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Sample records for co-cultivated damp building

  1. Co-cultivated damp building related microbes Streptomyces californicus and Stachybotrys chartarum induce immunotoxic and genotoxic responses via oxidative stress.

    PubMed

    Markkanen Penttinen, Piia; Pelkonen, Jukka; Tapanainen, Maija; Mäki-Paakkanen, Jorma; Jalava, Pasi I; Hirvonen, Maija-Riitta

    2009-08-01

    Oxidative stress has been proposed to be one mechanism behind the adverse health outcomes associated with living in a damp indoor environment. In the present study, the capability of damp building-related microbes Streptomyces californicus and Stachybotrys chartarum to induce oxidative stress was evaluated in vitro. In addition, the role of oxidative stress in provoking the detected cytotoxic, genotoxic, and inflammatory responses was studied by inhibiting the production of reactive oxygen species (ROS) using N-acetyl-l-cysteine (NAC). RAW264.7 macrophages were exposed in a dose- and time-dependent manner to the spores of co-cultivated S. californicus and S. chartarum, to their separately cultivated spore-mixture, or to the spores of these microbes alone. The intracellular peroxide production and cytotoxicity were measured by flow cytometric analysis, nitric oxide production was analyzed by the Griess method, DNA damage was determined by the comet assay, and cytokine production was measured by an immunochemical ELISA (enzyme-linked immunosorbent assay). All the studied microbial exposures triggered oxidative stress and subsequent cellular damage in RAW264.7 macrophages. The ROS scavenger, NAC, prevented growth arrest, apoptosis, DNA damage, and cytokine production induced by the co-culture since it reduced the intracellular level of ROS within macrophages. In contrast, the DNA damage and cell cycle arrest induced by the spores of S. californicus alone could not be prevented by NAC. Bioaerosol-induced oxidative stress in macrophages may be an important mechanism behind the frequent respiratory symptoms and diseases suffered by residents of moisture damaged buildings. Furthermore, microbial interactions during co-cultivation stimulate the production of highly toxic compound(s) which may significantly increase oxidative damage.

  2. Elastic seismic response of building with supplemental damping

    SciTech Connect

    Ashour, S.A.

    1987-01-01

    Supplemental damping devices can add significant amounts of energy dissipation in buildings. While most previous studies of the earthquake response of buildings were confined to the small damping inherent in structural and nonstructural components, the consequences of adding from 10 to 150% of critical damping as supplemental damping on the elastic response behavior of buildings is studied. Th study is divided into three parts: single degree-of-freedom systems, multidegree-of-freedom systems, and distributed-parameter systems. For single degree-of-freedom systems, a relationship between seismic-displacement response and the amount of damping was established. Similarly, a relationship between the commonly used pseudo-spectral acceleration and the actual absolute acceleration was established for these higher-damping cases. The consequences of adding supplemental damping in multistory buildings was studied using simply coupled stiffness systems as well as using beam and column flexibilities. The displacement and energy component responses were used to develop an understanding of the behavior of buildings with large damping. The optimum distribution of supplemental damping in a building for the highest efficiency of damper utilization was studied using a distributed-parameter system.

  3. Investigation of superstructure damping identification for the HDR containment building

    SciTech Connect

    Hsieh, B.J.; Kot, C.A.; Srinivasan, M.G.

    1985-01-01

    A method for the estimation of first mode structural damping, developed by other investigators, was applied to shaker test data of the HDR containment building. Due to inadequate precision in the experimental phase measurements no valid results could be obtained. Based on modal analysis it was also noted that for systems such as the HDR building, contributions of higher modes are not negligible as was assumed in the original approach. Therefore, the procedure for the determination of superstructure damping using experimental data was extended to include the effects of higher modes. The extended method does not lead to any higher order nonlinear equations than the first mode approximation and was found to be as simple to apply as the original approach.

  4. Secondary metabolites from Penicillium corylophilum isolated from damp buildings.

    PubMed

    McMullin, David R; Nsiama, Tienabe K; Miller, J David

    2014-01-01

    Indoor exposure to the spores and mycelial fragments of fungi that grow on damp building materials can result in increased non-atopic asthma and upper respiratory disease. The mechanism appears to involve exposure to low doses of fungal metabolites. Penicillium corylophilum is surprisingly common in damp buildings in USA, Canada and western Europe. We examined isolates of P. corylophilum geographically distributed across Canada in the first comprehensive study of secondary metabolites of this fungus. The sesquiterpene phomenone, the meroterpenoids citreohybridonol and andrastin A, koninginin A, E and G, three new alpha pyrones and four new isochromans were identified from extracts of culture filtrates. This is the first report of koninginins, meroterpenoids and alpha pyrones from P. corylophilum. These secondary metabolite data support the removal of P. corylophilum from Penicillium section Citrina and suggest that further taxonomic studies are required on this species.

  5. Methods for elimination of dampness in Building walls

    NASA Astrophysics Data System (ADS)

    Campian, Cristina; Pop, Maria

    2016-06-01

    Dampness elimination in building walls is a very sensitive problem, with high costs. Many methods are used, as: chemical method, electro osmotic method or physical method. The RECON method is a representative and a sustainable method in Romania. Italy has the most radical method from all methods. The technology consists in cutting the brick walls, insertion of a special plastic sheeting and injection of a pre-mixed anti-shrinking mortar.

  6. Dampness in buildings and health. Nordic interdisciplinary review of the scientific evidence on associations between exposure to "dampness" in buildings and health effects (NORDDAMP).

    PubMed

    Bornehag, C G; Blomquist, G; Gyntelberg, F; Järvholm, B; Malmberg, P; Nordvall, L; Nielsen, A; Pershagen, G; Sundell, J

    2001-06-01

    Several epidemiological investigations concerning indoor environments have indicated that "dampness" in buildings is associated to health effects such as respiratory symptoms, asthma and allergy. The aim of the present interdisciplinary review is to evaluate this association as shown in the epidemiological literature. A literature search identified 590 peer-reviewed articles of which 61 have been the foundation for this review. The review shows that "dampness" in buildings appears to increase the risk for health effects in the airways, such as cough, wheeze and asthma. Relative risks are in the range of OR 1.4-2.2. There also seems to be an association between "dampness" and other symptoms such as tiredness, headache and airways infections. It is concluded that the evidence for a causal association between "dampness" and health effects is strong. However, the mechanisms are unknown. Several definitions of dampness have been used in the studies, but all seems to be associated with health problems. Sensitisation to mites may be one but obviously not the only mechanism. Even if the mechanisms are unknown, there is sufficient evidence to take preventive measures against dampness in buildings.

  7. Comparison of damping in buildings under low-amplitude and strong motions

    USGS Publications Warehouse

    Celebi, M.

    1996-01-01

    This paper presents a comprehensive assessment of damping values and other dynamic characteristics of five buildings using strong-motion and low-amplitude (ambient vibration) data. The strong-motion dynamic characteristics of five buildings within the San Francisco Bay area are extracted from recordings of the 17 October 1989 Loma Prieta earthquake (LPE). Ambient vibration response characteristics for the same five buildings were inferred using data collected in 1990 following LPE. Additional earthquake data other than LPE for one building and ambient vibration data collected before LPE for two other buildings provide additional confirmation of the results obtained. For each building, the percentages of critical damping and the corresponding fundamental periods determined from low-amplitude test data are appreciably lower than those determined from strong-motion recordings. These differences are attributed mainly to soil-structure interaction and other non-linear behavior affecting the structures during strong shaking. Significant contribution of radiation damping to the effective damping of a specific building is discussed in detail.

  8. Highly-Damped Spectral Acceleration as a Ground Motion Intensity Measure for Estimating Collapse Vulnerability of Buildings

    NASA Astrophysics Data System (ADS)

    Buyco, K.; Heaton, T. H.

    2016-12-01

    Current U.S. seismic code and performance-based design recommendations quantify ground motion intensity using 5%-damped spectral acceleration when estimating the collapse vulnerability of buildings. This intensity measure works well for predicting inter-story drift due to moderate shaking, but other measures have been shown to be better for estimating collapse risk.We propose using highly-damped (>10%) spectral acceleration to assess collapse vulnerability. As damping is increased, the spectral acceleration at a given period T begins to behave like a weighted average of the corresponding lowly-damped (i.e. 5%) spectrum at a range of periods. Weights for periods longer than T increase as damping increases. Using high damping is physically intuitive for two reasons. Firstly, ductile buildings dissipate a large amount of hysteretic energy before collapse and thus behave more like highly-damped systems. Secondly, heavily damaged buildings experience period-lengthening, giving further credence to the weighted-averaging property of highly-damped spectral acceleration.To determine the optimal damping value(s) for this ground motion intensity measure, we conduct incremental dynamic analysis for a suite of ground motions on several different mid-rise steel buildings and select the damping value yielding the lowest dispersion of intensity at the collapse threshold. Spectral acceleration calculated with damping as high as 70% has been shown to be a better indicator of collapse than that with 5% damping.

  9. Seismic damage diagnosis of a masonry building using short-term damping measurements

    NASA Astrophysics Data System (ADS)

    Kouris, Leonidas Alexandros S.; Penna, Andrea; Magenes, Guido

    2017-04-01

    It is of considerable importance to perform dynamic identification and detect damage in existing structures. This paper describes a new and practical method for damage diagnosis of masonry buildings requiring minimum computational effort. The method is based on the relative variation of modal damping and validated against experimental data from a full scale two storey shake table test. The experiment involves a building subjected to uniaxial vibrations of progressively increasing intensity at the facilities of EUCENTRE laboratory (Pavia, Italy) up to a near collapse damage state. Five time-histories are applied scaling the Montenegro (1979) accelerogram. These strong motion tests are preceded by random vibration tests (RVT's) which are used to perform modal analysis. Two deterministic methods are applied: the single degree of freedom (SDOF) assumption together with the peak-picking method in the discrete frequency domain and the Eigen realisation algorithm with data correlations (ERA-DC) in the discrete time domain. Regarding the former procedure, some improvements are incorporated to locate rigorously the natural frequencies and estimate the modal damping. The progressive evolution of the modal damping is used as a key indicator to characterise damage on the building. Modal damping is connected to the structural mass and stiffness. A square integrated but only with two components expression for proportional (classical) damping is proposed to fit better with the experimental measurements of modal damping ratios. Using this Rayleigh order formulation the contribution of each of the damping components is evaluated. The stiffness component coefficient is proposed as an effective index to detect damage and quantify its intensity.

  10. Effect of Damping and Yielding on the Seismic Response of 3D Steel Buildings with PMRF

    PubMed Central

    Haldar, Achintya; Rodelo-López, Ramon Eduardo; Bojórquez, Eden

    2014-01-01

    The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions. PMID:25097892

  11. Effect of damping and yielding on the seismic response of 3D steel buildings with PMRF.

    PubMed

    Reyes-Salazar, Alfredo; Haldar, Achintya; Rodelo-López, Ramon Eduardo; Bojórquez, Eden

    2014-01-01

    The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions.

  12. STACHYBOTRYS CHARTARU Trichothecene Mycotoxins and Damp Building-Related Illness: New Insights into a Public Health Enigma

    EPA Science Inventory

    Damp building-related illnesses (DBRI) include a myriad of respiratory, immunologic, and neurologic symptoms that are sometimes etiologically linked to aberrant indoor growth of the toxic black mold, Stachybotrys chartarum. Although supportive evidence for such linkages is limite...

  13. STACHYBOTRYS CHARTARU Trichothecene Mycotoxins and Damp Building-Related Illness: New Insights into a Public Health Enigma

    EPA Science Inventory

    Damp building-related illnesses (DBRI) include a myriad of respiratory, immunologic, and neurologic symptoms that are sometimes etiologically linked to aberrant indoor growth of the toxic black mold, Stachybotrys chartarum. Although supportive evidence for such linkages is limite...

  14. Building dampness and mold in European homes in relation to climate, building characteristics and socio-economic status: The European Community Respiratory Health Survey ECRHS II.

    PubMed

    Norbäck, D; Zock, J-P; Plana, E; Heinrich, J; Tischer, C; Jacobsen Bertelsen, R; Sunyer, J; Künzli, N; Villani, S; Olivieri, M; Verlato, G; Soon, A; Schlünssen, V; Gunnbjörnsdottir, M I; Jarvis, D

    2017-09-01

    We studied dampness and mold in homes in relation to climate, building characteristics and socio-economic status (SES) across Europe, for 7127 homes in 22 centers. A subsample of 3118 homes was inspected. Multilevel analysis was applied, including age, gender, center, SES, climate, and building factors. Self-reported water damage (10%), damp spots (21%), and mold (16%) in past year were similar as observed data (19% dampness and 14% mold). Ambient temperature was associated with self-reported water damage (OR=1.63 per 10°C; 95% CI 1.02-2.63), damp spots (OR=2.95; 95% CI 1.98-4.39), and mold (OR=2.28; 95% CI 1.04-4.67). Precipitation was associated with water damage (OR=1.12 per 100 mm; 95% CI 1.02-1.23) and damp spots (OR=1.11; 95% CI 1.02-1.20). Ambient relative air humidity was not associated with indoor dampness and mold. Older buildings had more dampness and mold (P<.001). Manual workers reported less water damage (OR=0.69; 95% CI 0.53-0.89) but more mold (OR=1.27; 95% CI 1.03-1.55) as compared to managerial/professional workers. There were correlations between reported and observed data at center level (Spearman rho 0.61 for dampness and 0.73 for mold). In conclusion, high ambient temperature and precipitation and high building age can be risk factors for dampness and mold in homes in Europe. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  15. Microfungal contamination of damp buildings--examples of risk constructions and risk materials.

    PubMed Central

    Gravesen, S; Nielsen, P A; Iversen, R; Nielsen, K F

    1999-01-01

    To elucidate problems with microfungal infestation in indoor environments, a multidisciplinary collaborative pilot study, supported by a grant from the Danish Ministry of Housing and Urban Affairs, was performed on 72 mold-infected building materials from 23 buildings. Water leakage through roofs, rising damp, and defective plumbing installations were the main reasons for water damage with subsequent infestation of molds. From a score system assessing the bioavailability of the building materials, products most vulnerable to mold attacks were water damaged, aged organic materials containing cellulose, such as wooden materials, jute, wallpaper, and cardboard. The microfungal genera most frequently encountered were Penicillium (68%), Aspergillus (56%), Chaetomium (22%), Ulocladium, (21%), Stachybotrys (19%) and Cladosporium (15%). Penicillium chrysogenum, Aspergillus versicolor, and Stachybotrys chartarum were the most frequently occurring species. Under field conditions, several trichothecenes were detected in each of three commonly used building materials, heavily contaminated with S. chartarum. Under experimental conditions, four out of five isolates of S. chartarum produced satratoxin H and G when growing on new and old, very humid gypsum boards. A. versicolor produced the carcinogenic mycotoxin sterigmatocystin and 5-methoxysterigmatocystin under the same conditions. PMID:10347000

  16. Effectiveness of damped braces to mitigate seismic torsional response of unsymmetric-plan buildings

    NASA Astrophysics Data System (ADS)

    Mazza, Fabio; Pedace, Emilia; Favero, Francesco Del

    2017-02-01

    The seismic retrofitting of unsymmetric-plan reinforced concrete (r.c.) framed buildings can be carried out by the incorporation of damped braces (DBs). Yet most of the proposals to mitigate the seismic response of asymmetric framed buildings by DBs rest on the hypothesis of elastic (linear) structural response. The aim of the present work is to evaluate the effectiveness and reliability of a Displacement-Based Design procedure of hysteretic damped braces (HYDBs) based on the nonlinear behavior of the frame members, which adopts the extended N2 method considered by Eurocode 8 to evaluate the higher mode torsional effects. The Town Hall of Spilinga (Italy), a framed structure with an L-shaped plan built at the beginning of the 1960s, is supposed to be retrofitted with HYDBs to attain performance levels imposed by the Italian seismic code (NTC08) in a high-risk zone. Ten structural solutions are compared by considering two in-plan distributions of the HYDBs, to eliminate (elastic) torsional effects, and different design values of the frame ductility combined with a constant design value of the damper ductility. A computer code for the nonlinear dynamic analysis of r.c. spatial framed structures is adopted to evaluate the critical incident angle of bidirectional earthquakes. Beams and columns are simulated with a lumped plasticity model, including flat surface modeling of the axial load-biaxial bending moment elastic domain at the end sections, while a bilinear law is used to idealize the behavior of the HYDBs. Damage index domains are adopted to estimate the directions of least seismic capacity, considering artificial earthquakes whose response spectra match those adopted by NTC08 at serviceability and ultimate limit states.

  17. Simplified seismic collapse capacity-based evaluation and design of frame buildings with and without supplemental damping systems

    NASA Astrophysics Data System (ADS)

    Hamidia, Mohammad Javad

    A simplified procedure is developed for estimating the seismic sidesway collapse capacity of frame building structures. The procedure is then extended to quantify the seismic collapse capacity of buildings incorporating supplemental damping systems. The proposed procedure is based on a robust database of seismic peak displacement responses of viscously damped nonlinear single-degree-of-freedom systems for various seismic intensities and uses nonlinear static (pushover) analysis without the need for nonlinear time history dynamic analysis. The proposed procedure is assessed by comparing its collapse capacity predictions on 1470 different building models with those obtained from incremental nonlinear dynamic analyses. A straightforward unifying collapse capacity based design procedure aimed at achieving a pre-determined probability of collapse under maximum considered earthquake event is also introduced for structures equipped with viscous dampers (linear and nonlinear) and hysteretic dampers. The proposed simplified procedure offers a simple, yet efficient, computational/analytical tool that is capable of predicting collapse capacities with acceptable accuracy for a wide variety of frame building structures incorporate several types of supplemental damping systems.

  18. Dampness, food habits, and sick building syndrome symptoms in elementary school pupils.

    PubMed

    Saijo, Yasuaki; Nakagi, Yoshihiko; Ito, Toshihiro; Sugioka, Yoshihiko; Endo, Hitoshi; Yoshida, Takahiko

    2010-09-01

    We investigated dampness/mold in schools and dwellings, and food habits and subjective symptoms in elementary school pupils, in order to clarify the effect of dampness and food habits on subjective symptoms in elementary school pupils. Questionnaires were used to investigate dampness in classrooms and dwellings in Hokkaido, Japan, and its effect on subjective symptoms in 1,077 pupils in 8 elementary schools. We used a dampness index for both the home and classroom; the index was the sum of the presence of four dampness indicators: (1) visible mold, (2) moldy odor, (3) water leakage, and (4) condensation on windowpanes. The questionnaire also contained queries about food habits, as follows: the frequency of eating breakfast, whether the energy provided by the school lunch was sufficient, and whether eating too many snacks and/or sweets were consumed. Adjusted logistic regression was used to determine whether dampness and food habits were related to the subjective symptoms. In fully adjusted models, the home dampness index was significantly related to cough, general symptoms, and having at least one symptom; the classroom dampness index was significantly related to nasal symptoms. In addition, usually not eating breakfast was significantly related to eye symptoms, and too many snacks and/or sweets was significantly related to eye, nasal, and general symptoms. Both home and classroom dampness can affect pupils' health. Home dampness, in particular, was significantly related to cough and general symptoms, and classroom dampness was significantly related to nasal symptoms. Furthermore, favorable food habits have a positive effect on pupils' subjective symptoms.

  19. Dampness, food habits, and sick building syndrome symptoms in elementary school pupils

    PubMed Central

    Nakagi, Yoshihiko; Ito, Toshihiro; Sugioka, Yoshihiko; Endo, Hitoshi; Yoshida, Takahiko

    2010-01-01

    Objectives We investigated dampness/mold in schools and dwellings, and food habits and subjective symptoms in elementary school pupils, in order to clarify the effect of dampness and food habits on subjective symptoms in elementary school pupils. Methods Questionnaires were used to investigate dampness in classrooms and dwellings in Hokkaido, Japan, and its effect on subjective symptoms in 1,077 pupils in 8 elementary schools. We used a dampness index for both the home and classroom; the index was the sum of the presence of four dampness indicators: (1) visible mold, (2) moldy odor, (3) water leakage, and (4) condensation on windowpanes. The questionnaire also contained queries about food habits, as follows: the frequency of eating breakfast, whether the energy provided by the school lunch was sufficient, and whether eating too many snacks and/or sweets were consumed. Adjusted logistic regression was used to determine whether dampness and food habits were related to the subjective symptoms. Results In fully adjusted models, the home dampness index was significantly related to cough, general symptoms, and having at least one symptom; the classroom dampness index was significantly related to nasal symptoms. In addition, usually not eating breakfast was significantly related to eye symptoms, and too many snacks and/or sweets was significantly related to eye, nasal, and general symptoms. Conclusions Both home and classroom dampness can affect pupils’ health. Home dampness, in particular, was significantly related to cough and general symptoms, and classroom dampness was significantly related to nasal symptoms. Furthermore, favorable food habits have a positive effect on pupils’ subjective symptoms. PMID:21432556

  20. Co-cultivation of Streptomyces californicus and Stachybotrys chartarum stimulates the production of cytostatic compound(s) with immunotoxic properties

    SciTech Connect

    Penttinen, Piia . E-mail: Piia.Penttinen@ktl.fi; Pelkonen, Jukka; Huttunen, Kati; Hirvonen, Maija-Riitta

    2006-12-15

    We have recently shown that the actinobacterium Streptomyces californicus and the fungus Stachybotrys chartarum originating from moisture damaged buildings possess both immunotoxic and immunostimulatory characteristics, which are synergistically potentiated by microbial interaction. In the search for the causative agent(s) behind the immunotoxicity, the cytostatic effects of the co-cultivated spores of S. californicus and S. chartarum were compared to those caused by widely used cytostatic agents produced by streptomycetes. The RAW264.7 macrophages were exposed to four doses of doxorubicin (DOX), actinomycin D (AMD), mitomycin C (MMC) or phleomycin (PHLEO) for 24 h. Kinetics of the spores of the co-cultivated and the separately cultivated microbes (1 x 10{sup 6} spores/ml) was compared to DOX (0.15 {mu}M). Apoptotic responses were analyzed by measuring DNA content and mitochondria membrane depolarization with flow cytometer, and by the fluorometric caspase-3 assay. The present data indicate that interactions during co-cultivation of S. californicus and S. chartarum stimulate the production of an unidentified cytostatic compound(s) capable of inducing mitochondria mediated apoptosis and cell cycle arrest at S-G{sub 2}/M. The spores of co-cultivated microbes caused a 4-fold collapse of mitochondrial membrane potential and an almost 6-fold caspase-3 activation and DNA fragmentation when compared to control. Similar responses were induced by DNA cleaving compounds, especially DOX and AMD, at the relatively low concentrations, but not the spores of the same microbes when they were grown separately. These data suggest that when growing in the same habitat, interactions between S. californicus and S. chartarum stimulates the production of an unknown cytostatic compound(s) which evoke immunotoxic effects similar to those by chemotherapeutic drugs.

  1. Co-cultivation of Streptomyces californicus and Stachybotrys chartarum stimulates the production of cytostatic compound(s) with immunotoxic properties.

    PubMed

    Penttinen, Piia; Pelkonen, Jukka; Huttunen, Kati; Hirvonen, Maija-Riitta

    2006-12-15

    We have recently shown that the actinobacterium Streptomyces californicus and the fungus Stachybotrys chartarum originating from moisture damaged buildings possess both immunotoxic and immunostimulatory characteristics, which are synergistically potentiated by microbial interaction. In the search for the causative agent(s) behind the immunotoxicity, the cytostatic effects of the co-cultivated spores of S. californicus and S. chartarum were compared to those caused by widely used cytostatic agents produced by streptomycetes. The RAW264.7 macrophages were exposed to four doses of doxorubicin (DOX), actinomycin D (AMD), mitomycin C (MMC) or phleomycin (PHLEO) for 24 h. Kinetics of the spores of the co-cultivated and the separately cultivated microbes (1x10(6) spores/ml) was compared to DOX (0.15 muM). Apoptotic responses were analyzed by measuring DNA content and mitochondria membrane depolarization with flow cytometer, and by the fluorometric caspase-3 assay. The present data indicate that interactions during co-cultivation of S. californicus and S. chartarum stimulate the production of an unidentified cytostatic compound(s) capable of inducing mitochondria mediated apoptosis and cell cycle arrest at S-G(2)/M. The spores of co-cultivated microbes caused a 4-fold collapse of mitochondrial membrane potential and an almost 6-fold caspase-3 activation and DNA fragmentation when compared to control. Similar responses were induced by DNA cleaving compounds, especially DOX and AMD, at the relatively low concentrations, but not the spores of the same microbes when they were grown separately. These data suggest that when growing in the same habitat, interactions between S. californicus and S. chartarum stimulates the production of an unknown cytostatic compound(s) which evoke immunotoxic effects similar to those by chemotherapeutic drugs.

  2. Building-related respiratory symptoms can be predicted with semi-quantitative indices of exposure to dampness and mold.

    PubMed

    Park, J-H; Schleiff, P L; Attfield, M D; Cox-Ganser, J M; Kreiss, K

    2004-12-01

    Using a semi-quantitative mold exposure index, the National Institute for Occupational Safety and Health (NIOSH) investigated 13 college buildings to examine whether building-related respiratory symptoms among employees are associated with environmental exposure to mold and dampness in buildings. We collected data on upper and lower respiratory symptoms and their building-relatedness, and time spent in specific rooms with a self-administered questionnaires. Trained NIOSH industrial hygienists classified rooms for water stains, visible mold, mold odor, and moisture using semi-quantitative scales and then estimated individual exposure indices weighted by the time spent in specific rooms. The semi-quantitative exposure indices significantly predicted building-related respiratory symptoms, including wheeze [odds ratio (OR) = 2.3; 95% confidence interval (CI) = 1.1-4.5], chest tightness (OR = 2.2; 95% CI = 1.1-4.6), shortness of breath (OR = 2.7; 95% CI = 1.2-6.1), nasal (OR = 2.5; 95% CI = 1.3-4.7) and sinus (OR = 2.2; 95% CI = 1.2-4.1) symptoms, with exposure-response relationships. We found that conditions suggestive of indoor mold exposure at work were associated with building-related respiratory symptoms. Our findings suggest that observational semi-quantitative indices of exposure to dampness and mold can support action to prevent building-related respiratory diseases. Current air sampling methods have major limitations in assessing exposure to mold and other biological agents that may prevent the demonstration of associations of bioaerosol exposure with health. Our study demonstrates that semi-quantitative dampness/mold exposure indices, based solely on visual and olfactory observation and weighted by time spent in specific rooms, can predict existence of excessive building-related respiratory symptoms and diseases. Relative extent of water stains, visible mold, mold odor, or moisture can be used to prioritize remediation to reduce potential risk of building

  3. Protein profiles of nasal lavage fluid from individuals with work-related upper airway symptoms associated with moldy and damp buildings.

    PubMed

    Wåhlén, K; Fornander, L; Olausson, P; Ydreborg, K; Flodin, U; Graff, P; Lindahl, M; Ghafouri, B

    2016-10-01

    Upper airway irritation is common among individuals working in moldy and damp buildings. The aim of this study was to investigate effects on the protein composition of the nasal lining fluid. The prevalence of symptoms in relation to work environment was examined in 37 individuals working in two damp buildings. Microbial growth was confirmed in one of the buildings. Nasal lavage fluid was collected from 29 of the exposed subjects and 13 controls, not working in a damp building. Protein profiles were investigated with a proteomic approach and evaluated by multivariate statistical models. Subjects from both workplaces reported upper airway and ocular symptoms. Based on protein profiles, symptomatic subjects in the two workplaces were discriminated from each other and separated from healthy controls. The groups differed in proteins involved in inflammation and host defense. Measurements of innate immunity proteins showed a significant increase in protein S100-A8 and decrease in SPLUNC1 in subjects from one workplace, while alpha-1-antitrypsin was elevated in subjects from the other workplace, compared with healthy controls. The results show that protein profiles in nasal lavage fluid can be used to monitor airway mucosal effects in personnel working in damp buildings and indicate that the profile may be separated when the dampness is associated with the presence of molds. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  4. Isolation and Damping of Shocks, Vibrations and Seismic Movements at Buildings: Equipment and Pipe Networks by SERB-SITON Method

    SciTech Connect

    Panait, A.; Serban, V.

    2006-07-01

    The paper presents SERB -- SITON method to control, limit and damp the shocks, vibration, impact load and seismic movements with applications in buildings, equipment and pipe networks (herein called: 'components'). The elimination or reduction of shocks, vibration, impact load and seismic movements is a difficult problem, still improperly handled theoretically and practically because many times the phenomena are random in character and the behavior of components is non-linear with variations of the properties in time, variations that lead to the increase or decrease of the energy and impulse transfer from the dynamic excitation to the components. Moreover, the existing supports and dampers applied today, are not efficient enough in the reduction of the dynamic movement for all the frequency ranges met with in the technical application field. The stiffness and damping of classic supports do not allow a good isolation of components against shocks and vibrations so to eliminate their propagation to the environment and neither do they provide a satisfactory protection of the components sensitive to shocks and vibrations and seismic movements coming from the environment. In order to reduce the effects of shocks, vibrations impact and seismic movements on the components, this paper presents the results obtained by SITON on the concept, design, construction, experimental testing and application of new types of supports, devices and thin lattice structure, called 'SERB', capable to overtake large static loads, to allow displacements from impact, thermal expansions or yielding of supports and which, in any work position, can elastically overtake large dynamic loads or impact loads which they damp. The new supports and devices and thin lattice structure allow their adjustment without the occurrence of over-stressing in the components due to their non -- linear geometric behavior, and the contact pressure among the elements is limited to pre-set values to avoid blocking

  5. Damped Ly alpha absorbers at high redshift: Large disks or galactic building blocks?

    NASA Technical Reports Server (NTRS)

    Haehnelt, Martin G.; Steinmetz, Matthias; Rauch, Michael

    1997-01-01

    The nature of the physical structures giving rise to damped Lyman alpha absorption systems (DLAS) at high redshifts is investigated. The proposal that rapidly rotating large disks are the only viable explanation for the observed asymmetric profiles of low ionization absorption lines is examined. Using hydrodynamic simulations of galaxy formation, it is demonstated that irregular protogalactic clumps can reproduce the observed velocity width distribution and asymmetries of the absorption profiles equally well. The velocity broadening in the simulated clumps is due to a mixture of rotation, random motions, infall and merging. The observed velocity width correlates with the virial velocity for the dark matter halo of the forming protogalactic clump. The typical virial velocity of the halos required to lead to the DLAS population is approximately 100 km/s. It is concluded that the evidence that DLAS at high redshift are related to large, rapidly rotating disks, is not compelling.

  6. Inflammation-associated gene expression in RAW 264.7 macrophages induced by toxins from fungi common on damp building materials.

    PubMed

    Rand, Thomas G; Chang, Carolyn T; McMullin, David R; Miller, J David

    2017-09-01

    Most fungi that grow on damp building materials produce low molecular weight compounds, some of which are known to be toxic. In this study, we tested the hypothesis that exposure to some metabolites of fungi common on damp building materials would result in time-, dose-, and compound-specific responses in the production of various chemokines by RAW 264.7 cells. Cell cultures were exposed to a 10(-7)M or 10(-8)M metabolite dose for 2, 4, 8 or 24h. Metabolite concentrations used were based on those that might be expected in alveolar macrophages due to inhalation exposure from living or working in a damp building. Compared to controls, exposure provoked significant time-, dose- and compound-specific responses manifest as differentially elevated secretion of three of nine cytokines tested in culture supernatant of treated cells. The greatest number of cytokines produced in response to the metabolites tested were in andrastin A-treated cells (GM-CSF, TGFβ1, Tnf-α) followed by koninginin A (TGFβ1 and Tnf-α) and phomenone (GM-CSF, TGFβ1). Chaetoglobosin A, chaetomugilin D and walleminone exposures each resulted in significant time-specific production of Tnf-α only. This investigation adds to a body of evidence supporting the role of low molecular weight compounds from damp building materials as pathogen associated molecular patterns (PAMPs). Along with fungal glucan and chitin, these compounds contribute to the non-allergy based respiratory outcomes for people living and working in damp buildings. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Stachybotrys chartarum, trichothecene mycotoxins, and damp building-related illness: new insights into a public health enigma.

    PubMed

    Pestka, James J; Yike, Iwona; Dearborn, Dorr G; Ward, Marsha D W; Harkema, Jack R

    2008-07-01

    Damp building-related illnesses (DBRI) include a myriad of respiratory, immunologic, and neurologic symptoms that are sometimes etiologically linked to aberrant indoor growth of the toxic black mold, Stachybotrys chartarum. Although supportive evidence for such linkages is limited, there are exciting new findings about this enigmatic organism relative to its environmental dissemination, novel bioactive components, unique cellular targets, and molecular mechanisms of action which provide insight into the S. chartarum's potential to evoke allergic sensitization, inflammation, and cytotoxicity in the upper and lower respiratory tracts. Macrocyclic trichothecene mycotoxins, produced by one chemotype of this fungus, are potent translational inhibitors and stress kinase activators that appear to be a critical underlying cause for a number of adverse effects. Notably, these toxins form covalent protein adducts in vitro and in vivo and, furthermore, cause neurotoxicity and inflammation in the nose and brain of the mouse. A second S. chartarum chemotype has recently been shown to produce atranones-mycotoxins that can induce pulmonary inflammation. Other biologically active products of this fungus that might contribute to pathophysiologic effects include proteinases, hemolysins, beta-glucan, and spirocyclic drimanes. Solving the enigma of whether Stachybotrys inhalation indeed contributes to DBRI will require studies of the pathophysiologic effects of low dose chronic exposure to well-characterized, standardized preparations of S. chartarum spores and mycelial fragments, and, coexposures with other environmental cofactors. Such studies must be linked to improved assessments of human exposure to this fungus and its bioactive constituents in indoor air using both state-of-the-art sampling/analytical methods and relevant biomarkers.

  8. Quadratic Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Quadratic friction involves a discontinuous damping term in equations of motion in order that the frictional force always opposes the direction of the motion. Perhaps for this reason this topic is usually omitted from beginning texts in differential equations and physics. However, quadratic damping is more realistic than viscous damping in many…

  9. Quadratic Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Quadratic friction involves a discontinuous damping term in equations of motion in order that the frictional force always opposes the direction of the motion. Perhaps for this reason this topic is usually omitted from beginning texts in differential equations and physics. However, quadratic damping is more realistic than viscous damping in many…

  10. A BENCHMARK PROGRAM FOR EVALUATION OF METHODS FOR COMPUTING SEISMIC RESPONSE OF COUPLED BUILDING-PIPING/EQUIPMENT WITH NON-CLASSICAL DAMPING.

    SciTech Connect

    Xu, J.; Degrassi, G.; Chokshi, N.

    2001-03-22

    Under the auspices of the US Nuclear Regulatory Commission (NRC), Brookhaven National Laboratory (BNL) developed a comprehensive program to evaluate state-of-the-art methods and computer programs for seismic analysis of typical coupled nuclear power plant (NPP) systems with nonclassical damping. In this program, four benchmark models of coupled building-piping/equipment systems with different damping characteristics were analyzed for a suite of earthquakes by program participants applying their uniquely developed methods and computer programs. This paper presents the results of their analyses, and their comparison to the benchmark solutions generated by BNL using time domain direct integration methods. The participant's analysis results established using complex modal time history methods showed good comparison with the BNL solutions, while the analyses produced with either complex-mode response spectrum methods or classical normal-mode response spectrum method, in general, produced more conservative results, when averaged over a suite of earthquakes. However, when coupling due to damping is significant, complex-mode response spectrum methods performed better than the classical normal-mode response spectrum method. Furthermore, as part of the program objectives, a parametric assessment is also presented in this paper, aimed at evaluation of the applicability of various analysis methods to problems with different dynamic characteristics unique to coupled NPP systems. It is believed that the findings and insights learned from this program will be useful in developing new acceptance criteria and providing guidance for future regulatory activities involving licensing applications of these alternate methods to coupled systems.

  11. Functional characterization of a Penicillium chrysogenum mutanase gene induced upon co-cultivation with Bacillus subtilis

    PubMed Central

    2014-01-01

    Background Microbial gene expression is strongly influenced by environmental growth conditions. Comparison of gene expression under different conditions is frequently used for functional analysis and to unravel regulatory networks, however, gene expression responses to co-cultivation with other microorganisms, a common occurrence in nature, is rarely studied under laboratory conditions. To explore cellular responses of the antibiotic-producing fungus Penicillium chrysogenum to prokaryotes, the present study investigates its transcriptional responses during co-cultivation with Bacillus subtilis. Results Steady-state glucose-limited chemostats of P. chrysogenum grown under penillicin-non-producing conditions were inoculated with B. subtilis. Physiological and transcriptional responses of P. chrysogenum in the resulting mixed culture were monitored over 72 h. Under these conditions, B. subtilis outcompeted P. chrysogenum, as reflected by a three-fold increase of the B. subtilis population size and a two-fold reduction of the P. chrysogenum biomass concentration. Genes involved in the penicillin pathway and in synthesis of the penicillin precursors and side-chain were unresponsive to the presence of B. subtilis. Moreover, Penicillium polyketide synthase and nonribosomal peptide synthase genes were either not expressed or down-regulated. Among the highly responsive genes, two putative α-1,3 endoglucanase (mutanase) genes viz Pc12g07500 and Pc12g13330 were upregulated by more than 15-fold and 8-fold, respectively. Measurement of enzyme activity in the supernatant of mixed culture confirmed that the co-cultivation with B. subtilis induced mutanase production. Mutanase activity was neither observed in pure cultures of P. chrysogenum or B. subtilis, nor during exposure of P. chrysogenum to B. subtilis culture supernatants or heat-inactivated B. subtilis cells. However, mutanase production was observed in cultures of P. chrysogenum exposed to filter-sterilized supernatants

  12. Landau damping

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2010-10-01

    Section 2.5.8 of the Handbook of Accelerator Physics and Engineering on Landau damping is rewritten. An solvable example is first given to demonstrate the interplay between Landau damping and decoherence. This example is an actual one when the beam oscillatory motion is driven by a wake force. The dispersion relation is derived and its implication on Landau damping is illustrated. The rest of the article touches on the Landau damping of transverse and longitudinal beam oscillations. The stability criteria are given for a bunched beam and the changes of the criteria when the beam is lengthened and becomes unbunched.

  13. Characterization of Co-Cultivation of Cyanobacteria on Growth, Productions of Polysaccharides and Extracellular Proteins, Nitrogenase Activity, and Photosynthetic Activity.

    PubMed

    Xue, Chuizhao; Wang, Libo; Wu, Tong; Zhang, Shiping; Tang, Tao; Wang, Liang; Zhao, Quanyu; Sun, Yuhan

    2017-01-01

    Cyanobacteria as biofertilizers are benefit to reduce the use of chemical fertilizers and reestablish the ecological system in soil. In general, several strains of cyanobacteria were involved in the biofertilizers. The co-cultivation of cyanobacteria were characterized on growth profile, production of polysaccharides and extracellular proteins, nitrogenase activity, and photosynthetic activity for three selected N2-fixing cyanobacteria, Anabaena cylindrica (B1611 and F243) and Nostoc sp. (F280). After eight-day culture, the highest dry weights were obtained in F280 pure culture and co-cultivation of B1611 and F280. Higher production of extracellular proteins and cell-bonding polysaccharides (CPS) were observed in co-cultivations compared with pure culture. The highest released polysaccharides (RPS) contents were obtained in pure culture of F280 and co-cultivation of F280 and F243. Galactose and glucose were major components of CPS and RPS in all samples. Trehalose was a specific component of RPS in F280 pure culture. Based on the monosaccharide contents of CPS and RPS, F280 was the dominant species in the related treatments of co-cultivation. The nitrogenase activities in all treatments exhibited a sharp rise at the late stage while a significant decrease existed when three cyanobacteria strains were mixed. Photosynthetic activities for all treatments were determined with rapid light curve, and the related parameters were estimated.

  14. Coulomb Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  15. Coulomb Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  16. Co-cultivation of microalgae and nitrifiers for higher biomass production and better carbon capture.

    PubMed

    Bilanovic, Dragoljub; Holland, Mark; Starosvetsky, Jeanna; Armon, Robert

    2016-11-01

    The aim of this work was to study co-cultivation of nitrifiers with microalgae as a non-intrusive technique for selective removal of oxygen generated by microalgae. Biomass concentration was, at least, 23% higher in mixed-cultures where nitrifiers kept the dissolved oxygen concentration below 9.0μLL(-1) than in control Chlorella vulgaris axenic-cultures where the concentration of dissolved oxygen was higher than 10.0μLL(-1). This approach to eliminating oxygen inhibition of microalgal growth could become the basis for the development of advanced microalgae reactors for removal of CO2 from the atmosphere, and concentrated CO2 streams. CO2 sequestration would become a chemically and geologically safer and environmentally more sound technology provided it uses microalgal, or other biomass, instead of CO2, for carbon storage.

  17. Significance of stiffening of high damping rubber bearings on the response of base-isolated buildings under near-fault earthquakes

    NASA Astrophysics Data System (ADS)

    Alhan, Cenk; Gazi, Hatice; Kurtuluş, Hakan

    2016-10-01

    High Damping Rubber Bearings (HDRBs) are among various types of laterally flexible isolation system elements that effectively protect structures from detrimental effects of earthquakes by lengthening their fundamental periods. However, large isolator displacements resulting in strains larger than 100% may come into scene in case of near-fault ground motions containing long-period and large-amplitude velocity and/or displacement pulses. This is particularly important when HDRBs are used since the post-yield stiffness of an HDRB increases due to inherent strain hardening characteristics when a threshold isolator displacement limit is exceeded. Therefore, it may be critical to consider the stiffening of HDRBs in modeling of these elements for accurate seismic response evaluation of the buildings equipped with HDRBs that are located in near-fault regions. In this study, the significance of stiffening of HDRBs on the response of base-isolated buildings is investigated by conducting nonlinear time history analyses of benchmark six-story base-isolated buildings which employ HDRBs that are represented by non-stiffening or stiffening models under both historical and synthetic near-fault ground motions of various magnitudes and fault distances. The structural response parameters included in the comparisons are base displacements, story drifts, and floor accelerations. It is found that, the significance of stiffening of HDRBs on the response of base-isolated buildings under near-fault earthquakes becomes more prominent as the earthquake magnitude increases and the fault distance decreases and thus suggestions for modifications to seismic code regulations are made accordingly.

  18. Can the co-cultivation of rice and fish help sustain rice production?

    PubMed Central

    Hu, Liangliang; Zhang, Jian; Ren, Weizheng; Guo, Liang; Cheng, Yongxu; Li, Jiayao; Li, Kexin; Zhu, Zewen; Zhang, Jiaen; Luo, Shiming; Cheng, Lei; Tang, Jianjun; Chen, Xin

    2016-01-01

    Because rice feeds half of the world’s population, a secure global food supply depends on sustainable rice production. Here we test whether the co-cultivation of rice and fish into one “rice-fish system” (RFS; fish refers to aquatic animals in this article) could help sustain rice production. We examined intensive and traditional RFSs that have been widely practiced in China. We found that rice yields did not decrease when fish yield was below a threshold value in each intensive RFS. Below the thresholds, moreover, fish yields in intensive RFSs can be substantially higher than those in traditional RFS without reducing rice yield. Relative to rice monoculture, the use of fertilizer-nitrogen and pesticides decreased, and the farmers’ net income increased in RFSs. The results suggest that RFSs can help sustain rice production, and suggest that development of co-culture technologies (i.e. proper field configuration for fish and rice) is necessary to achieve the sustainability. PMID:27349875

  19. Recovery of an environmental Chlamydia strain from activated sludge by co-cultivation with Acanthamoeba sp.

    PubMed

    Collingro, Astrid; Poppert, Sven; Heinz, Eva; Schmitz-Esser, Stephan; Essig, Andreas; Schweikert, Michael; Wagner, Michael; Horn, Matthias

    2005-01-01

    Chlamydiae are a unique group of obligate intracellular bacteria comprising important pathogens of vertebrates as well as symbionts of free-living amoebae. Although there is ample molecular evidence for a huge diversity and wide distribution of chlamydiae in nature, environmental chlamydiae are currently represented by only few isolates. This paper reports the recovery of a novel environmental chlamydia strain from activated sludge by co-cultivation with Acanthamoeba sp. The recovered environmental chlamydia strain UV-7 showed the characteristic morphology of chlamydial developmental stages as revealed by electron microscopy and was identified as a new member of the family Parachlamydiaceae (98.7 % 16S rRNA sequence similarity to Parachlamydia acanthamoebae). Infection studies suggested that Parachlamydia sp. UV-7 is not confined to amoeba hosts but is also able to invade mammalian cells. These findings outline a new straightforward approach to retrieving environmental chlamydiae from nature without prior, tedious isolation and cultivation of their natural host cells, and lend further support to suggested implications of environmental chlamydiae for public health.

  20. Can the co-cultivation of rice and fish help sustain rice production?

    NASA Astrophysics Data System (ADS)

    Hu, Liangliang; Zhang, Jian; Ren, Weizheng; Guo, Liang; Cheng, Yongxu; Li, Jiayao; Li, Kexin; Zhu, Zewen; Zhang, Jiaen; Luo, Shiming; Cheng, Lei; Tang, Jianjun; Chen, Xin

    2016-06-01

    Because rice feeds half of the world’s population, a secure global food supply depends on sustainable rice production. Here we test whether the co-cultivation of rice and fish into one “rice-fish system” (RFS; fish refers to aquatic animals in this article) could help sustain rice production. We examined intensive and traditional RFSs that have been widely practiced in China. We found that rice yields did not decrease when fish yield was below a threshold value in each intensive RFS. Below the thresholds, moreover, fish yields in intensive RFSs can be substantially higher than those in traditional RFS without reducing rice yield. Relative to rice monoculture, the use of fertilizer-nitrogen and pesticides decreased, and the farmers’ net income increased in RFSs. The results suggest that RFSs can help sustain rice production, and suggest that development of co-culture technologies (i.e. proper field configuration for fish and rice) is necessary to achieve the sustainability.

  1. Involvement of formyl peptide receptors in the stimulatory effect of crotoxin on macrophages co-cultivated with tumour cells.

    PubMed

    Costa, E S; Faiad, O J; Landgraf, R G; Ferreira, A K; Brigatte, P; Curi, R; Cury, Y; Sampaio, S C

    2013-11-01

    Crotoxin (CTX) is the main neurotoxic component of Crotalus durissus terrificus snake venom. It inhibits tumour growth and modulates the function of macrophages, which are essential cells in the tumour microenvironment. The present study investigated the effect of CTX on the secretory activity of monocultured macrophages and macrophages co-cultivated with LLC-WRC 256 cells. The effect of the macrophage secretory activities on tumour cell proliferation was also evaluated. Macrophages pre-treated with CTX (0.3 μg/mL) for 2 h were co-cultivated with LLC-WRC 256 cells, and the secretory activity of the macrophages was determined after 12, 24 and 48 h. The co-cultivation of CTX-treated macrophages with the tumour cells caused a 20% reduction in tumour cell proliferation. The production of both H2O2 and NO was increased by 41% and 29% after 24 or 48 h of co-cultivation, respectively, compared to the values for the co-cultures of macrophages of control. The level of secreted IL-1β increased by 3.7- and 3.2-fold after 12 h and 24 h of co-cultivation, respectively. Moreover, an increased level of LXA4 (25%) was observed after 24 h of co-cultivation, and a 2.3- and 2.1-fold increased level of 15-epi-LXA4 was observed after 24 h and 48 h, respectively. Boc-2, a selective antagonist of formyl peptide receptors, blocked both the stimulatory effect of CTX on the macrophage secretory activity and the inhibitory effect of these cells on tumour cell proliferation. Taken together, these results indicate that CTX enhanced the secretory activity of macrophages, which may contribute to the antitumour activity of these cells, and that activation of formyl peptide receptors appears to play a major role in this effect. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Non-destructive mapping of dampness and salts in degraded wall paintings in hypogeous buildings: the case of St. Clement at mass fresco in St. Clement Basilica, Rome.

    PubMed

    Di Tullio, Valeria; Proietti, Noemi; Gobbino, Marco; Capitani, Donatella; Olmi, Roberto; Priori, Saverio; Riminesi, Cristiano; Giani, Elisabetta

    2010-03-01

    As is well known, the deterioration of wall paintings due to the capillary rise of water through the walls is a very widespread problem. In this paper, a study of microclimate monitoring, unilateral nuclear magnetic resonance (NMR), and evanescent-field dielectrometry (EFD) was applied to map non-destructively, in situ, and in a quantitative way the distribution of the moisture in an ancient deteriorated wall painting of the eleventh century. Both unilateral NMR and EFD are quite new, fully portable, and non-destructive techniques, and their combination is absolutely new. The approach reported here is proposed as a new analytical protocol to afford the problem of mapping, non-destructively, the moisture in a deteriorated wall painting in a hypogeous building such as that of the second level of St. Clement Basilica, Rome (Italy), where the use of IR thermography is impaired due to the environmental conditions, and the gravimetric tests are forbidden due to the preciousness of the artifact. The moisture distribution was mapped at different depths, from the very first layers of the painted film to a depth of 2 cm. It has also been shown how the map obtained in the first layers of the artwork is affected by the environmental conditions typical of a hypogeous building, whereas the maps obtained at higher depths are representative of the moisture due to the capillary rise of water from the ground. The quantitative analysis of the moisture was performed by calibrating NMR and EFD signals with purposely prepared specimens. This study may be applied before and after performing any intervention aimed at restoring and improving the state of conservation of this type of artwork and reducing the dampness or extracting salts (driven by the variation of moisture content) and monitoring the effectiveness of the performed interventions during the time. This protocol is applicable to any type of porous material.

  3. Co-cultivation of Aspergillus nidulans Recombinant Strains Produces an Enzymatic Cocktail as Alternative to Alkaline Sugarcane Bagasse Pretreatment

    PubMed Central

    Lima, Matheus S.; Damasio, André R. de L.; Crnkovic, Paula M.; Pinto, Marcelo R.; da Silva, Ana M.; da Silva, Jean C. R.; Segato, Fernando; de Lucas, Rosymar C.; Jorge, João A.; Polizeli, Maria de L. T. de M.

    2016-01-01

    Plant materials represent a strategic energy source because they can give rise to sustainable biofuels through the fermentation of their carbohydrates. A clear example of a plant-derived biofuel resource is the sugar cane bagasse exhibiting 60–80% of fermentable sugars in its composition. However, the current methods of plant bioconversion employ severe and harmful chemical/physical pretreatments raising biofuel cost production and environmental degradation. Replacing these methods with co-cultivated enzymatic cocktails is an alternative. Here we propose a pretreatment for sugarcane bagasse using a multi-enzymatic cocktail from the co-cultivation of four Aspergillus nidulans recombinant strains. The co-cultivation resulted in the simultaneous production of GH51 arabinofuranosidase (AbfA), GH11 endo-1,4-xylanase (XlnA), GH43 endo-1,5-arabinanase (AbnA) and GH12 xyloglucan specific endo-β-1,4-glucanase (XegA). This core set of recombinant enzymes was more efficient than the alternative alkaline method in maintaining the cellulose integrity and exposing this cellulose to the following saccharification process. Thermogravimetric and differential thermal analysis revealed residual byproducts on the alkali pretreated biomass, which were not found in the enzymatic pretreatment. Therefore, the enzymatic pretreatment was residue-free and seemed to be more efficient than the applied alkaline method, which makes it suitable for bioethanol production. PMID:27199917

  4. Co-cultivation of Aspergillus nidulans Recombinant Strains Produces an Enzymatic Cocktail as Alternative to Alkaline Sugarcane Bagasse Pretreatment.

    PubMed

    Lima, Matheus S; Damasio, André R de L; Crnkovic, Paula M; Pinto, Marcelo R; da Silva, Ana M; da Silva, Jean C R; Segato, Fernando; de Lucas, Rosymar C; Jorge, João A; Polizeli, Maria de L T de M

    2016-01-01

    Plant materials represent a strategic energy source because they can give rise to sustainable biofuels through the fermentation of their carbohydrates. A clear example of a plant-derived biofuel resource is the sugar cane bagasse exhibiting 60-80% of fermentable sugars in its composition. However, the current methods of plant bioconversion employ severe and harmful chemical/physical pretreatments raising biofuel cost production and environmental degradation. Replacing these methods with co-cultivated enzymatic cocktails is an alternative. Here we propose a pretreatment for sugarcane bagasse using a multi-enzymatic cocktail from the co-cultivation of four Aspergillus nidulans recombinant strains. The co-cultivation resulted in the simultaneous production of GH51 arabinofuranosidase (AbfA), GH11 endo-1,4-xylanase (XlnA), GH43 endo-1,5-arabinanase (AbnA) and GH12 xyloglucan specific endo-β-1,4-glucanase (XegA). This core set of recombinant enzymes was more efficient than the alternative alkaline method in maintaining the cellulose integrity and exposing this cellulose to the following saccharification process. Thermogravimetric and differential thermal analysis revealed residual byproducts on the alkali pretreated biomass, which were not found in the enzymatic pretreatment. Therefore, the enzymatic pretreatment was residue-free and seemed to be more efficient than the applied alkaline method, which makes it suitable for bioethanol production.

  5. A dual-species co-cultivation system to study the interactions between Roseobacters and dinoflagellates

    PubMed Central

    Wang, Hui; Tomasch, Jürgen; Jarek, Michael; Wagner-Döbler, Irene

    2014-01-01

    Some microalgae in nature live in symbiosis with microorganisms that can enhance or inhibit growth, thus influencing the dynamics of phytoplankton blooms. In spite of the great ecological importance of these interactions, very few defined laboratory systems are available to study them in detail. Here we present a co-cultivation system consisting of the toxic phototrophic dinoflagellate Prorocentrum minimum and the photoheterotrophic alphaproteobacterium Dinoroseobacter shibae. In a mineral medium lacking a carbon source, vitamins for the bacterium and the essential vitamin B12 for the dinoflagellate, growth dynamics reproducibly went from a mutualistic phase, where both algae and bacteria grow, to a pathogenic phase, where the algae are killed by the bacteria. The data show a “Jekyll and Hyde” lifestyle that had been proposed but not previously demonstrated. We used RNAseq and microarray analysis to determine which genes of D. shibae are transcribed and differentially expressed in a light dependent way at an early time-point of the co-culture when the bacterium grows very slowly. Enrichment of bacterial mRNA for transcriptome analysis was optimized, but none of the available methods proved capable of removing dinoflagellate ribosomal RNA completely. RNAseq showed that a phasin encoding gene (phaP1) which is part of the polyhydroxyalkanoate (PHA) metabolism operon represented approximately 10% of all transcripts. Five genes for aerobic anoxygenic photosynthesis were down-regulated in the light, indicating that the photosynthesis apparatus was functional. A betaine-choline-carnitine-transporter (BCCT) that may be used for dimethylsulfoniopropionate (DMSP) uptake was the highest up-regulated gene in the light. The data suggest that at this early mutualistic phase of the symbiosis, PHA degradation might be the main carbon and energy source of D. shibae, supplemented in the light by degradation of DMSP and aerobic anoxygenic photosynthesis. PMID:25009539

  6. Observed Faraday Effects in Damped Lyα Absorbers and Lyman Limit Systems: The Magnetized Environment of Galactic Building Blocks at Redshift = 2

    NASA Astrophysics Data System (ADS)

    Farnes, J. S.; Rudnick, L.; Gaensler, B. M.; Haverkorn, M.; O'Sullivan, S. P.; Curran, S. J.

    2017-06-01

    Protogalactic environments are typically identified using quasar absorption lines and can manifest as Damped Lyman-alpha Absorbers (DLAs) and Lyman Limit Systems (LLSs). We use radio observations of Faraday effects to test whether these galactic building blocks host a magnetized medium, by combining DLA and LLS detections with 1.4 GHz polarization data from the NRAO VLA Sky Survey (NVSS). We obtain a control, a DLA, and an LLS sample consisting of 114, 19, and 27 lines of sight, respectively. Using a Bayesian framework and weakly informative priors, we are unable to detect either coherent or random magnetic fields in DLAs: the regular coherent fields must be ≤slant 2.8 μG, and the lack of depolarization suggests the weakly magnetized gas in DLAs is non-turbulent and quiescent. However, we find a mild suggestive indication that LLSs have coherent magnetic fields, with a 71.5% probability that LLSs have higher | {RM}| than a control, although this is sensitive to the redshift distribution. We also find a strong indication that LLSs host random magnetic fields, with a 95.5% probability that LLS lines of sight have lower polarized fractions than a control. The regular coherent fields within the LLSs must be ≤slant 2.4 μG, and the magnetized gas must be highly turbulent with a typical turbulent length scale on the order of ≈5-20 pc. Our results are consistent with the standard dynamo paradigm, whereby magnetism in protogalaxies increases in coherence over cosmic time, and with a hierarchical galaxy formation scenario, with the DLAs and LLSs exploring different stages of magnetic field evolution in galaxies.

  7. Sesquiterpene emissions from Alternaria alternata and Fusarium oxysporum: Effects of age, nutrient availability, and co-cultivation

    PubMed Central

    Weikl, Fabian; Ghirardo, Andrea; Schnitzler, Jörg-Peter; Pritsch, Karin

    2016-01-01

    Alternaria alternata is one of the most studied fungi to date because of its impact on human life – from plant pathogenicity to allergenicity. However, its sesquiterpene emissions have not been systematically explored. Alternaria regularly co-occurs with Fusarium fungi, which are common plant pathogens, on withering plants. We analyzed the diversity and determined the absolute quantities of volatile organic compounds (VOCs) in the headspace above mycelial cultures of A. alternata and Fusarium oxysporum under different conditions (nutrient rich and poor, single cultures and co-cultivation) and at different mycelial ages. Using stir bar sorptive extraction and gas chromatography–mass spectrometry, we observed A. alternata to strongly emit sesquiterpenes, particularly during the early growth stages, while emissions from F. oxysporum consistently remained comparatively low. The emission profile characterizing A. alternata comprised over 20 sesquiterpenes with few effects from nutrient quality and age on the overall emission profile. Co-cultivation with F. oxysporum resulted in reduced amounts of VOCs emitted from A. alternata although its profile remained similar. Both fungi showed distinct emission profiles, rendering them suitable biomarkers for growth-detection of their phylotype in ambient air. The study highlights the importance of thorough and quantitative evaluations of fungal emissions of volatile infochemicals such as sesquiterpenes. PMID:26915756

  8. Sesquiterpene emissions from Alternaria alternata and Fusarium oxysporum: Effects of age, nutrient availability, and co-cultivation.

    PubMed

    Weikl, Fabian; Ghirardo, Andrea; Schnitzler, Jörg-Peter; Pritsch, Karin

    2016-02-26

    Alternaria alternata is one of the most studied fungi to date because of its impact on human life - from plant pathogenicity to allergenicity. However, its sesquiterpene emissions have not been systematically explored. Alternaria regularly co-occurs with Fusarium fungi, which are common plant pathogens, on withering plants. We analyzed the diversity and determined the absolute quantities of volatile organic compounds (VOCs) in the headspace above mycelial cultures of A. alternata and Fusarium oxysporum under different conditions (nutrient rich and poor, single cultures and co-cultivation) and at different mycelial ages. Using stir bar sorptive extraction and gas chromatography-mass spectrometry, we observed A. alternata to strongly emit sesquiterpenes, particularly during the early growth stages, while emissions from F. oxysporum consistently remained comparatively low. The emission profile characterizing A. alternata comprised over 20 sesquiterpenes with few effects from nutrient quality and age on the overall emission profile. Co-cultivation with F. oxysporum resulted in reduced amounts of VOCs emitted from A. alternata although its profile remained similar. Both fungi showed distinct emission profiles, rendering them suitable biomarkers for growth-detection of their phylotype in ambient air. The study highlights the importance of thorough and quantitative evaluations of fungal emissions of volatile infochemicals such as sesquiterpenes.

  9. [Comparison of the indirect immunofluorescence assay performance of Bartonella henselae antigens obtained by co-cultivation in Vero and HeLa cells].

    PubMed

    Ergin, Cağrı; Akkaya, Yüksel; Kiriş Satılmış, Ozgün; Yılmaz, Cansev

    2011-07-01

    The laboratory diagnosis of Bartonella henselae infection is mainly based on serological testing by indirect immunofluorescence assay (IFA). Cell line co-cultivation with B.henselae and agar derivated antigens are the two major procedures used for evaluation of anti-Bartonella antibodies. Vero and Hep-2 cell lines are the most commonly used media for co-cultivation both in-house and commercial diagnostic kits production. However, HeLa cells which are easily supplied and grown, also can easily be infected by B.henselae. The aim of this study was to compare the performances of antigens obtained by co-cultivation of B.henselae ATCC 49882 (Houston-1) in Vero and HeLa Cells in IFA serology. Out of 381 sera samples, 127 (33.3%) were found positive and 195 (51.2%) were found negative by IFA performed by both cell line co-cultivations. The total agreement between the methods were found as 84.5% (322/381), and Cohen kappa value was calculated as 0.68 (strong, coherent). As a result, He-La cells were found to be useful for the preparation of B.henselae antigens to be used in IFA for the serologic diagnosis of B.henselae infections. However different genotype strains and cross reactions with other infectious agents should be investigated by further studies before routine applications of HeLa cell co-cultivations procedure is established.

  10. Effects of amoebae on the growth of microbes isolated from moisture-damaged buildings.

    PubMed

    Yli-Pirilä, Terhi; Kusnetsov, Jaana; Hirvonen, Maija-Riitta; Seuri, Markku; Nevalainen, Aino

    2006-04-01

    Dampness, moisture, and mold in buildings are associated with adverse health outcomes. In addition to fungi and bacteria, amoebae have been found in moisture-damaged building materials. Amoebae and a growing list of bacteria have been shown to have mutual effects on each other's growth, but the interactions between amoebae and microbes common in moisture-damaged buildings have not been reported. We co-cultivated the amoeba Acanthamoeba polyphaga with bacteria and fungi isolated from moisture-damaged buildings in laboratory conditions for up to 28 days. The microbes selected were the bacteria Streptomyces californicus, Bacillus cereus, and Pseudomonas fluorescens, and the fungi Stachybotrys chartarum, Aspergillus versicolor, and Penicillium spinulosum. Fungi and bacteria generally benefited from the presence of the amoebae, whereas the growth of amoebae was hindered by Streptomyces californicus, Stachybotrys chartarum, and Bacillus cereus. Pseudomonas fluorescens slightly enhanced amoebae viability. Amoebae were indifferent to the presence of Aspergillus versicolor and Penicillium spinulosum. Thus, our results show that amoebae can alter the survival and growth of some microbes in moisture-damaged buildings.

  11. Highly efficient Agrobacterium-mediated transformation of embryogenic cell suspensions of Musa acuminata cv. Mas (AA) via a liquid co-cultivation system.

    PubMed

    Huang, Xia; Huang, Xue-Lin; Xiao, Wang; Zhao, Jie-Tang; Dai, Xue-Mei; Chen, Yun-Feng; Li, Xiao-Ju

    2007-10-01

    A high efficient protocol of Agrobacterium-mediated transformation of Musa acuminata cv. Mas (AA), a major banana variety of the South East Asia region, was developed in this study. Male-flower-derived embryogenic cell suspensions (ECS) were co-cultivated in liquid medium with Agrobacterium strain EHA105 harboring a binary vector pCAMBIA2301 carrying nptII and gusA gene in the T-DNA. Depending upon conditions and duration of co-cultivation in liquid medium, 0-490 transgenic plants per 0.5 ml packed cell volume (PCV) of ECS were obtained. The optimum duration of inoculation was 2 h, and the highest transformation frequency was achieved when infected ECS were co-cultivated in liquid medium first for 12 h at 40 rpm and then for 156 h at 100 rpm on a rotary shaker. Co-cultivation for a shorter duration (72 h) or shaking constantly at 100 rpm at the same duration gave 1.6 and 1.8 folds lower transformation efficiency, respectively. No transgenic plants were obtained in parallel experiments carried on semi-solid media. Histochemical GUS assay and molecular analysis in several tissues of the transgenic plants demonstrated that foreign genes were stably integrated into the banana genome. Compared to semi-solid co-cultivation transformation in other banana species, it is remarkable that liquid co-cultivation was much more efficient for transformation of the Mas cultivar, and was at least 1 month faster for regenerating transgenic plants.

  12. Aflatoxin B1 degradation during co-cultivation of Aspergillus flavus and Pleurotus ostreatus strains on rice straw.

    PubMed

    Das, Arijit; Bhattacharya, Sourav; Palaniswamy, Muthusamy; Angayarkanni, Jayaraman

    2015-06-01

    Aflatoxin B1 (AFB1) produced by Aspergillus flavus is known to have carcinogenic and teratogenic effects on animal health. Accidental feeding of AFB1-contaminated rice straw may be detrimental to dairy cattle. White-rot basidiomycetous fungus Pleurotus ostreatus can grow on different agronomic wastes by synthesizing different ligninolytic enzymes. These extracellular enzymes are capable of degrading many environmentally hazardous compounds including AFB1. The present study examines the ability of different strains of P. ostreatus to degrade AFB1 in contaminated rice straw. Different strains of A. flavus were inoculated on rice straw for AFB1 production. The moldy straw was then subjected to co-cultivation by different strains of P. ostreatus. The extent of AFB1 degradation was determined by high performance liquid chromatography. Results indicated the presence of AFB1 in the moldy straw samples at levels of 27.95 ± 0.23 and 21.26 ± 0.55 µg/g of dry substrate for A. flavus MTCC 2798 and A. flavus GHBF09, respectively. Co-cultivation of P. ostreatus strains on AFB1-contaminated rice straw revealed their ability to rapidly colonize the substrate by profuse hyphal ramification. Highest degradation of AFB1 (89.41 %) was recorded in the straw containing co-cultures of A. flavus MTCC 2798 and P. ostreatus GHBBF10. Natural isolate P. ostreatus GHBBF10 demonstrated higher AFB1-degradation potential than P.ostreatus MTCC 142. This basidiomycete strain can be further exploited to effectively degrade moderate concentrations of AFB1 in contaminated moldy rice straw.

  13. Magnetic Damping For Maglev

    DOE PAGES

    Zhu, S.; Cai, Y.; Rote, D. M.; ...

    1998-01-01

    Magnetic damping is one of the important parameters that control the response and stability of maglev systems. An experimental study to measure magnetic damping directly is presented. A plate attached to a permanent magnet levitated on a rotating drum was tested to investigate the effect of various parameters, such as conductivity, gap, excitation frequency, and oscillation amplitude, on magnetic damping. The experimental technique is capable of measuring all of the magnetic damping coefficients, some of which cannot be measured indirectly.

  14. Damped leaf flexure hinge

    NASA Astrophysics Data System (ADS)

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  15. Damped leaf flexure hinge.

    PubMed

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  16. Further characterization of the genotoxicity of formaldehyde in vitro by the sister chromatid exchange test and co-cultivation experiments.

    PubMed

    Neuss, Simone; Speit, Günter

    2008-09-01

    The induction of sister chromatid exchanges (SCE) was used to further characterize the genotoxic action of formaldehyde (FA) on cultured mammalian cells. FA induced SCE in V79 Chinese hamster cells and A549 human lung cells in a concentration-related manner. Addition of 5-bromodeoxyuridine (BrdUrd) for the differentiation of sister chromatids to visualize SCE 4 h after the FA treatment led to a clearly reduced induction of SCE in agreement with the repair kinetics of FA-induced DNA-protein cross-links. When A549 cells were treated with FA for 1 h and then co-cultivated with V79 cells in the presence of BrdUrd, a clear induction of SCE was measured in V79 cells. When the same experiment was performed including washing and change of medium after the FA treatment, no induction of SCE was measured in V79 cells. These results indicate that reactive FA remains in the cell culture medium for a longer time period despite the high reactivity of FA with macromolecules. However, FA that has entered a cell is not released and does not damage other cells. Possible implications for the mutagenicity of FA in vivo will be discussed.

  17. DNA damage and p53 in RAW264.7 cells induced by the spores of co-cultivated Streptomyces californicus and Stachybotrys chartarum.

    PubMed

    Penttinen, Piia; Tampio, Marjo; Mäki-Paakkanen, Jorma; Vähäkangas, Kirsi; Pelkonen, Jukka; Hirvonen, Maija-Riitta

    2007-06-03

    Our recent studies have revealed that the co-cultivation of environmental microbes, Streptomyces californicus and Stachybotrys chartarum, potentiates the immunotoxic properties of the spores. In the present study, the spore-induced genotoxic potential of these microbes was investigated. Dose related differences in genotoxic and cytotoxic effects and in p53 level in mouse RAW264.7 macrophages were studied after 24h exposure to the spores of separately cultivated Streptomyces californicus or Stachybotrys chartarum alone, a simple spore-mixture of these microbes as well as to the spores of co-cultivated microbes. The genotoxic effect of the exposures was determined by the Comet assay and p53 level was analyzed by immunoblotting. Cytotoxicity was assessed by using flow cytometric analysis and also by the MTT test. The results revealed that the spores of co-cultivated microbes evoked DNA damage, p53 accumulation and cytotoxicity at a lower dose than the other exposures, and at the highest dose there was a 2.5-fold increase in DNA damage compared to control. In addition, the spores of Streptomyces californicus alone induced a 1.5-fold increase in DNA damage compared to control, dose dependent p53 accumulation and also extensive cytotoxicity. In contrast, the mixture of separately cultivated spores or the spores of Stachybotrys chartarum alone did not induce DNA damage with any tested dose although they triggered significant cytotoxicity and a slightly increased p53 level. Our results suggest that the detected genotoxic responses are the result of DNA damage in RAW264.7 cells by some genotoxically active metabolite(s) and the production of this compound was stimulated in Streptomyces californicus when it was co-cultivated with Stachybotrys chartarum.

  18. Critically damped quantum search.

    PubMed

    Mizel, Ari

    2009-04-17

    Although measurement and unitary processes can accomplish any quantum evolution in principle, thinking in terms of dissipation and damping can be powerful. We propose a modification of Grover's algorithm in which the idea of damping plays a natural role. Remarkably, we find that there is a critical damping value that divides between the quantum O(sqrt[N]) and classical O(N) search regimes. In addition, by allowing the damping to vary in a fashion we describe, one obtains a fixed-point quantum search algorithm in which ignorance of the number of targets increases the number of oracle queries only by a factor of 1.5.

  19. Engineered damping treatments

    NASA Astrophysics Data System (ADS)

    Oh, J.; Ray, Manas C.; Baz, Amr M.

    2001-07-01

    Engineered Damping Treatments (EDT) that have high damping characteristics per unit volume are presented. The EDT's under consideration, consist of cellular viscoelastic damping matrices with optimally selected cell configuration, size and distribution. The cellular topology of the EDT's is designed using Computer-Aided-Design (CAD) strategies and the obtained optimal configurations will be manufactured using the state-of-the-art technology of Rapid Prototyping (RP). The EDT's are modeled using the finite element method in an attempt to determine the optimal topologies that maximize the strain energy, maximize the damping characteristics and minimize the total weight. The CAD files of the prototypes of the EDT's. The damping characteristics of the manufactured EDT's are evaluated and compared with the corresponding characteristics obtained by conventional solid damping treatments in order to emphasize the importance of using optimally configured damping treatment to achieve high damping characteristics. The presented procedures are invaluable for designing efficient damping treatments for many military and civilian structures whose vibrations and noise must be effectively controlled.

  20. On the modal damping ratios of shear-type structures equipped with Rayleigh damping systems

    NASA Astrophysics Data System (ADS)

    Trombetti, T.; Silvestri, S.

    2006-04-01

    The effects of added manufactured viscous dampers upon shear-type structures are analytically investigated here for the class of Rayleigh damping systems. The definitions of mass proportional damping (MPD) and stiffness proportional damping (SPD) systems are briefly recalled and their physical counterpart is derived. From basic physics, a detailed mathematical demonstration that the first modal damping ratio of a structure equipped with the MPD system is always larger than the first modal damping ratio of a structure equipped with the SPD system is provided here. All results are derived for the class of structures characterised by constant values of lateral stiffness and storey mass, under the equal "total size" constraint. The paper also provides closed form demonstrations of other properties of modal damping ratios which further indicate that the MPD and the SPD systems are respectively characterised by the largest and the smallest damping efficiency among Rayleigh damping systems subjected to base excitation. A numerical application with realistic data corresponding to an actual seven-storey building structure is presented to illustrate and verify the theoretical findings.

  1. Co-Cultivation of Fungal and Microalgal Cells as an Efficient System for Harvesting Microalgal Cells, Lipid Production and Wastewater Treatment

    PubMed Central

    Wrede, Digby; Taha, Mohamed; Miranda, Ana F.; Kadali, Krishna; Stevenson, Trevor; Ball, Andrew S.; Mouradov, Aidyn

    2014-01-01

    The challenges which the large scale microalgal industry is facing are associated with the high cost of key operations such as harvesting, nutrient supply and oil extraction. The high-energy input for harvesting makes current commercial microalgal biodiesel production economically unfeasible and can account for up to 50% of the total cost of biofuel production. Co-cultivation of fungal and microalgal cells is getting increasing attention because of high efficiency of bio-flocculation of microalgal cells with no requirement for added chemicals and low energy inputs. Moreover, some fungal and microalgal strains are well known for their exceptional ability to purify wastewater, generating biomass that represents a renewable and sustainable feedstock for biofuel production. We have screened the flocculation efficiency of the filamentous fungus A. fumigatus against 11 microalgae representing freshwater, marine, small (5 µm), large (over 300 µm), heterotrophic, photoautotrophic, motile and non-motile strains. Some of the strains are commercially used for biofuel production. Lipid production and composition were analysed in fungal-algal pellets grown on media containing alternative carbon, nitrogen and phosphorus sources contained in wheat straw and swine wastewater, respectively. Co-cultivation of algae and A. fumigatus cells showed additive and synergistic effects on biomass production, lipid yield and wastewater bioremediation efficiency. Analysis of fungal-algal pellet's fatty acids composition suggested that it can be tailored and optimised through co-cultivating different algae and fungi without the need for genetic modification. PMID:25419574

  2. Co-cultivation of fungal and microalgal cells as an efficient system for harvesting microalgal cells, lipid production and wastewater treatment.

    PubMed

    Wrede, Digby; Taha, Mohamed; Miranda, Ana F; Kadali, Krishna; Stevenson, Trevor; Ball, Andrew S; Mouradov, Aidyn

    2014-01-01

    The challenges which the large scale microalgal industry is facing are associated with the high cost of key operations such as harvesting, nutrient supply and oil extraction. The high-energy input for harvesting makes current commercial microalgal biodiesel production economically unfeasible and can account for up to 50% of the total cost of biofuel production. Co-cultivation of fungal and microalgal cells is getting increasing attention because of high efficiency of bio-flocculation of microalgal cells with no requirement for added chemicals and low energy inputs. Moreover, some fungal and microalgal strains are well known for their exceptional ability to purify wastewater, generating biomass that represents a renewable and sustainable feedstock for biofuel production. We have screened the flocculation efficiency of the filamentous fungus A. fumigatus against 11 microalgae representing freshwater, marine, small (5 µm), large (over 300 µm), heterotrophic, photoautotrophic, motile and non-motile strains. Some of the strains are commercially used for biofuel production. Lipid production and composition were analysed in fungal-algal pellets grown on media containing alternative carbon, nitrogen and phosphorus sources contained in wheat straw and swine wastewater, respectively. Co-cultivation of algae and A. fumigatus cells showed additive and synergistic effects on biomass production, lipid yield and wastewater bioremediation efficiency. Analysis of fungal-algal pellet's fatty acids composition suggested that it can be tailored and optimised through co-cultivating different algae and fungi without the need for genetic modification.

  3. Modulation of the pro-inflammatory cytokines and matrix metalloproteinases production in co-cultivated human keratinocytes and melanocytes.

    PubMed

    Decean, H; Perde-Schrepler, M; Tatomir, C; Fischer-Fodor, E; Brie, I; Virag, P

    2013-10-01

    The human epidermis exerts immunoregulatory functions through the variety of cytokines and other molecules elaborated by keratinocytes and melanocytes. Their constitutive production is very low; however, considerably increased upon stimulation. In vivo, keratinocytes and melanocytes have a typical exposure in the skin, referred as melanocyte epidermal unit. In the present study we co-cultivated these cells in vitro proposing to elucidate some communication links in close cell-to-cell association. We assessed the amounts of IL-6, IL-8, and matrix metalloproteinases (MMP-2 and MMP-9) in individually and co-cultured cells, exposed or not to UVB radiation. Normal human epidermal keratinocytes and melanocytes were grown in specific media and supplements. Cells were exposed to UVB radiation (100 mJ/cm(2)) to create comparable stress to the environmental one. Cytokines were determined with ELISA and confirmed with Western blot and metalloproteinases with gel zimography. Pure cultures of keratinocytes and melanocytes released low amounts of cytokines and metalloproteinases, these secretions being enhanced by UVB irradiation. In co-cultures, the cell-to-cell proximity triggered signals which markedly augmented the cytokines' secretions, whereas metalloproteinases were down-regulated. UVB irradiation did not influence either of these secretions in co-cultures. Concurrently with the highest levels of the pro-inflammatory cytokines, MMP-9 was up-regulated creating pro-inflammatory conditions and premises for changes in cellular survival, differentiation and phenotype. A complex network of interactions occurred between keratinocytes and melanocytes in co-cultures, resulting in modulated pro-inflammatory cytokines and metalloproteinases productions. Therefore, any disturbances in the microenvironmental signaling system and its molecular constituents may result in inflammation or even tumorigenesis in the epidermis.

  4. Decoherence and Landau-Damping

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2005-12-01

    The terminologies, decoherence and Landau damping, are often used concerning the damping of a collective instability. This article revisits the difference and relation between decoherence and Landau damping. A model is given to demonstrate how Landau damping affects the rate of damping coming from decoherence.

  5. Turbine blade damping study

    NASA Technical Reports Server (NTRS)

    Dominic, R. J.

    1984-01-01

    Research results and progress on the performance of bladed systems is reported the different topics discussed include: the study of turbine blade damping; forced vibrations of friction damped beam moistures in two dimensions; and a users manual for a computer program for dynamic analysis of bladed systems.

  6. Turbojet engine blade damping

    NASA Technical Reports Server (NTRS)

    Srinivasan, A. V.; Cutts, D. G.; Sridhar, S.

    1981-01-01

    The potentials of various sources of nonaerodynamic damping in engine blading are evaluated through a combination of advanced analysis and testing. The sources studied include material hysteresis, dry friction at shroud and root disk interfaces as well as at platform type external dampers. A limited seris of tests was conducted to evaluate damping capacities of composite materials (B/AL, B/AL/Ti) and thermal barrier coatings. Further, basic experiments were performed on titanium specimens to establish the characteristics of sliding friction and to determine material damping constants J and n. All the tests were conducted on single blades. Mathematical models were develthe several mechanisms of damping. Procedures to apply this data to predict damping levels in an assembly of blades are developed and discussed.

  7. Variations of hybrid damping

    NASA Astrophysics Data System (ADS)

    Lam, Margaretha J.; Inman, Daniel J.; Saunders, William R.

    1998-06-01

    Damping is important to structures and can be achieved through the addition of viscoelastic materials (VEM). The damping of the VEM is enhanced if a constraining layer is attached to the VEM. If this constraining layer is active, the treatment is called active constrained layer damping (ACLD). In the last few years, ACLD has proven to be superior in vibration control to active or passive damping. The active element makes ACLD more effective than passive constrained layer damping. It also provides a fail-safe in case of breakdown of the active element that is not present for purely active control. It is shown that the control effort needed to damp vibration using ACLD can be significantly higher than purely active control. In order to combine the inherent damping of passive control with the effectiveness of the active element, this paper will explore different variations of active, passive and hybrid damping. Some of the variations include: passive constrained layer damping (PCLD) separate from active element but on the same side of beam, PCLD separate from active on the opposite side of the beam, and active element underneath PCLD. The discretized system equations will be obtained using assumed modes method and Lagrange's equation. The damping will be modeled using the Golla-Hughes-McTavish (GHM) method. The optimal placement and size of the active, passive, ACLD and hybrid treatments will be found using different schemes. The issue of overshoot and settling time of the output and control force using LQR will be addressed, as well as the control effort, passive and active vibration suppression, and LQR cost function. It will be shown that the hybrid treatments are capable of greater vibration control for lower control effort for different optimization schemes. 31

  8. Spatial cyclotron damping

    NASA Technical Reports Server (NTRS)

    Olson, C. L.

    1970-01-01

    To examine spatial electron cyclotron damping in a uniform Vlasov plasma, it is noted that the plasma response to a steady-state transverse excitation consists of several terms (dielectric-pole, free-streaming, and branch-cut), but that the cyclotron-damped pole term is the dominant term for z l = c/w sub ce provided (w sub pe/w sub ce) squared (c/a) is much greater than 1. If the latter inequality does not hold, then the free-streaming and branch-cut terms persist well past z = c/w sub ce as w sub 1 approaches w sub ce, making experimental measurement of cyclotron damping essentially impossible. Considering only (w sub pe/w sub ce) squared (c/a) is much greater than 1, it is shown how collisional effects should be estimated and how a finite-width excitation usually has little effect on the cyclotron-damped part of the response. Criteria is established concerning collisional damping, measurable damping length sizes, and allowed uncertainty in the magnetic field Beta. Results of numerical calculations, showing the regions in the appropriate parameter spaces that meet these criteria, are presented. From these results, one can determine the feasibility of, or propose parameter values for, an experiment designed to measure spatial cyclotron damping. It is concluded that the electron temperature T sub e should be at least 1 ev., and preferably 10 ev. or higher, for a successful experiment.

  9. Control System Damps Vibrations

    NASA Technical Reports Server (NTRS)

    Kopf, E. H., Jr.; Brown, T. K.; Marsh, E. L.

    1983-01-01

    New control system damps vibrations in rotating equipment with help of phase-locked-loop techniques. Vibrational modes are controlled by applying suitable currents to drive motor. Control signals are derived from sensors mounted on equipment.

  10. Co-cultivation of mutant Penicillium oxalicum SAU(E)-3.510 and Pleurotus ostreatus for simultaneous biosynthesis of xylanase and laccase under solid-state fermentation.

    PubMed

    Dwivedi, Pallavi; Vivekanand, V; Pareek, Nidhi; Sharma, Amit; Singh, Rajesh P

    2011-10-01

    Co-cultivation of mutant Penicillium oxalicum SAU(E)-3.510 and Pleurotus ostreatus MTCC 1804 was evaluated for the production of xylanase-laccase mixture under solid-state fermentation (SSF) condition. Growth compatibility between mutant P. oxalicum SAU(E)-3.510 and white rot fungi (P. ostreatus MTCC 1804, Trametes hirsuta MTCC 136 and Pycnoporus sp. MTCC 137) was analyzed by growing them on potato dextrose agar plate. Extracellular enzyme activities were determined spectrophotometrically. Under derived conditions, paired culturing of mutant P. oxalicum SAU(E)-3.510 and P. ostreatus MTCC 1804 resulted in 58% and 33% higher levels of xylanase and laccase production, respectively. A combination of sugarcane bagasse and black gram husk in a ratio of 3:1 was found to be the most ideal solid substrate and support for fungal colonization and enzyme production during co-cultivation. Maximum levels of xylanase (8205.31 ± 168.31 IU g(-1)) and laccase (375.53 ± 34.17 IU g(-1)) during SSF were obtained by using 4 g of solid support with 80% of moisture content. Furthermore, expressions of both xylanase and laccase were characterized during mixed culture by zymogram analysis. Improved levels of xylanase and laccase biosynthesis were achieved by co-culturing the mutant P. oxalicum SAU(E)-3.510 and P. ostreatus MTCC 1804. This may be because of efficient substrate utilization as compared to their respective monocultures in the presence of lignin degradation compounds because of synergistic action of xylanase and laccase. Understanding and developing the process of co-cultivation appears productive for the development of mixed enzyme preparation with tremendous potential for biobleaching.

  11. DAMPs, ageing, and cancer: The 'DAMP Hypothesis'.

    PubMed

    Huang, Jin; Xie, Yangchun; Sun, Xiaofang; Zeh, Herbert J; Kang, Rui; Lotze, Michael T; Tang, Daolin

    2015-11-01

    Ageing is a complex and multifactorial process characterized by the accumulation of many forms of damage at the molecular, cellular, and tissue level with advancing age. Ageing increases the risk of the onset of chronic inflammation-associated diseases such as cancer, diabetes, stroke, and neurodegenerative disease. In particular, ageing and cancer share some common origins and hallmarks such as genomic instability, epigenetic alteration, aberrant telomeres, inflammation and immune injury, reprogrammed metabolism, and degradation system impairment (including within the ubiquitin-proteasome system and the autophagic machinery). Recent advances indicate that damage-associated molecular pattern molecules (DAMPs) such as high mobility group box 1, histones, S100, and heat shock proteins play location-dependent roles inside and outside the cell. These provide interaction platforms at molecular levels linked to common hallmarks of ageing and cancer. They can act as inducers, sensors, and mediators of stress through individual plasma membrane receptors, intracellular recognition receptors (e.g., advanced glycosylation end product-specific receptors, AIM2-like receptors, RIG-I-like receptors, and NOD1-like receptors, and toll-like receptors), or following endocytic uptake. Thus, the DAMP Hypothesis is novel and complements other theories that explain the features of ageing. DAMPs represent ideal biomarkers of ageing and provide an attractive target for interventions in ageing and age-associated diseases. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Damping modeling in Timoshenko beams

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Wang, Y.

    1992-01-01

    Theoretical and numerical results of damping model studies for composite material beams using the Timoshenko theory is presented. Based on the damping models developed for Euler-Bernoulli beams, the authors develop damping methods for both bending and shear in investigation of Timoshenko beams. A computational method for the estimation of the damping parameters is given. Experimental data with high-frequency excitation were used to test Timoshenko beam equations with different types of damping models for bending and shear in various combinations.

  13. Public health and economic impact of dampness and mold

    SciTech Connect

    Mudarri, David; Fisk, William J.

    2007-06-01

    The public health risk and economic impact of dampness and mold exposures was assessed using current asthma as a health endpoint. Individual risk of current asthma from exposure to dampness and mold in homes from Fisk et al. (2007), and asthma risks calculated from additional studies that reported the prevalence of dampness and mold in homes were used to estimate the proportion of U.S. current asthma cases that are attributable to dampness and mold exposure at 21% (95% confidence internal 12-29%). An examination of the literature covering dampness and mold in schools, offices, and institutional buildings, which is summarized in the appendix, suggests that risks from exposure in these buildings are similar to risks from exposures in homes. Of the 21.8 million people reported to have asthma in the U.S., approximately 4.6 (2.7-6.3) million cases are estimated to be attributable to dampness and mold exposure in the home. Estimates of the national cost of asthma from two prior studies were updated to 2004 and used to estimate the economic impact of dampness and mold exposures. By applying the attributable fraction to the updated national annual cost of asthma, the national annual cost of asthma that is attributable to dampness and mold exposure in the home is estimated to be $3.5 billion ($2.1-4.8 billion). Analysis indicates that exposure to dampness and mold in buildings poses significant public health and economic risks in the U.S. These findings are compatible with public policies and programs that help control moisture and mold in buildings.

  14. Alteration of white-rot basidiomycetes cellulase and xylanase activities in the submerged co-cultivation and optimization of enzyme production by Irpex lacteus and Schizophyllum commune.

    PubMed

    Metreveli, Eka; Kachlishvili, Eva; Singer, Steven W; Elisashvili, Vladimir

    2017-10-01

    Mono and dual cultures of four white-rot basidiomycete species were evaluated for cellulase and xylanase activity under submerged fermentation conditions. Co-cultivation of Pycnoporus coccineus or Trametes hirsuta with Schizophyllum commune displayed antagonistic interactions resulting in the decrease of endoglucanase and total cellulase activities. In contrast, increases in cellulase and xylanase activity were revealed through the compatible interactions of Irpex lacteus with S. commune. Co-cultivation conditions were optimized for maximum enzyme production by I. lacteus and S. commune, the best producers of cellulase/xylanase and β-glucosidase, respectively. An optimized medium for the target enzyme production by the mixed culture was established in a laboratory fermenter yielding 7U/mL total cellulase, 142U/mL endoglucanase, 104U/mL xylanase, and 5.2U/mL β-glucosidase. The dual culture approach resulted in an enzymatic mixture with 11% improved lignocellulose saccharification potential compared to enzymes from a monoculture of I. lacteus. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. The synergistic effect on production of lignin-modifying enzymes through submerged co-cultivation of Phlebia radiata, Dichomitus squalens and Ceriporiopsis subvermispora using agricultural residues.

    PubMed

    Dong, Ya-Chen; Wang, Wei; Hu, Zhong-Ce; Fu, Ming-Liang; Chen, Qi-He

    2012-06-01

    The lignin-modifying enzymes (LMEs) play an important role in decomposition of agricultural residues, which contain a certain amount of lignin. In this study, the production of LMEs by three co-cultivated combinations of Phlebia radiata, Dichomitus squalens and Ceriporiopsis subvermispora and the respective monocultures was comparatively investigated. Laccase and manganese peroxidases (MnP) were significantly promoted in the co-culture of P. radiata and D. squalens, and corncob was verified to be beneficial for laccase and MnP production. Moreover, laccase production by co-culture of P. radiata and D. squalens with high ratio of glucose to nitrogen was higher than low ratio under carbon- and nitrogen-meager conditions. New laccase isoenzymes measured by Native-PAGE were stimulated by co-cultured P. radiata with D. squalens or C. subvermispora, respectively, growing in the defined medium containing corncob, but the expression of laccase was greatly restrained by the co-culturing of D. squalens with C. subvermispora. This study showed that the synergistic and depressing effects of co-cultivation of P. radiata, D. squalens and C. subvermispora on LMEs were species specific.

  16. Damping in Space Constructions

    NASA Astrophysics Data System (ADS)

    de Vreugd, Jan; de Lange, Dorus; Winters, Jasper; Human, Jet; Kamphues, Fred; Tabak, Erik

    2014-06-01

    Monolithic structures are often used in optomechanical designs for space applications to achieve high dimensional stability and to prevent possible backlash and friction phenomena. The capacity of monolithic structures to dissipate mechanical energy is however limited due to the high Q-factor, which might result in high stresses during dynamic launch loads like random vibration, sine sweeps and shock. To reduce the Q-factor in space applications, the effect of constrained layer damping (CLD) is investigated in this work. To predict the damping increase, the CLD effect is implemented locally at the supporting struts in an existing FE model of an optical instrument. Numerical simulations show that the effect of local damping treatment in this instrument could reduce the vibrational stresses with 30-50%. Validation experiments on a simple structure showed good agreement between measured and predicted damping properties. This paper presents material characterization, material modeling, numerical implementation of damping models in finite element code, numerical results on space hardware and the results of validation experiments.

  17. Damped flexible seal

    SciTech Connect

    DuBois, Neil J.; Amaral, Antonio M.

    1992-10-27

    A damped flexible seal assembly for a torpedo isolates the tailcone thereof rom vibrational energy present in the drive shaft assembly. A pair of outside flanges, each of which include an inwardly facing groove and an O-ring constrained therein, provide a watertight seal against the outer non-rotating surface of the drive shaft assembly. An inside flange includes an outwardly-facing groove and an O-ring constrained therein, and provides a watertight seal against the inner surface of the tail cone. Two cast-in-place elastomeric seals provide a watertight seal between the flanges and further provide a damping barrier between the outside flanges and the inside flanges for damping vibrational energy present in the drive shaft assembly before the energy can reach the tailcone through the seal assembly.

  18. Damping of thermoacoustic oscillations

    NASA Technical Reports Server (NTRS)

    Tward, E.; Mason, P. V.

    1982-01-01

    A commonly encountered and troublesome problem in cryogenic systems is related to the occurrence of thermoacoustic oscillations (TAO). The oscillations are accompanied by large heat fluxes which can cause large increases in the boiloff from dewars. Such a boiloff can lead to a serious degradation in performance. It appears, therefore, highly advisable to incorporate mechanisms for damping TAO in those parts of the system where there oscillations might occur. The present investigation is concerned with the criteria for the design of such damping mechanisms. Attention is given to the theory regrading the suppression of TAO, a damper consisting of a capillary with a surge tank, and porous solid dampers.

  19. Measurement of mobility and damping of floors

    NASA Astrophysics Data System (ADS)

    White, M. F.; Liasjø, K. H.

    1982-04-01

    Point mobility and damping (loss factor) were measured for different types of wooden and concrete floors in occupied buildings. A vertically applied excitation force was used. Various types of woodworking machines and workshop equipment were present during the tests in order to give a practical measure of floor damping. For comparison, the characteristics of a free concrete slab with point supports at each corner, a newly constructed unfurnished office building, and an experimental floating floor were also measured. Measurements were made in three frequency bands in the range from 5 to 1600 Hz. For concrete floors maximum point mobility was typically in the region 10 -4-10 -7 m/N s, and for wooden floors, typically 10 -2-10 -4 m/N s. Loss factors were typically in the region 0.01-0.6, depending on floor construction and frequency.

  20. Monitoring of soft high damping elastomeric bearings for earthquake isolation

    SciTech Connect

    Coveney, V.A.; Kuroda, T.; Kobatake, M.; Nita, Y.; Kulak, R.F.; Chang, Y.W.; Seidensticker, R.W.

    1993-07-01

    Over the last 20 years several practical systems for the protection of buildings and their contents against the effects of earthquakes were developed. These systems rely on effectively decoupling the building from the strong horizontal ground accelerations that are some of the most damaging features of an earthquake. The isolation of small buildings against earthquakes poses particular problems for high damping elastomer. systems. It was recognized that one way to overcome these problems was to use elastomers with particularly low moduli, high damping and other necessary characteristics. This paper describes some key features of the development of soft high damping natural bearings. Their use for the earthquake isolation of a small highly instrumented building at Tohoku University in Sendai, Japan is discussed. The paper focuses on the monitoring of the bearings during production and their performance in situ under static and earthquake (dynamic) conditions.

  1. The DAMPE Neutron Detector

    NASA Astrophysics Data System (ADS)

    Yan, Zhang; Tao, Ma; Yongyi, Huang

    2016-07-01

    The first Chinese space observatory DAMPE (DArk Matter Particle Explorer) was successfully launched on Dec. 17th, 2015. One major scientific object of DAMPE is to measure electrons between 5GeV to 10TeV with excellent energy resolution (1.5% at 800GeV) to search for possible dark matter signatures. The detector consists of four subsystems: a plastic scintillator detector (PSD), a silicon-tungsten tracker (STK), a BGO calorimeter (BGO), and a neutron detector (NUD). The NUD on board DAMPE is designed to detect moderated neutrons via the boron capture of thermal neutrons in boron-doped plastics. Given the fact that hadron showers initiated in the BGO calorimeter by incident nuclei tend to be followed by significantly more neutron activities comparing to electromagnetic cascades triggered by electrons, the NUD provides an additional order of magnitude hadron rejection capability to improve the overall e/p discrimination of DAMPE up to 10 ^{5}. Preliminary analysis of the in-orbit data is given, together with comparisons to the results obtained by a detailed GEANT4 simulation of the NUD instrument.

  2. 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.

  3. Nutational Damping Revisited

    NASA Astrophysics Data System (ADS)

    Burns, J. A.; Sharma, I.

    2000-10-01

    Motivated by the recent detection of complex rotational states for several asteroids and comets, as well as by the ongoing and planned spacecraft missions to such bodies, which should allow their rotational states to be accurately determined, we revisit the problem of the nutational damping of small solar system bodies. The nutational damping of asteroids has been approximately analyzed by Prendergast (1958), Burns and Safronov (1973), and Efroimsky and Lazarian (2000). Many other similar dynamical studies concern planetary wobble decay (e.g., Peale 1973; Yoder and Ward 1979), interstellar dust grain alignment (e.g., Purcell 1979; Lazarian and Efroimsky 1999) and damping of Earth's Chandler wobble (Lambeck 1980). Recall that rotational energy loss for an isolated body aligns the body's angular momentum vector with its axis of maximum inertia. Assuming anelastic dissipation, simple dimensional analysis determines a functional form of the damping timescale, on which all the above authors agree. However, the numerical coefficients of published results are claimed to differ by orders of magnitude. Differences have been ascribed to absent physics, to solutions that fail to satisfy boundary conditions perfectly, and to unphysical choices for the Q parameter. The true reasons for the discrepancy are unclear since, despite contrary claims, the full 3D problem (nutational damping of an anelastic ellipsoid) is analytically intractable so far. To move the debate forward, we compare the solution of a related 2D problem to the expressions found previously, and we present results from a finite element model. On this basis, we feel that previous rates for the decay of asteroidal tumbling (Harris 1994), derived from Burns and Safronov (1973), are likely to be accurate, at least to a factor of a few. Funded by NASA.

  4. Damping formulas and experimental values of damping in flutter models

    NASA Technical Reports Server (NTRS)

    Coleman, Robert P

    1940-01-01

    The problem of determining values of structural damping for use in flutter calculations is discussed. The concept of equivalent viscous damping is reviewed and its relation to the structural damping coefficient g introduced in NACA Technical Report No. 685 is shown. The theory of normal modes is reviewed and a number of methods are described for separating the motions associated with different modes. Equations are developed for use in evaluating the damping parameters from experimental data. Experimental results of measurements of damping in several flutter models are presented.

  5. Phycospheric Native Bacteria Pelagibaca bermudensis and Stappia sp. Ameliorate Biomass Productivity of Tetraselmis striata (KCTC1432BP) in Co-cultivation System through Mutualistic Interaction

    PubMed Central

    Park, Jungsoo; Park, Bum Soo; Wang, Pengbin; Patidar, Shailesh K.; Kim, Jin Ho; Kim, Sae-Hee; Han, Myung-Soo

    2017-01-01

    Effective sustainable algal cultivation techniques are essential for mass production of the marine microalga Tetraselmis for biofuel and array of co-products. The phycospheric communities affect the microalgal growth and metabolism through various allelochemical and nutrient interactions; hence, their potential to affect the quantity and quality of both biomass and bioproducts is significant. In the present study, we have screened the phycospheric communities of biofuel producing Tetraselmis striata (KCTC1432BP). A total of 26 bacterial strains were isolated and identified from the phycosphere of T. striata mass culture. Then, each bacterial strain was tested in co-cultivation conditions with T. striata for evaluating its growth promoting and inhibitory effects. Among these all strains, two promising strains (Pelagibaca bermudensis KCTC 13073BP and Stappia sp. KCTC 13072BP) were selected because of their maximum growth promoting effects and mutualistic interactions. The growth rate, biomass productivity, lipid contents, and fatty acids were analyzed during their combined growth in O3 media and compared with axenic growth of T. striata. Later, growth promoting mechanisms in the co-cultivation environment were investigated for these promising bacterial strains under replete and limited conditions of nutrients (nitrate, phosphate, and vitamin B12). The growth promoting potential of P. bermudensis was illustrated by the two fold enhancement in biomass productivity. These bacteria are promising for microalgal cultivation without any negative effects on the native seawater bacterial communities, as revealed by next generation sequencing analysis. This study represents, to date, the first report highlighting the role of phycospheric growth promoting bacteria of promising biofuel feedstock T. striata. PMID:28321229

  6. Sampling considerations for modal analysis with damping

    NASA Astrophysics Data System (ADS)

    Park, Jae Young; Wakin, Michael B.; Gilbert, Anna C.

    2015-03-01

    Structural health monitoring (SHM) systems are critical for monitoring aging infrastructure (such as buildings or bridges) in a cost-effective manner. Wireless sensor networks that sample vibration data over time are particularly appealing for SHM applications due to their flexibility and low cost. However, in order to extend the battery life of wireless sensor nodes, it is essential to minimize the amount of vibration data these sensors must collect and transmit. In recent work, we have studied the performance of the Singular Value Decomposition (SVD) applied to the collection of data and provided new finite sample analysis characterizing conditions under which this simple technique{also known as the Proper Orthogonal Decomposition (POD){can correctly estimate the mode shapes of the structure. Specifically, we provided theoretical guarantees on the number and duration of samples required in order to estimate a structure's mode shapes to a desired level of accuracy. In that previous work, however, we considered simplified Multiple-Degree-Of-Freedom (MDOF) systems with no damping. In this paper we consider MDOF systems with proportional damping and show that, with sufficiently light damping, the POD can continue to provide accurate estimates of a structure's mode shapes. We support our discussion with new analytical insight and experimental demonstrations. In particular, we study the tradeoffs between the level of damping, the sampling rate and duration, and the accuracy to which the structure's mode shapes can be estimated.

  7. Damping of thermoacoustic oscillations

    SciTech Connect

    Tward, E.; Mason, P.V.

    1982-01-01

    The design criteria for the damping mechanism required to suppress thermoacoustic oscillation is discussed. The theory is presented with formulas stated. Incident acoustic wave generation is illustrated with the pipes and damper positions indicated. Capillary and surge tank functions are described with illustrations and formulas relevant to the thermoacoustic oscillation process. Porous solid dampers were introduced which used glass wool. The problem of damping of the thermoacoustic oscillation appears to be solvable in many applications through the use of an orifice and surge tank. This device can be installed either as a termination in an oscillating pipe or in a branch. It is suggested that such a device be incorporated into cryogenic systems whenever thermoacoustic oscillations could cause a problem.

  8. Design, analysis, and testing of high frequency passively damped struts

    NASA Technical Reports Server (NTRS)

    Yiu, Y. C.; Davis, L. Porter; Napolitano, Kevin; Ninneman, R. Rory

    1993-01-01

    Objectives of the research are: (1) to develop design requirements for damped struts to stabilize control system in the high frequency cross-over and spill-over range; (2) to design, fabricate and test viscously damped strut and viscoelastically damped strut; (3) to verify accuracy of design and analysis methodology of damped struts; and (4) to design and build test apparatus, and develop data reduction algorithm to measure strut complex stiffness. In order to meet the stringent performance requirements of the SPICE experiment, the active control system is used to suppress the dynamic responses of the low order structural modes. However, the control system also inadvertently drives some of the higher order modes unstable in the cross-over and spill-over frequency range. Passive damping is a reliable and effective way to provide damping to stabilize the control system. It also improves the robustness of the control system. Damping is designed into the SPICE testbed as an integral part of the control-structure technology.

  9. On damping mechanisms in beams

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Inman, D. J.

    1991-01-01

    A partial differential equation model of a cantilevered beam with a tip mass at its free end is used to study damping in a composite. Four separate damping mechanisms consisting of air damping, strain rate damping, spatial hysteresis and time hysteresis are considered experimentally. Dynamic tests were performed to produce time histories. The time history data is then used along with an approximate model to form a sequence of least squares problems. The solution of the least squares problem yields the estimated damping coefficients. The resulting experimentally determined analytical model is compared with the time histories via numerical simulation of the dynamic response. The procedure suggested here is compared with a standard modal damping ratio model commonly used in experimental modal analysis.

  10. On damping mechanisms in beams

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Inman, D. J.

    1989-01-01

    A partial differential equation model of a cantilevered beam with a tip mass at its free end is used to study damping in a composite. Four separate damping mechanisms consisting of air damping, strain rate damping, spatial hysteresis and time hysteresis are considered experimentally. Dynamic tests were performed to produce time histories. The time history data is then used along with an approximate model to form a sequence of least squares problems. The solution of the least squares problem yields the estimated damping coefficients. The resulting experimentally determined analytical model is compared with the time histories via numerical simulation of the dynamic response. The procedure suggested here is compared with a standard modal damping ratio model commonly used in experimental modal analysis.

  11. Magnetically Damped Furnace (MDF)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Magnetically Damped Furnace (MDF) breadboard is being developed in response to NASA's mission and goals to advance the scientific knowledge of microgravity research, materials science, and related technologies. The objective of the MDF is to dampen the fluid flows due to density gradients and surface tension gradients in conductive melts by introducing a magnetic field during the sample processing. The MDF breadboard will serve as a proof of concept that the MDF performance requirements can be attained within the International Space Station resource constraints.

  12. Magnetically Damped Furnace (MDF)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Magnetically Damped Furnace (MDF) breadboard is being developed in response to NASA's mission and goals to advance the scientific knowledge of microgravity research, materials science, and related technologies. The objective of the MDF is to dampen the fluid flows due to density gradients and surface tension gradients in conductive melts by introducing a magnetic field during the sample processing. The MDF breadboard will serve as a proof of concept that the MDF performance requirements can be attained within the International Space Station resource constraints.

  13. Damping characteristics of friction damped braced frame and its effectiveness in the mega-sub controlled structure system

    NASA Astrophysics Data System (ADS)

    Lian, Yeda; Zhang, Xunan; Sheldon, Cherry

    2007-06-01

    Based on energy dissipation and structural control principle, a new structural configuration, called the mega-sub controlled structure (MSCS) with friction damped braces (FDBs), is first presented. Meanwhile, to calculate the damping coefficient in the slipping state a new analytical method is proposed. The damping characteristics of one-storey friction damped braced frame (FDBF) are investigated, and the influence of the structural parameters on the energy dissipation and the practical engineering design are discussed. The nonlinear dynamic equations and the analytical model of the MSCS with FDBs are established. Three building structures with different structural configurations, which were designed with reference to the conventional mega-sub structures such as used in Tokyo City Hall, are comparatively investigated. The results illustrate that the structure presented in the paper has excellent dynamic properties and satisfactory control effectiveness.

  14. The Joint Damping Experiment (JDX)

    NASA Technical Reports Server (NTRS)

    Folkman, Steven L.; Bingham, Jeff G.; Crookston, Jess R.; Dutson, Joseph D.; Ferney, Brook D.; Ferney, Greg D.; Rowsell, Edwin A.

    1997-01-01

    The Joint Damping Experiment (JDX), flown on the Shuttle STS-69 Mission, is designed to measure the influence of gravity on the structural damping of a high precision three bay truss. Principal objectives are: (1) Measure vibration damping of a small-scale, pinjointed truss to determine how pin gaps give rise to gravity-dependent damping rates; (2) Evaluate the applicability of ground and low-g aircraft tests for predicting on-orbit behavior; and (3) Evaluate the ability of current nonlinear finite element codes to model the dynamic behavior of the truss. Damping of the truss was inferred from 'Twang' tests that involve plucking the truss structure and recording the decay of the oscillations. Results are summarized as follows. (1) Damping, rates can change by a factor of 3 to 8 through changing the truss orientation; (2) The addition of a few pinned joints to a truss structure can increase the damping by a factor as high as 30; (3) Damping is amplitude dependent; (4) As gravity induced preloads become large (truss long axis perpendicular to gravity vector) the damping is similar to non-pinjointed truss; (5) Impacting in joints drives higher modes in structure; (6) The torsion mode disappears if gravity induced preloads are low.

  15. Induction of Diverse Bioactive Secondary Metabolites from the Mangrove Endophytic Fungus Trichoderma sp. (Strain 307) by Co-Cultivation with Acinetobacter johnsonii (Strain B2)

    PubMed Central

    Zhang, Liuhong; Niaz, Shah Iram; Khan, Dilfaraz; Wang, Zhen; Zhu, Yonghong; Zhou, Haiyun; Lin, Yongcheng; Li, Jing; Liu, Lan

    2017-01-01

    Two new sesquiterpenes, microsphaeropsisin B (1) and C (2), and two new de-O-methyllasiodiplodins, (3R, 7R)-7-hydroxy-de-O-methyllasiodiplodin (4) and (3R)-5-oxo-de-O-methyllasiodiplodin (5), together with one new natural product (6) and twelve known compounds (3, 7–17), were isolated from the co-cultivation of mangrove endophytic fungus Trichoderma sp. 307 and aquatic pathogenic bacterium Acinetobacter johnsonii B2. Their structures, including absolute configurations, were elucidated by extensive analysis of spectroscopic data, electronic circular dichroism, Mo2(AcO)4-induced circular dichroism, and comparison with reported data. All of the isolated compounds were tested for their α-glucosidase inhibitory activity and cytotoxicity. New compounds 4 and 5 exhibited potent α-glucosidase inhibitory activity with IC50 values of 25.8 and 54.6 µM, respectively, which were more potent than the positive control (acarbose, IC50 = 703.8 µM). The good results of the tested bioactivity allowed us to explore α-glucosidase inhibitors in lasiodiplodins. PMID:28208607

  16. Differential gene expression in Xylella fastidiosa 9a5c during co-cultivation with the endophytic bacterium Methylobacterium mesophilicum SR1.6/6.

    PubMed

    Dourado, Manuella Nóbrega; Santos, Daiene Souza; Nunes, Luiz Roberto; Costa de Oliveira, Regina Lúcia Batista da; de Oliveira, Marcus Vinicius; Araújo, Welington Luiz

    2015-12-01

    Xylella fastidiosa, the causal agent of citrus variegated chlorosis (CVC), colonizes plant xylem, reducing sap flow, and inducing internerval chlorosis, leaf size reduction, necrosis, and harder and smaller fruits. This bacterium may be transmitted from plant to plant by sharpshooter insects, including Bucephalogonia xanthopis. The citrus endophytic bacterium Methylobacterium mesophilicum SR1.6/6 colonizes citrus xylem and previous studies showed that this strain is also transferred from plant to plant by B. xanthopis (Insecta), suggesting that this endophytic bacterium may interact with X. fastidiosa in planta and inside the insect vector during co-transmission by the same insect vector. To better understand the X. fastidiosa behavior in the presence of M. mesophilicum, we evaluated the X. fastidiosa transcriptional profile during in vitro interaction with M. mesophilicum SR1.6/6. The results showed that during co-cultivation, X. fastidiosa down-regulated genes related to growth and up-regulated genes related to energy production, stress, transport, and motility, suggesting the existence of a specific adaptive response to the presence of M. mesophilicum in the culture medium.

  17. Enhanced methane production in an anaerobic digestion and microbial electrolysis cell coupled system with co-cultivation of Geobacter and Methanosarcina.

    PubMed

    Yin, Qi; Zhu, Xiaoyu; Zhan, Guoqiang; Bo, Tao; Yang, Yanfei; Tao, Yong; He, Xiaohong; Li, Daping; Yan, Zhiying

    2016-04-01

    The anaerobic digestion (AD) and microbial electrolysis cell (MEC) coupled system has been proved to be a promising process for biomethane production. In this paper, it was found that by co-cultivating Geobacter with Methanosarcina in an AD-MEC coupled system, methane yield was further increased by 24.1%, achieving to 360.2 mL/g-COD, which was comparable to the theoretical methane yield of an anaerobic digester. With the presence of Geobacter, the maximum chemical oxygen demand (COD) removal rate (216.8 mg COD/(L·hr)) and current density (304.3A/m(3)) were both increased by 1.3 and 1.8 fold compared to the previous study without Geobacter, resulting in overall energy efficiency reaching up to 74.6%. Community analysis demonstrated that Geobacter and Methanosarcina could coexist together in the biofilm, and the electrochemical activities of both were confirmed by cyclic voltammetry. Our study observed that the carbon dioxide content in total gas generated from the AD reactor with Geobacter was only half of that generated from the same reactor without Geobacter, suggesting that Methanosarcina may obtain the electron transferred from Geobacter for the reduction of carbon dioxide to methane. Taken together, Geobacter not only can improve the performance of the MEC system, but also can enhance methane production.

  18. Interspecific cooperation: enhanced growth, attachment and strain-specific distribution in biofilms through Azospirillum brasilense-Pseudomonas protegens co-cultivation.

    PubMed

    Pagnussat, Luciana A; Salcedo, Florencia; Maroniche, Guillermo; Keel, Christoph; Valverde, Claudio; Creus, Cecilia M

    2016-10-01

    Plant-growth-promoting bacteria belonging to Azospirillum and Pseudomonas genera are major inhabitants of the rhizosphere. Both are increasingly commercialized as crops inoculants. Interspecific interaction in the rhizosphere is critical for inoculants aptness. The objective of this work was to evaluate Azospirillum and Pseudomonas interaction in mixed biofilms by co-cultivation of the model strains Azospirillum brasilense Sp245 and Pseudomonas protegens CHA0. The results revealed enhanced growth of both strains when co-cultured in static conditions. Moreover, Sp245 biofilm formed in plastic surfaces was increased 2-fold in the presence of CHA0. Confocal microscopy revealed highly structured mixed biofilms showing Sp245 mainly on the bottom and CHA0 towards the biofilm surface. In addition, A. brasilense biofilm was thicker and denser when co-cultured with P. protegens. In a colony-colony interaction assay, Sp245 changed nearby CHA0 producing small colony phenotype, which accounts for a diffusible metabolite mediator; though CHA0 spent medium did not affect Sp245 colony phenotype. Altogether, these results point to a cooperative interaction between A. brasilense Sp245 and P. protegens CHA0 in which both strains increase their static growth and produce structured mixed biofilms with a strain-specific distribution. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  19. Surge-damping vacuum valve

    DOEpatents

    Bullock, Jack C.; Kelly, Benjamin E.

    1980-01-01

    A valve having a mechanism for damping out flow surges in a vacuum system which utilizes a slotted spring-loaded disk positioned adjacent the valve's vacuum port. Under flow surge conditions, the differential pressure forces the disk into sealing engagement with the vacuum port, thereby restricting the flow path to the slots in the disk damping out the flow surge.

  20. PUBLIC HEALTH AND ECONOMIC IMPACT OF DAMPNESS AND MOLD

    EPA Science Inventory

    There is a rapidly growing body of scientific literature examining the relationship between dampness and mold in buildings and associated health effects. Reviews by expert groups in Europe (Bornehag et al. 2001; Bornehag et al. 2004) and the United States (IOM, 2004) conclude th...

  1. PUBLIC HEALTH AND ECONOMIC IMPACT OF DAMPNESS AND MOLD

    EPA Science Inventory

    There is a rapidly growing body of scientific literature examining the relationship between dampness and mold in buildings and associated health effects. Reviews by expert groups in Europe (Bornehag et al. 2001; Bornehag et al. 2004) and the United States (IOM, 2004) conclude th...

  2. Damping measurements using operational data

    SciTech Connect

    James, G.H.; Carne, T.G.; Veers, P.S.

    1996-08-01

    The authors have measured modal damping using strain-gauge data from an operating wind turbine. This new technique for measuring modal damping is easier and less expensive than previously used methods. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. The authors have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandia 34-m Test Bed has been used to calculate modal damping ratios as a function of rotor rotation rate. This capability will allow more accurate fatigue life prediction and control.

  3. Fast recovery of transgenic submergence tolerant rice cultivars of North-East India by early co-cultivation of Agrobacterium with pre-cultured callus.

    PubMed

    Nguyen, Van Cuu; Nguyen, Van Khiem; Singh, Chongtham Henary; Devi, Guruaribam Shantibala; Reddy, Vanga Siva; Leelavathi, Sadhu

    2017-01-01

    Agro-climatic conditions of North-East India are very complex and rice cultivars present in the region have been adapted to grow under harsh environmental conditions. Germplasm present in the region is considered to possess several important and unique traits that are of importance in rice improvement programs. Genetic engineering is a powerful tool to introduce new traits into crop plants. However, not much information is available on the methods to introduce foreign genes into North-East rice cultivars. Therefore, the main objective of this study is to develop transformation procedures for fast recovery of transgenic plants from North-East rice cultivars. To achieve this objective, a systematic study was carried out to identify media components and culture conditions for efficient embryogenic callus induction from the mature seeds and differentiation of callus into plantlets from two North-East deep water rice cultivars, Taothabi and Khongan. Also, role of preculture of callus on Agrobacterium-mediated transformation was studied. Co-cultivation of Agrobacterium with 1-5 days precultured callus was found to result in high frequency of transformation. Detailed characterization of transgenic lines confirmed stable integration of transgenes and expression of reporter gfp gene. The whole process starting from callus induction to regenerating of transgenic rice plants that can be established in the soil was achieved in about 35-45 days. The procedures developed were found to be applicable to a popular variety IR 64. Therefore, methods developed in this study should be useful not only to introduce new traits quickly but also to validate the function(s) of several candidate gene(s) identified under the functional genomics of rice.

  4. Self-Damping Sprung Wheel

    NASA Technical Reports Server (NTRS)

    Weddendorf, Bruce

    1993-01-01

    Self-damping sprung wheel provides shock-absorbing suspension for wheelchair, reducing user's discomfort when traversing rough terrain or obstacles. Pair of self-damping sprung wheels installed in place of conventional large rear wheels of standard wheelchair, which user operates in conventional manner. Rim deflects in vicinity of contact with ground or floor. Includes inner and outer hoops bending when obstacle encountered. Shear deformation of elastomeric hoop between them absorbs energy. Thus, three hoops act together as damping spring. Alternative version of wheel designed for bicycle.

  5. Bearing-Cartridge Damping Seal

    NASA Technical Reports Server (NTRS)

    Goggins, David G.; Scharrer, Joseph K.; Chen, Wei C.

    1991-01-01

    In proposed design for improved ball-bearing cartridge, damping seal in form of thin-layer fluid journal bearing incorporated into cartridge. Damping seal acts as auxiliary bearing, relieving bearing balls of significant portions of both static and dynamic bearing loads. Damping from seal reduces dynamic loads even further by reducing amplitude of vibrations in second vibrational mode of rotor, which mode occurs when rotor turning at nearly full operating speed. Intended for use in high-pressure-oxygen turbopump of Space Shuttle main engine, also applicable to other turbomachinery bearings.

  6. Self-Damping Sprung Wheel

    NASA Technical Reports Server (NTRS)

    Weddendorf, Bruce

    1993-01-01

    Self-damping sprung wheel provides shock-absorbing suspension for wheelchair, reducing user's discomfort when traversing rough terrain or obstacles. Pair of self-damping sprung wheels installed in place of conventional large rear wheels of standard wheelchair, which user operates in conventional manner. Rim deflects in vicinity of contact with ground or floor. Includes inner and outer hoops bending when obstacle encountered. Shear deformation of elastomeric hoop between them absorbs energy. Thus, three hoops act together as damping spring. Alternative version of wheel designed for bicycle.

  7. Active Constrained Layer Damping of Thin Cylindrical Shells

    NASA Astrophysics Data System (ADS)

    RAY, M. C.; OH, J.; BAZ, A.

    2001-03-01

    The effectiveness of the active constrained layer damping (ACLD) treatments in enhancing the damping characteristics of thin cylindrical shells is presented. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. Experiments are performed to verify the numerical predictions. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  8. Electrorheologically damped impact system

    NASA Astrophysics Data System (ADS)

    Hardt, Lee R.

    1991-05-01

    An impact switch is described having a housing containing a rigid coaxial conductor entering one end. An inner cylindrical contact extends axially inward from and beyond the in housing end of an outer tubular contact which has a spiral spring extending axially from within a recess therein. The free end of the spring supports a mass spaced from the end of the inner contact. The contacts, spring and mass are enclosed within a flexible shroud spaced from the inner wall of the housing. The space between the shroud and housing contains an electrorheological fluid, the viscosity of which is a function of the voltage supplied by two electrodes extending through the housing and into the fluid. The voltage controlled viscosity permits control of damping of the shroud, mass, and spring movements in response to impact caused switch deceleration and control of time for switch closure and fuze delay by means of mass contact with the inner cylindrical contact, or spring contact with the outer tubular contact.

  9. Damping measurements using operational data

    SciTech Connect

    James, G.H.; Carne, T.G.; Veers, P.S.

    1991-01-01

    We have measured modal damping using strain-gauge data from an operating wind turbine. Previously, such measurements were difficult and expensive. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. We have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandia 34-meter Test Bed has been used to calculate modal damping ratios as a function of rotor rotation rate. This capability will allow more accurate fatigue life prediction and control. 16 refs., 3 figs., 2 tabs.

  10. Landau damping in space plasmas

    NASA Technical Reports Server (NTRS)

    Thorne, Richard M.; Summers, Danny

    1991-01-01

    The Landau damping of electrostatic Langmuir waves and ion-acoustic waves in a hot, isotropic, nonmagnetized, generalized Lorentzian plasma is analyzed using the modified plasma dispersion function. Numerical solutions for the real and imaginary parts of the wave frequency omega sub 0 - (i)(gamma) have been obtained as a function of the normalized wave number (k)(lambda sub D), where lambda sub D is the electron Debye length. For both particle distributions the electrostatic modes are found to be strongly damped at short wavelengths. At long wavelengths, this damping becomes less severe, but the attenuation of Langmuir waves is much stronger for a generalized Lorentzian plasma than for a Maxwellian plasma. It is concluded that Landau damping of ion-acoustic waves is only slightly affected by the presence of a high energy tail, but is strongly dependent on the ion temperature.

  11. Vibration damping method and apparatus

    DOEpatents

    Redmond, James M.; Barney, Patrick S.; Parker, Gordon G.; Smith, David A.

    1999-01-01

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof.

  12. Vibration damping method and apparatus

    DOEpatents

    Redmond, J.M.; Barney, P.S.; Parker, G.G.; Smith, D.A.

    1999-06-22

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof. 38 figs.

  13. Shape optimization of damping layers

    NASA Technical Reports Server (NTRS)

    Lin, T.-C.; Scott, R. A.

    1987-01-01

    Shape optimization of unconstrained and constrained damping layers is completed. The specific problem analyzed is a cantilever beam loaded at its tip by a harmonic force. Finite element modeling and mathematical programming techniques are used to obtain the solution. Performance measures are taken to be reduction of maximum diplacement and increase in fatigue lifetime. Results include the improvement, over the uniform treatment case, of these measures when the profile of the damping layer is optimized.

  14. Turbomachinery rotor support with damping

    NASA Technical Reports Server (NTRS)

    Vonpragenau, George L. (Inventor)

    1990-01-01

    Damping seals, damping bearings, and a support sleeve are presented for the ball bearings of a high speed rotor. The ball bearings consist of a duplex set having the outer races packaged tightly within the sleeve while the sleeve provides a gap with a support member so that the bearings may float with the sleeve. The sleeve has a web extending radially between the pair of outer races and acts in conjunction with one or more springs to apply an axial preload to the outer races. The sleeves have a series of slits which provide the sleeve with a spring-like quality so that the spring acts to center the rotor upon which the bearings are mounted during start up and shut down. A damping seal or a damping bearing may be used in conjunction with the ball bearings and supporting sleeve, the damping seal and damping bearing having rotor portions including rigid outer surfaces mounted within the bore of a stator portion having triangular shaped pockets on the surface facing the rotor. Axial gates are provided between adjacent pockets in sections of the stator permitting fluid to flow with less resistance axially relative to the flow of fluids circumferentially between the rotor and the stator.

  15. Damping Measurements of Plasma Modes

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Affolter, M.; Driscoll, C. F.

    2010-11-01

    For azimuthally symmetric plasma modes in a magnesium ion plasma, confined in a 3 Tesla Penning-Malmberg trap with a density of n ˜10^7cm-3, we measure a damping rate of 2s-1< γ< 10^4s-1 over a wide range in temperature (5 x10-6 eV< T < 5eV) and aspect ratio (0.25 < α< 25), with a wave amplitude of δn / n ˜5%. Changing the aspect ratio, α= Lp/ 2rp, of the plasma column, alters the frequency of the mode from 16 KHz to 192 KHz. The oscillatory fluid displacement is small compared to the wavelength of the mode; in contrast, the fluid velocity, δvf, can be large compared to v. The real part of the frequency satisfies a linear dispersion relation. In long thin plasmas (α> 10) these modes are Trivelpiece-Gould (TG) modes, and for smaller values of α they are Dubin spheroidal modes. However the damping appears to be non-linear; initially large waves have weaker exponential damping, which is not yet understood. Recent theoryootnotetextM.W. Anderson and T.M. O'Neil, Phys. Plasmas 14, 112110 (2007). calculates the damping of TG modes expected from viscosity due to ion-ion collisions; but the measured damping, while having a similar temperature and density dependence, is about 40 times larger than calculated. This discrepancy might be due to an external damping mechanism.

  16. Damping characterization in large structures

    NASA Technical Reports Server (NTRS)

    Eke, Fidelis O.; Eke, Estelle M.

    1991-01-01

    This research project has as its main goal the development of methods for selecting the damping characteristics of components of a large structure or multibody system, in such a way as to produce some desired system damping characteristics. The main need for such an analytical device is in the simulation of the dynamics of multibody systems consisting, at least partially, of flexible components. The reason for this need is that all existing simulation codes for multibody systems require component-by-component characterization of complex systems, whereas requirements (including damping) often appear at the overall system level. The main goal was met in large part by the development of a method that will in fact synthesize component damping matrices from a given system damping matrix. The restrictions to the method are that the desired system damping matrix must be diagonal (which is almost always the case) and that interbody connections must be by simple hinges. In addition to the technical outcome, this project contributed positively to the educational and research infrastructure of Tuskegee University - a Historically Black Institution.

  17. Damping Ring R&D at CESR-TA

    SciTech Connect

    Rubin, David L.

    2015-01-23

    Accelerators that collide high energy beams of matter and anti-matter are essential tools for the investigation of the fundamental constituents of matter, and the search for new forms of matter and energy. A “Linear Collider” is a machine that would bring high energy and very compact bunches of electrons and positrons (anti-electrons) into head-on collision. Such a machine would produce (among many other things) the newly discovered Higgs particle, enabling a detailed study of its properties. Among the most critical and challenging components of a linear collider are the damping rings that produce the very compact and intense beams of electrons and positrons that are to be accelerated into collision. Hot dilute particle beams are injected into the damping rings, where they are compressed and cooled. The size of the positron beam must be reduced more than a thousand fold in the damping ring, and this compression must be accomplished in a fraction of a second. The cold compact beams are then extracted from the damping ring and accelerated into collision at high energy. The proposed International Linear Collider (ILC), would require damping rings that routinely produce such cold, compact and intense beams. The goal of the Cornell study was a credible design for the damping rings for the ILC. Among the technical challenges of the damping rings; the development of instrumentation that can measure the properties of the very small beams in a very narrow window of time, and mitigation of the forces that can destabilize the beams and prevent adequate cooling, or worse lead to beam loss. One of the most pernicious destabilizing forces is due to the formation of clouds of electrons in the beam pipe. The electron cloud effect is a phenomenon in particle accelerators in which a high density of low energy electrons, build up inside the vacuum chamber. At the outset of the study, it was anticipated that electron cloud effects would limit the intensity of the positron ring

  18. Damping mechanisms of a pendulum

    NASA Astrophysics Data System (ADS)

    Dolfo, Gilles; Castex, Daniel; Vigué, Jacques

    2016-11-01

    In this paper, we study the damping mechanisms of a pendulum. The originality of our setup is the use of a metal strip suspension and the development of extremely sensitive electric measurements of the pendulum velocity and position. Their sensitivity is absolutely necessary for a reliable measurement of the pendulum damping time constant because this measurement is possible only for very low oscillation amplitudes, when air friction forces quadratic in velocity have a negligible contribution to the observed damping. We have thus carefully studied damping by air friction forces, which is the dominant mechanism for large values of the Reynolds number Re but which is negligible in the Stokes regime, {Re} ∼ 1. In this last case, we have found that the dominant damping is due to internal friction in the metal strip, a universal effect called anelasticity, and, for certain frequencies, to resonant coupling to the support of the pendulum. All our measurements are well explained by theory. We believe this paper would be of interest to students in an undergraduate classical mechanics course.

  19. Damping modification factors for eastern Canada

    NASA Astrophysics Data System (ADS)

    Daneshvar, Poulad; Bouaanani, Najib

    2017-07-01

    This paper investigates damping modification factors in eastern Canada based on historical and simulated records compatible with seismic hazard in this region. Damping modification factors are characterized as a function of magnitude, distance, site condition, and damping ratio. Damping modification factors corresponding to historical and simulated ground motions on rock sites are shown to exhibit the same trends for all damping levels. In addition to period dependency of damping modification factors, we demonstrate their sensitivity to magnitude variations at longer periods. The effect of distance is shown to be less pronounced. It is also observed that soil conditions affect damping modification factors at short as well as longer periods. Period-dependent equations are proposed for practical assessment of damping modification factors corresponding to damping ratios between 1 and 40%, considering different magnitude-distance combinations and soil conditions representative of seismic hazard in eastern Canada.

  20. Increased damping of irregular resonators.

    PubMed

    Russ, S; Sapoval, B

    2002-03-01

    It is shown that fractal drums and jagged geometry resonators may be more damped than ordinary Euclidean systems. Several damping mechanisms are examined and studied by numerical calculations. The results depend on the dissipation mechanisms but globally they increase with localization, frequency, and the irregularity of the resonator. The increased dissipation is due to the uneven spatial distribution of the vibrational amplitude in two different ways. First, it is related to the partial confinement of the vibrational modes. Secondly, increased dissipation may be due to singularities in the amplitude distribution. This is the case when a few points exist where the vibration is pinned to zero inducing local logarithmic singularities. This last effect can be spectacular: a single defect can dominate the surface damping by viscous forces of a square drum.

  1. Increased damping in irregular resonators

    NASA Astrophysics Data System (ADS)

    Sapoval, Bernard; Asch, Mark; Felix, Simon; Filoche, Marcel

    2005-04-01

    The relation between shape and damping of shallow acoustical cavities has been studied numerically in the case where the dissipation occurs only on the cavity walls. It is first found that whatever the type of geometrical irregularity, many, but not all the modes are localized. It is shown that the localization mechanism is what is called weak localization. The more irregular, the smaller the quality factors are found. However this effect is very different for the non-localized and the localized modes. For non-localized modes the damping increases roughly proportionally to the cavity surface. The localized modes are even more damped. These results generalize the results already obtained both numerically and experimentally on prefractal acoustical cavities. [B. Sapoval, O. Haeberle, and S. Russ, J. Acoust. Soc. Am. 102, 2014-2019 (1997); B. Hebert, B. Sapoval, and S. Russ, ibid. 105, 1567-1576 (1999)].

  2. Landau damping of auroral hiss

    NASA Technical Reports Server (NTRS)

    Morgan, D. D.; Gurnett, D. A.; Menietti, J. D.; Winningham, J. D.; Burch, J. L.

    1994-01-01

    Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit omega/k(sub parallel) to values of 3.4 x 10(exp 4) km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, omega/k(sub parallel) is limited to values greater than 6.8 x 10(exp 4) km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that omega/k(sub parallel) corresponds to resonance energies greater than 1 keV and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities.

  3. Landau damping of auroral hiss

    NASA Technical Reports Server (NTRS)

    Morgan, D. D.; Gurnett, D. A.; Menietti, J. D.; Winningham, J. D.; Burch, J. L.

    1994-01-01

    Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit omega/k(sub parallel) to values of 3.4 x 10(exp 4) km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, omega/k(sub parallel) is limited to values greater than 6.8 x 10(exp 4) km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that omega/k(sub parallel) corresponds to resonance energies greater than 1 keV and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities.

  4. Structural damping with shape-memory alloys: one class of devices

    NASA Astrophysics Data System (ADS)

    Krumme, Robert; Hayes, Jack; Sweeney, Steve

    1995-05-01

    Passive control of the dynamic response of civil structures utilizing shape-memory alloy (SMA) damping techniques is reviewed. An important class of SMA damper -- the center- tapped (CT) device -- is described. Coverage includes: (1) characterization of damping requirements and passive damping approaches for civil structures; (2) characterization of SMA material behaviors relevant to civil structural applications; (3) overview of our SMA passive damping device technology and description of the center-tapped device operation and structure; (4) precis of an experimental program conducted to verify the CT device behavior, the detailed results of which are reported in another paper by the Earthquake Engineering Research Center; (5) review of a design study of SMA passive damping for retrofit of an extant nonductile concrete building.

  5. Active vibration damping using smart material

    NASA Astrophysics Data System (ADS)

    Baras, John S.; Yan, Zhuang

    1994-06-01

    We consider the modeling and active damping of an elastic beam using distributed actuators and sensors. The piezoelectric ceramic material (PZT) is used to build the actuator. The sensor is made of the piezoelectric polymer polyvinylidene fluoride (PVDF). These materials are glued on both sides of the beam. For the simple clamped beam, the closed loop controller has been shown to be able to extract energy from the beam. The shape of the actuator and its influence on the closed loop system performance are discussed. It is shown that it is possible to suppress the selected mode by choosing the appropriate actuator layout. It is also shown that by properly installing the sensor and determining the sensor shape we can further extract and manipulate the sensor signal for our control need.

  6. State protection under collective damping and diffusion

    NASA Astrophysics Data System (ADS)

    de Ponte, M. A.; Mizrahi, S. S.; Moussa, M. H. Y.

    2011-07-01

    In this paper we provide a recipe for state protection in a network of oscillators under collective damping and diffusion. Our strategy is to manipulate the network topology, i.e., the way the oscillators are coupled together, the strength of their couplings, and their natural frequencies, in order to create a relaxation-diffusion-free channel. This protected channel defines a decoherence-free subspace (DFS) for nonzero-temperature reservoirs. Our development also furnishes an alternative approach to build up DFSs that offers two advantages over the conventional method: it enables the derivation of all the network-protected states at once, and also reveals, through the network normal modes, the mechanism behind the emergence of these protected domains.

  7. Active vibration damping using smart material

    NASA Technical Reports Server (NTRS)

    Baras, John S.; Yan, Zhuang

    1994-01-01

    We consider the modeling and active damping of an elastic beam using distributed actuators and sensors. The piezoelectric ceramic material (PZT) is used to build the actuator. The sensor is made of the piezoelectric polymer polyvinylidene fluoride (PVDF). These materials are glued on both sides of the beam. For the simple clamped beam, the closed loop controller has been shown to be able to extract energy from the beam. The shape of the actuator and its influence on the closed loop system performance are discussed. It is shown that it is possible to suppress the selected mode by choosing the appropriate actuator layout. It is also shown that by properly installing the sensor and determining the sensor shape we can further extract and manipulate the sensor signal for our control need.

  8. 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.

  9. A damping mechanics model and a beam finite element for the free-vibration of laminated composite strips under in-plane loading

    NASA Astrophysics Data System (ADS)

    Chortis, Dimitris I.; Chrysochoidis, Nikos A.; Varelis, Dimitris S.; Saravanos, Dimitris A.

    2011-11-01

    A theoretical framework is presented for predicting the nonlinear damping and damped vibration of laminated composite strips due to large in-plane forces. Nonlinear Green-Lagrange axial strains are introduced in the governing equations of a viscoelastic composite and new nonlinear damping and stiffness matrices are formulated including initial stress effects. Building upon the nonlinear laminate mechanics, a damped beam finite element is developed. Finite element stiffness and damping matrices are synthesized and the static equilibrium is predicted using a Newton-Raphson solver. The corresponding linearized damped free-vibration response is predicted and modal frequencies and damping of the in-plane deflected strip are calculated. Numerical results quantify the nonlinear effect of in-plane loads on structural modal damping of various laminated composite strips. The modal loss-factors and natural frequencies of cross-ply Glass/Epoxy beams subject to in-plane loading are measured and correlated with numerical results.

  10. 76 FR 28789 - Draft Alert Entitled “Preventing Occupational Respiratory Disease From Dampness in Office...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-18

    ... Respiratory Disease From Dampness in Office Buildings, Schools, and Other Nonindustrial Buildings'' AGENCY: National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control and... comment. SUMMARY: The National Institute for Occupational Safety and Health (NIOSH) of the Centers for...

  11. Surfactant damping of water waves

    NASA Astrophysics Data System (ADS)

    Lapham, Gary S.; Dowling, David R.; Schultz, William W.

    1997-11-01

    The most well known and perhaps most important distinguishing characteristic of a water surface laden with surfactant is the profound increase in small-wave damping with the addition of even small amounts of surfactant material. It would seem to follow that damping increases with increasing surfactant concentration. This is undoubtedly true for some surfactants, however our experiments with a soluble surfactant show that it is possible to increase surfactant concentration and measure a decrease in damping. While the increased concentration is accompanied by a dramatic decrease in measured static surface tension, some of the capillary-wave frequency regime is less damped. Experimental measurements of the real and imaginary parts of the wave speed are compared with existing theory where at least one other physical quantity besides surface tension is needed to properly model the interface. Our on-going work with insoluble surfactants may also provide an example of this type of behavior for materials that do not readily transfer to and from the bulk water. [Supported by the Office of Naval Research

  12. Dealing with damping-off

    USDA-ARS?s Scientific Manuscript database

    Damping-off is a common disease that rots and kills both seeds and recently germinated seedlings. The disease is caused by number of different soilborne pathogens, including true fungi (Botrytis, Fusarium, and Rhizoctonia species) and oomycetes (Phytophthora and Pythium species). The seedlings of mo...

  13. Vibration Damping Circuit Card Assembly

    NASA Technical Reports Server (NTRS)

    Hunt, Ronald Allen (Inventor)

    2016-01-01

    A vibration damping circuit card assembly includes a populated circuit card having a mass M. A closed metal container is coupled to a surface of the populated circuit card at approximately a geometric center of the populated circuit card. Tungsten balls fill approximately 90% of the metal container with a collective mass of the tungsten balls being approximately (0.07) M.

  14. Red cell DAMPs and inflammation.

    PubMed

    Mendonça, Rafaela; Silveira, Angélica A A; Conran, Nicola

    2016-09-01

    Intravascular hemolysis, or the destruction of red blood cells in the circulation, can occur in numerous diseases, including the acquired hemolytic anemias, sickle cell disease and β-thalassemia, as well as during some transfusion reactions, preeclampsia and infections, such as those caused by malaria or Clostridium perfringens. Hemolysis results in the release of large quantities of red cell damage-associated molecular patterns (DAMPs) into the circulation, which, if not neutralized by innate protective mechanisms, have the potential to activate multiple inflammatory pathways. One of the major red cell DAMPs, heme, is able to activate converging inflammatory pathways, such as toll-like receptor signaling, neutrophil extracellular trap formation and inflammasome formation, suggesting that this DAMP both activates and amplifies inflammation. Other potent DAMPs that may be released by the erythrocytes upon their rupture include heat shock proteins (Hsp), such as Hsp70, interleukin-33 and Adenosine 5' triphosphate. As such, hemolysis represents a major inflammatory mechanism that potentially contributes to the clinical manifestations that have been associated with the hemolytic diseases, such as pulmonary hypertension and leg ulcers, and likely plays a role in specific complications of sickle cell disease such as endothelial activation, vaso-occlusive processes and tissue injury.

  15. Flexible ring baffles for damping liquid slosh

    NASA Technical Reports Server (NTRS)

    Brooks, G. W.; Stephens, D. G.

    1968-01-01

    Slosh damping, obtained through the use of small, less massive, flexible baffles, provides a relatively lightweight system for damping the motions of liquid propellants in launch vehicles, missiles, and other tankage systems.

  16. Damped Oscillator with Delta-Kicked Frequency

    NASA Technical Reports Server (NTRS)

    Manko, O. V.

    1996-01-01

    Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.

  17. Next generation HOM-damping

    NASA Astrophysics Data System (ADS)

    Marhauser, Frank

    2017-06-01

    Research and development for superconducting radio-frequency cavities has made enormous progress over the last decades from the understanding of theoretical limitations to the industrial mass fabrication of cavities for large-scale particle accelerators. Key technologies remain hot topics due to continuously growing demands on cavity performance, particularly when in pursuit of high quality beams at higher beam currents or higher luminosities than currently achievable. This relates to higher order mode (HOM) damping requirements. Meeting the desired beam properties implies avoiding coupled multi-bunch or beam break-up instabilities depending on the machine and beam parameters that will set the acceptable cavity impedance thresholds. The use of cavity HOM-dampers is crucial to absorb the wakefields, comprised by all beam-induced cavity Eigenmodes, to beam-dynamically safe levels and to reduce the heat load at cryogenic temperature. Cavity damping concepts may vary, but are principally based on coaxial and waveguide couplers as well as beam line absorbers or any combination. Next generation energy recovery linacs and circular colliders call for cavities with strong HOM-damping that can exceed the state-of-the-art, while the operating mode efficiency shall not be significantly compromised concurrently. This imposes major challenges given the rather limited damping concepts. A detailed survey of established cavities is provided scrutinizing the achieved damping performance, shortcomings, and potential improvements. The scaling of the highest passband mode impedances is numerically evaluated in dependence on the number of cells for a single-cell up to a nine-cell cavity, which reveals the increased probability of trapped modes. This is followed by simulations for single-cell and five-cell cavities, which incorporate multiple damping schemes to assess the most efficient concepts. The usage and viability of on-cell dampers is elucidated for the single-cell cavity since it

  18. Next generation HOM-damping

    DOE PAGES

    Marhauser, Frank

    2017-05-15

    Research and development for superconducting radio-frequency cavities has made enormous progress over the last decades from the understanding of theoretical limitations to the industrial mass fabrication of cavities for large-scale particle accelerators. Key technologies remain hot topics due to continuously growing demands on cavity performance, particularly when in pursuit of high quality beams at higher beam currents or higher luminosities than currently achievable. This relates to Higher Order Mode (HOM) damping requirements. Meeting the desired beam properties implies avoiding coupled multi-bunch or beam break-up instabilities depending on the machine and beam parameters that will set the acceptable cavity impedance thresholds.more » The use of cavity HOM-dampers is crucial to absorb the wakefields, comprised by all beam-induced cavity Eigenmodes, to beam-dynamically safe levels and to reduce the heat load at cryogenic temperature. Cavity damping concepts may vary, but are principally based on coaxial and waveguide couplers as well as beam line absorbers or any combination. Next generation Energy Recovery Linacs and circular colliders call for cavities with strong HOM-damping that can exceed the state-of-the-art, while the operating mode efficiency shall not be significantly compromised concurrently. This imposes major challenges given the rather limited damping concepts. A detailed survey of established cavities is provided scrutinizing the achieved damping performance, shortcomings, and potential improvements. The scaling of the highest passband mode impedances is numerically evaluated in dependence on the number of cells for a single-cell up to a nine-cell cavity, which reveals the increased probability of trapped modes. This is followed by simulations for single-cell and five-cell cavities, which incorporate multiple damping schemes to assess the most efficient concepts. The usage and viability of on-cell dampers is elucidated for the single-cell cavity

  19. Mechanical testing of high-damping elastomer materials for determining design parameters of seismic isolation bearings

    SciTech Connect

    Hughes, T.H.; Kulak, R.F.

    1994-06-01

    High-damping steel-laminated elastomeric bearings are one of the devices used for isolating large buildings and structures from earthquake damage. These load-bearing isolators are constructed from alternating layers of high-damping rubber and steel plates. In this paper the mechanical testing of small specimens of some elastomer compounds proposed for the isolation of advanced nuclear reactors is discussed. Variation of shear stiffness and damping with respect to shear strain level (5 % to 300 %), temperature ({minus}40{degrees}C to +50{degrees}C) and frequency (0.002Hz to 5Hz) are reported. Problems involved in obtaining reliable and repeatable results are also discussed.

  20. Building with Sand

    ERIC Educational Resources Information Center

    Ashbrook, Peggy

    2010-01-01

    Children playing in damp sand invariably try to make a tower or a tunnel. By providing experiences with a variety of materials, alone and together, teachers set up the conditions for children to learn through their senses and ensure that a class approaches a topic with a common set of experiences to build on. Learning about the properties of…

  1. Building with Sand

    ERIC Educational Resources Information Center

    Ashbrook, Peggy

    2010-01-01

    Children playing in damp sand invariably try to make a tower or a tunnel. By providing experiences with a variety of materials, alone and together, teachers set up the conditions for children to learn through their senses and ensure that a class approaches a topic with a common set of experiences to build on. Learning about the properties of…

  2. Squeezed states of damped oscillator chain

    NASA Technical Reports Server (NTRS)

    Manko, O. V.

    1993-01-01

    The Caldirola-Kanai model of one-dimensional damped oscillator is extended to the chain of coupled parametric oscillators with damping. The correlated and squeezed states for the chain of coupled parametric oscillators with damping are constructed. Based on the concept of the integrals of motion, it is demonstrated how squeezing phenomenon arises due to parametric excitation.

  3. Recommendation for the Feasibility of more Compact LC Damping Rings

    SciTech Connect

    Pivi, M.T.F.; Wang, L.; Demma, T.; Guiducci, S.; Suetsugu, Y.; Shibata, K.; Ohmi, K.; Dugan, G.; Palmer, M.; Crittenden, J.A.; Harkay, K.; Boon, L.; Furman, M.A.; Venturini, M.; Celata, C.; Malyshev, O.B.; Papaphilippou, I.; /CERN

    2010-06-15

    As part of the international Linear Collider (ILC) collaboration, we have compared the electron cloud (EC) effect for different Damping Ring (DR) designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of the shorter damping ring with respect to the electron cloud build-up and related beam instabilities. The studies for a 3.2 km ring were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design SB2009 [1] and would allow considerable reduction of the number of components, wiggler magnets and costs. We discuss the impact of the proposed operation of the ILC at high repetition rate 10 Hz and address the necessary modifications for the DRs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigation techniques and the integration of the CesrTA results into the Damping Ring design.

  4. Recommendation for the Feasibility of more Compact LC Damping Rings

    SciTech Connect

    Pivi, M. T. F.; Wang, L.; Demma, T.; Guiducci, S.; Suetsugu, Y.; Fukuma, H.; Shibata, K.; Dugan, K.,G.; Palmer, M.; Crittenden, J.; Harkay, K.; Boon, L.; Furman, M. A.; Venturini, M.; Celata, C.; Malyshev, O.; Papaphilippou, I.

    2010-05-23

    As part of the international Linear Collider (ILC) collaboration, we have compared the electron cloud (EC) effect for different Damping Ring (DR) designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. The studies for a 3.2 km ring were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design SB2009 [1] and would allow to considerably reduce the number of components, wiggler magnets and costs. We discuss the impact of the proposed operation of the ILC at high repetition rate 10 Hz and address the necessary modifications for the DRs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design.

  5. Vibration control of cylindrical shells using active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Ray, Manas C.; Chen, Tung-Huei; Baz, Amr M.

    1997-05-01

    The fundamentals of controlling the structural vibration of cylindrical shells treated with active constrained layer damping (ACLD) treatments are presented. The effectiveness of the ACLD treatments in enhancing the damping characteristics of thin cylindrical shells is demonstrated theoretically and experimentally. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. The FEM is used to predict the natural frequencies and the modal loss factors of shells which are partially treated with patches of the ACLD treatments. The predictions of the FEM are validated experimentally using stainless steel cylinders which are 20.32 cm in diameter, 30.4 cm in length and 0.05 cm in thickness. The cylinders are treated with ACLD patches of different configurations in order to target single or multi-modes of lobar vibrations. The ACLD patches used are made of DYAD 606 visco-elastic layer which is sandwiched between two layers of PVDF piezo-electric films. Vibration attenuations of 85% are obtained with maximum control voltage of 40 volts. Such attenuations are attributed to the effectiveness of the ACLD treatment in increasing the modal damping ratios by about a factor of four over those of conventional passive constrained layer damping (PCLD) treatments. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  6. Frequency and temperature dependence of high damping elastomers

    SciTech Connect

    Kulak, R.F.; Hughes, T.H.

    1993-08-01

    High damping steel-laminated elastomeric seismic isolation bearings are one of the preferred devices for isolating large buildings and structures. In the US, the current reference design for the Advanced Liquid Metal Reactor (ALMR) uses laminated bearings for seismic isolation. These bearings are constructed from alternating layers of high damping rubber and steel plates. They are typically designed for shear strains between 50 and 100% and are expected to sustain two to three times these levels for beyond design basis loading conditions. Elastomeric bearings are currently designed to provide a system frequency between 0.4 and 0.8 Hz and expected to operate between {minus}20 and 40 degrees Centigrade. To assure proper performance of isolation bearings, it is necessary to characterize the elastomer`s response under expected variations of frequency and temperature. The dynamic response of the elastomer must be characterized within the frequency range that spans the bearing acceptance test frequency, which may be as low as 0.005 Hz, and the design frequency. Similarly, the variation in mechanical characteristics of the elastomer must be determined over the design temperature range, which is between {minus}20 and 40 degrees Centigrade. This paper reports on (1) the capabilities of a testing facility at ANL for testing candidate elastomers, (2) the variation with frequency and temperature of the stiffness and damping of one candidate elastomer, and (3) the effect of these variations on bearing acceptance testing criteria and on the choice of bearing design values for stiffness and damping.

  7. Optimum Damping in a Non-Linear Base Isolation System

    NASA Astrophysics Data System (ADS)

    Jangid, R. S.

    1996-02-01

    Optimum isolation damping for minimum acceleration of a base-isolated structure subjected to earthquake ground excitation is investigated. The stochastic model of the El-Centro1940 earthquake, which preserves the non-stationary evolution of amplitude and frequency content of ground motion, is used as an earthquake excitation. The base isolated structure consists of a linear flexible shear type multi-storey building supported on a base isolation system. The resilient-friction base isolator (R-FBI) is considered as an isolation system. The non-stationary stochastic response of the system is obtained by the time dependent equivalent linearization technique as the force-deformation of the R-FBI system is non-linear. The optimum damping of the R-FBI system is obtained under important parametric variations; i.e., the coefficient of friction of the R-FBI system, the period and damping of the superstructure; the effective period of base isolation. The criterion selected for optimality is the minimization of the top floor root mean square (r.m.s.) acceleration. It is shown that the above parameters have significant effects on optimum isolation damping.

  8. Mold exposure and respiratory health in damp indoor environments.

    PubMed

    Park, Ju-Hyeong; Cox-Ganser, Jean M

    2011-01-01

    Almost all modern buildings experience at least minor, and sometimes serious, water damage during their life span. Excess moisture in buildings becomes a critical factor for mold (fungal) proliferation in nutrient-rich environments. As a result, building occupants may be exposed to increased levels of microbial agents such as fungal spores, cell fragments, cell wall components, or toxins. Such exposures may result in various diseases and symptoms, both respiratory and non-respiratory. Respiratory health complaints are common in damp buildings and have been more thoroughly studied than non-respiratory complaints. Respiratory diseases and symptoms which may be produced by exposure to indoor fungi include asthma development, exacerbation of asthma, hypersensitivity pneumonitis, cough, wheeze, dyspnea (shortness of breath), nasal and throat symptoms, and respiratory infections. In addition to these illnesses, rhinosinusitis and sarcoidosis in water-damaged building occupants are also drawing more scientific attention. In this article, we explore the evidence for adverse effects of fungal exposure on respiratory health in damp indoor environments and potential disease mechanisms related to the exposure.

  9. DAMPs, Ageing, and Cancer: The ‘DAMP Hypothesis’

    PubMed Central

    Huang, Jin; Xie, Yangchun; Sun, Xiaofang; Zeh, Herbert J.; Kang, Rui; Lotze, Michael T.; Tang, Daolin

    2014-01-01

    Ageing is a complex and multifactorial process characterized by the accumulation of many forms of damage at the molecular, cellular, and tissue level with advancing age. Ageing increases the risk of the onset of chronic inflammation-associated diseases such as cancer, diabetes, stroke, and neurodegenerative disease. In particular, ageing and cancer share some common origins and hallmarks such as genomic instability, epigenetic alteration, aberrant telomeres, inflammation and immune injury, reprogrammed metabolism, and degradation system impairment (including within the ubiquitin-proteasome system and the autophagic machinery). Recent advances indicate that damage-associated molecular pattern molecules (DAMPs) such as high mobility group box 1, histones, S100, and heat shock proteins play location-dependent roles inside and outside the cell. These provide interaction platforms at molecular levels linked to common hallmarks of ageing and cancer. They can act as inducers, sensors, and mediators of stress through individual plasma membrane receptors, intracellular recognition receptors (e.g., advanced glycosylation end product-specific receptors, AIM2-like receptors, RIG-I-like receptors, and NOD1-like receptors, and toll-like receptors), or following endocytic uptake. Thus, the DAMP Hypothesis is novel and complements other theories that explain the features of ageing. DAMPs represent ideal biomarkers of ageing and provide an attractive target for interventions in ageing and age-associated diseases. PMID:25446804

  10. Cocured damped layers in composite structure

    SciTech Connect

    Rotz, C.A. ); Barrett, D.J. )

    1992-01-01

    A study was made on the feasibility of laminating and cocuring graphite fiber-epoxy prepreg with plies of commercially available damping materials for form beams and hat-stiffened panels. Experiments showed that cocuring did not adversely affect the damping materials and that excellent structural damping properties could be obtained. The construction of the hat-stiffened panels proved that complex parts containing damping materials could be fabricated. Dynamic testing of these components showed that internal architectural features could be designed to promote damping in primary structure.

  11. Clipped viscous damping with negative stiffness for semi-active cable damping

    NASA Astrophysics Data System (ADS)

    Weber, F.; Boston, C.

    2011-04-01

    This paper investigates numerically and experimentally clipped viscous damping with negative stiffness for semi-active cable damping. From simulations it is concluded that unclipped and clipped viscous damping with negative stiffness is equivalent to unclipped and clipped LQR. It is shown that optimized unclipped viscous damping with negative stiffness generates critical cable damping by an anti-node at the actuator position. The resulting curvature at the actuator position is larger than the curvature close to the anchors due to the disturbance forces which may lead to premature cable fatigue at the actuator position. Optimized clipped viscous damping with negative stiffness does not show this drawback, can be implemented using a semi-active damper and produces twice as much cable damping as optimal viscous damping. Close to the optimal tuning, it leads to approximately the same control force as optimal semi-active friction damping with negative stiffness, which explains the superior cable damping. The superior damping results from the negative stiffness that increases the damper motion. Clipped viscous damping with negative stiffness is validated on a strand cable with a magneto-rheological damper. The measured cable damping is twice that achieved by emulated viscous damping, which confirms the numerical results. A tuning rule for clipped viscous damping with negative stiffness of real cables with flexural rigidity is given.

  12. Route Flap Damping Made Usable

    NASA Astrophysics Data System (ADS)

    Pelsser, Cristel; Maennel, Olaf; Mohapatra, Pradosh; Bush, Randy; Patel, Keyur

    The Border Gateway Protocol (BGP), the de facto inter-domain routing protocol of the Internet, is known to be noisy. The protocol has two main mechanisms to ameliorate this, MinRouteAdvertisementInterval (MRAI), and Route Flap Damping (RFD). MRAI deals with very short bursts on the order of a few to 30 seconds. RFD deals with longer bursts, minutes to hours. Unfortunately, RFD was found to severely penalize sites for being well-connected because topological richness amplifies the number of update messages exchanged. So most operators have disabled it. Through measurement, this paper explores the avenue of absolutely minimal change to code, and shows that a few RFD algorithmic constants and limits can be trivially modified, with the result being damping a non-trivial amount of long term churn without penalizing well-behaved prefixes' normal convergence process.

  13. Evaluation of SDRC Damping Analysis.

    DTIC Science & Technology

    1980-01-01

    Appendix C - Mechanical Analysis Dita Appendix D - Basic Program plus results Appendix E - American Bureau of Shipping Letter Appendix F - Power ...SEWC supplied a table of estimated roots and an associated damping power spectra. The tables of modal parameters and the data plots are connected by...appropriate table and plot. Appendix F provides a complete listing of all daping power spectras submitted by 51110. 2 Figure 6 (a,b,c) shows a plot of

  14. Nonlinear damping identification from transient data

    NASA Astrophysics Data System (ADS)

    Smith, Clifford B.; Wereley, Norman M.

    1999-06-01

    To study new damping augmentation methods for helicopter rotor systems, accurate and reliable nonlinear damping identification techniques are needed. For example, current studies on applications of magnetorheological (MR) dampers for rotor stability augmentation suggest that a strong Coulomb damping characteristic will be manifested as the field applied to the MR fluid is maximized. Therefore, in this work, a single degree of freedom (SDOF) system having either nonlinear Coulomb or quadratic damping is considered. This paper evaluates three analyses for identifying damping from transient test data; an FFT-based moving block analysis, an analysis based on a periodic Fourier series decomposition, and a Hilbert transform based technique. Analytical studies are used to determine the effects of block length, noise, and error in identified modal frequency on the accuracy of the identified damping level. The FFT-based moving block has unacceptable performance for systems with nonlinear damping. These problems were remedied in the Fourier series based analysis and acceptable performance is obtained for nonlinear damping identification from both this technique and the Hilbert transform based method. To more closely simulate a helicopter rotor system test, these techniques were then applied to a signal composed of two closely spaced modes. This data was developed to simulate a response containing the first lag and 1/rev modes. The primary mode of interest (simulated lag mode) had either Coulomb or quadratic damping, and the close mode (1/rev) was either undamped or had a specified viscous damping level. A comprehensive evaluation of the effects of close mode amplitude, frequency, and damping level was performed. A classifier was also developed to identify the dominant damping mechanism in a signal of 'unknown' composition. This classifier is based on the LMS error of a fit of the analytical envelope expression to the experimentally identified envelope signal. In most

  15. ICAN/DAMP-integrated composite analyzer with damping analysis capabilities: User's manual

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitrious A.; Sanfeliz, Jose G.

    1992-01-01

    This manual describes the use of the computer code ICAN/DAMP (Integrated Composite Analyzer with Damping Analysis Capabilities) for the prediction of damping in polymer-matrix composites. The code is written in FORTRAN 77 and is a version of the ICAN (Integrated Composite ANalyzer) computer program. The code incorporates a new module for synthesizing the material damping from micromechanics to laminate level. Explicit micromechanics equations based on hysteretic damping are programmed relating the on-axis damping capacities to the fiber and matrix properties and fiber volume ratio. The damping capacities of unidirectional composites subjected to off-axis loading are synthesized from on-axis damping values. The hygrothermal effect on the damping performance of unidirectional composites caused by temperature and moisture variation is modeled along with the damping contributions from interfacial friction between broken fibers and matrix. The temperature rise is continuously vibrating composite plies and composite laminates is also estimated. The ICAN/DAMP user's manual provides descriptions of the damping analysis module's functions, structure, input requirements, output interpretation, and execution requirements. It only addresses the changes required to conduct the damping analysis and is used in conjunction with the 'Second Generation Integrated Composite Analyzer (ICAN) Computer Code' user's manual (NASA TP-3290).

  16. Introduction to DAMPE event reconstruction (On behalf of DAMPE collaboration)

    NASA Astrophysics Data System (ADS)

    Zang, Jingjing

    2016-07-01

    The Dark Matter Particle Explorer (DAMPE) is a high energy particle physics experiment satellite, launched on 17 Dec 2015. To measure basic attributes of cosmic ray particles, DAMPE is equipped with four sub-detectors, BGO calorimeter (BGO), plastic scintillator detector (PSD), silicon tungsten tracker (STK) and neutron detector (NUD). On orbit, the high energy particle data are acquired and recorded by well-designed Data Acquisition system. After that, a series of elaborate event reconstruction algorithms are implemented to determine the energy, direction and particle ID of each event. The energy reconstruction algorithm firstly treats the sum of the BGO crystal energy as the overall energy estimator and various corrections are performed to calculate energy leakage from side and back of the calorimeter. The track reconstruction starts with cluster finding in STK, then shower axis of BGO and barycentre of clusters are used to extract seed of tracks. These seeds will be projected on the next layer by Kalman Filter method which will finally give location and direction of particle tracks. Based on shower development in BGO and tracks reconstructed by STK, we also combine data from PSD and NUD and developed a series of algorithms to evaluate particle's charge and identification. In this talk, we will describe technical strategies of event reconstruction and provide their basic performance.

  17. Damped transverse oscillations of interacting coronal loops

    NASA Astrophysics Data System (ADS)

    Soler, Roberto; Luna, Manuel

    2015-10-01

    Damped transverse oscillations of magnetic loops are routinely observed in the solar corona. This phenomenon is interpreted as standing kink magnetohydrodynamic waves, which are damped by resonant absorption owing to plasma inhomogeneity across the magnetic field. The periods and damping times of these oscillations can be used to probe the physical conditions of the coronal medium. Some observations suggest that interaction between neighboring oscillating loops in an active region may be important and can modify the properties of the oscillations. Here we theoretically investigate resonantly damped transverse oscillations of interacting nonuniform coronal loops. We provide a semi-analytic method, based on the T-matrix theory of scattering, to compute the frequencies and damping rates of collective oscillations of an arbitrary configuration of parallel cylindrical loops. The effect of resonant damping is included in the T-matrix scheme in the thin boundary approximation. Analytic and numerical results in the specific case of two interacting loops are given as an application.

  18. Critically stable damping in flexible structure control

    NASA Astrophysics Data System (ADS)

    Xing, Zhigang; Zheng, Gangtie

    2017-10-01

    The concept of critically stable damping and its application to flexible structure control are presented. Critically stable damping was originally noted from the viewpoint of control-structure integration. It was recognized that a slight augmentation of structural damping would result in substantially more robust control without decreased performance and could guarantee the stability margin for any structural frequency increase. This paper illustrates the wide occurrence of critically stable damping phenomenon, establishes its basic relationship for the insight of the general design procedure, and applies the concept into the practical design of a satellite with a large deployable antenna. It is noted that the critically stable damping concept could provide a feasible approach to overcome the difficulty in ultra-large space structure design and control, and enhance the performance of a variety of excellent control design methodologies for flexible structure control. This critically stable damping provides new insight into the integrated design of control and structure.

  19. Vitreous Enamel Damping Material Development.

    DTIC Science & Technology

    1982-11-01

    PROCEDURES 3 2.1. EXPERIMENTAL 3 2.1.1. GLASS PREPARATION 3 2.1.2. METHOD OF COATING APPLICATION 3 2.1.3. VIBRATION DAMPING MEASUREMENTS 3 2.2. CALCULATION OF...discussion in this report. fL 2 SECTION II TECHNICAL PROCEDURES 2.1 EXPERIMENTAL 2.1.1 Glass Preparation All of the compositions, except the standard...After heat treatments of composition "B", a- cristobalite and devitrite (Na20.3CaO-6SiO 2) appear as crystalline phases; a- cristobalite being the major

  20. Slip Damping of Turbine Blades.

    DTIC Science & Technology

    1978-12-01

    between stress and energy dissipated of the form N D = J0 (73) B - j was assumed. J and N are empirically derived constants and a is the B bending...November 1977. 12. Klumpp, James H., and Benjamin J . Lazan . Frictional Damping and Resonant Vibration Characteristics of an Axial Slip Lap Joint. WADC...GAE/AA/78D-1 I 4-80OI *mmmmmmih. 00 DTIC ELECTEK ~OF 4 MAR 18 US0 B ,C) UNITED STATES AIR FORCE AIR UNIVERSITY ;* AIR FORCE INSTITUTE OF TECHNOLOGY

  1. The intrinsic damping of the fractional oscillator

    NASA Astrophysics Data System (ADS)

    Tofighi, Ali

    2003-11-01

    We obtain analytical expressions for the time rate of change of the potential energy, the kinetic energy and the total energy of a fractional oscillator in terms of the products of Mittag-Leffler functions. We propose a definition for the intrinsic damping force of this oscillator. We obtain a general expression for this damping force. An expression for this damping force in the asymptotic limit ( ωt→0) is also obtained.

  2. CHARACTERIZATION OF DAMPING IN BOLTED LAP JOINTS

    SciTech Connect

    C. MALONEY; D. PEAIRS; ET AL

    2000-08-01

    The dynamic response of a jointed beam was measured in laboratory experiments. The data were analyzed and the system was mathematically modeled to establish plausible representations of joint damping behavior. Damping is examined in an approximate, local linear framework using log decrement and half power bandwidth approaches. in addition, damping is modeled in a nonlinear framework using a hybrid surface irregularities model that employs a bristles-construct. Experimental and analytical results are presented.

  3. Viscous damped space structure for reduced jitter

    NASA Technical Reports Server (NTRS)

    Wilson, James F.; Davis, L. Porter

    1987-01-01

    A technique to provide modal vibration damping in high performance space structures was developed which uses less than one once of incompressible fluid. Up to 50 percent damping can be achieved which can reduce the settling times of the lowest structural mode by as much as 50 to 1. This concept allows the designers to reduce the weight of the structure while improving its dynamic performance. Damping by this technique is purely viscous and has been shown by test to be linear over 5 orders of input magnitude. Amplitudes as low as 0.2 microinch were demonstrated. Damping in the system is independent of stiffness and relatively insensitive to temperature.

  4. Damping constant estimation in magnetoresistive readers

    SciTech Connect

    Stankiewicz, Andrzej Hernandez, Stephanie

    2015-05-07

    The damping constant is a key design parameter in magnetic reader design. Its value can be derived from bulk or sheet film ferromagnetic resonance (FMR) line width. However, dynamics of nanodevices is usually defined by presence of non-uniform modes. It triggers new damping mechanisms and produces stronger damping than expected from traditional FMR. This work proposes a device-level technique for damping evaluation, based on time-domain analysis of thermally excited stochastic oscillations. The signal is collected using a high bandwidth oscilloscope, by direct probing of a biased reader. Recorded waveforms may contain different noise signals, but free layer FMR is usually a dominating one. The autocorrelation function is a reflection of the damped oscillation curve, averaging out stochastic contributions. The damped oscillator formula is fitted to autocorrelation data, producing resonance frequency and damping constant values. Restricting lag range allows for mitigation of the impact of other phenomena (e.g., reader instability) on the damping constant. For a micromagnetically modeled reader, the technique proves to be much more accurate than the stochastic FMR line width approach. Application to actual reader waveforms yields a damping constant of ∼0.03.

  5. Hysteretic damping in rotordynamics: An equivalent formulation

    NASA Astrophysics Data System (ADS)

    Genta, Giancarlo; Amati, Nicola

    2010-10-01

    The hysteretic damping model cannot be applied to time domain dynamic simulations: this is a well-known feature that has been discussed in the literature since the time when analog computers were widespread. The constant equivalent damping often introduced to overcome this problem is also discussed, and its limitations are stated, in particular those linked with its application in rotordynamics to simulate rotating damping. An alternative model based on the nonviscous damping (NVD) model, but with a limited number of additional degrees of freedom, is proposed, and the relevant equations are derived. Some examples show applications to the rotordynamics field.

  6. Material Damping Experiments at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Levine, Marie; White, Christopher

    2003-01-01

    A unique experimental facility has been designed to measure damping of materials at cryogenic temperatures. The test facility pays special attention to removing other sources of damping in the measurement by avoiding frictional interfaces, decoupling the test specimen from the support system, and by using a non-contacting measurement device; Damping data is obtained for materials (AI, GrEp, Be, Fused Quartz), strain amplitudes (less than 10-6 ppm), frequencies (20Hz-330Hz) and temperatures (20K-293K) relevant to future precision optical space missions. The test data shows a significant decrease in viscous damping at cryogenic temperatures and can be as low as 10-4%, but the amount of the damping decrease is a function of frequency and material. Contrary to the other materials whose damping monotonically decreased with temperature, damping of Fused Quartz increased substantially at cryo, after reaching a minimum at around l50 K. The damping is also shown to be insensitive to strain for low strain levels. At room temperatures, the test data correlates well to the analytical predictions of the Zener damping model. Discrepancies at cryogenic temperatures between the model predictions and the test data are observed.

  7. A Novel Damping Mechanism for Diocotron Modes

    NASA Astrophysics Data System (ADS)

    Chim, Chi Yung; O'Neil, Thomas M.

    2014-10-01

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 1 and m = 2 diocotron modes. Transport due to small field asymmetries produces a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius, where f = mfE × B (r) . The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This poster explains with analytic theory and simulations the new algebraic damping due to both mobility and diffusive fluxes. The damping is due to transfer of canonical angular momentum from the mode to halo particles, as they are swept around the ``cat's eye'' orbits of resonant wave-particle interaction. Another picture is that the electrons in the resonant layer form a dipole (m = 1) or quadrupole (m = 2) density distribution, and the electric field for this distribution produces E × B drifts that symmetrizes the core and damps the mode. Supported by NSF/DOE Partnership Grants PHY-0903877 and DE-SC0002451.

  8. Superconductive material and magnetic field for damping and levitation support and damping of cryogenic instruments

    NASA Technical Reports Server (NTRS)

    Dolgin, Benjamin P. (Inventor)

    1994-01-01

    A superconductive load bearing support without a mechanical contact and vibration damping for cryogenic instruments in space is presented. The levitation support and vibration damping is accomplished by the use of superconducting magnets and the 'Meissner' effect. The assembly allows for transfer of vibration energy away from the cryogenic instrument which then can be damped by the use of either an electronic circuit or conventional vibration damping mean.

  9. Acoustic transducer with damping means

    DOEpatents

    Smith, Richard W.; Adamson, Gerald E.

    1976-11-02

    An ultrasonic transducer specifically suited to high temperature sodium applications is described. A piezoelectric active element is joined to the transducer faceplate by coating the faceplate and juxtaposed active element face with wetting agents specifically compatible with the bonding procedure employed to achieve the joint. The opposite face of the active element is fitted with a backing member designed to assure continued electrical continuity during adverse operating conditions which can result in the fracturing of the active element. The fit is achieved employing a spring-loaded electrode operably arranged to electrically couple the internal transducer components, enclosed in a hermetically sealed housing, to accessory components normally employed in transducer applications. Two alternative backing members are taught for assuring electrical continuity. The first employs a resilient, discrete multipoint contact electrode in electrical communication with the active element face. The second employs a resilient, elastomeric, electrically conductive, damped member in electrical communication with the active element face in a manner to effect ring-down of the transducer. Each embodiment provides continued electrical continuity within the transducer in the event the active element fractures, while the second provides the added benefit of damping.

  10. Relaxation damping in oscillating contacts

    PubMed Central

    Popov, M.; Popov, V.L.; Pohrt, R.

    2015-01-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed. PMID:26549011

  11. Damped Lyman-α Systems

    NASA Astrophysics Data System (ADS)

    Petitjean, P.; Ledoux, C.

    Recently, Prochaska & Wolfe (1997) have used Keck spectra of 17 DLA absorbers to investigate the kinematics of the neutral gas using unsaturated low excitation transitions such as Si iiλ 1808. They show that the absorption profiles are inconsistent with models of galactic haloes with random motions, spherically infalling gas and slowly rotating hot disks. The CDM model (Kauffmann 1996) is rejected as it produces disks with rotation velocities too small to account for the large observed velocity broadening of the absorption lines. Models of thick disks (h ~0.3 R, where h is the vertical scale and R the radius) with large rotational velocity (v 225kms-1) can reproduce the data. By combining new data on five damped systems with information gathered in the literature, we study the kinematics of the low and high-ionization phases in a sample of 26 damped Lyman-α systems in the redshift range 1.17 - 4.38. We show that the broader the line the more asymmetric, as expected in case rotation dominates the line broadening. However this correlation does not hold for velocities larger than 150 km/s indicating that evidence for rotational motions if any is restricted to velocity broadenings Δ V < 150kms-1. The systems with Δ V > 200kms-1 are peculiar with kinematics consistent with random motions. They show sub-systems as those expected if the objects are in the process of merging.

  12. Tuned vibration absorbers with nonlinear viscous damping for damped structures under random load

    NASA Astrophysics Data System (ADS)

    Shum, K. M.

    2015-06-01

    The classical problem for the application of a tuned vibration absorber is to minimize the response of a structural system, such as displacement, velocity, acceleration or to maximize the energy dissipated by tuned vibration absorber. The development of explicit optimal absorber parameters is challenging for a damped structural system since the fixed points no longer exist in the frequency response curve. This paper aims at deriving a set of simple design formula of tuned vibration absorber with nonlinear viscous damping based on the frequency tuning for harmonic load for a damped structural system under white noise excitation. The vibration absorbers being considered include tuned mass damper (TMD) and liquid column vibration absorber (LCVA). Simple approximate expression for the standard deviation velocity response of tuned vibration absorber for damped primary structure is also derived in this study to facilitate the estimation of the damping coefficient of TMD with nonlinear viscous damping and the head loss coefficient of LCVA. The derived results indicate that the higher the structural inherent damping the smaller the supplementary damping provided by a tuned vibration absorber. Furthermore, the optimal damping of tuned vibration absorber is shown to be independent of structural damping when it is tuned using the frequency tuning for harmonic load. Finally, the derived closed-form expressions are demonstrated to be capable of predicting the optimal parameters of tuned vibration absorbers with sufficient accuracy for preliminary design of tuned vibration absorbers with nonlinear viscous damping for a damped primary structure.

  13. Quasienergy formulation of damped response theory.

    PubMed

    Kristensen, Kasper; Kauczor, Joanna; Kjaergaard, Thomas; Jørgensen, Poul

    2009-07-28

    We present a quasienergy-based formulation of damped response theory where a common effective lifetime parameter has been introduced for all excited states in terms of complex excitation energies. The introduction of finite excited state lifetimes leads to a set of (complex) damped response equations, which have the same form to all orders in the perturbation. An algorithm is presented for solving the damped response equations in Hartree-Fock theory and Kohn-Sham density functional theory. The use of the quasienergy formulation allows us to obtain directly the computationally simplest expressions for damped response functions by applying a set of response parameter elimination rules, which minimize the total number of damped response equations to be solved. In standard response theory broadened absorption spectra are obtained by ad hoc superimposing lineshape functions onto the absorption stick spectra, whereas an empirical lineshape function common to all excitations is an integrated part of damped response theory. By superimposing the lineshape functions inherent in damped response theory onto the stick spectra of standard response theory, we show that the absorption spectra obtained in standard and damped response theory calculations are identical. We demonstrate that damped response theory may be applied to obtain absorption spectra in all frequency ranges, also those that are not readily addressed using standard response theory. This makes damped response theory an effective tool, e.g., for determining absorption spectra for large molecules, where the density of the excited states may be very high, and where standard response theory therefore is not applicable in practice. A thorough comparison is given between our formulation of damped response theory and the formulation by Norman et al. [J. Chem. Phys. 123, 194103 (2005)].

  14. DAMPs from Cell Death to New Life

    PubMed Central

    Vénéreau, Emilie; Ceriotti, Chiara; Bianchi, Marco Emilio

    2015-01-01

    Our body handles tissue damage by activating the immune system in response to intracellular molecules released by injured tissues [damage-associated molecular patterns (DAMPs)], in a similar way as it detects molecular motifs conserved in pathogens (pathogen-associated molecular patterns). DAMPs are molecules that have a physiological role inside the cell, but acquire additional functions when they are exposed to the extracellular environment: they alert the body about danger, stimulate an inflammatory response, and finally promote the regeneration process. Beside their passive release by dead cells, some DAMPs can be secreted or exposed by living cells undergoing a life-threatening stress. DAMPs have been linked to inflammation and related disorders: hence, inhibition of DAMP-mediated inflammatory responses is a promising strategy to improve the clinical management of infection- and injury-elicited inflammatory diseases. However, it is important to consider that DAMPs are not only danger signals but also central players in tissue repair. Indeed, some DAMPs have been studied for their role in tissue healing after sterile or infection-associated inflammation. This review is focused on two exemplary DAMPs, HMGB1 and adenosine triphosphate, and their contribution to both inflammation and tissue repair. PMID:26347745

  15. 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.

  16. Understanding the Damped SHM without ODEs

    ERIC Educational Resources Information Center

    Ng, Chiu-king

    2016-01-01

    Instead of solving ordinary differential equations (ODEs), the damped simple harmonic motion (SHM) is surveyed qualitatively from basic mechanics and quantitatively by the instrumentality of a graph of velocity against displacement. In this way, the condition b ? [square root]4mk for the occurrence of the non-oscillating critical damping and…

  17. Bending rate damping in elastic systems

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Wang, Y.; Fabiano, R. H.

    1989-01-01

    Preliminary results of an investigation of the bending rate damping model for elastic structures are presented. A model for which the internal damping term is physically plausible and which can accomodate cantilevered boundary conditions is discussed. The model formulation and mathematical foundations are given, and numerical results are discussed.

  18. Damping device for a stationary labyrinth seal

    NASA Technical Reports Server (NTRS)

    El-Aini, Yehia M. (Inventor); Mitchell, William S. (Inventor); Roberts, Lawrence P. (Inventor); Montgomery, Stuart K. (Inventor); Davis, Gary A. (Inventor)

    2010-01-01

    A stationary labyrinth seal system includes a seal housing having an annular cavity, a plurality of damping devices, and a retaining ring. The damping devices are positioned within the annular cavity and are maintained within the annular cavity by the retaining ring.

  19. Damping-off in forest nurseries

    Treesearch

    Carl Hartley

    1921-01-01

    Damping-off is the commonest English name for a symptomatic group of diseases affecting great numbers of plant species of widely separated phylogenetic groups. It is commonly used for any disease which results in the rapid decay of young succulent seedlings or soft cuttings. Young shoots from underground rootstocks may also be damped-off before they break through the...

  20. Understanding the Damped SHM without ODEs

    ERIC Educational Resources Information Center

    Ng, Chiu-king

    2016-01-01

    Instead of solving ordinary differential equations (ODEs), the damped simple harmonic motion (SHM) is surveyed qualitatively from basic mechanics and quantitatively by the instrumentality of a graph of velocity against displacement. In this way, the condition b ? [square root]4mk for the occurrence of the non-oscillating critical damping and…

  1. Beam dynamic issues in TESLA damping ring

    SciTech Connect

    Shiltsev, V.

    1996-05-01

    In this paper we study general requirements on impedances of the linear collider TESLA damping ring design. Quantitative consideration is performed for 17-km long ``dog-bone`` ring. Beam dynamics in alternative options of 6.3 and 2.3-km long damping rings is briefly discussed. 5 refs., 2 tabs.

  2. Identification of Mold and Dampness-Associated Respiratory Morbidity in 2 Schools: Comparison of Questionnaire Survey Responses to National Data

    ERIC Educational Resources Information Center

    Sahakian, Nancy M.; White, Sandra K.; Park, Ju-Hyeong; Cox-Ganser, Jean M.; Kreiss, Kathleen

    2008-01-01

    Background: Dampness and mold problems are frequently encountered in schools. Approximately one third of US public schools require extensive repairs or need at least 1 building replaced. This study illustrates how national data can be used to identify building-related health risks in school employees and students. Methods: School employees (n =…

  3. Identification of Mold and Dampness-Associated Respiratory Morbidity in 2 Schools: Comparison of Questionnaire Survey Responses to National Data

    ERIC Educational Resources Information Center

    Sahakian, Nancy M.; White, Sandra K.; Park, Ju-Hyeong; Cox-Ganser, Jean M.; Kreiss, Kathleen

    2008-01-01

    Background: Dampness and mold problems are frequently encountered in schools. Approximately one third of US public schools require extensive repairs or need at least 1 building replaced. This study illustrates how national data can be used to identify building-related health risks in school employees and students. Methods: School employees (n =…

  4. Damping characteristics of damaged fiber composite components

    NASA Technical Reports Server (NTRS)

    Eberle, K.

    1986-01-01

    Defects in fiber composite components produce changes with respect to the vibrational characteristics of the material. These changes can be recognized in the form of a frequency shift or an alteration of the damping process. The present investigation is concerned with questions regarding the possibility of a utilization of the changes in suitable defect-detecting inspection procedures. A description is given of a method for measuring the damping characteristics of a specimen. This method provides a spectrum of the damping coefficients of the sample as a basis for a comprehensive evaluation of the damping behavior. The correlation between defects and change in the damping characteristics is demonstrated with the aid of results obtained in measurements involving specimens of carbon-fiber composites and a component consisting of glass-fiber-reinforced plastics.

  5. Landau damping in a turbulent setting

    SciTech Connect

    Plunk, G. G.

    2013-03-15

    To address the problem of Landau damping in kinetic turbulence, we consider the forcing of the linearized Vlasov equation by a stationary random source. It is found that the time-asymptotic density response is dominated by resonant particle interactions that are synchronized with the source. The energy consumption of this response is calculated, implying an effective damping rate, which is the main result of this paper. Evaluating several cases, it is found that the effective damping rate can differ from the Landau damping rate in magnitude and also, remarkably, in sign. A limit is demonstrated in which the density and current become phase-locked, which causes the effective damping to be negligible; this result offers a fresh perspective from which to reconsider recent observations of kinetic turbulence satisfying critical balance.

  6. A finite element model with nonviscous damping

    NASA Technical Reports Server (NTRS)

    Roussos, L. A.; Hyer, M. W.; Thornton, E. A.

    1981-01-01

    A constitutive law by which structural damping is modeled as a relationship between stress, strain, and strain rate in a material is used in conjunction with the finite element method to develop general integral expressions for viscous and nonviscous damping matrices. To solve the set of nonlinear equations resulting from the presence of nonviscous damping, a solution technique is developed by modifying the Newmark method to accommodate an iterative solution and treat the nonviscous damping as a pseudo-force. The technique is then checked for accuracy and convergence in single- and multi-degree-of-freedom problems, and is found to be accurate and efficient for initial-condition problems with small nonviscous damping.

  7. Magnetic damping of rotation. [in satellites

    NASA Technical Reports Server (NTRS)

    Opik, E. J.

    1977-01-01

    Based on Wilson's (1977) article on the magnetic effects on space vehicles and other celestial bodies, the magnetic damping of rotation is considered. The inadequacy of the interstellar magnetic field in overcoming solar wind shielding and thus influencing the rotation of bodies is described. The ionospheric shielding of the interstellar field is discussed along with the permeability and magnetic damping by the solar or stellar wind. Star formation and angular momentum is discussed and attention is given to the magnetic damping of unshielded small bodies. Calculations of the rate for damping through random particle impact are made. Theories concerning the rotation of asteroids and the origin of meteorites are reviewed. The shielding process of ionospheric plasmas is outlined and the damping effect of the geomagnetic field on the rotation of artificial satellites is evaluated.

  8. Large space structure damping design

    NASA Technical Reports Server (NTRS)

    Pilkey, W. D.; Haviland, J. K.

    1983-01-01

    Several FORTRAN subroutines and programs were developed which compute complex eigenvalues of a damped system using different approaches, and which rescale mode shapes to unit generalized mass and make rigid bodies orthogonal to each other. An analytical proof of a Minimum Constrained Frequency Criterion (MCFC) for a single damper is presented. A method to minimize the effect of control spill-over for large space structures is proposed. The characteristic equation of an undamped system with a generalized control law is derived using reanalysis theory. This equation can be implemented in computer programs for efficient eigenvalue analysis or control quasi synthesis. Methods to control vibrations in large space structure are reviewed and analyzed. The resulting prototype, using electromagnetic actuator, is described.

  9. VIBRATION DAMPING AND SHOCK MOUNT

    DOEpatents

    Stevens, D.J.; Forman, G.W.

    1963-12-10

    A shock absorbing mount in which vibrations are damped by an interference fit between relatively movable parts of the mount is described. A pair of generally cup-shaped parts or members have skirt portions disposed in an oppositely facing nesting relationship with the skirt of one member frictionally engaging the skirt of the other. The outermost skirt may be slotted to provide spring-like segments which embrace the inner skirt for effecting the interference fit. Belleville washers between the members provide yieldable support for a load carried by the mount. When a resonant frequency of vibration forces acting upon the moumt attains a certain level the kinetic energy of these forces is absorbed by sliding friction between the parts. (AEC)

  10. Langmuir wave damping decreases slowly

    NASA Astrophysics Data System (ADS)

    Rose, Harvey

    2006-10-01

    The onset of stimulated Raman scatter in a single laser speckle occurs (D. S. Montgomery et al., Phys. Plasmas, 9, 2311 (2002)) at lower laser intensity, I, than predicted by linear theory based on classical Landau damping, νL, of the SRS daughter Langmuir wave. Does this imply that SRS onset in a speckled laser beam, propagating through long scale length plasma, is also at odds with linear theory? It has been shown (Harvey A. Rose and D. F. DuBois, Phys. Rev. Lett. 72, 2883 (1994)) that linear convective gain in speckles with large fluctuations of I about the average, , leads to onset at a value of , Ic, small compared to that for onset in a uniform beam. While nonlinear electron trapping effects may occur in very intense speckles, whether or not these effects are sufficient to lower the onset value of below Ic depends on how strongly electrons must be trapped before there is significant reduction in νL. As the amplitude of an SRS daughter Langmuir wave increases, its νL decreases by the factor ν/φb, due to the competition between electron trapping, with electron bounce frequency, φb, and escape of these trapped electrons by advection out of a speckle's side, at rate ν. This result (Harvey A. Rose and David A. Russell, Phys. Plasmas, 8, 4784 (2001)) is valid for ν/φb 1. In this talk I present a nonlinear, transit time damping, calculation of νL and find that reduction by a factor of two does not occur until φb/ν 5. This slow turn on of trapping effects suggests that the linear calculation of Ic is NIF relevant.

  11. Building Mathematical Models of Simple Harmonic and Damped Motion.

    ERIC Educational Resources Information Center

    Edwards, Thomas

    1995-01-01

    By developing a sequence of mathematical models of harmonic motion, shows that mathematical models are not right or wrong, but instead are better or poorer representations of the problem situation. (MKR)

  12. SLC positron damping ring optics design

    SciTech Connect

    Delahaye, J.P.; Rivkin, L.

    1984-12-01

    The basic SLAC Linear Collider operation scheme assumes the use of two damping rings, one for the e/sup -/, one for the e/sup +/, in order to reduce the colliding beam normalized emittances to 30..pi.. ..mu..radm hence raising the corresponding luminosity by a factor 170. The e/sup -/ damping ring which optics was designed by H. Wiedemann, has been extensively studied and modelled since it's completion at the end of 1982. The e/sup +/ damping ring to be built soon will be based on the same design except for some modifications resulting from the studies on the e/sup -/ damping ring which clearly pointed out two major optics weak points: the extracted normalized emittances are 30 to 60% bigger than the design values, which already left no margin for unavoidable blow-up between the damping rings and the SLC interaction point, and the chromaticity correction based on distributed sextupole components provided by shaping the ends of the bending magnet poles was insufficient. Moreover the QDI quadrupoles introduce a strong coupling between transverse planes due to an undesirable skew component. The present note describes the basic modifications of the ring lattice and main equipment positions in order to improve the first two points in the Positron Damping Ring. The QDI quadrupole design has already been modified and magnets of a new type will be implemented in both damping rings.

  13. Validation Of Equivalent Viscous Damping Methodologies

    NASA Astrophysics Data System (ADS)

    Vaquer Araujo, Xavier; Fransen, S. H. J. A.; Germes, S.; Thiry, N.

    2012-07-01

    An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle in the low-frequency domain. To obtain accurate predictions of the satellite’s dynamic environment it is essential that the damping of the system is correctly defined and taken into account within the resolution methodologies for the Coupled Loads Analysis (CLA). When working with finite element models, the materials’ damping is characterized by structural damping ratios. In addition, most of the load cases present in the CLA are transient excitations so the resolution of the equations of motion must be done in the time domain. Unfortunately, transient analyses cannot be carried out using structural damping models. Thus, a transformation from a structural to a viscous damping characterization is necessary. Nevertheless, this transformation is not trivial. There exist many methodologies aiming at computing an equivalent viscous damping matrix of the system so it can be used in transient analyses. This paper describes the results obtained in the validation of equivalent viscous damping methodologies used in the European Space Agency. This work permitted to identify the limitations of these methodologies and to come up with an enhanced methodology that predicts more reliable results.

  14. Material damping experiments at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Levine, Marie B.; White, Christopher

    2003-12-01

    NASA's James Webb Space Telescope (JWST) will be operating at temperatures below 40K to image in the infrared. The 7-m class telescope will require nanometric jitter stability of the optical elements such as the primary and secondary mirrors. Of particular concern is the vibration response of these cryogenic systems when subjected to on-board disturbance sources such as the reaction wheels, the amplitude of which is governed by damping. Unfortunately there is relatively little data available for flight grade materials at these temperatures and within the frequency bands of interest. The paper will describe the experimental setup designed to measure viscous damping to values as low 10^-4%. The tests measure damping from room temperature all the way down to 20K in a controlled thermal and disturbance free environment. Data is obtained for strain levels of about 0.1 micro-strain down to nano-strains to verify vibration level effects on material damping. Damping is also measured for several frequencies in the range of 20Hz to 300Hz to assess the trend of damping as a function of vibrational frequency. Data for several materials, such as Aluminum, Beryllium, Quartz, and various composites are presented. The data is compared to analytical predictions using the Zener damping theory and is shown to match well at room temperature but to disagree at colder temperatures.

  15. Bounce harmonic Landau damping of plasma waves

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Affolter, M.; Kabantsev, A. A.; Dubin, D. H. E.; Ashourvan, A.; Driscoll, C. F.

    2016-05-01

    We present measurements of bounce harmonic Landau damping due to z-variations in the plasma potential, created by an azimuthally symmetric "squeeze" voltage Vs applied to the cylindrical wall. Traditional Landau damping on spatially uniform plasma is weak in regimes where the wave phase velocity vp h≡ω/k is large compared to the thermal velocity. However, z-variations in plasma density and potential create higher spatial harmonics, which enable resonant wave damping by particles with bounce-averaged velocities vp h/n , where n is an integer. In our geometry, the applied squeeze predominantly generates a resonance at vp h/3 . Wave-coherent laser induced fluorescence measurements of particle velocities show a distinctive Landau damping signature at vp h/3 , with amplitude proportional to the applied Vs. The measured (small amplitude) wave damping is then proportional to Vs2 , in quantitative agreement with theory over a range of 20 in temperature. Significant questions remain regarding "background" bounce harmonic damping due to ubiquitous confinement fields and regarding the saturation of this damping at large wave amplitudes.

  16. Experimental verification of damping mechanisms in a composite beam

    NASA Technical Reports Server (NTRS)

    Cudney, Harley H.; Inman, Daniel J.

    1989-01-01

    A method of estimating the distributed damping parameters based on the measured modal parameters (frequency and damping ratios) was derived. Three different mathematical models were used to model the damping mechanism of a quasi-isotropic pultruded cantilevered beam. These three models were (1) viscous (air) damping, (2) strain rate damping, and (3) both viscous and strain rate damping. The eigenvalues of the partial differential equation model were found to be uninfluenced by any of the three assumed damping models. Values were obtained for each of the damping models as well as the modulus of elasticity of the beam. It was found that the two-parameter damping model provided the best fit to measured modal data. However, the two-parameter damping model could only reproduce the measured damping ratios to within 85 percent.

  17. Investigation on the mechanism of damping behavior of magnetorheological elastomers

    NASA Astrophysics Data System (ADS)

    Yang, Jie; Gong, Xinglong; Deng, Huaxia; Qin, Lijun; Xuan, Shouhu

    2012-12-01

    Magnetorheological elastomers (MREs) are a group of smart materials which have many applications such as dynamic vibration absorbers, engine mounts, and so on. The damping behavior is important for applications of MREs. However, the mechanism of the damping of MREs has not been investigated thoroughly. In this study, MREs are modeled as special particle reinforced composites with magneto-induced properties and the mechanism of the damping behavior of MREs is investigated theoretically and experimentally. It has been found that there are three types of damping property in MREs: the intrinsic damping, the interface damping and the magneto-mechanical damping. The presented damping model is successfully validated by damping tests on a series of MRE samples. Furthermore, the relationships between the damping properties and formulas of MREs are discussed; this provides guidance for the manufacture of MREs with various damping properties.

  18. A Resonant Damping Study Using Piezoelectric Materials

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

    2008-01-01

    Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

  19. Radiation damping of a polarizable particle

    NASA Astrophysics Data System (ADS)

    Novotny, Lukas

    2017-09-01

    A polarizable body moving in an external electromagnetic field will slow down. This effect is referred to as radiation damping and is analogous to Doppler cooling in atomic physics. Using the principles of special relativity we derive an expression for the radiation damping force and find that it solely depends on the scattered power. The cooling of the particle's center-of-mass motion is balanced by heating due to radiation pressure shot noise, giving rise to an equilibrium that depends on the ratio of the field's frequency and the particle's mass. While damping is of relativistic nature, heating has its roots in quantum mechanics.

  20. Oscillation damped movement of suspended objects

    SciTech Connect

    Jones, J.F.; Petterson, B.J.

    1988-01-01

    Transportation of objects using overhead cranes or manipulators can induce pendulum motion of the object. Residual oscillation from transportation typically must be damped or allowed to decay before the next process can take place. By properly programming the acceleration of the transporting device (e.g., crane) an oscillation damped transport and swing free stop is obtainable. This paper reviews the theory associated with oscillation damped trajectories for simply suspended objects and describes a particular implementation using a CIMCORP XR 6100 gantry robot. 8 refs., 7 figs., 1 tab.

  1. Nonlinear Landau damping of Alfven waves.

    NASA Technical Reports Server (NTRS)

    Hollweg, J. V.

    1971-01-01

    Demonstration that large-amplitude linearly or elliptically polarized Alfven waves propagating parallel to the average magnetic field can be dissipated by nonlinear Landau damping. The damping is due to the longitudinal electric field associated with the ion sound wave which is driven (in second order) by the Alfven wave. The damping rate can be large even in a cold plasma (beta much less than 1, but not zero), and the mechanism proposed may be the dominant one in many plasmas of astrophysical interest.

  2. Damping of the dipole vortex.

    PubMed

    Li, Xin; Pierce, Donna M; Arnoldus, Henk F

    2011-05-01

    When a circular electric dipole moment, rotating in the x-y plane, is embedded in a material with relative permittivity ε(r) and relative permeability μ(r), the field lines of energy flow of the emitted radiation are dramatically influenced by the surrounding material. For emission in free space, the field lines swirl around the z axis and lie on a cone. The direction of rotation of the field lines around the z axis is the same as the direction of rotation of the dipole moment. We found that when the real part of ε(r) is negative, the rotation of the field lines changes direction, and hence the energy counter-rotates the dipole moment. When there is damping in the material, due to an imaginary part of ε(r), the cone turns into a funnel, and the density of the field lines diminishes near the location of the source. In addition, all radiation is emitted along the z axis and the x-y plane, whereas for emission in free space, the radiation is emitted in all directions. It is also shown that the displacement of the dipole image in the far field depends on the material parameters and that the shift can be much larger than the shift of the image in free space.

  3. Turbine blade friction damping study

    NASA Technical Reports Server (NTRS)

    Dominic, R. J.

    1985-01-01

    A lumped parameter method, implemented on a VAX 11/780 computer shows that the primary parameters affecting the performance of the friction damper of the first stage turbine of the SSME high pressure fuel pump are: the damper-blade coefficient of friction; the normal force applied to the friction interface; the amplitude of the periodic forcing function; the relative phase angle of the forcing functions for adjacent blades bridged by a damper (effectively, the engine order of the forcing function); and the amount of hysteretic damping that acts to limit the vibration amplitude of the blade in its resonance modes. The low order flexural resonance vibration modes of HPFTP blades without dampers, with production dampers, and with two types of lightweight experimental dampers were evaluated in high speed spin pit tests. Results agree with those of the analytical study in that blades fitted with production friction dampers experienced the airfoil-alone flexural resonance mode, while those without dampers or with lighter weight dampers did not. No blades fitted with dampers experienced the whole blade flexural resonance mode during high speed tests, while those without dampers did.

  4. Eigensolutions of non-proportionally damped systems based on continuous damping sensitivity

    NASA Astrophysics Data System (ADS)

    Lázaro, Mario

    2016-02-01

    The viscous damping model has been widely used to represent dissipative forces in structures under mechanical vibrations. In multiple degree of freedom systems, such behavior is mathematically modeled by a damping matrix, which in general presents non-proportionality, that is, it does not become diagonal in the modal space of the undamped problem. Eigensolutions of non-proportional systems are usually estimated assuming that the modal damping matrix is diagonally dominant (neglecting the off-diagonal terms) or, in the general case, using the state-space approach. In this paper, a new closed-form expression for the complex eigenvalues of non-proportionally damped system is proposed. The approach is derived assuming small damping and involves not only the diagonal terms of the modal damping matrix, but also the off-diagonal terms, which appear under higher order. The validity of the proposed approach is illustrated through a numerical example.

  5. Random vibrations of quadratic damping systems. [optimum damping analysis for automobile suspension system

    NASA Technical Reports Server (NTRS)

    Sireteanu, T.

    1974-01-01

    An oscillating system with quadratic damping subjected to white noise excitation is replaced by a nonlinear, statistically equivalent system for which the associated Fokker-Planck equation can be exactly solved. The mean square responses are calculated and the optimum damping coefficient is determined with respect to the minimum mean square acceleration criteria. An application of these results to the optimization of automobile suspension damping is given.

  6. Random vibrations of quadratic damping systems. [optimum damping analysis for automobile suspension system

    NASA Technical Reports Server (NTRS)

    Sireteanu, T.

    1974-01-01

    An oscillating system with quadratic damping subjected to white noise excitation is replaced by a nonlinear, statistically equivalent system for which the associated Fokker-Planck equation can be exactly solved. The mean square responses are calculated and the optimum damping coefficient is determined with respect to the minimum mean square acceleration criteria. An application of these results to the optimization of automobile suspension damping is given.

  7. Oscillation damping means for magnetically levitated systems

    DOEpatents

    Post, Richard F.

    2009-01-20

    The present invention presents a novel system and method of damping rolling, pitching, or yawing motions, or longitudinal oscillations superposed on their normal forward or backward velocity of a moving levitated system.

  8. Linear collisionless Landau damping in Hilbert space

    NASA Astrophysics Data System (ADS)

    Zocco, Alessandro

    2015-08-01

    The equivalence between the Laplace transform (Landau, J. Phys. USSR 10 (1946), 25) and Hermite transform (Zocco and Schekochihin, Phys. Plasmas 18, 102309 (2011)) solutions of the linear collisionless Landau damping problem is proven.

  9. The plastic scintillator detector for DAMPE

    NASA Astrophysics Data System (ADS)

    Yu, Yuhong; Sun, Zhiyu; Su, Hong; Yang, Yaqing; Liu, Jie; Kong, Jie; Xiao, Guoqing; Ma, Xinwen; Zhou, Yong; Zhao, Hongyun; Mo, Dan; Zhang, Yongjie; Yang, Peng; Chen, Junling; Yang, Haibo; Fang, Fang; Zhang, Shengxia; Yao, HuiJun; Duan, Jinglai; Niu, Xiaoyang; Hu, Zhengguo; Wang, Zhaomin; Wang, Xiaohui; Zhang, Jingzhe; Liu, Wenqiang

    2017-09-01

    The DArk Matter Particle Explorer (DAMPE) is a general purpose satellite-borne high energy γ - ray and cosmic ray detector. Among the scientific objectives of DAMPE are the search for the origin of cosmic rays and an understanding of the Dark Matter particles. As one of the four detectors in DAMPE, the Plastic Scintillator Detector (PSD) plays an important role in the particle charge measurement and the photons/electrons discrimination. It can identify the atomic number Z/charge states of relativistic ions from H to Fe and the detection efficiency for Z = 1 particles can reach 0.9999. The PSD has been working reliably since the successfully launching of DAMPE on December 17, 2015. In this paper, the design, assembly, qualification tests of the PSD and some of the performance measured on the ground are presented in detail.

  10. Roll Damping Characterisation Program: User Guide

    DTIC Science & Technology

    2014-06-01

    sallying test. The Defence Science and Technology Organisation (DSTO) have developed a software-based tool called the Roll Damping Characterisation...Murray Riding Maritime Division Murray obtained a Bachelor of Science (Honours) Degree from the

  11. Modification of spastic gait through mechanical damping.

    PubMed

    Maki, B E; Rosen, M J; Simon, S R

    1985-01-01

    The effect of dissipative mechanical loads on spastic gait has been studied, to evaluate the feasibility of using mechanically damped orthoses to effect functional improvements in the gait of spastic patients. This concept is based on a hypothesis citing uninhibited, velocity-dependent stretch reflexes as a possible causal factor in spastic gait abnormalities, such as equinus and back-kneeing. In order to screen potential experimental subjects and to quantify velocity-dependent reflex behaviour, ankle rotation experiments and filmed gait analysis were performed. The results supported the existence of a velocity threshold. Orthosis simulation experiments were performed with one spastic subject, using a wearable, computer-controlled, electromechanical, below-knee orthosis simulator to apply a variety of damping loads to the ankle as the subject walked. Results indicated that appropriate damping can improve local joint kinematics. The damping causes a reduction in muscle stretch velocity which apparently results in reduced spastic reflex activity.

  12. Electron beam depolarization in a damping ring

    SciTech Connect

    Minty, M.

    1993-04-01

    Depolarization of a polarized electron beam injected into a damping ring is analyzed by extending calculations conventionally applied to proton synchrotrons. Synchrotron radiation in an electron ring gives rise to both polarizing and depolarizing effects. In a damping ring, the beam is stored for a time much less than the time for self polarization. Spin flip radiation may therefore be neglected. Synchrotron radiation without spin flips, however, must be considered as the resonance strength depends on the vertical betatron oscillation amplitude which changes as the electron beam is radiation damped. An expression for the beam polarization at extraction is derived which takes into account radiation damping. The results are applied to the electron ring at the Stanford Linear Collider and are compared with numerical matrix formalisms.

  13. Simplified Model of Nonlinear Landau Damping

    SciTech Connect

    N. A. Yampolsky and N. J. Fisch

    2009-07-16

    The nonlinear interaction of a plasma wave with resonant electrons results in a plateau in the electron distribution function close to the phase velocity of the plasma wave. As a result, Landau damping of the plasma wave vanishes and the resonant frequency of the plasma wave downshifts. However, this simple picture is invalid when the external driving force changes the plasma wave fast enough so that the plateau cannot be fully developed. A new model to describe amplification of the plasma wave including the saturation of Landau damping and the nonlinear frequency shift is proposed. The proposed model takes into account the change of the plasma wave amplitude and describes saturation of the Landau damping rate in terms of a single fluid equation, which simplifies the description of the inherently kinetic nature of Landau damping. A proposed fluid model, incorporating these simplifications, is verified numerically using a kinetic Vlasov code.

  14. Turbine blade with tuned damping structure

    DOEpatents

    Campbell, Christian X.; Messmann, Stephen J.

    2015-09-01

    A turbine blade is provided comprising: a root; an airfoil comprising an external wall extending radially from the root and having a radially outermost portion; and a damping structure. The external wall may comprise first and second side walls joined together to define an inner cavity of the airfoil. The damping structure may be positioned within the airfoil inner cavity and coupled to the airfoil so as to define a tuned mass damper.

  15. Quantum damped oscillator I: Dissipation and resonances

    SciTech Connect

    Chruscinski, Dariusz

    2006-04-15

    Quantization of a damped harmonic oscillator leads to so called Bateman's dual system. The corresponding Bateman's Hamiltonian, being a self-adjoint operator, displays the discrete family of complex eigenvalues. We show that they correspond to the poles of energy eigenvectors and the corresponding resolvent operator when continued to the complex energy plane. Therefore, the corresponding generalized eigenvectors may be interpreted as resonant states which are responsible for the irreversible quantum dynamics of a damped harmonic oscillator.

  16. Analysis of nonlinear damping properties of carbon

    NASA Astrophysics Data System (ADS)

    Kazakova, Olga I.; Smolin, Igor Yu.; Bezmozgiy, Iosif M.

    2016-11-01

    This paper describes research results of nonlinear damping properties of carbon fiber reinforced plastics. The experimental and computational research is performed on flat composite specimens with the gradual structure complication (from 1 to 12 layers). Specimens are subjected to three types of testing which are modal, harmonic and transient analyses. Relationships between the amplitude response and damping ratio are obtained by means of the analysis of variance as the result of this research.

  17. Optimal constrained layer damping with partial coverage

    NASA Astrophysics Data System (ADS)

    Marcelin, J.-L.; Trompette, Ph.; Smati, A.

    1992-12-01

    This paper deals with the optimal damping of beams constrained by viscoelastic layers when only one or several portions of the beam are covered. An efficient finite element model for dynamic analysis of such beams is used. The design variables are the dimensions and prescribed locations of the viscoelastic layers and the objective is the maximum viscoelastic damping factor. The method for nonlinear programming in structural optimization is the so-called method of moving asymptotes.

  18. Damping Studies of Ceramic Reinforced Aluminum

    DTIC Science & Technology

    1991-03-01

    13 3. Microstructure of A356 aluminum with 0 and 20 v/o SiC .................................. 13 4. The effect of temperature...15 7. Damping capacity versus storage modulus for A356 Aluminum matrix composites measured at 0.1, 1, and 10 Hz from -10 to 250°C...15 8. The effect of frequency on the damping capacity of A356 aluminum matrix composites measured at 0.1, 1, and 10 Hz

  19. Microscale damping using thin film active materials

    NASA Astrophysics Data System (ADS)

    Kerrigan, Catherine A.; Ho, Ken K.; Mohanchandra, K. P.; Carman, Gregory P.

    2007-04-01

    This paper focuses on understanding and developing a new approach to dampen MEMS structures using both experiments and analytical techniques. Thin film Nitinol and thin film Terfenol-D are evaluated as a damping solution to the micro scale damping problem. Stress induced twin boundary motion in Nitinol is used to passively dampen potentially damaging vibrations. Magnetic domain wall motion is used to passively dampen vibration in Terfenol-D. The thin films of Nitinol, Nitinol/Silicon laminates and Nitinol/Terfenol-D/Nickel laminates have been produced using a sputter deposition process and damping properties have been evaluated. Dynamic testing shows substantial damping (tan δ) measurable in each case. Nitinol film samples were tested in the Differential Scanning Calorimetry (DSC) to determine phase transformation temperatures. The twin boundary mechanism by which energy absorption occurs is present at all points below the Austenite start temperature (approximately 69°C in our film) and therefore allows damping at cold temperatures where traditional materials fail. Thin film in the NiTi/Si laminate was found to produce substantially higher damping (tan δ = 0.28) due to the change in loading condition. The NiTi/Si laminate sample was tested in bending allowing the twin boundaries to be reset by cyclic tensile and compressive loads. The thin film Terfenol-D in the Nitinol/Terfenol-D/Nickel laminate was shown to produce large damping (tan δ = 0.2). In addition to fabricating and testing, an analytical model of a heterogeneous layered thin film damping material was developed and compared to experimental work.

  20. Spatial versus time hysteresis in damping mechanisms

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Fabiano, R. H.; Wang, Y.; Inman, D. J.; Cudney, H., Jr.

    1988-01-01

    A description is given of continuing investigations on the task of estimating internal damping mechanisms in flexible structures. Specifically, two models for internal damping in Euler-Bernoulli beams are considered: spatial hysteresis and time hysteresis. A theoretically sound computational algorithm for estimation is described, and experimental results are discussed. It is concluded that both models perform well in the sense that they accurately predict response for the experiments conducted.

  1. Measurement of damping of graphite epoxy materials

    NASA Technical Reports Server (NTRS)

    Crocker, M. J.

    1985-01-01

    Work on a damping measurement test apparatus is discussed. The device is designed to excite tube specimens in a vacuum chamber. Also some experiments were conducted on a tube specimen to confirm previously reported results. A table of data showing the results of forced vibration tests using a half ring and a free-free boundary is given. The main purpose was to study the effect of the frequency resolution on the damping ratio measurements.

  2. Transient analysis for damping identification in rotating composite beams with integral damping layers

    NASA Astrophysics Data System (ADS)

    Smith, Clifford B.; Wereley, Norman M.

    1996-10-01

    The first objective of this paper is to evaluate the performance of damping identification algorithms. The second objective is to determine the feasibility of damping augmentation in rotating composite beams via passive constrained layer damping (PCLD). Damping identification schemes were applied to four rectangular cross-section laminated composite beams with cocured integral damping layers over the span of the beam. The cocured beam consisted of a twenty-ply balanced and symmetric cross-ply Gr/Ep composite host structure, a top and bottom damping layer of viscoelastic material (VEM), and a 2-ply Gr/Ep constraining layer sandwiching the viscoelastic material to the host structure. Four VEM thicknesses were considered: 0, 5, 10, and 15 mils. The cantilevered beams were tested at rotational speeds ranging from 0 to 900 RPM in a vacuum chamber. Excitation in bending was provided using piezo actuators, and the bending response was measured using full strain gauge bridges. Transient data were analysed using logarithmic decrement, a Hilbert transform technique, and an FFT- based moving block analysis. When compared to the beam with no VEM, a 19.2% volume fraction (15 mil layer) of viscoelastic in the beam produced a 400% increase in damping ratio in the non-rotating case, while at 900 RPM, the damping ratio increased only 360%. Overall structural damping was reduced as a function of RPM, due to centrifugal stiffening.

  3. Damping of Sound Waves in Strong Centrifugal Field

    NASA Astrophysics Data System (ADS)

    Bogovalov, S. V.; Kislov, V. A.; Tronin, I. V.

    A method for numerical calculation of the sound wave damping and dispersion law in a strong centrifugal field of the order of 106 g is considered. The damping is defined from the width of the resonance peak for different wave vectors. In the strong centrifugal field damping of the sound waves essentially exceeds the damping in the quiescent gas.

  4. Validation of equivalent viscous damping methodologies

    NASA Astrophysics Data System (ADS)

    Vaquer Araujo, Xavier; Fransen, Sebastiaan H. J. A.; Germès, Sylvain; Thiry, Nicolas

    2013-06-01

    An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle in the low-frequency domain. To obtain accurate predictions of the satellite's dynamic environment, it is essential that the damping of the system is correctly defined and taken into account within the resolution methodologies for the coupled loads analysis (CLA). When working with finite element models, the materials' damping is characterized by structural damping ratios. In addition, most of the load cases present in the CLA are transient excitations, and so the resolution of the equations of motion must be done in the time domain. Unfortunately, in the CLA, transient analyses cannot be carried out using structural damping models. Thus, a transformation from a structural to a viscous damping characterization is necessary in this case. Nevertheless, this transformation is not trivial. There exist many methodologies for computing an equivalent viscous damping (EqVD) matrix of the system which can be used in transient analyses. This paper describes the results obtained from the validation of EqVD methodologies used in the European Space Agency. This work identifies the limitations of these methodologies and comes up with an enhanced methodology that predicts more reliable results.

  5. Hybrid Damping System for an Electronic Equipment Mounting Shelf

    NASA Technical Reports Server (NTRS)

    Voracek, David; Kolkailah, Faysal A.; Cavalli, J. R.; Elghandour, Eltahry

    1997-01-01

    The objective of this study was to design and construct a vibration control system for an electronic equipment shelf to be evaluated in the NASA Dryden FTF-11. The vibration control system was a hybrid system which included passive and active damping techniques. Passive damping was fabricated into the equipment shelf using ScothDamp(trademark) damping film and aluminum constraining layers. Active damping was achieved using a two channel active control circuit employing QuickPack(trademark) sensors and actuators. Preliminary Chirp test results indicated passive damping smoothed the frequency response while active damping reduced amplitudes of the frequency response for most frequencies below 500Hz.

  6. Hybrid Damping System for an Electronic Equipment Mounting Shelf

    NASA Technical Reports Server (NTRS)

    Voracek, David; Kolkailah, Faysal A.; Cavalli, J. R.; Elghandour, Eltahry

    1997-01-01

    The objective of this study was to design and construct a vibration control system for an electronic equipment shelf to be evaluated in the NASA Dryden FTF-II. The vibration control system was a hybrid system which included passive and active damping techniques. Passive damping was fabricated into the equipment shelf using ScothDamp(trademark) damping film and aluminum constraining layers. Active damping was achieved using a two channel active control circuit employing QuickPack(trademark) sensors and actuators. Preliminary Chirp test results indicated passive damping smoothed the frequency response while active damping reduced amplitudes of the frequency response for most frequencies below 500Hz.

  7. The Frequency and Damping of Soil-Structure Systems with Embedded Foundation

    SciTech Connect

    Ghannad, M. Ali; Rahmani, Mohammad T.; Jahankhah, Hossein

    2008-07-08

    The effect of foundation embedment on fundamental period and damping of buildings has been the title of several researches in three past decades. A review of the literature reveals some discrepancies between proposed formulations for dynamic characteristics of soil-embedded foundation-structure systems that raise the necessity of more investigation on this issue. Here, first a set of approximate polynomial equations for soil impedances, based on numerical data calculated from well known cone models, are presented. Then a simplified approach is suggested to calculate period and damping of the whole system considering soil medium as a viscoelastic half space. The procedure includes both material and radiation damping while frequency dependency of soil impedance functions is not ignored. Results show that soil-structure interaction can highly affect dynamic properties of system. Finally the results are compared with one of the commonly referred researches.

  8. Geometric reasoning about damped and forced harmonic motion in the complex plane

    NASA Astrophysics Data System (ADS)

    Close, Hunter G.

    2015-09-01

    Complex-valued functions are commonly used to solve differential equations for one-dimensional motion of a harmonic oscillator with linear damping, a sinusoidal driving force, or both. However, the usual approach treats complex functions as an algebraic shortcut, neglecting geometrical representations of those functions and discarding imaginary parts. This article emphasizes the benefit of using diagrams in the complex plane for such systems, in order to build intuition about harmonic motion and promote spatial reasoning and the use of varied representations. Examples include the analysis of exact time sequences of various kinematic events in damped harmonic motion, sense-making about the phase difference between a driving force and the resulting motion, and understanding the discrepancy between the resonant frequency and the natural undamped frequency for forced, damped harmonic motion. The approach is suitable for supporting instruction in undergraduate upper-division classical mechanics.

  9. Numerical determination of the transmissibility characteristics of a squeeze film damped forced vibration system

    NASA Technical Reports Server (NTRS)

    Sutton, M. A.; Davis, P. K.

    1976-01-01

    Numerical solutions of the governing equations of motion of a liquid squeeze film damped forced vibration system were carried out to examine the feasibility of using a liquid squeeze film to cushion and protect large structures, such as buildings, located in areas of high seismic activity. The mathematical model used was that for a single degree of freedom squeeze film damped spring mass system. The input disturbance was simulated by curve fitting actual seismic data with an eleventh order Lagranging polynomial technique. Only the normal component of the seismic input was considered. The nonlinear, nonhomogeneous governing differential equation of motion was solved numerically to determine the transmissibility over a wide range of physical parameters using a fourth-order Runge-Kutta technique. It is determined that a liquid squeeze film used as a damping agent in a spring-mass system can significantly reduce the response amplitude for a seismic input disturbance.

  10. Cross Section of Legislative Approaches to Reducing Indoor Dampness and Mold

    PubMed Central

    Boese, Gerald W.

    2017-01-01

    Exposure to indoor dampness and mold is associated with numerous adverse respiratory conditions, including asthma. While no quantitative health-based threshold currently exists for mold, the conditions that support excessive dampness and mold are known and preventable; experts agree that controlling these conditions could lead to substantial savings in health care costs and improvement in public health. This article reviews a sample of state and local policies to limit potentially harmful exposures. Adoption of laws to strengthen building codes, specify dampness and mold in habitability laws, regulate mold contractors, and other legislative approaches are discussed, as are key factors supporting successful implementation. Communicating these lessons learned could accelerate the process for other jurisdictions considering similar approaches. Information about effectiveness of legislation as prevention is lacking; thus, evaluation could yield important information to inform the development of model state or local laws that significantly address mold as a public health concern. PMID:27977504

  11. Asthma related to workplace dampness and impaired work ability.

    PubMed

    Karvala, Kirsi; Nordman, Henrik; Luukkonen, Ritva; Uitti, Jukka

    2014-01-01

    To examine the long-term effects on work ability among patients previously diagnosed with occupational asthma (OA) or work-exacerbated asthma (WEA) or symptoms in relation to workplace dampness. A questionnaire follow-up was used to study 1,098 patients (of whom 87 % were female) examined because of a suspected occupational respiratory disease caused by building dampness and mold. Self-rated work ability and early withdrawal from work were the two outcomes of the study. As determinants, we investigated the influence of the asthma diagnosis given in the initial examinations (OA or WEA), the number of persistent indoor air symptoms, and the psychosocial factors at work. With a mean follow-up of 7.8 years, 40 % of the OA patients, under 65 years of age, were outside worklife versus 23 % of the WEA patients and 15 % of the patients with only upper respiratory symptoms at baseline. The diagnosis of OA was associated with a nearly sixfold risk for early withdrawal from work in a comparison with a reference group with upper respiratory symptoms. A perceived poor social climate at work and poor experiences with supervisory co-operation were associated with impaired work ability outcomes. Those with multiple, long-term indoor air symptoms considerably more often perceived their work ability to be poor when compared with those with less significant symptoms. Adverse work ability outcomes are associated with asthma in relation to workplace dampness. The study raises the need for effective preventive measures in order to help workers with indoor air symptoms sustain their work ability.

  12. Introduction to the scientific application system of DAMPE (On behalf of DAMPE collaboration)

    NASA Astrophysics Data System (ADS)

    Zang, Jingjing

    2016-07-01

    The Dark Matter Particle Explorer (DAMPE) is a high energy particle physics experiment satellite, launched on 17 Dec 2015. The science data processing and payload operation maintenance for DAMPE will be provided by the DAMPE Scientific Application System (SAS) at the Purple Mountain Observatory (PMO) of Chinese Academy of Sciences. SAS is consisted of three subsystems - scientific operation subsystem, science data and user management subsystem and science data processing subsystem. In cooperation with the Ground Support System (Beijing), the scientific operation subsystem is responsible for proposing observation plans, monitoring the health of satellite, generating payload control commands and participating in all activities related to payload operation. Several databases developed by the science data and user management subsystem of DAMPE methodically manage all collected and reconstructed science data, down linked housekeeping data, payload configuration and calibration data. Under the leadership of DAMPE Scientific Committee, this subsystem is also responsible for publication of high level science data and supporting all science activities of the DAMPE collaboration. The science data processing subsystem of DAMPE has already developed a series of physics analysis software to reconstruct basic information about detected cosmic ray particle. This subsystem also maintains the high performance computing system of SAS to processing all down linked science data and automatically monitors the qualities of all produced data. In this talk, we will describe all functionalities of whole DAMPE SAS system and show you main performances of data processing ability.

  13. Collisional damping of the geodesic acoustic mode with toroidal rotation. I. Viscous damping

    SciTech Connect

    Gong, Xueyu; Xie, Baoyi; Chen, You; Yu, Jiangmei; Yu, Jun; Guo, Wenfeng

    2016-03-15

    With the dispersion relation derived for the geodesic acoustic mode in toroidally rotating tokamak plasmas using the fluid model, the effect of the toroidal rotation on the collisional viscous damping of the geodesic acoustic mode is investigated. It is found that the collisional viscous damping of the geodesic acoustic mode has weak increase with respect to the toroidal Mach number.

  14. Effects of damping wigglers on beam dynamics in the NLC damping rings

    SciTech Connect

    Wolski, Andrzej; Wu, Ying

    2001-06-16

    To achieve the required damping time in the main damping rings for the Next Linear Collider (NLC), a wiggler will be required in each ring with integrated squared field strength up to 110 T{sup 2}m. There are concerns that nonlinear components of the wiggler field will damage the dynamic aperture of the ring, leading to poor injection efficiency. Severe effects from an insertion device have been observed and corrected in SPEAR 2. In this paper, we describe a model that we have developed to study the effects of the damping wiggler, compare the predictions of the model with actual experience in the case of the SPEAR 2 wiggler, and consider the predicted effects of current damping wiggler design on the NLC main damping rings.

  15. Prevalence of Residential Dampness and Mold Exposure in a University Student Population

    PubMed Central

    Lanthier-Veilleux, Mathieu; Généreux, Mélissa; Baron, Geneviève

    2016-01-01

    The impact of residential dampness or mold on respiratory health is well established but few studies have focused on university students. This study aims to: (a) describe the prevalence of exposure to residential dampness or mold in university students according to socio-geographic factors and (b) identify associated housing characteristics. A web survey was conducted in 2014 among the 26,676 students registered at the Université de Sherbrooke (QC, Canada). Residential dampness and mold being closely intertwined, they were considered as a single exposure and assessed using a validated questionnaire. Exposure was compared according to socio-geographic and housing characteristics using chi-square tests and logistic regressions. Among the 2097 participants included in the study (response rate: 8.1%), over 80% were tenants. Residential exposure to dampness or mold was frequent (36.0%, 95% CI: 33.9–38.1). Marked differences for this exposure were noted according to home ownership (39.7% vs. 25.5% among tenants and owners respectively; OR = 1.92%, 95% CI: 1.54–2.38). Campus affiliation, household composition and the number of residents per building were associated with exposure to dampness or mold (p < 0.01), while sex and age were not. Exposure was also associated with older buildings, and buildings in need of renovations and lacking proper ventilation (p < 0.001). This study highlights the potential risk of university students suffering from mold-related health effects given their frequent exposure to this agent. Further research is needed to fully evaluate the mold-related health impact in this at risk group. PMID:26861364

  16. Prevalence of Residential Dampness and Mold Exposure in a University Student Population.

    PubMed

    Lanthier-Veilleux, Mathieu; Généreux, Mélissa; Baron, Geneviève

    2016-02-05

    The impact of residential dampness or mold on respiratory health is well established but few studies have focused on university students. This study aims to: (a) describe the prevalence of exposure to residential dampness or mold in university students according to socio-geographic factors and (b) identify associated housing characteristics. A web survey was conducted in 2014 among the 26,676 students registered at the Université de Sherbrooke (QC, Canada). Residential dampness and mold being closely intertwined, they were considered as a single exposure and assessed using a validated questionnaire. Exposure was compared according to socio-geographic and housing characteristics using chi-square tests and logistic regressions. Among the 2097 participants included in the study (response rate: 8.1%), over 80% were tenants. Residential exposure to dampness or mold was frequent (36.0%, 95% CI: 33.9-38.1). Marked differences for this exposure were noted according to home ownership (39.7% vs. 25.5% among tenants and owners respectively; OR = 1.92%, 95% CI: 1.54-2.38). Campus affiliation, household composition and the number of residents per building were associated with exposure to dampness or mold (p < 0.01), while sex and age were not. Exposure was also associated with older buildings, and buildings in need of renovations and lacking proper ventilation (p < 0.001). This study highlights the potential risk of university students suffering from mold-related health effects given their frequent exposure to this agent. Further research is needed to fully evaluate the mold-related health impact in this at risk group.

  17. Gilbert damping in magnetic layered systems

    NASA Astrophysics Data System (ADS)

    Barati, E.; Cinal, M.; Edwards, D. M.; Umerski, A.

    2014-07-01

    The Gilbert damping constant present in the phenomenological Landau-Lifshitz-Gilbert equation describing the dynamics of magnetization is calculated for ferromagnetic metallic films as well as Co/nonmagnet (NM) bilayers. The calculations are done within a realistic nine-orbital tight-binding model including spin-orbit coupling. The convergence of the damping constant expressed as a sum over the Brillouin zone is remarkably improved by introducing finite temperature into the electronic occupation factors and subsequent summation over the Matsubara frequencies. We investigate how the Gilbert damping constant depends on the ferromagnetic film thickness as well as on the thickness of the nonmagnetic cap in Co/NM bilayers (NM=Cu, Pd, Ag, Pt, and Au). The obtained theoretical dependence of the damping constant on the electron-scattering rate, describing the average lifetime of electronic states, varies substantially with the ferromagnetic film thickness and it differs significantly from the dependence for bulk ferromagnetic metals. The presence of nonmagnetic caps is found to largely enhance the magnetic damping in Co/NM bilayers in accordance with experimental data. Unlike Cu, Ag, and Au a particularly strong enhancement is obtained for Pd and Pt caps. This is attributed to the combined effect of the large spin-orbit couplings of Pd and Pt and the simultaneous presence of d states at the Fermi level in these two metals. The calculated Gilbert damping constant also shows an oscillatory dependence on the thicknesses of both ferromagnetic and nonmagnetic parts of the investigated systems which is attributed to quantum-well states. Finally, the expression for contributions to the damping constant from individual atomic layers is derived. The obtained distribution of layer contributions in Co/Pt and Co/Pd bilayers proves that the enhanced damping which affects the dynamics of the magnetization in the Co film originates mainly from a region within the nonmagnetic part of the

  18. Smart earthquake-resistant materials: using time-released adhesives for damping, stiffening, and deflection control

    NASA Astrophysics Data System (ADS)

    Dry, Carolyn M.

    1996-04-01

    Preventing buildings and bridges from damage from severe dynamic loading events is a primary goal of civil infrastructure. Present designs attempt to control structural response by making the structures more massive, by increasing lateral stiffness through bracing, and by damping technology such as mass damping and base-isolation. These attempts affect portions of the governing equation: for an idealized building frame or bridge, the free vibrational behavior is described by Mu + cu + ku equals -mug(t) where m equals mass, c equals damping coefficient, k equals lateral stiffness, u equals deflection, and ug(t) equals ground acceleration. The use of adhesive released internally in a material based way of addressing the problem. The time release of low modulus adhesive chemicals would assist the damping characteristics of the structure, use of a stiffer adhesive would allow the damaged structure to regain some lateral stiffness (k) and adjustment of the set times of the adhesives would act to control the deflection. These can be thought of as potential new method of controlling vibration of behavior in case of a dynamic loading event. In past experiments, self-healing concrete matrices were shown to increase post-yield deflection and load carrying capability by the release and setting of adhesives. The results were promising in resisting damage of dynamic loads applied to frames. This indicates that self-healing concrete would be extremely valuable in civil engineering structures that were subjected to failure-inducing loads such as earthquakes.

  19. Radiation damping in microcoil NMR probes

    NASA Astrophysics Data System (ADS)

    Krishnan, V. V.

    2006-04-01

    Radiation damping arises from the field induced in the receiver coil by large bulk magnetization and tends to selectively drive this magnetization back to equilibrium much faster than relaxation processes. The demand for increased sensitivity in mass-limited samples has led to the development of microcoil NMR probes that are capable of obtaining high quality NMR spectra with small sample volumes (nL-μL). Microcoil probes are optimized to increase sensitivity by increasing either the sample-to-coil ratio (filling factor) of the probe or quality factor of the detection coil. Though radiation damping effects have been studied in standard NMR probes, these effects have not been measured in the microcoil probes. Here a systematic evaluation of radiation damping effects in a microcoil NMR probe is presented and the results are compared with similar measurements in conventional large volume samples. These results show that radiation-damping effects in microcoil probe is much more pronounced than in 5 mm probes, and that it is critically important to optimize NMR experiments to minimize these effects. As microcoil probes provide better control of the bulk magnetization, with good RF and B0 inhomogeneity, in addition to negligible dipolar field effects due to nearly spherical sample volumes, these probes can be used exclusively to study the complex behavior of radiation damping.

  20. Radiation damping in microcoil NMR probes.

    PubMed

    Krishnan, V V

    2006-04-01

    Radiation damping arises from the field induced in the receiver coil by large bulk magnetization and tends to selectively drive this magnetization back to equilibrium much faster than relaxation processes. The demand for increased sensitivity in mass-limited samples has led to the development of microcoil NMR probes that are capable of obtaining high quality NMR spectra with small sample volumes (nL-microL). Microcoil probes are optimized to increase sensitivity by increasing either the sample-to-coil ratio (filling factor) of the probe or quality factor of the detection coil. Though radiation damping effects have been studied in standard NMR probes, these effects have not been measured in the microcoil probes. Here a systematic evaluation of radiation damping effects in a microcoil NMR probe is presented and the results are compared with similar measurements in conventional large volume samples. These results show that radiation-damping effects in microcoil probe is much more pronounced than in 5 mm probes, and that it is critically important to optimize NMR experiments to minimize these effects. As microcoil probes provide better control of the bulk magnetization, with good RF and B0 inhomogeneity, in addition to negligible dipolar field effects due to nearly spherical sample volumes, these probes can be used exclusively to study the complex behavior of radiation damping.

  1. Structural damping using encapsulated shear thickening fluids

    NASA Astrophysics Data System (ADS)

    Soutrenon, Mathieu; Michaud, Véronique

    2012-04-01

    Smart structures with tunable damping and stiffness characteristics are of high interest to aerospace applications, but often require an external power source to be activated. This can be avoided by using highly concentrated silica suspensions, which exhibit a shear-thickening behavior, linked to a dramatic increase in viscous dissipation. These materials are however liquid at rest, and sensitive to humidity, so they are difficult to implement as such into structural applications. In the present work, highly concentrated solutions of monodisperse silica particles in PEG were selected for their strong thickening effect at rather low critical shear strain. Damping properties were characterized by measuring the energy dissipated per cycle at low frequency (<2Hz) during oscillatory tests using a rheometer. STF were impregnated in an open-cell foam scaffold and encapsulated into a RTV-silicone to produce patches that can be handled easily. Silicone also protects the STF against outgassing or humidity pickup. Experimental results show a simultaneous increase of stiffness and damping properties for theses patches at low frequencies and large strains. Damping is thus getting closer to the range of elastomeric commercial damping materials, possibly overtaking them in specific conditions.

  2. Damping and spectral formation of upstream whistlers

    SciTech Connect

    Orlowski, D.S.; Russell, C.T.; Krauss-Varban, D.

    1995-09-01

    Previous studies have indicated that damping rates of upstream whistlers strongly depend on the details of the electron distribution function. Moreover, detailed analysis of Doppler shift and the whistler dispersion relation indicate that upstream whistlers propagate obliquely in a finite band of frequencies. In this paper we present results of a kinetic calculation of damping lengths of wideband whistlers using the sum of seven drifting bi-Maxwellian electron distributions as a best fit to the ISEE 1 electron data. For two cases, when upstream whistlers are observed, convective damping lengths derived from ISEE magnetic field and ephemeris data are compared with theoretical results. We find that the calculated convective damping lengths are consistent with the data and that upstream whistlers remain marginally stable. We also show that the slope of plasma frame spectra of upstream whistlers, obtained by direct fitting of the observed spectra, is between 5 and 7. The overall spectral, wave, and particle characteristics, proximity to the shock, as well as propagation and damping properties indicated that these waves cannot be generated locally. Instead, the observed upstream whistlers arise in the shock ramp, most likely by a variety of cross-field drift and/or anisotropy driven instabilities. 57 refs., 11 figs.

  3. Noise Transmission Characteristics of Damped Plexiglas Windows

    NASA Technical Reports Server (NTRS)

    Gibbs, Gary P.; Buehrle, Ralph D.; Klos, Jacob; Brown, Sherilyn A.

    2002-01-01

    Most general aviation aircraft utilize single layer plexiglas material for the windshield and side windows. Adding noise control treatments to transparent panels is a challenging problem. In this paper, damped plexiglas windows are evaluated for replacement of conventional windows in general aviation aircraft to reduce the structure-borne and airborne noise transmitted into the interior. In contrast to conventional solid windows, the damped plexiglas window panels are fabricated using two or three layers of plexiglas with transparent viscoelastic damping material sandwiched between the layers. Results from acoustic tests conducted in the NASA Langley Structural Acoustic Loads and Transmission (SALT) facility are used to compare different designs of the damped plexiglas panels with solid windows of the same nominal thickness. Comparisons of the solid and damped plexiglas panels show reductions in the radiated sound power of up to 8 dB at low frequency resonances and as large as 4.5 dB over a 4000 Hz bandwidth. The weight of the viscoelastic treatment was approximately 1% of the panel mass. Preliminary FEM/BEM modeling shows good agreement with experimental results for radiated sound power.

  4. Damped Windows for Aircraft Interior Noise Control

    NASA Technical Reports Server (NTRS)

    Buehrle, Ralph D.; Klos, Jacob; Gibbs, Gary P.

    2004-01-01

    Windows are a significant path for structure-borne and air-borne noise transmission into aircraft. To improve the acoustical performance, damped windows were fabricated using two or three layers of plexiglas with transparent viscoelastic damping material sandwiched between the layers. In this paper, numerical and experimental results are used to evaluate the acoustic benefits of damped windows. Tests were performed in the Structural Acoustic Loads and Transmission Facility at NASA Langley Research Center to measure the transmission loss for diffuse acoustic excitation and radiated sound power for point force excitation. Comparisons between uniform and damped plexiglas windows showed increased transmission loss of 6 dB at the first natural frequency, 6 dB at coincidence, and 4.5 dB over a 50 to 4k Hz range. Radiated sound power was reduced up to 7 dB at the lower natural frequencies and 3.7 dB over a 1000 Hz bandwidth. Numerical models are presented for the prediction of radiated sound power for point force excitation and transmission loss for diffuse acoustic excitation. Radiated sound power and transmission loss predictions are in good agreement with experimental data. A parametric study is presented that evaluates the optimum configuration of the damped plexiglas windows for reducing the radiated sound power.

  5. Damping by branching: a bioinspiration from trees.

    PubMed

    Theckes, B; Langre, E de; Boutillon, X

    2011-12-01

    Man-made slender structures are known to be sensitive to high levels of vibration due to their flexibility which often cause irreversible damage. In nature, trees repeatedly endure large amplitudes of motion, mostly caused by strong climatic events, yet with minor or no damage in most cases. A new damping mechanism inspired by the architecture of trees is identified here and characterized in the simplest tree-like structure, a Y-shaped branched structure. Through analytical and numerical analyses of a simple two-degree-of-freedom model, branching is shown to be the key ingredient in this protective mechanism that we call damping-by-branching. It originates in the geometrical nonlinearities so that it is specifically efficient to damp out large amplitudes of motion. A more realistic model, using flexible beam approximation, shows that the mechanism is robust. Finally, two bioinspired architectures are analyzed, showing significant levels of damping achieved via branching with typically 30% of the energy being dissipated in one oscillation. This concept of damping-by-branching is of simple practical use in the design of very slender and flexible structures subjected to extreme dynamical loadings.

  6. Anti-damping effect of radiation reaction

    NASA Astrophysics Data System (ADS)

    Wang, G.; Li, H.; Shen, Y. F.; Yuan, X. Z.; Zi, J.

    2010-01-01

    The anti-damping effect of radiation reaction, which means the radiation reaction does non-negative work on a radiating charge, is investigated at length by using the Lorentz-Dirac equation (LDE) for the motion of a point charge respectively acted on by (a) a pure electric field, (b) a pure magnetic field and (c) the fields of an electromagnetic wave. We found that the curvature of the charge's trajectory plays an important role in the radiation reaction force, and the anti-damping effect cannot take place for the real macroscopic motions of a point charge. The condition for this anti-damping effect to take place is that the gradient of the external force field must exceed a certain value over the region of magnitude of the classical radius of massive charges (~10-15 m). Our results are potentially helpful to lessen the controversy on LDE and justify it as the correct classical equation describing the radiating charge's motion. If this anti-damping effect of LDE were a real existing physical process, it could serve as a mechanism within the context of classical electrodynamics for the stability of hydrogen atoms. Using the picture of an electron in quantum electrodynamics, namely the negative bare charge surrounded by the polarized positive charges of vacuum, we can obtain a reasonable explanation for the energy transferred to the electron during the occurrence of the anti-damping effect, on which the venerable work of Wheeler and Feynman has thrown some light.

  7. Accelerated Radiation-Damping for Increased Spin Equilibrium (ARISE)

    PubMed Central

    Huang, Susie Y.; Witzel, Thomas; Wald, Lawrence L.

    2008-01-01

    Control of the longitudinal magnetization in fast gradient echo sequences is an important factor enabling the high efficiency of balanced Steady State Free Precession (bSSFP) sequences. We introduce a new method for accelerating the return of the longitudinal magnetization to the +z-axis that is independent of externally applied RF pulses and shows improved off-resonance performance. The Accelerated Radiation damping for Increased Spin Equilibrium (ARISE) method uses an external feedback circuit to strengthen the Radiation Damping (RD) field. The enhanced RD field rotates the magnetization back to the +z-axis at a rate faster than T1 relaxation. The method is characterized in gradient echo phantom imaging at 3T as a function of feedback gain, phase, and duration and compared with results from numerical simulations of the Bloch equations incorporating RD. A short period of feedback (10ms) during a refocused interval of a crushed gradient echo sequence allowed greater than 99% recovery of the longitudinal magnetization when very little T2 relaxation has time to occur. Appropriate applications might include improving navigated sequences. Unlike conventional flip-back schemes, the ARISE “flip-back” is generated by the spins themselves, thereby offering a potentially useful building block for enhancing gradient echo sequences. PMID:18956463

  8. Passive damping concepts for slender columns in space structures

    NASA Technical Reports Server (NTRS)

    Razzaq, Z.; Ekhelikar, R. K.

    1985-01-01

    An experimental and theoretical study of three different passive damping concepts is conducted for a slender member with partial rotational end restraints. Over a hundred full-scale natural vibration experiments were conducted to evaluate the effectiveness of mass-string, polyethylene tubing, and chain damping concepts. The damping properties obtained from the experiments were used in the approximate analyses based on the partial differential equation of motion for the problem. The comparison of the experimental and the theoretical deflection-time relations shows that the velocity-dependent damping model used in the theory is adequate. From the experimental results, the effect of end connection friction and induced axial forces on damping is identified. The definition of an efficiency index is proposed based on the damping ratio and the mass of a given passive damping device. Using this definition, the efficiencies of the three damping devices are compared. The polyethylene tubing concept resulted into a low damping efficiency.

  9. Turbine blade damping device with controlled loading

    DOEpatents

    Marra, John J.

    2015-09-29

    A damping structure for a turbomachine rotor. The damping structure including an elongated snubber element including a first snubber end rigidly attached to a first blade and extending toward an adjacent second blade, and an opposite second snubber end positioned adjacent to a cooperating surface associated with the second blade. The snubber element has a centerline extending radially inwardly in a direction from the first blade toward the second blade along at least a portion of the snubber element between the first and second snubber ends. Rotational movement of the rotor effects relative movement between the second snubber end and the cooperating surface to position the second snubber end in frictional engagement with the cooperating surface with a predetermined damping force determined by a centrifugal force on the snubber element.

  10. Viscous damping of perforated planar micromechanical structures

    PubMed Central

    Homentcovschi, D.; Miles, R.N.

    2008-01-01

    The paper gives an analytical approximation to the viscous damping coefficient due to the motion of a gas between a pair of closely spaced fluctuating plates in which one of the plates contains a regular system of circular holes. These types of structures are important parts of many microelectromechanical devices realized in MEMS technology as microphones, microaccelerometers, resonators, etc. The pressure satisfies a Reynolds’ type equation with coefficients accounting for all the important effects: compressibility of the gas, inertia and possibly slip of the gas on the plates. An analytical expression for the optimum number of circular holes which assure a minimum value of the total damping coefficient is given. This value realizes an equilibrium between the squeeze-film damping and the viscous resistance of the holes. The paper also provides analytical design formulas to be used in the case of regular circular perforated plates. PMID:19365579

  11. Biomimetic Gradient Polymers with Enhanced Damping Capacities.

    PubMed

    Wang, Dong; Zhang, Huan; Guo, Jing; Cheng, Beichen; Cao, Yuan; Lu, Shengjun; Zhao, Ning; Xu, Jian

    2016-04-01

    Designing gradient structures, mimicking biological materials, such as pummelo peels and tendon, is a promising strategy for developing advanced materials with superior energy damping capacities. Here a facile and effective approach for fabricating polymers with composition gradients at millimeter length scale is presented. The gradient thiol-ene polymers (TEPs) are created by the use of density difference of ternary thiol-ene-ene precursors and the subsequent photo-crosslinking via thiol-ene reaction. The compositional gradients are analyzed via differential scanning calorimeter (DSC), compressive modulus testing, atomic force microscopy (AFM) indentation, and swelling measurements. In contrast to homogeneous TEPs networks, the resultant gradient polymer shows a broader effective damping temperature range combining with good mechanical properties. The present result provides an effective route toward high damping materials by the fabrication of gradient structures.

  12. Highly damped kinematic coupling for precision instruments

    DOEpatents

    Hale, Layton C.; Jensen, Steven A.

    2001-01-01

    A highly damped kinematic coupling for precision instruments. The kinematic coupling provides support while causing essentially no influence to its nature shape, with such influences coming, for example, from manufacturing tolerances, temperature changes, or ground motion. The coupling uses three ball-cone constraints, each combined with a released flexural degree of freedom. This arrangement enables a gain of higher load capacity and stiffness, but can also significantly reduce the friction level in proportion to the ball radius divided by the distance between the ball and the hinge axis. The blade flexures reduces somewhat the stiffness of the coupling and provides an ideal location to apply constrained-layer damping which is accomplished by attaching a viscoelastic layer and a constraining layer on opposite sides of each of the blade flexures. The three identical ball-cone flexures provide a damped coupling mechanism to kinematically support the projection optics system of the extreme ultraviolet lithography (EUVL) system, or other load-sensitive apparatus.

  13. Radiation damping in focusing-dominated systems

    SciTech Connect

    Huang, Zhirong; Chen, Pisin; Ruth, R.D.

    1995-06-01

    A quasi-classical method is developed to calculate the radiation damping of a relativistic particle in a straight, continuous focusing system. In one limiting case where the pitch angle of the particle {theta}{sub p} is much larger than the radiation opening angle 1/{gamma}, the radiation power spectrum is similar to synchrotron radiation and the relative damping rate of the transverse action is proportional to the relative energy loss rate. In the other limiting case where {theta}{sub p} {much_lt} 1/{gamma}, the radiation is dipole in nature and the relative damping rate of the transverse action is energy-independent and is much faster than the relative energy rate. Quantum excitation to the transverse action is absent in this focusing channel. These results can be extended to bent systems provided that the focusing field dominates over the bending field.

  14. Turbine blade damping device with controlled loading

    SciTech Connect

    Marra, John J

    2013-09-24

    A damping structure for a turbomachine rotor. The damping structure including an elongated snubber element including a first snubber end rigidly attached to a first blade and extending toward an adjacent second blade, and an opposite second snubber end positioned adjacent to a cooperating surface associated with the second blade. The snubber element has a centerline extending radially inwardly in a direction from the first blade toward the second blade along at least a portion of the snubber element between the first and second snubber ends. Rotational movement of the rotor effects relative movement between the second snubber end and the cooperating surface to position the second snubber end in frictional engagement with the cooperating surface with a predetermined damping force determined by a centrifugal force on the snubber element.

  15. Measurement of damping of graphite epoxy materials

    NASA Technical Reports Server (NTRS)

    Crocker, M. J.

    1985-01-01

    The design of an experiment to measure the damping of a cylindrical graphite-epoxy specimen with a three point support and a knife edge support is described as well as equipment used in tests conducted to determine the influence of the support at the two ends of the specimen and to simulate an idealized free-free boundary condition at the two edges. A curve fitting technique is being used to process the frequency response data obtained. Experiments conducted on the thin plate specimen also reveal the influence of the end support condition on the damping ratio of the specimen. The damping ratio values measured for both specimens appear to be strongly influenced by the shape of the specimen and appear to depend on length and fiber orientation as well as the presence of discontinuities such as sharp bends, corners, and notches.

  16. Ponderomotive scaling in the radiative damping regime

    NASA Astrophysics Data System (ADS)

    Pandit, Rishi R.; Ackad, Edward; d'Humieres, Emmanuel; Sentoku, Yasuhiko

    2017-10-01

    The ponderomotive force for super intense laser matter interactions has been derived by taking into account the higher order terms of radiative damping. The ion acceleration via collisionless shock, generated by both the ponderomotive pressure of the intense laser pulse during the interaction and the electron acceleration, becomes less efficient due to the radiative damping. A new ponderomotive scaling has been derived by applying the force with the radiation reaction to the super intense laser regime, and it is benchmarked by a particle-in-cell simulation with the radiative damping terms included in equations of motion. We find good agreement between theoretical and simulation results in terms of shock velocity and accelerated ion energy.

  17. Damping properties of plasmonic waves on graphene

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2017-07-01

    By considering the friction force due to the interaction of plasmonic waves and graphene lattice, the damping properties (lifetime and propagation length) of long-wavelength plasmonic waves on a monolayer graphene are studied by means of a perturbative method. Electronic excitations on the graphene surface are modeled by an infinitesimally thin layer of massless electron gas, which is described by means of the linearized hydrodynamic theory. The analytical expressions for the frequency dependence of damping function, the propagation length and the lifetime of long-wavelength surface waves on graphene with small intrinsic damping are derived and analyzed. Also, simple expressions for the stored and dissipated energy densities of the surface waves are presented.

  18. Damped electrostatic structures in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Hussain, S.; Akhtar, N.

    2017-06-01

    In this work, we study the damped nonlinear solitary wave structures in electron ion dense collisional plasmas in the presence of exchange correlation potential. Due to high density and low temperature, these plasmas are considered as quantum plasmas. The quantum mechanical effects due to quantum statistical pressure, quantum tunnelling, and exchange correlation due to 1/2 spin of Fermions are included in a quantum hydrodynamic model. The collisions of plasmas particles with neutrals are taken into account to derive the Damped Korteweg-de Vries equation. A reductive perturbation technique is performed to study nonlinearities and dispersive effects in the plasma system. The comparative importance of the potential due to the degenerate pressure, exchange correlation potential, and the Bohm potential in the linear and nonlinear dispersion is presented. The effects of variations of different plasma parameters on propagation characteristics of damped oscillations in the context of astrophysical objects like neutron stars/pulsar are discussed.

  19. Fluid damping of cylindrical liquid storage tanks.

    PubMed

    Habenberger, Joerg

    2015-01-01

    A method is proposed in order to calculate the damping effects of viscous fluids in liquid storage tanks subjected to earthquakes. The potential equation of an ideal fluid can satisfy only the boundary conditions normal to the surface of the liquid. To satisfy also the tangential interaction conditions between liquid and tank wall and tank bottom, the potential flow is superimposed by a one-dimensional shear flow. The shear flow in this boundary layer yields to a decrease of the mechanical energy of the shell-liquid-system. A damping factor is derived from the mean value of the energy dissipation in time. Depending on shell geometry and fluid viscosity, modal damping ratios are calculated for the convective component.

  20. Passively damped vibration welding system and method

    DOEpatents

    Tan, Chin-An; Kang, Bongsu; Cai, Wayne W.; Wu, Tao

    2013-04-02

    A vibration welding system includes a controller, welding horn, an anvil, and a passive damping mechanism (PDM). The controller generates an input signal having a calibrated frequency. The horn vibrates in a desirable first direction at the calibrated frequency in response to the input signal to form a weld in a work piece. The PDM is positioned with respect to the system, and substantially damps or attenuates vibration in an undesirable second direction. A method includes connecting the PDM having calibrated properties and a natural frequency to an anvil of an ultrasonic welding system. Then, an input signal is generated using a weld controller. The method includes vibrating a welding horn in a desirable direction in response to the input signal, and passively damping vibration in an undesirable direction using the PDM.

  1. Assessing Equivalent Viscous Damping Using Piping System test Results

    SciTech Connect

    Nie, J.; Morante, R.

    2010-07-18

    The specification of damping for nuclear piping systems subject to seismic-induced motions has been the subject of many studies and much controversy. Damping estimation based on test data can be influenced by numerous factors, consequently leading to considerable scatter in damping estimates in the literature. At present, nuclear industry recommendations and nuclear regulatory guidance are not consistent on the treatment of damping for analysis of nuclear piping systems. Therefore, there is still a need to develop a more complete and consistent technical basis for specification of appropriate damping values for use in design and analysis. This paper summarizes the results of recent damping studies conducted at Brookhaven National Laboratory.

  2. Optimal piezoelectric switching technique for vibration damping

    NASA Astrophysics Data System (ADS)

    Neubauer, Marcus; Oleskiewicz, Robert

    2007-04-01

    This paper describes piezoelectric switching techniques for vibration damping. The dynamical behaviour of a piezoceramics connected to a switching LR shunt and the dissipated energy are obtained using a fundamental piezoelectric model. All calculations are performed in a normalized way and highlight the influence of the electromechanical coupling coefficient of the piezoceramics and the shunt parameters. For the first time, a precise result for the dynamics of a shunted piezoceramics is derived. The analytic results are used to determine the optimal switching sequence and external branch parameters in order to maximize the damping performance. The results are validated by measurements of a clamped beam.

  3. Wind turbine blade with viscoelastic damping

    DOEpatents

    Sievers, Ryan A.; Mullings, Justin L.

    2017-01-10

    A wind turbine blade (60) damped by viscoelastic material (54, 54A-F) sandwiched between stiffer load-bearing sublayers (52A, 52B, 56A, 56B) in portions of the blade effective to damp oscillations (38) of the blade. The viscoelastic material may be located in one or more of: a forward portion (54A) of the shell, an aft portion (54D) of the shell, pressure and suction side end caps (54B) of an internal spar, internal webbing walls (54C, 54E), and a trailing edge core (54F).

  4. Particle systems and nonlinear Landau damping

    SciTech Connect

    Villani, Cédric

    2014-03-15

    Some works dealing with the long-time behavior of interacting particle systems are reviewed and put into perspective, with focus on the classical Kolmogorov–Arnold–Moser theory and recent results of Landau damping in the nonlinear perturbative regime, obtained in collaboration with Clément Mouhot. Analogies are discussed, as well as new qualitative insights in the theory. Finally, the connection with a more recent work on the inviscid Landau damping near the Couette shear flow, by Bedrossian and Masmoudi, is briefly discussed.

  5. Inertia-Wheel Vibration-Damping System

    NASA Technical Reports Server (NTRS)

    Fedor, Joseph V.

    1990-01-01

    Proposed electromechanical system would damp vibrations in large, flexible structure. In active vibration-damping system motors and reaction wheels at tips of appendages apply reaction torques in response to signals from accelerometers. Velocity signal for vibrations about one axis processes into control signal to oppose each of n vibrational modes. Various modes suppressed one at a time. Intended primarily for use in spacecraft that has large, flexible solar panels and science-instrument truss assembly, embodies principle of control interesting in its own right and adaptable to terrestrial structures, vehicles, and instrument platforms.

  6. Damping Goes the Distance in Golf

    NASA Technical Reports Server (NTRS)

    2004-01-01

    In the late 1980s, Dr. Benjamin Dolgin of NASA s Jet Propulsion Laboratory developed a concept for a high-damping graphite/viscoelastic material for the Strategic Defense Initiative (popularly referred to as "Star Wars"), as part of a space-based laser anti-missile program called "Asterix." Dolgin drummed up this concept with the intention of stabilizing weapons launch platforms in space, where there is no solid ground to firmly support these structures. Without the inclusion of high-damping material, the orbital platforms were said to vibrate for 20 minutes after force was applied - a rate deemed "unacceptable" by leaders of the Strategic Defense Initiative.

  7. Inertia-Wheel Vibration-Damping System

    NASA Technical Reports Server (NTRS)

    Fedor, Joseph V.

    1990-01-01

    Proposed electromechanical system would damp vibrations in large, flexible structure. In active vibration-damping system motors and reaction wheels at tips of appendages apply reaction torques in response to signals from accelerometers. Velocity signal for vibrations about one axis processes into control signal to oppose each of n vibrational modes. Various modes suppressed one at a time. Intended primarily for use in spacecraft that has large, flexible solar panels and science-instrument truss assembly, embodies principle of control interesting in its own right and adaptable to terrestrial structures, vehicles, and instrument platforms.

  8. Lag-stabilized force feedback damping

    SciTech Connect

    Petterson, B.J.; Robinett, R.D.; Werner, J.C.

    1991-05-01

    A lag-stabilized, force feedback controller for damping initial and residual oscillations of a planar, cantilevered flexible arm has been analytically developed and experimentally implemented on a commercial robot. The controller feeds back force sensor measurements that are delayed in time and proportional to the displacement (angular orientation) of the arm in order to damp the oscillation. As a result of the lag (contrary to popular belief), the controlled robot system is stable and provides tunable performance on a Cincinnati Milacron T3-786 robot. 3 refs., 9 figs., 2 tabs.

  9. Delay of Transition Using Forced Damping

    NASA Technical Reports Server (NTRS)

    Exton, Reginald J.

    2014-01-01

    Several experiments which have reported a delay of transition are analyzed in terms of the frequencies of the induced disturbances generated by different flow control elements. Two of the experiments employed passive stabilizers in the boundary layer, one leading-edge bluntness, and one employed an active spark discharge in the boundary layer. It is found that the frequencies generated by the various elements lie in the damping region of the associated stability curve. It is concluded that the creation of strong disturbances in the damping region stabilizes the boundary-layer and delays the transition from laminar to turbulent flow.

  10. Mechanical Design of the DAMPE BGO Calorimeter

    NASA Astrophysics Data System (ADS)

    Hu, Yiming; Wu, Jian; Feng, Changqing; Zhang, Yunlong; Chen, Dengyi; Chang, Jin

    The Dark Matter Particle Explorer, DAMPE, is a new designed satellite developed for the CASs new Innovation 2020 program. As the main component of DAMPE, the new designed BGO calorimeter consists of 308 BGO Crystals coupled with photomultiplier tube.The reliability and safety of the BGO Calorimeter structure play a very important role in the operation of whole detector. During the rocket launch, the calorimeter structure should be stable against vibration and environmental factors to ensure detector works in good conditions. In this article, we make the BGO calorimeter structure design, and then prove that it will work in the environments of rocket launch and flight.

  11. Building characteristics associated with moisture related problems in 8,918 Swedish dwellings.

    PubMed

    Hägerhed-Engman, Linda; Bornehag, Carl-Gustaf; Sundell, Jan

    2009-08-01

    Moisture problems in buildings have in a number of studies been shown to increase the risk for respiratory symptoms. The study Dampness in Buildings and Health (DBH) was initiated with the aim to identify health relevant exposures related to dampness in buildings. A questionnaire study about home environment with a focus on dampness problems and health was conducted in one county of Sweden (8,918 homes, response rate 79%). Building characteristics that were associated with one or more of the dampness indicators were for single-family houses, older houses, flat-roofed houses built in the 1960s and 1970s, houses with a concrete slab on the ground that were built before 1983. Moreover, tenancy and earlier renovation due to mould or moisture problems was strongly associated with dampness. A perception of dry air was associated with window-pane condensation, e.g. humid indoor air.

  12. Identification of mold and dampness-associated respiratory morbidity in 2 schools: comparison of questionnaire survey responses to national data.

    PubMed

    Sahakian, Nancy M; White, Sandra K; Park, Ju-Hyeong; Cox-Ganser, Jean M; Kreiss, Kathleen

    2008-01-01

    Dampness and mold problems are frequently encountered in schools. Approximately one third of US public schools require extensive repairs or need at least 1 building replaced. This study illustrates how national data can be used to identify building-related health risks in school employees and students. School employees (n = 309) in 2 elementary schools (schools A and B) with dampness and mold problems completed standardized questionnaires. Responses were compared with participant responses from the 3rd National Health and Nutrition Examination Survey and were indirectly standardized for gender, age, smoking status, and (for school B) race. Uncontrolled comparisons were made to responses from a study of office workers, as well as between responses from school employees in different sections of the school buildings designated by decade of construction. Employees from both schools had excess work-related throat and lower respiratory symptoms, as well as eye, nasal, sinus, and wheezing symptoms. School B employees also had excess physician-diagnosed asthma and work-related fatigue, headache, and skin irritation. Employees in sections of the school buildings that were categorized as having greater dampness and mold contamination had more frequent upper and lower respiratory symptoms than employees working in other building sections. This noncostly type of analysis of indoor air quality complaints can be used to motivate and prioritize building remediation in public schools where funds for building remediation are usually limited.

  13. Damping of the wrist joint during voluntary movement.

    PubMed

    Milner, T E; Cloutier, C

    1998-10-01

    Damping characteristics of the musculoskeletal system were investigated during rapid voluntary wrist flexion movements. Oscillations about the final position were induced by introducing a load with the characteristics of negative damping, which artificially reduced the damping of the wrist. Subjects responded to increases in the negatively damped load by stronger cocontraction of wrist flexor and extensor muscles during the stabilization phase of the movement. However, their ability to counteract the effects of the negatively damped load diminished as the negative damping increased. Consequently, the number and frequency of oscillations increased. The oscillations were accompanied by phase-locked muscle activity superimposed on underlying tonic muscle activation. The wrist stiffness and damping coefficient increased with the increased cocontraction that accompanied more negatively damped loads, although changes in the damping coefficient were less systematic than the stiffness. Analysis of successive half-cycles of the oscillation revealed that the wrist stiffness and damping coefficient increased, despite decreasing muscle activation, as oscillation amplitude and velocity declined. This indicates that the inverse dependence of the damping coefficient on oscillation velocity contributes significantly to damping of joint motion. It is suggested that this property helps to offset a negative contribution to damping from the stretch reflex.

  14. The DAMPE silicon-tungsten tracker

    NASA Astrophysics Data System (ADS)

    Azzarello, P.; Ambrosi, G.; Asfandiyarov, R.; Bernardini, P.; Bertucci, B.; Bolognini, A.; Cadoux, F.; Caprai, M.; De Mitri, I.; Domenjoz, M.; Dong, Y.; Duranti, M.; Fan, R.; Fusco, P.; Gallo, V.; Gargano, F.; Gong, K.; Guo, D.; Husi, C.; Ionica, M.; La Marra, D.; Loparco, F.; Marsella, G.; Mazziotta, M. N.; Mesa, J.; Nardinocchi, A.; Nicola, L.; Pelleriti, G.; Peng, W.; Pohl, M.; Postolache, V.; Qiao, R.; Surdo, A.; Tykhonov, A.; Vitillo, S.; Wang, H.; Weber, M.; Wu, D.; Wu, X.; Zhang, F.

    2016-09-01

    The DArk Matter Particle Explorer (DAMPE) is a spaceborne astroparticle physics experiment, launched on 17 December 2015. DAMPE will identify possible dark matter signatures by detecting electrons and photons in the 5 GeV-10 TeV energy range. It will also measure the flux of nuclei up to 100 TeV, for the study of the high energy cosmic ray origin and propagation mechanisms. DAMPE is composed of four sub-detectors: a plastic strip scintillator, a silicon-tungsten tracker-converter (STK), a BGO imaging calorimeter and a neutron detector. The STK is composed of six tracking planes of 2 orthogonal layers of single-sided micro-strip detectors, for a total detector surface of ca. 7 m2. The STK has been extensively tested for space qualification. Also, numerous beam tests at CERN have been done to study particle detection at silicon module level, and at full detector level. After description of the DAMPE payload and its scientific mission, we will describe the STK characteristics and assembly. We will then focus on some results of single ladder performance tests done with particle beams at CERN.

  15. Damping of liquid sloshing by foams

    NASA Astrophysics Data System (ADS)

    Sauret, A.; Boulogne, F.; Cappello, J.; Dressaire, E.; Stone, H. A.

    2015-02-01

    When a container is set in motion, the free surface of the liquid starts to oscillate or slosh. Such effects can be observed when a glass of water is handled carelessly and the fluid sloshes or even spills over the rims of the container. However, beer does not slosh as readily as water, which suggests that foam could be used to damp sloshing. In this work, we study experimentally the effect on sloshing of a liquid foam placed on top of a liquid bath. We generate a monodisperse two-dimensional liquid foam in a rectangular container and track the motion of the foam. The influence of the foam on the sloshing dynamics is experimentally characterized: only a few layers of bubbles are sufficient to significantly damp the oscillations. We rationalize our experimental findings with a model that describes the foam contribution to the damping coefficient through viscous dissipation on the walls of the container. Then we extend our study to confined three-dimensional liquid foam and observe that the behavior of 2D and confined 3D systems are very similar. Thus, we conclude that only the bubbles close to the walls have a significant impact on the dissipation of energy. The possibility to damp liquid sloshing using foam is promising in numerous industrial applications such as the transport of liquefied gas in tankers or for propellants in rocket engines.

  16. Active Damping Using Distributed Anisotropic Actuators

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Cabell, Randolph H.; Quinones, Juan D.; Wier, Nathan C.

    2010-01-01

    A helicopter structure experiences substantial high-frequency mechanical excitation from powertrain components such as gearboxes and drive shafts. The resulting structure-borne vibration excites the windows which then radiate sound into the passenger cabin. In many cases the radiated sound power can be reduced by adding damping. This can be accomplished using passive or active approaches. Passive treatments such as constrained layer damping tend to reduce window transparency. Therefore this paper focuses on an active approach utilizing compact decentralized control units distributed around the perimeter of the window. Each control unit consists of a triangularly shaped piezoelectric actuator, a miniature accelerometer, and analog electronics. Earlier work has shown that this type of system can increase damping up to approximately 1 kHz. However at higher frequencies the mismatch between the distributed actuator and the point sensor caused control spillover. This paper describes new anisotropic actuators that can be used to improve the bandwidth of the control system. The anisotropic actuators are composed of piezoelectric material sandwiched between interdigitated electrodes, which enables the application of the electric field in a preferred in-plane direction. When shaped correctly the anisotropic actuators outperform traditional isotropic actuators by reducing the mismatch between the distributed actuator and point sensor at high frequencies. Testing performed on a Plexiglas panel, representative of a helicopter window, shows that the control units can increase damping at low frequencies. However high frequency performance was still limited due to the flexible boundary conditions present on the test structure.

  17. Vibration damping for the Segmented Mirror Telescope

    NASA Astrophysics Data System (ADS)

    Maly, Joseph R.; Yingling, Adam J.; Griffin, Steven F.; Agrawal, Brij N.; Cobb, Richard G.; Chambers, Trevor S.

    2012-09-01

    The Segmented Mirror Telescope (SMT) at the Naval Postgraduate School (NPS) in Monterey is a next-generation deployable telescope, featuring a 3-meter 6-segment primary mirror and advanced wavefront sensing and correction capabilities. In its stowed configuration, the SMT primary mirror segments collapse into a small volume; once on location, these segments open to the full 3-meter diameter. The segments must be very accurately aligned after deployment and the segment surfaces are actively controlled using numerous small, embedded actuators. The SMT employs a passive damping system to complement the actuators and mitigate the effects of low-frequency (<40 Hz) vibration modes of the primary mirror segments. Each of the six segments has three or more modes in this bandwidth, and resonant vibration excited by acoustics or small disturbances on the structure can result in phase mismatches between adjacent segments thereby degrading image quality. The damping system consists of two tuned mass dampers (TMDs) for each of the mirror segments. An adjustable TMD with passive magnetic damping was selected to minimize sensitivity to changes in temperature; both frequency and damping characteristics can be tuned for optimal vibration mitigation. Modal testing was performed with a laser vibrometry system to characterize the SMT segments with and without the TMDs. Objectives of this test were to determine operating deflection shapes of the mirror and to quantify segment edge displacements; relative alignment of λ/4 or better was desired. The TMDs attenuated the vibration amplitudes by 80% and reduced adjacent segment phase mismatches to acceptable levels.

  18. The DAMPE experiment: first data from space

    NASA Astrophysics Data System (ADS)

    De Mitri, Ivan

    2017-03-01

    The DAMPE satellite has been successfully launched in orbit on December 2015. The science goals of the mission include the study of high energy cosmic ray electrons, photons, protons and nuclei in a wide energy range: 109 - 1014 eV. A report on the mission status will be presented, together with on-orbit detector performance and first data coming from space.

  19. Scattering Theory of Mesoscopic Gilbert Damping

    NASA Astrophysics Data System (ADS)

    Brataas, Arne

    2010-03-01

    Magnetic damping determines the performance of magnetic devices including high-frequency oscillators, hard drives, magnetic random access memories, magnetic logic devices, and magnetic field sensors. The drive to improve these devices, to reduce the response time of sensors and the physical dimensions has led to a greater focus on studying the friction force a changing magnetization experiences. We study the magnetization dynamics of single domain ferromagnets and domain walls in contact with a thermal bath by scattering theory. We recover the Landau-Lifshitz-Gilbert equation and express the Gilbert damping tensor in terms of the scattering matrix [1,2]. Dissipation of magnetic energy equals energy current pumped out of the system by the time-dependent magnetization, with separable spin-relaxation induced bulk and spin-pumping generated interface contributions [3]. The scattering theory of Gilbert damping is suitable for first-principles calculations that include disorder and spin-orbit coupling on an equal footing [4]. In linear response, our scattering theory for the Gilbert damping tensor is equivalent with the Kubo formalism. [4pt] [1] A. Brataas, Y. Tserkovnyak, and G. E. W. Bauer, Phys. Rev. Lett. 101, 037207 (2008). [0pt] [2] K. M. D. Hals, A. K. Nguyen, and A. Brataas, Phys. Rev. Lett. 102, 256601 (2009). [0pt] [3] Y. Tserkovnyak, A. Brataas, G. E. W. Bauer, and B. I. Halperin, Rev. Mod. Phys. 77, 1375 (2005). [0pt] [4] A. A. Starikov, P. J. Kelly, A. Brataas, Y. Tserkovnyak, and G. E. W. Bauer, unpublished.

  20. Active damping in a flexible manipulator

    NASA Technical Reports Server (NTRS)

    Pham, Trung T.

    1990-01-01

    Viewgraphs on active damping in a flexible manipulator are presented. Topics covered include: Shuttle Remote Manipulator System (SRMS); flexible structures; vibration; modeling of a flexible manipulator dynamical structure; designing control law criterion that minimizes vibration; and candidate application of fuzzy logic control law to the problem.

  1. The Stochastic Nonlinear Damped Wave Equation

    SciTech Connect

    Barbu, V. Da Prato, G.

    2002-12-19

    We prove the existence of an invariant measure for the transition semigroup associated with a nonlinear damped stochastic wave equation in R{sup n} of the Klein-Gordon type. The uniqueness of the invariant measure and the structure of the corresponding Kolmogorov operator are also studied.

  2. Active damping of spacecraft structural appendage vibrations

    NASA Technical Reports Server (NTRS)

    Fedor, Joseph V. (Inventor)

    1990-01-01

    An active vibration damper system, for bending in two orthogonal directions and torsion, in each of three mutually perpendicular axes is located at the extremities of the flexible appendages of a space platform. The system components for each axis includes: an accelerometer, filtering and signal processing apparatus, and a DC motor-inertia wheel torquer. The motor torquer, when driven by a voltage proportional to the relative vibration tip velocity, produces a reaction torque for opposing and therefore damping a specific modal velocity of vibration. The relative tip velocity is obtained by integrating the difference between the signal output from the accelerometer located at the end of the appendage with the output of a usually carried accelerometer located on a relatively rigid body portion of the space platform. A selector switch, with sequential stepping logic or highest modal vibration energy logic, steps to another modal tip velocity channel and receives a signal voltage to damp another vibration mode. In this manner, several vibration modes can be damped with a single sensor/actuator pair. When a three axis damper is located on each of the major appendages of the platform, then all of the system vibration modes can be effectively damped.

  3. Effectiveness and Predictability of Particle Damping

    DTIC Science & Technology

    2000-01-01

    Conference Monterey, California, February 9-11, 1999. 20. Kielb, R., et al., “Advanced Damping Systems for Fan and Compressor Blisks ”, Proceedings of the 4tjh...for applications where high centrifugal loads exist such as the fan , compressor and turbines of aircraft engines. In these applications current

  4. Gilbert damping in binary magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Barati, E.; Cinal, M.

    2017-04-01

    We present quantum mechanical calculations of the Gilbert damping constant α in ultrathin L1 0 [Co/NM ] N superlattices and (001) fcc [Co/NM ] N magnetic multilayers built of cobalt and nonmagnetic metals NM = Cu, Ag, Pd, Pt, and Au. The calculations are performed within a realistic nine-orbital tight-binding model of the band structure including spin-orbit interaction. The dependence of α on the stacking number N , ferromagnetic and nonmagnetic layer thicknesses as well as the electron scattering rate is investigated. The damping constant is shown to be the sum of a constant term (bulklike) and a 1 /N term (due to external surfaces) which arise from inter- and intraband electronic transitions, respectively. The calculated α is found to be enhanced in the considered multilayers in comparison with its values for bulk Co and their bilayer counterparts with the same total Co thickness. The origin of this enhancement and the variation of α with the geometric structure of the multilayers are further investigated by analyzing the damping contributions from individual atomic layers. The obtained theoretical results for the damping constant are shown to be in good agreement with previous experimental observations in magnetic multilayers. In particular, the experimentally observed linear dependence on the ratio of NM (Pd or Pt) and Co layer thicknesses is reproduced in the present calculations.

  5. Nonlinear Landau damping and Alfven wave dissipation

    NASA Technical Reports Server (NTRS)

    Vinas, Adolfo F.; Miller, James A.

    1995-01-01

    Nonlinear Landau damping has been often suggested to be the cause of the dissipation of Alfven waves in the solar wind as well as the mechanism for ion heating and selective preacceleration in solar flares. We discuss the viability of these processes in light of our theoretical and numerical results. We present one-dimensional hybrid plasma simulations of the nonlinear Landau damping of parallel Alfven waves. In this scenario, two Alfven waves nonresonantly combine to create second-order magnetic field pressure gradients, which then drive density fluctuations, which in turn drive a second-order longitudinal electric field. Under certain conditions, this electric field strongly interacts with the ambient ions via the Landau resonance which leads to a rapid dissipation of the Alfven wave energy. While there is a net flux of energy from the waves to the ions, one of the Alfven waves will grow if both have the same polarization. We compare damping and growth rates from plasma simulations with those predicted by Lee and Volk (1973), and also discuss the evolution of the ambient ion distribution. We then consider this nonlinear interaction in the presence of a spectrum of Alfven waves, and discuss the spectrum's influence on the growth or damping of a single wave. We also discuss the implications for wave dissipation and ion heating in the solar wind.

  6. Landau damping in the SLAC linac

    SciTech Connect

    Bane, K.L.F.

    1985-04-01

    In the SLC Landau damping can greatly stabilize the beam against changes in injection conditions into the linac. For example, by choosing phi/sub a/ = -15/sup 0/, n/sub a/ = 51, the jitter tolerances for 25% emittance growth can be relaxed by greater than a factor of 10, while sacrificing 1.6 GeV in final energy. Increasing the focusing, especially near the beginning of the linac, will lessen the energy penalty for a given amount of stability. For example, with the planned addition of more quads in sectors 2-4 the stability of the above example can be achieved at the cost of only 1.0 GeV in final energy. The simulations including machine errors indicate that the static residual emittance growth can be kept consistently below 30% with Landau damping, but that this would be difficult to achieve without Landau damping. It can be supposed that Landau damping will also stabilize the beam to magnet jitter, though a more thorough study of machine error effects still needs to be done. 9 refs., 4 figs., 1 tab.

  7. Chiral damping of magnetic domain walls.

    PubMed

    Jué, Emilie; Safeer, C K; Drouard, Marc; Lopez, Alexandre; Balint, Paul; Buda-Prejbeanu, Liliana; Boulle, Olivier; Auffret, Stephane; Schuhl, Alain; Manchon, Aurelien; Miron, Ioan Mihai; Gaudin, Gilles

    2016-03-01

    Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics, current-induced spin-orbit torques and some topological magnetic structures. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii-Moriya interaction (DMI) exhibit identical spatial symmetry. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. ).

  8. Apparatus and method of preloading vibration-damping bellows

    DOEpatents

    Cutburth, Ronald W.

    1988-01-01

    An improved vibration damping bellows mount or interconnection is disclosed. In one aspect, the bellows is compressively prestressed along its length to offset vacuum-generated tensile loads and thereby improve vibration damping characteristics.

  9. Experimental determination of material damping using vibration analyzer

    NASA Technical Reports Server (NTRS)

    Chowdhury, Mostafiz R.; Chowdhury, Farida

    1990-01-01

    Structural damping is an important dynamic characteristic of engineering materials that helps to damp vibrations by reducing their amplitudes. In this investigation, an experimental method is illustrated to determine the damping characteristics of engineering materials using a dual channel Fast Fourier Transform (FFT) analyzer. A portable Compaq III computer which houses the analyzer, is used to collect the dynamic responses of three metal rods. Time-domain information is analyzed to obtain the logarithmic decrement of their damping. The damping coefficients are then compared to determine the variation of damping from material to material. The variations of damping from one point to another of the same material, due to a fixed point excitation, and the variable damping at a fixed point due to excitation at different points, are also demonstrated.

  10. Resistor-damped electromechanical lever blocks

    NASA Astrophysics Data System (ADS)

    Zago, Lorenzo; Genequand, Pierre M.; Kjelberg, Ivar

    1998-06-01

    The paper presents an innovative technical solution which provides a combined damping and isolation interface with the appropriate transmissibility characteristics between a vibrating base and a sensitive payload, typically an optical terminal/telescope. The novelty of the solution is primarily found in the implementation of uncoupling and magnification of the incurred vibrations by means of flexures combined with the implementation of energy dissipation by means of a linear electro-magnetic actuator to constitute a passive integrated resistor-damped electromechanic lever block. By means of frictionless flexible lever systems, the amplitude of the payload vibrations is adapted to the optimal range of the actuator with a magnification by a factor ranging typically between 10 and 30. Passive viscous damping is obtained by simply short-circuiting the electro-magnetic motor and can be adapted by setting the impedance of the shorting connection. The desired stiffness is provided by the passive springs of the elastic motor suspension and by the stiffness of the lever flexure blades. The mobile mass of the motors also provide a reaction mass which, like damping and stiffness, is amplified by the square of the lever factor. A theoretical model of resistor-damped electromechanical lever blocks has been established. A particular property is it the good attenuation of excited vibrations only over a set frequency range. Above this range the interface properties rejoin the ones of a rigid connection. This performance makes this type of isolators particularly suitable for integration into multi-layer vibration control systems where sensitive equipment is protected by a mix of passive and active damping/isolation devices acting optimally at different frequency ranges. Experiments performed with a dummy load (80 Kg) representative of a satellite based optical terminal demonstrated the efficiency of the system in protecting the payload by passive damping for vibration excitations

  11. Nonlinear damping and quasi-linear modelling.

    PubMed

    Elliott, S J; Ghandchi Tehrani, M; Langley, R S

    2015-09-28

    The mechanism of energy dissipation in mechanical systems is often nonlinear. Even though there may be other forms of nonlinearity in the dynamics, nonlinear damping is the dominant source of nonlinearity in a number of practical systems. The analysis of such systems is simplified by the fact that they show no jump or bifurcation behaviour, and indeed can often be well represented by an equivalent linear system, whose damping parameters depend on the form and amplitude of the excitation, in a 'quasi-linear' model. The diverse sources of nonlinear damping are first reviewed in this paper, before some example systems are analysed, initially for sinusoidal and then for random excitation. For simplicity, it is assumed that the system is stable and that the nonlinear damping force depends on the nth power of the velocity. For sinusoidal excitation, it is shown that the response is often also almost sinusoidal, and methods for calculating the amplitude are described based on the harmonic balance method, which is closely related to the describing function method used in control engineering. For random excitation, several methods of analysis are shown to be equivalent. In general, iterative methods need to be used to calculate the equivalent linear damper, since its value depends on the system's response, which itself depends on the value of the equivalent linear damper. The power dissipation of the equivalent linear damper, for both sinusoidal and random cases, matches that dissipated by the nonlinear damper, providing both a firm theoretical basis for this modelling approach and clear physical insight. Finally, practical examples of nonlinear damping are discussed: in microspeakers, vibration isolation, energy harvesting and the mechanical response of the cochlea.

  12. Identification and evaluation of linear damping models in beam vibrations

    NASA Technical Reports Server (NTRS)

    Boers, B. L.; Rosenberg, G. S.; Wambsganss, M. W., Jr.

    1969-01-01

    Sensitive method, identifying effective damping mechanisms, involves comparing experimentally determined ratio of first to second mode magnification factors related to common point on beam. Cluster size has little effect on frequencies of elements, magnification factor decreases with cluster size, and viscous and stress damping are dominant damping mechanisms.

  13. Estimation of Boltzmann damping coefficients in beam models

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Fabiano, R. H.; Wang, Y.

    1988-01-01

    A distributed parameter model of a flexible structure with Boltzmann type viscoelastic damping is discussed. A computational method for the estimation of the damping parameters is developed, and theoretical convergence results are given. An example is presented in which actual experimental data is used, demonstrating the efficacy of the computational method and the plausibility of the model for predicting response in damped structures.

  14. Passive damping concepts for slender columns in space structures

    NASA Technical Reports Server (NTRS)

    Razzaq, Z.

    1985-01-01

    Research into the identification of potential passive damping concepts for use in very slender structural members was continued. The following damping concepts are under investigation: mass-string dampers; bright zinc chain; polyethylene tubing; external viscoelastic tape; brushes for electrostatic and frictional damping; suspended chambers with oil and discs; and hybrid concepts. Each of these concepts are briefly discussed.

  15. Damping and induced damping of a lightweight sandwich panel with simple and complex attachments

    NASA Astrophysics Data System (ADS)

    Conlon, S. C.; Hambric, S. A.

    2009-05-01

    Accurately estimating a structure's broadband response is highly dependent on a proper characterization of the system's internal damping as well as induced (or effective) damping when coupled systems are considered. In many aerospace and related applications a primary or master structure is loaded with equipment or substructures. The effects of these attachments on the master structure are often poorly understood and frequently overlooked, but in many cases can dominate the master structure's response. In this work various measures of damping of a lightweight aerospace panel (aluminum sandwich honeycomb core panel) with simple (lumped mass) and complex (electronic equipment) attachments are investigated using experimental techniques and simple statistical energy analysis models. The panel's various measures of damping in steady-state conditions are defined and explored. The panels with simple and complex attachments are experimentally evaluated using power injection methods. The results show that at different frequencies the simple panel's response is controlled by internal and then acoustic radiation damping. The complex attachment's induced damping effects, however, can far exceed both the structure internal and acoustic radiation components. A range of complex attachment configurations are evaluated and general design assessment procedures developed for use by designers. Future work is planned to explore the systems transient response and derived parameters, as well as investigate the effects when the attachment mass varies over a greater range of values, a realistic condition applicable to many aerospace systems.

  16. Damped and zero-damped quasinormal modes of charged, nearly extremal black holes

    NASA Astrophysics Data System (ADS)

    Zimmerman, Aaron; Mark, Zachary

    2016-02-01

    Despite recent progress, the complete understanding of the perturbations of charged, rotating black holes as described by the Kerr-Newman metric remains an open and fundamental problem in relativity. In this study, we explore the existence of families of quasinormal modes of Kerr-Newman black holes whose decay rates limit to zero at extremality, called zero-damped modes in past studies. We review the nearly extremal and WKB approximation methods for spin-weighted scalar fields (governed by the Dudley-Finley equation) and give an accounting of the regimes where scalar zero-damped and damped modes exist. Using Leaver's continued fraction method, we verify that these approximations give accurate predictions for the frequencies in their regimes of validity. In the nonrotating limit, we argue that gravito-electromagnetic perturbations of nearly extremal Reissner-Nordström black holes have zero-damped modes in addition to the well-known spectrum of damped modes. We provide an analytic formula for the frequencies of these modes, verify their existence using a numerical search, and demonstrate the accuracy of our formula. These results, along with recent numerical studies, point to the existence of a simple universal equation for the frequencies of zero-damped gravito-electromagnetic modes of Kerr-Newman black holes, whose precise form remains an open question.

  17. Effects of radiation damping for biomolecular NMR experiments in solution: a hemisphere concept for water suppression.

    PubMed

    Ishima, Rieko

    2015-09-01

    Abundant solvent nuclear spins, such as water protons in aqueous solution, cause radiation damping in NMR experiments. It is important to know how the effect of radiation damping appears in high-resolution protein NMR because macromolecular studies always require very high magnetic field strengths with a highly sensitive NMR probe that can easily cause radiation damping. Here, we show the behavior of water magnetization after a pulsed-field gradient (PFG) using nutation experiments at 900 MHz with a cryogenic probe: when water magnetization is located in the upper hemisphere (having +Z component, parallel to the external magnetic field), dephasing of the magnetization by a PFG effectively suppresses residual water magnetization in the transverse plane. In contrast, when magnetization is located in the lower hemisphere (having -Z component), the small residual transverse component remaining after a PFG is still sufficient to induce radiation damping. Based on this observation, we designed (1)H-(15)N HSQC experiments in which water magnetization is maintained in the upper hemisphere, but not necessarily along Z, and compared them with the conventional experiments, in which water magnetization is inverted during the t1 period. The result demonstrates moderate gain of signal-to-noise ratio, 0-28%. Designing the experiments such that water magnetization is maintained in the upper hemisphere allows shorter pulses to be used compared to the complete water flip-back and, thereby, is useful as a building block of protein NMR pulse programs in solution.

  18. Effects of radiation damping for biomolecular NMR experiments in solution: a hemisphere concept for water suppression

    PubMed Central

    Ishima, Rieko

    2016-01-01

    Abundant solvent nuclear spins, such as water protons in aqueous solution, cause radiation damping in NMR experiments. It is important to know how the effect of radiation damping appears in high-resolution protein NMR because macromolecular studies always require very high magnetic field strengths with a highly sensitive NMR probe that can easily cause radiation damping. Here, we show the behavior of water magnetization after a pulsed-field gradient (PFG) using nutation experiments at 900 MHz with a cryogenic probe: when water magnetization is located in the upper hemisphere (having +Z component, parallel to the external magnetic field), dephasing of the magnetization by a PFG effectively suppresses residual water magnetization in the transverse plane. In contrast, when magnetization is located in the lower hemisphere (having −Z component), the small residual transverse component remaining after a PFG is still sufficient to induce radiation damping. Based on this observation, we designed 1H-15N HSQC experiments in which water magnetization is maintained in the upper hemisphere, but not necessarily along Z, and compared them with the conventional experiments, in which water magnetization is inverted during the t1 period. The result demonstrates moderate gain of signal-to-noise ratio, 0–28%. Designing the experiments such that water magnetization is maintained in the upper hemisphere allows shorter pulses to be used compared to the complete water flip-back and, thereby, is useful as a building block of protein NMR pulse programs in solution. PMID:27524944

  19. Determining material damping type by comparing modal frequency estimators.

    PubMed

    Anthony, D K; Simón, F; Juan, Jesús

    2009-09-01

    The accuracy of modal frequency and damping estimators for non-lightly damped single degree of freedom systems depend on the response parameter used as well as the damping mechanism. Therefore, in order to make accurate modal parameter measurements, the damping mechanism at play must be known to be either viscous or hysteretic a priori. Here, comparisons between the evaluated frequency values are used to glean this information. The damping mechanism of an experimental system (consisting of resilient layer and mass plate) is then determined using two simple modal parameter estimators and applying statistical methods.

  20. Fast damping in mismatched high intensity beam transportation

    NASA Astrophysics Data System (ADS)

    Variale, V.

    2001-08-01

    A very fast damping of beam envelope oscillation amplitudes was recently observed in simulations of high intensity beam transport, through periodic FODO cells, in mismatched conditions [V. Variale, Nuovo Cimento Soc. Ital. Fis. 112A, 1571-1582 (1999) and T. Clauser et al., in Proceedings of the Particle Accelerator Conference, New York, 1999 (IEEE, Piscataway, NJ, 1999), p. 1779]. A Landau damping mechanism was proposed at the origin of observed effect. In this paper, to further investigate the source of this fast damping, extensive simulations have been carried out. The results presented here support the interpretation of the mechanism at the origin of the fast damping as a Landau damping effect.

  1. Effects of damping on mode shapes, volume 1

    NASA Technical Reports Server (NTRS)

    Gates, R. M.

    1977-01-01

    Displacement, velocity, and acceleration admittances were calculated for a realistic NASTRAN structural model of space shuttle for three conditions: liftoff, maximum dynamic pressure and end of solid rocket booster burn. The realistic model of the orbiter, external tank, and solid rocket motors included the representation of structural joint transmissibilities by finite stiffness and damping elements. Methods developed to incorporate structural joints and their damping characteristics into a finite element model of the space shuttle, to determine the point damping parameters required to produce realistic damping in the primary modes, and to calculate the effect of distributed damping on structural resonances through the calculation of admittances.

  2. A soft damping function for dispersion corrections with less overfitting.

    PubMed

    Ucak, Umit V; Ji, Hyunjun; Singh, Yashpal; Jung, Yousung

    2016-11-07

    The use of damping functions in empirical dispersion correction schemes is common and widespread. These damping functions contain scaling and damping parameters, and they are usually optimized for the best performance in practical systems. In this study, it is shown that the overfitting problem can be present in current damping functions, which can sometimes yield erroneous results for real applications beyond the nature of training sets. To this end, we present a damping function called linear soft damping (lsd) that suffers less from this overfitting. This linear damping function damps the asymptotic curve more softly than existing damping functions, attempting to minimize the usual overcorrection. The performance of the proposed damping function was tested with benchmark sets for thermochemistry, reaction energies, and intramolecular interactions, as well as intermolecular interactions including nonequilibrium geometries. For noncovalent interactions, all three damping schemes considered in this study (lsd, lg, and BJ) roughly perform comparably (approximately within 1 kcal/mol), but for atomization energies, lsd clearly exhibits a better performance (up to 2-6 kcal/mol) compared to other schemes due to an overfitting in lg and BJ. The number of unphysical parameters resulting from global optimization also supports the overfitting symptoms shown in the latter numerical tests.

  3. A soft damping function for dispersion corrections with less overfitting

    NASA Astrophysics Data System (ADS)

    Ucak, Umit V.; Ji, Hyunjun; Singh, Yashpal; Jung, Yousung

    2016-11-01

    The use of damping functions in empirical dispersion correction schemes is common and widespread. These damping functions contain scaling and damping parameters, and they are usually optimized for the best performance in practical systems. In this study, it is shown that the overfitting problem can be present in current damping functions, which can sometimes yield erroneous results for real applications beyond the nature of training sets. To this end, we present a damping function called linear soft damping (lsd) that suffers less from this overfitting. This linear damping function damps the asymptotic curve more softly than existing damping functions, attempting to minimize the usual overcorrection. The performance of the proposed damping function was tested with benchmark sets for thermochemistry, reaction energies, and intramolecular interactions, as well as intermolecular interactions including nonequilibrium geometries. For noncovalent interactions, all three damping schemes considered in this study (lsd, lg, and BJ) roughly perform comparably (approximately within 1 kcal/mol), but for atomization energies, lsd clearly exhibits a better performance (up to 2-6 kcal/mol) compared to other schemes due to an overfitting in lg and BJ. The number of unphysical parameters resulting from global optimization also supports the overfitting symptoms shown in the latter numerical tests.

  4. Development of Transverse Modes Damped DLA Structure

    SciTech Connect

    Jing, C.; Kanareykin, A.; Schoessow, P.; Gai, W.; Konecny, R.; Power, J. G.; Conde, M.

    2009-01-22

    As the dimensions of accelerating structures become smaller and beam intensities higher, the transverse wakefields driven by the beam become quite large with even a slight misalignment of the beam from the geometric axis. These deflection modes can cause inter-bunch beam breakup and intra-bunch head-tail instabilities along the beam path, and thus BBU control becomes a critical issue. All new metal based accelerating structures, like the accelerating structures developed at SLAC or power extractors at CLIC, have designs in which the transverse modes are heavily damped. Similarly, minimizing the transverse wakefield modes (here the HEMmn hybrid modes in Dielectric-Loaded Accelerating (DLA) structures) is also very critical for developing dielectric based high energy accelerators. In this paper, we present the design of a 7.8 GHz transverse mode damped DLA structure currently under construction, along with plans for the experimental program.

  5. Relativity Damps OPEP in Nuclear Matter

    NASA Astrophysics Data System (ADS)

    Banerjee, Manoj K.

    1998-09-01

    Using a relativistic Dirac--Brueckner analysis the OPEP contribution to the ground state energy of nuclear matter is studied. In the study the pion is derivative-coupled. We find that the role of the tensor force in the saturation mechanism is substantially reduced compared to its dominant role in a usual nonrelativistic treatment. We show that the damping of derivative-coupled OPEP is actually due to the decrease of M*/M with increasing density. We point out that if derivative-coupled OPEP is the preferred form of nuclear effective Lagrangian nonrelativistic treatment of nuclear matter is in trouble. Lacking the notion of M* it cannot replicate the damping. We suggest an examination of the feasibility of using pseudoscalar coupled πN interaction before reaching a final conclusion about nonrelativistic treatment of nuclear matter.

  6. Random vibrations of a damped rotating shaft

    NASA Astrophysics Data System (ADS)

    Dimentberg, M. F.; Ryzhik, B.; Sperling, L.

    2005-01-01

    Response of a simple Jeffcott rotor to random excitation is considered with both external and internal damping taken into account. Mean square responses are predicted by the method of moments for the cases of transverse and angular (tilting) oscillations. Contrary to unbalance-induced response the random vibrations are shown to depend on the internal or "rotating" damping; in particular, their level increases with approaching threshold speed for dynamic instability. Procedure for estimating this threshold from on-line measurements of the shaft's random vibrations at a constant rotation speed is outlined based on the calculating coherence function of lateral displacements in two perpendicular directions for the case of transverse vibrations and that of tilting angles about two perpendicular axes for the case of tilting oscillations. Dependence of the mean square responses on the rotation speed can also be used for the stability margin evaluation.

  7. Wakefield Damping for the CLIC Crab Cavity

    SciTech Connect

    Ambattu, P.K.; Burt, G.; Dexter, A.C.; Carter, R.G.; Khan, V.; Jones, R.M.; Dolgashev, V.; /SLAC

    2011-12-01

    A crab cavity is required in the CLIC to allow effective head-on collision of bunches at the IP. A high operating frequency is preferred as the deflection voltage required for a given rotation angle and the RF phase tolerance for a crab cavity are inversely proportional to the operating frequency. The short bunch spacing of the CLIC scheme and the high sensitivity of the crab cavity to dipole kicks demand very high damping of the inter-bunch wakes, the major contributor to the luminosity loss of colliding bunches. This paper investigates the nature of the wakefields in the CLIC crab cavity and the possibility of using various damping schemes to suppress them effectively.

  8. Active Vibration Damping of Solar Arrays

    NASA Astrophysics Data System (ADS)

    Reinicke, Gunar; Baier, Horst; Grillebeck, Anton; Scharfeld, Frank; Hunger, Joseph; Abou-El-Ela, A.; Lohberg, Andreas

    2012-07-01

    Current generations of large solar array panels are lightweight and flexible constructions to reduce net masses. They undergo strong vibrations during launch. The active vibration damping is one convenient option to reduce vibration responses and limit stresses in facesheets. In this study, two actuator concepts are used for vibration damping. A stack interface actuator replaces a panel hold down and is decoupled from bending moments and shear forces. Piezoelectric patch actuators are used as an alternative, where the number, position and size of actuators are mainly driven by controllability analyses. Linear Quadratic Gaussian control is used to attenuate vibrations of selected mode shapes with both actuators. Simulations as well as modal and acoustic tests show the feasibility of selected actuator concepts.

  9. Utilising HVDC to damp power oscillations

    SciTech Connect

    Smed, T.; Andersson, G. . Dept. of Electric Power Systems)

    1993-04-01

    In this paper, damping of slow oscillations with active and reactive power modulation of HVDC-links is analyzed with the aim of gaining a physical insight into the problem. The analysis shows that active power modulation is efficient when applied to a short mass-scaled electrical distance from one of the swinging machines, and reactive power modulation is most efficient when there exists a well-defined power flow direction and the modulation is made at a point close to the electrical midpoint between the swinging machines. It is shown that the intuitively appealing feedback signals frequency and derivative of the voltage are appropriate for active and reactive power modulation, respectively. The impact of the constraints imposed by the HVDC equations are analyzed, and it is determined when the implicit reactive power modulation resulting from constant [gamma] control may be detrimental for the damping.

  10. Accelerator physics measurements at the damping ring

    SciTech Connect

    Rivkin, L.; Delahaye, J.P.; Wille, K.; Allen, M.; Bane, K.; Fieguth, T.; Hofmann, A.; Hutton, A.; Lee, M.; Linebarger, W.

    1985-05-01

    Besides the optics measurements described elsewhere, machine experiments were done at the SLC damping ring to determine some of its parameters. The synchrotron radiation energy loss which gives the damping rates was measured by observing the rf-voltage dependence of the synchronous phase angle. The emittance was obtained from the synchrotron light monitor, scraper measurements and by extracting the beam through a doublet and measuring its size for different quadrupole settings. Current dependent effects such as parasitic mode losses, head tail instabilities, synchrotron and betatron frequency shifts were measured to estimate the impedance. Rf-cavity beam loading and its compensation were also studied and ion collection was investigated. All results agree reasonably well with expectations and indicate no limitations to the design performance.

  11. Plasmon damping in graphene out of equilibrium

    NASA Astrophysics Data System (ADS)

    Sun, Zhiyuan; Basov, Dimitri; Fogler, Michael

    Motivated by recent experiments with graphene under high photoexcitation, we study theoretically plasmons of graphene in the two-temperature regime, i.e., the regime where electrons are much hotter than the lattice. We calculate the plasmon damping due to scattering of electrons by acoustic phonons, which is the dominant intrinsic contribution in clean graphene. As the system relaxes to equilibrium, the plasmon frequency adiabatically changes with time. We show that this causes a partial compensation of the plasmon damping. A similar mechanism may apply to another collective mode (the energy wave) predicted to exist in graphene in the low-frequency hydrodynamic regime. Implications for infrared and THz pump-probe experiments are discussed.

  12. Relativity damps OPEP in nuclear matter

    SciTech Connect

    Banerjee, M.K.

    1998-06-01

    Using a relativistic Dirac-Brueckner analysis the OPEP contribution to the ground state energy of nuclear matter is studied. In the study the pion is derivative-coupled. The author finds that the role of the tensor force in the saturation mechanism is substantially reduced compared to its dominant role in a usual nonrelativistic treatment. He shows that the damping of derivative-coupled OPEP is actually due to the decrease of M{sup *}/M with increasing density. He points out that if derivative-coupled OPEP is the preferred form of nuclear effective lagrangian nonrelativistic treatment of nuclear matter is in trouble. Lacking the notion of M{sup *} it cannot replicate the damping. He suggests an examination of the feasibility of using pseudoscalar coupled {pi}N interaction before reaching a final conclusion about nonrelativistic treatment of nuclear matter.

  13. Enthalpy damping for the steady Euler equations

    NASA Technical Reports Server (NTRS)

    Jespersen, D. C.

    1984-01-01

    For inviscid steady flow problems where the enthalpy is constant at steady state, it was previously proposed to use the difference between the local enthalpy and the steady state enthalpy as a driving term to accelerate convergence of iterative schemes. This idea is analyzed, both on the level of the partial differential equation and on the level of a particular finite difference scheme. It is shown that for the two-dimensional unsteady Euler equations, a hyperbolic system with eigenvalues on the imaginary axis, there is no enthalpy damping strategy which moves all the eigenvalues into the open left half plane. For the numerical scheme, however, the analysis shows and examples verify that enthalpy damping is potentially effective in accelerating convergence to steady state.

  14. Enthalpy damping for the steady Euler equations

    NASA Technical Reports Server (NTRS)

    Jespersen, D. C.

    1985-01-01

    For inviscid steady flow problems where the enthalpy is constant at steady state, it was previously proposed to use the difference between the local enthalpy and the steady state enthalpy as a driving term to accelerate convergence of iterative schemes. This idea is analyzed, both on the level of the partial differential equation and on the level of a particular finite difference scheme. It is shown that for the two-dimensional unsteady Euler equations, a hyperbolic system with eigenvalues on the imaginary axis, there is no enthalpy damping strategy which moves all the eigenvalues into the open left half plane. For the numerical scheme, however, the analysis shows and examples verify that enthalpy damping is potentially effective in accelerating convergence to steady state.

  15. Pressurized fluid damping of nanoelectromechanical systems.

    PubMed

    Svitelskiy, Oleksiy; Sauer, Vince; Liu, Ning; Cheng, Kar-Mun; Finley, Eric; Freeman, Mark R; Hiebert, Wayne K

    2009-12-11

    Interactions of nanoscale structures with fluids are of current interest both in the elucidation of fluid dynamics at these small scales, and in determining the ultimate performance of nanoelectromechanical systems outside of vacuum. We present a comprehensive study of nanomechanical damping in three gases (He, N2, CO2), and liquid CO2. Resonant dynamics in multiple devices of varying size and frequency is measured over 10 decades of pressure (1 mPa-20 MPa) using time-domain stroboscopic optical interferometry. The wide pressure range allows full exploration of the regions of validity of Newtonian and non-Newtonian flow damping models. Observing free molecular flow behavior extending above 1 atm, we find a fluid relaxation time model to be valid throughout, but not beyond, the non-Newtonian regime, and a Newtonian flow vibrating spheres model to be valid in the viscous limit.

  16. On the damping capacity of cast irons

    NASA Astrophysics Data System (ADS)

    Golovin, S. A.

    2012-07-01

    The treatment of experimental data on the amplitude-dependent internal friction (ADIF) in terms of various theoretical models has revealed a staged character and the main mechanisms of the processes of energy dissipation in graphite with increasing amplitude of vibrations upon cyclic loading. It is shown that the level of the damping capacity of lamellar cast iron depends on the relationship between the elastic and strength characteristics of graphite and the matrix phase. In cast irons with a rigid matrix structure (pearlite, martensite), the energy dissipation is determined by the volume fraction and morphology of the initial graphite phase. In cast irons with a softer metallic phase (ferrite), the contact interaction of graphite inclusions with the matrix and the properties of the matrix introduce additional sources of high damping.

  17. Nonlinear Landau damping in the ionosphere

    NASA Technical Reports Server (NTRS)

    Kiwamoto, Y.; Benson, R. F.

    1978-01-01

    A model is presented to explain the non-resonant waves which give rise to the diffuse resonance observed near 3/2 f sub H by the Alouette and ISIS topside sounders, where f sub H is the ambient electron cyclotron frequency. In a strictly linear analysis, these instability driven waves will decay due to Landau damping on a time scale much shorter than the observed time duration of the diffuse resonance. Calculations of the nonlinear wave particle coupling coefficients, however, indicate that the diffuse resonance wave can be maintained by the nonlinear Landau damping of the sounder stimulated 2f sub H wave. The time duration of the diffuse resonance is determined by the transit time of the instability generated and nonlinearly maintained diffuse resonance wave from the remote short lived hot region back to the antenna. The model is consistent with the Alouette/ISIS observations, and clearly demonstrates the existence of nonlinear wave-particle interactions in the ionosphere.

  18. Movers and shakers: granular damping in microgravity.

    PubMed

    Bannerman, M N; Kollmer, J E; Sack, A; Heckel, M; Mueller, P; Pöschel, T

    2011-07-01

    The response of an oscillating granular damper to an initial perturbation is studied using experiments performed in microgravity and granular dynamics simulations. High-speed video and image processing techniques are used to extract experimental data. An inelastic hard sphere model is developed to perform simulations and the results are in excellent agreement with the experiments. In line with previous work, a linear decay of the amplitude is observed. Although this behavior is typical for a friction-damped oscillator, through simulation it is shown that this effect is still present even when friction forces are absent. A simple expression is developed which predicts the optimal damping conditions for a given amplitude and is independent of the oscillation frequency and particle inelasticities.

  19. Harmonic cavities for the NLC damping rings

    SciTech Connect

    de Santis, S.; Wolski, A.

    2003-05-29

    To achieve high luminosity, a linear collider needs damping rings to produce beams with very small transverse emittances. In the NLC, design constraints place the Main Damping Rings in a parameter regime where intrabeam scattering (IBS) is likely to be a limitation on the emittance, and hence on the final luminosity. It is possible to mitigate the effects of IBS by lengthening the bunch: this may be achieved by redesigning the lattice with higher momentum compaction, or by use of higher harmonic cavities. Here, we consider the latter approach. We estimate the required bunch lengthening that might be needed, outline some appropriate parameters for the harmonic cavities, and discuss some of the effects that might be introduced or exacerbated by the cavities, such as synchronous phase variation along the bunch train.

  20. The impact damped harmonic oscillator in free decay

    NASA Technical Reports Server (NTRS)

    Brown, G. V.; North, C. M.

    1987-01-01

    The impact-damped oscillator in free decay is studied by using time history solutions. A large range of oscillator amplitude is covered. The amount of damping is correlated with the behavior of the impacting mass. There are three behavior regimes: (1) a low amplitude range with less than one impact per cycle and very low damping, (2) a useful middle amplitude range with a finite number of impacts per cycle, and (3) a high amplitude range with an infinite number of impacts per cycle and progressively decreasing damping. For light damping the impact damping in the middle range is: (1) proportional to impactor mass, (2) additive to proportional damping, (3) a unique function of vibration amplitude, (4) proportional to 1-epsilon, where epsilon is the coefficient of restitution, and (5) very roughly inversely proportional to amplitude. The system exhibits jump phenomena and period doublings. An impactor with 2 percent of the oscillator's mass can produce a loss factor near 0.1.

  1. Unified micromechanics of damping for unidirectional fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Saravanos, D. A.; Chamis, C. C.

    1989-01-01

    An integrated micromechanics methodology for the prediction of damping capacity in fiber-reinforced polymer matrix unidirectional composites has been developed. Explicit micromechanics equations based on hysteretic damping are presented relating the on-axis damping capacities to the fiber and matrix properties and volume fraction. The damping capacities of unidirectional composites subjected to off-axis loading are synthesized from thermal effect on the damping performance of unidirectional composites due to temperature and moisture variations is also modeled. The damping contributions from interfacial friction between broken fibers and matrix are incorporated. Finally, the temperature rise in continuously vibrating composite plies is estimated. Application examples illustrate the significance of various parameters on the damping performance of unidirectional and off-axis fiber reinforced composites.

  2. Damping Materials, Finite Elements and Special Projects.

    DTIC Science & Technology

    1982-12-01

    made of either Haynes Alloy Number 188, Hastalloy C, Hastalloy X, or 17 - 4PH stainless steel Hastalloy X. Figure 1.26 is a schematic of the test...Motors Corporation (DDA), conducted a cooperative effort to characterize a DDA proprietary temperature damping material. The UDRI supplied two 17 - 4PH ...range at which the 17 - 4PH stainless steel beams could be tested. Serious discrepancy was noted between the structural loss factors derived from the room

  3. CASTOR damping experiment in-flight results

    NASA Astrophysics Data System (ADS)

    Guay, Philippe; Bousquet, Paul W.; Courau, E.; Mercier, F.

    2001-07-01

    Over the past ten years, space structures such as optical systems, large antennae or sensitive microgravity payloads have increased their stability requirements. To answer this need, prediction and reduction of vibration levels have been widely studied. The 'CASTOR' truss experiment (French acronym for ChAracterization of STructures in ORbit) is mainly dedicated to the investigation of the dynamic behaviour -in zero g conditions- of a truss mock-up with various damping technologies. The performances of various dampers have been validated in flight, measurements compared with the predictions and the results analysed for different technological solutions. This project was developed under CNES management, and the final experimental work was performed in orbit by a French cosmonaut on MIR station during the summer of 1999. In the first place, the French space agency's interest in structural dynamics behind the CASTOR experiment will be recalled. The flight hardware will then be fully described and a short clip filmed during the PERSEUS mission in MIR will supported this. The truss test bench will be presented, together with the design drivers for damping the first structural modes below 100Hz. The dampers -which are efficient- are located in some strategic bars in the truss. Their performance has been optimized using an energetic criterion. This paper will then focus on the design of the damping, using either piezoelectric active control or passive energy dissipation in elastomer or fluid devices. Particular emphasis will be laid upon the excellent flight results obtained with all the various damping systems, and on the effect of in-orbit conditions. A comparison between the different technologies here tested will also be made with regards to performances achieved and their suitability for space applications. In conclusion, lessons learned during the development process will be highlighted and further work on spacecraft applications discussed.

  4. Vibration Damping Response of Composite Materials

    DTIC Science & Technology

    1991-04-01

    to predict the vibration damping of these coposites. L lein Irauu, .. rii. se i-s foi tesi specimel gC-miLtrics oSl0y, so that - material...manner that the strain in the x direction was determined. This development results in the transverse strain given as av (x,y,z) avO (x,y)ei~ t a 2wO(xy) ei

  5. Coulomb collision effects on linear Landau damping

    SciTech Connect

    Callen, J. D.

    2014-05-15

    Coulomb collisions at rate ν produce slightly probabilistic rather than fully deterministic charged particle trajectories in weakly collisional plasmas. Their diffusive velocity scattering effects on the response to a wave yield an effective collision rate ν{sub eff} ≫ ν and a narrow dissipative boundary layer for particles with velocities near the wave phase velocity. These dissipative effects produce temporal irreversibility for times t ≳ 1/ν{sub eff} during Landau damping of a small amplitude Langmuir wave.

  6. Fluidic Technology Investigation - Suspension Damping Simulations

    DTIC Science & Technology

    1977-01-01

    IF (w (I LT’ CVM)~4$1 IF ( Wrf 1 0 i CmpY MX2)V?1112wW~ CALL ORPArIP:(Pcx) pP,i.,IERR) .......-or pi i v~,R4p CAlLA (QAI)Rr7,4,?,T.ERR) T F Z (I ~LT C V...Damper Damping Devices Suspension Systems Shock Absorbers Adaptive Suspension Systems Hydro -Fluidics 20. ABSTRACT (Continue on reverse side if necessary

  7. Damping in Ferrous Shape Memory Alloys

    DTIC Science & Technology

    1993-08-01

    time it has been proposed that the solution lies in the approach of energy dissipation by using metallic structural materials which have inherent...and automotive manufacturing plants, has never achieved commercial producton . 1-b. Ferromagnetic alloys, such as Fe-Cr alloys High damping Fe-Cr alloys...Pre-exsiring mar~en-si,ýe worms orwie treenred orieL a ion ! A Lr cow s SL AL 14- L AL Figure 26. Schematic illustration of various processes involved

  8. Robot vibration control using inertial damping forces

    NASA Technical Reports Server (NTRS)

    Lee, Soo Han; Book, Wayne J.

    1991-01-01

    This paper concerns the suppression of the vibration of a large flexible robot by inertial forces of a small robot which is located at the tip of the large robot. A controller for generating damping forces to a large robot is designed based on the two time scale model. The controller does not need to calculate the quasi-steady variables and is efficient in computation. Simulation results show the effectiveness of the inertial forces and the controller designed.

  9. Robot vibration control using inertial damping forces

    NASA Technical Reports Server (NTRS)

    Lee, Soo Han; Book, Wayne J.

    1989-01-01

    The suppression is examined of the vibration of a large flexible robot by inertial forces of a small robot which is located at the tip of the large robot. A controller for generating damping forces to a large robot is designed based on the two time scale mode. The controller does not need to calculate the quasi-steady state variables and is efficient in computation. Simulation results show the effectiveness of the inertial forces and the controller designed.

  10. Collisional damping rates for plasma waves

    SciTech Connect

    Tigik, S. F. Ziebell, L. F.; Yoon, P. H.

    2016-06-15

    The distinction between the plasma dynamics dominated by collisional transport versus collective processes has never been rigorously addressed until recently. A recent paper [P. H. Yoon et al., Phys. Rev. E 93, 033203 (2016)] formulates for the first time, a unified kinetic theory in which collective processes and collisional dynamics are systematically incorporated from first principles. One of the outcomes of such a formalism is the rigorous derivation of collisional damping rates for Langmuir and ion-acoustic waves, which can be contrasted to the heuristic customary approach. However, the results are given only in formal mathematical expressions. The present brief communication numerically evaluates the rigorous collisional damping rates by considering the case of plasma particles with Maxwellian velocity distribution function so as to assess the consequence of the rigorous formalism in a quantitative manner. Comparison with the heuristic (“Spitzer”) formula shows that the accurate damping rates are much lower in magnitude than the conventional expression, which implies that the traditional approach over-estimates the importance of attenuation of plasma waves by collisional relaxation process. Such a finding may have a wide applicability ranging from laboratory to space and astrophysical plasmas.

  11. Random Response of Linear Hysteretic Damping

    SciTech Connect

    Floris, Claudio

    2008-07-08

    The probabilistic characterization of the response of a single-degree-of-freedom (SDOF) oscillator with linear hysteretic damping excited by ground motion described by zero mean stationary Gaussian processes is achieved by profiting from a steady-state solution of the motion equation, valid when the excitation is given by the superposition of harmonics. The model of linear hysteretic damping has been introduced to fit damping mechanisms in which the dissipation rate is independent of frequency, and mathematically it is described by the Hilbert transform of the response. Though this model is debated since it violates the principle of causality, its intrinsic simplicity makes it preferable to other models. The steady-state solution of the motion equation proposed in this paper allows a closed form evaluation of the respone mean square value. However, the numerical examples show that this quantity is affected by the mechanism of energy dissipation only when this is large. On the contrary, for a low capacity of dissipation the response mean square value is rather insensitive to the dissipation mechanism.

  12. A comparison of viscoelastic damping models

    NASA Technical Reports Server (NTRS)

    Slater, Joseph C.; Belvin, W. Keith; Inman, Daniel J.

    1993-01-01

    Modern finite element methods (FEM's) enable the precise modeling of mass and stiffness properties in what were in the past overwhelmingly large and complex structures. These models allow the accurate determination of natural frequencies and mode shapes. However, adequate methods for modeling highly damped and high frequency dependent structures did not exist until recently. The most commonly used method, Modal Strain Energy, does not correctly predict complex mode shapes since it is based on the assumption that the mode shapes of a structure are real. Recently, many techniques have been developed which allow the modeling of frequency dependent damping properties of materials in a finite element compatible form. Two of these methods, the Golla-Hughes-McTavish method and the Lesieutre-Mingori method, model the frequency dependent effects by adding coordinates to the existing system thus maintaining the linearity of the model. The third model, proposed by Bagley and Torvik, is based on the Fractional Calculus method and requires fewer empirical parameters to model the frequency dependence at the expense of linearity of the governing equations. This work examines the Modal Strain Energy, Golla-Hughes-McTavish and Bagley and Torvik models and compares them to determine the plausibility of using them for modeling viscoelastic damping in large structures.

  13. Synchrosqueezed wavelet transform for damping identification

    NASA Astrophysics Data System (ADS)

    Mihalec, Marko; Slavič, Janko; Boltežar, Miha

    2016-12-01

    Synchrosqueezing is a procedure for improving the frequency localization of a continuous wavelet transform. This research focuses on using a synchrosqueezed wavelet transform (SWT) to determine the damping ratios of a vibrating system using a free-response signal. While synchrosqueezing is advantageous due to its localisation in the frequency, damping identification with the original SWT is not sufficiently accurate. Here, the synchrosqueezing was researched in detail, and it was found that an error in the frequency occurs as a result of the numerical calculation of the preliminary frequencies. If this error were to be compensated, a better damping identification would be expected. To minimize the frequency-shift error, three different strategies are investigated: the scale-dependent coefficient method, the shifted-coefficient method and the autocorrelated-frequency method. Furthermore, to improve the SWT, two synchrosqueezing criteria are introduced: the average SWT and the proportional SWT. Finally, the proposed modifications are tested against close modes and the noise in the signals. It was numerically and experimentally confirmed that the SWT with the proportional criterion offers better frequency localization and performs better than the continuous wavelet transform when tested against noisy signals.

  14. Collisional damping rates for plasma waves

    NASA Astrophysics Data System (ADS)

    Tigik, S. F.; Ziebell, L. F.; Yoon, P. H.

    2016-06-01

    The distinction between the plasma dynamics dominated by collisional transport versus collective processes has never been rigorously addressed until recently. A recent paper [P. H. Yoon et al., Phys. Rev. E 93, 033203 (2016)] formulates for the first time, a unified kinetic theory in which collective processes and collisional dynamics are systematically incorporated from first principles. One of the outcomes of such a formalism is the rigorous derivation of collisional damping rates for Langmuir and ion-acoustic waves, which can be contrasted to the heuristic customary approach. However, the results are given only in formal mathematical expressions. The present brief communication numerically evaluates the rigorous collisional damping rates by considering the case of plasma particles with Maxwellian velocity distribution function so as to assess the consequence of the rigorous formalism in a quantitative manner. Comparison with the heuristic ("Spitzer") formula shows that the accurate damping rates are much lower in magnitude than the conventional expression, which implies that the traditional approach over-estimates the importance of attenuation of plasma waves by collisional relaxation process. Such a finding may have a wide applicability ranging from laboratory to space and astrophysical plasmas.

  15. Metallic materials for mechanical damping capacity applications

    NASA Astrophysics Data System (ADS)

    Crăciun, R. C.; Stanciu, S.; Cimpoeșu, R.; (Dragoș Ursanu, A. I.; Manole, V.; Paraschiv, P.; Chicet, D. L.

    2016-08-01

    Some metallic materials exhibit good damping capacity of mechanical energy into thermal energy. This property along with the others metallic characteristics make this materials interesting for a big number of applications. These materials can be used as bumpers in different applications including automotive field. Beside grey cast iron and shape memory alloys few new metallic materials are presented for the supposition of high damping capacity. We analyze the causes that increase the internal friction of some metallic materials and possibilities to enhance this property through different mechanical, physical or chemical methods. Shape memory alloys, especially those based on copper, present a different damping capacity on martensite, austenite or transition state. In the transformation range M ↔A, which in case of copper base shape memory alloys is quite large, the metallic intelligent materials present a high internal friction, almost comparable with natural rubber behavior that can transform mechanical energy into thermal energy till a certain value of the external solicitation. These materials can be used as noise or small vibrations bumpers or even as shock absorbers in automotive industry.

  16. Active damping of the SOFIA Telescope assembly

    NASA Astrophysics Data System (ADS)

    Keas, Paul J.; Dunham, Edward; Lampater, Ulrich; Pfüller, Enrico; Teufel, Stefan; Roeser, Hans-Peter; Wiedemann, Manuel; Wolf, Jürgen

    2012-09-01

    The NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA) employs a 2.5-meter reflector telescope in a Boeing 747SP. The telescope is housed in an open cavity and is subjected to aeroacoustic and inertial disturbances in flight. To meet pointing requirements, SOFIA must achieve a pointing stability of approximately 0.5 arcseconds RMS. An active damping control system is being developed for SOFIA to reduce image jitter and image degradation due to resonance of the telescope assembly. Our paper discusses the history of the active damping design for SOFIA, from early concepts to the current implementation which has recently completed a ground and flight testing for proof-of-concept. We describe some milestones in the analysis and testing of the telescope assembly which guided the development of the vibration control system. The control synthesis approach and current implementation of the active damping control system is presented. Finally, we summarize the performance observed in early flight tests and the steps that are currently foreseen to completing the development of this system.

  17. DAMPs and influenza virus infection in ageing.

    PubMed

    Samy, Ramar Perumal; Lim, Lina H K

    2015-11-01

    Influenza A virus (IAV) is a serious global health problem worldwide due to frequent and severe outbreaks. IAV causes significant morbidity and mortality in the elderly population, due to the ineffectiveness of the vaccine and the alteration of T cell immunity with ageing. The cellular and molecular link between ageing and virus infection is unclear and it is possible that damage associated molecular patterns (DAMPs) may play a role in the raised severity and susceptibility of virus infections in the elderly. DAMPs which are released from damaged cells following activation, injury or cell death can activate the immune response through the stimulation of the inflammasome through several types of receptors found on the plasma membrane, inside endosomes after endocytosis as well as in the cytosol. In this review, the detriment in the immune system during ageing and the links between influenza virus infection and ageing will be discussed. In addition, the role of DAMPs such as HMGB1 and S100/Annexin in ageing, and the enhanced morbidity and mortality to severe influenza infection in ageing will be highlighted. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Discrete-layered damping model of multilayer plate with account of internal damping

    NASA Astrophysics Data System (ADS)

    Paimushin, V. N.; Gazizullin, R. K.

    2016-11-01

    Construction of discrete-layered damping model of multilayer plate in small displacement and deformations with account of internal damping of layers of Thompson- Kelvin-Voight model is presented. Based on derived equations, analytical solution is given to the static damping problem of simply supported single-layer rectangular plate subjected to uniformly distributed pressure, which is applied to one of its boundary planes. Convergence to the three-dimensional case is analysed for the obtained solution with respect to the dependence on dimension of mesh in the thickness direction of plate. For thin plates, dimension reduction of the formulated problem is set on the basis of simplifying hypothesis applied for each layer.

  19. Characterization of high damping bearings and their responses to earthquake motions

    SciTech Connect

    Wu, Ting-shu; Seidensticker, R.W.

    1990-01-01

    An isolation system consisting of six (6) laminated high-damping rubber bearings has been installed in a test facility on the Tohoku University site in Sendai, Japan. The isolation system is designed to have a frequency of 0.75 Hz. This frequency, however, is obtained only when there is a strong earthquake, resulting in significant horizontal displacements. After the installation of this system, in April 1989, static and dynamic tests were performed to obtained fundamental dynamic response properties of the system. The day after these tests were completed, an earthquake of magnitude M = 4.9 occurred in the area. The maximum acceleration experienced by the building was only about 0.03 g. Several other earthquakes have occurred since then, all of which resulted in low input acceleration at the Tohoku facility. Analytical investigations for the building have been carried out using a model with stiffness and damping of the isolation system obtained from the in-situ tests. Response of the simulated model to this earthquake show good agreement with the recorded data at each floor of the isolated building. Both the recorded data and the analytical results indicate that the bearings installed in this building are stiff enough to prevent drift of the superstructure under minor tremors or wind loads. Results of all in-situ tests are presented. 5 refs., 10 figs., 1 tab.

  20. Non-Linear Slosh Damping Model Development and Validation

    NASA Technical Reports Server (NTRS)

    Yang, H. Q.; West, Jeff

    2015-01-01

    Propellant tank slosh dynamics are typically represented by a mechanical model of spring mass damper. This mechanical model is then included in the equation of motion of the entire vehicle for Guidance, Navigation and Control (GN&C) analysis. For a partially-filled smooth wall propellant tank, the critical damping based on classical empirical correlation is as low as 0.05%. Due to this low value of damping, propellant slosh is potential sources of disturbance critical to the stability of launch and space vehicles. It is postulated that the commonly quoted slosh damping is valid only under the linear regime where the slosh amplitude is small. With the increase of slosh amplitude, the critical damping value should also increase. If this nonlinearity can be verified and validated, the slosh stability margin can be significantly improved, and the level of conservatism maintained in the GN&C analysis can be lessened. The purpose of this study is to explore and to quantify the dependence of slosh damping with slosh amplitude. Accurately predicting the extremely low damping value of a smooth wall tank is very challenging for any Computational Fluid Dynamics (CFD) tool. One must resolve thin boundary layers near the wall and limit numerical damping to minimum. This computational study demonstrates that with proper grid resolution, CFD can indeed accurately predict the low damping physics from smooth walls under the linear regime. Comparisons of extracted damping values with experimental data for different tank sizes show very good agreements. Numerical simulations confirm that slosh damping is indeed a function of slosh amplitude. When slosh amplitude is low, the damping ratio is essentially constant, which is consistent with the empirical correlation. Once the amplitude reaches a critical value, the damping ratio becomes a linearly increasing function of the slosh amplitude. A follow-on experiment validated the developed nonlinear damping relationship. This discovery can

  1. A new global approach using a network of piezoelectric elements and energy redistribution for enhanced vibration damping of smart structure

    NASA Astrophysics Data System (ADS)

    Wu, Dan; Guyomar, Daniel; Richard, Claude

    2013-04-01

    A new global approach for improved vibration damping of smart structure, based on global energy redistribution by means of a network of piezoelectric elements is proposed. It is basically using semi-active Synchronized Switch Damping technique. SSD technique relies on a cumulative build-up of the voltage resulting from the continuous switching and it was shown that the performance is strongly related to this voltage. The increase of the piezoelectric voltage results in improvement of the damping performance. External voltage sources or improved switching sequences were previously designed to increase this voltage in the case of single piezoelectric element structure configurations. This paper deals with extended structure with many embedded piezoelectric elements. The proposed strategy consist of using an electric network made with non-linear component and switches in order to set up and control a low-loss energy transfer from source piezoelements extracting the vibration energy of the structure and oriented toward a given piezoelement in order to increase its operative energy for improving a given mode damping. This paper presents simulation of a clamped plate with four piezoelectric elements implemented in the Matlab/SimulinkTM environment and SimscapeTM library. The various simulation cases show the relationship between the damping performance on a given targeted mode and the established power flow. SSDD and SSDT are two proposed original networks. Performances are compared to the SSDI baseline. A damping increase of 18dB can be obtained even with a weakly coupled piezoelectric element in the multi-sine excitation case. This result proves the importance of new global non-linear multi-actuator strategies for improved vibration damping of extended smart structure.

  2. Meta-Analyses of the Associations of Respiratory Health Effectswith Dampness and Mold in Homes

    SciTech Connect

    Fisk, William J.; Lei-Gomez, Quanhong; Mendell, Mark J.

    2006-01-01

    The Institute of Medicine (IOM) of the National Academy of Sciences recently completed a critical review of the scientific literature pertaining to the association of indoor dampness and mold contamination with adverse health effects. In this paper, we report the results of quantitative meta-analysis of the studies reviewed in the IOM report. We developed point estimates and confidence intervals (CIs) to summarize the association of several respiratory and asthma-related health outcomes with the presence of dampness and mold in homes. The odds ratios and confidence intervals from the original studies were transformed to the log scale and random effect models were applied to the log odds ratios and their variance. Models were constructed both accounting for the correlation between multiple results within the studies analyzed and ignoring such potential correlation. Central estimates of ORs for the health outcomes ranged from 1.32 to 2.10, with most central estimates between 1.3 and 1.8. Confidence intervals (95%) excluded unity except in two of 28 instances, and in most cases the lower bound of the CI exceeded 1.2. In general, the two meta-analysis methods produced similar estimates for ORs and CIs. Based on the results of the meta-analyses, building dampness and mold are associated with approximately 30% to 80% increases in a variety of respiratory and asthma-related health outcomes. The results of these meta-analyses reinforce the IOM's recommendation that actions be taken to prevent and reduce building dampness problems.

  3. Dynamic analysis of systems having large damping variations

    SciTech Connect

    Philippacopoulos, A.J.

    1985-01-01

    In the earthquake response analysis of structures in which the damping characteristics between the elements varies significantly the standard mode superposition method cannot be used. Several approximations have been proposed that allow the application of the modal superposition method for cases in which the damping matrix is not orthogonal with respect to the modal shapes. The most commonly used approximation is based on a composite damping value which is employed in the modal equations. This value is a weighted average of the damping values of the individual components of the structural model. In this paper an investigation of the errors introduced by the composite damping in the response of simple structures is presented. The results given in the paper can be used for benchmarking the approximations in more complex systems for which composite damping solutions are employed.

  4. Dynamic analyses of viscoelastic dielectric elastomers incorporating viscous damping effect

    NASA Astrophysics Data System (ADS)

    Zhang, Junshi; Zhao, Jianwen; Chen, Hualing; Li, Dichen

    2017-01-01

    In this paper, based on the standard linear solid rheological model, a dynamics model of viscoelastic dielectric elastomers (DEs) is developed with incorporation of viscous damping effect. Numerical calculations are employed to predict the damping effect on the dynamic performance of DEs. With increase of damping force, the DEs show weak nonlinearity and vibration strength. Phase diagrams and Poincaré maps are utilized to detect the dynamic stability of DEs, and the results indicate that a transition from aperiodic vibration to quasi-periodic vibration occurs with enlargement of damping force. The resonance properties of DEs including damping effect are subsequently analyzed, demonstrating a reduction of resonant frequency and resonance peak with increase of damping force.

  5. Vibration control through passive constrained layer damping and active control

    NASA Astrophysics Data System (ADS)

    Lam, Margaretha J.; Inman, Daniel J.; Saunders, William R.

    1997-05-01

    To add damping to systems, viscoelastic materials (VEM) are added to structures. In order to enhance the damping effects of the VEM, a constraining layer is attached. When this constraining layer is an active element, the treatment is called active constrained layer damping (ACLD). Recently, the investigation of ACLD treatments has shown it to be an effective method of vibration suppression. In this paper, the treatment of a beam with a separate active element and passive constrained layer (PCLD) element is investigated. A Ritz- Galerkin approach is used to obtain discretized equations of motion. The damping is modeled using the GHM method and the system is analyzed in the time domain. By optimizing on the performance and control effort for both the active and passive case, it is shown that this treatment is capable of lower control effort with more inherent damping, and is therefore a better approach to damp vibration.

  6. Damping in high-temperature superconducting levitation systems

    DOEpatents

    Hull, John R.

    2009-12-15

    Methods and apparatuses for improved damping in high-temperature superconducting levitation systems are disclosed. A superconducting element (e.g., a stator) generating a magnetic field and a magnet (e.g. a rotor) supported by the magnetic field are provided such that the superconducting element is supported relative to a ground state with damped motion substantially perpendicular to the support of the magnetic field on the magnet. Applying this, a cryostat housing the superconducting bearing may be coupled to the ground state with high damping but low radial stiffness, such that its resonant frequency is less than that of the superconducting bearing. The damping of the cryostat may be substantially transferred to the levitated magnetic rotor, thus, providing damping without affecting the rotational loss, as can be derived applying coupled harmonic oscillator theory in rotor dynamics. Thus, damping can be provided to a levitated object, without substantially affecting the rotational loss.

  7. Active member bridge feedback control for damping augmentation

    NASA Technical Reports Server (NTRS)

    Chen, Gun-Shing; Lurie, Boris J.

    1992-01-01

    An active damping augmentation approach using active members in a structural system is described. The problem of maximizing the vibration damping in a lightly damped structural system is considered using the analogy of impedance matching between the load and source impedances in an electrical network. The proposed active damping augmentation approach therefore consists of finding the desired active member impedances that maximize the vibration damping, and designing a feedback control in order to achieve desired active member impedances. This study uses a bridge feedback concept that feeds back a combination of signals from sensors of the axial force and relative velocity across the active member to realize the desired active member impedance. The proposed active damping augmentation approach and bridge feedback concept were demonstrated on a three-longeron softly suspended truss structure.

  8. Research on damping properties optimization of variable-stiffness plate

    NASA Astrophysics Data System (ADS)

    Wen-kai, QI; Xian-tao, YIN; Cheng, SHEN

    2016-09-01

    This paper investigates damping optimization design of variable-stiffness composite laminated plate, which means fibre paths can be continuously curved and fibre angles are distinct for different regions. First, damping prediction model is developed based on modal dissipative energy principle and verified by comparing with modal testing results. Then, instead of fibre angles, the element stiffness and damping matrixes are translated to be design variables on the basis of novel Discrete Material Optimization (DMO) formulation, thus reducing the computation time greatly. Finally, the modal damping capacity of arbitrary order is optimized using MMA (Method of Moving Asymptotes) method. Meanwhile, mode tracking technique is employed to investigate the variation of modal shape. The convergent performance of interpolation function, first order specific damping capacity (SDC) optimization results and variation of modal shape in different penalty factor are discussed. The results show that the damping properties of the variable-stiffness plate can be increased by 50%-70% after optimization.

  9. Higher order mode damping in an ALS test cavity

    SciTech Connect

    Jacob, A.F.; Lamberston, G.R. ); Barry, W. )

    1990-06-01

    The higher order mode attenuation scheme proposed for the Advanced Light Source accelerating cavities consists of two broad-band dampers placed 90{degrees} apart on the outer edge. In order to assess the damping efficiency a test assembly was built. The HOM damping was obtained by comparing the peak values of the transmission through the cavity for both the damped and the undamped case. Because of the high number of modes and frequency shifts due to the damping gear, the damping was assessed statistically, by averaging over several modes. In the frequency range from 1.5 to 5.5 GHz, average damping greater than 100 was obtained. 1 ref., 6 figs.

  10. Nutation damping in viscoelastic tumbling rotators

    NASA Astrophysics Data System (ADS)

    Frouard, Julien; Efroimsky, Michael

    2015-11-01

    Presently, 138 asteroids show signs of being in non-principal spin states (Warner et al. 2009, updated September 2015). Such spin is often called `tumble' or `wobble'. The instantaneous rotation axis of a wobbling body performs nutation about the direction of the (conserved) angular-momentum vector. Incited by collisions and YORP, wobble is mitigated by internal dissipation due to the nutation-caused alternating stresses inside the asteroid.The knowledge of the timescale related to the damping of the nutation angle is complementary to the knowledge of the timescales associated with collisions and YORP. Previous evaluations of the nutation relaxation rate were based on an inherently inconsistent approach that may be called "Q-model". First, the elastic energy in a periodically deforming rotator was calculated in assumption of the deformation being elastic. Therefrom, the energy dissipation rate was determined by introducing an ad hoc quality factor Q. This ignored the fact that friction (and the ensuing existence of Q) is due to deviation from elasticity.We use the viscoelastic Maxwell model which naturally implies dissipation (as any other viscoelastic model would). In this approach, we compute the power and damping time for an oblate ellipsoid and a prism. Now, the viscosity assumes the role of the product μQ in the empirical Q-model, with μ being the rigidity. Contrarily to the Q-model, our model naturally gives a null dissipation for a shape tending to a sphere. We also explore when the constant part of the stress can be ignored in the derivation of the damping time. The neglect of prestressing turns out to be legitimate for the mean viscosity exceeding a certain threshold value.

  11. Imaging of Damped Ly-alpha Absorbers

    NASA Astrophysics Data System (ADS)

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

    1998-05-01

    Intervening H I gas clouds toward QSOs give rise to damped Ly-alpha absorption. Because of the high column density (N(H I)>= 2*E(20) cm(-2) ) these systems have been thought to be galactic disks in some stage of formation. However, because potential optical counterparts have not been identified for most damped Ly-alpha systems, it is possible that some of the absorbing systems could be dwarf irregular galaxies or low surface brightness galaxies, and are thus difficult to image. In any case, the absorbers are expected to have small angular separation from the QSOs, and so high resolution imaging is required to differentiate the absorbers from the QSOs. Because previous studies have not shown any dominant morphological form for the few candidate objects known, our images are obtained with the Hawaii tip-tilt system in order to achieve the best possible morphological classification. By imaging in the NIR and optical bands that bracket the 4000 Angstroms break of these Ly-alpha absorbers, we can more readily select candidate objects by photometrically constraining their redshifts. In our sample of 14 QSOs with abosorbers from 1damped Ly-alpha absorption systems which have no previously optically-identified counterparts, and for some of which we have Keck HIRES spectra. Companion papers in this session present the spectral analysis of two of these QSO's (Roth et al., Bauer et al.) and studies of M81 as a possible local analog of the Ly-alpha absorbers (Kolhatkar et al.)

  12. Study of Track Reconstruction for DAMPE

    NASA Astrophysics Data System (ADS)

    Lu, Tong-suo; Lei, Shi-jun; Zang, Jing-jing; Chang, Jin; Wu, Jian

    2017-07-01

    The Dark Matter Particle Explorer (DAMPE) is aimed to study the existence and distribution of dark matter via the observation of high-energy particles in space with a large energy bandwidth, high energy resolution, and high spatial resolution. The track reconstruction is to restore the positions and angles of the incident particles using the multiple observations of different channels at different positions, and its accuracy determines the angular resolution of the explorer. The track reconstruction is mainly based on the observations of two sub-detectors, namely, the Silicon Tracker (STK) and the BGO (Bi4Ge3O12) calorimeter. In accordance with the design and structure of the two sub-detectors, and using the data collected during the beam tests and ground tests of cosmic rays, we discuss in detail the method of track reconstruction for the DAMPE, which includes mainly three basic procedures: the selection of track hits, the fitting of track hits, and the judgement of the optimal track. Since an energetic particle most probably leaves multiple hits in different layers of the STK and BGO crystals, we first provide a method to obtain a rough track in the BGO calorimeter by the centroid method, and hereby to constrain the track hits in the STK. Then for the selected one group of possible track hits in the STK, we apply two different algorithms, the Kalman filter and the least square linear fitting, to fit these track hits. The consistency of the results obtained independently via the two algorithms confirms the validity of our track reconstruction results. Finally, several criteria for picking out the most possible track among all the tracks found in the reconstruction by combining the results of the BGO calorimeter and STK are discussed. Using the track reconstruction method proposed in this article and the beam test data, we confirm that the angular resolution of the DAMPE satisfies its design requirement.

  13. Researches on Track Reconstruction for DAMPE

    NASA Astrophysics Data System (ADS)

    Lu, T. S.; Lei, S. J.; Zang, J. J.; Chang, J.; Wu, J.

    2016-05-01

    The Dark Matter Particle Explorer (DAMPE) is aimed to study the existence and distribution of dark matter via observation of high energy particles in space with unprecedented large energy bandwidth, high energy resolution, and high space resolution. The track reconstruction is to restore the positions and angles of the incident particles using the multiple observations of different channels at different positions, and its accuracy determines the angular resolution of the detector. The track reconstruction is mainly based on the observations of two sub-detectors, namely, the Silicon Tracker (STK) detector and the BGO (Bi_4Ge_3O12) calorimeter. In accordance with the design and structure of the two sub-detectors and using the data collected during the beam tests and ground tests, we provide a detailed introduction of the track reconstruction of DAMPE data, including three basic steps, the selection of track hits, the fitting of track hits, and the judgement of the best track among (most probably) many of them. Since a high energy particle most probably leaves more than one hit in each level of the STK and BGO, we first provide a method to constrain the STK clusters for the track reconstruction using the rough result of the BGO reconstruction. We apply two different algorithms, the Kalman filter and the least square linear fitting, to fit the track hits. The consistency of the results obtained independently via the two algorithms confirms the validity of our track reconstruction results, and we discuss the advantages/disadvantages of each method. Several criteria combining the BGO and STK detection are discussed for picking out the most possible track among all the tracks found in the track reconstruction. Using the track reconstruction methods mentioned in this article and the beam test data, we confirm that the angular resolution of DAMPE satisfies the requirement in design.

  14. System for damping vibrations in a turbine

    DOEpatents

    Roberts, III, Herbert Chidsey; Johnson, Curtis Alan; Taxacher, Glenn Curtis

    2015-11-24

    A system for damping vibrations in a turbine includes a first rotating blade having a first ceramic airfoil, a first ceramic platform connected to the first ceramic airfoil, and a first root connected to the first ceramic platform. A second rotating blade adjacent to the first rotating blade includes a second ceramic airfoil, a second ceramic platform connected to the second ceramic airfoil, and a second root connected to the second ceramic platform. A non-metallic platform damper has a first position in simultaneous contact with the first and second ceramic platforms.

  15. HVDC system control for damping subsynchronous oscillations

    SciTech Connect

    Piwko, R.J.; Larsen, E.V.

    1982-07-01

    A method for designing a supplemental subsynchronous damping control (SSDC) for an HVDC transmission system is described. The SSDC eliminates torsional instabilities caused by interaction between conventional HVDC controls and turbine-generator rotor torsional modes of vibration. Results of digital simulation used in the design process are compared with measurements made on an HVDC simulator. Results of both digital simulations and HVDC simulator tests which demonstrate SSDC performance are shown. This research and development effort was sponsored by EPRI under RP1425-1.

  16. Improved Modeling of Structural Joint Damping

    DTIC Science & Technology

    1986-12-01

    Lazan , B . J ., "Review of Structural Damping Mechanisms," Wright Air Development Center Technical Report 59-676, 1961. 14...V |^ j ££^ \\S i r--*\\ S ! § ) —.-l’ V FRICTION MODEL RELOADS _L_i, V RELOO( B M-6 CURVE FRICTION MODEL RELOAD ( B ) k FIGURE 3-9 GROSS... b = the length of the shaft M = moment applied to shaft J = polar moment of inertia G = shear modulus K = JG/ b The polar moment of inertia

  17. Transport description of damped nuclear reactions

    SciTech Connect

    Randrup, J.

    1983-04-01

    Part I is an elementary introduction to the general transport theory of nuclear dynamics. It can be read without any special knowledge of the field, although basic quantum mechanics is required for the formal derivation of the general expression for the transport coefficients. The results can also be used in a wider context than the present one. Part II gives the student an up-to-date orientation about recent progress in the understanding of the angular-momentum variables in damped reactions. The emphasis is here on the qualitative understanding of the physics rather than the, at times somewhat tedious, formal derivations. (WHK)

  18. Bridge feedback for active damping augmentation

    NASA Technical Reports Server (NTRS)

    Chen, G.-S.; Lurie, B. J.

    1990-01-01

    A method is described for broadband damping augmentation of a structural system in which the active members (with feedback control) were developed such that their mechanical input impedance can be electrically adjusted to maximize the energy dissipation rate in the structural system. The active member consists of sensors, an actuator, and a control scheme. A mechanical/electrical analogy is described to model the passive structures and the active members in terms of their impedance representation. As a result, the problem of maximizing dissipative power is analogous to the problem of impedance matching in the electrical network. Closed-loop performance was demonstrated for single- and multiple-active-member controlled truss structure.

  19. Damped coalescence cascade of liquid drops

    NASA Astrophysics Data System (ADS)

    Shim, Suin; Stone, Howard A.

    2017-04-01

    We introduce a regime of the coalescence cascade of a liquid drop—the damped coalescence cascade (DCC)—where the rebound of daughter drops is suppressed. DCC typically occurs when the surface tension difference between the bath and the drop is larger than a critical value. A local Marangoni flow generated in the bath at every pinch-off is expected to accelerate air drainage in the gap between the daughter drop and the bath, and thus leads to suppression of the rebound of the daughter drop. Both scaling arguments and lubrication calculations demonstrate faster air drainage in the presence of local Marangoni flow.

  20. Status of the SLC damping rings

    SciTech Connect

    Hutton, A.M.; Davies-White, W.A.; Delahaye, J.P.; Fieguth, T.H.; Hofmann, A.; Jager, J.; Kloeppel, P.K.; Lee, M.J.; Linebarger, W.A.; Rivkin, L.

    1985-06-01

    Electron beams of full design energy 1.21 GeV and nearly full design intensity 4 x 10/sup 10/ particles/pulse (design 5 x 10/sup 10/) have been extracted from the Stanford Linac and successfully stored in the electron damping ring. Beams of less intensity have been extracted from the ring and reinjected into the Linac. The present intensity limits are not thought to be fundamental. The operating experience with the electron ring and the status of the construction of the positron ring will be discussed. 11 refs., 1 fig., 2 tabs.

  1. Coatings for High-Temperature Vibration Damping of Turbines

    DTIC Science & Technology

    2009-10-01

    damping is provided by both the thin bond- coat and thermal barrier coating (TBC) in TBC coated superalloy system, (ii) the damping from each component...bond- coat and the TBC itself, and (iii) damping from EB-PVD deposited TBCs and platinum-modified nickel aluminide bond- coats occur at the same...closer to chemical equilibrium with existing superalloys than those currently used as bond- coats . Also, depending on the platinum content, the nickel

  2. Critical damping constant of microwave-assisted magnetization switching

    NASA Astrophysics Data System (ADS)

    Yamaji, Toshiki; Arai, Hiroko; Matsumoto, Rie; Imamura, Hiroshi

    2016-02-01

    Microwave-assisted switching of magnetization in a perpendicularly magnetized disk was theoretically studied and special attention was paid to the effect of a damping constant on the switching field. We found that there exists a critical damping constant above which the switching field suddenly increases. We derived an analytical expression of the critical damping constant and showed that it decreases with increasing frequency of the microwave field, while it increases with increasing amplitude of the microwave field and the effective anisotropy field.

  3. Confinement-dependent damping in a layered liquid.

    PubMed

    de Beer, Sissi; van den Ende, Dirk; Mugele, Frieder

    2011-03-23

    We present atomic force microscopy (AFM) measurements of the conservative oscillatory solvation forces and the damping in confined films of octamethylcyclotetrasiloxane using small amplitude modulation with magnetic driving. We find distinct maxima in the interaction damping upon probing the discrete molecular layers, supporting earlier observations of the same phenomenon using AFM with an acoustic driving scheme. The maxima in the damping are located at the same tip-surface separation as the maxima in the conservative oscillatory interaction stiffness.

  4. A unique multipurpose damping circuit for shunt capacitor bank switching

    SciTech Connect

    Sabot, A.; Morin, C.; Guillaume, C.; Pons, A. . Les Renardieres Lab.); Taisne, J.P. . Transmission Division); Pizzo, G.L.; Morf, H.U. )

    1993-07-01

    Considerations on disturbances related to Shunt Capacitor Bank (SCB) switching are summarized and a unique damping circuit able to cope with all of them is proposed. This damping circuit consists of a reactor in parallel with a resistor which is in series with a Metal Oxide Varistor (MOV), the latter being used to switch on the resistor only during transients. The design parameter of this damping circuit are described and the main tests performed are presented.

  5. Existence and damping of toroidicity-induced Alfven eigenmodes

    SciTech Connect

    Mahajan, S.M.; Mett, R.R.

    1991-12-01

    A new method of analyzing the toroidicity-induced Alfven eigenmode (TAE) from kinetic theory is presented. The analysis includes electron parallel dynamics non-perturbatively, an effect which is found to strongly influence the character and damping of the TAE -- contrary to previous theoretical predictions. The normal electron Landau damping of the TAE is found to be higher than previously expected, and may explain recent experimental measurements of the TAE damping coefficient. 11 refs., 1 fig., 1 tab.

  6. Test particle study of Landau damping of steepening magnetosonic waves

    NASA Technical Reports Server (NTRS)

    Matsumoto, H.; Barnes, A.

    1982-01-01

    A test particle study of Landau damping of steepening large-amplitude magnetosonic waves is made. Motions of test particles in a model of a steepening large-amplitude magnetosonic wave are traced. The kinetic energy change of the ensemble of test particles is computed to estimate the effective Landau damping rate of the magnetosonic wave. The numerical results are compared with the linear kinetic theory of Landau damping and interpreted in terms of a simple physical picture for particle trapping.

  7. Damping element for reducing the vibration of an airfoil

    DOEpatents

    Campbell, Christian X; Marra, John J

    2013-11-12

    An airfoil (10) is provided with a tip (12) having an opening (14) to a center channel (24). A damping element (16) is inserted within the opening of the center channel, to reduce an induced vibration of the airfoil. The mass of the damping element, a spring constant of the damping element within the center channel, and/or a mounting location (58) of the damping element within the center channel may be adjustably varied, to shift a resonance frequency of the airfoil outside a natural operating frequency of the airfoil.

  8. Significance of modeling internal damping in the control of structures

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Inman, D. J.

    1992-01-01

    Several simple systems are examined to illustrate the importance of the estimation of damping parameters in closed-loop system performance and stability. The negative effects of unmodeled damping are particularly pronounced in systems that do not use collocated sensors and actuators. An example is considered for which even the actuators (a tip jet nozzle and flexible hose) for a simple beam produce significant damping which, if ignored, results in a model that cannot yield a reasonable time response using physically meaningful parameter values. It is concluded that correct damping modeling is essential in structure control.

  9. Development of Composite Materials with High Passive Damping Properties

    DTIC Science & Technology

    2006-05-15

    SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT 13. SUPPLEMENTARY NOTES 14 . ABSTRACT The structures studied in this ONR...2.1.2 Measures of damping 8 2.1.3 Measurement methods 9 2.2 Damping in Sandwich Structures. 9 2.2.1 Analytical models 10 2.2.2 Damping and damage 14 ...2.2.3 Finite element models 14 2.2.4 Statistical energy analysis method 15 CHAPTER 3 ANALYSIS OF DAMPING IN SANDWICH MATERIALS. 24 3.1 Equation of

  10. Dependence of Kambersky damping on Fermi level and spin orientation

    SciTech Connect

    Qu, T.; Victora, R. H.

    2014-05-07

    Kambersky damping represents the loss of magnetic energy from the electrons to the lattice through the spin orbit interaction. It is demonstrated that, for bcc Fe-based transition metal alloys, the logarithm of the energy loss is proportional to the density of states at the Fermi level. Both inter and intraband damping are calculated for spins at arbitrary angle to the previously examined [001] direction. Although the easy axis 〈100〉 shows isotropic relaxation and achieves the minimum damping value of 0.002, other directions, such as 〈110〉, show substantial anisotropic damping.

  11. Damping of superfluid flow by a thermal cloud.

    PubMed

    Meppelink, R; Koller, S B; Vogels, J M; Stoof, H T C; van der Straten, P

    2009-12-31

    One of the principal signatures of superfluidity is the frictionless flow of a superfluid through another substance. Here, we study the flow of a Bose-Einstein condensate through a thermal cloud and study its damping for different harmonic confinements and temperatures. The damping rates close to the collisionless regime are found to be in good agreement with Landau damping and become smaller for more homogeneous systems. In the hydrodynamic regime, we observe additional damping due to collisions, and we discuss the implications of these findings for superfluidity in this system.

  12. Design and fabrication of integrally damped composite fan blades

    NASA Astrophysics Data System (ADS)

    Kosmatka, John B.; Appuhn, Geoffrey

    1999-06-01

    The design, analysis, and fabrication methods of embedding small viscoelastic damping patches into scaled composite fan blades is presented, where the goal is to improve the blade fatigue characteristics by increasing the damping in the chord-wise modes. This discussion concentrates on improving the damping levels in a research composite shell/titanium spar fan blade, developed by NASA-Lewis and Pratt and Whitney. First, the geometry and material definition of the existing composite fan blade are presented. Second, methods for sizing and locating the damping patch are presented based upon the modal strain energy method. The layered damping patch is composed of outer layers of a TEDLAR (or KAPTON) barrier film, which encompasses a viscoelastic damping material and loose- weave scrim cloth (creep protection). Two different patch sizes and locations are discussed to provide maximum damping as well as optimal damping. Finally, procedures are outlined for fabricating the integrally damped composite fan blades. Fabricated blades will be tested at the NASA-Lewis vacuum facility.

  13. Damping of long-wavelength kinetic alfven fluctuations: linear theory

    SciTech Connect

    Gary, S Peter; Borovsky, Joseph E

    2008-01-01

    The full electromagnetic linear dispersion equation for kinetic Alfven fluctuations in a homogeneous, isotropic, Maxwellian electron-proton plasma is solved numerically in the long wavelength limit. The solutions are summarized by an analytic expression for the damping rate of such modes at propagation sufficiently oblique to the background magnetic field B{sub o} which scales as k{sub {perpendicular}}{sup 2} k{sub {parallel}} where the subscripts denote directions relative to B{sub o}. This damping progressively (although not monotonically) increases with increasing electron {beta}, corresponding to four distinct damping regimes: nonresonant, electron Landau, proton Landau, and proton transit-time damping.

  14. Damping of Crank-Nicolson error oscillations.

    PubMed

    Britz, D; Østerby, O; Strutwolf, J

    2003-07-01

    The Crank-Nicolson (CN) simulation method has an oscillatory response to sharp initial transients. The technique is convenient but the oscillations make it less popular. Several ways of damping the oscillations in two types of electrochemical computations are investigated. For a simple one-dimensional system with an initial singularity, subdivision of the first time interval into a number of equal subintervals (the Pearson method) works rather well, and so does division with exponentially increasing subintervals, where however an optimum expansion parameter must be found. This method can be computationally more expensive with some systems. The simple device of starting with one backward implicit (BI, or Laasonen) step does damp the oscillations, but not always sufficiently. For electrochemical microdisk simulations which are two-dimensional in space and using CN, the use of a first BI step is much more effective and is recommended. Division into subintervals is also effective, and again, both the Pearson method and exponentially increasing subintervals methods are effective here. Exponentially increasing subintervals are often considerably more expensive computationally. Expanding intervals over the whole simulation period, although capable of satisfactory results, for most systems will require more cpu time compared with subdivision of the first interval only.

  15. Characterization of damping in microfibrous material

    NASA Astrophysics Data System (ADS)

    Soobramaney, Pregassen; Flowers, George T.; Dean, Robert N.

    2012-04-01

    MEMS gyroscopes are used in many applications including harsh environments such as high-power, high-frequency acoustic noise. If the latter is at the natural frequency of the gyroscope, the proof mass will be overexcited giving rise to a corrupted gyroscope output. To mitigate the effect of the high-power, high-frequency acoustic noise, it is proposed to use nickel microfibrous sheets as an acoustic damper. For this purpose, the characterization of vibration damping in Nickel microfibrous sheets was examined in the present research effort. The sheets were made from nickel fibers with cellulose as a binding agent using a wet-lay papermaking technique. Sintering was done at 1000 °C to remove all the cellulose giving rise to a porous material. Square sheets of 20 cm were made from three diameters of nickel fibers namely 4, 8, and 12 microns. The sheets were cut into smaller pieces to fit the requirements of a fixture specially designed for this study. The fixture was attached to a LDS V408 shaker with a mass resting on a stack of the microfibrous sheets to simulate transmitted vibration by base motion with the sheet stack acting as a damper. A series of experiments was conducted using these 3 fiber diameters, different number of layers of microfibrous sheets and varying the vibration amplitude. From the collected vibration data, the stiffness and damping ratio of the microfibrous material was characterized.

  16. Quantifying acoustic damping using flame chemiluminescence

    NASA Astrophysics Data System (ADS)

    Boujo, E.; Denisov, A.; Schuermans, B.; Noiray, N.

    2016-12-01

    Thermoacoustic instabilities in gas turbines and aeroengine combustors falls within the category of complex systems. They can be described phenomenologically using nonlinear stochastic differential equations, which constitute the grounds for output-only model-based system identification. It has been shown recently that one can extract the governing parameters of the instabilities, namely the linear growth rate and the nonlinear component of the thermoacoustic feedback, using dynamic pressure time series only. This is highly relevant for practical systems, which cannot be actively controlled due to a lack of cost-effective actuators. The thermoacoustic stability is given by the linear growth rate, which results from the combination of the acoustic damping and the coherent feedback from the flame. In this paper, it is shown that it is possible to quantify the acoustic damping of the system, and thus to separate its contribution to the linear growth rate from the one of the flame. This is achieved by post-processing in a simple way simultaneously acquired chemiluminescence and acoustic pressure data. It provides an additional approach to further unravel from observed time series the key mechanisms governing the system dynamics. This straightforward method is illustrated here using experimental data from a combustion chamber operated at several linearly stable and unstable operating conditions.

  17. Identification of the damping properties of rigid isotropic materials by studying the damping flexural vibrations of test specimens

    NASA Astrophysics Data System (ADS)

    Gyunal, I.; Paimushin, V. N.; Firsov, V. A.; Shishkin, V. M.

    2017-03-01

    A technique for determining the damping properties of a rigid isotropic material from the experimental data on the damping capacity of elongated cantilever-fixed test specimens due to the internal and external aerodynamic damping is proposed. The following two methods for eliminating the aerodynamic damping component are considered: the extrapolation of the data on the damping capacity of a series of test specimens of different widths to the point corresponding to the zero width and the theoretical-experimental approach. The damping properties of the material are determined by the vibration logarithmic decrement depending on the amplitude of the linear deformation. This dependence is represented by a power polynomial. The polynomial coefficients are determined from the minimum condition of the goal function for the positive logarithmic decrement of the material vibrations. These coefficients are sought at the reference point by repeatedly solving the direct problem of determining the damping capacity of the test specimen from the given damping properties of the material. An example is considered to illustrate the identification of the damping properties of steel St.3.

  18. Vibrational resonance in Duffing systems with fractional-order damping.

    PubMed

    Yang, J H; Zhu, H

    2012-03-01

    The phenomenon of vibrational resonance (VR) is investigated in over- and under-damped Duffing systems with fractional-order damping. It is found that the factional-order damping can induce change in the number of the steady stable states and then lead to single- or double-resonance behavior. Compared with vibrational resonance in the ordinary systems, the following new results are found in the fractional-order systems. (1) In the overdamped system with double-well potential and ordinary damping, there is only one kind of single-resonance, whereas there are double-resonance and two kinds of single-resonance for the case of fractional-order damping. The necessary condition for these new resonance behaviors is the value of the fractional-order satisfies α > 1. (2) In the overdamped system with single-well potential and ordinary damping, there is no resonance, whereas there is a single-resonance for the case of fractional-order damping. The necessary condition for the new result is α > 1. (3) In the underdamped system with double-well potential and ordinary damping, there are double-resonance and one kind of single-resonance, whereas there are double-resonance and two kinds of single-resonance for the case of fractional-order damping. The necessary condition for the new single-resonance is α < 1. (4) In the underdamped system with single-well potential, there is at most a single-resonance existing for both the cases of ordinary and fractional-order damping. In the underdamped systems, varying the value of the fractional-order is equivalent to change the damping parameter for some cases.

  19. Bounce-harmonic Landau Damping of Plasma Waves

    NASA Astrophysics Data System (ADS)

    Anderegg, Francois

    2015-11-01

    We present measurement of plasma wave damping, spanning the temperature regimes of direct Landau damping, bounce-harmonic Landau damping, inter-species drag damping, and viscous damping. Direct Landau damping is dominant at high temperatures, but becomes negligible as v damping, controlled by an applied ``squeeze'' potential, which generates harmonics in the wave potential and in the particle dynamics. A particle moving in z experiences a non-sinusoidal mode potential caused by the squeeze, producing high spatial harmonics with lower phase velocity. These harmonics are Landau damped even when the mode phase velocity vph is large compared to the thermal velocity v , since the nth harmonic is resonant with a particle bouncing at velocity vb =vph / n . Here we increase the bounce harmonics through applied squeeze potential; but some harmonics are always present in finite length systems. For our centered squeeze geometry, theory shows that only odd harmonics are generated, and predicts the Landau damping rate from vph / n . Experimentally, the squeeze potential increases the wave damping and reduces its frequency. The frequency shift occurs because the squeeze potential reduces the number of particle where the mode velocity is the largest, therefore reducing the mode frequency. We observe an increase in the damping proportional to Vs2,and a frequency reduction proportional to Vs , in quantitative agreement with theory. Wave-coherent laser induced fluorescence allows direct observation of bounce resonances on the particle distribution, here predominantly at vph / 3 . A clear increase of the bounce harmonics is visible on the particle distribution when the squeeze potential is applied. Supported by NSF Grant PHY-1414570, and DOE Grants DE-SC0002451 and DE-SC0008693.

  20. Building Awareness.

    ERIC Educational Resources Information Center

    Meilach, Dona Z.

    2001-01-01

    Discusses the importance of developing students' building awareness by exploring logos, or buildings that symbolize a country, to learn about architecture and the cultures in different countries. Explores categories of buildings. Includes examples of logos from around the world. (CMK)

  1. A Lanczos-chain driven approach for calculating damped vibrational configuration interaction response functions

    NASA Astrophysics Data System (ADS)

    Hansen, Mikkel Bo; Seidler, Peter; Győrffy, Werner; Christiansen, Ove

    2010-09-01

    We present an approach based on the Lanczos method for calculating the vibrational configuration interaction response functions necessary for evaluating the pure vibrational contributions to the polarizabilities and first hyperpolarizabilities of molecules. The method iteratively builds a tridiagonal representation of the central response matrix, which is subsequently used for solving the response equations. From the same chain, the response functions can be evaluated approximately for any frequency as well as using any complex damping factor. Applications to formaldehyde, cyclopropene, and uracil illustrate the concepts presented.

  2. Simulations of the Electron Cloud Builld Up and Instabilities for Various ILC Damping Ring Configurations

    SciTech Connect

    Pivi, Mauro; Raubenheimer, Tor O.; Wang, Lanfa; Ohmi, Kazuhito; Wanzenberg, Rainer; Wolski, Andrzej; /Liverpool U. /Cockcroft Inst. Accel. Sci. Tech.

    2007-03-12

    In the beam pipe of the positron damping ring of the International Linear Collider (ILC), an electron cloud may be first produced by photoelectrons and ionization of residual gases and then increased by the secondary emission process. This paper reports the assessment of electron cloud effects in a number of configuration options for the ILC baseline configuration. Careful estimates were made of the secondary electron yield (sometimes in the literature also referred as secondary emission yield SEY or {delta}, with a peak value {delta}{sub max}) threshold for electron cloud build-up, and the related single- and coupled-bunch instabilities, as a function of beam current and surface properties for a variety of optics designs. When the configuration for the ILC damping rings was chosen at the end of 2005, the results from these studies were important considerations. On the basis of the joint theoretical and experimental work, the baseline configuration currently specifies a pair of 6 km damping rings for the positron beam, to mitigate the effects of the electron cloud that could present difficulties in a single 6 km ring. However, since mitigation techniques are now estimated to be sufficiently mature, a reduced single 6-km circumference is presently under consideration so as to reduce costs.

  3. Management of seedling damping-off of alfalfa

    USDA-ARS?s Scientific Manuscript database

    A vigorous and productive alfalfa stand starts with strong and uniform seedling establishment. Seed rot and seedling damping-off are a significant cause of poor stand establishment in wet soils. A number of organisms cause seed rot and seedling damping-off including several species of Pythium. As a ...

  4. Variable hybrid piezoelectric damping based on control power requirement

    NASA Astrophysics Data System (ADS)

    Adachi, Kazuhiko; Awakura, Yoshihumi; Iwatsubo, Takuzo

    2001-07-01

    A new hybrid piezoelectric damping system with switching control are proposed here in order to reduce the control power requirement of piezoelectrical damping augmentation for flexible structures. There are two types of hybrid piezoelectric damping; one is a series type (integrated type, type I) where piezoelectric actuators are actively driven by the external voltage source with the passive tuned RL shunting circuit in series. The other is a separated type in collocated condition (type II) where the external voltage sources and the passive tuned RL shunting circuits are separated from each other, and both piezoelectric actuators to be used to the active and passive dampings are collocated on the host structure. The types I - II switching rule of the variable hybrid piezoelectric damping is determined by the vibration condition on the host structure. Availability of the proposed variable hybrid piezoelectric damping system is experimentally demonstrated by using a simple cantilever beam example with surface bonded piezo-elements. The experimental results indicate that the variable hybrid piezoelectric damping system is effective comparing the single type of hybrid piezoelectric damping system (type I or type II) from the viewpoint of active control power requirement.

  5. The Study of Damped Harmonic Oscillations Using an Electronic Counter

    ERIC Educational Resources Information Center

    Wadhwa, Ajay

    2009-01-01

    We study damped harmonic oscillations in mechanical systems like the loaded spring and simple pendulum with the help of an oscillation measuring electronic counter. The experimental data are used in a software program that solves the differential equation for damped vibrations of any system and determines its position, velocity and acceleration as…

  6. The Study of Damped Harmonic Oscillations Using an Electronic Counter

    ERIC Educational Resources Information Center

    Wadhwa, Ajay

    2009-01-01

    We study damped harmonic oscillations in mechanical systems like the loaded spring and simple pendulum with the help of an oscillation measuring electronic counter. The experimental data are used in a software program that solves the differential equation for damped vibrations of any system and determines its position, velocity and acceleration as…

  7. Component modes damping assignment methodology for articulated, multiflexible body structures

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.

    1993-01-01

    To simulate the dynamical motion of articulated, multiflexible body structures, one can use multibody simulation packages such as DISCOS. To this end, one must supply appropriate reduced-order models for all of the flexible components involved. The component modes projection and assembly model reduction (COMPARE) methodology is one way to construct these reduced-order component models, which when reassembled capture important system input-to-output mapping of the full-order model at multiple system configurations of interest. In conjunction, we must also supply component damping matrices which when reassembled generate a system damping matrix that has certain desirable properties. The problem of determining the damping factors of components' modes to achieve a given system damping matrix is addressed here. To this end, we must establish from first principles a matrix-algebraic relation between the system's modal damping matrix and the components' modal damping matrices. An unconstrained/constrained optimization problem can then be formulated to determine the component modes' damping factors that best satisfy that matrix-algebraic relation. The effectiveness of the developed methodology, called ModeDamp, has been successfully demonstrated on a high-order, finite element model of the Galileo spacecraft.

  8. Translational damping on high-frequency flapping wings

    NASA Astrophysics Data System (ADS)

    Parks, Perry A.

    Flapping fliers such as insects and birds depend on passive translational and rotational damping to terminate quick maneuvers and to provide a source of partial stability in an otherwise unstable dynamic system. Additionally, passive translational and rotational damping reduce the amount of active kinematic changes that must be made to terminate maneuvers and maintain stability. The study of flapping-induced damping phenomena also improves the understanding of micro air vehicle (MAV) dynamics needed for the synthesis of effective flight control strategies. Aerodynamic processes which create passive translational and rotational damping as a direct result of symmetric flapping with no active changes in wing kinematics have been previously studied and were termed flapping counter-force (FCF) and flapping counter-torque (FCT), respectively. In this first study of FCF measurement in air, FCF generation is measured using a pendulum system designed to isolate and measure the relationship of translational flapping-induced damping with wingbeat frequency for a 2.86 gram mechanical flapper equipped with real cicada wings. Analysis reveals that FCF generation and wingbeat frequency are directly proportional, as expected from previous work. The quasi-steady FCF model using Blade-Element-Theory is used as an estimate for translational flapping-induced damping. In most cases, the model proves to be accurate in predicting the relationship between flapping-induced damping and wingbeat frequency. "Forward-backward" motion proves to have the strongest flapping-induced damping while "up-down" motion has the weakest.

  9. Interdigitated interdigital transducer for surface elastometry of soft damping tissue.

    PubMed

    Danicki, Eugene; Nowicki, Andrzej; Tasinkevych, Yuriy

    2013-06-01

    Measurement of the shear elastic constant of soft and highly damping tissue of high Poisson ratio is quite a challenging task. It is proposed to evaluate shear wave velocity and damping of tissue by measuring the shear skimming bulk waves using one interdigitated interdigital transducer on a piezoelectric layer, such as polyvinylidene fluoride, applied to the surface of the small tissue sample.

  10. Dependence of kink oscillation damping on the amplitude

    NASA Astrophysics Data System (ADS)

    Goddard, C. R.; Nakariakov, V. M.

    2016-05-01

    Context. Kink oscillations of coronal loops are one of the most intensively studied oscillatory phenomena in the solar corona. In the large-amplitude rapidly damped regime, these oscillations are observed to have a low quality factor with only a few cycles of oscillation detected before they are damped. The specific mechanism responsible for rapid damping is commonly accepted to be associated with the linear coupling between collective kink oscillations and localised torsional oscillations, the phenomenon of resonant absorption of the kink mode. The role of finite amplitude effects, however, is still not clear. Aims: We investigated the empirical dependence of the kink oscillation damping time and its quality factor, which is defined as the ratio of damping time to oscillation period, on the oscillation amplitude. Methods: We analysed decaying kink oscillation events detected previously with TRACE, SDO/AIA and and STEREO/EUVI in the extreme ultraviolet (EUV) 171 Å band. Results: We found that the ratio of the kink oscillation damping time to the oscillation period systematically decreases with the oscillation amplitude. We approximated the quality factor dependence on the oscillation displacement amplitude via the power-law dependence with the exponent of -1/2, however we stress that this is a by-eye estimate, and a more rigorous estimation of the scaling law requires more accurate measurements and increased statistics. We conclude that damping of kink oscillations of coronal loops depends on the oscillation amplitude, indicating the possible role of non-linear mechanisms for damping.

  11. Rhizoctonia damping-off stem canker and root rot

    USDA-ARS?s Scientific Manuscript database

    Rhizoctonia solani has been reported to cause damping-off and root rot of rhododendrons and azaleas. Damping-off often includes groups of dying and dead seedlings. Decline of rooted plants in containers results from both root rot and stem necrosis below or above the soil line. Root rot is usually no...

  12. Experimental Spin Testing of Integrally Damped Composite Plates

    NASA Technical Reports Server (NTRS)

    Kosmatka, John

    1998-01-01

    The experimental behavior of spinning laminated composite pretwisted plates (turbo-fan blade-like) with small (less than 10% by volume) integral viscoelastic damping patches was investigated at NASA-Lewis Research Center. Ten different plate sets were experimentally spin tested and the resulting data was analyzed. The first-four plate sets investigated tailoring patch locations and definitions to damp specific modes on spinning flat graphite/epoxy plates as a function of rotational speed. The remaining six plate sets investigated damping patch size and location on specific modes of pretwisted (30 degrees) graphite/epoxy plates. The results reveal that: (1) significant amount of damping can be added using a small amount of damping material, (2) the damped plates experienced no failures up to the tested 28,000 g's and 750,000 cycles, (3) centrifugal loads caused an increase in bending frequencies and corresponding reductions in bending damping levels that are proportional to the bending stiffness increase, and (4) the centrifugal loads caused a decrease in torsion natural frequency and increase in damping levels of pretwisted composite plates.

  13. Nonlinear Landau damping in quark-gluon plasma

    NASA Astrophysics Data System (ADS)

    Xiaofei, Zhang; Jiarong, Li

    1995-08-01

    The semiclassical kinetic equations for the quark-gluon plasma (QGP) are discussed by the multiple time-scale method. The mechanism of nonlinear Landau damping owing to non-Abelian and nonlinear wave-particle interactions in QGP is investigated, and the nonlinear Landau damping rate for the longitudinal color eigenwaves in the long-wavelength limit is calculated.

  14. Flux-driven algebraic damping of m = 1 diocotron mode

    NASA Astrophysics Data System (ADS)

    Chim, Chi Yung; O'Neil, Thomas M.

    2016-07-01

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 1 diocotron modes. Transport due to small field asymmetries produces a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius r = Rw at the wall of the trap. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from, spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This paper explains with analytic theory the new algebraic damping due to particle transport by both mobility and diffusion. As electrons are swept around the "cat's eye" orbits of the resonant wave-particle interaction, they form a dipole (m = 1) density distribution. From this distribution, the electric field component perpendicular to the core displacement produces E × B-drift of the core back to the axis, that is, damps the m = 1 mode. The parallel component produces drift in the azimuthal direction, that is, causes a shift in the mode frequency.

  15. Flux-driven algebraic damping of m = 1 diocotron mode

    NASA Astrophysics Data System (ADS)

    Chim, Chi Yung; O'Neil, Thomas

    2015-11-01

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 1 diocotron modes. Transport due to small field asymmetries produce a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius rres, where f = mfE × B (rres) . The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This poster explains with analytic theory and simulations the new algebraic damping due to both mobility and diffusive fluxes. As electrons are swept around the ``cat's eye'' orbits of resonant wave-particle interaction, they form a dipole (m = 1) density distribution, and the electric field from this distribution produces an E × B drift of the core back to the axis, i.e. damps the m = 1 mode. Supported by National Science Foundation Grant PHY-1414570.

  16. Self-damping cementitious composites with multi-layer graphene

    NASA Astrophysics Data System (ADS)

    Ruan, Yanfeng; Zhou, Daocheng; Sun, Shengwei; Wu, Xinyi; Yu, Xun; Hou, Jilin; Dong, Xufeng; Han, Baoguo

    2017-07-01

    Cementitious composites are quasi-brittle and susceptible to damage under dynamic loads. The addition of nanoscale fillers into cementitious composites is an effective approach to address this issue. In this paper, multi-layer graphenes (MLGs) are incorporated into cementitious composites to enhance its damping property. The underlying modification mechanism of MLGs to cementitous composites is also investigated. Experimental results showed that the addition of MLGs can effectively modify the damping property of cementitious composites. Compared with cementitious composites without MLGs, the damping ratio of cementitious composites filled with 1% and 5% of MLGs increases by 16.22% and 45.73%, respectively. The improvement of MLGs to damping property of cementitious composites can be attributed to the interlayer slip of MLGs, viscous friction between MLGs and matrix, and excellent thermal conductivity of MLGs. Moreover, the damping ratio measured by time-domain exponential decay method and frequency-domain half-power bandwidth method is consistent.

  17. Nonlinear damping model for flexible structures. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Zang, Weijian

    1990-01-01

    The study of nonlinear damping problem of flexible structures is addressed. Both passive and active damping, both finite dimensional and infinite dimensional models are studied. In the first part, the spectral density and the correlation function of a single DOF nonlinear damping model is investigated. A formula for the spectral density is established with O(Gamma(sub 2)) accuracy based upon Fokker-Planck technique and perturbation. The spectral density depends upon certain first order statistics which could be obtained if the stationary density is known. A method is proposed to find the approximate stationary density explicitly. In the second part, the spectral density of a multi-DOF nonlinear damping model is investigated. In the third part, energy type nonlinear damping model in an infinite dimensional setting is studied.

  18. A Physical Molecular Mechanics Method for Damped Dispersion.

    PubMed

    Verma, Pragya; Wang, Bo; Fernandez, Laura E; Truhlar, Donald G

    2017-03-22

    Damped dispersion can be a significant component of the interaction energy in many physical and chemical processes, for example, physisorption and noncovalent complexation. For physically interpreting and modeling such processes, it is convenient to have an analytic method to calculate damped dispersion that is readily applicable across the entire periodic table. Of the available methods to calculate damped dispersion energy for interacting systems with overlapping charge distributions, we select symmetry-adapted perturbation theory (SAPT) as providing a reasonable definition, and of the possible analytic forms, we choose the D3(BJ) method. However, the available parameterizations of D3(BJ) include not only damped dispersion energy but also corrections for errors in specific exchange-correlation functionals. Here we present a parameterization that provides a physical measure of damped dispersion without such density functional corrections. The method generalizes an earlier method of Pernal and coworkers to all elements from hydrogen to plutonium.

  19. Comparison of damping treatments for gas turbine blades

    NASA Astrophysics Data System (ADS)

    Gordon, Robert W.; Hollkamp, Joseph J.

    1996-05-01

    High frequency vibration of gas turbine fan blades is a high cycle fatigue concern. Friction damping devices are ineffective in suppressing high frequency vibration modes and external damping treatments are plagued by creep concerns. An alternative approach is to apply viscoelastic material internally in the blades. In this paper, an analytical comparison of internal damping treatments for fan blades is presented. The fan blade is modeled as a solid, flat, cantilevered titanium plate. Internal portions are removed producing cavities that are filled with viscoelastic material. Configurations with one, two, and three cavities are modeled using the modal strain energy method in conjunction with finite element analysis to estimate damping. Results show that appreciable damping levels for high frequency modes are possible with stiff viscoelastic material. Other design criteria are also considered. Results indicate that the hydrostatic load from the viscoelastic material on the cavity walls may be a concern.

  20. Damping of thermal acoustic oscillations in hydrogen systems

    NASA Astrophysics Data System (ADS)

    Gu, Youfan; Timmerhaus, Klaus D.

    Acoustic waves initiated by a large temperature gradient along a tube are defined as thermal acoustic oscillations (TAOs). These oscillations have been damped by introducing such sound absorbing techniques as acoustic filters, resonators, etc.. These devices serve as an acoustic sink that is used to absorb or dissipate the acoustic energy thereby eliminating or damping such oscillations. Several empirical damping techniques, such as attaching a resonator as a side branch or inserting a wire in the tube, have been developed in the past and have provided reasonable success. However, the effect of connecting tube radius, length, and resonator volume on the damping of thermal acoustic oscillations has not been evaluated quantitatively. Further, these methods have not been effective when the oscillating tube radius was relatively large. Detailed theoretical analyses of these techniques including a newly developed method for damping oscillations in a tube of relatively large radius are provided in this presentation.

  1. Impact of Damping Uncertainty on SEA Model Response Variance

    NASA Technical Reports Server (NTRS)

    Schiller, Noah; Cabell, Randolph; Grosveld, Ferdinand

    2010-01-01

    Statistical Energy Analysis (SEA) is commonly used to predict high-frequency vibroacoustic levels. This statistical approach provides the mean response over an ensemble of random subsystems that share the same gross system properties such as density, size, and damping. Recently, techniques have been developed to predict the ensemble variance as well as the mean response. However these techniques do not account for uncertainties in the system properties. In the present paper uncertainty in the damping loss factor is propagated through SEA to obtain more realistic prediction bounds that account for both ensemble and damping variance. The analysis is performed on a floor-equipped cylindrical test article that resembles an aircraft fuselage. Realistic bounds on the damping loss factor are determined from measurements acquired on the sidewall of the test article. The analysis demonstrates that uncertainties in damping have the potential to significantly impact the mean and variance of the predicted response.

  2. Damping of thermal acoustic oscillations in hydrogen systems

    NASA Technical Reports Server (NTRS)

    Gu, Youfan; Timmerhaus, Klaus D.

    1991-01-01

    Acoustic waves initiated by a large temperature gradient along a tube are defined as thermal acoustic oscillations (TAOs). These oscillations have been damped by introducing such sound absorbing techniques as acoustic filters, resonators, etc.. These devices serve as an acoustic sink that is used to absorb or dissipate the acoustic energy thereby eliminating or damping such oscillations. Several empirical damping techniques, such as attaching a resonator as a side branch or inserting a wire in the tube, have been developed in the past and have provided reasonable success. However, the effect of connecting tube radius, length, and resonator volume on the damping of thermal acoustic oscillations has not been evaluated quantitatively. Further, these methods have not been effective when the oscillating tube radius was relatively large. Detailed theoretical analyses of these techniques including a newly developed method for damping oscillations in a tube of relatively large radius are provided in this presentation.

  3. Prevalence of dampness and mold in European housing stock.

    PubMed

    Haverinen-Shaughnessy, Ulla

    2012-09-01

    An assessment of the prevalence of dampness and mold in European housing stock was carried out. It is based on general indicators of dampness and mold in dwellings reported in the literature. The assessment relies on recent studies, taking into account regional and climatic differences, as well as differences in study design, methodology, and definitions. Data were available from 31 European countries. Weighted prevalence estimates are 12.1% for damp, 10.3% for mold, 10.0% for water damage, and 16.5% for a combination of any one or more indicators. Significant (up to 18%) differences were observed for dampness and mold prevalence estimates depending on survey factors, region, and climate. In conclusion, dampness and/or mold problems could be expected to occur in one of every six of the dwellings in Europe. Prevalence and occurrence of different types of problems may vary across geographical areas, which can be partly explained by differences in climate.

  4. Damping strapdown inertial navigation system based on a Kalman filter

    NASA Astrophysics Data System (ADS)

    Zhao, Lin; Li, Jiushun; Cheng, Jianhua; Hao, Yong

    2016-11-01

    A damping strapdown inertial navigation system (DSINS) can effectively suppress oscillation errors of strapdown inertial navigation systems (SINSs) and improve the navigation accuracy of SINSs. Aiming at overcoming the disadvantages of traditional damping methods, a DSINS, based on a Kalman filter (KF), is proposed in this paper. Using the measurement data of accelerometers and calculated navigation parameters during the navigation process, the expression of the observation equation is derived. The calculation process of the observation in both the internal damping state and the external damping state is presented. Finally, system oscillation errors are compensated by a KF. Simulation and test results show that, compared with traditional damping methods, the proposed method can reduce system overshoot errors and shorten the convergence time of oscillation errors effectively.

  5. Vibrational modes and damping in the cochlear partition

    NASA Astrophysics Data System (ADS)

    O'Maoiléidigh, Dáibhid; Hudspeth, A. J.

    2015-12-01

    It has been assumed in models of cochlear mechanics that the primary role of the cochlear active process is to counteract the damping of the basilar membrane, the vibration of which is much larger in a living animal than post mortem. Recent measurements of the relative motion between the reticular lamina and basilar membrane imply that this assumption is incorrect. We propose that damping is distributed throughout the cochlear partition rather than being concentrated in the basilar membrane. In the absence of significant damping, the cochlear partition possesses three modes of vibration, each associated with its own locus of Hopf bifurcations. Hair-cell activity can amplify any of these modes if the system's operating point lies near the corresponding bifurcation. The distribution of damping determines which mode of vibration predominates. For physiological levels of damping, only one mode produces a vibration pattern consistent with experimental measurements of relative motion and basilar-membrane motion.

  6. Effects of ion motion on linear Landau damping

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Sheng, Zheng-Ming; Kong, Xiang-Mu; Su, Fu-Fang

    2017-02-01

    The effects of ion motion on Landau damping has been studied by the use of one-dimensional Vlasov-Poisson simulation. It is shown that the ion motion may significantly change the development of the linear Landau damping. When the ion mass is multiple of proton mass, its motion will halt the linear Landau damping at some time due to the excitation of ion acoustic waves. The latter will dominate the system evolution at the later stage and hold a considerable fraction of the total energy in the system. With very small ion mass, such as in electron-positron plasma, the ion motion can suppress the linear Landau damping very quickly. When the initial field amplitude is relatively high such as with the density perturbation amplitude δn/n0 > 0.1, the effect of ion motion on Landau damping is found to be weak or even ignorable.

  7. Magnetic damping: domain wall dynamics versus local ferromagnetic resonance.

    PubMed

    Weindler, T; Bauer, H G; Islinger, R; Boehm, B; Chauleau, J-Y; Back, C H

    2014-12-05

    Magnetic relaxation is one of the dominating features of magnetization dynamics. Depending on the magnetic structure and the experimental approach, different magnitudes of the damping parameter are reported even for a given material. In this study, we experimentally address this issue by accessing the damping parameter in the same magnetic nanotracks using different approaches: local ferromagnetic resonance (α=0.0072) and field-driven domain wall dynamics (α=0.023). The experimental results cannot fully be accounted for by modeling only roughness in micromagnetic simulations. Consequently, we have included nonlocal texture induced damping to the micromagnetic code. We find excellent agreement with the observed increased damping in the vortex structures for the same input Gilbert alpha when texture-induced nonlocal damping is included.

  8. Passively Damped Laminated Piezoelectric Shell Structures with Integrated Electric Networks

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitris A.

    1999-01-01

    Multi-field mechanics are presented for curvilinear piezoelectric laminates interfaced with distributed passive electric components. The equations of motion for laminated piezoelectric shell structures with embedded passive electric networks are directly formulated and solved using a finite element methodology. The modal damping and frequencies of the piezoelectric shell are calculated from the poles of the system. Experimental and numerical results are presented for the modal damping and frequency of composite beams with a resistively shunted piezoceramic patch. The modal damping and frequency of plates, cylindrical shells and cylindrical composite blades with piezoelectric-resistor layers are predicted. Both analytical and experimental studies illustrate a unique dependence of modal damping and frequencies on the shunting resistance and show the effect of structural shape and curvature on piezoelectric damping.

  9. Passively Shunted Piezoelectric Damping of Centrifugally-Loaded Plates

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten P.; Provenza, Andrew J.; Trudell, Jeffrey J.; Min, James B.

    2009-01-01

    Researchers at NASA Glenn Research Center have been investigating shunted piezoelectric circuits as potential damping treatments for turbomachinery rotor blades. This effort seeks to determine the effects of centrifugal loading on passively-shunted piezoelectric - damped plates. Passive shunt circuit parameters are optimized for the plate's third bending mode. Tests are performed both non-spinning and in the Dynamic Spin Facility to verify the analysis, and to determine the effectiveness of the damping under centrifugal loading. Results show that a resistive shunt circuit will reduce resonant vibration for this configuration. However, a tuned shunt circuit will be required to achieve the desired damping level. The analysis and testing address several issues with passive shunt circuit implementation in a rotating system, including piezoelectric material integrity under centrifugal loading, shunt circuit implementation, and tip mode damping.

  10. Flow damping due to stochastization of the magnetic field

    PubMed Central

    Ida, K.; Yoshinuma, M.; Tsuchiya, H.; Kobayashi, T.; Suzuki, C.; Yokoyama, M.; Shimizu, A.; Nagaoka, K.; Inagaki, S.; Itoh, K.; Akiyama, T.; Emoto, M.; Evans, T.; Dinklage, A.; Du, X.; Fujii, K.; Goto, M.; Goto, T.; Hasuo, M.; Hidalgo, C.; Ichiguchi, K.; Ishizawa, A.; Jakubowski, M.; Kamiya, K.; Kasahara, H.; Kawamura, G.; Kato, D.; Kobayashi, M.; Morita, S.; Mukai, K.; Murakami, I.; Murakami, S.; Narushima, Y.; Nunami, M.; Ohdach, S.; Ohno, N.; Osakabe, M.; Pablant, N.; Sakakibara, S.; Seki, T.; Shimozuma, T.; Shoji, M.; Sudo, S.; Tanaka, K.; Tokuzawa, T.; Todo, Y.; Wang, H.; Yamada, H.; Takeiri, Y.; Mutoh, T.; Imagawa, S.; Mito, T.; Nagayama, Y.; Watanabe, K. Y.; Ashikawa, N.; Chikaraishi, H.; Ejiri, A.; Furukawa, M.; Fujita, T.; Hamaguchi, S.; Igami, H.; Isobe, M.; Masuzaki, S.; Morisaki, T.; Motojima, G.; Nagasaki, K.; Nakano, H.; Oya, Y.; Suzuki, Y.; Sakamoto, R.; Sakamoto, M.; Sanpei, A.; Takahashi, H.; Tokitani, M.; Ueda, Y.; Yoshimura, Y.; Yamamoto, S.; Nishimura, K.; Sugama, H.; Yamamoto, T.; Idei, H.; Isayama, A.; Kitajima, S.; Masamune, S.; Shinohara, K.; Bawankar, P. S.; Bernard, E.; von Berkel, M.; Funaba, H.; Huang, X. L.; Ii, T.; Ido, T.; Ikeda, K.; Kamio, S.; Kumazawa, R.; Moon, C.; Muto, S.; Miyazawa, J.; Ming, T.; Nakamura, Y.; Nishimura, S.; Ogawa, K.; Ozaki, T.; Oishi, T.; Ohno, M.; Pandya, S.; Seki, R.; Sano, R.; Saito, K.; Sakaue, H.; Takemura, Y.; Tsumori, K.; Tamura, N.; Tanaka, H.; Toi, K.; Wieland, B.; Yamada, I.; Yasuhara, R.; Zhang, H.; Kaneko, O.; Komori, A.

    2015-01-01

    The driving and damping mechanism of plasma flow is an important issue because flow shear has a significant impact on turbulence in a plasma, which determines the transport in the magnetized plasma. Here we report clear evidence of the flow damping due to stochastization of the magnetic field. Abrupt damping of the toroidal flow associated with a transition from a nested magnetic flux surface to a stochastic magnetic field is observed when the magnetic shear at the rational surface decreases to 0.5 in the large helical device. This flow damping and resulting profile flattening are much stronger than expected from the Rechester–Rosenbluth model. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that the flow damping is due to the change in the non-diffusive term of momentum transport. PMID:25569268

  11. Eddy-current-damped microelectromechanical switch

    DOEpatents

    Christenson, Todd R.; Polosky, Marc A.

    2007-10-30

    A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction).

  12. Eddy-current-damped microelectromechanical switch

    DOEpatents

    Christenson, Todd R.; Polosky, Marc A.

    2009-12-15

    A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction).

  13. Forced oscillations in quadratically damped systems

    NASA Technical Reports Server (NTRS)

    Bayliss, A.

    1978-01-01

    Bayliss (1975) has studied the question whether in the case of linear differential equations the relationship between the stability of the homogeneous equations and the existence of almost periodic solutions to the inhomogeneous equation is preserved by finite difference approximations. In the current investigation analogous properties are considered for the case in which the damping is quadratic rather than linear. The properties of the considered equation for arbitrary forcing terms are examined and the validity is proved of a theorem concerning the characteristics of the unique solution. By using the Lipschitz continuity of the mapping and the contracting mapping principle, almost periodic solutions can be found for perturbations of the considered equation. Attention is also given to the Lipschitz continuity of the solution operator and the results of numerical tests which have been conducted to test the discussed theory.

  14. Magnetomechanical damping and magnetoelastic hysteresis in permalloy

    NASA Astrophysics Data System (ADS)

    Ercuta, A.; Mihalca, I.

    2002-11-01

    The inverse Wiedemann effect (IWE) consisting in longitudinal magnetization reversals was detected with a cylindrical permalloy layer subjected to circular DC magnetic fields while performing low frequency (~1 Hz) free torsion oscillations. Hysteresis occurring in the magnetization vs elastic strain dependence (the `magnetoelastic hysteresis') suggested irreversible processes activated mechanically. Joint vibration and magnetization time records were carried out by means of an experimental set-up including inverted pendulum and conventional integrating fluxmeter, in order to compare the relative energy losses ascribed to the magnetomechanical damping (MMD) and to the magnetoelastic hysteresis, respectively. The experimental results clearly pointed out a close connection between IWE and MMD providing evidence that, when simultaneously examined, both effects reflect the same basic phenomenon: the irreversible magnetization changes induced by the elastic strain.

  15. Vibration damping with active carbon fiber structures

    NASA Astrophysics Data System (ADS)

    Neugebauer, Reimund; Kunze, Holger; Riedel, Mathias; Roscher, Hans-Jürgen

    2007-04-01

    This paper presents a mechatronic strategy for active reduction of vibrations on machine tool struts or car shafts. The active structure is built from a carbon fiber composite with embedded piezofiber actuators that are composed of piezopatches based on the Macro Fiber Composite (MFC) technology, licensed by NASA and produced by Smart Material GmbH in Dresden, Germany. The structure of these actuators allows separate or selectively combined bending and torsion, meaning that both bending and torsion vibrations can be actively absorbed. Initial simulation work was done with a finite element model (ANSYS). This paper describes how state space models are generated out of a structure based on the finite element model and how controller codes are integrated into finite element models for transient analysis and the model-based control design. Finally, it showcases initial experimental findings and provides an outlook for damping multi-mode resonances with a parallel combination of resonant controllers.

  16. Exact Damping for Relativistic Plasma Waves

    NASA Astrophysics Data System (ADS)

    Swanson, D. G.

    2000-10-01

    The damping coefficient for a relativistic plasma may be reduced to a single integral with no approximations through use of the Newberger sum rules when k_z=0. Expanding the integral in a series, the leading term agrees with the leading term of the weak relativistic function F_7/2(z), but the remaining terms are not alike. The single expansion parameter is proportional to λ z, indicating that the result may NOT be accurately expressed as a series involving products of Bessel functions of argument λ times functions F_q(z). Expressions for the imaginary parts of all dielectric tensor elements will be presented. The real parts of the tensor elements are not as simple, but because the elements are analytic, they must likewise be modified.

  17. Pair creation: Back reactions and damping

    SciTech Connect

    Bloch, J. C. R.; Mizerny, V. A.; Prozorkevich, A. V.; Roberts, C. D.; Schmidt, S. M.; Smolyansky, S. A.; Vinnik, D. V.

    1999-12-01

    We solve the quantum Vlasov equation for fermions and bosons, incorporating spontaneous pair creation in the presence of back reactions and collisions. Pair creation is initiated by an external impulse field and the source term is non-Markovian. A simultaneous solution of Maxwell's equation in the presence of feedback yields an internal current and electric field that exhibit plasma oscillations with a period {tau}{sub pl}. Allowing for collisions, these oscillations are damped on a time scale {tau}{sub r} determined by the collision frequency. Plasma oscillations cannot affect the early stages of the formation of a quark-gluon plasma unless {tau}{sub r}>>{tau}{sub pl} and {tau}{sub pl}{approx}1/{lambda}{sub QCD}{approx}1 fm/c. (c) 1999 The American Physical Society.

  18. Radiation damping in atomic photonic crystals.

    PubMed

    Horsley, S A R; Artoni, M; La Rocca, G C

    2011-07-22

    The force exerted on a material by an incident beam of light is dependent upon the material's velocity in the laboratory frame of reference. This velocity dependence is known to be difficult to measure, as it is proportional to the incident optical power multiplied by the ratio of the material velocity to the speed of light. Here we show that this typically tiny effect is greatly amplified in multilayer systems composed of resonantly absorbing atoms exhibiting ultranarrow photonic band gaps. The amplification effect for optically trapped 87Rb is shown to be as much as 3 orders of magnitude greater than for conventional photonic-band-gap materials. For a specific pulsed regime, damping remains observable without destroying the system and significant for material velocities of a few ms(-1).

  19. Damping assembly for a torque converter clutch

    SciTech Connect

    Dull, D.C.

    1989-12-26

    This patent describes a turbine damped torque converter and clutch. It comprises: a pressure plate; a torque converter turbine; a torque converter impeller; means including a control chamber for the pressure plate means for controlling the apply and release of the clutch for engaging the clutch with the impeller; a torque converter output shaft; a planetary gear arrangement including an input gear drivingly connected with the pressure plate, a reaction gear drivingly connected with the turbine, an output member drivingly connected with the output shaft and pinion gear means meshing with the input gear and the reaction gear for drivingly interconnecting the turbine and the pressure plate at a drive ratio of the turbine to the pressure plate of less than 1:1; and one-way drive means disposed between the turbine and the output shaft for preventing the turbine from overrunning the output shaft.

  20. Magnetoacoustic heating by ion Landau damping

    NASA Technical Reports Server (NTRS)

    Turner, L.

    1980-01-01

    The Vlasov-fluid model of Freidberg (1972) is used to study the resonance heating of a sharp-boundary screw pinch. The analysis provides the first treatment of the magnetoacoustic heating of a cylindrical plasma by means of ion Landau damping, which was identified as a viable dissipative mechanism for the conversion of magnetoacoustic wave energy into ion thermal energy. In addition, local and global energy conservation are considered, and formulae and numerical results for the thermal energy doubling time and the associated induced rf electric fields are presented. It is shown that collisionless absorption can provide a heating mechanism when an equilibrium plasma column is pumped by oscillations of the confining magnetic field at a frequency near the oblique magnetoacoustic frequency.

  1. Transient growth of damped baroclinic waves

    NASA Technical Reports Server (NTRS)

    Farrell, B.

    1985-01-01

    A solution of the linear initial value problem for the model of Eady with the inclusion of Ekman damping is presented. This model exhibits large transient growth of perturbations for synoptic cyclone spatial scales and a realistic value of the vertical turbulent viscosity coefficient despite the fact that all normal modes are exponentially decaying. Similar results are found for the model of Charney, implying that exponential instability cannot, in general, serve to explain the occurrence of cyclone scale disturbances in midlatiudes. Rather these are seen to arise additionally and perhaps predominantly from the release of mean flow potential energy by favorably configured initial perturbations. The Petterssen criterion for midlatitude cyclogenesis results naturally from this development as does its extension to the formation of subtropical monsoon depressions. Implications for the maintenance of midlatitude temperature gradients are discussed.

  2. Magnetoacoustic heating by ion Landau damping

    NASA Astrophysics Data System (ADS)

    Turner, L.

    1980-07-01

    The Vlasov-fluid model of Freidberg (1972) is used to study the resonance heating of a sharp-boundary screw pinch. The analysis provides the first treatment of the magnetoacoustic heating of a cylindrical plasma by means of ion Landau damping, which was identified as a viable dissipative mechanism for the conversion of magnetoacoustic wave energy into ion thermal energy. In addition, local and global energy conservation are considered, and formulae and numerical results for the thermal energy doubling time and the associated induced rf electric fields are presented. It is shown that collisionless absorption can provide a heating mechanism when an equilibrium plasma column is pumped by oscillations of the confining magnetic field at a frequency near the oblique magnetoacoustic frequency.

  3. Magnetic Damping of Solid Solution Semiconductor Alloys

    NASA Technical Reports Server (NTRS)

    Szofran, Frank R.; Benz, K. W.; Croell, Arne; Dold, Peter; Cobb, Sharon D.; Volz, Martin P.; Motakef, Shariar

    1999-01-01

    The objective of this study is to: (1) experimentally test the validity of the modeling predictions applicable to the magnetic damping of convective flows in electrically conductive melts as this applies to the bulk growth of solid solution semiconducting materials; and (2) assess the effectiveness of steady magnetic fields in reducing the fluid flows occurring in these materials during processing. To achieve the objectives of this investigation, we are carrying out a comprehensive program in the Bridgman and floating-zone configurations using the solid solution alloy system Ge-Si. This alloy system has been studied extensively in environments that have not simultaneously included both low gravity and an applied magnetic field. Also, all compositions have a high electrical conductivity, and the materials parameters permit reasonable growth rates. An important supporting investigation is determining the role, if any, that thermoelectromagnetic convection (TEMC) plays during growth of these materials in a magnetic field. TEMC has significant implications for the deployment of a Magnetic Damping Furnace in space. This effect will be especially important in solid solutions where the growth interface is, in general, neither isothermal nor isoconcentrational. It could be important in single melting point materials, also, if faceting takes place producing a non-isothermal interface. In conclusion, magnetic fields up to 5 Tesla are sufficient to eliminate time-dependent convection in silicon floating zones and possibly Bridgman growth of Ge-Si alloys. In both cases, steady convection appears to be more significant for mass transport than diffusion, even at 5 Tesla in the geometries used here. These results are corroborated in both growth configurations by calculations.

  4. Magnetic Damping of Solid Solution Semiconductor Alloys

    NASA Technical Reports Server (NTRS)

    Szofran, Frank R.; Benz, K. W.; Corell, Arne; Dold, Peter; Cobb, Sharon D.; Volz, Martin P.; Motakef, Shariar

    1998-01-01

    The objective of this study is to conduct the Earth-based research sufficient to successfully propose a flight experiment (1) to experimentally test the validity of the modeling predictions applicable to the magnetic damping of convective flows in conductive melts as this applies to the bulk growth of solid solution semiconducting materials in the reduced gravitational levels available in low Earth orbit and (2) to assess the effectiveness of steady magnetic fields in reducing the fluid flows occurring in these materials during space processing. To achieve the objectives of this investigation, we are carrying out a comprehensive program in the Bridgman and floating-zone configurations using the solid solution alloy system Ge-Si. This alloy system was chosen because it has been studied extensively in environments that have not simultaneously included both low gravity and an applied magnetic field. Also, all compositions have a high electrical conductivity, and the materials parameters permit high growth rates compared to many other commonly studied alloy semiconductors. An important supporting investigation is determining the role, if any, that thermoelectromagnetic convection (TEMC) plays during growth of these materials in a magnetic field. Some compositional anomalies observed by us in magnetic grown crystals can only be explained by TEMC; this has significant implications for the deployment of a Magnetic Damping Furnace in space. This effect will be especially important in solid solutions where the growth interface is, in general, neither isothermal nor isoconcentrational. It could be important in single melting point materials, also, if faceting takes place producing a non-isothermal interface.

  5. Experimental Observations on Material Damping at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Peng, Chia-Yen; Levine, Marie; Shido, Lillian; Leland, Robert

    2004-01-01

    This paper describes a unique experimental facility designed to measure damping of materials at cryogenic temperatures for the Terrestrial Planet Finder (TPF) mission at the Jet Propulsion Laboratory. The test facility removes other sources of damping in the measurement by avoiding frictional interfaces, decoupling the test specimen from the support system, and by using a non-contacting measurement device. Damping data reported herein are obtained for materials (Aluminum, Aluminum/Terbium/Dysprosium, Titanium, Composites) vibrating in free-free bending modes with low strain levels (< 10(exp -6) ppm). The fundamental frequencies of material samples are ranged from 14 to 202 Hz. To provide the most beneficial data relevant to TPF-like precision optical space missions, the damping data are collected from room temperatures (around 293 K) to cryogenic temperatures (below 40 K) at unevenly-spaced intervals. More data points are collected over any region of interest. The test data shows a significant decrease in viscous damping at cryogenic temperatures. The cryogenic damping can be as low as 10(exp -4) %, but the amount of the damping decrease is a function of frequency and material. However, Titanium 15-3-3-3 shows a remarkable increase in damping at cryogenic temperatures. It demonstrates over one order of magnitude increase in damping in comparison to Aluminum 6061-T6. Given its other properties (e.g., good stiffness and low conductivity) this may prove itself to be a good candidate for the application on TPF. At room temperatures, the test data are correlated well with the damping predicted by the Zener theory. However, large discrepancies at cryogenic temperatures between the Zener theory and the test data are observed.

  6. Experimental Observations on Material Damping at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Peng, Chia-Yen; Levine, Marie; Shido, Lillian; Leland, Robert

    2004-01-01

    This paper describes a unique experimental facility designed to measure damping of materials at cryogenic temperatures for the Terrestrial Planet Finder (TPF) mission at the Jet Propulsion Laboratory. The test facility removes other sources of damping in the measurement by avoiding frictional interfaces, decoupling the test specimen from the support system, and by using a non-contacting measurement device. Damping data reported herein are obtained for materials (Aluminum, Aluminum/Terbium/Dysprosium, Titanium, Composites) vibrating in free-free bending modes with low strain levels (< 10(exp -6) ppm). The fundamental frequencies of material samples are ranged from 14 to 202 Hz. To provide the most beneficial data relevant to TPF-like precision optical space missions, the damping data are collected from room temperatures (around 293 K) to cryogenic temperatures (below 40 K) at unevenly-spaced intervals. More data points are collected over any region of interest. The test data shows a significant decrease in viscous damping at cryogenic temperatures. The cryogenic damping can be as low as 10(exp -4) %, but the amount of the damping decrease is a function of frequency and material. However, Titanium 15-3-3-3 shows a remarkable increase in damping at cryogenic temperatures. It demonstrates over one order of magnitude increase in damping in comparison to Aluminum 6061-T6. Given its other properties (e.g., good stiffness and low conductivity) this may prove itself to be a good candidate for the application on TPF. At room temperatures, the test data are correlated well with the damping predicted by the Zener theory. However, large discrepancies at cryogenic temperatures between the Zener theory and the test data are observed.

  7. Diocotron Mode Damping from a Flux through the Critical Layer

    NASA Astrophysics Data System (ADS)

    Driscoll, C. Fred

    2014-10-01

    Experiments and theory characterize a novel type of spatial Landau damping of diocotron modes which is algebraic rather than exponential in time; this damping is caused by a flux of particles through the wave/rotation critical layer. These kz = 0 diocotron (drift) modes with azimuthal mode numbers mθ = 1 , 2 . . . are dominant features in the dynamics of non-neutral plasmas in cylindrical and toroidal traps; and they are directly analogous to Kelvin waves on 2D fluid vortices. Spatial Landau damping is the resonant interaction between a mode at frequency fm and the plasma rotation fE (r) , at the critical radius Rc where fm =mθfE (Rc) . This is mathematically analogous to velocity-space Landau damping with fk = kv / 2 π . Experimentally, diocotron modes on pure electron plasmas exhibit exponential Landau damping when the initial plasma density is non-zero at Rc. Here, we demonstrate that a steady outward flux of particles through Rc causes diocotron modes to damp algebraically to zero amplitude, as D (t) =D0 -γm t . The outward flux is controlled and measured experimentally, and the damping rates γm are proportional to the flux. In general, any weak non-ideal process which causes outward flux may cause this damping. Analytics and simulations have developed a simple model of this damping, treating the transfer of canonical angular momentum from the mode to particles transiting the nonlinear trapping region at Rc. The model qualitatively agrees with experiments for mθ = 1 , but nominally predicts a discrepant algebraic exponent for mθ = 2 , perhaps due to the amplitude dependence of the trapping structure. Overall, this novel flux-driven damping is determined by the present magnitudes of the wave and outward flux, in contrast to the Landau analysis of phase mixing of the initial density. Supported by NSF/DOE Partnership Grants PHY-0903877 and DE-SC0002451.

  8. Atomistic Mechanisms for Viscoelastic Damping in Inorganic Solids

    NASA Astrophysics Data System (ADS)

    Ranganathan, Raghavan

    Viscoelasticity, a ubiquitous material property, can be tuned to engineer a wide range of fascinating applications such as mechanical dampers, artificial tissues, functional foams and optoelectronics, among others. Traditionally, soft matter such as polymers and polymer composites have been used extensively for viscoelastic damping applications, owing to the inherent viscous nature of interactions between polymer chains. Although this leads to good damping characteristics, the stiffness in these materials is low, which in turn leads to limitations. In this context, hard inorganic materials and composites are promising candidates for enhanced damping, owing to their large stiffness and, in some cases large loss modulus. Viscoelasticity in these materials has been relatively unexplored and atomistic mechanisms responsible for damping are not apparent. Therefore, the overarching goal of this work is to understand mechanisms for viscoelastic damping in various classes of inorganic composites and alloys at an atomistic level from molecular dynamics simulations. We show that oscillatory shear deformation serves as a powerful probe to explain mechanisms for exceptional damping in hitherto unexplored systems. The first class of inorganic materials consists of crystalline phases of a stiff inclusion in a soft matrix. The two crystals within the composite, namely the soft and a stiff phase, individually show a highly elastic behavior and a very small loss modulus. On the other hand, a composite with the two phases is seen to exhibit damping that is about 20 times larger than predicted theoretical bounds. The primary reason for the damping is due to large anharmonicity in phonon-phonon coupling, resulting from the composite microstructure. A concomitant effect is the distribution of shear strain, which is observed to be highly inhomogeneous and mostly concentrated in the soft phase. Interestingly, the shear frequency at which the damping is greatest is observed to scale with

  9. Flux-driven algebraic damping of diocotron modes

    SciTech Connect

    Chim, Chi Yung; O’Neil, Thomas M.

    2015-06-29

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 1 and m = 2 diocotron modes. Transport due to small field asymmetries produces a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius R{sub m}, where there is a matching of ω{sub m} = mω{sub E} (R{sub m}) for the mode frequency ω{sub m} and E × B-drift rotation frequency ω{sub E}. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from, spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This new mechanism of damping is due to transfer of canonical angular momentum from the mode to halo particles, as they are swept around the “cat’s eye” orbits of the resonant wave-particle interaction. This paper provides a simple derivation of the time dependence of the mode amplitudes.

  10. Nonlinear damping calculation in cylindrical gear dynamic modeling

    NASA Astrophysics Data System (ADS)

    Guilbault, Raynald; Lalonde, Sébastien; Thomas, Marc

    2012-04-01

    The nonlinear dynamic problem posed by cylindrical gear systems has been extensively covered in the literature. Nonetheless, a significant proportion of the mechanisms involved in damping generation remains to be investigated and described. The main objective of this study is to contribute to this task. Overall, damping is assumed to consist of three sources: surrounding element contribution, hysteresis of the teeth, and oil squeeze damping. The first two contributions are considered to be commensurate with the supported load; for its part however, squeeze damping is formulated using expressions developed from the Reynolds equation. A lubricated impact analysis between the teeth is introduced in this study for the minimum film thickness calculation during contact losses. The dynamic transmission error (DTE) obtained from the final model showed close agreement with experimental measurements available in the literature. The nonlinear damping ratio calculated at different mesh frequencies and torque amplitudes presented average values between 5.3 percent and 8 percent, which is comparable to the constant 8 percent ratio used in published numerical simulations of an equivalent gear pair. A close analysis of the oil squeeze damping evidenced the inverse relationship between this damping effect and the applied load.

  11. Cellular Magnesium Matrix Foam Composites for Mechanical Damping Applications

    NASA Astrophysics Data System (ADS)

    Shunmugasamy, Vasanth Chakravarthy; Mansoor, Bilal; Gupta, Nikhil

    2016-01-01

    The damping characteristics of metal alloys and metal matrix composites are relevant to the automotive, aerospace, and marine structures. Use of lightweight materials can help in increasing payload capacity and in decreasing fuel consumption. Lightweight composite materials possessing high damping capabilities that can be designed as structural members can greatly benefit in addressing these needs. In this context, the damping properties of lightweight metals such as aluminum and magnesium and their respective composites have been studied in the existing literature. This review focuses on analyzing the damping properties of aluminum and magnesium alloys and their cellular composites. The damping properties of various lightweight alloys and composites are compared on the basis of their density to understand the potential for weight saving in structural applications. Magnesium alloys are observed to possess better damping properties in comparison to aluminum. However, aluminum matrix syntactic foams reinforced with silicon carbide hollow particles possess a damping capacity and density comparable to magnesium alloy. By using the data presented in the study, composites with specific compositions and properties can be selected for a given application. In addition, the comparison of the results helps in identifying the areas where attention needs to be focused to address the future needs.

  12. Perceptual studies of violin body damping and vibrato.

    PubMed

    Fritz, Claudia; Woodhouse, Jim; Cheng, Felicia P-H; Cross, Ian; Blackwell, Alan F; Moore, Brian C J

    2010-01-01

    This work explored how the perception of violin notes is influenced by the magnitude of the applied vibrato and by the level of damping of the violin resonance modes. Damping influences the "peakiness" of the frequency response, and vibrato interacts with this peakiness by producing fluctuations in spectral content as well as in frequency and amplitude. Initially, it was shown that thresholds for detecting a change in vibrato amplitude were independent of body damping, and thresholds for detecting a change in body damping were independent of vibrato amplitude. A study of perceptual similarity using triadic comparison showed that vibrato amplitude and damping were largely perceived as independent dimensions. A series of listening tests was conducted employing synthesized, recorded, or live performance to probe perceptual responses in terms of "liveliness" and preference. The results do not support the conclusion that liveliness results from the combination of the use of vibrato and a "peaky" violin response. Judgments based on listening to single notes showed inconsistent patterns for liveliness, while preferences were highest for damping that was slightly less than for a reference (real) violin. In contrast, judgments by players based on many notes showed preference for damping close to the reference value.

  13. SPATIAL DAMPING OF PROPAGATING KINK WAVES IN PROMINENCE THREADS

    SciTech Connect

    Soler, R.; Oliver, R.; Ballester, J. L.

    2011-01-10

    Transverse oscillations and propagating waves are frequently observed in threads of solar prominences/filaments and have been interpreted as kink magnetohydrodynamic (MHD) modes. We investigate the spatial damping of propagating kink MHD waves in transversely nonuniform and partially ionized prominence threads. Resonant absorption and ion-neutral collisions (Cowling's diffusion) are the damping mechanisms taken into account. The dispersion relation of resonant kink waves in a partially ionized magnetic flux tube is numerically solved by considering prominence conditions. Analytical expressions of the wavelength and damping length as functions of the kink mode frequency are obtained in the thin tube and thin boundary approximations. For typically reported periods of thread oscillations, resonant absorption is an efficient mechanism for the kink mode spatial damping, while ion-neutral collisions have a minor role. Cowling's diffusion dominates both the propagation and damping for periods much shorter than those observed. Resonant absorption may explain the observed spatial damping of kink waves in prominence threads. The transverse inhomogeneity length scale of the threads can be estimated by comparing the observed wavelengths and damping lengths with the theoretically predicted values. However, the ignorance of the form of the density profile in the transversely nonuniform layer introduces inaccuracies in the determination of the inhomogeneity length scale.

  14. Experiences with active damping and impedance-matching compensators

    NASA Astrophysics Data System (ADS)

    Betros, Robert S.; Alvarez, Oscar S.; Bronowicki, Allen J.

    1993-09-01

    TRW has been implementing active damping compensators on smart structures for the past five years. Since that time there have been numerous publications on the use of impedance matching techniques for structural damping augmentation. The idea of impedance matching compensators came about by considering the flow of power in a structure undergoing vibration. The goal of these compensators is to electronically dissipate as much of this flowing power as possible. This paper shows the performance of impedance matching compensators used in smart structures to be comparable to that of active damping compensators. Theoretical comparisons between active damping and impedance matching methods are made using PZT actuators and sensors. The effects of these collocated and non-collocated PZT sensors and actuators on the types of signals they sense and actuate are investigated. A method for automatically synthesizing impedance matching compensators is presented. Problems with implementing broad band active damping and impedance matching compensators on standard Digital Signal Processing (DSP) chips are discussed. Simulations and measurements that compare the performance of active damping and impedance matching techniques for a lightly damped cantilevered beam are shown.

  15. Structural dynamics and vibrations of damped, aircraft-type structures

    NASA Technical Reports Server (NTRS)

    Young, Maurice I.

    1992-01-01

    Engineering preliminary design methods for approximating and predicting the effects of viscous or equivalent viscous-type damping treatments on the free and forced vibration of lightly damped aircraft-type structures are developed. Similar developments are presented for dynamic hysteresis viscoelastic-type damping treatments. It is shown by both engineering analysis and numerical illustrations that the intermodal coupling of the undamped modes arising from the introduction of damping may be neglected in applying these preliminary design methods, except when dissimilar modes of these lightly damped, complex aircraft-type structures have identical or nearly identical natural frequencies. In such cases, it is shown that a relatively simple, additional interaction calculation between pairs of modes exhibiting this 'modal response' phenomenon suffices in the prediction of interacting modal damping fractions. The accuracy of the methods is shown to be very good to excellent, depending on the normal natural frequency separation of the system modes, thereby permitting a relatively simple preliminary design approach. This approach is shown to be a natural precursor to elaborate finite element, digital computer design computations in evaluating the type, quantity, and location of damping treatment.

  16. Damping and energy dissipation in soft tissue vibrations during running.

    PubMed

    Khassetarash, Arash; Hassannejad, Reza; Enders, Hendrik; Ettefagh, Mir Mohammad

    2015-01-21

    It has been well accepted that the vibrations of soft tissue cannot be simulated by a single sinusoidal function. In fact, these vibrations are a combination of several vibration modes. In this study, these modes are extracted applying a recently developed method namely, partly ensemble empirical mode decomposition (PEEMD). Then, a methodology for estimating the damping properties and energy dissipation caused by damping for each mode is used. Applying this methodology on simulated signals demonstrates high accuracy. This methodology is applied to the acceleration signals of the gastrocnemius muscle during sprinting and the differences between the damping properties of different vibration modes were identified. The results were 1) the damping property of high-frequency mode was higher than that for low-frequency modes. 2) All identified modes were in under damped condition, therefore, the vibrations had an oscillatory nature. 3) The damping ratios of lower modes are about 100% increased compared to higher modes. 4) The energy dissipation occurred in lower modes were much more than that for higher mode; According to the power spectrum of the ground reaction force (GRF), which is the input force into the body, the recent finding supports the muscle tuning paradigm. It is suggested that the damping properties and energy dissipation can be used to distinguish between different running conditions (surface, fatigue, etc.).

  17. Flux-driven algebraic damping of diocotron modes

    NASA Astrophysics Data System (ADS)

    Chim, Chi Yung; O'Neil, Thomas M.

    2015-06-01

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 1 and m = 2 diocotron modes. Transport due to small field asymmetries produces a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius Rm, where there is a matching of ωm = mωE (Rm) for the mode frequency ωm and E × B-drift rotation frequency ωE. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from, spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This new mechanism of damping is due to transfer of canonical angular momentum from the mode to halo particles, as they are swept around the "cat's eye" orbits of the resonant wave-particle interaction. This paper provides a simple derivation of the time dependence of the mode amplitudes.

  18. Flux-driven algebraic damping of m=2 diocotron mode

    NASA Astrophysics Data System (ADS)

    Chim, C. Y.; O'Neil, T. M.

    2016-10-01

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 2 diocotron modes. Due to small field asymmetries a low density halo of electrons is transported radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius rres, where f = mfE × B (rres) . The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from the exponential spatial Landau damping in a linear wave-particle resonance. This poster uses analytic theory and simulations to explain the new flux-driven algebraic damping of the mode. As electrons are swept around the nonlinear ``cat's eye'' orbits of the resonant wave-particle interaction, they form a quadrupole (m = 2) density distribution, which sets up an electric field that acts back on the plasma core. The field causes an E × B drift motion that symmetrizes the core, i.e. damps the m = 2 mode. Supported by NSF Grant PHY-1414570, and DOE Grants DE-SC0002451.

  19. Key Role of DAMP in Inflammation, Cancer, and Tissue Repair.

    PubMed

    Pandolfi, Franco; Altamura, Simona; Frosali, Simona; Conti, Pio

    2016-05-01

    This review aimed to take stock of the current status of research on damage-associated molecular pattern (DAMP) protein. We discuss the Janus-faced role of DAMP molecules in inflammation, cancer, and tissue repair. The high-mobility group box (HMGB)-1 and adenosine triphosphate proteins are well-known DAMP molecules and have been primarily associated with inflammation. However, as we shall see, recent data have linked these molecules to tissue repair. HMGB1 is associated with cancer-related inflammation. It activates nuclear factor kB, which is involved in cancer regulation via its receptor for advanced glycation end-products (RAGE), Toll-like receptors 2 and 4. Proinflammatory activity and tissue repair may lead to pharmacologic intervention, by blocking DAMP RAGE and Toll like receptor 2 and 4 role in inflammation and by increasing their concentration in tissue repair, respectively. We conducted a MEDLINE search for articles pertaining to the various issues related to DAMP, and we discuss the most relevant articles especially (ie, not only those published in journals with a higher impact factor). A cluster of remarkable articles on DAMP have appeared in the literature in recent years. Regarding inflammation, several strategies have been proposed to target HMGB1, from antibodies to recombinant box A, which interacts with RAGE, competing with the full molecule. In tissue repair, it was reported that the overexpression of HMGB1 or the administration of exogenous HMGB1 significantly increased the number of vessels and promoted recovery in skin-wound, ischemic injury. Due to the bivalent nature of DAMP, it is often difficult to explain the relative role of DAMP in inflammation versus its role in tissue repair. However, this point is crucial as DAMP-related treatments move into clinical practice. Copyright © 2016 Elsevier HS Journals, Inc. All rights reserved.

  20. Damping phenomena in a wire rope vibration isolation system

    NASA Technical Reports Server (NTRS)

    Tinker, M. L.; Cutchins, M. A.

    1992-01-01

    A study is presented of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators, with emphasis placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase plane trajectories, and frequency response curves are obtained. A semiempirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb friction damping is developed, and the results are compared to experimental data. Several observations and conclusions are made about the dynamic phenomena in a typical wire rope vibration isolation system based on the experimental and semiempirical results.

  1. Damping phenomena in a wire rope vibration isolation system

    NASA Technical Reports Server (NTRS)

    Tinker, Michael L.; Cutchins, Malcolm A.

    1990-01-01

    A study of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators is presented. Emphasis is placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase trajectories, and frequency response curves were obtained. A semi-empirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb friction damping is developed and results are compared to experimental data. Conclusions about dynamic phenomena in the wire rope system are made based on the experimental and semi-empirical results.

  2. Damping and support in high-temperature superconducting levitation systems

    DOEpatents

    Hull, John R.; McIver, Carl R.; Mittleider, John A.

    2009-12-15

    Methods and apparatuses to provide improved auxiliary damping for superconducting bearings in superconducting levitation systems are disclosed. In a superconducting bearing, a cryostat housing the superconductors is connected to a ground state with a combination of a damping strip of material, a set of linkage arms to provide vertical support, and spring washers to provide stiffness. Alternately, the superconducting bearing may be supported by a cryostat connected to a ground state by posts constructed from a mesh of fibers, with the damping and stiffness controlled by the fiber composition, size, and mesh geometry.

  3. An Improved Model for Air Damping of Perforated Structures

    NASA Astrophysics Data System (ADS)

    Lu, Cunhao; Li, Pu

    2017-07-01

    the prediction of air damping of micromachined mechanical resonant structures is significant in the design of high quality factor devices. In rarefied air, based on Bao’s molecule model, Li gives an analytical model for air damping of perforated structures. By studying the action of molecules going through holes and reflected by the fixed plate, this paper gives a probability of molecules through holes going into the gap between the moving plate and the fixed one. Comparison with Li’s model, the new model can play a better performance of air damping for perforated structures, at a wide range of size of holes.

  4. Damping MEMS Devices in Harsh Environments Using Active Thin Films

    DTIC Science & Technology

    2008-06-17

    properties of the layers was developed. Damping properties in Nitinol thin film due only to residual stresses was measured to be as high as tan delta...0.17 for large strain (0.9%). At lower strain levels a Nitinol /Silicon laminate was tested in a cantilever load frame. The damping value of the...film was measured to be 0.28 (at 0.27% strain). A Nitinol /Terfenol-D/Nickel laminate was fabricated and tested in a cantilever loading. The damping

  5. Effects of damping on mode shapes, volume 2

    NASA Technical Reports Server (NTRS)

    Gates, R. M.; Merchant, D. H.; Arnquist, J. L.

    1977-01-01

    Displacement, velocity, and acceleration admittances were calculated for a realistic NASTRAN structural model of space shuttle for three conditions: liftoff, maximum dynamic pressure and end of solid rocket booster burn. The realistic model of the orbiter, external tank, and solid rocket motors included the representation of structural joint transmissibilities by finite stiffness and damping elements. Data values for the finite damping elements were assigned to duplicate overall low-frequency modal damping values taken from tests of similar vehicles. For comparison with the calculated admittances, position and rate gains were computed for a conventional shuttle model for the liftoff condition. Dynamic characteristics and admittances for the space shuttle model are presented.

  6. Design parameters for the damped detuned accelerating structure

    SciTech Connect

    Ko, K.; Bane, K.; Gluckstern, R.; Hoag, H.; Kroll, N.; Lin, X.T.; Miller, R.; Ruth, R.; Thompson, K.; Wang, J. ||

    1995-06-01

    The advanced accelerating cavities for the NLCTA (and anticipated for NLC) will incorporate damping as well as detuning. The damping is provided by a set of four waveguides (which also serve as pumping manifolds) that run parallel to the structure, with strong iris coupling to each cavity cell and terminated at each end by absorbers. The previously reported equivalent circuit analysis has been refined and the dependence upon design parameters explored. The authors find that adequate damping can be provided by a single waveguide mode, leading to designs which are more compact than those initially considered. The design parameters and their rationale will be presented.

  7. Investigation of empirical damping laws for the space shuttle

    NASA Technical Reports Server (NTRS)

    Bernstein, E. L.

    1973-01-01

    An analysis of dynamic test data from vibration testing of a number of aerospace vehicles was made to develop an empirical structural damping law. A systematic attempt was made to fit dissipated energy/cycle to combinations of all dynamic variables. The best-fit laws for bending, torsion, and longitudinal motion are given, with error bounds. A discussion and estimate are made of error sources. Programs are developed for predicting equivalent linear structural damping coefficients and finding the response of nonlinearly damped structures.

  8. Nonlinear Landau damping of transverse electromagnetic waves in dusty plasmas

    SciTech Connect

    Tsintsadze, N. L.; Chaudhary, Rozina; Shah, H. A.; Murtaza, G.

    2009-04-15

    High-frequency transverse electromagnetic waves in a collisionless isotropic dusty plasma damp via nonlinear Landau damping. Taking into account the latter we have obtained a generalized set of Zakharov equations with local and nonlocal terms. Then from this coupled set of Zakharov equations a kinetic nonlinear Schroedinger equation with local and nonlocal nonlinearities is derived for special cases. It is shown that the modulation of the amplitude of the electromagnetic waves leads to the modulation instability through the nonlinear Landau damping term. The maximum growth rate is obtained for the special case when the group velocity of electromagnetic waves is close to the dust acoustic velocity.

  9. Damping induced by ferrofluid seals in ironless loudspeaker

    NASA Astrophysics Data System (ADS)

    Pinho, M.; Génevaux, J. M.; Dauchez, N.; Brouard, B.; Collas, P.; Mézière, H.

    2014-04-01

    Damping induced by ferrofluid seals in ironless loudspeakers is investigated in this paper. The magnetic field is steady but not spatially constant. A model to determine the viscous damping coefficient induced by the ferrofluid seal is derived. It is a function of geometrical parameters and local viscosity of the ferrofluid in which dependence from magnetic field, shear rate and frequency is accounted for. Comparison with experimental results shows a good agreement for the thinner seals. An overestimation of the damping is observed for higher volumes. This discrepancy comes from geometric irregularities of the magnet assembly made out of several tiles.

  10. Backup nutation damping strategy for the Galileo spacecraft

    NASA Technical Reports Server (NTRS)

    Eke, Fidelis O.; Eke, Estelle M.

    1989-01-01

    A discussion is presented of the design and testing of remedial measures that can be taken to achieve reasonable nutation damping of the Galileo spacecraft in the event of failure of its boom damper in flight. One scheme exploits the effects of payload motion on the nutational stability of a spinning spacecraft. However, the spacecraft-motion-compensation algorithm can only be used if the scan platform bore sight is pointed in a direction chosen to produce rapid damping of spacecraft nutation. A second method suggested for nutation damping is a thruster-based open-loop control algorithm, utilizing a pair of thrusters as actuators.

  11. Dissipationless Damping of Compressive MHD Modes in Twisted Flux Tubes

    NASA Astrophysics Data System (ADS)

    Giagkiozis, I.; Fedun, V.; Verth, G.; Goossens, M. L.; Van Doorsselaere, T.

    2015-12-01

    Axisymmetric modes in straight magentic flux tubes exhibit a cutoff in the long wavelength limit and no damping is predicted. However, as soon as weak magnetic twist is introduced inside as well as outside the magnetic flux tube the cutoff recedes. Furthermore, when density variations are also incomporated within the modelresonant absorption appears. In this work we explore analytically the expected damping times for waves within the Alfven continuum for different solar atmospheric conditions. Based on the results in this work we offer insight on recent observations of sausage wave damping in the chromosphere.

  12. Liquid-filled type vibration damping structure

    SciTech Connect

    Tabata, T.

    1987-06-16

    A liquid-filled type vibration damping structure is described comprising: a liquid-filled vibration isolator having (a) first and second frames respectively mounted on a vibration source and on the side of a vehicle body; (b) resilient member connected between the first and second frames; (c) a diaphragm secured to the first frame; (d) a baffle member secured onto the first frame and dividing an internal space surrounded by the resilient member, the diaphragm, and the second frame into first and second liquid chambers, the baffle member further having a hole and a first aperture for communicating the first and second liquid chambers with each other; (e) a holder cooperating with the baffle member to form therebetween an orifice portion communicated with the hole of the baffle member and having at least one aperture aligned with the first aperture of the baffle member; (f) a movable plate held by at least the holder between the apertures of the holder and the baffle member and moved with respect to the baffle member by the liquid flow through the apertures of the holder and the baffle member; and (g) at least one mass body attached into the resilient member to reduce the resilient coefficient. The structure further comprising: a bracket member for mounting the vibration isolator onto the vibration source at a predetermined angle of inclination with respect to the direction of vibration from the source; and the angle is sufficient to suppress the generation of a liquid column resonance peak.

  13. Warburg effect-damping of electromagnetic oscillations.

    PubMed

    Pokorný, Jiří; Pokorný, Jan; Borodavka, Fedir

    2017-06-02

    Mitochondrial dysfunction is a central defect in cells creating the Warburg and reverse Warburg effect cancers. However, the link between mitochondrial dysfunction and cancer has not yet been clearly explained. Decrease of mitochondrial oxidative energy production to about 50 % in comparison with healthy cells may be caused by inhibition of pyruvate transfer into mitochondrial matrix and/or disturbed H(+) ion transfer across inner mitochondrial membrane into cytosol. Lowering of the inner membrane potential and shifting of the working point of mitochondria to high values of pH above an intermediate point causes reorganization of the ordered water layer at the mitochondrial membrane. The reorganized ordered water layers at high pH values release electrons which are transferred to the cytosol rim of the layer. The electrons damp electromagnetic activity of Warburg effect cancer cells or fibroblasts associated with reverse Warburg effect cancer cells leading to lowered electromagnetic activity, disturbed coherence, increased frequency of oscillations and decreased level of biological functions. In reverse Warburg effect cancers, associated fibroblasts supply energy-rich metabolites to the cancer cell resulting in increased power of electromagnetic field, fluctuations due to shift of oscillations to an unstable nonlinear region, decreased frequency and loss of coherence.

  14. Loss of Landau Damping for Bunch Oscillations

    SciTech Connect

    Burov, A.; /Fermilab

    2011-04-11

    Conditions for the existence, uniqueness and stability of self-consistent bunch steady states are considered. For the existence and uniqueness problems, simple algebraic criteria are derived for both the action and Hamiltonian domain distributions. For the stability problem, van Kampen theory is used. The onset of a discrete van Kampen mode means the emergence of a coherent mode without any Landau damping; thus, even a tiny couple-bunch or multi-turn wake is sufficient to drive the instability. The method presented here assumes an arbitrary impedance, RF shape, and beam distribution function. Available areas on the intensity-emittance plane are shown for resistive wall wake and single harmonic, bunch shortening and bunch lengthening RF configurations. Thresholds calculated for the Tevatron parameters and impedance model are in agreement with the observations. These thresholds are found to be extremely sensitive to the small-argument behaviour of the bunch distribution function. Accordingly, a method to increase the LLD threshold is suggested. This article summarizes and extends recent author's publications.

  15. Damping of forward neutrons in pp collisions

    NASA Astrophysics Data System (ADS)

    Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan; Soffer, J.

    2008-07-01

    We calculate absorptive corrections to single pion exchange in the production of leading neutrons in pp collisions. Contrary to the usual procedure of convolving the survival probability with the cross section, we apply corrections to the spin amplitudes. The nonflip amplitude turns out to be much more suppressed by absorption than the spin-flip one. We identify the projectile proton Fock state responsible for the absorptive corrections as a color octet-octet 5-quarks configuration. Calculations within two very different models, color-dipole light-cone description, and in hadronic representation, lead to rather similar absorptive corrections. We found a much stronger damping of leading neutrons than in some of previous estimates. Correspondingly, the cross section is considerably smaller than was measured at ISR. However, comparison with recent measurements by the ZEUS collaboration of neutron production in deep-inelastic scattering provides a strong motivation for challenging the normalization of the ISR data. This conjecture is also supported by preliminary data from the NA49 experiment for neutron production in pp collisions at SPS.

  16. Influence of quasiparticle damping on magnetic stability

    NASA Astrophysics Data System (ADS)

    Herrmann, T.; Nolting, W.

    1996-04-01

    We propose a modified alloy analogy for the single-band Hubbard model, by which we investigate the possibility of spontaneous ferromagnetism in narrow energy bands. It is shown that a proper definition of the fictitious alloy enables self-consistent magnetic solutions to be found. The existence of spontaneous magnetism is mainly influenced by the lattice structure, the effective Coulomb coupling, and the band occupation. In accordance with the simple Stoner criterion, ferromagnetism appears in strongly correlated electron systems for band occupations, which locate the chemical potential μ in regions of high quasiparticle density of states. Rather realistic Curie temperatures are found. The macroscopic magnetic properties explain themselves via temperature-dependent quasiparticle densities of states, quasiparticle band structures, and respective spectral densities. It is shown how quasiparticle damping may depress quite substantially the stability of magnetic states by broadening corresponding spectral density peaks. Correlation effects lead to the expected splitting into two quasiparticle subbands (``Hubbard bands''), and under certain conditions to an additional exchange splitting of each of these quasiparticle subbands, as well as to a spin-dependent band narrowing, the combination of which gives rise to an unconventional ``inverse'' exchange shift at certain positions of the Brillouin zone.

  17. Nonlinear Landau damping in the ionosphere

    NASA Technical Reports Server (NTRS)

    Kiwamoto, Y.; Benson, R. F.

    1979-01-01

    A model which explains the nonresonant waves which produce the diffuse resonance observed near 3/2 f(H) by the Alouette and Isis topside sounders, where f(H) is the ambient electron cyclotron frequency, is presented. These waves are the result of plasma wave instabilities driven by anisotropic electron velocity distributions initiated by the high-power short-duration sounder pulse. Calculations of the nonlinear wave-particle coupling coefficients show that the diffuse resonance wave can be maintained by nonlinear Landau damping of the sounder-stimulated 2f(H) wave which is observed with a time duration longer than that of the diffuse resonance wave. The time duration of the diffuse resonance is determined by the transit time of the instability-generated and nonlinearly maintained diffuse resonance wave from the remote short-lived hot region back to the antenna. The model is consistent with the Alouette/Isis observations and it demonstrates the existence of nonlinear wave-particle interactions in the ionosphere.

  18. Thermoelastic Damping in Cone Microcantilever Resonator

    NASA Astrophysics Data System (ADS)

    Li, Pu; Zhou, Hongyue

    2017-07-01

    Microbeams with continuous or discontinuous variable cross-section have been applied in Microelectromechanical Systems (MEMS) resonators, such as tapered microbeam, torsion microbeam and stepped microbeam. Thermoelastic damping (TED), which is verified as a fundamental energy lost mechanism for microresonators, is calculated by the Zener’s model and Lifshits and Roukes’s (LR) model in general. However, for non-uniform microbeam resonators, these two classical models are not suitable in some cases. On the basis of Zener’s theory, a TED model for cone microcantilever with rectangular cross-section has been derived in this study. The comparison of results obtained by the present model and Finite Element Method (FEM) model proves that the proposed model is able to predict TED value for cone microcantilever. In addition, TED in cone microcantilever is nearly same as TED in wedge microcantilever. The results show that quality factors (Q-factors) of cone microcantilever and wedge microcantilever are larger than Q-factor of uniform microbeam at low frequencies. The Debye peak value of a uniform microcantilever is equal to 0.5Δ E , while those of cone microcantilever and wedge microcantilever are about 0.438ΔE and 0.428ΔE, respectively.

  19. Investigation of damping liquids for aircraft instruments

    NASA Technical Reports Server (NTRS)

    Keulegan, G H

    1929-01-01

    This report covers the results of an investigation carried on at the Bureau of Standards under a research authorization from, and with the financial assistance of, the National Advisory Committee for Aeronautics. The choice of a damping liquid for aircraft instruments is difficult owing to the range of temperature at which aircraft operate. Temperature changes affect the viscosity tremendously. The investigation was undertaken with the object of finding liquids of various viscosities otherwise suitable which had a minimum change in viscosity with temperature. The new data relate largely to solutions. The effect of temperature on the kinematic viscosity of the following liquids and solutions was determined in the temperature interval -18 degrees to +30 degrees C. (1) solutions of animal and vegetable oils in xylene. These were poppy-seed oil, two samples of neat's-foot oils, castor oil, and linseed oil. (2) solutions of mineral oil in xylene. These were Squibb's petrolatum of naphthene base and transformer oil. (3) glycerine solutions in ethyl alcohol and in mixture of 50-50 ethyl alcohol and water. (4) mixtures of normal butyl alcohol with methyl alcohol. (5) individual liquids, kerosene, mineral spirits, xylene, recoil oil. The apparatus consisted of four capillary-tube viscometers, which were immersed in a liquid bath in order to secure temperature control. The method of calibration and the related experimental data are presented.

  20. Association of residential dampness and mold with respiratory tract infections and bronchitis: a meta-analysis

    PubMed Central

    2010-01-01

    .33-1.65). Little effect of publication bias was evident. Estimated attributable risk proportions ranged from 8% to 20%. Conclusions Residential dampness and mold are associated with substantial and statistically significant increases in both respiratory infections and bronchitis. If these associations were confirmed as causal, effective control of dampness and mold in buildings would prevent a substantial proportion of respiratory infections. PMID:21078183

  1. Association of residential dampness and mold with respiratory tract infections and bronchitis: a meta-analysis

    SciTech Connect

    Fisk, William J.; Eliseeva, Ekaterina A.; Mendell, Mark J.

    2010-11-15

    bias was evident. Estimated attributable risk proportions ranged from 8% to 20%. Residential dampness and mold are associated with substantial and statistically significant increases in both respiratory infections and bronchitis. If these associations were confirmed as causal, effective control of dampness and mold in buildings would prevent a substantial proportion of respiratory infections.

  2. Building America

    SciTech Connect

    Brad Oberg

    2010-12-31

    IBACOS researched the constructability and viability issues of using high performance windows as one component of a larger approach to building houses that achieve the Building America 70% energy savings target.

  3. Updating Bearing Stiffness and Damping Coefficients of a Rotor System

    NASA Astrophysics Data System (ADS)

    Chouksey, M.; Dutt, J. K.; Modak, S. V.

    2013-10-01

    Finite element (FE) models of structures have been quite useful in both static and dynamic analyses of structures. However, quite often, these models are not reliable enough since predictions based on them may not be found to have acceptable correlation with experimentally obtained data. This paper attempts updating of bearing radial and tilt stiffness as well as damping parameters of a rotor system by using inverse eigen sensitivity method (IESM). Non-proportional viscous damping model has been used in modelling damping coefficients of bearings. The state space form of equations of motion of the system is used in applying the IESM for model updating. The results show that both stiffness and damping coefficients of bearings can be effectively found out by using the IESM. The method is found to update the eigenvalues quite well even under the presence of measurement noise.

  4. Analysis of coils of wire rope arranged for passive damping

    NASA Technical Reports Server (NTRS)

    Cutchins, M. A.; Cochran, J. E., Jr.; Kumar, K.; Fitz-Coy, N. G.; Tinker, M. L.

    1988-01-01

    Vibration dampers constructed with multiple loops of wire rope are studied. The literature on such devices is reviewed briefly, and dynamic and static models of them are examined. Fundamental and advanced NASTRAN models for wire rope damping are considered.

  5. A study of material damping in large space structures

    NASA Technical Reports Server (NTRS)

    Highsmith, A. L.; Allen, D. H.

    1989-01-01

    A constitutive model was developed for predicting damping as a function of damage in continuous fiber reinforced laminated composites. The damage model is a continuum formulation, and uses internal state variables to quantify damage and its subsequent effect on material response. The model is sensitive to the stacking sequence of the laminate. Given appropriate baseline data from unidirectional material, and damping as a function of damage in one crossply laminate, damage can be predicted as a function of damage in other crossply laminates. Agreement between theory and experiment was quite good. A micromechanics model was also developed for examining the influence of damage on damping. This model explicitly includes crack surfaces. The model provides reasonable predictions of bending stiffness as a function of damage. Damping predictions are not in agreement with the experiment. This is thought to be a result of dissipation mechanisms such as friction, which are not presently included in the analysis.

  6. Landau damping of Langmuir twisted waves with kappa distributed electrons

    SciTech Connect

    Arshad, Kashif Aman-ur-Rehman; Mahmood, Shahzad

    2015-11-15

    The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and are illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].

  7. The moment problem and vibrations damping of beams and plates

    SciTech Connect

    Atamuratov, Andrey G.; Muravey, Leonid A.

    2016-06-08

    Beams and plates are the elements of different complex mechanical structures, for example, pipelines and aerospace platforms. That is why the problem of damping of their vibrations caused by unwanted perturbations is actual task.

  8. Damping Optimization for Linear Vibrating Systems Using Dimension Reduction

    NASA Astrophysics Data System (ADS)

    Benner, Peter; Tomljanović, Zoran; Truhar, Ninoslav

    We consider a mathematical model of a linear vibrational system described by the second-order system of differential equations Mddot{x} + Ddot{x} + Kx = 0, where M, K and D are positive definite matrices, called mass, stiffness and damping, respectively. We are interested in finding an optimal damping matrix which will damp a certain part of the undamped eigenfrequencies. For this we use a minimization criterion which minimizes the average total energy of the system. This is equivalent to the minimization of the trace of the solution of a corresponding Lyapunov equation. In this paper we consider an algorithm for the efficient optimization of the damping positions based on dimension reduction techniques. Numerical results illustrate the efficiency of our approach.

  9. Mooring Line Damping Estimation for a Floating Wind Turbine

    PubMed Central

    Qiao, Dongsheng; Ou, Jinping

    2014-01-01

    The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design. PMID:25243231

  10. Mooring line damping estimation for a floating wind turbine.

    PubMed

    Qiao, Dongsheng; Ou, Jinping

    2014-01-01

    The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

  11. An Active Damping at Blade Resonances Using Piezoelectric Transducers

    NASA Technical Reports Server (NTRS)

    Choi, Benjamin; Morrison, Carlos; Duffy, Kirsten

    2008-01-01

    The NASA Glenn Research Center (GRC) is developing an active damping at blade resonances using piezoelectric structure to reduce excessive vibratory stresses that lead to high cycle fatigue (HCF) failures in aircraft engine turbomachinery. Conventional passive damping work was shown first on a nonrotating beam made by Ti-6A1-4V with a pair of identical piezoelectric patches, and then active feedback control law was derived in terms of inductor, resister, and capacitor to control resonant frequency only. Passive electronic circuit components and adaptive feature could be easily programmable into control algorithm. Experimental active damping was demonstrated on two test specimens achieving significant damping on tip displacement and patch location. Also a multimode control technique was shown to control several modes.

  12. Influence of damping on quantum interference - An exactly soluble model

    NASA Technical Reports Server (NTRS)

    Caldeira, A. O.; Leggett, A. J.

    1985-01-01

    This paper reports the result of a calculation which shows the effect of damping on the quantum interference of two Gaussian wave packets in a harmonic potential. The influence-functional method, which seems to be the most appropriate one for this kind of calculation, is used. It is shown that quantum-interference effects are severely diminished by the presence of damping even when its influence on the system is only light. The corrections to the undamped formulas are always expressible in terms of the phenomenological damping constant, the temperature (in the high-temperature limit), the cutoff frequency of the reservoir oscillators, and the mean number of quanta of energy intially present in the system. Both weakly and strongly damped systems are analyzed in the regime of low and high temperatures.

  13. Estimation of full modal damping matrices from complex test modes

    NASA Technical Reports Server (NTRS)

    Hasselman, T. K.; Chrostowski, J. D.; Pappa, Richard

    1993-01-01

    This paper describes the refinements of a previously published method for estimating a full modal damping matrix from complex test modes. It also documents application of the refined method to a structure where complex test modes were derived by the ERA method from multi-input random vibration test data. A numerical example based on simulated test data is presented to demonstrate the validity of the method. The application using real data was not successful, presumably because of noise in the small phase angles of the measured complex modes. Alternative test and data reduction procedures are suggested as possible remedies to the problem. A careful analysis of measurement and data processing errors should be made to examine basic feasibility before implementing the alternative procedures. The ability to estimate a full modal damping matrix is considered important for the preflight estimation of on-orbit damping, and for the synthesis of structural damping from substructure tests.

  14. Measurements of Aerodynamic Damping in the MIT Transonic Rotor

    NASA Technical Reports Server (NTRS)

    Crawley, E. F.

    1981-01-01

    A method was developed and demonstrated for the direct measurement of aerodynamic forcing and aerodynamic damping of a transonic compressor. The method is based on the inverse solution of the structural dynamic equations of motion of the blade disk system in order to determine the forces acting on the system. The disturbing and damping forces acting on a given blade are determined if the equations of motion are expressed in individual blade coordinates. If the structural dynamic equations are transformed to multiblade coordinates, the damping can be measured for blade disk modes, and related to a reduced frequency and interblade phase angle. In order to measure the aerodynamic damping in this way, the free response to a known excitation is studied.

  15. Damping Experiment of Spinning Composite Plates with Embedded Viscoelastic Material

    NASA Technical Reports Server (NTRS)

    Mehmed, Oral; Kosmatka, John B.

    1997-01-01

    One way to increase gas turbine engine blade reliability and durability is to reduce blade vibration. It is well known that vibration reduction can be achieved by adding damping to metal and composite blade-disk systems. This experiment was done to investigate the use of integral viscoelastic damping treatments to reduce vibration of rotating composite fan blades. It is part of a joint research effort with NASA LeRC and the University of California, San Diego (UCSD). Previous vibration bench test results obtained at UCSD show that plates with embedded viscoelastic material had over ten times greater damping than similar untreated plates; and this was without a noticeable change in blade stiffness. The objectives of this experiment, were to verify the structural integrity of composite plates with viscoelastic material embedded between composite layers while under large steady forces from spinning, and to measure the damping and natural frequency variation with rotational speed.

  16. Extracting Damping Ratio from Dynamic Data and Numerical Solutions

    NASA Technical Reports Server (NTRS)

    Casiano, M. J.

    2016-01-01

    There are many ways to extract damping parameters from data or models. This Technical Memorandum provides a quick reference for some of the more common approaches used in dynamics analysis. Described are six methods of extracting damping from data: the half-power method, logarithmic decrement (decay rate) method, an autocorrelation/power spectral density fitting method, a frequency response fitting method, a random decrement fitting method, and a newly developed half-quadratic gain method. Additionally, state-space models and finite element method modeling tools, such as COMSOL Multiphysics (COMSOL), provide a theoretical damping via complex frequency. Each method has its advantages which are briefly noted. There are also likely many other advanced techniques in extracting damping within the operational modal analysis discipline, where an input excitation is unknown; however, these approaches discussed here are objective, direct, and can be implemented in a consistent manner.

  17. The effect of mechanical damping loads on disabling action tremor.

    PubMed

    Aisen, M L; Arnold, A; Baiges, I; Maxwell, S; Rosen, M

    1993-07-01

    Patients with severe action tremor have uncontrollable, relatively rapid oscillatory motion super-imposed on otherwise useable slower voluntary motor activity. Because a mechanical damper produces an opposing force proportional to velocity, applying damping loads to tremorous limbs should attenuate the (high-velocity) tremor component of movement while permitting the slower purposeful portion to proceed relatively unopposed. In this study, the effect of upper extremity damping in three degrees of freedom was examined in 10 patients with cerebellar action tremor due to multiple sclerosis or traumatic brain injury. Variable amounts of damping were applied by prototype energy-dissipating orthoses which generated resistive viscous loads by means of computer-controlled magnetic particle brakes. All patients experienced statistically and functionally significant tremor reduction with the application of damping.

  18. Synchrotron and collisional damping effects on runaway electron distributions

    NASA Astrophysics Data System (ADS)

    Paz-Soldan, C.; Eidietis, N.; Pace, D.; Cooper, C.; Shiraki, D.; Commaux, N.; Hollmann, E.; Moyer, R.; Granetz, R.; Embreus, O.; Fulop, T.; Stahl, A.; Wilkie, G.; Aleynikov, P.; Brennan, D. P.; Liu, C.

    2016-10-01

    Validated models of runaway electron (RE) dissipation are required to confidently approve safe ITER Q = 10 operation. DIII-D experiments using quiescent REs are exploring the importance of synchrotron and collisional damping terms to RE dissipation. New time and energy-resolved measurements of RE bremsstrahlung hard X-ray (HXR) emission reveal stark differences between high and low energy REs as damping terms are varied. Previously reported anomalously high RE dissipation only applies to low energy REs. At high energy (where synchrotron effects are strongest) low synchrotron damping cases reach higher peak RE energy despite weaker particle confinement. Low-energy RE decay is observed concurrently with high-energy RE growth. RE dissipation models predict bump-on-tail distributions whose properties depend on the damping terms. Measured HXR spectra are very broad, as expected for bump-on-tail distributions. Work supported by the U.S. DOE under DE-FC02-04ER54698.

  19. Airborne Cladosporium and other fungi in damp versus reference residences

    NASA Astrophysics Data System (ADS)

    Pasanen, A.-L.; Niininen, M.; Kalliokoski, P.; Nevalainen, A.; Jantunen, M. J.

    Our previous study (Nevalainen et al., 1991, Envir. Int.17, 299-302) showed that airborne counts of total viable fungal spores in damp residences did not remarkably differ from those in reference residences. The results of the present study confirmed this finding. Indoor air spore counts varied considerably from residence to residence and even within the same residence. Thus, the counts were only occasionally high in the damp residences. Counts of airborne Cladosporium spp. spores and yeast cells were significantly higher in the damp residences than in the reference ones. The difference of yeast cell counts between the residence groups was explained by the difference in outdoor air, whereas Cladosporium spp. spores were mainly derived from indoors. Prevalence of Aspergillus spp. spores was also slightly higher in the damp residences than in the reference ones.

  20. Gilbert damping of ferromagnetic metals incorporating inhomogeneous spin dynamics

    SciTech Connect

    Umetsu, Nobuyuki Miura, Daisuke; Sakuma, Akimasa

    2015-05-07

    The effects of inhomogeneous spin dynamics on magnetic damping in ferromagnetic metals are studied. On the basis of linear response theory, we derive the microscopic expression for the Gilbert damping term in a two-dimensional electron gas interacting with the magnetization via exchange coupling in the presence of Rashba spin-orbit coupling (SOC). In the spin wave propagating with the wave vector, q, the behavior of q-dependent damping can be explained in terms of both inter- and intra-band spin excitations. The spatially dependent damping torques originating from Rashba SOC that cancel out in a uniform precession system distort the circular orbit of a magnetization-precession trajectory in the presence of inhomogeneous spin dynamics.

  1. Resummation and the gluon damping rate in hot QCD

    SciTech Connect

    Pisarski, R.D.

    1990-08-01

    At high temperature a consistent perturbative expansion requires the resummation of an infinite subset of loop corrections into an effective expansion. This effective exansion is used to compute the gluon damping rate at leading order. 25 refs.

  2. Flywheel vibration isolation test using a variable-damping isolator

    NASA Astrophysics Data System (ADS)

    Oh, Hyun-Ung; Taniwaki, Shigemune; Kinjyo, Naofumi; Izawa, Katsuhiko

    2006-04-01

    This study demonstrates the isolation performance of a variable-damping isolator using a bio-metal fiber (BMF) valve to enhance the pointing performance of observation satellites by isolating disturbances induced by reaction wheel assemblies. Vibration isolation tests of the variable-damping isolator were performed using an air-floating wheel disturbance detector to investigate whether the isolator can actually isolate flywheel vibration. In this paper, we first present a recently developed variable-damping isolator with low power consumption, and a reaction wheel disturbance detector, fabricated in a previous study, which detects low-frequency disturbances. Next, we describe the effectiveness of the variable-damping isolator based on flywheel vibration isolation test results.

  3. An integrated methodology for optimizing structural composite damping

    NASA Technical Reports Server (NTRS)

    Saravanos, D. A.; Chamis, C. C.

    1989-01-01

    A method is presented for tailoring plate and shell composite structures for optimal forced damped dynamic response. The damping of specific vibration modes is optimized with respect to dynamic performance criteria including placement of natural frequencies and minimization of resonance amplitudes. The structural composite damping is synthesized from the properties of the constituent materials, laminate parameters, and structural geometry based on a specialty finite element. Application studies include the optimization of laminated composite beams and composite shells with fiber volume ratios and ply angles as design variables. The results illustrate the significance of damping tailoring to the dynamic performance of composite structures, and the effectiveness of the method in optimizing the structural dynamic response.

  4. Estimation of full modal damping matrices from complex test modes

    NASA Technical Reports Server (NTRS)

    Hasselman, T. K.; Chrostowski, J. D.; Pappa, Richard

    1993-01-01

    This paper describes the refinements of a previously published method for estimating a full modal damping matrix from complex test modes. It also documents application of the refined method to a structure where complex test modes were derived by the ERA method from multi-input random vibration test data. A numerical example based on simulated test data is presented to demonstrate the validity of the method. The application using real data was not successful, presumably because of noise in the small phase angles of the measured complex modes. Alternative test and data reduction procedures are suggested as possible remedies to the problem. A careful analysis of measurement and data processing errors should be made to examine basic feasibility before implementing the alternative procedures. The ability to estimate a full modal damping matrix is considered important for the preflight estimation of on-orbit damping, and for the synthesis of structural damping from substructure tests.

  5. Damping Rotor Nutation Oscillations in a Gyroscope with Magnetic Suspension

    NASA Technical Reports Server (NTRS)

    Komarov, Valentine N.

    1996-01-01

    A possibility of an effective damping of rotor nutations by modulating the field of the moment transducers in synchronism with the nutation frequency is considered. The algorithms for forming the control moments are proposed and their application is discussed.

  6. Modal parameter identification and damping ratio estimation from the full-scale measurements of a typical Tibetan wooden structure

    NASA Astrophysics Data System (ADS)

    Dai, Lu; Yang, Na; Law, S. S.; Yang, Qingshan

    2016-12-01

    Tibetan heritage buildings have a high historical and cultural value. They have endured adverse environmental loadings over hundreds of years without significant damage. However, there are few reports on their structural characteristics under normal environmental loadings and their behavior under dynamic loadings. In this research, a typical Tibetan wooden wall-frame building is selected to study its dynamic characteristics. Field measurements of the structure were conducted under environmental excitation to collect acceleration responses. The stochastic subspace identification (SSI) method was adopted to calculate the structural modal parameters and obtain the out-of-plane vibration characteristics of the slab and frames. The results indicated that the wall-frame structure had a lower out-of-plane stiffness and greater in-plane stiffness due to the presence of stone walls. Due to poor identified damping ratio estimates from the SSI method, a method based on the variance upper bound was proposed to complement the existing variance lower bound method for estimating the modal damping ratio to address the significant damping variability obtained from different points and measurements. The feasibility of the proposed method was illustrated with the measured data from the floor slab of the structure. The variance lower and upper bound methods both provided consistent results compared to those from the traditional SSI method.

  7. Dampness and mold in the indoor environment: implications for asthma.

    PubMed

    Sahakian, N M; Park, J-H; Cox-Ganser, J M

    2008-08-01

    This article presents epidemiologic findings pertinent to asthma and asthma-like symptoms in relation to exposure to dampness/mold in homes, schools, and workplaces. With regard to specific agents found in damp indoor environments that may play a role in asthma, it concentrates on mold (used synonymously with fungi) and includes some findings on bacteria. The literature on asthma in relation to dust mite or cockroach allergens is not addressed.

  8. Development of Damped Metal Matrix Composites for Advanced Structural Applications

    DTIC Science & Technology

    1990-04-01

    DTIP FiLE COPY Applied Research Laboratory (Dto 00 CD Technical Report NO DEVELOPMENT OF DAMPED METAL MATRIX COMPOSITES FOR ADVANCED STRUCTURAL...DEVELOPMENT OF DAMPED METAL MATRIX COMPOSITES FOR ADVANCED STRUCTURAL APPLICATIONS by Clark A. Updike Ram B. Bhagat Technical Report No. TR 90-004 April 1990... Metal Matrix Composites for Advanced Structural Applications 12 PERSONAL AUTHOR(S) C.A. Updike, R. Bhagat 1 3a TYPE OF REPORT 13b TIME COVERED 14. DATE

  9. Viscous damping of toroidal angular momentum in tokamaks

    SciTech Connect

    Stacey, W. M.

    2014-09-15

    The Braginskii viscous stress tensor formalism was generalized to accommodate non-axisymmetric 3D magnetic fields in general toroidal flux surface geometry in order to provide a representation for the viscous damping of toroidal rotation in tokamaks arising from various “neoclassical toroidal viscosity” mechanisms. In the process, it was verified that the parallel viscosity contribution to damping toroidal angular momentum still vanishes even in the presence of toroidal asymmetries, unless there are 3D radial magnetic fields.

  10. Composite slip table of dissimilar materials for damping longitudinal modes

    DOEpatents

    Gregory, Danny L.; Priddy, Tommy G.; Smallwood, David O.; Woodall, Tommy D.

    1991-01-01

    A vibration slip table for use in a vibration testing apparatus. The table s comprised of at least three composite layers of material; a first metal layer, a second damping layer, and a third layer having a high acoustic velocity relative to the first layer. The different acoustic velocities between the first and third layers cause relative shear displacements between the layers with the second layer damping the displacements between the first and third layers to reduce the table longitudinal vibration modes.

  11. Damping characteristics of a reentry vehicle at hypersonic velocities

    NASA Astrophysics Data System (ADS)

    Adamov, N. P.; Puzyrev, L. N.; Kharitonov, A. M.; Chasovnikov, E. A.; Dyad'kin, A. A.; Krylov, A. N.

    2014-09-01

    The experimental equipment, model, test conditions, and methods used for determining the streamwise damping on a setup with free oscillations on rolling bearings are described. Characteristics of aerodynamic damping of the model with two positions of the rotation axis and Mach numbers M∞ = 2, 4, and 6 are measured. Irregular oscillations of the model with a greater displacement of the rotation axis with respect to the longitudinal axis are found to arise at M∞ = 2.

  12. Landau damping of geodesic acoustic mode in toroidally rotating tokamaks

    SciTech Connect

    Ren, Haijun; Cao, Jintao

    2015-06-15

    Geodesic acoustic mode (GAM) is analyzed by using modified gyro-kinetic (MGK) equation applicable to low-frequency microinstabilities in a rotating axisymmetric plasma. Dispersion relation of GAM in the presence of arbitrary toroidal Mach number is analytically derived. The effects of toroidal rotation on the GAM frequency and damping rate do not depend on the orientation of equilibrium flow. It is shown that the toroidal Mach number M increases the GAM frequency and dramatically decreases the Landau damping rate.

  13. Beliaev damping of quasiparticles in a Bose-Einstein condensate.

    PubMed

    Katz, N; Steinhauer, J; Ozeri, R; Davidson, N

    2002-11-25

    We report a measurement of the suppression of collisions of quasiparticles with ground state atoms within a Bose-Einstein condensate at low momentum. These collisions correspond to Beliaev damping of the excitations, in the previously unexplored regime of the continuous quasiparticle energy spectrum. We use a hydrodynamic simulation of the expansion dynamics, with the Beliaev damping cross section, in order to confirm the assumptions of our analysis.

  14. An efficient frequency response solution for nonproportionally damped systems

    NASA Technical Reports Server (NTRS)

    Conti, Paul; Rule, William K.

    1987-01-01

    A method is presented to accurately and economically calculate steady state frequency responses based on the analysis of large finite element models with nonproportional damping effects. The new method is a hybrid of the traditional nonproportional and proportional damping solution methods. It captures the advantages of each computational approach without the burden of their respective shortcomings, as demonstrated with comparative analysis performed on a large finite element model.

  15. Inverse design of nonlinearity in energy harvesters for optimum damping

    NASA Astrophysics Data System (ADS)

    Ghandchi Tehrani, Maryam; Elliott, S. J.

    2016-09-01

    This paper presents the inverse design method for the nonlinearity in an energy harvester in order to achieve an optimum damping. A single degree-of-freedom electromechanical oscillator is considered as an energy harvester, which is subjected to a harmonic base excitation. The harvester has a limited throw due to the physical constraint of the device, which means that the amplitude of the relative displacement between the mass of the harvester and the base cannot exceed a threshold when the device is driven at resonance and beyond a particular amplitude. This physical constraint requires the damping of the harvester to be adjusted for different excitation amplitudes, such that the relative displacement is controlled and maintained below the limit. For example, the damping can be increased to reduce the amplitude of the relative displacement. For high excitation amplitudes, the optimum damping is, therefore, dependent on the amplitude of the base excitation, and can be synthesised by a nonlinear function. In this paper, a nonlinear function in the form of a bilinear is considered to represent the damping model of the device. A numerical optimisation using Matlab is carried out to fit a curve to the amplitude-dependent damping in order to determine the optimum bilinear model. The nonlinear damping is then used in the time-domain simulations and the relative displacement and the average harvested power are obtained. It is demonstrated that the proposed nonlinear damping can maintain the relative displacement of the harvester at its maximum level for a wide range of excitation, therefore providing the optimum condition for power harvesting.

  16. Automated dynamic analytical model improvement for damped structures

    NASA Technical Reports Server (NTRS)

    Fuh, J. S.; Berman, A.

    1985-01-01

    A method is described to improve a linear nonproportionally damped analytical model of a structure. The procedure finds the smallest changes in the analytical model such that the improved model matches the measured modal parameters. Features of the method are: (1) ability to properly treat complex valued modal parameters of a damped system; (2) applicability to realistically large structural models; and (3) computationally efficiency without involving eigensolutions and inversion of a large matrix.

  17. Healthy Buildings?

    ERIC Educational Resources Information Center

    Grubb, Deborah

    Health problems related to school buildings can be categorized in five major areas: sick-building syndrome; health-threatening building materials; environmental hazards such as radon gas and asbestos; lead poisoning; and poor indoor air quality due to smoke, chemicals, and other pollutants. This paper provides an overview of these areas,…

  18. An optimization study for viscous dampers between adjacent buildings

    NASA Astrophysics Data System (ADS)

    Kandemir-Mazanoglu, Elif Cagda; Mazanoglu, Kemal

    2017-05-01

    This paper investigates optimum viscous damper capacity and number for prevention of one-sided structural pounding between two adjacent buildings under earthquake motion. The buildings assumed as shear-type structures are modeled by using lumped mass-stiffness technique. Impact forces due to pounding is simulated by nonlinear elastic spring approximation called Hertz model. A parametric study is conducted by varying storey number and stiffness of buildings in addition to the capacity of the viscous dampers. Pounding force and supplemental damping ratio for each case are presented based upon newly defined nondimensional natural frequency parameter ratio. An optimization procedure for determination of viscous damper capacity is developed based on modified supplemental damping ratio equation. Results are compared with each other to clarify the effect of variation in building parameters on pounding forces and viscous damper capacity.

  19. On eigenproblem solution of damped vibrations associated with gyroscopic moments

    NASA Astrophysics Data System (ADS)

    ElBeheiry, E. M.

    2009-02-01

    A new efficient approach is presented for solving the quadratic eigenvalue problem of weakly, nonproportionally damped vibration systems. In the analysis of these systems, gyroscopic moments and external damping are both considered. Traditional restriction of symmetry of inertia, damping and stiffness matrices is slightly relaxed. A second-order perturbation theory is developed such that the perturbed solution is based on the eigensolution of an unperturbed subproblem. This subproblem considers the unperturbed system in two different forms: (i) a conservative, gyroscopic part of an original problem, or (ii) a nonconservative, gyroscopic part of an original problem that is proportionally damped. To cope with asymmetry of the system matrices, a Duncan's like state formulation is used to bring these matrices into a suitable form for perturbations. Two numerical examples are introduced for explaining the detailed implementation of the presented approach. Additionally, a practical problem of rotor supported by two tilting pad-bearings is investigated. The eigensolutions obtained by the current approach match, to a great extent, other solutions obtained by time-consuming exact methods. The investigation procedure given here gives a framework to handle vibration problems of weakly nonproportional damping and/or weakly asymmetric inertia, damping and stiffness matrices.

  20. Reducing extrinsic damping of surface acoustic waves at gigahertz frequencies

    NASA Astrophysics Data System (ADS)

    Gelda, Dhruv; Sadhu, Jyothi; Ghossoub, Marc G.; Ertekin, Elif; Sinha, Sanjiv

    2016-04-01

    High-frequency surface acoustic waves (SAWs) in the gigahertz range can be generated using absorption from an ultrafast laser in a patterned metallic grating on a substrate. Reducing the attenuation at these frequencies can yield better sensors as well as enable them to better probe phonon and electron-phonon interactions near surfaces. It is not clear from existing experiments which mechanisms dominate damping at high frequencies. We calculate damping times of SAWs due to various mechanisms in the 1-100 GHz range to find that mechanical loading of the grating on the substrate dominates dissipation by radiating energy from the surface into the bulk. To overcome this and enable future measurements to probe intrinsic damping, we propose incorporating distributed acoustic Bragg reflectors in the experimental structure. Layers of alternating materials with contrasting acoustic impedances embedded a wavelength away from the surface serve to reflect energy back to the surface. Using numerical simulations, we show that a single Bragg reflector is sufficient to increase the energy density at the surface by more than five times. We quantify the resulting damping time to find that it is longer than the intrinsic damping time. The proposed structure can enable future measurements of intrinsic damping in SAWs at ˜100 GHz.