.; Galli, F.

    2016-12-01

    We develop the notion of "entwinement" to characterize the amount of quantum entanglement between internal, discretely gauged degrees of freedom in a quantum field theory. This concept originated in the program of reconstructing spacetime from entanglement in holographic duality. We define entwinement formally in terms of a novel replica method which uses twist operators charged in a representation of the discrete gauge group. In terms of these twist operators we define a non-local, gauge-invariant object whose expectation value computes entwinement in a standard replica limit. We apply our method to the computation of entwinement in symmetric orbifold conformal field theories in 1+1 dimensions, which have an S N gauging. Such a theory appears in the weak coupling limit of the D1-D5 string theory which is dual to AdS3 at strong coupling. In this context, we show how certain kinds of entwinement measure the lengths, in units of the AdS scale, of non-minimal geodesics present in certain excited states of the system which are gravitationally described as conical defects and the M = 0 BTZ black hole. The possible types of entwinement that can be computed define a very large new class of quantities characterizing the fine structure of quantum wavefunctions.

  20. Supervised Discrete Hashing With Relaxation.

    PubMed

    Gui, Jie; Liu, Tongliang; Sun, Zhenan; Tao, Dacheng; Tan, Tieniu

    2016-12-29

    Data-dependent hashing has recently attracted attention due to being able to support efficient retrieval and storage of high-dimensional data, such as documents, images, and videos. In this paper, we propose a novel learning-based hashing method called ''supervised discrete hashing with relaxation'' (SDHR) based on ''supervised discrete hashing'' (SDH). SDH uses ordinary least squares regression and traditional zero-one matrix encoding of class label information as the regression target (code words), thus fixing the regression target. In SDHR, the regression target is instead optimized. The optimized regression target matrix satisfies a large margin constraint for correct classification of each example. Compared with SDH, which uses the traditional zero-one matrix, SDHR utilizes the learned regression target matrix and, therefore, more accurately measures the classification error of the regression model and is more flexible. As expected, SDHR generally outperforms SDH. Experimental results on two large-scale image data sets (CIFAR-10 and MNIST) and a large-scale and challenging face data set (FRGC) demonstrate the effectiveness and efficiency of SDHR.

  1. Discreteness effects in population dynamics

    NASA Astrophysics Data System (ADS)

    Guevara Hidalgo, Esteban; Lecomte, Vivien

    2016-05-01

    We analyse numerically the effects of small population size in the initial transient regime of a simple example population dynamics. These effects play an important role for the numerical determination of large deviation functions of additive observables for stochastic processes. A method commonly used in order to determine such functions is the so-called cloning algorithm which in its non-constant population version essentially reduces to the determination of the growth rate of a population, averaged over many realizations of the dynamics. However, the averaging of populations is highly dependent not only on the number of realizations of the population dynamics, and on the initial population size but also on the cut-off time (or population) considered to stop their numerical evolution. This may result in an over-influence of discreteness effects at initial times, caused by small population size. We overcome these effects by introducing a (realization-dependent) time delay in the evolution of populations, additional to the discarding of the initial transient regime of the population growth where these discreteness effects are strong. We show that the improvement in the estimation of the large deviation function comes precisely from these two main contributions.

  2. Split ring containment attachment device

    DOEpatents

    Sammel, Alfred G.

    1996-01-01

    A containment attachment device 10 for operatively connecting a glovebag 200 to plastic sheeting 100 covering hazardous material. The device 10 includes an inner split ring member 20 connected on one end 22 to a middle ring member 30 wherein the free end 21 of the split ring member 20 is inserted through a slit 101 in the plastic sheeting 100 to captively engage a generally circular portion of the plastic sheeting 100. A collar potion 41 having an outer ring portion 42 is provided with fastening means 51 for securing the device 10 together wherein the glovebag 200 is operatively connected to the collar portion 41.

  3. Saturn's Rings Edge-on

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In one of nature's most dramatic examples of 'now-you see-them, now-you-don't', NASA's Hubble Space Telescope captured Saturn on May 22, 1995 as the planet's magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn's ring plane.

    For comparison, the top picture was taken by Hubble on December 1, 1994 and shows the rings in a more familiar configuration for Earth observers.

    The bottom picture was taken shortly before the ring plane crossing. The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn's atmosphere. Two of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.

    This observation will be used to determine the time of ring-plane crossing and the thickness of the main rings and to search for as yet undiscovered satellites. Knowledge of the exact time of ring-plane crossing will lead to an improved determination of the rate at which Saturn 'wobbles' about its axis (polar precession).

    Both pictures were taken with Hubble's Wide Field Planetary Camera 2. The top image was taken in visible light. Saturn's disk appears different in the bottom image because a narrowband filter (which only lets through light that is not absorbed by methane gas in Saturn's atmosphere) was used to reduce the bright glare of the planet. Though Saturn is approximately 900 million miles away, Hubble can see details as small as 450 miles across.

    The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science

  4. Formation of lunar basin rings

    USGS Publications Warehouse

    Hodges, C.A.; Wilhelms, D.E.

    1978-01-01

    The origin of the multiple concentric rings that characterize lunar impact basins, and the probable depth and diameter of the transient crater have been widely debated. As an alternative to prevailing "megaterrace" hypotheses, we propose that the outer scarps or mountain rings that delineate the topographic rims of basins-the Cordilleran at Orientale, the Apennine at Imbrium, and the Altai at Nectaris-define the transient cavities, enlarged relatively little by slumping, and thus are analogous to the rim crests of craters like Copernicus; inner rings are uplifted rims of craters nested within the transient cavity. The magnitude of slumping that occurs on all scarps is insufficient to produce major inner rings from the outer. These conclusions are based largely on the observed gradational sequence in lunar central uplifts:. from simple peaks through somewhat annular clusters of peaks, peak and ring combinations and double ring basins, culminating in multiring structures that may also include peaks. In contrast, belts of slump terraces are not gradational with inner rings. Terrestrial analogs suggest two possible mechanisms for producing rings. In some cases, peaks may expand into rings as material is ejected from their cores, as apparently occurred at Gosses Bluff, Australia. A second process, differential excavation of lithologically diverse layers, has produced nested experimental craters and is, we suspect, instrumental in the formation of terrestrial ringed impact craters. Peak expansion could produce double-ring structures in homogeneous materials, but differential excavation is probably required to produce multiring and peak-in-ring configurations in large lunar impact structures. Our interpretation of the representative lunar multiring basin Orientale is consistent with formation of three rings in three layers detected seismically in part of the Moon-the Cordillera (basin-bounding) ring in the upper crust, the composite Montes Rook ring in the underlying

  5. Ground Movement in SSRL Ring

    SciTech Connect

    Sunikumar, Nikita; /UCLA /SLAC

    2011-08-25

    Users of the Stanford Synchrotron Radiation Lightsource (SSRL) are being affected by diurnal motion of the synchrotron's storage ring, which undergoes structural changes due to outdoor temperature fluctuations. In order to minimize the effects of diurnal temperature fluctuations, especially on the vertical motion of the ring floor, scientists at SSRL tried three approaches: painting the storage ring white, covering the asphalt in the middle of the ring with highly reflective Mylar and installing Mylar on a portion of the ring roof and walls. Vertical motion in the storage ring is measured by a Hydrostatic Leveling System (HLS), which calculates the relative height of water in a pipe that extends around the ring. The 24-hr amplitude of the floor motion was determined using spectral analysis of HLS data, and the ratio of this amplitude before and after each experiment was used to quantitatively determine the efficacy of each approach. The results of this analysis showed that the Mylar did not have any significant effect on floor motion, although the whitewash project did yield a reduction in overall HLS variation of 15 percent. However, further analysis showed that the reduction can largely be attributed to a few local changes rather than an overall reduction in floor motion around the ring. Future work will consist of identifying and selectively insulating these local regions in order to find the driving force behind diurnal floor motion in the storage ring.

  6. Statistical ring current of Saturn

    NASA Astrophysics Data System (ADS)

    Carbary, J. F.; Achilleos, N.; Arridge, C. S.

    2012-06-01

    The statistical ring current of Saturn has been determined from the curl of the median magnetic field derived from over 5 years of observations of the Cassini magnetometer. The main issue addressed here is the calculation of the statistical ring current of Saturn by directly computing, for the first time, the symmetrical part of the ring current J from the Maxwell equation ∇ × B = μ0J from assembling the perturbation magnetic field B from 2004 through 2010. This study validates previous studies, based on fewer data and not using ∇ × B, and shows that the ring current flows eastward (in the +ϕ or corotation direction) and extends from ˜3 RS to at least ˜20 RS (1 RS = 60,268 km), which is the vicinity of the dayside magnetopause; that the ring current has a peak strength of ˜75 pA/m2 at ˜9.5 RS; and that the ring current has a half-width of ˜1.5 RS. Two outcomes of this study are that the ring current bends northward, as suggested by the “bowl” model of Saturn's plasma sheet, and that the total ring current is 9.2 ± 1.0 MA. In the context of future endeavors, the statistical ring current presented here can be used for calculations of the magnetic field of Saturn for particle drifts, field line mapping, and J × B force.

  7. Fingering inside the coffee ring

    NASA Astrophysics Data System (ADS)

    Weon, Byung Mook; Je, Jung Ho

    2013-01-01

    Colloidal droplets including micro- and nanoparticles generally leave a ringlike stain, called the “coffee ring,” after evaporation. We show that fingering emerges during evaporation inside the coffee ring, resulting from a bidispersed colloidal mixture of micro- and nanoparticles. Microscopic observations suggest that finger formation is driven by competition between the coffee-ring and Marangoni effects, especially when the inward Marangoni flow is overwhelmed by the outward coffee-ring flow. This finding could help to understand the variety of the final deposition patterns of colloidal droplets.

  8. Perfectly Matched Layers versus discrete transparent boundary conditions in quantum device simulations

    SciTech Connect

    Mennemann, Jan-Frederik Jüngel, Ansgar

    2014-10-15

    Discrete transparent boundary conditions (DTBC) and the Perfectly Matched Layers (PML) method for the realization of open boundary conditions in quantum device simulations are compared, based on the stationary and time-dependent Schrödinger equation. The comparison includes scattering state, wave packet, and transient scattering state simulations in one and two space dimensions. The Schrödinger equation is discretized by a second-order Crank–Nicolson method in case of DTBC. For the discretization with PML, symmetric second-, fourth-, and sixth-order spatial approximations as well as Crank–Nicolson and classical Runge–Kutta time-integration methods are employed. In two space dimensions, a ring-shaped quantum waveguide device is simulated in the stationary and transient regime. As an application, a simulation of the Aharonov–Bohm effect in this device is performed, showing the excitation of bound states localized in the ring region. The numerical experiments show that the results obtained from PML are comparable to those obtained using DTBC, while keeping the high numerical efficiency and flexibility as well as the ease of implementation of the former method. -- Highlights: •In-depth comparison between discrete transparent boundary conditions (DTBC) and PML. •First 2-D transient scattering state simulations using DTBC. •First 2-D transient scattering state simulations of the Aharonov–Bohm effect.

  9. Rings Around the Pole

    NASA Image and Video Library

    2005-01-20

    Atmospheric features in Saturn's north polar region are revealed in spectacular detail in this Cassini image, taken in the near infrared spectral region, where methane gas is not very absorbing. The dark shadows of Saturn's rings drape across the planet, creating the illusion of atmospheric bands. Dots of bright clouds give the appearance that this is an active place. The image was taken with the Cassini spacecraft wide angle camera on Dec. 14, 2004, at a distance of 717,800 kilometers (446,100 miles) from Saturn through a filter sensitive to wavelengths of infrared light centered at 939 nanometers. The image scale is about 43 kilometers (27 miles) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA06567

  10. Black ring deconstruction

    SciTech Connect

    Gimon, Eric; Gimon, Eric G.; Levi, Thomas S.

    2007-06-22

    We present a sample microstate for a black ring in four and five dimensional language. The microstate consists of a black string microstate with an additional D6-brane. We show that with an appropriate choice of parameters the piece involving the black string microstate falls down a long AdS throat, whose M-theory lift is AdS_3 x S2. We wrap a spinning dipole M2-brane on the S2 in the probe approximation. In IIA, this corresponds to a dielectric D2-brane carrying only D0-charge. We conjecture this is the firstapproximation to a cloud of D0-branes blowing up due to their non-abelian degrees of freedom and the Myers effect.

  11. A familiar ring?

    SciTech Connect

    Camack, M.J.

    1995-05-01

    These days, the 1984 divestiture of the regional Bell operating companies from AT&T and the succeeding competitive struggles among long-distance companies and equipment providers seem to ring loud and clear for those in the electric power business. The similarities are compelling: Advancements in technology, the clamor of customers for choice, and other natural pressures in the marketplace challenge the traditional structure of a natural monopoly, creating an opening for competition. Voila, deregulation. To gain expertise from the divestiture experience, several electric utility companies have dialed up former telecommunications executives and managers for their insights, hiring them for key positions in senior management. Veterans of telecommunications have instructive views on the similarities, differences, and lessons learned, especially in the areas of marketing and customer focus.

  12. Ring around the colloid

    NASA Astrophysics Data System (ADS)

    Cavallaro, Marcello, Jr.; Gharbi, Mohamed A.; Beller, Daniel A.; Čopar, Simon; Shi, Zheng; Kamien, Randall D.; Yang, Shu; Baumgart, Tobias; Stebe, Kathleen J.

    In this work, we show that Janus washers, genus-one colloids with hybrid anchoring conditions, form topologically required defects in nematic liquid crystals. Experiments under crossed polarizers reveal the defect structure to be a rigid disclination loop confined within the colloid, with an accompanying defect in the liquid crystal. When confined to a homeotropic cell, the resulting colloid-defect ring pair tilts relative to the far field director, in contrast to the behavior of toroidal colloids with purely homeotropic anchoring. We show that this tilting behavior can be reversibly suppressed by the introduction of a spherical colloid into the center of the toroid, creating a new kind of multi-shape colloidal assemblage.

  13. A parametric study for the generation of ion Bernstein modes from a discrete spectrum to a continuous one in the inner magnetosphere. II. Particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Sun, Jicheng; Gao, Xinliang; Lu, Quanming; Chen, Lunjin; Tao, Xin; Wang, Shui

    2016-02-01

    In this paper, we perform one-dimensional particle-in-cell simulations to investigate the properties of perpendicular magnetosonic waves in a plasma system consisting of three components: cool electrons, cool protons, and tenuous ring distribution protons, where the waves are excited by the tenuous proton ring distribution. Consistent with the linear theory, the spectra of excited magnetosonic waves can change from discrete to continuous due to the overlapping of adjacent unstable wave modes. The increase of the proton to electron mass ratio, the ratio of the light speed to the Alfven speed, or the concentration of protons with a ring distribution tends to result in a continuous spectrum of magnetosonic waves, while the increase of the ring velocity of the tenuous proton ring distribution leads to a broader one, but with a discrete structure. Moreover, the energization of both cool electrons and protons and the scattering of ring distribution protons due to the excited magnetosonic waves are also observed in our simulations, which cannot be predicted by the linear theory. Besides, a thermalized proton ring distribution may lead to the further excitation of several lower discrete harmonics with their frequencies about several proton gyrofrequencies.

  14. The Saturn Ring Observer: In situ studies of planetary rings

    NASA Astrophysics Data System (ADS)

    Nicholson, P. D.; Tiscareno, M. S.; Spilker, L. J.

    2010-12-01

    As part of the Planetary Science Decadal Survey recently undertaken by the NRC's Space Studies Board for the National Academy of Sciences, studies were commissioned for a number of potential missions to outer planet targets. One of these studies examined the technological feasibility of a mission to carry out in situ studies of Saturn's rings, from a spacecraft placed in a circular orbit above the ring plane: the Saturn Ring Observer. The technical findings and background are discussed in a companion poster by T. R. Spilker et al. Here we outline the science goals of such a mission. Most of the fundamental interactions in planetary rings occur on spatial scales that are unresolved by flyby or orbiter spacecraft. Typical particle sizes in the rings of Saturn are in the 1 cm - 10 m range, and average interparticle spacings are a few meters. Indirect evidence indicates that the vertical thickness of the rings is as little as 5 - 10 m, which implies a velocity dispersion of only a few mm/sec. Theories of ring structure and evolution depend on the unknown characteristics of interparticle collisions and on the size distribution of the ring particles. The SRO could provide direct measurements of both the coefficient of restitution -- by monitoring individual collisions -- and the particles’ velocity dispersion. High-resolution observations of individual ring particles should also permit estimates of their spin states. Numerical simulations of Saturn’s rings incorporating both collisions and self-gravity predict that the ring particles are not uniformly distributed, but are instead clustered into elongated structures referred to as “self-gravity wakes”, which are continually created and destroyed on an orbital timescale. Theory indicates that the average separation between wakes in the A ring is of order 30-100 m. Direct imaging of self-gravity wakes, including their formation and subsequent dissolution, would provide critical validation of these models. Other

  15. Discrete dissipative localized modes in nonlinear magnetic metamaterials.

    PubMed

    Rosanov, Nikolay N; Vysotina, Nina V; Shatsev, Anatoly N; Shadrivov, Ilya V; Powell, David A; Kivshar, Yuri S

    2011-12-19

    We analyze the existence, stability, and propagation of dissipative discrete localized modes in one- and two-dimensional nonlinear lattices composed of weakly coupled split-ring resonators (SRRs) excited by an external electromagnetic field. We employ the near-field interaction approach for describing quasi-static electric and magnetic interaction between the resonators, and demonstrate the crucial importance of the electric coupling, which can completely reverse the sign of the overall interaction between the resonators. We derive the effective nonlinear model and analyze the properties of nonlinear localized modes excited in one-and two-dimensional lattices. In particular, we study nonlinear magnetic domain walls (the so-called switching waves) separating two different states of nonlinear magnetization, and reveal the bistable dependence of the domain wall velocity on the external field. Then, we study two-dimensional localized modes in nonlinear lattices of SRRs and demonstrate that larger domains may experience modulational instability and splitting.

  16. Status of NSLS-II Storage Ring Vacuum Systems

    SciTech Connect

    Doom,L.; Hseuh,H.; Ferreira, M.; Longo, C.; Ravindranath, V.; Settepani, P.; Sharma, S.; Wilson, K.

    2009-05-04

    National Synchrotron Light Source II (NSLS-II), being constructed at Brookhaven National Laboratory, is a 3-GeV, high-flux and high- brightness synchrotron radiation facility with a nominal current of 500 mA. The storage ring vacuum system will have extruded aluminium chambers with ante-chamber for photon fans and distributed NEG strip pumping. Discrete photon absorbers will be used to intercept the un-used bending magnet radiation. In-situ bakeout will be implemented to achieve fast conditioning during initial commissioning and after interventions.

  17. Hamiltonian theory of nonlinear waves in planetary rings

    NASA Technical Reports Server (NTRS)

    Stewart, G. R.

    1987-01-01

    The derivation of a Hamiltonian field theory for nonlinear density waves in Saturn's rings is discussed. Starting with a Hamiltonian for a discrete system of gravitating streamlines, an averaged Hamiltonian is obtained by successive applications of Lie transforms. The transformation may be carried out to any desired order in q, where q is the nonlinearity parameter defined in the work of Shu, et al (1985) and Borderies et al (1985). Subsequent application of the Wentzel-Kramer-Brillouin Method approximation yields an asymptotic field Hamiltonian. Both the nonlinear dispersion relation and the wave action transport equation are easily derived from the corresponding Lagrangian by the standard variational principle.

  18. Ideal shrinking and expansion of discrete sequences

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.

    1986-01-01

    Ideal methods are described for shrinking or expanding a discrete sequence, image, or image sequence. The methods are ideal in the sense that they preserve the frequency spectrum of the input up to the Nyquist limit of the input or output, whichever is smaller. Fast implementations that make use of the discrete Fourier transform or the discrete Hartley transform are described. The techniques lead to a new multiresolution image pyramid.

  19. How Jupiter's Ring Was Discovered.

    ERIC Educational Resources Information Center

    Elliot, James; Kerr, Richard

    1985-01-01

    "Rings" (by astronomer James Elliot and science writer Richard Kerr) is a nontechnical book about the discovery and exploration of ring systems from the time of Galileo to the era of the Voyager spacecraft. One of this book's chapters is presented. (JN)

  20. Uranus Rings in False Color

    NASA Image and Video Library

    1996-01-29

    This false-color view of the rings of Uranus was made from images taken by NASA Voyager 2 on Jan. 21, 1986. All nine known rings are visible here; the somewhat fainter, pastel lines seen between them are contributed by the computer enhancement. http://photojournal.jpl.nasa.gov/catalog/PIA00033

  1. Nardò Ring, Italy

    NASA Image and Video Library

    2008-04-08

    The Nardò Ring is a striking visual feature from space, and astronauts have photographed it several times. The Ring is a race car test track in Italy. This image was acquired by NASA Terra satellite on August 17. 2007.

  2. Running Rings Around the Web.

    ERIC Educational Resources Information Center

    McDermott, Irene E.

    1999-01-01

    Describes the development and current status of WebRing, a service that links related Web sites into a central hub. Discusses it as a viable alternative to other search engines and examines issues of free speech, use by the business sector, and implications for WebRing after its purchase by Yahoo! (LRW)

  3. Reversible Seeding in Storage Rings

    SciTech Connect

    Ratner, Daniel; Chao, Alex; /SLAC

    2011-12-14

    We propose to generate steady-state microbunching in a storage ring with a reversible seeding scheme. High gain harmonic generation (HGHG) and echo-enabled harmonic generation (EEHG) are two promising methods for microbunching linac electron beams. Because both schemes increase the energy spread of the seeded beam, they cannot drive a coherent radiator turn-by-turn in a storage ring. However, reversing the seeding process following the radiator minimizes the impact on the electron beam and may allow coherent radiation at or near the storage ring repetition rate. In this paper we describe the general idea and outline a proof-of-principle experiment. Electron storage rings can drive high average power light sources, and free-electron lasers (FELs) are now producing coherent light sources of unprecedented peak brightness While there is active research towards high repetition rate FELs (for example, using energy recovery linacs), at present there are still no convenient accelerator-based sources of high repetition rate, coherent radiation. As an alternative avenue, we recently proposed to establish steady-state microbunching (SSMB) in a storage ring. By maintaining steady-state coherent microbunching at one point in the storage ring, the beam generates coherent radiation at or close to the repetition rate of the storage ring. In this paper, we propose a method of generating a microbunched beam in a storage ring by using reversible versions of linac seeding schemes.

  4. How Jupiter's Ring Was Discovered.

    ERIC Educational Resources Information Center

    Elliot, James; Kerr, Richard

    1985-01-01

    "Rings" (by astronomer James Elliot and science writer Richard Kerr) is a nontechnical book about the discovery and exploration of ring systems from the time of Galileo to the era of the Voyager spacecraft. One of this book's chapters is presented. (JN)

  5. Contraceptive vaginal rings: a review.

    PubMed

    Brache, Vivian; Faundes, Anibal

    2010-11-01

    Development efforts on contraceptive vaginal rings were initiated over 40 years ago based on two principles: the capacity of the vaginal epithelium to absorb steroids and the capacity of elastomers to release these hormones at a nearly constant rate. Numerous models of contraceptive vaginal rings (CVRs) have been studied, but only two have reached the market: NuvaRing, a combined ring that releases etonogestrel (ENG) and ethinylestradiol (EE), and Progering, a progesterone-releasing ring for use in lactating women. The main advantages of CVRs are their effectiveness (similar to or slightly better than the pill), ease of use without the need of remembering a daily routine, user's ability to control initiation and discontinuation, nearly constant release rate allowing for lower doses, greater bioavailability and good cycle control with the combined ring. The main disadvantages are related to the mode of delivery; CVRs may cause vaginal discharge and complaints, ring expulsion is not uncommon, the ring may be felt during coitus and vaginal insertion may be unpleasant for some women. The studies reviewed in this article provide evidence that CVRs are safe, effective and highly acceptable to women. There is no doubt that CVRs offer a new, effective contraceptive option to women, expanding their available choices of hormonal contraception. Copyright © 2010 Elsevier Inc. All rights reserved.

  6. Ring Infiltrate in Staphylococcal Keratitis

    PubMed Central

    Wallang, Batriti S.; Sharma, Savitri; Sahu, Srikant K.; Mittal, Ruchi

    2013-01-01

    Smear and culture tests of corneal scrapings from a patient with a ring infiltrate confirmed significant growth of a Staphylococcus species resistant to fluoroquinolones. Because of nonresponse to medical management, the patient underwent therapeutic penetrating keratoplasty. Staphylococcal infection of the cornea may appear as a ring-like infiltrate that is recalcitrant to medical management. PMID:23100354

  7. Biomechanics of Corneal Ring Implants

    PubMed Central

    2015-01-01

    Purpose: To evaluate the biomechanics of corneal ring implants by providing a related mathematical theory and biomechanical model for the treatment of myopia and keratoconus. Methods: The spherical dome model considers the inhomogeneity of the tunica of the eye, dimensions of the cornea, lamellar structure of the corneal stroma, and asphericity of the cornea. It is used in this study for calculating a strengthening factor sf for the characterization of different ring-shaped corneal implant designs. The strengthening factor is a measure of the amount of strengthening of the cornea induced by the implant. Results: For ring segments and incomplete rings, sf = 1.0, which indicates that these implants are not able to strengthen the cornea. The intracorneal continuous complete ring (MyoRing) has a strengthening factor of up to sf = 3.2. The MyoRing is, therefore, able to strengthen the cornea significantly. Conclusions: The result of the presented biomechanical analysis of different ring-shaped corneal implant designs can explain the different postoperative clinical results of different implant types in myopia and keratoconus. PMID:26312619

  8. Rings Full of Waves (zoom)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image shows a close-up view of a density wave in Saturn's A ring. It was taken by the narrow angle camera on the Cassini spacecraft after successful entry into Saturn's orbit. The view shows the dark, or unlit, side of the rings.

  9. Fibre ring cavity semiconductor laser

    SciTech Connect

    Duraev, V P; Medvedev, S V

    2013-10-31

    This paper presents a study of semiconductor lasers having a polarisation maintaining fibre ring cavity. We examine the operating principle and report main characteristics of a semiconductor ring laser, in particular in single- and multiple-frequency regimes, and discuss its application areas. (lasers)

  10. Simulating the Smallest Ring World of Chariklo

    NASA Astrophysics Data System (ADS)

    Michikoshi, Shugo; Kokubo, Eiichiro

    2017-03-01

    A ring system consisting of two dense narrow rings has been discovered around Centaur Chariklo. The existence of these rings around a small object poses various questions about their origin, stability, and lifetime. In order to understand the nature of Chariklo’s rings, we perform global N-body simulations of the self-gravitating collisional particle rings for the first time. We find that Chariklo should be denser than the ring material in order to avoid the rapid diffusion of the rings. If Chariklo is denser than the ring material, fine spiral structures called self-gravity wakes occur in the inner ring. These wakes accelerate the viscous spreading of the ring significantly and typically occur on timescales of about 100 {years} for m-sized ring particles, which is considerably shorter than the timescales suggested in previous studies. The existence of these narrow rings implies smaller ring particles or the existence of shepherding satellites.

  11. Discrete modelling of drapery systems

    NASA Astrophysics Data System (ADS)

    Thoeni, Klaus; Giacomini, Anna

    2016-04-01

    Drapery systems are an efficient and cost-effective measure in preventing and controlling rockfall hazards on rock slopes. The simplest form consists of a row of ground anchors along the top of the slope connected to a horizontal support cable from which a wire mesh is suspended down the face of the slope. Such systems are generally referred to as simple or unsecured draperies (Badger and Duffy 2012). Variations such as secured draperies, where a pattern of ground anchors is incorporated within the field of the mesh, and hybrid systems, where the upper part of an unsecured drapery is elevated to intercept rockfalls originating upslope of the installation, are becoming more and more popular. This work presents a discrete element framework for simulation of unsecured drapery systems and its variations. The numerical model is based on the classical discrete element method (DEM) and implemented into the open-source framework YADE (Šmilauer et al., 2010). The model takes all relevant interactions between block, drapery and slope into account (Thoeni et al., 2014) and was calibrated and validated based on full-scale experiments (Giacomini et al., 2012).The block is modelled as a rigid clump made of spherical particles which allows any shape to be approximated. The drapery is represented by a set of spherical particle with remote interactions. The behaviour of the remote interactions is governed by the constitutive behaviour of the wire and generally corresponds to a piecewise linear stress-strain relation (Thoeni et al., 2013). The same concept is used to model wire ropes. The rock slope is represented by rigid triangular elements where material properties (e.g., normal coefficient of restitution, friction angle) are assigned to each triangle. The capabilities of the developed model to simulate drapery systems and estimate the residual hazard involved with such systems is shown. References Badger, T.C., Duffy, J.D. (2012) Drapery systems. In: Turner, A.K., Schuster R

  12. Structure of random discrete spacetime

    NASA Technical Reports Server (NTRS)

    Brightwell, Graham; Gregory, Ruth

    1991-01-01

    The usual picture of spacetime consists of a continuous manifold, together with a metric of Lorentzian signature which imposes a causal structure on the spacetime. A model, first suggested by Bombelli et al., is considered in which spacetime consists of a discrete set of points taken at random from a manifold, with only the causal structure on this set remaining. This structure constitutes a partially ordered set (or poset). Working from the poset alone, it is shown how to construct a metric on the space which closely approximates the metric on the original spacetime manifold, how to define the effective dimension of the spacetime, and how such quantities may depend on the scale of measurement. Possible desirable features of the model are discussed.

  13. Discrete breathers in hydrogenated graphene

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Baimova, Julia A.; Dmitriev, Sergey V.; Wang, Xu; Zhu, Hongwei; Zhou, Kun

    2013-07-01

    Discrete breathers (DBs) in graphane (fully hydrogenated graphene) are investigated using molecular dynamics simulations. It is found that the DB can be excited by applying an out-of-plane displacement on a single hydrogen atom of graphane. The vibration frequency of the DB lies either within the gap of the phonon spectrum of graphane or beyond its upper spectrum bound. Both soft and hard types of anharmonicity of the DB, which have not been found in the same system, are observed in graphane. The study shows that the DB is robust and its lifetime is affected by various factors including its anharmonicity type, its amplitude and frequency, and the force on the hydrogen atom that forms it, whose competition results in a complex mechanism for the lifetime determination. The investigation of the maximum kinetic energy of DBs reveals that they may function to activate or accelerate dehydrogenation of hydrogenated graphene at high temperatures.

  14. Structure of random discrete spacetime

    NASA Technical Reports Server (NTRS)

    Brightwell, Graham; Gregory, Ruth

    1991-01-01

    The usual picture of spacetime consists of a continuous manifold, together with a metric of Lorentzian signature which imposes a causal structure on the spacetime. A model, first suggested by Bombelli et al., is considered in which spacetime consists of a discrete set of points taken at random from a manifold, with only the causal structure on this set remaining. This structure constitutes a partially ordered set (or poset). Working from the poset alone, it is shown how to construct a metric on the space which closely approximates the metric on the original spacetime manifold, how to define the effective dimension of the spacetime, and how such quantities may depend on the scale of measurement. Possible desirable features of the model are discussed.

  15. Scalar discrete nonlinear multipoint boundary value problems

    NASA Astrophysics Data System (ADS)

    Rodriguez, Jesus; Taylor, Padraic

    2007-06-01

    In this paper we provide sufficient conditions for the existence of solutions to scalar discrete nonlinear multipoint boundary value problems. By allowing more general boundary conditions and by imposing less restrictions on the nonlinearities, we obtain results that extend previous work in the area of discrete boundary value problems [Debra L. Etheridge, Jesus Rodriguez, Periodic solutions of nonlinear discrete-time systems, Appl. Anal. 62 (1996) 119-137; Debra L. Etheridge, Jesus Rodriguez, Scalar discrete nonlinear two-point boundary value problems, J. Difference Equ. Appl. 4 (1998) 127-144].

  16. A discrete event method for wave simulation

    SciTech Connect

    Nutaro, James J

    2006-01-01

    This article describes a discrete event interpretation of the finite difference time domain (FDTD) and digital wave guide network (DWN) wave simulation schemes. The discrete event method is formalized using the discrete event system specification (DEVS). The scheme is shown to have errors that are proportional to the resolution of the spatial grid. A numerical example demonstrates the relative efficiency of the scheme with respect to FDTD and DWN schemes. The potential for the discrete event scheme to reduce numerical dispersion and attenuation errors is discussed.

  17. Discrete gauge symmetry in continuum theories

    SciTech Connect

    Krauss, L.M.; Wilczek, F.

    1989-03-13

    We point out that local symmetries can masquerade as discrete global symmetries to an observer equipped with only low-energy probes. The existence of the underlying local gauge invariance can, however, result in observable Aharonov-Bohm-type effects. Black holes can therefore carry discrete gauge charges: a form of nonclassical ''hair.'' Neither black-hole evaporation, wormholes, nor anything else can violate discrete gauge symmetries. In supersymmetric unified theories such discrete symmetries can forbid proton-decay amplitudes that might otherwise be catastrophic.

  18. The Search for Ringed Exoplanets

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-04-01

    Are planetary rings as common in our galaxy as they are in our solar system? A new study demonstrates how we might search for ringed exoplanets and then possibly finds one!Saturns Elsewhere?Artists illustration of the super ring system around exoplanet J1407b. This is the only exoplanet weve found with rings, but its not at all like Saturn. [Ron Miller]Our solar system is filled with moons and planetary rings, so it stands to reason that exoplanetary systems should exhibit the same features. But though weve been in the planet-hunting game for decades, weve only found one exoplanet thats surrounded by a ring system. Whats more, that system J1407b has enormous rings that are vastly different from the modest, Saturn-like rings that we might expect to be more commonplace.Have we not discovered ringed exoplanets just because theyre hard to identify? Or is it because theyre not out there? A team of scientists led by Masataka Aizawa (University of Tokyo) has set out to answer this question by conducting a systematic search for rings around long-period planet candidates.The transit light curve of KIC 10403228, shown with three models: the best-fitting planet-only model (blue) and the two best-fitting planet+ring models (green and red). [Aizawa et al. 2017]The Hunt BeginsWhy long-period planets? Rings are expected to be unstable as the planet gets closer to the central star. Whats more, the planet needs to be far enough away from the stars warmth for the icy rings to exist. The authors therefore select from the collection of candidate transiting planets 89 long-period candidates that might be able to host rings.Aizawa and collaborators then fit single-planet models (with no rings) to the light curves of these planets and search for anomalies curves that arent fit well by these standard models. Particularly suspicious characteristics include a long ingress/egress as the planet moves across the face of the star, and asymmetry of the transit shape.After applying a series of

  19. Advances in microbicide vaginal rings.

    PubMed

    Malcolm, R Karl; Edwards, Karen-Leigh; Kiser, Patrick; Romano, Joseph; Smith, Thomas J

    2010-12-01

    Vaginal ring devices capable of providing sustained/controlled release of incorporated actives are already marketed for steroidal contraception and estrogen replacement therapy. In recent years, there has been considerable interest in developing similar ring devices for the administration of microbicidal compounds to prevent vaginal HIV transmission. Intended to be worn continuously, such coitally independent microbicide rings are being developed to maintain effective vaginal microbicide concentrations over many weeks or months, thereby overcoming issues around timing of product application, user compliance and acceptability associated with more conventional semi-solid formulations. In this article, an overview of vaginal ring technologies is presented, followed by a review of recent advances and issues pertaining to their application for the delivery of HIV microbicides. This article forms part of a special supplement on presentations covering intravaginal rings, based on the symposium "Trends in Microbicide Formulations", held on 25 and 26 January 2010, Arlington, VA. Copyright © 2010 Elsevier B.V. All rights reserved.

  20. Modeling of Electromagnetic Scattering by Discrete and Discretely Heterogeneous Random Media by Using Numerically Exact Solutions of the Maxwell Equations

    NASA Astrophysics Data System (ADS)

    Dlugach, J. M.; Mishchenko, M. I.

    2017-07-01

    In this paper, we discuss some aspects of numerical modeling of electromagnetic scattering by discrete random medium by using numerically exact solutions of the macroscopic Maxwell equations. Typical examples of such media are clouds of interstellar dust, clouds of interplanetary dust in the Solar system, dusty atmospheres of comets, particulate planetary rings, clouds in planetary atmospheres, aerosol particles with numerous inclusions and so on. Our study is based on the results of extensive computations of different characteristics of electromagnetic scattering obtained by using the superposition T-matrix method which represents a direct computer solver of the macroscopic Maxwell equations for an arbitrary multisphere configuration. As a result, in particular, we clarify the range of applicability of the low-density theories of radiative transfer and coherent backscattering as well as of widely used effective-medium approximations.

  1. Modeling of Electromagnetic Scattering by Discrete and Discretely Heterogeneous Random Media by Using Numerically Exact Solutions of the Maxwell Equations

    NASA Technical Reports Server (NTRS)

    Dlugach, Janna M.; Mishchenko, Michael I.

    2017-01-01

    In this paper, we discuss some aspects of numerical modeling of electromagnetic scattering by discrete random medium by using numerically exact solutions of the macroscopic Maxwell equations. Typical examples of such media are clouds of interstellar dust, clouds of interplanetary dust in the Solar system, dusty atmospheres of comets, particulate planetary rings, clouds in planetary atmospheres, aerosol particles with numerous inclusions and so on. Our study is based on the results of extensive computations of different characteristics of electromagnetic scattering obtained by using the superposition T-matrix method which represents a direct computer solver of the macroscopic Maxwell equations for an arbitrary multisphere configuration. As a result, in particular, we clarify the range of applicability of the low-density theories of radiative transfer and coherent backscattering as well as of widely used effective-medium approximations.

  2. Anticipating the Filtrons of Automata by Complex Discrete Systems Analysis

    NASA Astrophysics Data System (ADS)

    Siwak, Pawel

    2002-09-01

    Filtrons of automata are coherent structures (discrete solitons) supported by iterated automata maps (IAMs). They differ from signals of cellular automata. The signals emerge during parallel processing of strings, while IAMs transform strings in serial. We relate the filtron and its supporting automaton with a particular complex discrete system (CDS). This CDS has the form of a processing ring net. Its computation is characterized by four components: instructions of processing nodes (I), inter-processor communication constraints (C), initial data (D), and synchronization (S). We present an analysis of a computation performed within this CDS. It is useful in the problems of searching for any of the mentioned four components assuming that remaining three are known. We give a technique of anticipating the filtrons with a desired parameter C when I, S and D are given. We show how to decide the synchronization S when I, C and D are assumed, and how to determine instructions I when the desired filtron is described by known C, D and S.

  3. Calculus and design of discrete velocity models using computer algebra

    NASA Astrophysics Data System (ADS)

    Babovsky, Hans; Grabmeier, Johannes

    2016-11-01

    In [2, 3], a framework for a calculus with Discrete Velocity Models (DVM) has been derived. The rotatonal symmetry of the discrete velocities can be modelled algebraically by the action of the cyclic group C4 - or including reflections of the dihedral group D4. Taking this point of view, the linearized collision operator can be represented in a compact form as a matrix of elements in the group algebra. Or in other words, by choosing a special numbering it exhibits a certain block structure which lets it appear as a matrix with entries in a certain polynomial ring. A convenient way for approaching such a structure is the use of a computer algebra system able to treat these (predefined) algebraic structures. We used the computer algebra system FriCAS/AXIOM [4, 5] for the generation of the velocity and the collision sets and for the analysis of the structure of the collision operator. Concerning the fluid dynamic limit, the system provides the characterization of sets of collisions and their contribution to the flow parameters. It allows the design of rotationally invariant symmetric models for prescribed Prandtl numbers. The implementation in FriCAS/AXIOM is explained and its results for a 25-velocity model are presented.

  4. Black hole ringing, quasinormal modes, and light rings

    NASA Astrophysics Data System (ADS)

    Khanna, Gaurav; Price, Richard H.

    2017-04-01

    Modeling of gravitational waves from binary black hole inspiral has played an important role in the recent observations of such signals. The late-stage ringdown phase of the gravitational waveform is often associated with the null particle orbit ("light ring") of the black hole spacetime. With simple models we show that this link between the light ring and spacetime ringing is based more on the history of specific models than on an actual constraining relationship. We also show, in particular, that a better understanding of the dissociation of the two may be relevant to the astrophysically interesting case of rotating (Kerr) black holes.

  5. Stability analysis of a discrete Hutchinson equation with discrete and distributed delay

    NASA Astrophysics Data System (ADS)

    Suryanto, A.; Yanti, I.; Kusumawinahyu, W. M.

    2014-02-01

    In this paper a Hutchinson equation with discrete and distributed delay is discretized by the Euler method. The dynamics of the obtained discrete system is then investigated. Specifically the stability of the positive fixed point is analyzed. It is found that for sufficiently small time-step of integration, the positive equilibrium undergoes a Neimark-Sacker bifurcation which is controlled by the discrete time delay. The results of analysis are then confirmed by some numerical simulations.

  6. Dione Before the Rings

    NASA Image and Video Library

    2015-11-23

    Saturn's rings are so expansive that they often sneak into Cassini's pictures of other bodies. Here, they appear with the planet in a picture taken during a close flyby of Dione. The flyby of Dione (698 miles or 1123 kilometers across) during which this image was taken was the last close encounter with this moon during Cassini's mission. The main goal of the flyby was to use the spacecraft as a probe to measure Dione's gravity field. However, scientists also managed to take some very close images of the surface. All of the data will be helpful to understand the interior structure and geological history of this distant, icy world. This view is centered on terrain at 7 degrees south latitude, 122 degrees west longitude. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 17, 2015. The view was obtained at a distance of approximately 48,000 miles (77,000 kilometers) from Dione and at a Sun-Dione-spacecraft, or phase angle of 35 degrees. Image scale is 1,520 feet (464 meters) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18344

  7. Ring Buffered Network Bus

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This report describes the research effort to demonstrate the integration of a data sharing technology, Ring Buffered Network Bus, in development by Dryden Flight Research Center, with an engine simulation application, the Java Gas Turbine Simulator, in development at the University of Toledo under a grant from the Glenn Research Center. The objective of this task was to examine the application of the RBNB technologies as a key component in the data sharing, health monitoring and system wide modeling elements of the NASA Aviation Safety Program (AVSP) [Golding, 1997]. System-wide monitoring and modeling of aircraft and air safety systems will require access to all data sources which are relative factors when monitoring or modeling the national airspace such as radar, weather, aircraft performance, engine performance, schedule and planning, airport configuration, flight operations, etc. The data sharing portion of the overall AVSP program is responsible for providing the hardware and software architecture to access and distribute data, including real-time flight operations data, among all of the AVSP elements. The integration of an engine code capable of numerically "flying" through recorded flight paths and weather data using a software tool that allows for distributed access of data to this engine code demonstrates initial steps toward building a system capable of monitoring and modeling the National Airspace.

  8. Percolation assisted excitation transport in discrete-time quantum walks

    NASA Astrophysics Data System (ADS)

    Štefaňák, M.; Novotný, J.; Jex, I.

    2016-02-01

    Coherent transport of excitations along chains of coupled quantum systems represents an interesting problem with a number of applications ranging from quantum optics to solar cell technology. A convenient tool for studying such processes are quantum walks. They allow us to determine all the process features in a quantitative way. We study the survival probability and the transport efficiency on a simple, highly symmetric graph represented by a ring. The propagation of excitation is modeled by a discrete-time (coined) quantum walk. For a two-state quantum walk, where the excitation (walker) has to leave its actual position to the neighboring sites, the survival probability decays exponentially and the transport efficiency is unity. The decay rate of the survival probability can be estimated using the leading eigenvalue of the evolution operator. However, if the excitation is allowed to stay at its present position, i.e. the propagation is modeled by a lazy quantum walk, then part of the wave-packet can be trapped in the vicinity of the origin and never reaches the sink. In such a case, the survival probability does not vanish and the excitation transport is not efficient. The dependency of the transport efficiency on the initial state is determined. Nevertheless, we show that for some lazy quantum walks dynamical, percolations of the ring eliminate the trapping effect and efficient excitation transport can be achieved.

  9. Ion Rings for Magnetic Fusion

    SciTech Connect

    Greenly, John, B.

    2005-07-31

    This Final Technical Report presents the results of the program, Ion Rings for Magnetic Fusion, which was carried out under Department of Energy funding during the period August, 1993 to January, 2005. The central objective of the program was to study the properties of field-reversed configurations formed by ion rings. In order to reach this objective, our experimental program, called the Field-reversed Ion Ring Experiment, FIREX, undertook to develop an efficient, economical technology for the production of field-reversed ion rings. A field-reversed configuration (FRC) in which the azimuthal (field-reversing) current is carried by ions with gyro-radius comparable to the magnetic separatrix radius is called a field-reversed ion ring. A background plasma is required for charge neutralization of the ring, and this plasma will be confined within the ring's closed magnetic flux. Ion rings have long been of interest as the basis of compact magnetic fusion reactors, as the basis for a high-power accelerator for an inertial fusion driver, and for other applications of high power ion beams or plasmas of high energy density. Specifically, the FIREX program was intended to address the longstanding question of the contribution of large-orbit ions to the observed stability of experimental FRCs to the MHD tilt mode. Typical experimental FRCs with s {approx} 2-4, where s is the ratio of separatrix radius to ion gyro-radius, have been stable to tilting, but desired values for a fusion reactor, s > 20, should be unstable. The FIREX ring would consist of a plasma with large s for the background ions, but with s {approx} 1 for the ring ions. By varying the proportions of these two populations, the minimum proportion of large-orbit ions necessary for stability could be determined. The incorporation of large-orbit ions, perhaps by neutral-beam injection, into an FRC has been advanced for the purpose of stabilizing, heating, controlling angular momentum, and aiding the formation of a

  10. Genetics Home Reference: ring chromosome 20 syndrome

    MedlinePlus

    ... Home Health Conditions ring chromosome 20 syndrome ring chromosome 20 syndrome Printable PDF Open All Close All ... to view the expand/collapse boxes. Description Ring chromosome 20 syndrome is a condition that affects the ...

  11. Galactic Behavior for the Outer B Ring

    NASA Image and Video Library

    2010-11-01

    Keeping a close watch on the outer portion of Saturn B ring, NASA Cassini spacecraft records the complex inward and outward movement of the edge of the ring. This ring movement resembles the suspected behavior of spiral disk galaxies.

  12. Particle properties and processes in Uranus' rings

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.; Brahic, A.; Burns, J. A.; Marouf, Essam A.

    1991-01-01

    The particle properties and processes in the Uranian rings are analyzed from Voyager observations and ground-based data. Occultation observations of the epsilon ring are interpreted to yield an effective size of the ring particles that exceeds 70 cm, a surface mass density that exceeds 80 g/sq cm, and a ring vertical thickness greater than tens of meters for solid ice particles. The particles forming the classic rings are dark and gray, with albedo of 0.014 +/-0.004. It is argued that the small amount of dust that exists in the classical rings and between the rings in bands is created by erosion of ring particles and unseen satellites resulting from collisions and micrometeoroid bombardment. As proposed for regions of the other known ring systems, new ring material can be continually created by the destruction of small moons near the rings, which may explain the youthful appearance of the Uranian rings.

  13. Modeling piston-ring dynamics, blowby, and ring-twist effects

    SciTech Connect

    Tian, T.; Noordzij, L.B.; Wong, V.W.; Heywood, J.B.

    1996-12-31

    A ring-dynamics and gas-flow model has been developed to study ring/groove contact, blowby, and the influence of ring static twist, keystone ring/groove configurations, and other piston and ring parameters. The model is developed for a ring pack with three rings. The dynamics of the top two rings and the gas pressures in the regions above the oil control ring are simulated. Distributions of oil film thickness and surface roughness on the groove and ring surfaces are assumed in the model to calculate the forces generated by the ring/groove contact. Ring static and dynamic twists are considered as well as different keystone ring/groove configurations. Ring dynamics and gas flows are coupled in the formulation and an implicit scheme is implemented, enabling the model to resolve detailed events such as ring flutter. Studies on a spark ignition engine found that static twist or, more generally speaking, the relative angle between rings and their grooves, has great influence on ring/groove contact characteristics, ring stability, and blowby. Ring flutter is found to occur for the second ring with a negative static twist under normal operating conditions and for the top ring with a negative static twist under high-speed/low-load operating conditions. Studies on a diesel engine show that different keystone ring/groove configurations result in different twist behaviors of the ring that may affect the wear pattern of the keystone ring running surfaces.

  14. Discretization vs. Rounding Error in Euler's Method

    ERIC Educational Resources Information Center

    Borges, Carlos F.

    2011-01-01

    Euler's method for solving initial value problems is an excellent vehicle for observing the relationship between discretization error and rounding error in numerical computation. Reductions in stepsize, in order to decrease discretization error, necessarily increase the number of steps and so introduce additional rounding error. The problem is…

  15. Interface discrete light bullets in waveguide arrays.

    PubMed

    Mihalache, Dumitru; Mazilu, Dumitru; Lederer, Falk; Kivshar, Yuri S

    2007-08-01

    We analyze spatiotemporal light localization at the interface separating two different periodic photonic lattices. We demonstrate the existence of a novel class of continuous-discrete spatiotemporal solitons propagating along the interface, including hybrid staggered-unstaggered discrete light bullets with tails belonging to spectral gaps of different types.

  16. Current Density and Continuity in Discretized Models

    ERIC Educational Resources Information Center

    Boykin, Timothy B.; Luisier, Mathieu; Klimeck, Gerhard

    2010-01-01

    Discrete approaches have long been used in numerical modelling of physical systems in both research and teaching. Discrete versions of the Schrodinger equation employing either one or several basis functions per mesh point are often used by senior undergraduates and beginning graduate students in computational physics projects. In studying…

  17. Conservative discretization of the Landau collision integral

    DOE PAGES

    Hirvijoki, E.; Adams, M. F.

    2017-03-28

    Here we describe a density, momentum-, and energy-conserving discretization of the nonlinear Landau collision integral. The method is suitable for both the finite-element and discontinuous Galerkin methods and does not require structured meshes. The conservation laws for the discretization are proven algebraically and demonstrated numerically for an axially symmetric nonlinear relaxation problem using a finite-element implementation.

  18. Current Density and Continuity in Discretized Models

    ERIC Educational Resources Information Center

    Boykin, Timothy B.; Luisier, Mathieu; Klimeck, Gerhard

    2010-01-01

    Discrete approaches have long been used in numerical modelling of physical systems in both research and teaching. Discrete versions of the Schrodinger equation employing either one or several basis functions per mesh point are often used by senior undergraduates and beginning graduate students in computational physics projects. In studying…

  19. Discretization vs. Rounding Error in Euler's Method

    ERIC Educational Resources Information Center

    Borges, Carlos F.

    2011-01-01

    Euler's method for solving initial value problems is an excellent vehicle for observing the relationship between discretization error and rounding error in numerical computation. Reductions in stepsize, in order to decrease discretization error, necessarily increase the number of steps and so introduce additional rounding error. The problem is…

  20. Quantifying Discretization Effects on Brain Trauma Simulations

    DTIC Science & Technology

    2016-01-01

    analyzed in each case were the variations in stress magnitude, spatial distribution, and wave patterns that arise inside the brain. The effects of...ARL-CR-0792 ● JAN 2016 US Army Research Laboratory Quantifying Discretization Effects on Brain Trauma Simulations prepared by...originator. ARL-CR-0792● JAN 2016 US Army Research Laboratory Quantifying Discretization Effects on Brain Trauma Simulations

  1. Ring-Ringlet Interactions in Saturn's C Ring

    NASA Technical Reports Server (NTRS)

    Rappaport, N. J.

    1997-01-01

    The overall obejective of this work is to derive a theoretical model for the formation of gaps harboring isolated ringlets in order to explain the presence of such features in Saturn's C ring and Cassini division.

  2. Reflex ring laser amplifier system

    DOEpatents

    Summers, Mark A.

    1985-01-01

    A laser pulse is injected into an unstable ring resonator-amplifier structure. Inside this resonator the laser pulse is amplified, spatially filtered and magnified. The laser pulse is recirculated in the resonator, being amplified, filtered and magnified on each pass. The magnification is chosen so that the beam passes through the amplifier in concentric non-overlapping regions similar to a single pass MOPA. After a number of passes around the ring resonator the laser pulse is spatially large enough to exit the ring resonator system by passing around an output mirror.

  3. Researches on the Piston Ring

    NASA Technical Reports Server (NTRS)

    Ehihara, Keikiti

    1944-01-01

    In internal combustion engines, steam engines, air compressors, and so forth, the piston ring plays an important role. Especially, the recent development of Diesel engines which require a high compression pressure for their working, makes, nowadays, the packing action of the piston ring far more important than ever. Though a number of papers have been published in regard to researches on the problem of the piston ring, none has yet dealt with an exact measurement of pressure exerted on the cylinder wall at any given point of the ring. The only paper that can be traced on this subject so far is Mr. Nakagawa's report on the determination of the relative distribution of pressure on the cylinder wall, but the measuring method adopted therein appears to need further consideration. No exact idea has yet been obtained as to how the obturation of gas between the piston and cylinder, the frictional resistance of the piston, and the wear of the cylinder wall are affected by the intensity and the distribution of the radial pressure of the piston ring. Consequently, the author has endeavored, by employing an apparatus of his own invention, to get an exact determination of the pressure distribution of the piston ring. By means of a newly devised ring tester, to which piezoelectricity of quartz was applied, the distribution of the radial pressure of many sample rings on the market was accurately determined. Since many famous piston rings show very irregular pressure distribution, the author investigated and achieved a manufacturing process of the piston ring which will exert uniform pressure on the cylinder wall. Temperature effects on the configuration and on the mean spring power have also been studied. Further, the tests were performed to ascertain how the gas tightness of the piston ring may be affected by the number or spring power. The researches as to the frictional resistance between the piston ring and the cylinder wall were carried out, too. The procedure of study, and

  4. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059478 (10 July 2014) --- In the International Space Station's Kibo laboratory, European Space Agency astronaut Alexander Gerst (left) and NASA astronaut Reid Wiseman, both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  5. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059467 (10 July 2014) --- In the International Space Station's Kibo laboratory, European Space Agency astronaut Alexander Gerst and NASA astronaut Reid Wiseman (mostly obscured), both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  6. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059344 (10 July 2014) --- In the International Space Station’s Kibo laboratory, NASA astronaut Reid Wiseman (left) and European Space Agency astronaut Alexander Gerst, both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  7. Generalized exponential function and discrete growth models

    NASA Astrophysics Data System (ADS)

    Souto Martinez, Alexandre; Silva González, Rodrigo; Lauri Espíndola, Aquino

    2009-07-01

    Here we show that a particular one-parameter generalization of the exponential function is suitable to unify most of the popular one-species discrete population dynamic models into a simple formula. A physical interpretation is given to this new introduced parameter in the context of the continuous Richards model, which remains valid for the discrete case. From the discretization of the continuous Richards’ model (generalization of the Gompertz and Verhulst models), one obtains a generalized logistic map and we briefly study its properties. Notice, however that the physical interpretation for the introduced parameter persists valid for the discrete case. Next, we generalize the (scramble competition) θ-Ricker discrete model and analytically calculate the fixed points as well as their stabilities. In contrast to previous generalizations, from the generalized θ-Ricker model one is able to retrieve either scramble or contest models.

  8. Active control of turbomachine discrete tones

    NASA Astrophysics Data System (ADS)

    Fleeter, Sanford

    This paper was directed at active control of discrete frequency noise generated by subsonic blade rows through cancellation of the blade row interaction generated propagating acoustic waves. First discrete frequency noise generated by a rotor and stator in a duct was analyzed to determine the propagating acoustic pressure waves. Then a mathematical model was developed to analyze and predict the active control of discrete frequency noise generated by subsonic blade rows through cancellation of the propagating acoustic waves, accomplished by utilizing oscillating airfoil surfaces to generate additional control propagating pressure waves. These control waves interact with the propagating acoustic waves, thereby, in principle, canceling the acoustic waves and thus, the far field discrete frequency tones. This model was then applied to a fan exit guide vane to investigate active airfoil surface techniques for control of the propagating acoustic waves, and thus the far field discrete frequency tones, generated by blade row interactions.

  9. Discrete breathers in graphane: Effect of temperature

    NASA Astrophysics Data System (ADS)

    Baimova, J. A.; Murzaev, R. T.; Lobzenko, I. P.; Dmitriev, S. V.; Zhou, Kun

    2016-05-01

    The discrete breathers in graphane in thermodynamic equilibrium in the temperature range 50-600 K are studied by molecular dynamics simulation. A discrete breather is a hydrogen atom vibrating along the normal to a sheet of graphane at a high amplitude. As was found earlier, the lifetime of a discrete breather at zero temperature corresponds to several tens of thousands of vibrations. The effect of temperature on the decay time of discrete breathers and the probability of their detachment from a sheet of graphane are studied in this work. It is shown that closely spaced breathers can exchange energy with each other at zero temperature. The data obtained suggest that thermally activated discrete breathers can be involved in the dehydrogenation of graphane, which is important for hydrogen energetics.

  10. Discrete breathers in graphane: Effect of temperature

    SciTech Connect

    Baimova, J. A.; Murzaev, R. T.; Lobzenko, I. P.; Dmitriev, S. V.; Zhou, Kun

    2016-05-15

    The discrete breathers in graphane in thermodynamic equilibrium in the temperature range 50–600 K are studied by molecular dynamics simulation. A discrete breather is a hydrogen atom vibrating along the normal to a sheet of graphane at a high amplitude. As was found earlier, the lifetime of a discrete breather at zero temperature corresponds to several tens of thousands of vibrations. The effect of temperature on the decay time of discrete breathers and the probability of their detachment from a sheet of graphane are studied in this work. It is shown that closely spaced breathers can exchange energy with each other at zero temperature. The data obtained suggest that thermally activated discrete breathers can be involved in the dehydrogenation of graphane, which is important for hydrogen energetics.

  11. Discrete multiscale wavelet shrinkage and integrodifferential equations

    NASA Astrophysics Data System (ADS)

    Didas, S.; Steidl, G.; Weickert, J.

    2008-04-01

    We investigate the relation between discrete wavelet shrinkage and integrodifferential equations in the context of simplification and denoising of one-dimensional signals. In the continuous setting, strong connections between these two approaches were discovered in 6 (see references). The key observation is that the wavelet transform can be understood as derivative operator after the convolution with a smoothing kernel. In this paper, we extend these ideas to the practically relevant discrete setting with both orthogonal and biorthogonal wavelets. In the discrete case, the behaviour of the smoothing kernels for different scales requires additional investigation. The results of discrete multiscale wavelet shrinkage and related discrete versions of integrodifferential equations are compared with respect to their denoising quality by numerical experiments.

  12. Laplacians on discrete and quantum geometries

    NASA Astrophysics Data System (ADS)

    Calcagni, Gianluca; Oriti, Daniele; Thürigen, Johannes

    2013-06-01

    We extend discrete calculus for arbitrary (p-form) fields on embedded lattices to abstract discrete geometries based on combinatorial complexes. We then provide a general definition of discrete Laplacian using both the primal cellular complex and its combinatorial dual. The precise implementation of geometric volume factors is not unique and, comparing the definition with a circumcentric and a barycentric dual, we argue that the latter is, in general, more appropriate because it induces a Laplacian with more desirable properties. We give the expression of the discrete Laplacian in several different sets of geometric variables, suitable for computations in different quantum gravity formalisms. Furthermore, we investigate the possibility of transforming from position to momentum space for scalar fields, thus setting the stage for the calculation of heat kernel and spectral dimension in discrete quantum geometries.

  13. Codes over infinite family of rings : Equivalence and invariant ring

    NASA Astrophysics Data System (ADS)

    Irwansyah, Muchtadi-Alamsyah, Intan; Muchlis, Ahmad; Barra, Aleams; Suprijanto, Djoko

    2016-02-01

    In this paper, we study codes over the ring Bk=𝔽pr[v1,…,vk]/(vi2=vi,∀i =1 ,…,k ) . For instance, we focus on two topics, i.e. characterization of the equivalent condition between two codes over Bk using a Gray map into codes over finite field 𝔽pr, and finding generators for invariant ring of Hamming weight enumerator for Euclidean self-dual codes over Bk.

  14. On the consistency between nearest-neighbor peridynamic discretizations and discretized classical elasticity models

    SciTech Connect

    Seleson, Pablo; Du, Qiang; Parks, Michael L.

    2016-08-16

    The peridynamic theory of solid mechanics is a nonlocal reformulation of the classical continuum mechanics theory. At the continuum level, it has been demonstrated that classical (local) elasticity is a special case of peridynamics. Such a connection between these theories has not been extensively explored at the discrete level. This paper investigates the consistency between nearest-neighbor discretizations of linear elastic peridynamic models and finite difference discretizations of the Navier–Cauchy equation of classical elasticity. While nearest-neighbor discretizations in peridynamics have been numerically observed to present grid-dependent crack paths or spurious microcracks, this paper focuses on a different, analytical aspect of such discretizations. We demonstrate that, even in the absence of cracks, such discretizations may be problematic unless a proper selection of weights is used. Specifically, we demonstrate that using the standard meshfree approach in peridynamics, nearest-neighbor discretizations do not reduce, in general, to discretizations of corresponding classical models. We study nodal-based quadratures for the discretization of peridynamic models, and we derive quadrature weights that result in consistency between nearest-neighbor discretizations of peridynamic models and discretized classical models. The quadrature weights that lead to such consistency are, however, model-/discretization-dependent. We motivate the choice of those quadrature weights through a quadratic approximation of displacement fields. The stability of nearest-neighbor peridynamic schemes is demonstrated through a Fourier mode analysis. Finally, an approach based on a normalization of peridynamic constitutive constants at the discrete level is explored. This approach results in the desired consistency for one-dimensional models, but does not work in higher dimensions. The results of the work presented in this paper suggest that even though nearest

  15. On the consistency between nearest-neighbor peridynamic discretizations and discretized classical elasticity models

    SciTech Connect

    Seleson, Pablo; Du, Qiang; Parks, Michael L.

    2016-08-16

    The peridynamic theory of solid mechanics is a nonlocal reformulation of the classical continuum mechanics theory. At the continuum level, it has been demonstrated that classical (local) elasticity is a special case of peridynamics. Such a connection between these theories has not been extensively explored at the discrete level. This paper investigates the consistency between nearest-neighbor discretizations of linear elastic peridynamic models and finite difference discretizations of the Navier–Cauchy equation of classical elasticity. While nearest-neighbor discretizations in peridynamics have been numerically observed to present grid-dependent crack paths or spurious microcracks, this paper focuses on a different, analytical aspect of such discretizations. We demonstrate that, even in the absence of cracks, such discretizations may be problematic unless a proper selection of weights is used. Specifically, we demonstrate that using the standard meshfree approach in peridynamics, nearest-neighbor discretizations do not reduce, in general, to discretizations of corresponding classical models. We study nodal-based quadratures for the discretization of peridynamic models, and we derive quadrature weights that result in consistency between nearest-neighbor discretizations of peridynamic models and discretized classical models. The quadrature weights that lead to such consistency are, however, model-/discretization-dependent. We motivate the choice of those quadrature weights through a quadratic approximation of displacement fields. The stability of nearest-neighbor peridynamic schemes is demonstrated through a Fourier mode analysis. Finally, an approach based on a normalization of peridynamic constitutive constants at the discrete level is explored. This approach results in the desired consistency for one-dimensional models, but does not work in higher dimensions. The results of the work presented in this paper suggest that even though nearest

  16. MULTISCALE DISCRETIZATION OF SHAPE CONTOURS

    SciTech Connect

    Prasad, L.; Rao, R.

    2000-09-01

    We present an efficient multi-scale scheme to adaptively approximate the continuous (or densely sampled) contour of a planar shape at varying resolutions. The notion of shape is intimately related to the notion of contour, and the efficient representation of the contour of a shape is vital to a computational understanding of the shape. Any polygonal approximation of a planar smooth curve is equivalent to a piecewise constant approximation of the parameterized X and Y coordinate functions of a discrete point set obtained by densely sampling the curve. Using the Haar wavelet transform for the piecewise approximation yields a hierarchical scheme in which the size of the approximating point set is traded off against the morphological accuracy of the approximation. Our algorithm compresses the representation of the initial shape contour to a sparse sequence of points in the plane defining the vertices of the shape's polygonal approximation. Furthermore, it is possible to control the overall resolution of the approximation by a single, scale-independent parameter.

  17. Seipin Is a Discrete Homooligomer†

    PubMed Central

    Binns, Derk; Lee, SungKyung; Hilton, Christopher L.; Jiang, Qiu-Xing; Goodman, Joel M.

    2011-01-01

    Seipin is a transmembrane protein that resides in the endoplasmic reticulum and concentrates at junctions between the ER and cytosolic lipid droplets. Mutations in the human seipin gene, including the missense mutation A212P, lead to congenital generalized lipodystrophy (CGL), characterized by the lack of normal adipose tissue and accumulation of fat in liver and muscles. In both yeast and CGL patient fibroblasts, seipin is required for normal lipid droplet morphology; in its absence droplets appear to bud abnormally from the ER. Here we report the first purification and physical characterization of seipin. Yeast seipin is in a large discrete protein complex. Affinity purification demonstrated that seipin is the main if not exclusive protein in the complex. Detergent sucrose gradients in H2O, and D2O and gel filtration were used to determine the size of the seipin complex and account for detergent binding. Both seipin-myc13 (seipin fused to 13 tandem copies of the myc epitope) expressed from the endogenous promoter and overexpressed seipin-mCherry form ~500 kDa proteins consisting of about 9 copies of seipin. The yeast orthologue of the human A212P allele forms only smaller complexes and is unstable; we hypothesize that this accounts for its null phenotype in humans. Seipin appears as a toroid by negative staining electron microscopy. We speculate that seipin plays at least a structural role in organizing droplets or in communication between droplets and ER. PMID:21062080

  18. Ultraviolet Ring Around the Galaxies

    NASA Image and Video Library

    2010-08-11

    Astronomers have found unexpected rings and arcs of ultraviolet light around a selection of galaxies, four of which are shown here as viewed by NASA and the European Space Agency Hubble Space Telescope.

  19. Black rings at large D

    NASA Astrophysics Data System (ADS)

    Tanabe, Kentaro

    2016-02-01

    We study the effective theory of slowly rotating black holes at the infinite limit of the spacetime dimension D. This large D effective theory is obtained by integrating the Einstein equation with respect to the radial direction. The effective theory gives equations for non-linear dynamical deformations of a slowly rotating black hole by effective equations. The effective equations contain the slowly rotating Myers-Perry black hole, slowly boosted black string, non-uniform black string and black ring as stationary solutions. We obtain the analytic solution of the black ring by solving effective equations. Furthermore, by perturbation analysis of effective equations, we find a quasinormal mode condition of the black ring in analytic way. As a result we confirm that thin black ring is unstable against non-axisymmetric perturbations. We also include 1 /D corrections to the effective equations and discuss the effects by 1 /D corrections.

  20. Dissipative ring solitons with vorticity.

    PubMed

    Soto-Crespo, J M; Akhmediev, N; Mejia-Cortés, C; Devine, N

    2009-03-16

    We study dissipative ring solitons with vorticity in the frame of the (2+1)-dimensional cubic-quintic complex Ginzburg-Landau equation. In dissipative media, radially symmetric ring structures with any vorticity m can be stable in a finite range of parameters. Beyond the region of stability, the solitons lose the radial symmetry but may remain stable, keeping the same value of the topological charge. We have found bifurcations into solitons with n-fold bending symmetry, with n independent on m. Solitons without circular symmetry can also display (m + 1)-fold modulation behaviour. A sequence of bifurcations can transform the ring soliton into a pulsating or chaotic state which keeps the same value of the topological charge as the original ring.

  1. Ring Beholds a Delicate Flower

    NASA Image and Video Library

    2005-02-11

    NASA Spitzer Space Telescope finds a delicate flower in the Ring Nebula, as shown in this image. The outer shell of this planetary nebula looks surprisingly similar to the delicate petals of a camellia blossom.

  2. Physical processes in planetary rings

    NASA Technical Reports Server (NTRS)

    Burns, Joseph A.

    1991-01-01

    A summary of research performed in 1990 is presented. The subject areas covered include perturbed narrow rings and the dynamics of circumplanetary dust. Progress made in the area of perturbed narrow rings includes: (1) the possible discovery of an undocumented moonlet in the environs of Saturn's F ring; and (2) the investigation of the consequences of a close satellite perturbing a narrow ring using numerical simulation. Progress made in the area of circumplanetary dust includes: (1) studies of the motion of circumplanetary dust under the action of radiation pressure and various electromagnetic processes; and (2) the initiation of a systematic explanation of the curious consequences of some of the perturbations that act on small particles.

  3. Earhart in the A Ring

    NASA Image and Video Library

    2013-08-19

    Cassini scientists continue their quest to understand the origin and evolution of the newly discovered features observed in Saturn A ring which have become known as propellers as shown in this image from NASA Cassini spacecraft.

  4. Vortex rings in Bose gas

    SciTech Connect

    Belyaev, S. T.

    2016-06-15

    We consider excitations that exist, in addition to phonons, in the ideal Bose gas at zero temperature. These excitations are vortex rings whose energy spectrum is similar to the roton one in liquid helium.

  5. Propeller Churns the A Ring

    NASA Image and Video Library

    2010-07-08

    This image is part of a set of images obtained by NASA Cassini spacecraft showing a propeller-shaped structure created by a hidden, embedded moon moving through one of Saturn rings. An animation is available at the Photojournal.

  6. Large Double-ringed Basin

    NASA Image and Video Library

    2000-08-05

    Taken about 40 minutes before NASA Mariner 10 made its close approach to Mercury on Sept. 21,1974, this picture shows a large double-ringed basin center of picture located in the planet south polar region

  7. Compatible Spatial Discretizations for Partial Differential Equations

    SciTech Connect

    Arnold, Douglas, N, ed.

    2004-11-25

    From May 11--15, 2004, the Institute for Mathematics and its Applications held a hot topics workshop on Compatible Spatial Discretizations for Partial Differential Equations. The numerical solution of partial differential equations (PDE) is a fundamental task in science and engineering. The goal of the workshop was to bring together a spectrum of scientists at the forefront of the research in the numerical solution of PDEs to discuss compatible spatial discretizations. We define compatible spatial discretizations as those that inherit or mimic fundamental properties of the PDE such as topology, conservation, symmetries, and positivity structures and maximum principles. A wide variety of discretization methods applied across a wide range of scientific and engineering applications have been designed to or found to inherit or mimic intrinsic spatial structure and reproduce fundamental properties of the solution of the continuous PDE model at the finite dimensional level. A profusion of such methods and concepts relevant to understanding them have been developed and explored: mixed finite element methods, mimetic finite differences, support operator methods, control volume methods, discrete differential forms, Whitney forms, conservative differencing, discrete Hodge operators, discrete Helmholtz decomposition, finite integration techniques, staggered grid and dual grid methods, etc. This workshop seeks to foster communication among the diverse groups of researchers designing, applying, and studying such methods as well as researchers involved in practical solution of large scale problems that may benefit from advancements in such discretizations; to help elucidate the relations between the different methods and concepts; and to generally advance our understanding in the area of compatible spatial discretization methods for PDE. Particular points of emphasis included: + Identification of intrinsic properties of PDE models that are critical for the fidelity of numerical

  8. Collector ring project at FAIR

    NASA Astrophysics Data System (ADS)

    Dolinskii, A.; Berkaev, D.; Blell, U.; Dimopoulou, C.; Gorda, O.; Leibrock, H.; Litvinov, S.; Laier, U.; Koop, I.; Schurig, I.; Starostenko, A.; Shatunov, P.; Weinrich, U.

    2015-11-01

    The collector ring is a dedicated ring for fast cooling of ions coming from separators at the FAIR project. To accommodate optimal technical solutions, a structure of a magnet lattice was recently reviewed and modified. Consequently, more appropriate technical solutions for the main magnets could be adopted. A general layout and design of the present machine is shown. The demanding extraction schemes have been detailed and open design issues were completed.

  9. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, Richard N.; Martin, Juergen; Paldus, Barbara A.; Xie, Jinchun

    1999-01-01

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS).

  10. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, R.N.; Martin, J.; Paldus, B.A.; Xie, J.

    1999-06-15

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS). 6 figs.

  11. Resonance capture and Saturn's rings

    SciTech Connect

    Patterson, C.W.

    1986-05-01

    We have assigned the resonances apparently responsible for the stabilization of the Saturn's shepherd satellites and for the substructure seen in the F-ring and the ringlets in the C-ring. We show that Saturn's narrow ringlets have a substructure determined by three-body resonances with Saturn's ringmoons and the sun. We believe such resonances have important implications to satellite formation. 17 refs., 1 fig., 1 tab.

  12. Analysis of Ring Wake Simulations

    NASA Astrophysics Data System (ADS)

    Lewis, M. C.; Stewart, G. R.

    1999-09-01

    indent=20pt Collisional N-body simulations at the edge of a perturbed planetary ring are used to model the edges of the Encke gap in Saturn's rings. A small satellite, Pan, orbits inside the Encke gap and excites forced eccentricities and density wakes on both edges of the gap. The simulations use a local cell method to model a narrow ring using particles of the appropriate size for the A-ring at the proper optical depth. In the simulations we see evidence for shear reversal at the wake peaks. Our results imply that the most significant factor in the damping of the wakes is the reduction of the forced eccentricity and not randomization of the phase angles of the particles. The reduction of the forced eccentricity occurs in an orderly fashion with steep drops at each successive wake maximum following the highest density wake peak. indent=20pt At the inner edge (that nearer the perturber) we see phase shifts visible as bending of the line wake maxima. Because the simulations are actually of narrow rings, we also see a number of interesting phenomena at the outer edge. A strong boundary layer forms at that edge, which becomes partially detached from the rest of the ring. The wake patterns persist much further downstream in this boundary layer than they do in the rest of the ring. We also observe that in the less dense region between the main section of the ring and the boundary layer the magnitude of the forced eccentricities reverse their behavior in the main part and increase at each wake maxima. indent=20pt At the talk we will compare our results to the various analytic theories of Borderies, Goldreich, and Tremaine.

  13. Sources and Losses of Ring Current Ions

    NASA Technical Reports Server (NTRS)

    Chen, Sheng-Hsien; Fok, Mei-Ching H.; Angeloupoulos, Vassilis

    2010-01-01

    During geomagnetic quiet times, in-situ measurements of ring current energetic ions (few to few tens of keVs) from THEMIS spacecraft often exhibit multiple ion populations at discrete energies that extend from the inner magnetosphere to the magnetopause at dayside or plasma sheet at nightside. During geomagnetic storm times, the levels of fluxes as well as the mean energies of these ions elevated dramatically and the more smooth distributions in energies and distances during quiet times are disrupted into clusters of ion populations with more confined spatial extends. This reveals local plasma heating processes that might have come into play. Several processes have been proposed. Magnetotail dipolarization, sudden enhancement of field-aligned current, local current disruptions, and plasma waves are possible mechanisms to heat the ions locally as well as strong convections of energetic ions directly from the magnetotail due to reconnections. We will examine two geomagnetic storms on October 11, 2008 and July 22, 2009 to reveal possible heating mechanisms. We will analyze in-situ plasma and magnetic field measurements from THEMIS, GOES, and DMSP for the events to study the ion pitch angle distributions and magnetic field perturbations in the auroral ionosphere and inner magnetosphere where the plasma heating processes occur.

  14. Faint F Ring and Prometheus

    NASA Image and Video Library

    2016-11-21

    Surface features are visible on Saturn's moon Prometheus in this view from NASA's Cassini spacecraft. Most of Cassini's images of Prometheus are too distant to resolve individual craters, making views like this a rare treat. Saturn's narrow F ring, which makes a diagonal line beginning at top center, appears bright and bold in some Cassini views, but not here. Since the sun is nearly behind Cassini in this image, most of the light hitting the F ring is being scattered away from the camera, making it appear dim. Light-scattering behavior like this is typical of rings comprised of small particles, such as the F ring. This view looks toward the unilluminated side of the rings from about 14 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 24, 2016. The view was acquired at a distance of approximately 226,000 miles (364,000 kilometers) from Prometheus and at a sun-Prometheus-spacecraft, or phase, angle of 51 degrees. Image scale is 1.2 miles (2 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20508

  15. History of Neptune's Ring Arcs

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Colwell, J. E.; Canup, R. M.

    1997-07-01

    The recent dynamical calculations for Neptune's Adams ring arcs by Foryta and Sicardy (1996) and Hanninen and Porco (1997) determine the basic evolutionary parameters for this system. The ring evolution is dominated by stochastic events, particularly chaotic motion that causes a migration between the corotation sites (FS96) and collisions near quadrature (HP97). A basic problem is that the high velocity collisions that produce the dusty arcs at the Galatea corotation resonances rapidly depopulate these sites (Colwell and Esposito 1990). With the new results in hand for the evolution of the ring particles over periods of less than a century, we can now calculate the long-term stochastic evolution of the Adams ring. Using a finite Markov chain as a model for this stochastic process, we follow the suggestion by FS96 that corotation sites provide preferential locations for accretion. A more general conclusion is that the longitudinal concentration of material in a few nearby sites (and that the majority of the Adams ring material is residing there) requires either an exceedingly recent event (EC92) or that the corotation sites be absorbing states of the Markov chain.In the latter case, the competing processes of chaotic diffusion and frustrated accretion can provide the arc and clump features as recurrent transient events near the Roche limit. Similar phenomena would be expected for Saturn's F and G rings.

  16. Classifying Saturn's F Ring Strands

    NASA Astrophysics Data System (ADS)

    Albers, Nicole; Sremcevic, M.; Esposito, L. W.; Colwell, J. E.

    2009-09-01

    The Cassini Ultraviolet Imaging Spectrograph (UVIS) High Speed Photometer (HSP) has recorded more than 113 stellar occultations by Saturn's F ring providing measurements with ring plane resolutions of a few dozen meters and better. Inner and outer F ring strands have been seen throughout the Cassini mission where they revealed themselves as non-continuous, azimuthally and temporally highly variable structures. In the light of a more accurate orbit description of the F ring core we find evidence for a ring that becomes dynamically more active as the system approaches anti-apse alignment with Prometheus. This is consistent with the observed increased strand activity. A recent strand that morphologically resembles the core is the strongest seen to date and points to the intricate relation between core and strands indicating the strands' violent creation. Using more than 150 identifications of various strands, we trace their kinematics and infer dynamical timescales and photometric properties. Implications for the dynamical evolution of the F ring will be discussed. This research was supported by the Cassini Project.

  17. Collar nut and thrust ring

    DOEpatents

    Lowery, Guy B.

    1991-01-01

    A collar nut comprises a hollow cylinder having fine interior threads at one end for threadably engaging a pump mechanical seal assembly and an inwardly depending flange at the other end. The flange has an enlarged portion with a groove for receiving an O-ring for sealing against the intrusion of pumpage from the exterior. The enlarged portion engages a thrust ring about the pump shaft for crushing a hard O-ring, such as a graphite O-ring. The hard O-ring seals the interior of the mechanical seal assembly and pump housing against the loss of lubricants or leakage of pumpage. The fine threads of the hollow cylinder provide the mechanical advantage for crushing the hard O-ring evenly and easily with a hand tool from the side of the collar nut rather than by tightening a plurality of bolts from the end and streamlines the exterior surface of the mechanical seal. The collar nut avoids the spatial requirements of bolt heads at the end of a seal and associated bolt head turbulence.

  18. The ring of the narcissist.

    PubMed

    Shengold, L

    1995-12-01

    The author has not attempted a complete exposition of the meaning of rings--which can refer to and symbolise many aspects of relationships with other human beings from 'transitional objects' of early development (Winnicott) to all sorts of bonds of loyalty, friendship, and love in the life of the child and the adult. He stresses the meanings of the ring from the point of view of early narcissistic development--the 'body ego' time of early development in which symbolism (in Freud's sense) develops. The clinical and literary examples therefore illustrate the use of rings as magical narcissistic symbols--part subject and part object--derived developmentally from the body ego and ultimately from the body sphincters. Endowed with these regressive primitive meanings, rings are felt to have magical powers that can either preserve or destroy, and that can control emotions in the self and in others. In the course of ordinary or pathological narcissistic regressions, rings (consciously associated with many positive feelings and achievements) also partake, in so far as they are 'Freudian' symbols, of qualities associated with developmentally early defensive mechanisms and modes of psychic functioning (projection, introjection; idealisation, devaluation). In the cases cited, rings seemed specifically associated with (and to symbolise) sphincteric (largely anal) narcissistic defensiveness--the mind functioning as an emotional sphincteric counterpart primarily deadening and distancing affect but intermittently letting through primitive rage and primal polymorphous perverse sexual impulses.

  19. Physics of Jupiter's Gossamer Rings

    NASA Astrophysics Data System (ADS)

    Hamilton, Douglas P.; Krueger, H.

    2007-10-01

    Thebe's gossamer ring, the outermost and faintest of Jupiter's rings, has an outward extension that we have previously argued is due to a shadow resonance (Hamilton 2003, DPS meeting #35, #11.09). A shadow resonance arises from the abrupt shutoff of photoelectric charging when a dust particle enters Jupiter's shadow which, in turn, affects the strength of the electromagnetic perturbation from the planet's intense magnetic field. The result is a coupled oscillation between a particle's orbital eccentricity and its semimajor axis. Ring material spreads outward from Thebe while maintaining its vertical thickness just as observed by Galileo imaging. In addition to cameras, the Galileo spacecraft was also equipped with dust and plasma detectors. The spacecraft made two passes through the ring and its dust detector found that 1) dust fluxes drop immediately interior to Thebe's orbit, 2) some grains have inclinations in excess of 20 degrees and 3) submicron particles are present in the Amalthea ring in much greater numbers than in the Thebe ring. These findings can all be explained in the context of our shadow resonance model: the inner boundary is a direct consequence of the conservation of the Electromagnetic Jacobi Constant, the high inclinations are forced by a vertical resonance, and the excess submicron particles are a consequence of the weakening of electromagnetic forces in the vicinity of synchronous orbit. In this talk, we will present the data sets as well as detailed numerical simulations that back up these claims.

  20. Of Rings and Volcanoes

    NASA Astrophysics Data System (ADS)

    2002-01-01

    Office National d'Etudes et de Recherches Aérospatiales (ONERA) , Laboratoire d'Astrophysique de Grenoble (LAOG) and the DESPA and DASGAL laboratories of the Observatoire de Paris in France, in collaboration with ESO. The CONICA infra-red camera was built, under an ESO contract, by the Max-Planck-Institut für Astronomie (MPIA) (Heidelberg) and the Max-Planck Institut für Extraterrestrische Physik (MPE) (Garching) in Germany, in collaboration with ESO. Saturn - Lord of the rings ESO PR Photo 04a/02 ESO PR Photo 04a/02 [Preview - JPEG: 460 x 400 pix - 54k] [Normal - JPEG: 1034 x 800 pix - 200k] Caption : PR Photo 04a/02 shows the giant planet Saturn, as observed with the VLT NAOS-CONICA Adaptive Optics instrument on December 8, 2001; the distance was 1209 million km. It is a composite of exposures in two near-infrared wavebands (H and K) and displays well the intricate, banded structure of the planetary atmosphere and the rings. Note also the dark spot at the south pole at the bottom of the image. One of the moons, Tethys, is visible as a small point of light below the planet. It was used to guide the telescope and to perform the adaptive optics "refocussing" for this observation. More details in the text. Technical information about this photo is available below. This NAOS/CONICA image of Saturn ( PR Photo 04a/02 ), the second-largest planet in the solar system, was obtained at a time when Saturn was close to summer solstice in the southern hemisphere. At this moment, the tilt of the rings was about as large as it can be, allowing the best possible view of the planet's South Pole. That area was on Saturn's night side in 1982 and could therefore not be photographed during the Voyager encounter. The dark spot close to the South Pole is a remarkable structure that measures approximately 300 km across. It was only recently observed in visible light from the ground with a telescope at the Pic du Midi Observatory in the Pyrenees (France) - this is the first infrared image to

  1. On the definition of discrete hydrodynamic variables.

    PubMed

    Español, Pep; Zúñiga, Ignacio

    2009-10-28

    The Green-Kubo formula for discrete hydrodynamic variables involves information about not only the fluid transport coefficients but also about discrete versions of the differential operators that govern the evolution of the discrete variables. This gives an intimate connection between discretization procedures in fluid dynamics and coarse-graining procedures used to obtain hydrodynamic behavior of molecular fluids. We observed that a natural definition of discrete hydrodynamic variables in terms of Voronoi cells leads to a Green-Kubo formula which is divergent, rendering the full coarse-graining strategy useless. In order to understand this subtle issue, in the present paper we consider the coarse graining of noninteracting Brownian particles. The discrete hydrodynamic variable for this problem is the number of particles within Voronoi cells. Thanks to the simplicity of the model we spot the origin of the singular behavior of the correlation functions. We offer an alternative definition, based on the concept of a Delaunay cell that behaves properly, suggesting the use of the Delaunay construction for the coarse graining of molecular fluids at the discrete hydrodynamic level.

  2. Discrete flavour symmetries from the Heisenberg group

    NASA Astrophysics Data System (ADS)

    Floratos, E. G.; Leontaris, G. K.

    2016-04-01

    Non-abelian discrete symmetries are of particular importance in model building. They are mainly invoked to explain the various fermion mass hierarchies and forbid dangerous superpotential terms. In string models they are usually associated to the geometry of the compactification manifold and more particularly to the magnetised branes in toroidal compactifications. Motivated by these facts, in this note we propose a unified framework to construct representations of finite discrete family groups based on the automorphisms of the discrete and finite Heisenberg group. We focus in particular, on the PSL2 (p) groups which contain the phenomenologically interesting cases.

  3. Discrete Elements Method of Neutral Particle Transport

    DTIC Science & Technology

    1983-10-01

    0 ,,S" . K A t - "’.* DISCRETE ELEMENTS METHOD NEUTRAL PARTICLE TRANSPORT ..- DISSERTATION AF. IT/DS/PH/83-5 Kirk A. Mathews LCDR USN D~ Approved for...DISCRETE ELEMENTS METHOD OF NEUTRAL PARTICLE TRANSPORT DISSERTATION Presented to the Faculty of the School of Engineering of the Air Force Institute...o .°. .• . r •.- - DS/PH/83-5 DISCRETE ELEMENTS METHOD OF NEUTRAL PARTICLE TRANSPORT 4 "by Kirk A. Mathews LCDR USN Approved: , Charles J

  4. Hairs of discrete symmetries and gravity

    NASA Astrophysics Data System (ADS)

    Choi, Kang Sin; Kim, Jihn E.; Kyae, Bumseok; Nam, Soonkeon

    2017-06-01

    Gauge symmetries are known to be respected by gravity because gauge charges carry flux lines, but global charges do not carry flux lines and are not conserved by gravitational interaction. For discrete symmetries, they are spontaneously broken in the Universe, forming domain walls. Since the realization of discrete symmetries in the Universe must involve the vacuum expectation values of Higgs fields, a string-like configuration (hair) at the intersection of domain walls in the Higgs vacua can be realized. Therefore, we argue that discrete charges are also respected by gravity.

  5. Stochastic Kuramoto oscillators with discrete phase states

    NASA Astrophysics Data System (ADS)

    Jörg, David J.

    2017-09-01

    We present a generalization of the Kuramoto phase oscillator model in which phases advance in discrete phase increments through Poisson processes, rendering both intrinsic oscillations and coupling inherently stochastic. We study the effects of phase discretization on the synchronization and precision properties of the coupled system both analytically and numerically. Remarkably, many key observables such as the steady-state synchrony and the quality of oscillations show distinct extrema while converging to the classical Kuramoto model in the limit of a continuous phase. The phase-discretized model provides a general framework for coupled oscillations in a Markov chain setting.

  6. Discrete symmetries and de Sitter spacetime

    SciTech Connect

    Cotăescu, Ion I. Pascu, Gabriel

    2014-11-24

    Aspects of the ambiguity in defining quantum modes on de Sitter spacetime using a commuting system composed only of differential operators are discussed. Discrete symmetries and their actions on the wavefunction in commonly used coordinate charts are reviewed. It is argued that the system of commuting operators can be supplemented by requiring the invariance of the wavefunction to combined discrete symmetries- a criterion which selects a single state out of the α-vacuum family. Two such members of this family are singled out by particular combined discrete symmetries- states between which exists a well-known thermality relation.

  7. Accretion in Saturn's F Ring

    NASA Astrophysics Data System (ADS)

    Meinke, B. K.; Esposito, L. W.; Stewart, G.

    2012-12-01

    Saturn's F ring is the solar system's principal natural laboratory for direct observation of accretion and disruption processes. The ring resides in the Roche zone, where tidal disruption competes with self-gravity, which allows us to observe the lifecycle of moonlets. Just as nearby moons create structure at the B ring edge (Esposito et al. 2012) and the Keeler gap (Murray 2007), the F ring "shepherding" moons Prometheus and Pandora stir up ring material and create observably changing structures on timescales of days to decades. In fact, Beurle et al (2010) show that Prometheus makes it possible for "distended, yet gravitationally coherent clumps" to form in the F ring, and Barbara and Esposito (2002) predicted a population of ~1 km bodies in the ring. In addition to the observations over the last three decades, the Cassini Ultraviolet Imaging Spectrograph (UVIS) has detected 27 statistically significant features in 101 occultations by Saturn's F ring since July 2004. Seventeen of those 27 features are associated with clumps of ring material. Two features are opaque in occultation, which makes them candidates for solid objects, which we refer to as Moonlets. The 15 other features partially block stellar signal for 22 m to just over 3.7 km along the radial expanse of the occultation. Upon visual inspection of the occultation profile, these features resemble Icicles, thus we will refer to them as such here. The density enhancements responsible for such signal attenuations are likely due to transient clumping of material, evidence that aggregations of material are ubiquitous in the F ring. Our lengthy observing campaign reveals that Icicles are likely transient clumps, while Moonlets are possible solid objects. Optical depth is an indicator of clumping because more-densely aggregated material blocks more light; therefore, it is natural to imagine moonlets as later evolutionary stage of icicle, when looser clumps of material compact to form a feature that appears

  8. Study for ILC Damping Ring at KEKB

    SciTech Connect

    Flanagan, J.W.; Fukuma, H.; Kanazawa, K.I.; Koiso, H.; Masuzawa, M.; Ohmi, Kazuhito; Ohnishi, Y.; Oide, Katsunobu; Suetsugu, Y.; Tobiyama, M.; Pivi, M.; /SLAC

    2011-11-04

    ILC damping ring consists of very low emittance electron and positron storage rings. It is necessary for ILC damping ring to study electron cloud effects in such low emittance positron ring. We propose a low emittance operation of KEKB to study the effects.

  9. Double acting stirling engine piston ring

    DOEpatents

    Howarth, Roy B.

    1986-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  10. Reinforcement core facilitates O-ring installation

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Reinforcement core holds O-ring in place within a structure while adjacent parts are being assembled. The core in the O-ring adds circumferential rigidity to the O-ring material. This inner core does not appreciably affect the sectional elasticity or gland-sealing characteristics of the O-ring.

  11. Plasma deposited rider rings for hot displacer

    DOEpatents

    Kroebig, Helmut L.

    1976-01-01

    A hot cylinder for a cryogenic refrigerator having two plasma spray deposited rider rings of a corrosion and abrasion resistant material provided in the rider ring grooves, wherein the rider rings are machined to the desired diameter and width after deposition. The rider rings have gas flow flats machined on their outer surface.

  12. Concentric ring flywheel without expansion separators

    DOEpatents

    Kuklo, T.C.

    1999-08-24

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion. 3 figs.

  13. Concentric ring flywheel without expansion separators

    DOEpatents

    Kuklo, Thomas C.

    1999-01-01

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion.

  14. Running Parallel Discrete Event Simulators on Sierra

    SciTech Connect

    Barnes, P. D.; Jefferson, D. R.

    2015-12-03

    In this proposal we consider porting the ROSS/Charm++ simulator and the discrete event models that run under its control so that they run on the Sierra architecture and make efficient use of the Volta GPUs.

  15. The discrete-time compensated Kalman filter

    NASA Technical Reports Server (NTRS)

    Lee, W. H.; Athans, M.

    1978-01-01

    A suboptimal dynamic compensator to be used in conjunction with the ordinary discrete time Kalman filter was derived. The resultant compensated Kalman Filter has the property that steady state bias estimation errors, resulting from modelling errors, were eliminated.

  16. Commutation Relations and Discrete Garnier Systems

    NASA Astrophysics Data System (ADS)

    Ormerod, Christopher M.; Rains, Eric M.

    2016-11-01

    We present four classes of nonlinear systems which may be considered discrete analogues of the Garnier system. These systems arise as discrete isomonodromic deformations of systems of linear difference equations in which the associated Lax matrices are presented in a factored form. A system of discrete isomonodromic deformations is completely determined by commutation relations between the factors. We also reparameterize these systems in terms of the image and kernel vectors at singular points to obtain a separate birational form. A distinguishing feature of this study is the presence of a symmetry condition on the associated linear problems that only appears as a necessary feature of the Lax pairs for the least degenerate discrete Painlevé equations.

  17. Causal fermions in discrete space-time

    NASA Astrophysics Data System (ADS)

    Farrelly, Terence C.; Short, Anthony J.

    2014-01-01

    In this paper, we consider fermionic systems in discrete space-time evolving with a strict notion of causality, meaning they evolve unitarily and with a bounded propagation speed. First, we show that the evolution of these systems has a natural decomposition into a product of local unitaries, which also holds if we include bosons. Next, we show that causal evolution of fermions in discrete space-time can also be viewed as the causal evolution of a lattice of qubits, meaning these systems can be viewed as quantum cellular automata. Following this, we discuss some examples of causal fermionic models in discrete space-time that become interesting physical systems in the continuum limit: Dirac fermions in one and three spatial dimensions, Dirac fields, and briefly the Thirring model. Finally, we show that the dynamics of causal fermions in discrete space-time can be efficiently simulated on a quantum computer.

  18. Vortex chains travelling with discrete velocities

    NASA Astrophysics Data System (ADS)

    Malishevskii, A. S.; Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G.

    2008-05-01

    It has been shown that Swihart waves slowing down caused by Josephson junction spatial dispersion leads to the new field periodic nonlinear vortex states moving with discrete velocities. Swihart waves trapping by periodic vortex structures is discovered.

  19. Motion of Discrete Interfaces Through Mushy Layers

    NASA Astrophysics Data System (ADS)

    Braides, Andrea; Solci, Margherita

    2016-08-01

    We study the geometric motion of sets in the plane derived from the homogenization of discrete ferromagnetic energies with weak inclusions. We show that the discrete sets are composed by a `bulky' part and an external `mushy region' composed only of weak inclusions. The relevant motion is that of the bulky part, which asymptotically obeys to a motion by crystalline mean curvature with a forcing term, due to the energetic contribution of the mushy layers, and pinning effects, due to discreteness. From an analytical standpoint, it is interesting to note that the presence of the mushy layers implies only a weak and not strong convergence of the discrete motions, so that the convergence of the energies does not commute with the evolution. From a mechanical standpoint it is interesting to note the geometrical similarity of some phenomena in the cooling of binary melts.

  20. Radix Representation of Triangular Discrete Grid System

    NASA Astrophysics Data System (ADS)

    Ben, J.; Li, Y. L.; Wang, R.

    2016-11-01

    Discrete Global Grid Systems (DGGSs) are spatial references that use a hierarchical tessellation of cells to partition and address the entire globe. It provides an organizational structure that permits fast integration between multiple sources of large and variable geospatial data. Although many endeavors have been done to describe certain discrete grid systems, there still lack of a uniform mathematical framework for them. This paper simplifies the planar class I aperture 4 triangular discrete grid system into a hierarchical lattice model which is proved to be a radix system in the complex number plane. Mathematical properties of the radix system reveal the discrete grid system is equivalent to the set of complex numbers with special form. The conclusion provides a potential way to build a uniform mathematical framework of DGGS and can be used to design efficient encoding and spatial operation scheme for DGGS.

  1. A Few Continuous and Discrete Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Zhang, Yufeng; Rui, Wenjuan

    2016-08-01

    Starting from a 2-unimodular group, we construct its new Lie algebras for which the positive-order Lax pairs and the negative-order Lax pairs are introduced, respectively. With the help of the resulting structure equation of the group we generate some partial differential equations including the well-known MKdV equation, the sine-Gordon equation, the hyperbolic sine-Gordon equation and other new nonlinear evolution equations. With the aid of the Tu scheme combined with the given Lax pairs, we obtain the isospectral and nonisospectral hierarchies of evolution equations, from which we generate two sets of symmetries of a generalized nonlinear Schrödinger (gNLS) equation. Finally, we discretize the Lax pairs to obtain a set of coupled semi-discrete equations. As their reduction, we produce the semi-discrete MKdV equation and semi-discrete NLS equation.

  2. Comparing the Discrete and Continuous Logistic Models

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2008-01-01

    The solutions of the discrete logistic growth model based on a difference equation and the continuous logistic growth model based on a differential equation are compared and contrasted. The investigation is conducted using a dynamic interactive spreadsheet. (Contains 5 figures.)

  3. Comparing the Discrete and Continuous Logistic Models

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2008-01-01

    The solutions of the discrete logistic growth model based on a difference equation and the continuous logistic growth model based on a differential equation are compared and contrasted. The investigation is conducted using a dynamic interactive spreadsheet. (Contains 5 figures.)

  4. Dynamic discretization method for solving Kepler's equation

    NASA Astrophysics Data System (ADS)

    Feinstein, Scott A.; McLaughlin, Craig A.

    2006-09-01

    Kepler’s equation needs to be solved many times for a variety of problems in Celestial Mechanics. Therefore, computing the solution to Kepler’s equation in an efficient manner is of great importance to that community. There are some historical and many modern methods that address this problem. Of the methods known to the authors, Fukushima’s discretization technique performs the best. By taking more of a system approach and combining the use of discretization with the standard computer science technique known as dynamic programming, we were able to achieve even better performance than Fukushima. We begin by defining Kepler’s equation for the elliptical case and describe existing solution methods. We then present our dynamic discretization method and show the results of a comparative analysis. This analysis will demonstrate that, for the conditions of our tests, dynamic discretization performs the best.

  5. Interaction of the BKCa channel gating ring with dendrotoxins

    PubMed Central

    Takacs, Zoltan; Imredy, John P; Bingham, Jon-Paul; Zhorov, Boris S; Moczydlowski, Edward G

    2014-01-01

    Two classes of small homologous basic proteins, mamba snake dendrotoxins (DTX) and bovine pancreatic trypsin inhibitor (BPTI), block the large conductance Ca2+-activated K+ channel (BKCa, KCa1.1) by production of discrete subconductance events when added to the intracellular side of the membrane. This toxin-channel interaction is unlikely to be pharmacologically relevant to the action of mamba venom, but as a fortuitous ligand-protein interaction, it has certain biophysical implications for the mechanism of BKCa channel gating. In this work we examined the subconductance behavior of 9 natural dendrotoxin homologs and 6 charge neutralization mutants of δ-dendrotoxin in the context of current structural information on the intracellular gating ring domain of the BKCa channel. Calculation of an electrostatic surface map of the BKCa gating ring based on the Poisson-Boltzmann equation reveals a predominantly electronegative surface due to an abundance of solvent-accessible side chains of negatively charged amino acids. Available structure-activity information suggests that cationic DTX/BPTI molecules bind by electrostatic attraction to site(s) on the gating ring located in or near the cytoplasmic side portals where the inactivation ball peptide of the β2 subunit enters to block the channel. Such an interaction may decrease the apparent unitary conductance by altering the dynamic balance of open versus closed states of BKCa channel activation gating. PMID:25483585

  6. Instantaneous Frequency and Damping from Transient Ring-Down Data

    SciTech Connect

    Kuether, Robert J.; Brake, Matthew Robert

    2015-10-01

    Broadband impact excitation in structural dynamics is a common technique used to detect and characterize nonlinearities in mechanical systems since it excites many frequencies of a structure at once and can be applied with a variety of boundary conditions. Non-stationary time signals from transient ring-down measurements require time-frequency analysis tools to observe variations in frequency and energy dissipation as the response evolves. This work uses the short-time Fourier transform to estimate the instantaneous frequency and damping ratio from either measured or simulated transient ring-down data. By combining the discrete Fourier transform with an expanding or contracting window function that moves along the time axis, the resulting spectrum is used to estimate the instantaneous frequencies, damping and complex Fourier coefficients. This method is demonstrated on a multi-degree-of-freedom beam with a cubic spring attachment, and investigates the amplitudefrequency dependence in connection to the undamped nonlinear normal modes. A second example shows the results from experiment ring-down response on a beam with a lap joint, and reveals how the system behaves as energy dissipates.

  7. Terminal Dynamics Approach to Discrete Event Systems

    NASA Technical Reports Server (NTRS)

    Zak, Michail; Meyers, Ronald

    1995-01-01

    This paper presents and discusses a mathematical formalism for simulation of discrete event dynamic (DED)-a special type of 'man-made' systems to serve specific purposes of information processing. The main objective of this work is to demonstrate that the mathematical formalism for DED can be based upon a terminal model of Newtonian dynamics which allows one to relax Lipschitz conditions at some discrete points.!.

  8. Discrete Surface Modelling Using Partial Differential Equations.

    PubMed

    Xu, Guoliang; Pan, Qing; Bajaj, Chandrajit L

    2006-02-01

    We use various nonlinear partial differential equations to efficiently solve several surface modelling problems, including surface blending, N-sided hole filling and free-form surface fitting. The nonlinear equations used include two second order flows, two fourth order flows and two sixth order flows. These nonlinear equations are discretized based on discrete differential geometry operators. The proposed approach is simple, efficient and gives very desirable results, for a range of surface models, possibly having sharp creases and corners.

  9. Development of discrete components. Final report

    SciTech Connect

    Brown, R.J.

    1995-11-01

    Allied-Signal Inc, Kansas City Division, was provided with funding to maintain the capability to procure discrete components for various applications. A development project was undertaken to procure transistor die from one supplier for assembly into finished components by a different supplier. These components would be SA-equivalent with appropriate preconditioning, testing, and certification, The methodologies developed herein go far to ensure the future availability of discrete components.

  10. Discrete mechanics, "time machines" and hybrid systems

    NASA Astrophysics Data System (ADS)

    Elze, Hans-Thomas

    2013-09-01

    Modifying the discrete mechanics proposed by T.D. Lee, we construct a class of discrete classical Hamiltonian systems, in which time is one of the dynamical variables. This includes a toy model of "time machines" which can travel forward and backward in time and which differ from models based on closed timelike curves (CTCs). In the continuum limit, we explore the interaction between such time reversing machines and quantum mechanical objects, employing a recent description of quantum-classical hybrids.

  11. Creative Visualization in Discrete Global Grid System

    NASA Astrophysics Data System (ADS)

    Etemad, K.; Samavati, F.; Sherlock, M. J.

    2016-12-01

    Discrete Global Grid System (DGGS) is a disruptive method for developing digital representation of the Earth. In DGGS, to create a multiresolution representation of the Earth, the surface of the Earth is discretized to a hierarchy of indexed (mostly) regular cells. In this talk, an overview of research projects and recent achievements from my group related to DGGS is provided. This covers example works in large geospatial data processing and streaming, as well as creative visualization and interaction in the context of DGGS.

  12. Intrinsic structure in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Albers, N.

    2015-10-01

    Saturn's rings are the most prominent in our Solar system and one example of granular matter in space. Dominated by tides and inelastic collisions the system is highly flattened being almost 300000km wide while only tens of meters thick. Individual particles are composed of primarily water ice and range from microns to few tens of meters in size. Apparent patterns comprise ringlets, gaps, kinematic wakes, propellers, bending waves, and the winding spiral arms of density waves. These large-scale structures are perturbations foremost created by external as well as embedded moons. Observations made by the Cassini spacecraft currently in orbit around Saturn show these structures in unprecedented detail. But high-resolution measurements reveal the presence of small-scale structures throughout the system. These include self-gravity wakes (50-100m), overstable waves (100-300m), subkm structure at the A and B ring edges, "straw" and "ropy" structures (1-3km), and the C ring "ghosts". Most of these had not been anticipated and are found in perturbed regions, driven by resonances with external moons, where the system undergoes periodic phases of compression and relaxation that correlate with the presence of structure. High velocity dispersion and the presence of large clumps imply structure formation on time scales as short as one orbit (about 10 hours). The presence of these intrinsic structures is seemingly the response to varying local conditions such as internal density, optical depth, underlying particle size distribution, granular temperature, and distance from the central planet. Their abundance provides evidence for an active and dynamic ring system where aggregation and fragmentation are ongoing on orbital timescales. Thus a kinetic description of the rings may be more appropriate than the fluid one. I will present Cassini Ultraviolet Spectrometer (UVIS) High Speed Photometer (HSP) occultations, Voyager 1 and 2 Imaging Science Subsystem (ISS), and high

  13. Hydrodynamic Simulations of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Miller, Jacob; Stewart, G. R.; Esposito, L. W.

    2013-10-01

    Simulations of rings have traditionally been done using N-body methods, granting insight into the interactions of individual ring particles on varying scales. However, due to the scale of a typical ring system and the sheer number of particles involved, a global N-body simulation is too computationally expensive, unless particle collisions are replaced by stochastic forces (Bromley & Kenyon, 2013). Rings are extraordinarily flat systems and therefore are well-suited to existing geophysical shallow-water hydrodynamics models with well-established non-linear advection methods. By adopting a general relationship between pressure and surface density such as a polytropic equation of state, we can modify the shallow-water formula to treat a thin, compressible, self-gravitating, shearing fluid. Previous hydrodynamic simulations of planetary rings have been restricted to axisymmetric flows and therefore have not treated the response to nonaxisymmetric perturbations by moons (Schmidt & Tscharnuter 1999, Latter & Ogilvie 2010). We seek to expand on existing hydrodynamic methods and, by comparing our work with complementary N-body simulations and Cassini observations, confirm the veracity of our results at small scales before eventually moving to a global domain size. We will use non-Newtonian, dynamically variable viscosity to model the viscous transport caused by unresolved self-gravity wakes. Self-gravity will be added to model the dynamics of large-scale structures, such as density waves and edge waves. Support from NASA Outer Planets and Planetary Geology and Geophysics programs is gratefully acknowledged.

  14. Storage ring working group report

    SciTech Connect

    Krinsky, S.

    1997-01-01

    Over the last two decades great progress has been made in the development of storage rings with small transverse emittance. It is now a good time to consider the possibility of achieving very short bunches m storage rings. From the perspective of synchrotron radiation source development, there are at least two motivations for obtaining short electron bunches: (1) the generation of sub- picosecond x-ray pulses and (2) the coherent emission of sub- picosecond pulses of far infrared radiation. A useful short-term goal is the experimental study of bunches with 1 ps rms length both at high ({approx_gt} 1 GeV) and low ({approx_lt} 150 MeV) electron energies. Experiments on 1 ps bunches are now feasible and can yield new insight into the high frequency impedance of storage rings and the associated phenomena which can result in bunch lengthening. Achievement of 1 ps bunches can also be expected to allow the first observation of coherent synchrotron radiation in a storage ring, in the millimeter wavelength regime. A longer-term objective is the realization of 100 fs bunches. Achievement of this goal not only will advance understanding of storage rings but will open up new opportunities in synchrotron radiation based research at both x-ray and far infrared wavelengths. It is now an appropriate time to carry forward theoretical investigations clarifying the fundamental limitations on bunch length, and to devise schemes to minimize it.

  15. Ring Beholds a Delicate Flower

    NASA Technical Reports Server (NTRS)

    2005-01-01

    NASA's Spitzer Space Telescope finds a delicate flower in the Ring Nebula, as shown in this image. The outer shell of this planetary nebula looks surprisingly similar to the delicate petals of a camellia blossom. A planetary nebula is a shell of material ejected from a dying star. Located about 2,000 light years from Earth in the constellation Lyra, the Ring Nebula is also known as Messier Object 57 and NGC 6720. It is one of the best examples of a planetary nebula and a favorite target of amateur astronomers.

    The 'ring' is a thick cylinder of glowing gas and dust around the doomed star. As the star begins to run out of fuel, its core becomes smaller and hotter, boiling off its outer layers. The telescope's infrared array camera detected this material expelled from the withering star. Previous images of the Ring Nebula taken by visible-light telescopes usually showed just the inner glowing loop of gas around the star. The outer regions are especially prominent in this new image because Spitzer sees the infrared light from hydrogen molecules. The molecules emit infrared light because they have absorbed ultraviolet radiation from the star or have been heated by the wind from the star.

    Download the QuickTime movie for the animated version of this Ring Nebula image.

  16. Archiving of Planetary Ring Data

    NASA Technical Reports Server (NTRS)

    Elliot, James L.

    2001-01-01

    Stellar occultation data provide our only Earth-based means of probing planetary rings at kilometer spatial resolution. The occultation data archive at MIT contains original data and analysis products of stellar occultations by the ring systems of the planets Jupiter, Saturn, Uranus, and Neptune observed by members of the group (and other groups) from 1977 to the present. During this time period, several media have been used to record and store the original and processed data: (1) chart records; (2) printed output, (3) audio reel tape; (4) audio cassette tape; (5) 7-track, 1/2-inch computer tape; (6) 9-track, 1/2-inch computer tape at 800, 1600, and 6250 bpi; (7) NOVA disk platters (2.5 and 5.0 Mbyte); (8) write once optical disks; (9) punched cards; and (10) read-write optical disks. With the rapid change of computer technology over this time period, some of these media have become not only obsolete, but nearly extinct. In particular, it has become nearly impossible to find any facilities that can still read 800 bpi tapes, which contain the only copies of several important data sets for the ring system of Uranus. In particular, we have an extensive ring data collection that includes data sets for the following Uranian ring occultations: U0, U11, U12, U13, U14, U25, U17, and U36.

  17. Ring wormholes via duality rotations

    NASA Astrophysics Data System (ADS)

    Gibbons, Gary W.; Volkov, Mikhail S.

    2016-09-01

    We apply duality rotations and complex transformations to the Schwarzschild metric to obtain wormhole geometries with two asymptotically flat regions connected by a throat. In the simplest case these are the well-known wormholes supported by phantom scalar field. Further duality rotations remove the scalar field to yield less well known vacuum metrics of the oblate Zipoy-Voorhees-Weyl class, which describe ring wormholes. The ring encircles the wormhole throat and can have any radius, whereas its tension is always negative and should be less than -c4 / 4 G. If the tension reaches the maximal value, the geometry becomes exactly flat, but the topology remains non-trivial and corresponds to two copies of Minkowski space glued together along the disk encircled by the ring. The geodesics are straight lines, and those which traverse the ring get to the other universe. The ring therefore literally produces a hole in space. Such wormholes could perhaps be created by negative energies concentrated in toroidal volumes, for example by vacuum fluctuations.

  18. Ring Beholds a Delicate Flower

    NASA Technical Reports Server (NTRS)

    2005-01-01

    NASA's Spitzer Space Telescope finds a delicate flower in the Ring Nebula, as shown in this image. The outer shell of this planetary nebula looks surprisingly similar to the delicate petals of a camellia blossom. A planetary nebula is a shell of material ejected from a dying star. Located about 2,000 light years from Earth in the constellation Lyra, the Ring Nebula is also known as Messier Object 57 and NGC 6720. It is one of the best examples of a planetary nebula and a favorite target of amateur astronomers.

    The 'ring' is a thick cylinder of glowing gas and dust around the doomed star. As the star begins to run out of fuel, its core becomes smaller and hotter, boiling off its outer layers. The telescope's infrared array camera detected this material expelled from the withering star. Previous images of the Ring Nebula taken by visible-light telescopes usually showed just the inner glowing loop of gas around the star. The outer regions are especially prominent in this new image because Spitzer sees the infrared light from hydrogen molecules. The molecules emit infrared light because they have absorbed ultraviolet radiation from the star or have been heated by the wind from the star.

    Download the QuickTime movie for the animated version of this Ring Nebula image.

  19. Ring lasers in precise measurements: A review

    SciTech Connect

    Kozubovskii, V.R.; Privalov, V.E.

    1995-05-01

    Features of the ring laser offer possibilities for various applications. The special features of frequency stabilization of ring lasers are analyzed. The employment of ring lasers in laser spectroscopy and the development of gas analytical devices on their basis are considered. It is shown that ring lasers offer some advantages for linear angular measurements and measurements of parameters of motion. Ways to optimize the parameters of ring lasers are indicated. 180 refs., 21 figs.

  20. Softened-Stainless-Steel O-Rings

    NASA Technical Reports Server (NTRS)

    Marquis, G. A.; Waters, William I.

    1993-01-01

    In fabrication of O-ring of new type, tube of 304 stainless steel bent around mandril into circle and welded closed into ring. Ring annealed in furnace to make it soft and highly ductile. In this condition, used as crushable, deformable O-ring seal. O-ring replacements used in variety of atmospheres and temperatures, relatively inexpensive, fabricated with minimum amount of work, amenable to one-of-a-kind production, reusable, and environmentally benign.

  1. On the formation of ring galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Ting; Jiang, Ing-Guey

    2011-08-01

    The formation scenario of ring galaxies is addressed in this paper. We focus on the P-type ring galaxies presented in Madore, Nelson & Petrillo (2009), particularly on the axis-symmetric ones. Our simulations show that a ring can form through the collision of disc and dwarf galaxies, and the locations, widths, and density contrasts of the ring are well determined. We find that a ring galaxy such as AM 2302-322 can be produced by this collision scenario.

  2. Controlled Ring-Opening Metathesis Polymerization by Molybdenum and Tungsten Alkylidene Complexes

    DTIC Science & Technology

    1988-07-29

    weights and low polydispersities (as low as 1.03) consistent with a living catalyst system employing 50, 100, 200, and 400 eq of monomer. The reactions are...secondary metathesis of polymer chains Bulky alkoxide ligands Wittig-like reaction Ring-opening metathesis polymerization (ROMP) Feast monomer Cyclic...olefins Retro Diels-Alder reaction Norbornene (NBE) Low temperature column chromatography Endo-,endo-5,6-dicarbomethoxynorbornene Discrete, soluble

  3. Hawking Radiation from an Acoustic Black Hole on an Ion Ring

    SciTech Connect

    Horstmann, B.; Cirac, J. I.; Reznik, B.; Fagnocchi, S.

    2010-06-25

    In this Letter we propose to simulate acoustic black holes with ions in rings. If the ions are rotating with a stationary and inhomogeneous velocity profile, regions can appear where the ion velocity exceeds the group velocity of the phonons. In these regions phonons are trapped like light in black holes, even though we have a discrete field theory and a nonlinear dispersion relation. We study the appearance of Hawking radiation in this setup and propose a scheme to detect it.

  4. Exact solution for a noncentral electric dipole ring-shaped potential in the tridiagonal representation

    SciTech Connect

    Huangfu Guoqing; Zhang Mincang

    2011-04-15

    The Schroedinger equation with noncentral electric dipole ring-shaped potential is investigated by working in a complete square integrable basis that supports an infinite tridiagonal matrix representation of the wave operator. The three-term recursion relations for the expansion coefficients of both the angular and radial wavefunctions are presented. The discrete spectrum for the bound states is obtained by the diagonalization of the radial recursion relation. Some potential applications of this system in different fields are discussed.

  5. Recent advances in discrete dipole approximation

    NASA Astrophysics Data System (ADS)

    Flatau, P. J.

    2012-12-01

    I will describe recent advances and results related to Discrete Dipole Approximation. I will concentrate on Discrete Dipole Scattering (DDSCAT) code which has been jointly developed by myself and Bruce T. Draine. Discussion will concentrate on calculation of scattering and absorption by isolated particles (e.g., dust grains, ice crystals), calculations of scattering by periodic structures with applications to studies of scattering and absorption by periodic arrangement of finite cylinders, cubes, etc), very fast near field calculation, ways to display scattering targets and their composition using three dimensional graphical codes. I will discuss possible extensions. References Flatau, P. J. and Draine, B. T., 2012, Fast near field calculations in the discrete dipole approximation for regular rectilinear grids, Optics Express, 20, 1247-1252. Draine B. T. and Flatau P. J., 2008, Discrete-dipole approximation for periodic targets: theory and tests , J. Opt. Soc. Am. A., 25, 2693-2703. Draine BT and Flatau PJ, 2012, User Guide for the Discrete Dipole Approximation Code DDSCAT 7.2, arXiv:1202.3424v3.ear field calculations (Fast near field calculations in the discrete dipole approximation for regular rectilinear grids P. J. Flatau and B. T. Draine, Optics Express, Vol. 20, Issue 2, pp. 1247-1252 (2012))

  6. Discretization of continuous features in clinical datasets

    PubMed Central

    Maslove, David M; Podchiyska, Tanya; Lowe, Henry J

    2013-01-01

    Background The increasing availability of clinical data from electronic medical records (EMRs) has created opportunities for secondary uses of health information. When used in machine learning classification, many data features must first be transformed by discretization. Objective To evaluate six discretization strategies, both supervised and unsupervised, using EMR data. Materials and methods We classified laboratory data (arterial blood gas (ABG) measurements) and physiologic data (cardiac output (CO) measurements) derived from adult patients in the intensive care unit using decision trees and naïve Bayes classifiers. Continuous features were partitioned using two supervised, and four unsupervised discretization strategies. The resulting classification accuracy was compared with that obtained with the original, continuous data. Results Supervised methods were more accurate and consistent than unsupervised, but tended to produce larger decision trees. Among the unsupervised methods, equal frequency and k-means performed well overall, while equal width was significantly less accurate. Discussion This is, we believe, the first dedicated evaluation of discretization strategies using EMR data. It is unlikely that any one discretization method applies universally to EMR data. Performance was influenced by the choice of class labels and, in the case of unsupervised methods, the number of intervals. In selecting the number of intervals there is generally a trade-off between greater accuracy and greater consistency. Conclusions In general, supervised methods yield higher accuracy, but are constrained to a single specific application. Unsupervised methods do not require class labels and can produce discretized data that can be used for multiple purposes. PMID:23059731

  7. Discrete mappings with an explicit discrete Lyapunov function related to integrable mappings

    NASA Astrophysics Data System (ADS)

    Inoue, Hironori; Takahashi, Daisuke; Matsukidaira, Junta

    2006-05-01

    We propose discrete mappings of second order that have a discrete analogue of Lyapunov function. The mappings are extensions of the integrable Quispel-Roberts-Thompson (QRT) mapping, and a discrete Lyapunov function of the mappings is identical to an explicit conserved quantity of the QRT mapping. Moreover we can obtain a differential and an ultradiscrete limit of the mappings preserving the existence of Lyapunov function. We also give applications of a mapping with an adjusted parameter, a probabilistic mapping and coupled mappings.

  8. Cassini FUV Spectral Properties of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Bradley, Eric Todd; Colwell, J. E.; Esposito, L. W.; Cuzzi, J. N.; Tollerud, H.; Chambers, L.

    2009-09-01

    Spectra taken by the Cassin Ultraviolet Imaging Spectrograph (UVIS) of Saturn's C ring, B ring, Cassini Division, and A ring have been analyzed in order to characterize ring particle regolith properties, water ice abundance in the rings, and macroscopic scattering properties. Spectra of the normalized reflectance (I/F) in all four regions show a characteristic water ice absorption feature near 1650 Å. Using only the spectral shape of the water ice absorption feature, a modified Hapke model and Shkuratov model were used to determine the asymmetry parameter and photon mean path length for the regolith associated with ice grains on ring particles. Both models assume multiple scattering between regolith grains on a given ring particle. Retrieved values of the single scattering asymmetry parameter show the regolith grains to be highly backscattering in the FUV spectral regime. Retrieved values of the photon mean path length show a strong correlation with ring brightness in the C ring but are anti-correlated with ring brightness from the inner B ring through the outer A ring. The UV slope of 1800/1500 Å (reflectance outside the water absorption ratioed to that inside the absorption band) shows that the fractional abundance of surface water ice is largest in the outer B ring and decreases by over a factor of 2 across the inner C ring. Under a single scattering assumption, we are analyzing the data to look at the ring particle phase function and albedo for measurements over a range of phase angles and will present those results.

  9. Instantaneous mode contamination and parametric combination instability of spinning cyclically symmetric ring structures with expanding application to planetary gear ring

    NASA Astrophysics Data System (ADS)

    Wang, Shiyu; Sun, Wenjia; Wang, Yaoyao

    2016-08-01

    This work addresses the free and parametric elastic vibrations of the spinning cyclically symmetric ring structures. The focus is on the instantaneous mode contamination, parametric combination instability and their connections. An analytical model is developed by using the Hamilton's principle for the in-plane bending deflection, the distinction of which is in the arbitrary distributions of the attached mass and stiffness. A special case with equally-spaced discrete mass particles and spinning springs is detailed. The uneven tangential force and the time-invariant deflection caused by the mass particles are formulated. The results imply that the order of such deflection is equal to the number of the mass particles. The instantaneous mode contamination and parametric combination instability are captured by the perturbation and superposition mode shapes of the stationary smooth ring by introducing complex coefficients. The contamination rule is similar to that of the stationary structure but the contamination strength is time-variant due to the spinning springs. New analytical results and quantitative explanations on the contamination and instability especially their connections are presented. As an application of the proposed method, the free and parametric vibrations of the planetary gear ring are formulated. Main results are demonstrated by means of the numerical simulations and compared with the existing studies.

  10. CMB lensing and giant rings

    SciTech Connect

    Rathaus, Ben; Itzhaki, Nissan E-mail: ben.rathaus@gmail.com

    2012-05-01

    We study the CMB lensing signature of a pre-inationary particle (PIP), assuming it is responsible for the giant rings anomaly that was found recently in the WMAP data. Simulating Planck-like data we find that generically the CMB lensing signal to noise ratio associated with such a PIP is quite small and it would be difficult to cross correlate the temperature giant rings with the CMB lensing signal. However, if the pre-inationary particle is also responsible for the bulk flow measured from the local large scale structure, which happens to point roughly at the same direction as the giant rings, then the CMB lensing signal to noise ratio is fairly significant.

  11. Traversable wormholes: The Roman ring

    SciTech Connect

    Visser, M.

    1997-04-01

    In this Brief Report I introduce yet another class of geometries for which semiclassical chronology protection theorems are of dubious physical reliability. I consider a {ital {open_quotes}Roman ring{close_quotes}} of traversable wormholes, wherein a number of wormholes are arranged in a ring in such a manner that no subset of wormholes is near chronology violation, though the combined system can be arbitrarily close to chronology violation. I show that (with enough wormholes in the ring) the gravitational vacuum polarization (the expectation value of the quantum stress-energy tensor) can be made arbitrarily small. In particular, the back reaction can be kept arbitrarily small all the way to the {open_quotes}reliability horizon,{close_quotes} so that semiclassical quantum gravity becomes unreliable before the gravitational back reaction becomes large. {copyright} {ital 1997} {ital The American Physical Society}

  12. Remote Sensing of Dipole Rings

    NASA Technical Reports Server (NTRS)

    Hooker, Stanford B.; Mied, Richard P.; Brown, James W.; Kirwan, A. D., Jr.

    1997-01-01

    Historical satellite-derived sea surface temperature (SST) data are reanalyzed with a zebra color palette and a thermal separatrix method. The new results from this reanalysis are as follows: (a) Thirteen observational sequences of six rings from the Gulf Stream and the Brazil Current, which have historically been interpreted as solitary vortices or monopoles are shown to have a dipolar character; (b) some of these dipole rings have been observed in the open ocean, thereby eliminating the possibility that they are sustained by topographic interactions with the continental slope; (c) whether interacting with other features or evolving as isolated circulations, dipoles are seen to rotate within a relatively narrow range of approximately 4-8 deg/day (interacting) and 10-11 deg/day (isolated); and (d) feature tracking delineates energetic fluid in both vortices and eliminates the possibility of interpreting dipole rings as transient features produced by active monopoles and patches of entrained fluid.

  13. Ring Vaccination and Smallpox Control

    PubMed Central

    van den Hof, Susan; Wallinga, Jacco; van Wijngaarden, Jan

    2004-01-01

    We present a stochastic model for the spread of smallpox after a small number of index cases are introduced into a susceptible population. The model describes a branching process for the spread of the infection and the effects of intervention measures. We discuss scenarios in which ring vaccination of direct contacts of infected persons is sufficient to contain an epidemic. Ring vaccination can be successful if infectious cases are rapidly diagnosed. However, because of the inherent stochastic nature of epidemic outbreaks, both the size and duration of contained outbreaks are highly variable. Intervention requirements depend on the basic reproduction number R0, for which different estimates exist. When faced with the decision of whether to rely on ring vaccination, the public health community should be aware that an epidemic might take time to subside even for an eventually successful intervention strategy. PMID:15200816

  14. A new systematic calibration method of ring laser gyroscope inertial navigation system

    NASA Astrophysics Data System (ADS)

    Wei, Guo; Gao, Chunfeng; Wang, Qi; Wang, Qun; Xiong, Zhenyu; Long, Xingwu

    2016-10-01

    Inertial navigation system has been the core component of both military and civil navigation systems. Before the INS is put into application, it is supposed to be calibrated in the laboratory in order to compensate repeatability error caused by manufacturing. Discrete calibration method cannot fulfill requirements of high-accurate calibration of the mechanically dithered ring laser gyroscope navigation system with shock absorbers. This paper has analyzed theories of error inspiration and separation in detail and presented a new systematic calibration method for ring laser gyroscope inertial navigation system. Error models and equations of calibrated Inertial Measurement Unit are given. Then proper rotation arrangement orders are depicted in order to establish the linear relationships between the change of velocity errors and calibrated parameter errors. Experiments have been set up to compare the systematic errors calculated by filtering calibration result with those obtained by discrete calibration result. The largest position error and velocity error of filtering calibration result are only 0.18 miles and 0.26m/s compared with 2 miles and 1.46m/s of discrete calibration result. These results have validated the new systematic calibration method and proved its importance for optimal design and accuracy improvement of calibration of mechanically dithered ring laser gyroscope inertial navigation system.

  15. Physics of Jupiter's Gossamer Rings

    NASA Astrophysics Data System (ADS)

    Hamilton, Douglas P.; Krueger, H.

    2008-05-01

    Thebe's gossamer ring, the outermost and faintest of Jupiter's rings, extends outward by at least half a jovian radius from its source satellite while maintaining a constant vertical thickness. This structure is created by an electromagnetic perturbation known as a shadow resonance (Hamilton 2003, DPS meeting #35, #11.09). A shadow resonance arises from the abrupt shutoff of photoelectric charging when a dust particle enters Jupiter's shadow which, in turn, affects the strength of the electromagnetic perturbation from the planet's intense magnetic field. The result is a coupled oscillation between a particle's orbital eccentricity and its semimajor axis. Ring material spreads outward from Thebe while maintaining its vertical thickness just as observed by Galileo imaging. In addition to cameras, the Galileo spacecraft was also equipped with dust and plasma detectors. The spacecraft made two passes through the ring and its dust detector found that 1) dust fluxes drop immediately interior to Thebe's orbit, 2) some grains have inclinations in excess of 20 degrees and 3) submicron particles are present in the Amalthea ring in much greater numbers than in the Thebe ring. These findings can all be explained in the context of our shadow resonance model: the inner boundary is a direct consequence of the conservation of the Electromagnetic Jacobi Constant, the high inclinations are forced by a vertical version of the shadow resonance, and the excess submicron particles are a consequence of the weakening of electromagnetic forces in the vicinity of synchronous orbit. In this talk, we will present the data sets as well as detailed numerical simulations that back up these claims.

  16. Hawking radiation from black rings

    SciTech Connect

    Miyamoto, Umpei; Murata, Keiju

    2008-01-15

    We calculate the quantum radiation from the 5-dimensional charged rotating black rings by demanding the radiation eliminate the possible anomalies on the horizons. It is shown that the temperature, energy flux, and angular-momentum flux exactly coincide with those of the Hawking radiation. The black rings considered in this paper contain the Myers-Perry black hole as a limit, and the quantum radiation for this black hole, obtained in the literature, is recovered in the limit. The results support the picture that the Hawking radiation can be regarded as the anomaly eliminator on horizons and suggest its general applicability to the higher-dimensional black holes discovered recently.

  17. Damping ring designs and issues

    SciTech Connect

    Wolski, Andrzej; Decking, Winfried

    2003-05-12

    The luminosity performance of a future linear collider (LC) will depend critically on the performance of the damping rings. The design luminosities of the current LC proposals require rings with very short damping times, large acceptance, low equilibrium emittance and high beam intensity. We discuss the design strategies for lattices achieving the goals of dynamical stability, examine the challenges for alignment and coupling correction, and consider a variety of collective effects that threaten to limit beam quality. We put the design goals in context by referring to the experience of operating facilities, and outline the further research and development that is needed.

  18. The "Polar Light Sign" is a useful tool to detect discrete membranous supravalvular mitral stenosis.

    PubMed

    Hertwig, Christine; Haas, Nikolaus A; Habash, Sheeraz; Hanslik, Andreas; Kececioglu, Deniz; Sandica, Eugen; Laser, Kai-Thorsten

    2015-02-01

    Mitral valve stenosis caused by a discrete supravalvular membrane is a rare congenital malformation haemodynamically leading to significant mitral valve stenosis. When the supravalvular mitral stenosis consists of a discrete supravalvular membrane adherent to the mitral valve, it is usually not clearly detectable by routine echocardiography. We report about the typical echocardiographic finding in three young patients with this rare form of a discrete membranous supravalvular stenosis caused by a membrane adherent to the mitral valve. These cases present a typical echocardiographic feature in colour Doppler generated by the pathognomonic supramitral flow acceleration. Whereas typical supravalvular mitral stenosis caused by cor triatriatum or a clearly visible supravalvular ring is easily detectable by echocardiography, a discrete supravalvular membrane adjacent to the mitral valve leaflets resembling valvular mitral stenosis is difficult to differentiate by routine echocardiography. In our opinion, this colour phenomenon does resemble the visual impression of polar lights in the northern hemisphere; owing to its typical appearance, it may therefore be named as "Polar Light Sign". This phenomenon may help to detect this anatomical entity by echocardiography in time and therefore improve the prognosis for repair.

  19. Development of a container for handling, testing, and storing discrete microelectronic components

    NASA Technical Reports Server (NTRS)

    Filip, G. L.; Caruso, S. V.

    1972-01-01

    A container has been developed for handling, testing, burning-in, and storing discrete microelectronic components without removal from the protective package. The package was designed to accommodate the leadless inverted device and other carrier-mounted active devices and chip-type discrete resistors and capacitors. Before the indicated development, components were handled and tested in various ways, some of which resulted in damage or contamination. The basic design of the container utilizes precision machined printed circuit boards and chemically milled (photoetched) contact springs. Included in this design for protection is an O-ring-sealed cover. Methods of fabrication and limitations of the current hardware are presented. Current applications of and possible extensions to the technology are discussed.

  20. Investigation on convective heat transfer over a rotating disk with discrete pins

    NASA Astrophysics Data System (ADS)

    Zhang, Jing-Zhou; Tan, Xiao-Ming; Zhu, Xing-Dan

    2014-01-01

    A three-dimensional numerical study on the flow and heat transfer characteristics over a rotating disk surface with discrete pins was conducted by the use of RNG k-ɛ turbulent model. And some experiments were also made for validation. The effects of rotating angular speed and pin configuration on the temperature maps and convective heat transfer characteristics on the rotating surface were analyzed. As the increase of rotating velocity, the impingement of pumping jet on the centre of rotating disk becomes stronger and the transition from laminar to turbulent occurs at the outer radius of rotating disk, which resulting in heat transfer enhancement. The pins on the disk make the pumping action of a rotating disk weaker. Simultaneously, they also act as perturbing elements to the cyclone flow near the rotating disk surface, making the overall heat transfer to be enhanced. The needle pins have higher convective heat transfer capacity than the discrete ring pins with the same extend pin areas.

  1. Transparent Optical Protection Ring Architectures and Applications

    NASA Astrophysics Data System (ADS)

    Li, Ming-Jun; Soulliere, Mark J.; Tebben, Daniel J.; Nederlof, Leo; Vaughn, Mark D.; Wagner, Richard E.

    2005-10-01

    This paper reviews recent progress in optical protection rings with the focus on transparent optical protection rings. Different optical protection ring architectures, such as dedicated and shared protection rings, in both the optical-channel (OCh) layer and the optical multiplex section (OMS) layer, are described. In particular, OCh shared protection rings (OChSPRINGs) are discussed in detail including node-architecture designs, ring protocols, triggers, and messaging channels. Feasibility studies and experimental results from Corning Inc. and other companies are reviewed. The paper also discusses how protection-switching times scale with number of nodes and number of wavelengths, and shows examples of applications using the scaling rules for practical optical networks such as metro, regional, and long-haul ring networks. The cost benefits of transparent optical protection rings are analyzed using a typical metro network. Finally, the paper discusses remaining issues and future developments in the optical protection ring area.

  2. Uranus' Rings: Leading up to RPX

    NASA Astrophysics Data System (ADS)

    de Pater, I.; Showalter, M.; Hammel, H.; Gibbard, S.; Lissauer, J.

    We summarize recent HST and Keck observations of the uranian ring system, taken over the past years while the viewing geometry is changing. Some highlights of our campaign to date include: i) Detection of a ring system outside of Uranus main ring system by HST (Showalter and Lissauer, Science 311, p.973, 2006), followed by color information from Keck (de Pater et al, Science 312, p.92, 2006). This system consists of two rings. The inner ring, U2, is red and relatively narrow like Saturn's G ring, while the outer ring, U1, is much broader in extent and very blue, like Saturn's E ring. Just like Enceladus is located within the E ring, moon Mab is inside U1. Saturn's E ring is most likely produced by geyser activity on Enceladus. Mab, being over 20 times smaller, is unlikely to be geologically active. However, being this small, its size is optimal to produce a ring via meteorite sputtering. ii) Detection of a ring interior to the main ring system, which might be ring 1986U2R, discovered by Voyager, though its extent and location is different from the Voyager ring. iii) Dust sheets in between the main ring. These may be similar to the dust sheets seen by Voyager in forward scattered light, yet our observations indicate large changes from the Voyager era iv) New moons were detected by HST. The orbits of some of these moons appear to be somewhat erratic. The color of moon Mab appears to be more similar to that of the large outer moons than the small inner moons. Earth will cross Uranus' ring plane three times in 2007-2008 (2 May, 16 Aug. 2007, 20 Feb. 2008), and the Sun will cross it once (7 Dec. 2007). At these times optically thin dusty rings will brighten considerably, making this period an ideal time to study Uranus' outer ring system. Between the May and August crossings, as well as between December and February, the Earth and Sun are on opposite sides of the rings, so that any optically thick rings will essentially be invisible. This allows phenomena normally

  3. On the consistency between nearest-neighbor peridynamic discretizations and discretized classical elasticity models

    DOE PAGES

    Seleson, Pablo; Du, Qiang; Parks, Michael L.

    2016-08-16

    The peridynamic theory of solid mechanics is a nonlocal reformulation of the classical continuum mechanics theory. At the continuum level, it has been demonstrated that classical (local) elasticity is a special case of peridynamics. Such a connection between these theories has not been extensively explored at the discrete level. This paper investigates the consistency between nearest-neighbor discretizations of linear elastic peridynamic models and finite difference discretizations of the Navier–Cauchy equation of classical elasticity. While nearest-neighbor discretizations in peridynamics have been numerically observed to present grid-dependent crack paths or spurious microcracks, this paper focuses on a different, analytical aspect of suchmore » discretizations. We demonstrate that, even in the absence of cracks, such discretizations may be problematic unless a proper selection of weights is used. Specifically, we demonstrate that using the standard meshfree approach in peridynamics, nearest-neighbor discretizations do not reduce, in general, to discretizations of corresponding classical models. We study nodal-based quadratures for the discretization of peridynamic models, and we derive quadrature weights that result in consistency between nearest-neighbor discretizations of peridynamic models and discretized classical models. The quadrature weights that lead to such consistency are, however, model-/discretization-dependent. We motivate the choice of those quadrature weights through a quadratic approximation of displacement fields. The stability of nearest-neighbor peridynamic schemes is demonstrated through a Fourier mode analysis. Finally, an approach based on a normalization of peridynamic constitutive constants at the discrete level is explored. This approach results in the desired consistency for one-dimensional models, but does not work in higher dimensions. The results of the work presented in this paper suggest that even though nearest

  4. PREFACE: 4th Symposium on Prospects in the Physics of Discrete Symmetries (DISCRETE2014)

    NASA Astrophysics Data System (ADS)

    Di Domenico, Antonio; Mavromatos, Nick E.; Mitsou, Vasiliki A.; Skliros, Dimitri P.

    2015-07-01

    The DISCRETE 2014: Fourth Symposium in the Physics of Discrete Symmetries took place at King's College London, Strand Campus, London WC2R 2LS, from Tuesday, December 2 2014 till Saturday, December 6 2014. This is the fourth Edition of the DISCRETE conference series, which is a biannual event, having been held previously in Valencia (Discrete'08), Rome (Discrete2010) and Lisbon (Discrete2012). The topics covered at the DISCRETE series of conferences are: T, C, P, CP symmetries; accidental symmetries (B, L conservation); CPT symmetry, decoherence and entangled states, Lorentz symmetry breaking (phenomenology and current bounds); neutrino mass and mixing; implications for cosmology and astroparticle physics, dark matter searches; experimental prospects at LHC, new facilities. In DISCRETE 2014 we have also introduced two new topics: cosmological aspects of non-commutative space-times as well as PT symmetric Hamiltonians (non-Hermitian but with real eigenvalues), a topic that has wide applications in particle physics and beyond. The conference was opened by the King's College London Vice Principal on Research and Innovation, Mr Chris Mottershead, followed by a welcome address by the Chair of DISCRETE 2014 (Professor Nick E. Mavromatos). After these introductory talks, the scientific programme of the DISCRETE 2014 symposium started. Following the tradition of DISCRETE series of conferences, the talks (138 in total) were divided into plenary-review talks (25), invited research talks (50) and shorter presentations (63) — selected by the conveners of each session in consultation with the organisers — from the submitted abstracts. We have been fortunate to have very high-quality, thought stimulating and interesting talks at all levels, which, together with the discussions among the participants, made the conference quite enjoyable. There were 152 registered participants for the event.

  5. INVITED TALK: Dynamics Of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.

    2011-04-01

    Planetary rings are the only nearby astrophysical disks, and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 1e-7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close-range and in real-time in planetary rings. We will review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We will then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk), and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally-confined arcs both at Saturn, Jupiter, and Neptune. Finally, every known ring system includes a substantial component of diffuse dusty rings.

  6. An implicit finite element method for discrete dynamic fracture

    SciTech Connect

    Gerken, Jobie M.

    1999-12-01

    A method for modeling the discrete fracture of two-dimensional linear elastic structures with a distribution of small cracks subject to dynamic conditions has been developed. The foundation for this numerical model is a plane element formulated from the Hu-Washizu energy principle. The distribution of small cracks is incorporated into the numerical model by including a small crack at each element interface. The additional strain field in an element adjacent to this crack is treated as an externally applied strain field in the Hu-Washizu energy principle. The resulting stiffness matrix is that of a standard plane element. The resulting load vector is that of a standard plane element with an additional term that includes the externally applied strain field. Except for the crack strain field equations, all terms of the stiffness matrix and load vector are integrated symbolically in Maple V so that fully integrated plane stress and plane strain elements are constructed. The crack strain field equations are integrated numerically. The modeling of dynamic behavior of simple structures was demonstrated within acceptable engineering accuracy. In the model of axial and transverse vibration of a beam and the breathing mode of vibration of a thin ring, the dynamic characteristics were shown to be within expected limits. The models dominated by tensile forces (the axially loaded beam and the pressurized ring) were within 0.5% of the theoretical values while the shear dominated model (the transversely loaded beam) is within 5% of the calculated theoretical value. The constant strain field of the tensile problems can be modeled exactly by the numerical model. The numerical results should therefore, be exact. The discrepancies can be accounted for by errors in the calculation of frequency from the numerical results. The linear strain field of the transverse model must be modeled by a series of constant strain elements. This is an approximation to the true strain field, so some

  7. Initial Cassini Ultraviolet Observations of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Colwell, J. E.

    2004-12-01

    The first ring occultation to be observed by Cassini is of the star Xi Ceti on October 6-7, 2004, from a distance of 6.22 million km. The Ultraviolet Imaging Spectrograph (UVIS) includes a High Speed Photometer with a bandpass of ˜110-190 nm that has an integration period of 8 msec for this observation. The Fresnel zone at this distance is ˜40 m, and the speed of the occultation gives a radial sampling interval of 5-8 m. The occultation covers the C ring, Cassini Division, A ring, and F ring. The occultation is particularly well-suited for the low to intermediate optical depth regions of the C and F rings and the Cassini Division, and will have lower effective resolution in the higher optical depth regions of the A ring. The Xi Ceti occultation is by far the most distant that Cassini will observe. Ultraviolet spectral reflectance observations were also made at Saturn Orbit Insertion on July 1, 2004, providing the highest spatial resolution UV reflectance of the rings, with a 150 km effective resolution. Spectral variations are seen between the C, B, and A rings and the Cassini Division indicating varying amounts of dark material mixed in with water ice in the rings. The A ring is significantly brighter than the B and C rings, and its brightness increases with increasing radial distance. Meteoroid impacts into the rings darken the rings through the addition of silicates and carbonaceous material. Observed fluctuations in the UV brightness at length scales of less than 3000 km can be explained by impact fragmentation of moonlets or large ring particles in the rings. These fragmentation events expose relatively pure ice from the interior of the moonlet, leading to a local brightening of the ring which is gradually reduced and mixed with the surrounding ring material as the meteoroid bombardment continues. We will present our initial findings on ring structure, UV brightness, and particle sizes.

  8. Dynamics of a Discretely Reinforced Cylindrical Shell Under a Local Impulsive Load

    NASA Astrophysics Data System (ADS)

    Lugovoi, P. Z.; Sirenko, V. N.; Skosarenko, Yu. V.; Batutina, T. Ya.

    2017-03-01

    A procedure and software for studying the dynamics of a reinforced cylindrical shell on an elastic foundation are developed. The shell is under local loads distributed over small areas and varying linearly during a short time. The stringers are described by a structurally orthotropic model and the ring ribs by a discrete model. The candidate solution is expanded into series of natural modes. The influence of a local load on the deformation parameters of the shell is studied using a test example. Conclusions on the effect of the pulse shape, the time of action of the external forces, and the reinforcement on the strain state of the shell are drawn

  9. Propagation of short stress pulses in discrete strongly nonlinear tunable metamaterials.

    PubMed

    Xu, Yichao; Nesterenko, Vitali F

    2014-08-28

    The propagation of short pulses with wavelength comparable to the size of a unit cell has been studied in a one-dimensional discrete metamaterial composed of steel discs alternating with toroidal nitrile O-rings under different levels of precompression using experiments, numerical simulations and theoretical analysis. This strongly nonlinear metamaterial is more tunable than granular chains composed of linear elastic spherical particles and has better potential for attenuation of dynamic loads. A double power-law relationship for compressed O-rings was found to describe adequately their quasi-static and dynamic behaviour with significantly different elastic moduli. It is demonstrated that the double power-law metamaterial investigated allows a dramatic increase in sound speed and acoustic impedance of three to four times using a moderate force.

  10. Signet ring cell carcinoma in urine cytology: cytomorphologic findings and differential diagnosis.

    PubMed

    Guan, Hui; Tatsas, Armanda D; Ali, Syed Z

    2012-01-01

    Signet ring carcinoma is an exceedingly rare and aggressive variant of primary bladder carcinoma. The cytomorphologic features of this rare entity in urinary specimens have not been well characterized. Twenty-seven cases of signet ring cell carcinoma of the urinary bladder were identified from the pathology archives of The Johns Hopkins Hospital (1989-2011). Of these, 6 cases with prior urinary cytology specimens were studied. There were 5 males and 1 female, with a mean age of 62 years. The presenting complaints included hematuria with or without symptoms of bladder irritation. Histopathologically, there were 5 cases of primary bladder carcinoma and 1 case of metastatic colonic signet ring cell carcinoma. The salient cytomorphologic features included scattered malignant epithelial cells, displaying distinct cell borders, abundant cytoplasm with a single large, discrete mucin vacuole, and eccentric irregular nuclei with prominent nucleoli. Primary adenocarcinoma additionally revealed a few intact malignant glandular epithelial fragments. Metastatic colonic signet ring cell carcinoma displayed predominantly singly dispersed malignant cells with eccentrically placed, oval nuclei with occasional small nucleoli and a moderate amount of vacuolated cytoplasm. Signet ring cell carcinomas are rarely encountered in urinary cytology. The differential diagnosis includes distended histiocytes or degenerated urothelial cells, primary signet ring cell carcinoma, and metastatic adenocarcinoma. Copyright © 2012 S. Karger AG, Basel.

  11. Linitis plastica like primary signet ring cell carcinoma of the gallbladder - an extremely rare variant.

    PubMed

    Agarwal, S; Pandey, P; Durgapal, P; Krishna, M

    2016-12-01

    Signet ring carcinoma (SRCC) of gallbladder is an extremely rare tumor accounting for approximately 3% of all gallbladder carcinomas, with a handful of case reports in the literature. We report a case of signet ring cell carcinoma of the gallbladder in a 70 year-old female who was operated upon after the preoperative diagnosis of cholecystitis with cholelithiasis, based on ultrasonographic findings and subsequently diagnosed as signet ring cell carcinoma of the gallbladder on histopathological examination. Grossly there was no discrete growth, instead tumor presented as linitis plastica like diffuse thickening of the gallbladder wall. Microscopic examination revealed a diffusely infiltrative carcinoma comprised exclusively of signet ring cells and confirmed by periodic acid-Schiff (PAS), Alcian blue & Cytokeratin 7 stains. Post -operative clinico-radiological workup was done to exclude secondary. This highly aggressive signet ring cell carcinoma of gallbladder is being reported because of its rarity, its unique histomorphological features and diagnostic inadequacy of the routinely performed ultrasonography as well as highlighting the use of special stains and immunohistochemistry to exclude other possibilities. Our case highlights that routine histopathological examination of all the cholecystectomy specimens is a must to facilitate the early diagnosis of aggressive signet ring cell carcinoma gallbladder. © Copyright Società Italiana di Anatomia Patologica e Citopatologia Diagnostica, Divisione Italiana della International Academy of Pathology.

  12. The EMMA Main Ring Lattice.

    SciTech Connect

    Berg,J.S.

    2008-02-21

    I give a brief introduction to the purpose and goals of the EMMA experiment and describe how they will impact the design of the main EMMA ring. I then describe the mathematical model that is used to describe the EMMA lattice. Finally, I show how the different lattice configurations were obtained and list their parameters.

  13. Conical O-ring seal

    DOEpatents

    Chalfant, G.G. Jr.

    A shipping container for radioactive or other hazardous materials has a conical-shaped closure containing grooves in the conical surface thereof and an O-ring seal incorporated in each of such grooves. The closure and seal provide a much stronger, tighter and compact containment than with a conventional flanged joint.

  14. Stirring properties of vortex rings

    NASA Astrophysics Data System (ADS)

    Auerbach, David

    1991-05-01

    Ring vortex evolution, from the initial roll-up phase through to the final turbulent phase, was experimentally studied to see the dependence of its stirring properties on both the initial (accelerating, constant, decelerating, slow, fast) piston motion as well as on the boundary (tube/hole geometry) conditions. Stirring between fluid initially upstream and that initially downstream of the nozzle plane is done more by convective entrainment at the beginning (roll-up and contraction phases), by diffusive entrainment during the laminar and wavy phases, and by mixed entrainment and ejection during the transition to turbulence and the turbulent phase itself. During vortex roll-up, it was found that tubes eject shorter streaklines than do holes, and that there is less Re dependence for this for tubes than for holes. During the contraction phase, entrainment ends, save for minimal entrainment due to axial inflow into the ring from along the cores of Goertler-type vortices. Generally, the rate of fluid ejected is largest during the transition from the wavy to the turbulent state. As far as the stability of the vortices is concerned, rings generated at holes are less stable than those generated at tubes. During the final turbulent phase, rings not only entrain fluid but eject it periodically into the wake: Between two and four hairpin vortices are generated and laid off in the wake during each ejection. The frequency at which such ejections takes place scales as a Strouhal number that takes on values of between 2 and 4.

  15. Barred Ring Galaxy NGC 1291

    NASA Image and Video Library

    2005-05-05

    This ultraviolet image left and visual image right from NASA Galaxy Evolution Explorer is of the barred ring galaxy NGC 1291. The VIS image is dominated by the inner disk and bar. The UV image is dominated by the low surface brightness outer arms.

  16. Conical O-ring seal

    DOEpatents

    Chalfant, Jr., Gordon G.

    1984-01-01

    A shipping container for radioactive or other hazardous materials which has a conical-shaped closure containing grooves in the conical surface thereof and an O-ring seal incorporated in each of such grooves. The closure and seal provide a much stronger, tighter and compact containment than with a conventional flanged joint.

  17. On the vortex ring state

    NASA Astrophysics Data System (ADS)

    Green, Richard; Gillies, E.; Giuni, M.; Hislop, J.; Savas, Omer

    2014-11-01

    The investigation considers the vortex ring state, a phenomenon normally associated with the collapse of a trailing, helical vortex wake into a unstable vortex ring, and is a problem encountered when a helicopter rotor descends into its own wake. A series of wind tunnel and towing tank experiments on rotor systems have been performed, and a comparison is then made with the behaviour of a specially designed open core, annular jet system that generates a mean flow velocity profile similar to that observed below a rotor. In experimentally simulated descents the jet system forms flow patterns that are topologically similar to the vortex ring state of a rotor system. Furthermore the dynamic behaviour of the flow shares many of the important characteristics of the rotor flow. This result suggests that the phenomenon of the vortex ring state of a rotor wake is decoupled from the detailed vortex dynamics of the helical vortex filaments themselves. The presentation will describe the principle behind the investigation, the details of the annular jet system and the results gained using PIV and flow visualisation of the wake and jet systems.

  18. RHIC Ring Element Nomenclature System

    SciTech Connect

    Hahn, H.; Rufer, C.; Sondericker, J.

    1990-10-11

    A technical note was published by Hahn, in March 1985, that presented a nomenclature system which identified RHIC main magnets and their position in the ring structure. A revised nomenclature system is described in this technical note which supersedes the earlier version. This present designation completes the 1985 note and has been enlarged to take into account practical considerations like machine installation and operation.

  19. Looking for rings and things

    NASA Astrophysics Data System (ADS)

    Kenworthy, Matthew

    2017-04-01

    It's not often that an astronomical object gets its own dedicated observatory, but as the planet Beta Pictoris b moves in front of its host star, its every move will be watched by bRing, eager to discover more about the planet's Hill sphere, explains Matthew Kenworthy.

  20. Baroclinic Structure of Oceanic Rings

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Sun, C.

    One of the most important analytical solutions to the two dimensional incompressible flow is circular Rankin vortex that has a solid-body core and an approximately irrotational far field. For an f-plane rotating flow, Ingersoll (1969) presented a closed-form ring solution superposed with a zonal flow. So far most studies have been concerned with two dimensional and barotropic situations.