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Sample records for simulation-based interval two-stage

  1. A simulation-based interval two-stage stochastic model for agricultural non-point source pollution control through land retirement.

    PubMed

    Luo, B; Li, J B; Huang, G H; Li, H L

    2006-05-15

    This study presents a simulation-based interval two-stage stochastic programming (SITSP) model for agricultural non-point source (NPS) pollution control through land retirement under uncertain conditions. The modeling framework was established by the development of an interval two-stage stochastic program, with its random parameters being provided by the statistical analysis of the simulation outcomes of a distributed water quality approach. The developed model can deal with the tradeoff between agricultural revenue and "off-site" water quality concern under random effluent discharge for a land retirement scheme through minimizing the expected value of long-term total economic and environmental cost. In addition, the uncertainties presented as interval numbers in the agriculture-water system can be effectively quantified with the interval programming. By subdividing the whole agricultural watershed into different zones, the most pollution-related sensitive cropland can be identified and an optimal land retirement scheme can be obtained through the modeling approach. The developed method was applied to the Swift Current Creek watershed in Canada for soil erosion control through land retirement. The Hydrological Simulation Program-FORTRAN (HSPF) was used to simulate the sediment information for this case study. Obtained results indicate that the total economic and environmental cost of the entire agriculture-water system can be limited within an interval value for the optimal land retirement schemes. Meanwhile, a best and worst land retirement scheme was obtained for the study watershed under various uncertainties.

  2. Interval estimation of binomial proportion in clinical trials with a two-stage design.

    PubMed

    Tsai, Wei-Yann; Chi, Yunchan; Chen, Chia-Min

    2008-01-15

    Generally, a two-stage design is employed in Phase II clinical trials to avoid giving patients an ineffective drug. If the number of patients with significant improvement, which is a binomial response, is greater than a pre-specified value at the first stage, then another binomial response at the second stage is also observed. This paper considers interval estimation of the response probability when the second stage is allowed to continue. Two asymptotic interval estimators, Wald and score, as well as two exact interval estimators, Clopper-Pearson and Sterne, are constructed according to the two binomial responses from this two-stage design, where the binomial response at the first stage follows a truncated binomial distribution. The mean actual coverage probability and expected interval width are employed to evaluate the performance of these interval estimators. According to the comparison results, the score interval is recommended for both Simon's optimal and minimax designs.

  3. A Monte Carlo simulation based two-stage adaptive resonance theory mapping approach for offshore oil spill vulnerability index classification.

    PubMed

    Li, Pu; Chen, Bing; Li, Zelin; Zheng, Xiao; Wu, Hongjing; Jing, Liang; Lee, Kenneth

    2014-09-15

    In this paper, a Monte Carlo simulation based two-stage adaptive resonance theory mapping (MC-TSAM) model was developed to classify a given site into distinguished zones representing different levels of offshore Oil Spill Vulnerability Index (OSVI). It consisted of an adaptive resonance theory (ART) module, an ART Mapping module, and a centroid determination module. Monte Carlo simulation was integrated with the TSAM approach to address uncertainties that widely exist in site conditions. The applicability of the proposed model was validated by classifying a large coastal area, which was surrounded by potential oil spill sources, based on 12 features. Statistical analysis of the results indicated that the classification process was affected by multiple features instead of one single feature. The classification results also provided the least or desired number of zones which can sufficiently represent the levels of offshore OSVI in an area under uncertainty and complexity, saving time and budget in spill monitoring and response.

  4. A queuing-theory-based interval-fuzzy robust two-stage programming model for environmental management under uncertainty

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Li, Y. P.; Huang, G. H.

    2012-06-01

    In this study, a queuing-theory-based interval-fuzzy robust two-stage programming (QB-IRTP) model is developed through introducing queuing theory into an interval-fuzzy robust two-stage (IRTP) optimization framework. The developed QB-IRTP model can not only address highly uncertain information for the lower and upper bounds of interval parameters but also be used for analysing a variety of policy scenarios that are associated with different levels of economic penalties when the promised targets are violated. Moreover, it can reflect uncertainties in queuing theory problems. The developed method has been applied to a case of long-term municipal solid waste (MSW) management planning. Interval solutions associated with different waste-generation rates, different waiting costs and different arriving rates have been obtained. They can be used for generating decision alternatives and thus help managers to identify desired MSW management policies under various economic objectives and system reliability constraints.

  5. Short-interval two-stage approach to primary total knee arthroplasty for acutely septic osteoarthritic knees.

    PubMed

    Hochreiter, Bettina; Strahm, Carol; Behrend, Henrik

    2016-10-01

    Treatment strategies for advanced knee osteoarthritis with coexistent joint infection are not well established. While in periprosthetic joint infection the two-stage approach has been studied extensively, only few case reports on two-stage total knee arthroplasty (TKA) for knee osteoarthritis with coexistent joint infection have been published. The purpose of this paper was to report on our method of implementing a two-stage TKA with intervening antibiotic-loaded articulating cement spacers and a short interval between first- and second-stage procedures to treat two patients with Staphylococcus aureus-infected end-stage knee osteoarthritis. Consistent infection eradication was found at a 1-year follow-up with postoperative range of motion and knee scores comparing favourably with those of other case series. Level of evidence V.

  6. A manufacturing quality assessment model based-on two stages interval type-2 fuzzy logic

    NASA Astrophysics Data System (ADS)

    Purnomo, Muhammad Ridwan Andi; Helmi Shintya Dewi, Intan

    2016-01-01

    This paper presents the development of an assessment models for manufacturing quality using Interval Type-2 Fuzzy Logic (IT2-FL). The proposed model is developed based on one of building block in sustainable supply chain management (SSCM), which is benefit of SCM, and focuses more on quality. The proposed model can be used to predict the quality level of production chain in a company. The quality of production will affect to the quality of product. Practically, quality of production is unique for every type of production system. Hence, experts opinion will play major role in developing the assessment model. The model will become more complicated when the data contains ambiguity and uncertainty. In this study, IT2-FL is used to model the ambiguity and uncertainty. A case study taken from a company in Yogyakarta shows that the proposed manufacturing quality assessment model can work well in determining the quality level of production.

  7. A two-stage mixed-integer fuzzy programming with interval-valued membership functions approach for flood-diversion planning.

    PubMed

    Wang, S; Huang, G H

    2013-03-15

    Flood disasters have been extremely severe in recent decades, and they account for about one third of all natural catastrophes throughout the world. In this study, a two-stage mixed-integer fuzzy programming with interval-valued membership functions (TMFP-IMF) approach is developed for flood-diversion planning under uncertainty. TMFP-IMF integrates the fuzzy flexible programming, two-stage stochastic programming, and integer programming within a general framework. A concept of interval-valued fuzzy membership function is introduced to address complexities of system uncertainties. TMFP-IMF can not only deal with uncertainties expressed as fuzzy sets and probability distributions, but also incorporate pre-regulated water-diversion policies directly into its optimization process. TMFP-IMF is applied to a hypothetical case study of flood-diversion planning for demonstrating its applicability. Results indicate that reasonable solutions can be generated for binary and continuous variables. A variety of flood-diversion and capacity-expansion schemes can be obtained under four scenarios, which enable decision makers (DMs) to identify the most desired one based on their perceptions and attitudes towards the objective-function value and constraints.

  8. Optimal land use management for soil erosion control by using an interval-parameter fuzzy two-stage stochastic programming approach.

    PubMed

    Han, Jing-Cheng; Huang, Guo-He; Zhang, Hua; Li, Zhong

    2013-09-01

    Soil erosion is one of the most serious environmental and public health problems, and such land degradation can be effectively mitigated through performing land use transitions across a watershed. Optimal land use management can thus provide a way to reduce soil erosion while achieving the maximum net benefit. However, optimized land use allocation schemes are not always successful since uncertainties pertaining to soil erosion control are not well presented. This study applied an interval-parameter fuzzy two-stage stochastic programming approach to generate optimal land use planning strategies for soil erosion control based on an inexact optimization framework, in which various uncertainties were reflected. The modeling approach can incorporate predefined soil erosion control policies, and address inherent system uncertainties expressed as discrete intervals, fuzzy sets, and probability distributions. The developed model was demonstrated through a case study in the Xiangxi River watershed, China's Three Gorges Reservoir region. Land use transformations were employed as decision variables, and based on these, the land use change dynamics were yielded for a 15-year planning horizon. Finally, the maximum net economic benefit with an interval value of [1.197, 6.311] × 10(9) $ was obtained as well as corresponding land use allocations in the three planning periods. Also, the resulting soil erosion amount was found to be decreased and controlled at a tolerable level over the watershed. Thus, results confirm that the developed model is a useful tool for implementing land use management as not only does it allow local decision makers to optimize land use allocation, but can also help to answer how to accomplish land use changes.

  9. Two stage liquefaction of coal

    DOEpatents

    Neuworth, Martin B.

    1981-01-01

    A two stage coal liquefaction process and apparatus comprising hydrogen donor solvent extracting, solvent deashing, and catalytic hydrocracking. Preferrably, the catalytic hydrocracking is performed in an ebullating bed hydrocracker.

  10. Two stage coal gasification plant

    SciTech Connect

    Shoebotham, N.M.

    1984-06-26

    This invention relates to a two stage coal gasification plant which comprises a gasifier 1 and a predistillation retort 2. The gasifier has a plurality of gas extraction outlets 4 located in the periphery thereof which feed into a manifold 5 from where a percentage of the gas from the gasifier is extracted. Gas from the predistillation retort is extracted through an outlet near the top of the retort. An agitator 8 is provided for agitation of the coal in the agglomeration zone. The agitator is preferably automatically controlled by means of a temperature sensing device 10 located on an arm thereof.

  11. Two stage to orbit design

    NASA Technical Reports Server (NTRS)

    1991-01-01

    A preliminary design of a two-stage to orbit vehicle was conducted with the requirements to carry a 10,000 pound payload into a 300 mile low-earth orbit using an airbreathing first stage, and to take off and land unassisted on a 15,000 foot runway. The goal of the design analysis was to produce the most efficient vehicle in size and weight which could accomplish the mission requirements. Initial parametric analysis indicated that the weight of the orbiter and the transonic performance of the system were the two parameters that had the largest impact on the design. The resulting system uses a turbofan ramjet powered first stage to propel a scramjet and rocket powered orbiter to the stage point of Mach 6 to 6.5 at an altitude of 90,000 ft.

  12. Two-stage coal liquefaction process

    DOEpatents

    Skinner, Ronald W.; Tao, John C.; Znaimer, Samuel

    1985-01-01

    An improved SRC-I two-stage coal liquefaction process which improves the product slate is provided. Substantially all of the net yield of 650.degree.-850.degree. F. heavy distillate from the LC-Finer is combined with the SRC process solvent, substantially all of the net 400.degree.-650.degree. F. middle distillate from the SRC section is combined with the hydrocracker solvent in the LC-Finer, and the initial boiling point of the SRC process solvent is increased sufficiently high to produce a net yield of 650.degree.-850.degree. F. heavy distillate of zero for the two-stage liquefaction process.

  13. Two stage sorption of sulfur compounds

    DOEpatents

    Moore, William E.

    1992-01-01

    A two stage method for reducing the sulfur content of exhaust gases is disclosed. Alkali- or alkaline-earth-based sorbent is totally or partially vaporized and introduced into a sulfur-containing gas stream. The activated sorbent can be introduced in the reaction zone or the exhaust gases of a combustor or a gasifier. High efficiencies of sulfur removal can be achieved.

  14. Two-Stage Series-Resonant Inverter

    NASA Technical Reports Server (NTRS)

    Stuart, Thomas A.

    1994-01-01

    Two-stage inverter includes variable-frequency, voltage-regulating first stage and fixed-frequency second stage. Lightweight circuit provides regulated power and is invulnerable to output short circuits. Does not require large capacitor across ac bus, like parallel resonant designs. Particularly suitable for use in ac-power-distribution system of aircraft.

  15. Two stage surgical procedure for root coverage.

    PubMed

    George, Anjana Mary; Rajesh, K S; Hegde, Shashikanth; Kumar, Arun

    2012-07-01

    Gingival recession may present problems that include root sensitivity, esthetic concern, and predilection to root caries, cervical abrasion and compromising of a restorative effort. When marginal tissue health cannot be maintained and recession is deep, the need for treatment arises. This literature has documented that recession can be successfully treated by means of a two stage surgical approach, the first stage consisting of creation of attached gingiva by means of free gingival graft, and in the second stage, a lateral sliding flap of grafted tissue to cover the recession. This indirect technique ensures development of an adequate width of attached gingiva. The outcome of this technique suggests that two stage surgical procedures are highly predictable for root coverage in case of isolated deep recession and lack of attached gingiva.

  16. Two-Stage Free Electron Laser Research.

    DTIC Science & Technology

    1984-10-24

    Ctmetenar an reverse ode It ne*eey aud identify fo black nmber) Free electron laser, two-stage free electron laser, quasioptical cavity, helical ...of very high intensity (_10 W/cm ). A quasioptical cavity concept has been developed to produce such a field. A helical wiggler is needed to excite...the TE waveguide mode in this cavity. Work is described on the development of a pfmanent magnet helical wiggler for this system. Off-axis electron

  17. Two Stage Gear Tooth Dynamics Program

    DTIC Science & Technology

    1989-08-01

    cordi - tions and associated iteration prooedure become more complex. This is due to both the increased number of components and to the time for a...solved for each stage in the two stage solution . There are (3 + ntrrber of planets) degrees of freedom fcr eacb stage plus two degrees of freedom...should be devised. It should be noted that this is not minor task. In general, each stage plus an input or output shaft will have 2 times (4 + number

  18. Stepwise two-stage sample size adaptation.

    PubMed

    Wan, Hong; Ellenberg, Susan S; Anderson, Keaven M

    2015-01-15

    Several adaptive design methods have been proposed to reestimate sample size using the observed treatment effect after an initial stage of a clinical trial while preserving the overall type I error at the time of the final analysis. One unfortunate property of the algorithms used in some methods is that they can be inverted to reveal the exact treatment effect at the interim analysis. We propose using a step function with an inverted U-shape of observed treatment difference for sample size reestimation to lessen the information on treatment effect revealed. This will be referred to as stepwise two-stage sample size adaptation. This method applies calculation methods used for group sequential designs. We minimize expected sample size among a class of these designs and compare efficiency with the fully optimized two-stage design, optimal two-stage group sequential design, and designs based on promising conditional power. The trade-off between efficiency versus the improved blinding of the interim treatment effect will be discussed.

  19. Two-stage microbial community experimental design.

    PubMed

    Tickle, Timothy L; Segata, Nicola; Waldron, Levi; Weingart, Uri; Huttenhower, Curtis

    2013-12-01

    Microbial community samples can be efficiently surveyed in high throughput by sequencing markers such as the 16S ribosomal RNA gene. Often, a collection of samples is then selected for subsequent metagenomic, metabolomic or other follow-up. Two-stage study design has long been used in ecology but has not yet been studied in-depth for high-throughput microbial community investigations. To avoid ad hoc sample selection, we developed and validated several purposive sample selection methods for two-stage studies (that is, biological criteria) targeting differing types of microbial communities. These methods select follow-up samples from large community surveys, with criteria including samples typical of the initially surveyed population, targeting specific microbial clades or rare species, maximizing diversity, representing extreme or deviant communities, or identifying communities distinct or discriminating among environment or host phenotypes. The accuracies of each sampling technique and their influences on the characteristics of the resulting selected microbial community were evaluated using both simulated and experimental data. Specifically, all criteria were able to identify samples whose properties were accurately retained in 318 paired 16S amplicon and whole-community metagenomic (follow-up) samples from the Human Microbiome Project. Some selection criteria resulted in follow-up samples that were strongly non-representative of the original survey population; diversity maximization particularly undersampled community configurations. Only selection of intentionally representative samples minimized differences in the selected sample set from the original microbial survey. An implementation is provided as the microPITA (Microbiomes: Picking Interesting Taxa for Analysis) software for two-stage study design of microbial communities.

  20. Two-Stage Reduction Of Dynamical Models

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.; Tsuha, Walter S.

    1993-01-01

    No longer necessary to solve eigenvalue problems of high order. Component-mode projection-and-assembly model-reduction (COMPARE) method provides approximation of dynamics of vibrations of complicated, multiple flexible bodies by use of mathematical models of reduced order. Incorporates component-mode synthesis (CMS) method and enhanced projection-and-assembly (EP&A) method, described in "Enhanced Method of Reduction of Dynamical Models" (NPO-18402), providing for somewhat simplified two-stage process in which order of applicable mathematical models reduced. Reduced-order models used to design algorithms of control systems to suppress vibrations or otherwise control structure.

  1. Two stage indirect evaporative cooling system

    SciTech Connect

    Bourne, Richard C.; Lee, Brian E.; Callaway, Duncan

    2005-08-23

    A two stage indirect evaporative cooler that moves air from a blower mounted above the unit, vertically downward into dry air passages in an indirect stage and turns the air flow horizontally before leaving the indirect stage. After leaving the dry passages, a major air portion travels into the direct stage and the remainder of the air is induced by a pressure drop in the direct stage to turn 180.degree. and returns horizontally through wet passages in the indirect stage and out of the unit as exhaust air.

  2. Two-Stage Passive Vibration Isolator

    NASA Technical Reports Server (NTRS)

    Goullioud, Renaud; Gursel, Yekta; Neville, Timothy; Bronowicki, Allen J.; Platus, David; MacDonald, Rhonda

    2008-01-01

    The design and testing of a structural system were implemented to hold the optics of the planned Space Interferometry Mission (SIM) at positions and orientations characterized by vibrational translation and rotation errors of no more than a few nanometers or a few milliarcseconds, respectively. Much of the effort was devoted to a test bed for verifying the predicted behavior of a vibration- isolation structural subsystem working together with an active control system for positioning and orienting the SIM optics. There was considerable emphasis on the vibration-isolation subsystem, which was passive and comprised two stages. The main sources of vibration were six reaction wheels in an assembly denoted the "backpack." The first vibration-isolation stage consisted of hexapod isolator mounts - one for each reaction wheel - characterized by a natural vibration frequency of 10 Hz. The second stage was a set of three beams, disposed between the backpack and the structure that held the SIM optics, that were flexured such that they transmitted only bending loads, with a natural vibrational frequency and damping of about 5 Hz and 4 percent, respectively. Preliminary test results were presented and characterized as demonstrating the effectiveness of the two-stage vibration-isolation design.

  3. Two stage gear tooth dynamics program

    NASA Technical Reports Server (NTRS)

    Boyd, Linda S.

    1989-01-01

    The epicyclic gear dynamics program was expanded to add the option of evaluating the tooth pair dynamics for two epicyclic gear stages with peripheral components. This was a practical extension to the program as multiple gear stages are often used for speed reduction, space, weight, and/or auxiliary units. The option was developed for either stage to be a basic planetary, star, single external-external mesh, or single external-internal mesh. The two stage system allows for modeling of the peripherals with an input mass and shaft, an output mass and shaft, and a connecting shaft. Execution of the initial test case indicated an instability in the solution with the tooth paid loads growing to excessive magnitudes. A procedure to trace the instability is recommended as well as a method of reducing the program's computation time by reducing the number of boundary condition iterations.

  4. Two-stage eutectic metal brushes

    DOEpatents

    Hsu, John S [Oak Ridge, TN

    2009-07-14

    A two-stage eutectic metal brush assembly having a slip ring rigidly coupled to a shaft, the slip ring being electrically coupled to first voltage polarity. At least one brush is rigidly coupled to a second ring and slidingly engaged to the slip ring. Eutectic metal at least partially fills an annulus between the second ring and a stationary ring. At least one conductor is rigidly coupled to the stationary ring and electrically coupled to a second voltage polarity. Electrical continuity is maintained between the first voltage polarity and the second voltage polarity. Periodic rotational motion is present between the stationary ring and the second ring. Periodic rotational motion is also present between the brush and the slip ring.

  5. Isokinetic evaluation after two-stage bicruciate reconstruction

    PubMed Central

    GiglioTakaes, Igor; Inada, Mauro Mituso; de Miranda, João Batista; Cunha, Sérgio Augusto; Piedade, Sérgio Rocha

    2014-01-01

    Objective: To assess the functional balance of the knee after bicruciate reconstruction and its correlation with clinical score. Methods: 14 patients (11 men and three women), mean age 29.9±7.65 years, mean BMI 26.2±2.51 kg/m2 underwent surgical reconstruction of the Posterior Cruciate Ligament (PCL) and Anterior Cruciate Ligament (ACL) in two stages, with a mean interval of 3 months between procedures. With a mean follow-up period of 27.33 months, the isokinetic knee analysis was performed at 60°/s and 180°/s and the Lysholm and Tegner scores were applied. Results: The Lysholm score was 86.8±11.1 points and the Tegner score showed a deficit of 30% compared to pre-injury level. In isokinetic evaluation, the deficit of the operated quadriceps average torque was 17.05% at 60°/s and 12.16% at 180°/s, while the average flexor torque deficit was 3.43% at 60°/s and 5.82% at 180°/s. Although it was observed torque deficit between members, there were no statistical differences regarding the functional balance between hamstrings and quadriceps. Conclusion: Although the results of isokinetic evaluation has shown a functional balance of the knee (flexor-extensor), which may have contributed to the good subjective Lysholm score in the bicruciate two-stage reconstruction, two-stage reconstruction did not restore the pre-injury functional level. Level of Evidence IV, Case Series. PMID:24644415

  6. Two-Stage Modelling Of Random Phenomena

    NASA Astrophysics Data System (ADS)

    Barańska, Anna

    2015-12-01

    The main objective of this publication was to present a two-stage algorithm of modelling random phenomena, based on multidimensional function modelling, on the example of modelling the real estate market for the purpose of real estate valuation and estimation of model parameters of foundations vertical displacements. The first stage of the presented algorithm includes a selection of a suitable form of the function model. In the classical algorithms, based on function modelling, prediction of the dependent variable is its value obtained directly from the model. The better the model reflects a relationship between the independent variables and their effect on the dependent variable, the more reliable is the model value. In this paper, an algorithm has been proposed which comprises adjustment of the value obtained from the model with a random correction determined from the residuals of the model for these cases which, in a separate analysis, were considered to be the most similar to the object for which we want to model the dependent variable. The effect of applying the developed quantitative procedures for calculating the corrections and qualitative methods to assess the similarity on the final outcome of the prediction and its accuracy, was examined by statistical methods, mainly using appropriate parametric tests of significance. The idea of the presented algorithm has been designed so as to approximate the value of the dependent variable of the studied phenomenon to its value in reality and, at the same time, to have it "smoothed out" by a well fitted modelling function.

  7. Residential Two-Stage Gas Furnaces - Do They Save Energy?

    SciTech Connect

    Lekov, Alex; Franco, Victor; Lutz, James

    2006-05-12

    Residential two-stage gas furnaces account for almost a quarter of the total number of models listed in the March 2005 GAMA directory of equipment certified for sale in the United States. Two-stage furnaces are expanding their presence in the market mostly because they meet consumer expectations for improved comfort. Currently, the U.S. Department of Energy (DOE) test procedure serves as the method for reporting furnace total fuel and electricity consumption under laboratory conditions. In 2006, American Society of Heating Refrigeration and Air-conditioning Engineers (ASHRAE) proposed an update to its test procedure which corrects some of the discrepancies found in the DOE test procedure and provides an improved methodology for calculating the energy consumption of two-stage furnaces. The objectives of this paper are to explore the differences in the methods for calculating two-stage residential gas furnace energy consumption in the DOE test procedure and in the 2006 ASHRAE test procedure and to compare test results to research results from field tests. Overall, the DOE test procedure shows a reduction in the total site energy consumption of about 3 percent for two-stage compared to single-stage furnaces at the same efficiency level. In contrast, the 2006 ASHRAE test procedure shows almost no difference in the total site energy consumption. The 2006 ASHRAE test procedure appears to provide a better methodology for calculating the energy consumption of two-stage furnaces. The results indicate that, although two-stage technology by itself does not save site energy, the combination of two-stage furnaces with BPM motors provides electricity savings, which are confirmed by field studies.

  8. Extraoral implants for orbit rehabilitation: a comparison between one-stage and two-stage surgeries.

    PubMed

    de Mello, M C L M P; Guedes, R; de Oliveira, J A P; Pecorari, V A; Abrahão, M; Dib, L L

    2014-03-01

    The aim of the study was to compare the osseointegration success rate and time for delivery of the prosthesis among cases treated by two-stage or one-stage surgery for orbit rehabilitation between 2003 and 2011. Forty-five patients were included, 31 males and 14 females; 22 patients had two-stage surgery and 23 patients had one-stage surgery. A total 138 implants were installed, 42 (30.4%) on previously irradiated bone. The implant survival rate was 96.4%, with a success rate of 99.0% among non-irradiated patients and 90.5% among irradiated patients. Two-stage patients received 74 implants with a survival rate of 94.6% (four implants lost); one-stage surgery patients received 64 implants with a survival rate of 98.4% (one implant lost). The median time interval between implant fixation and delivery of the prosthesis for the two-stage group was 9.6 months and for the one-stage group was 4.0 months (P < 0.001). The one-stage technique proved to be reliable and was associated with few risks and complications; the rate of successful osseointegration was similar to those reported in the literature. The one-stage technique should be considered a viable procedure that shortens the time to final rehabilitation and facilitates appropriate patient follow-up treatment.

  9. STARS A Two Stage High Gain Harmonic Generation FEL Demonstrator

    SciTech Connect

    M. Abo-Bakr; W. Anders; J. Bahrdt; P. Budz; K.B. Buerkmann-Gehrlein; O. Dressler; H.A. Duerr; V. Duerr; W. Eberhardt; S. Eisebitt; J. Feikes; R. Follath; A. Gaupp; R. Goergen; K. Goldammer; S.C. Hessler; K. Holldack; E. Jaeschke; Thorsten Kamps; S. Klauke; J. Knobloch; O. Kugeler; B.C. Kuske; P. Kuske; A. Meseck; R. Mitzner; R. Mueller; M. Neeb; A. Neumann; K. Ott; D. Pfluckhahn; T. Quast; M. Scheer; Th. Schroeter; M. Schuster; F. Senf; G. Wuestefeld; D. Kramer; Frank Marhauser

    2007-08-01

    BESSY is proposing a demonstration facility, called STARS, for a two-stage high-gain harmonic generation free electron laser (HGHG FEL). STARS is planned for lasing in the wavelength range 40 to 70 nm, requiring a beam energy of 325 MeV. The facility consists of a normal conducting gun, three superconducting TESLA-type acceleration modules modified for CW operation, a single stage bunch compressor and finally a two-stage HGHG cascaded FEL. This paper describes the faciliy layout and the rationale behind the operation parameters.

  10. Premixing and flash vaporization in a two-stage combustor

    SciTech Connect

    Sjoblom, B.G.A.

    1982-01-01

    A double recirculation zone two-stage combustor fitted with airblast atomizers has been investigated in a previous work. This paper describes further tests with premixing tubes in the secondary combustion zone. Flash vaporization was employed to ensure complete vaporization of the secondary fuel, which was heated to 600K by the combustor inlet air. 9 refs.

  11. Analysis of two-stage Joule-Thomson expansion

    NASA Astrophysics Data System (ADS)

    Narasaki, Katsuhiro

    2016-03-01

    To cool far infrared detectors for infrared observation or superconductor-insulator-superconductor (SIS) mixers for atmospheric observation, 1 K-class and 4 K-class coolers have been developed. These coolers consist of a two-stage Stirling cooler for pre-cooling and a Joule-Thomson (JT) cooler with a single JT valve. This paper presents descriptions of theoretical analyses based on enthalpy balance to elucidate the benefits of a two-stage JT valve type compared with those of a single JT valve type in a JT cooler. First, relational expressions for heat balance analysis of enthalpy for single-stage JT expansion are introduced. Then similar relational expressions for two-stage JT expansion are introduced under some assumptions. Results of heat balance analyses using several parameters demonstrated that, using two-stage JT expansion, the cooling capacity for a 1 K-class cooler is improved by 100%; that of a 4 K-class cooler is improved by about 30%.

  12. A two-stage dynamic model for visual tracking.

    PubMed

    Kristan, Matej; Kovacic, Stanislav; Leonardis, Aleš; Pers, Janez

    2010-12-01

    We propose a new dynamic model which can be used within blob trackers to track the target's center of gravity. A strong point of the model is that it is designed to track a variety of motions which are usually encountered in applications such as pedestrian tracking, hand tracking, and sports. We call the dynamic model a two-stage dynamic model due to its particular structure, which is a composition of two models: a liberal model and a conservative model. The liberal model allows larger perturbations in the target's dynamics and is able to account for motions in between the random-walk dynamics and the nearly constant-velocity dynamics. On the other hand, the conservative model assumes smaller perturbations and is used to further constrain the liberal model to the target's current dynamics. We implement the two-stage dynamic model in a two-stage probabilistic tracker based on the particle filter and apply it to two separate examples of blob tracking: 1) tracking entire persons and 2) tracking of a person's hands. Experiments show that, in comparison to the widely used models, the proposed two-stage dynamic model allows tracking with smaller number of particles in the particle filter (e.g., 25 particles), while achieving smaller errors in the state estimation and a smaller failure rate. The results suggest that the improved performance comes from the model's ability to actively adapt to the target's motion during tracking.

  13. Non-parametric Estimation of a Survival Function with Two-stage Design Studies.

    PubMed

    Li, Gang; Tseng, Chi-Hong

    2008-06-01

    The two-stage design is popular in epidemiology studies and clinical trials due to its cost effectiveness. Typically, the first stage sample contains cheaper and possibly biased information, while the second stage validation sample consists of a subset of subjects with accurate and complete information. In this paper, we study estimation of a survival function with right-censored survival data from a two-stage design. A non-parametric estimator is derived by combining data from both stages. We also study its large sample properties and derive pointwise and simultaneous confidence intervals for the survival function. The proposed estimator effectively reduces the variance and finite-sample bias of the Kaplan-Meier estimator solely based on the second stage validation sample. Finally, we apply our method to a real data set from a medical device post-marketing surveillance study.

  14. Two-Stage Variable Sample-Rate Conversion System

    NASA Technical Reports Server (NTRS)

    Tkacenko, Andre

    2009-01-01

    A two-stage variable sample-rate conversion (SRC) system has been pro posed as part of a digital signal-processing system in a digital com munication radio receiver that utilizes a variety of data rates. The proposed system would be used as an interface between (1) an analog- todigital converter used in the front end of the receiver to sample an intermediatefrequency signal at a fixed input rate and (2) digita lly implemented tracking loops in subsequent stages that operate at v arious sample rates that are generally lower than the input sample r ate. This Two-Stage System would be capable of converting from an input sample rate to a desired lower output sample rate that could be var iable and not necessarily a rational fraction of the input rate.

  15. Multifunctional two-stage riser fluid catalytic cracking process.

    PubMed

    Zhang, Jinhong; Shan, Honghong; Chen, Xiaobo; Li, Chunyi; Yang, Chaohe

    This paper described the discovering process of some shortcomings of the conventional fluid catalytic cracking (FCC) process and the proposed two-stage riser (TSR) FCC process for decreasing dry gas and coke yields and increasing light oil yield, which has been successfully applied in 12 industrial units. Furthermore, the multifunctional two-stage riser (MFT) FCC process proposed on the basis of the TSR FCC process was described, which were carried out by the optimization of reaction conditions for fresh feedstock and cycle oil catalytic cracking, respectively, by the coupling of cycle oil cracking and light FCC naphtha upgrading processes in the second-stage riser, and the specially designed reactor for further reducing the olefin content of gasoline. The pilot test showed that it can further improve the product quality, increase the diesel yield, and enhance the conversion of heavy oil.

  16. The design of two-stage-to-orbit vehicles

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Two separate student design groups developed conceptual designs for a two-stage-to-orbit vehicle, with each design group consisting of a carrier team and an orbiter team. A two-stage-to-orbit system is considered in the event that single-stage-to-orbit is deemed not feasible in the foreseeable future; the two-stage system would also be used as a complement to an already existing heavy lift vehicle. The design specifications given are to lift a 10,000-lb payload 27 ft long by 10 ft diameter, to low Earth orbit (300 n.m.) using an air breathing carrier configuration that will take off horizontally within 15,000 ft. The staging Mach number and altitude were to be determined by the design groups. One group designed a delta wing/body carrier with the orbiter nested within the fuselage of the carrier, and the other group produced a blended cranked-delta wing/body carrier with the orbiter in the more conventional piggyback configuration. Each carrier used liquid hydrogen-fueled turbofanramjet engines, with data provided by General Electric Aircraft Engine Group. While one orbiter used a full-scale Space Shuttle Main Engine (SSME), the other orbiter employed a half-scale SSME coupled with scramjet engines, with data again provided by General Electric. The two groups conceptual designs, along with the technical trade-offs, difficulties, and details that surfaced during the design process are presented.

  17. Two-Stage Machine Learning model for guideline development.

    PubMed

    Mani, S; Shankle, W R; Dick, M B; Pazzani, M J

    1999-05-01

    We present a Two-Stage Machine Learning (ML) model as a data mining method to develop practice guidelines and apply it to the problem of dementia staging. Dementia staging in clinical settings is at present complex and highly subjective because of the ambiguities and the complicated nature of existing guidelines. Our model abstracts the two-stage process used by physicians to arrive at the global Clinical Dementia Rating Scale (CDRS) score. The model incorporates learning intermediate concepts (CDRS category scores) in the first stage that then become the feature space for the second stage (global CDRS score). The sample consisted of 678 patients evaluated in the Alzheimer's Disease Research Center at the University of California, Irvine. The demographic variables, functional and cognitive test results used by physicians for the task of dementia severity staging were used as input to the machine learning algorithms. Decision tree learners and rule inducers (C4.5, Cart, C4.5 rules) were selected for our study as they give expressive models, and Naive Bayes was used as a baseline algorithm for comparison purposes. We first learned the six CDRS category scores (memory, orientation, judgement and problem solving, personal care, home and hobbies, and community affairs). These learned CDRS category scores were then used to learn the global CDRS scores. The Two-Stage ML model classified as well as or better than the published inter-rater agreements for both the category and global CDRS scoring by dementia experts. Furthermore, for the most critical distinction, normal versus very mildly impaired, the Two-Stage ML model was 28.1 and 6.6% more accurate than published performances by domain experts. Our study of the CDRS examined one of the largest, most diverse samples in the literature, suggesting that our findings are robust. The Two-Stage ML model also identified a CDRS category, Judgment and Problem Solving, which has low classification accuracy similar to published

  18. Two stage treatment of dairy effluent using immobilized Chlorella pyrenoidosa

    PubMed Central

    2013-01-01

    Background Dairy effluents contains high organic load and unscrupulous discharge of these effluents into aquatic bodies is a matter of serious concern besides deteriorating their water quality. Whilst physico-chemical treatment is the common mode of treatment, immobilized microalgae can be potentially employed to treat high organic content which offer numerous benefits along with waste water treatment. Methods A novel low cost two stage treatment was employed for the complete treatment of dairy effluent. The first stage consists of treating the diary effluent in a photobioreactor (1 L) using immobilized Chlorella pyrenoidosa while the second stage involves a two column sand bed filtration technique. Results Whilst NH4+-N was completely removed, a 98% removal of PO43--P was achieved within 96 h of two stage purification processes. The filtrate was tested for toxicity and no mortality was observed in the zebra fish which was used as a model at the end of 96 h bioassay. Moreover, a significant decrease in biological oxygen demand and chemical oxygen demand was achieved by this novel method. Also the biomass separated was tested as a biofertilizer to the rice seeds and a 30% increase in terms of length of root and shoot was observed after the addition of biomass to the rice plants. Conclusions We conclude that the two stage treatment of dairy effluent is highly effective in removal of BOD and COD besides nutrients like nitrates and phosphates. The treatment also helps in discharging treated waste water safely into the receiving water bodies since it is non toxic for aquatic life. Further, the algal biomass separated after first stage of treatment was highly capable of increasing the growth of rice plants because of nitrogen fixation ability of the green alga and offers a great potential as a biofertilizer. PMID:24355316

  19. Two-Stage Fan I: Aerodynamic and Mechanical Design

    NASA Technical Reports Server (NTRS)

    Messenger, H. E.; Kennedy, E. E.

    1972-01-01

    A two-stage, highly-loaded fan was designed to deliver an overall pressure ratio of 2.8 with an adiabatic efficiency of 83.9 percent. At the first rotor inlet, design flow per unit annulus area is 42 lbm/sec/sq ft (205 kg/sec/sq m), hub/tip ratio is 0.4 with a tip diameter of 31 inches (0.787 m), and design tip speed is 1450 ft/sec (441.96 m/sec). Other features include use of multiple-circular-arc airfoils, resettable stators, and split casings over the rotor tip sections for casing treatment tests.

  20. Two-stage band selection algorithm for hyperspectral imagery

    NASA Astrophysics Data System (ADS)

    Velez-Reyes, Miguel; Linares, Daphnia M.; Jimenez-Rodriguez, Luis O.

    2002-08-01

    This paper presents a two-stage band optimal band selection algorithm for hyperspectral imagery. The algorithm tries to compute the closest subset of bands to the principal components in the sense of having the smallest canonical correlation. The first stage of the algorithm computes and initial guess for the closest bands using matrix-factorization-based band subset selection. The second stage refines the subset of bands using a steepest ascent algorithm. Experimental results using AVIRIS imagery from the Cuprite Mining District are presented.

  1. Two-stage dilute acid prehydrolysis of biomass

    DOEpatents

    Grohmann, Karel; Torget, Robert W.

    1992-01-01

    A two-stage dilute acid prehydrolysis process on xylan containing hemicellulose in biomass is effected by: treating feedstock of hemicellulosic material comprising xylan that is slow hydrolyzable and xylan that is fast hydrolyzable under predetermined low temperature conditions with a dilute acid for a residence time sufficient to hydrolyze the fast hydrolyzable xylan to xylose; removing said xylose from said fast hydrolyzable xylan and leaving a residue; and treating said residue having a slow hydrolyzable xylan with a dilute acid under predetermined high temperature conditions for a residence time required to hydrolyze said slow hydrolyzable xylan to xylose.

  2. Two-stage biohumus production from inedible potato biomass.

    PubMed

    Manukovsky, N S; Kovalev, V S; Gribovskaya, I V

    2001-07-01

    The feasibility of a two-stage bioconversion of inedible potato biomass into biohumus by oyster mushroom followed by worms was tested. As a raw material for biohumus production the inedible potato biomass in certain properties ranked below wheat straw. The most feasible method to convert the potato wastes into biohumus was to mix them with wheat straw at the mass ratio of 1:3 and then treat with mushrooms followed by worms. This gave a good yield of mushrooms. The biohumus produced from the mixture was suitable for use as a plant growth medium.

  3. Two-Stage FEL (Free Electron Laser) Program.

    DTIC Science & Technology

    1983-08-25

    Sargent and Spitzer editors, Addison-Wesley (1982). 3. S. B . Segall, H. R. Hiddleston, H. Takeda, S. Von Laven, R. Holsinger, J. Ward , J. Richardson, and W...1983). 4. S. Von Laven, S. B . Segall, J. F. Ward , "A Low Loss Quasioptical Cavity for a Two-Stage Free Electron Laser", in the proceedings of this...CLASSIFICATION OF THIS PAGE Mhen Data Entered) _ _"_ _ _A READ IMMUCTIONS REPORT DOCUMENTATION PAGE B n oR ORM I. REPORT NUMER 2. GOVT ACCESSION NO

  4. Advanced two-stage compressor program design of inlet stage

    NASA Technical Reports Server (NTRS)

    Bryce, C. A.; Paine, C. J.; Mccutcheon, A. R. S.; Tu, R. K.; Perrone, G. L.

    1973-01-01

    The aerodynamic design of an inlet stage for a two-stage, 10/1 pressure ratio, 2 lb/sec flow rate compressor is discussed. Initially a performance comparison was conducted for an axial, mixed flow and centrifugal second stage. A modified mixed flow configuration with tandem rotors and tandem stators was selected for the inlet stage. The term conical flow compressor was coined to describe a particular type of mixed flow compressor configuration which utilizes axial flow type blading and an increase in radius to increase the work input potential. Design details of the conical flow compressor are described.

  5. Two-stage series array SQUID amplifier for space applications

    NASA Astrophysics Data System (ADS)

    Tuttle, J. G.; DiPirro, M. J.; Shirron, P. J.; Welty, R. P.; Radparvar, M.

    We present test results for a two-stage integrated SQUID amplifier which uses a series array of d.c. SQUIDS to amplify the signal from a single input SQUID. The device was developed by Welty and Martinis at NIST and recent versions have been manufactured by HYPRES, Inc. Shielding and filtering techniques were employed during the testing to minimize the external noise. Energy resolution of 300 h was demonstrated using a d.c. excitation at frequencies above 1 kHz, and better than 500 h resolution was typical down to 300 Hz.

  6. Method of operating a two-stage coal gasifier

    DOEpatents

    Tanca, Michael C.

    1982-01-01

    A method of operating an entrained flow coal gasifier (10) via a two-stage gasification process. A portion of the coal (18) to be gasified is combusted in a combustion zone (30) with near stoichiometric air to generate combustion products. The combustion products are conveyed from the combustion zone into a reduction zone (32) wherein additional coal is injected into the combustion products to react with the combustion products to form a combustible gas. The additional coal is injected into the reduction zone as a mixture (60) consisting of coal and steam, preferably with a coal-to-steam weight ratio of approximately ten to one.

  7. Conceptual design of a two stage to orbit spacecraft

    NASA Technical Reports Server (NTRS)

    Armiger, Scott C.; Kwarta, Jennifer S.; Horsley, Kevin B.; Snow, Glenn A.; Koe, Eric C.; Single, Thomas G.

    1993-01-01

    This project, undertaken through the Advanced Space Design Program, developed a 'Conceptual Design of a Two Stage To Orbit Spacecraft (TSTO).' The design developed utilizes a combination of air breathing and rocket propulsion systems and is fully reusable, with horizontal takeoff and landing capability. The orbiter is carried in an aerodynamically designed bay in the aft section of the booster vehicle to the staging altitude. This TSTO Spacecraft design meets the requirements of replacing the aging Space Shuttle system with a more easily maintained vehicle with more flexible mission capability.

  8. A two-stage exon recognition model based on synergetic neural network.

    PubMed

    Huang, Zhehuang; Chen, Yidong

    2014-01-01

    Exon recognition is a fundamental task in bioinformatics to identify the exons of DNA sequence. Currently, exon recognition algorithms based on digital signal processing techniques have been widely used. Unfortunately, these methods require many calculations, resulting in low recognition efficiency. In order to overcome this limitation, a two-stage exon recognition model is proposed and implemented in this paper. There are three main works. Firstly, we use synergetic neural network to rapidly determine initial exon intervals. Secondly, adaptive sliding window is used to accurately discriminate the final exon intervals. Finally, parameter optimization based on artificial fish swarm algorithm is used to determine different species thresholds and corresponding adjustment parameters of adaptive windows. Experimental results show that the proposed model has better performance for exon recognition and provides a practical solution and a promising future for other recognition tasks.

  9. Performance and stability of two-stage anaerobic digestion.

    PubMed

    Zahller, J D; Bucher, R H; Ferguson, J F; Stensel, H D

    2007-05-01

    The stability, capacity, and solids destruction efficiency of single versus two-stage anaerobic digestion was studied in bench-scale reactors using combined waste activated and primary sludge. Laboratory staged mesophilic digesters showed an improved volatile solids and volatile suspended solids destruction efficiency over a single-stage system (at the same total solids retention time [SRT]) of approximately 3.2 and 5.8 percentage points, respectively. To quantify stability and capacity, a new digester monitoring method was introduced that measured the digester maximum acetate utilization capacity, V(max,ac), and was used to investigate the potential for digester instability at different transient loadings. The ratio of the V(max,ac) value to the estimated acetate production rate for a given digester loading was termed the acetate capacity number (ACN). Values greater than 1.0 indicate excess acetate utilization capacity. The first stage of the laboratory two-stage mesophilic system (10-day SRT for each stage) had an ACN number of 1.3 compared with a value of 1.8 for the single-stage 20-day SRT digester. Thus, while a staged mesophilic system can improve solids destruction efficiency, it demonstrates a lower capacity for metabolizing highly variable loads.

  10. Two-stage anaerobic digestion enables heavy metal removal.

    PubMed

    Selling, Robert; Håkansson, Torbjörn; Björnsson, Lovisa

    2008-01-01

    To fully exploit the environmental benefits of the biogas process, the digestate should be recycled as biofertiliser to agriculture. This practice can however be jeopardized by the presence of unwanted compounds such as heavy metals in the digestate. By using two-stage digestion, where the first stage includes hydrolysis/acidification and liquefaction of the substrate, heavy metals can be transferred to the leachate. From the leachate, metals can then be removed by adsorption. In this study, up to 70% of the Ni, 40% of the Zn and 25% of the Cd present in maize was removed when the leachate from hydrolysis was circulated over a macroporous polyacrylamide column for 6 days. For Cu and Pb, the mobilization in the hydrolytic stage was lower which resulted in a low removal. A more efficient two-stage process with improved substrate hydrolysis would give lower pH and/or longer periods with low pH in the hydrolytic stage. This is likely to increase metal mobilisation, and would open up for an excellent opportunity of heavy metal removal.

  11. Two-stage mineralization of phenanthrene by estuarine enrichment cultures

    SciTech Connect

    Guerin, W.F.; Jones, G.E.

    1988-04-01

    The polycyclic aromatic hydrocarbon phenanthrene was mineralized in two stages by soil, estuarine water, and sediment microbial populations. At high concentrations, phenanthrene was degraded, with the concomitant production of biomass and accumulation of Folin-Ciocalteau-reactive aromatic intermediates. Subsequent consumption of these intermediates resulted in a secondary increase in biomass. Analysis of intermediates by high-performance liquid chromatography, thin-layer chromatography, and UV absorption spectrometry showed 1-hydroxy-2-naphthoic acid (1H2NA) to be the predominant product. A less pronounced two-stage mineralization pattern was also observed by monitoring /sup 14/CO/sub 2/ production from low concentrations (0.5 mg liter/sup -1/) of radiolabeled phenanthrene. Here, mineralization of /sup 14/C-labeled 1H2NA could explain the incremental /sup 14/CO/sub 2/ produced during the later part of the incubations. Accumulation of 1H2NA by isolates obtained from enrichments was dependent on the initial phenanthrene concentration. The production of metabolites during polycyclic aromatic hydrocarbon biodegradation is discussed with regard to its possible adaptive significance and its methodological implications.

  12. An optimal stratified Simon two-stage design.

    PubMed

    Parashar, Deepak; Bowden, Jack; Starr, Colin; Wernisch, Lorenz; Mander, Adrian

    2016-07-01

    In Phase II oncology trials, therapies are increasingly being evaluated for their effectiveness in specific populations of interest. Such targeted trials require designs that allow for stratification based on the participants' molecular characterisation. A targeted design proposed by Jones and Holmgren (JH) Jones CL, Holmgren E: 'An adaptive Simon two-stage design for phase 2 studies of targeted therapies', Contemporary Clinical Trials 28 (2007) 654-661.determines whether a drug only has activity in a disease sub-population or in the wider disease population. Their adaptive design uses results from a single interim analysis to decide whether to enrich the study population with a subgroup or not; it is based on two parallel Simon two-stage designs. We study the JH design in detail and extend it by providing a few alternative ways to control the familywise error rate, in the weak sense as well as the strong sense. We also introduce a novel optimal design by minimising the expected sample size. Our extended design contributes to the much needed framework for conducting Phase II trials in stratified medicine. © 2016 The Authors Pharmaceutical Statistics Published by John Wiley & Sons Ltd.

  13. Two-stage coal gasification and desulfurization apparatus

    DOEpatents

    Bissett, Larry A.; Strickland, Larry D.

    1991-01-01

    The present invention is directed to a system which effectively integrates a two-stage, fixed-bed coal gasification arrangement with hot fuel gas desulfurization of a first stream of fuel gas from a lower stage of the two-stage gasifier and the removal of sulfur from the sulfur sorbent regeneration gas utilized in the fuel-gas desulfurization process by burning a second stream of fuel gas from the upper stage of the gasifier in a combustion device in the presence of calcium-containing material. The second stream of fuel gas is taken from above the fixed bed in the coal gasifier and is laden with ammonia, tar and sulfur values. This second stream of fuel gas is burned in the presence of excess air to provide heat energy sufficient to effect a calcium-sulfur compound forming reaction between the calcium-containing material and sulfur values carried by the regeneration gas and the second stream of fuel gas. Any ammonia values present in the fuel gas are decomposed during the combustion of the fuel gas in the combustion chamber. The substantially sulfur-free products of combustion may then be combined with the desulfurized fuel gas for providing a combustible fluid utilized for driving a prime mover.

  14. Runway Operations Planning: A Two-Stage Heuristic Algorithm

    NASA Technical Reports Server (NTRS)

    Anagnostakis, Ioannis; Clarke, John-Paul

    2003-01-01

    The airport runway is a scarce resource that must be shared by different runway operations (arrivals, departures and runway crossings). Given the possible sequences of runway events, careful Runway Operations Planning (ROP) is required if runway utilization is to be maximized. From the perspective of departures, ROP solutions are aircraft departure schedules developed by optimally allocating runway time for departures given the time required for arrivals and crossings. In addition to the obvious objective of maximizing throughput, other objectives, such as guaranteeing fairness and minimizing environmental impact, can also be incorporated into the ROP solution subject to constraints introduced by Air Traffic Control (ATC) procedures. This paper introduces a two stage heuristic algorithm for solving the Runway Operations Planning (ROP) problem. In the first stage, sequences of departure class slots and runway crossings slots are generated and ranked based on departure runway throughput under stochastic conditions. In the second stage, the departure class slots are populated with specific flights from the pool of available aircraft, by solving an integer program with a Branch & Bound algorithm implementation. Preliminary results from this implementation of the two-stage algorithm on real-world traffic data are presented.

  15. Neuronal substrates characterizing two stages in visual object recognition.

    PubMed

    Taminato, Tomoya; Miura, Naoki; Sugiura, Motoaki; Kawashima, Ryuta

    2014-12-01

    Visual object recognition is classically believed to involve two stages: a perception stage in which perceptual information is integrated, and a memory stage in which perceptual information is matched with an object's representation. The transition from the perception to the memory stage can be slowed to allow for neuroanatomical segregation using a degraded visual stimuli (DVS) task in which images are first presented at low spatial resolution and then gradually sharpened. In this functional magnetic resonance imaging study, we characterized these two stages using a DVS task based on the classic model. To separate periods that are assumed to dominate the perception, memory, and post-recognition stages, subjects responded once when they could guess the identity of the object in the image and a second time when they were certain of the identity. Activation of the right medial occipitotemporal region and the posterior part of the rostral medial frontal cortex was found to be characteristic of the perception and memory stages, respectively. Although the known role of the former region in perceptual integration was consistent with the classic model, a likely role of the latter region in monitoring for confirmation of recognition suggests the advantage of recently proposed interactive models.

  16. Modeling of a Sequential Two-Stage Combustor

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.; Liu, N.-S.; Gallagher, J. R.; Ryder, R. C.; Brankovic, A.; Hendricks, J. A.

    2005-01-01

    A sequential two-stage, natural gas fueled power generation combustion system is modeled to examine the fundamental aerodynamic and combustion characteristics of the system. The modeling methodology includes CAD-based geometry definition, and combustion computational fluid dynamics analysis. Graphical analysis is used to examine the complex vortical patterns in each component, identifying sources of pressure loss. The simulations demonstrate the importance of including the rotating high-pressure turbine blades in the computation, as this results in direct computation of combustion within the first turbine stage, and accurate simulation of the flow in the second combustion stage. The direct computation of hot-streaks through the rotating high-pressure turbine stage leads to improved understanding of the aerodynamic relationships between the primary and secondary combustors and the turbomachinery.

  17. Two-stage polling system with multiple servers

    NASA Astrophysics Data System (ADS)

    Lai, Wai Sum; Houck, David J.; Fuhrmann, Steven W.

    1997-10-01

    We investigate the impact of scheduling policies on the tail distribution of sojourn times experienced by various unevenly-loaded queues in a two-stage polling system served by a symmetric multiprocessor system running under a Unix- like operating system. The queues are statically divided into groups, with each group being managed by a process. A process can run on any of the available processors. Service to a customer is thus scheduled first at the process level and then at the queue level. Assuming that all customers have the same service requirement, and for Poisson arrivals and exponentially distributed service times and setup times, it is shown by simulation that the earliest-customer policy outperforms both 1-limited and exhaustive policies in the sense of providing equitable service to the queues.

  18. Investigation on Two-Stage 300 HZ Pulse Tube Cryocooler

    NASA Astrophysics Data System (ADS)

    Cai, H. K.; Yang, L. W.; Hong, G. T.; Luo, E. C.; Zhou, Y.

    2010-04-01

    In the past few years, ultra-high frequency pulse tube cryocoolers are becoming a research hotspot for their portability and compactness in aerospace and aviation applications. For preliminary research, a two-stage pulse tube cryocooler working at 300 Hz driven by a thermoacoustic engine is established to investigate the problems due to ultra high frequency, and several results have been derived in our early reports. In order to study the effect of thermal penetration depth, this paper presents the cooler adopting copper mesh as the regenerator, and comparison with stainless steel mesh is given. In addition, the influence of inertance tube on the lowest possible cooler temperature is also tested. Finally, we discuss the improvement for getting a lower temperature.

  19. Nonlinear two-stage model for color discrimination.

    PubMed

    Inamura, Taisuke; Shioiri, Satoshi; Tsujimura, Sei-ichi; Yaguchi, Hirohisa

    2011-04-01

    We modified a two-stage model for color discrimination proposed in a previous study [Color Res. Appl.25, 105 (2000)]; in order to extend the model to wider conditions, we considered the conditions with luminance modulations in addition to color modulations. Using the modified model, we successfully predicted color discrimination data with test color changes along both the chromatic and luminance axes under a variety of background colors. Both qualitative and quantitative assessments in modeling showed that nonlinearity is required in both the cone and the cone-opponent stages to interpret adaptation effects of both color and luminance on color discrimination. This fact suggests that the nonlinear properties at each stage have different roles in color perception.

  20. Two-stage designs for cross-over bioequivalence trials.

    PubMed

    Kieser, Meinhard; Rauch, Geraldine

    2015-07-20

    The topic of applying two-stage designs in the field of bioequivalence studies has recently gained attention in the literature and in regulatory guidelines. While there exists some methodological research on the application of group sequential designs in bioequivalence studies, implementation of adaptive approaches has focused up to now on superiority and non-inferiority trials. Especially, no comparison of the features and performance characteristics of these designs has been performed, and therefore, the question of which design to employ in this setting remains open. In this paper, we discuss and compare 'classical' group sequential designs and three types of adaptive designs that offer the option of mid-course sample size recalculation. A comprehensive simulation study demonstrates that group sequential designs can be identified, which show power characteristics that are similar to those of the adaptive designs but require a lower average sample size. The methods are illustrated with a real bioequivalence study example.

  1. Two-stage radio-frequency interferometer sensors

    PubMed Central

    Osterberg, Jeffrey; Wang, Pingshan

    2015-01-01

    We show that simple radio-frequency (RF) interferometers can have slow-wave positive group delay (PGD) or negative group delay (NGD), as well as superluminal propagation (SP) regions, due to a destructive interference process. These properties are easily tunable, which makes RF interferometers unique among systems that have NGD and SP regimes. A two-stage interferometer arrangement, which includes a first stage interferometer in the material-under-test path of a second stage, has significantly improved sensitivity in comparison with a one-stage reference interferometer. With a power divider based first stage and at its maximum NGD frequency, the frequency sensitivity improvement is as high as 7 times. With a quadrature based first stage, the sensitivity is increased by as much as 20 times. Sensitivity improvements are also observed at PGD and SP frequency regions. PMID:26576062

  2. The role of two-stage repair in modern hypospadiology

    PubMed Central

    Bracka, Aivar

    2008-01-01

    Hypospadias surgery continues to evolve. The enthusiasm for flap-based urethroplasty is waning and instead there is an increasing preference for urethroplasty that uses either the urethral plate alone or in combination with grafts. From the vast armamentarium of hypospadias repairs that are still in use, the author suggests a simple protocol of just three closely related procedures with which we can now repair almost all hypospadias. The tubularised incised plate (TIP) repair and the ‘Snodgraft’ modification of the TIP principle are simple and effective one-stage solutions when partial circumference urethroplasty is required. Conversely, the Bracka two-stage graft repair remains an ideal and versatile solution when a full circumference urethroplasty is required. It is particularly appropriate for severe primary hypospadias associated with a poor plate and marked chordee and also to replace a scarred, hairy or balanitis xerotica obliterans diseased urethra in re-operative salvage hypospadias. PMID:19468400

  3. Two-stage observer based offset-free MPC.

    PubMed

    Mohammadkhani, MohammadAli; Bayat, Farhad; Jalali, Ali Akbar

    2015-07-01

    This paper addresses design of model predictive control (MPC) for dynamic systems in the presence of disturbances. For the systems with disturbances, it is common to use observers to estimate states and disturbances, allowing control algorithm to reject disturbances. In this paper, we demonstrate how one can extend model predictive control for systems with disturbances by applying full state and disturbance observer. To this aim, a two-stage approach is proposed where the observer design procedure is completely decoupled from the MPC problem, known as the separation principle. We focus on the decoupling principal and it is shown that the observer can be designed independently via a norm minimization problem to reduce effects of disturbances and model mismatch. On the other hand, the MPC law is obtained using the multi-parametric quadratic programming approach where the parameters are the components of the state vector.

  4. Two-stage decision approach to material accounting

    SciTech Connect

    Opelka, J.H.; Sutton, W.B.

    1982-01-01

    The validity of the alarm threshold 4sigma has been checked for hypothetical large and small facilities using a two-stage decision model in which the diverter's strategic variable is the quantity diverted, and the defender's strategic variables are the alarm threshold and the effectiveness of the physical security and material control systems in the possible presence of a diverter. For large facilities, the material accounting system inherently appears not to be a particularly useful system for the deterrence of diversions, and essentially no improvement can be made by lowering the alarm threshold below 4sigma. For small facilities, reduction of the threshold to 2sigma or 3sigma is a cost effective change for the accounting system, but is probably less cost effective than making improvements in the material control and physical security systems.

  5. Two-stage radio-frequency interferometer sensors.

    PubMed

    Osterberg, Jeffrey; Wang, Pingshan

    2015-10-26

    We show that simple radio-frequency (RF) interferometers can have slow-wave positive group delay (PGD) or negative group delay (NGD), as well as superluminal propagation (SP) regions, due to a destructive interference process. These properties are easily tunable, which makes RF interferometers unique among systems that have NGD and SP regimes. A two-stage interferometer arrangement, which includes a first stage interferometer in the material-under-test path of a second stage, has significantly improved sensitivity in comparison with a one-stage reference interferometer. With a power divider based first stage and at its maximum NGD frequency, the frequency sensitivity improvement is as high as 7 times. With a quadrature based first stage, the sensitivity is increased by as much as 20 times. Sensitivity improvements are also observed at PGD and SP frequency regions.

  6. Two Stage Assessment of Thermal Hazard in An Underground Mine

    NASA Astrophysics Data System (ADS)

    Drenda, Jan; Sułkowski, Józef; Pach, Grzegorz; Różański, Zenon; Wrona, Paweł

    2016-06-01

    The results of research into the application of selected thermal indices of men's work and climate indices in a two stage assessment of climatic work conditions in underground mines have been presented in this article. The difference between these two kinds of indices was pointed out during the project entitled "The recruiting requirements for miners working in hot underground mine environments". The project was coordinated by The Institute of Mining Technologies at Silesian University of Technology. It was a part of a Polish strategic project: "Improvement of safety in mines" being financed by the National Centre of Research and Development. Climate indices are based only on physical parameters of air and their measurements. Thermal indices include additional factors which are strictly connected with work, e.g. thermal resistance of clothing, kind of work etc. Special emphasis has been put on the following indices - substitute Silesian temperature (TS) which is considered as the climatic index, and the thermal discomfort index (δ) which belongs to the thermal indices group. The possibility of the two stage application of these indices has been taken into consideration (preliminary and detailed estimation). Based on the examples it was proved that by the application of thermal hazard (detailed estimation) it is possible to avoid the use of additional technical solutions which would be necessary to reduce thermal hazard in particular work places according to the climate index. The threshold limit value for TS has been set, based on these results. It was shown that below TS = 24°C it is not necessary to perform detailed estimation.

  7. Runway Operations Planning: A Two-Stage Solution Methodology

    NASA Technical Reports Server (NTRS)

    Anagnostakis, Ioannis; Clarke, John-Paul

    2003-01-01

    The airport runway is a scarce resource that must be shared by different runway operations (arrivals, departures and runway crossings). Given the possible sequences of runway events, careful Runway Operations Planning (ROP) is required if runway utilization is to be maximized. Thus, Runway Operations Planning (ROP) is a critical component of airport operations planning in general and surface operations planning in particular. From the perspective of departures, ROP solutions are aircraft departure schedules developed by optimally allocating runway time for departures given the time required for arrivals and crossings. In addition to the obvious objective of maximizing throughput, other objectives, such as guaranteeing fairness and minimizing environmental impact, may be incorporated into the ROP solution subject to constraints introduced by Air Traffic Control (ATC) procedures. Generating optimal runway operations plans was approached in with a 'one-stage' optimization routine that considered all the desired objectives and constraints, and the characteristics of each aircraft (weight class, destination, Air Traffic Control (ATC) constraints) at the same time. Since, however, at any given point in time, there is less uncertainty in the predicted demand for departure resources in terms of weight class than in terms of specific aircraft, the ROP problem can be parsed into two stages. In the context of the Departure Planner (OP) research project, this paper introduces Runway Operations Planning (ROP) as part of the wider Surface Operations Optimization (SOO) and describes a proposed 'two stage' heuristic algorithm for solving the Runway Operations Planning (ROP) problem. Focus is specifically given on including runway crossings in the planning process of runway operations. In the first stage, sequences of departure class slots and runwy crossings slots are generated and ranked based on departure runway throughput under stochastic conditions. In the second stage, the

  8. An inexact mixed risk-aversion two-stage stochastic programming model for water resources management under uncertainty.

    PubMed

    Li, W; Wang, B; Xie, Y L; Huang, G H; Liu, L

    2015-02-01

    Uncertainties exist in the water resources system, while traditional two-stage stochastic programming is risk-neutral and compares the random variables (e.g., total benefit) to identify the best decisions. To deal with the risk issues, a risk-aversion inexact two-stage stochastic programming model is developed for water resources management under uncertainty. The model was a hybrid methodology of interval-parameter programming, conditional value-at-risk measure, and a general two-stage stochastic programming framework. The method extends on the traditional two-stage stochastic programming method by enabling uncertainties presented as probability density functions and discrete intervals to be effectively incorporated within the optimization framework. It could not only provide information on the benefits of the allocation plan to the decision makers but also measure the extreme expected loss on the second-stage penalty cost. The developed model was applied to a hypothetical case of water resources management. Results showed that that could help managers generate feasible and balanced risk-aversion allocation plans, and analyze the trade-offs between system stability and economy.

  9. Effect of Silica Fume on two-stage Concrete Strength

    NASA Astrophysics Data System (ADS)

    Abdelgader, H. S.; El-Baden, A. S.

    2015-11-01

    Two-stage concrete (TSC) is an innovative concrete that does not require vibration for placing and compaction. TSC is a simple concept; it is made using the same basic constituents as traditional concrete: cement, coarse aggregate, sand and water as well as mineral and chemical admixtures. As its name suggests, it is produced through a two-stage process. Firstly washed coarse aggregate is placed into the formwork in-situ. Later a specifically designed self compacting grout is introduced into the form from the lowest point under gravity pressure to fill the voids, cementing the aggregate into a monolith. The hardened concrete is dense, homogeneous and has in general improved engineering properties and durability. This paper presents the results from a research work attempt to study the effect of silica fume (SF) and superplasticizers admixtures (SP) on compressive and tensile strength of TSC using various combinations of water to cement ratio (w/c) and cement to sand ratio (c/s). Thirty six concrete mixes with different grout constituents were tested. From each mix twenty four standard cylinder samples of size (150mm×300mm) of concrete containing crushed aggregate were produced. The tested samples were made from combinations of w/c equal to: 0.45, 0.55 and 0.85, and three c/s of values: 0.5, 1 and 1.5. Silica fume was added at a dosage of 6% of weight of cement, while superplasticizer was added at a dosage of 2% of cement weight. Results indicated that both tensile and compressive strength of TSC can be statistically derived as a function of w/c and c/s with good correlation coefficients. The basic principle of traditional concrete, which says that an increase in water/cement ratio will lead to a reduction in compressive strength, was shown to hold true for TSC specimens tested. Using a combination of both silica fume and superplasticisers caused a significant increase in strength relative to control mixes.

  10. XPG Gene Polymorphisms Contribute to Colorectal Cancer Susceptibility: A Two-Stage Case-Control Study

    PubMed Central

    Hua, Rui-Xi; Zhuo, Zhen-Jian; Zhu, Jinhong; Zhang, Shao-Dan; Xue, Wen-Qiong; Zhang, Jiang-Bo; Xu, Hong-Mei; Li, Xi-Zhao; Zhang, Pei-Fen; He, Jing; Jia, Wei-Hua

    2016-01-01

    Previous studies have reported that xeroderma pigmentosum group G (XPG) gene polymorphisms may modulate colorectal cancer (CRC) susceptibility. In this study, we performed a two-stage case-control study to comprehensively investigate the associations of five polymorphisms in the XPG gene with CRC risk in 1,901 cases and 1,976 controls from Southern China, including rs2094258 C>T, rs751402 C>T, rs2296147 T>C, rs1047768 T>C and rs873601 G>A. After combining data from two stages, we found that three of the studied polymorphisms (rs2094258 C>T, rs751402 C>T, and rs873601 G>A) were significantly associated with CRC susceptibility. After adjustment for age and gender, multivariate logistic regression analysis indicated that carriers of the rs2094258 T alleles had an increased CRC risk [CT vs. CC: adjusted odds ratio (OR)=1.17, 95% confidence interval (CI)=1.01-1.36; TT vs. CC: adjusted OR=1.49, 95% CI=1.18-1.89; TT vs. CT/CC: adjusted OR=1.38, 95% CI=1.10-1.72]. Likely, rs873601 A allele also conferred increased CRC susceptibility. In contrast, a protective association was identified between rs751402 C>T polymorphism and the risk of CRC. In summary, our results indicated that these three polymorphisms were found to associate with CRC susceptibility in a Southern Chinese population. PMID:27698911

  11. Two-Stage, 90-GHz, Low-Noise Amplifier

    NASA Technical Reports Server (NTRS)

    Samoska, Lorene A.; Gaier, Todd C.; Xenos, Stephanie; Soria, Mary M.; Kangaslahti, Pekka P.; Cleary, Kieran A.; Ferreira, Linda; Lai, Richard; Mei, Xiaobing

    2010-01-01

    A device has been developed for coherent detection of the polarization of the cosmic microwave background (CMB). A two-stage amplifier has been designed that covers 75-110 GHz. The device uses the emerging 35-nm InP HEMT technology recently developed at Northrop Grumman Corporation primarily for use at higher frequencies. The amplifier has more than 18 dB gain and less than 35 K noise figure across the band. These devices have noise less than 30 K at 100 GHz. The development started with design activities at JPL, as well as characterization of multichip modules using existing InP. Following processing, a test campaign was carried out using single-chip modules at 100 GHz. Successful development of the chips will lead to development of multichip modules, with simultaneous Q and U Stokes parameter detection. This MMIC (monolithic microwave integrated circuit) amplifier takes advantage of performance improvements intended for higher frequencies, but in this innovation are applied at 90 GHz. The large amount of available gain ultimately leads to lower possible noise performance at 90 GHz.

  12. Gas loading system for LANL two-stage gas guns

    NASA Astrophysics Data System (ADS)

    Gibson, Lee; Bartram, Brian; Dattelbaum, Dana; Lang, John; Morris, John

    2015-06-01

    A novel gas loading system was designed for the specific application of remotely loading high purity gases into targets for gas-gun driven plate impact experiments. The high purity gases are loaded into well-defined target configurations to obtain Hugoniot states in the gas phase at greater than ambient pressures. The small volume of the gas samples is challenging, as slight changing in the ambient temperature result in measurable pressure changes. Therefore, the ability to load a gas gun target and continually monitor the sample pressure prior to firing provides the most stable and reliable target fielding approach. We present the design and evaluation of a gas loading system built for the LANL 50 mm bore two-stage light gas gun. Targets for the gun are made of 6061 Al or OFHC Cu, and assembled to form a gas containment cell with a volume of approximately 1.38 cc. The compatibility of materials was a major consideration in the design of the system, particularly for its use with corrosive gases. Piping and valves are stainless steel with wetted seals made from Kalrez and Teflon. Preliminary testing was completed to ensure proper flow rate and that the proper safety controls were in place. The system has been used to successfully load Ar, Kr, Xe, and anhydrous ammonia with purities of up to 99.999 percent. The design of the system, and example data from the plate impact experiments will be shown. LA-UR-15-20521

  13. Object Proposal Generation Using Two-Stage Cascade SVMs.

    PubMed

    Zhang, Ziming; Torr, Philip H S

    2016-01-01

    Object proposal algorithms have shown great promise as a first step for object recognition and detection. Good object proposal generation algorithms require high object detection recall rate as well as low computational cost, because generating object proposals is usually utilized as a preprocessing step. The problem of how to accelerate the object proposal generation and evaluation process without decreasing recall is thus of great interest. In this paper, we propose a new object proposal generation method using two-stage cascade support vector machines (SVMs), where in the first stage linear filters are learned for predefined quantized scales/aspect-ratios independently, and in the second stage a global linear classifier is learned across all the quantized scales/aspect-ratios for calibration, so that all the windows from the first stage can be compared properly. The windows with highest scores from the second stage are kept as inputs to our new efficient proposal calibration algorithm to improve their localization quality significantly, resulting in our final object proposals. We explain our scale/aspect-ratio quantization scheme, and investigate the effects of combinations of l1 and l2 regularizers in cascade SVMs with/without ranking constraints in learning. Comprehensive experiments on VOC2007 dataset are conducted, and our method is comparable with the current state-of-the-art methods with much better computational efficiency.

  14. Baseplate for two-stage cranial mounting of BMI connectors

    NASA Astrophysics Data System (ADS)

    McMorland, Angus J. C.; Velliste, Meel

    2013-06-01

    Objective. Intracortical electrode arrays provide the best spatial and temporal resolution signals for brain-machine interfaces. Wireless technologies are being developed to handle this information capacity, but currently the only means to deliver neural information from the implant to a signal processing unit is by a physical connection starting at a skull-mounted connector. The failure rate of the attachment of these connectors is significant. In this study we report an improvement to the traditional connectors. Approach. We have designed and applied an intermediary mounting plate that incorporates several features that provide better, more stable fixation to the skull: (1) wide legs allowing distribution of loading forces and distancing the intracranial screws from the skin interface, (2) a thin shelf to allow early osseointegration, (3) a concave interior to accommodate the curvature of the cranium, and (4) two-stage fixation process providing time for osseointegration prior to the application of loading forces from the connector. Main results. Six baseplates, over four design iterations, have now been tested in three non-human primates. The baseplates are associated with a substantially lower attachment failure rate. Significance. Our baseplate design improves on the current skull-mounted connectors, leading to better outcomes for subjects and fewer catastrophic failure events that can terminate resource intensive intracortical recording experiments.

  15. A two-stage approach to automatic face alignment

    NASA Astrophysics Data System (ADS)

    Wang, Tong; Ai, Haizhou; Huang, Gaofeng

    2003-09-01

    Face alignment is very important in face recognition, modeling and synthesis. Many approaches have been developed for this purpose, such as ASM, AAM, DAM and TC-ASM. After a brief review of all those methods, it is pointed out that these approaches all require a manual initialization to the positions of the landmarks and are very sensitive to it, and despite of all those devoted works the outline of a human face remains a difficult task to be localized precisely. In this paper, a two-stage method to achieve frontal face alignment fully automatically is introduced. The first stage is landmarks' initialization called coarse face alignment. In this stage, after a face is detected by an Adaboost cascade face detector, we use Simple Direct Appearance Model (SDAM) to locate a few key points of human face from the texture according which all the initial landmarks are setup as the coarse alignment. The second stage is fine face alignment that uses a variant of AAM method in which shape variation is predicted from texture reconstruction error together with an embedded ASM refinement for the outline landmarks of the face to achieve the fine alignment. Experiments on a face database of 500 people show that this method is very effective for practical applications.

  16. Laparoscopic management of a two staged gall bladder torsion

    PubMed Central

    Sunder, Yadav Kamal; Akhilesh, Sali Priyanka; Raman, Garg; Deborshi, Sharma; Shantilal, Mehta Hitesh

    2015-01-01

    Gall bladder torsion (GBT) is a relatively uncommon entity and rarely diagnosed preoperatively. A constant factor in all occurrences of GBT is a freely mobile gall bladder due to congenital or acquired anomalies. GBT is commonly observed in elderly white females. We report a 77-year-old, Caucasian lady who was originally diagnosed as gall bladder perforation but was eventually found with a two staged torsion of the gall bladder with twisting of the Riedel’s lobe (part of tongue like projection of liver segment 4A). This together, has not been reported in literature, to the best of our knowledge. We performed laparoscopic cholecystectomy and she had an uneventful post-operative period. GBT may create a diagnostic dilemma in the context of acute cholecystitis. Timely diagnosis and intervention is necessary, with extra care while operating as the anatomy is generally distorted. The fundus first approach can be useful due to altered anatomy in the region of Calot’s triangle. Laparoscopic cholecystectomy has the benefit of early recovery. PMID:26730287

  17. A two-stage model of fracture of rocks

    USGS Publications Warehouse

    Kuksenko, V.; Tomilin, N.; Damaskinskaya, E.; Lockner, D.

    1996-01-01

    In this paper we propose a two-stage model of rock fracture. In the first stage, cracks or local regions of failure are uncorrelated occur randomly throughout the rock in response to loading of pre-existing flaws. As damage accumulates in the rock, there is a gradual increase in the probability that large clusters of closely spaced cracks or local failure sites will develop. Based on statistical arguments, a critical density of damage will occur where clusters of flaws become large enough to lead to larger-scale failure of the rock (stage two). While crack interaction and cooperative failure is expected to occur within clusters of closely spaced cracks, the initial development of clusters is predicted based on the random variation in pre-existing Saw populations. Thus the onset of the unstable second stage in the model can be computed from the generation of random, uncorrelated damage. The proposed model incorporates notions of the kinetic (and therefore time-dependent) nature of the strength of solids as well as the discrete hierarchic structure of rocks and the flaw populations that lead to damage accumulation. The advantage offered by this model is that its salient features are valid for fracture processes occurring over a wide range of scales including earthquake processes. A notion of the rank of fracture (fracture size) is introduced, and criteria are presented for both fracture nucleation and the transition of the failure process from one scale to another.

  18. Optimal two-stage enrichment design correcting for biomarker misclassification.

    PubMed

    Zang, Yong; Guo, Beibei

    2015-11-26

    The enrichment design is an important clinical trial design to detect the treatment effect of the molecularly targeted agent (MTA) in personalized medicine. Under this design, patients are stratified into marker-positive and marker-negative subgroups based on their biomarker statuses and only the marker-positive patients are enrolled into the trial and randomized to receive either the MTA or a standard treatment. As the biomarker plays a key role in determining the enrollment of the trial, a misclassification of the biomarker can induce substantial bias, undermine the integrity of the trial, and seriously affect the treatment evaluation. In this paper, we propose a two-stage optimal enrichment design that utilizes the surrogate marker to correct for the biomarker misclassification. The proposed design is optimal in the sense that it maximizes the probability of correctly classifying each patient's biomarker status based on the surrogate marker information. In addition, after analytically deriving the bias caused by the biomarker misclassification, we develop a likelihood ratio test based on the EM algorithm to correct for such bias. We conduct comprehensive simulation studies to investigate the operating characteristics of the optimal design and the results confirm the desirable performance of the proposed design.

  19. Residential oil burners with low input and two stages firing

    SciTech Connect

    Butcher, T.; Krajewski, R.; Leigh, R.

    1997-12-31

    The residential oil burner market is currently dominated by the pressure-atomized, retention head burner. At low firing rates pressure atomizing nozzles suffer rapid fouling of the small internal passages, leading to bad spray patterns and poor combustion performance. To overcome the low input limitations of conventional burners, a low pressure air-atomized burner has been developed watch can operate at fining rates as low as 0.25 gallons of oil per hour (10 kW). In addition, the burner can be operated in a high/low fining rate mode. Field tests with this burner have been conducted at a fixed input rate of 0.35 gph (14 kW) with a side-wall vented boiler/water storage tank combination. At the test home, instrumentation was installed to measure fuel and energy flows and record trends in system temperatures. Laboratory efficiency testing with water heaters and boilers has been completed using standard single purpose and combined appliance test procedures. The tests quantify benefits due to low firing rates and other burner features. A two stage oil burner gains a strong advantage in rated efficiency while maintaining capacity for high domestic hot water and space heating loads.

  20. Apparatus and method for two-stage oxidation of wastes

    DOEpatents

    Fleischman, Scott D.

    1995-01-01

    An apparatus and method for oxidizing wastes in a two-stage process. The apparatus includes an oxidation device, a gas-liquid contacting column and an electrocell. In the first stage of the process, wastes are heated in the presence of air to partially oxidize the wastes. The heated wastes produce an off-gas stream containing oxidizable materials. In the second stage, the off-gas stream is cooled and flowed through the contacting column, where the off-gas stream is contacted with an aqueous acid stream containing an oxidizing agent having at least two positive valence states. At least a portion of the oxidizable materials are transferred to the acid stream and destroyed by the oxidizing agent. During oxidation, the valence of the oxidizing agent is decreased from its higher state to its lower state. The acid stream is flowed to the electrocell, where an electric current is applied to the stream to restore the oxidizing agent to its higher valence state. The regenerated acid stream is recycled to the contacting column.

  1. A two-stage DEA approach for environmental efficiency measurement.

    PubMed

    Song, Malin; Wang, Shuhong; Liu, Wei

    2014-05-01

    The slacks-based measure (SBM) model based on the constant returns to scale has achieved some good results in addressing the undesirable outputs, such as waste water and water gas, in measuring environmental efficiency. However, the traditional SBM model cannot deal with the scenario in which desirable outputs are constant. Based on the axiomatic theory of productivity, this paper carries out a systematic research on the SBM model considering undesirable outputs, and further expands the SBM model from the perspective of network analysis. The new model can not only perform efficiency evaluation considering undesirable outputs, but also calculate desirable and undesirable outputs separately. The latter advantage successfully solves the "dependence" problem of outputs, that is, we can not increase the desirable outputs without producing any undesirable outputs. The following illustration shows that the efficiency values obtained by two-stage approach are smaller than those obtained by the traditional SBM model. Our approach provides a more profound analysis on how to improve environmental efficiency of the decision making units.

  2. A continuous two stage solar coal gasification system

    NASA Astrophysics Data System (ADS)

    Mathur, V. K.; Breault, R. W.; Lakshmanan, S.; Manasse, F. K.; Venkataramanan, V.

    The characteristics of a two-stage fluidized-bed hybrid coal gasification system to produce syngas from coal, lignite, and peat are described. Devolatilization heat of 823 K is supplied by recirculating gas heated by a solar receiver/coal heater. A second-stage gasifier maintained at 1227 K serves to crack remaining tar and light oil to yield a product free from tar and other condensables, and sulfur can be removed by hot clean-up processes. CO is minimized because the coal is not burned with oxygen, and the product gas contains 50% H2. Bench scale reactors consist of a stage I unit 0.1 m in diam which is fed coal 200 microns in size. A stage II reactor has an inner diam of 0.36 m and serves to gasify the char from stage I. A solar power source of 10 kWt is required for the bench model, and will be obtained from a central receiver with quartz or heat pipe configurations for heat transfer.

  3. New LANL gas driven two-stage gun

    SciTech Connect

    Martinez, A.R.; Sheffied, S.A.; Whitehead, M.C.; Olivas, H.D.; Dick, J.J. )

    1994-07-10

    A new compressed-helium driven two-stage light gas gun has been installed at LANL to study shock initiated reaction in insensitive high explosives. The gun (based on a design at Ernst Mach Institute) has a 100-mm diameter by 7.6 long pump tube and a 50-mm diameter by 7.6-m long launch tube. The gas breech, capable of pressures up to 15,000 psi, has a volume of 42.5 liters and can be used in either a wrap-around or double-diaphragm mode. This breech was designed so we could use helium rather than powder combustion gases to drive the pump piston, eliminating the safety and cleanup problems assoicated with gun powder. Large hydraulic clamps (pressurized to 10,000 psi) are used to clamp the breech to the pump tube, the pump tube to the transition section, and the transition section to the launch tube. The target chamber was designed to allow the necessary room to do multiple magnetic gauging experiments. Gun control is accomplished using a MAC computer and LabVIEW control software. [copyright]American Institute of Physics

  4. New LANL gas driven two-stage gun

    NASA Astrophysics Data System (ADS)

    Martinez, A. R.; Sheffied, S. A.; Whitehead, M. C.; Olivas, H. D.; Dick, J. J.

    1994-07-01

    A new compressed-helium driven two-stage light gas gun has been installed at LANL to study shock initiated reaction in insensitive high explosives. The gun (based on a design at Ernst Mach Institute) has a 100-mm diameter by 7.6 long pump tube and a 50-mm diameter by 7.6-m long launch tube. The gas breech, capable of pressures up to 15,000 psi, has a volume of 42.5 liters and can be used in either a wrap-around or double-diaphragm mode. This breech was designed so we could use helium rather than powder combustion gases to drive the pump piston, eliminating the safety and cleanup problems assoicated with gun powder. Large hydraulic clamps (pressurized to 10,000 psi) are used to clamp the breech to the pump tube, the pump tube to the transition section, and the transition section to the launch tube. The target chamber was designed to allow the necessary room to do multiple magnetic gauging experiments. Gun control is accomplished using a MAC computer and LabVIEW control software.

  5. New LANL gas-driven two-stage gun

    SciTech Connect

    Martinez, A.R.; Sheffield, S.A.; Whitehead, M.C.; Olivas, H.D.; Dick, J.J.

    1993-08-01

    A new compressed-helium driven two-stage light gas gun has been installed at LANL to study shock initiated reaction in insensitive high explosives. The gun (based on a design at Ernst Mach Institute) has a 100-mm diameter by 7.6 long pump tube and a 50-mm diameter by 7.6-m long launch tube. The gas breech, capable of pressures up to 15.000 psi, has a volume of 42.5 liters and can be used in either a wrap-around or double-diaphragm mode. This breech was designed so we could use helium rather than powder combustion gases to drive the pump piston, eliminating the safety and cleanup problems associated with gun powder. Large hydraulic clamps (pressurized to 10,000 psi) are used to clamp the breech to the pump tube, the pump tube to the transition section, and the transition section to the launch tube. The target chamber was designed to allow the necessary room to do multiple magnetic gauging experiments. Gun control is accomplished using a MAC computer and LabVIEW control software.

  6. Contactless two-stage solar concentrators for tubular absorber

    NASA Astrophysics Data System (ADS)

    Benitez, Pablo; Minano, Juan C.; Garcia, Raphael; Mohedano Arroyo, Ruben

    1997-10-01

    Two new types of two-mirror solar concentrator for tubular receiver, the snail concentrator and the helmet concentrator , are presented. The main feature of these concentrators is that they have a sizable gap between the secondary mirror and the absorber, and they still achieve concentrations close to the thermodynamic limit with high collection efficiencies. This characteristic makes them unique and, on the contrary to the present two-stage designs, allows for the location of the secondary outside the evacuated tube. One of the differences between the snail and the helmet concentrators is that the last is symmetric (as the conventional parabolic trough) but the first is not. For an acceptance angle of (alpha) equals +/- 0.73 degs and a collection efficiency of 96.8% (i.e. 3.2% of the rays incident on the primary mirror within the acceptance angle are rejected), the snail concentrator and the helmet concentrator achieve an average flux concentration of 91.1% and 72.8% of the thermodynamic limit, respectively. The gap between the absorber and the secondary mirror is 6.8 and 12.1 times the absorber radius for each concentrator. Moreover, both concentrators have also high rim angles of the primary mirror: +/- 86.2 degs (helmet) and 3.1 - 98.8 degs (snail). This is of interest for a good mechanical stability of the collector.

  7. Catalytic two-stage coal hydrogenation and hydroconversion process

    DOEpatents

    MacArthur, James B.; McLean, Joseph B.; Comolli, Alfred G.

    1989-01-01

    A process for two-stage catalytic hydrogenation and liquefaction of coal to produce increased yields of low-boiling hydrocarbon liquid and gas products. In the process, the particulate coal is slurried with a process-derived liquid solvent and fed at temperature below about 650.degree. F. into a first stage catalytic reaction zone operated at conditions which promote controlled rate liquefaction of the coal, while simultaneously hydrogenating the hydrocarbon recycle oils at conditions favoring hydrogenation reactions. The first stage reactor is maintained at 650.degree.-800.degree. F. temperature, 1000-4000 psig hydrogen partial pressure, and 10-60 lb coal/hr/ft.sup.3 reactor space velocity. The partially hydrogenated material from the first stage reaction zone is passed directly to the close-coupled second stage catalytic reaction zone maintained at a temperature at least about 25.degree. F. higher than for the first stage reactor and within a range of 750.degree.-875.degree. F. temperature for further hydrogenation and thermal hydroconversion reactions. By this process, the coal feed is successively catalytically hydrogenated and hydroconverted at selected conditions, which results in significantly increased yields of desirable low-boiling hydrocarbon liquid products and minimal production of undesirable residuum and unconverted coal and hydrocarbon gases, with use of less energy to obtain the low molecular weight products, while catalyst life is substantially increased.

  8. Two-stage Catalytic Reduction of NOx with Hydrocarbons

    SciTech Connect

    Umit S. Ozkan; Erik M. Holmgreen; Matthew M. Yung; Jonathan Halter; Joel Hiltner

    2005-12-21

    A two-stage system for the catalytic reduction of NO from lean-burn natural gas reciprocating engine exhaust is investigated. Each of the two stages uses a distinct catalyst. The first stage is oxidation of NO to NO{sub 2} and the second stage is reduction of NO{sub 2} to N{sub 2} with a hydrocarbon. The central idea is that since NO{sub 2} is a more easily reduced species than NO, it should be better able to compete with oxygen for the combustion reaction of hydrocarbon, which is a challenge in lean conditions. Early work focused on demonstrating that the N{sub 2} yield obtained when NO{sub 2} was reduced was greater than when NO was reduced. NO{sub 2} reduction catalysts were designed and silver supported on alumina (Ag/Al{sub 2}O{sub 3}) was found to be quite active, able to achieve 95% N{sub 2} yield in 10% O{sub 2} using propane as the reducing agent. The design of a catalyst for NO oxidation was also investigated, and a Co/TiO{sub 2} catalyst prepared by sol-gel was shown to have high activity for the reaction, able to reach equilibrium conversion of 80% at 300 C at GHSV of 50,000h{sup -1}. After it was shown that NO{sub 2} could be more easily reduced to N{sub 2} than NO, the focus shifted on developing a catalyst that could use methane as the reducing agent. The Ag/Al{sub 2}O{sub 3} catalyst was tested and found to be inactive for NOx reduction with methane. Through iterative catalyst design, a palladium-based catalyst on a sulfated-zirconia support (Pd/SZ) was synthesized and shown to be able to selectively reduce NO{sub 2} in lean conditions using methane. Development of catalysts for the oxidation reaction also continued and higher activity, as well as stability in 10% water, was observed on a Co/ZrO{sub 2} catalyst, which reached equilibrium conversion of 94% at 250 C at the same GHSV. The Co/ZrO{sub 2} catalyst was also found to be extremely active for oxidation of CO, ethane, and propane, which could potential eliminate the need for any separate

  9. Cost-effectiveness analysis of population-based screening of hepatocellular carcinoma: Comparing ultrasonography with two-stage screening

    PubMed Central

    Kuo, Ming-Jeng; Chen, Hsiu-Hsi; Chen, Chi-Ling; Fann, Jean Ching-Yuan; Chen, Sam Li-Sheng; Chiu, Sherry Yueh-Hsia; Lin, Yu-Min; Liao, Chao-Sheng; Chang, Hung-Chuen; Lin, Yueh-Shih; Yen, Amy Ming-Fang

    2016-01-01

    AIM: To assess the cost-effectiveness of two population-based hepatocellular carcinoma (HCC) screening programs, two-stage biomarker-ultrasound method and mass screening using abdominal ultrasonography (AUS). METHODS: In this study, we applied a Markov decision model with a societal perspective and a lifetime horizon for the general population-based cohorts in an area with high HCC incidence, such as Taiwan. The accuracy of biomarkers and ultrasonography was estimated from published meta-analyses. The costs of surveillance, diagnosis, and treatment were based on a combination of published literature, Medicare payments, and medical expenditure at the National Taiwan University Hospital. The main outcome measure was cost per life-year gained with a 3% annual discount rate. RESULTS: The results show that the mass screening using AUS was associated with an incremental cost-effectiveness ratio of USD39825 per life-year gained, whereas two-stage screening was associated with an incremental cost-effectiveness ratio of USD49733 per life-year gained, as compared with no screening. Screening programs with an initial screening age of 50 years old and biennial screening interval were the most cost-effective. These findings were sensitive to the costs of screening tools and the specificity of biomarker screening. CONCLUSION: Mass screening using AUS is more cost effective than two-stage biomarker-ultrasound screening. The most optimal strategy is an initial screening age at 50 years old with a 2-year inter-screening interval. PMID:27022228

  10. High-Energy Two-Stage Pulsed Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Markusic, Tom

    2003-01-01

    A high-energy (28 kJ per pulse) two-stage pulsed plasma thruster (MSFC PPT-1) has been constructed and tested. The motivation of this project is to develop a high power (approximately 500 kW), high specific impulse (approximately 10000 s), highly efficient (greater than 50%) thruster for use as primary propulsion in a high power nuclear electric propulsion system. PPT-1 was designed to overcome four negative characteristics which have detracted from the utility of pulsed plasma thrusters: poor electrical efficiency, poor propellant utilization efficiency, electrode erosion, and reliability issues associated with the use of high speed gas valves and high current switches. Traditional PPTs have been plagued with poor efficiency because they have not been operated in a plasma regime that fully exploits the potential benefits of pulsed plasma acceleration by electromagnetic forces. PPTs have generally been used to accelerate low-density plasmas with long current pulses. Operation of thrusters in this plasma regime allows for the development of certain undesirable particle-kinetic effects, such as Hall effect-induced current sheet canting. PPT-1 was designed to propel a highly collisional, dense plasma that has more fluid-like properties and, hence, is more effectively pushed by a magnetic field. The high-density plasma loading into the second stage of the accelerator is achieved through the use of a dense plasma injector (first stage). The injector produces a thermal plasma, derived from a molten lithium propellant feed system, which is subsequently accelerated by the second stage using mega-amp level currents, which eject the plasma at a speed on the order of 100 kilometers per second. Traditional PPTs also suffer from dynamic efficiency losses associated with snowplow loading of distributed neutral propellant. The twostage scheme used in PPT-I allows the propellant to be loaded in a manner which more closely approximates the optimal slug loading. Lithium propellant

  11. Two-Stage Exams Improve Student Learning in an Introductory Geology Course: Logistics, Attendance, and Grades

    ERIC Educational Resources Information Center

    Knierim, Katherine; Turner, Henry; Davis, Ralph K.

    2015-01-01

    Two-stage exams--where students complete part one of an exam closed book and independently and part two is completed open book and independently (two-stage independent, or TS-I) or collaboratively (two-stage collaborative, or TS-C)--provide a means to include collaborative learning in summative assessments. Collaborative learning has been shown to…

  12. An inexact two-stage mixed integer linear programming method for solid waste management in the City of Regina.

    PubMed

    Li, Y P; Huang, G H

    2006-11-01

    In this study, an interval-parameter two-stage mixed integer linear programming (ITMILP) model is developed for supporting long-term planning of waste management activities in the City of Regina. In the ITMILP, both two-stage stochastic programming and interval linear programming are introduced into a general mixed integer linear programming framework. Uncertainties expressed as not only probability density functions but also discrete intervals can be reflected. The model can help tackle the dynamic, interactive and uncertain characteristics of the solid waste management system in the City, and can address issues concerning plans for cost-effective waste diversion and landfill prolongation. Three scenarios are considered based on different waste management policies. The results indicate that reasonable solutions have been generated. They are valuable for supporting the adjustment or justification of the existing waste flow allocation patterns, the long-term capacity planning of the City's waste management system, and the formulation of local policies and regulations regarding waste generation and management.

  13. Performance of an innovative two-stage process converting food waste to hydrogen and methane.

    PubMed

    Han, Sun-Kee; Shin, Hang-Sik

    2004-02-01

    This study was conducted to evaluate the performance of an innovative two-stage process, BIOCELL, that was developed to produce hydrogen (H2) and methane (CH4) from food waste on the basis of phase separation, reactor rotation mode, and sequential batch technique. The BIOCELL process consisted of four leaching-bed reactors for H2 recovery and post-treatment and a UASB reactor for CH4 recovery. The leaching-bed reactors were operated in a rotation mode with a 2-day interval between degradation stages. The sequential batch technique was useful to optimize environmental conditions during H2 fermentation. The BIOCELL process demonstrated that, at the high volatile solids (VS) loading rate of 11.9 kg/m3 x day, it could remove 72.5% of VS and convert VS(removed) to H2 (28.2%) and CH4 (69.9%) on a chemical oxygen demand (COD) basis in 8 days. H2 gas production rate was 3.63 m3/m3 x day, while CH4 gas production rate was 1.75 m3/m3 x day. The yield values of H2 and CH4 were 0.31 and 0.21 m3/kg VS(added), respectively. Moreover, the output from the post-treatment could be used as a soil amendment. The BIOCELL process proved to be stable, reliable, and effective in resource recovery as well as waste stabilization.

  14. Two stages of directed forgetting: Electrophysiological evidence from a short-term memory task.

    PubMed

    Gao, Heming; Cao, Bihua; Qi, Mingming; Wang, Jing; Zhang, Qi; Li, Fuhong

    2016-06-01

    In this study, a short-term memory test was used to investigate the temporal course and neural mechanism of directed forgetting under different memory loads. Within each trial, two memory items with high or low load were presented sequentially, followed by a cue indicating whether the presented items should be remembered. After an interval, subjects were asked to respond to the probe stimuli. The ERPs locked to the cues showed that (a) the effect of cue type was initially observed during the P2 (160-240 ms) time window, with more positive ERPs for remembering relative to forgetting cues; (b) load effects were observed during the N2-P3 (250-500 ms) time window, with more positive ERPs for the high-load than low-load condition; (c) the cue effect was also observed during the N2-P3 time window, with more negative ERPs for forgetting versus remembering cues. These results demonstrated that directed forgetting involves two stages: task-relevance identification and information discarding. The cue effects during the N2 epoch supported the view that directed forgetting is an active process.

  15. A Compact Two-Stage 120 W GaN High Power Amplifier for SweepSAR Radar Systems

    NASA Technical Reports Server (NTRS)

    Thrivikraman, Tushar; Horst, Stephen; Price, Douglas; Hoffman, James; Veilleux, Louise

    2014-01-01

    This work presents the design and measured results of a fully integrated switched power two-stage GaN HEMT high-power amplifier (HPA) achieving 60% power-added efficiency at over 120Woutput power. This high-efficiency GaN HEMT HPA is an enabling technology for L-band SweepSAR interferometric instruments that enable frequent repeat intervals and high-resolution imagery. The L-band HPA was designed using space-qualified state-of-the-art GaN HEMT technology. The amplifier exhibits over 34 dB of power gain at 51 dBm of output power across an 80 MHz bandwidth. The HPA is divided into two stages, an 8 W driver stage and 120 W output stage. The amplifier is designed for pulsed operation, with a high-speed DC drain switch operating at the pulsed-repetition interval and settles within 200 ns. In addition to the electrical design, a thermally optimized package was designed, that allows for direct thermal radiation to maintain low-junction temperatures for the GaN parts maximizing long-term reliability. Lastly, real radar waveforms are characterized and analysis of amplitude and phase stability over temperature demonstrate ultra-stable operation over temperature using integrated bias compensation circuitry allowing less than 0.2 dB amplitude variation and 2 deg phase variation over a 70 C range.

  16. Simulation-based surgical education.

    PubMed

    Evgeniou, Evgenios; Loizou, Peter

    2013-09-01

    The reduction in time for training at the workplace has created a challenge for the traditional apprenticeship model of training. Simulation offers the opportunity for repeated practice in a safe and controlled environment, focusing on trainees and tailored to their needs. Recent technological advances have led to the development of various simulators, which have already been introduced in surgical training. The complexity and fidelity of the available simulators vary, therefore depending on our recourses we should select the appropriate simulator for the task or skill we want to teach. Educational theory informs us about the importance of context in professional learning. Simulation should therefore recreate the clinical environment and its complexity. Contemporary approaches to simulation have introduced novel ideas for teaching teamwork, communication skills and professionalism. In order for simulation-based training to be successful, simulators have to be validated appropriately and integrated in a training curriculum. Within a surgical curriculum, trainees should have protected time for simulation-based training, under appropriate supervision. Simulation-based surgical education should allow the appropriate practice of technical skills without ignoring the clinical context and must strike an adequate balance between the simulation environment and simulators.

  17. DEVELOPMENT OF COLD CLIMATE HEAT PUMP USING TWO-STAGE COMPRESSION

    SciTech Connect

    Shen, Bo; Rice, C Keith; Abdelaziz, Omar; Shrestha, Som S

    2015-01-01

    This paper uses a well-regarded, hardware based heat pump system model to investigate a two-stage economizing cycle for cold climate heat pump applications. The two-stage compression cycle has two variable-speed compressors. The high stage compressor was modelled using a compressor map, and the low stage compressor was experimentally studied using calorimeter testing. A single-stage heat pump system was modelled as the baseline. The system performance predictions are compared between the two-stage and single-stage systems. Special considerations for designing a cold climate heat pump are addressed at both the system and component levels.

  18. Design considerations for single-stage and two-stage pneumatic pellet injectors

    SciTech Connect

    Gouge, M.J.; Combs, S.K.; Fisher, P.W.; Milora, S.L.

    1988-09-01

    Performance of single-stage pneumatic pellet injectors is compared with several models for one-dimensional, compressible fluid flow. Agreement is quite good for models that reflect actual breech chamber geometry and incorporate nonideal effects such as gas friction. Several methods of improving the performance of single-stage pneumatic pellet injectors in the near term are outlined. The design and performance of two-stage pneumatic pellet injectors are discussed, and initial data from the two-stage pneumatic pellet injector test facility at Oak Ridge National Laboratory are presented. Finally, a concept for a repeating two-stage pneumatic pellet injector is described. 27 refs., 8 figs., 3 tabs.

  19. Comparison of classical and two-stage methods of Barkhausen noise measurement

    NASA Astrophysics Data System (ADS)

    Pal'a, Jozef; Bydžovský, Jan

    2014-07-01

    The purpose of the article was to investigate properties of the two-stage methods of the Barkhausen noise (BN) measurement used in non-destructive testing. The principle of the two-stage method is based on subtraction of two successive instances of the electromotive force (EMF) signal with the same non-stochastic (continuous) component. The subtraction can be accomplished in a hardware (hardware two-stage method) or in a software (software two-stage method). The experiments proved that, with these methods, we are able to significantly suppress the dominant continuous component from the induced EMF signal without using filters and thus simplify the measurement. On the other hand, with the classical one-stage method, to achieve similar suppression of the continuous component and, simultaneously, to not suppress the BN, it was necessary to adjust the cut-off frequency of the high-pass filter.

  20. An adaptive two-stage sequential design for sampling rare and clustered populations

    USGS Publications Warehouse

    Brown, J.A.; Salehi, M.M.; Moradi, M.; Bell, G.; Smith, D.R.

    2008-01-01

    How to design an efficient large-area survey continues to be an interesting question for ecologists. In sampling large areas, as is common in environmental studies, adaptive sampling can be efficient because it ensures survey effort is targeted to subareas of high interest. In two-stage sampling, higher density primary sample units are usually of more interest than lower density primary units when populations are rare and clustered. Two-stage sequential sampling has been suggested as a method for allocating second stage sample effort among primary units. Here, we suggest a modification: adaptive two-stage sequential sampling. In this method, the adaptive part of the allocation process means the design is more flexible in how much extra effort can be directed to higher-abundance primary units. We discuss how best to design an adaptive two-stage sequential sample. ?? 2008 The Society of Population Ecology and Springer.

  1. Thermodynamic Analysis and Optimization Based on Exergy Flow for a Two-Staged Pulse Tube Refrigerator

    DTIC Science & Technology

    2010-01-01

    model is convenient for thermodynamic analysis and optimization and shows the important characteristics of two-stage PTRs. Exergy comes into the system ...THERMODYNAMIC ANALYSIS AND OPTIMIZATION BASED ON EXERGY FLOW FOR A TWOSTAGED PULSE TUBE REFRIGERATOR A. Razani, T. Fraser, C. Dodson, and T. Roberts...Prescribed by ANSI Std Z39-18 THERMODYNAMIC ANALYSIS AND OPTIMIZATION BASED ON EXERGY FLOW FOR A TWO-STAGED PULSE TUBE REFRIGERATOR A. Razani 1,3

  2. Two-stage Revision for Periprosthetic Hip and Knee Joint Infections

    PubMed Central

    Kini, Sunil Gurpur; Gabr, Ayman; Das, Rishi; Sukeik, Mohamed; Haddad, Fares Sami

    2016-01-01

    Background: Periprosthetic joint infection (PJI) continues to be one of the leading causes of failure following hip and knee surgery. The diagnostic workflow of PJI includes detailed clinical examination, serum markers, imaging and aspiration/biopsy of the affected joint. The goals of treatment are eradication of the infection, alleviation of pain, and restoration of joint function. Surgical management of PJI consists of debridement, antibiotics and implant retention (DAIR) and single or two-stage revision procedures. Two-stage revision remains the gold standard for treatment of PJIs. We aim to discuss the two stage procedure in this article and report the outcomes. Methods: The first stage of the two stages consists of removal of all components and associated cement with aggressive debridement and placement of an antibiotic-loaded cement spacer. Patients are then treated with variable periods of parenteral antibiotics, followed by an antibiotic free period to help ensure the infection has been eradicated. If the clinical evaluation and serum inflammatory markers suggest infection control, then the second stage can be undertaken and this involves removal of the cement spacer, repeat debridement, and placement of a new prosthesis. Results: Common themes around the two-stage revision procedure include timing of the second stage, antibiotics used in the interim period, length of the interim period before consideration of reimplantation and close liaising with microbiologists. Conclusion: Successful eradication of infection and good functional outcome using the two stage procedure is dependent on a multidisciplinary approach and having a standard reproducible startegy. PMID:28144371

  3. Including sampling and phenotyping costs into the optimization of two stage designs for genomewide association studies.

    PubMed

    Müller, Hans-Helge; Pahl, Roman; Schäfer, Helmut

    2007-12-01

    We propose optimized two-stage designs for genome-wide case-control association studies, using a hypothesis testing paradigm. To save genotyping costs, the complete marker set is genotyped in a sub-sample only (stage I). On stage II, the most promising markers are then genotyped in the remaining sub-sample. In recent publications, two-stage designs were proposed which minimize the overall genotyping costs. To achieve full design optimization, we additionally include sampling costs into both the cost function and the design optimization. The resulting optimal designs differ markedly from those optimized for genotyping costs only (partially optimized designs), and achieve considerable further cost reductions. Compared with partially optimized designs, fully optimized two-stage designs have higher first-stage sample proportion. Furthermore, the increment of the sample size over the one-stage design, which is necessary in two-stage designs in order to compensate for the loss of power due to partial genotyping, is less pronounced for fully optimized two-stage designs. In addition, we address the scenario where the investigator is interested to gain as much information as possible, however is restricted in terms of a budget. In that we develop two-stage designs that maximize the power under a certain cost constraint.

  4. Revision of Infected Total Knee Arthroplasty: Two-Stage Reimplantation Using an Antibiotic-Impregnated Static Spacer

    PubMed Central

    Almeida, Fernando; Renovell, Pablo; Morante, Elena; López, Raúl

    2013-01-01

    Background A two-stage revision remains as the "gold standard" treatment for chronically infected total knee arthroplasties. Methods Forty-five septic knee prostheses were revised with a minimum follow-up of 5 years. Static antibiotic-impregnated cement spacers were used in all cases. Intravenous antibiotics according to sensitivity test of the culture were applied during patients' hospital stay. Oral antibiotics were given for another 5 weeks. Second-stage surgery was undertaken after control of infection with normal erythrocyte sedimentation rate and C-reactive protein values. Extensile techniques were used if needed and metallic augments were employed for bone loss in 32 femoral and 29 tibial revisions. Results The average interval between the first-stage resection and reimplantation was 4.4 months. Significant improvement was obtained with respect to visual analog scale pain and clinical and functional scores, and infection was eradicated in 95.6% of cases following a two-stage revision total knee arthroplasty. Radiographic evaluation showed suitable alignment without signs of mechanical loosening. Conclusions This technique is a reasonable procedure to eradicate chronic infection in knee arthroplasty and provides proper functional and clinical results. However, it sometimes requires extensile surgical approaches that could imply arduous surgeries. Metallic augments with cementless stems available in most of the knee revision systems are a suitable alternative to handle bone deficiencies, avoiding the use of bone allografts with its complications. PMID:24009903

  5. Technology and staging effects on two-stage-to-orbit systems

    NASA Technical Reports Server (NTRS)

    Wilhite, Alan W.

    1991-01-01

    Horizontal takeoff and landing two-stage systems with an airbreathing first stage and rocket second stage are evaluated for staging Mach numbers that range from 5 to 14. All systems are evaluated with advanced technologies being developed in the NASP Program and sized to the same mission requirements. With these advanced technologies, the two-stage systems are heavier than the single stage. The weights of the two-stage systems are closely related to staging. Using a rocket on the first stage to accelerate from the turboramjet limit of Mach 6 to Mach 10 signiificantly decreases dry weight as compared to the Mach 6-staged system. The optimum dry weight staging Mach number for the scramjet two-stage system is Mach 12. At a 40 percent weight growth (current technology level), the scramjet two-stage systems are half the weight and less sensitive to weight changes than the single stage, but still require substantial technology development in the areas of inlets, nozzles, ramjet propulsion, active cooling, and high-temperature structures.

  6. Development of a replacement for trichloroethylene in the two-stage cleaning process

    SciTech Connect

    Harding, W.B.

    1992-12-01

    A solvent was sought to replace trichloroethylene in the two-stage cleaning process that is used in the Allied-Signal Inc., Kansas City Division (KCD) Miniature Electro-Mechanical Assembly Department. The process is an ultrasonic cleaning process in which product is first cleaned in trichloroethylene and then in isopropyl alcohol. After a general review of the properties of available solvents, isopropyl alcohol, d-limonene, and a synthetic mineral spirits, were chosen to be evaluated as trichloroethylene replacements. Stainless steel test panels were cleaned and then soiled with several different organic materials. Certain of the panels were cleaned by the two-stage process. The others were cleaned by the two-stage process using one or another of the solvents under evaluation in the place of the trichloroethylene. The cleanliness of the panels was determined by Auger and photoelectron spectroscopy. The panels cleaned with any of the three solvents under evaluation were found to be as clean as those cleaned by the standard two-stage process. Because of simplicity and minimization of inventory, it is recommended that the two-stage process be changed to use isopropyl alcohol in both stages.

  7. Application of acidic thermal treatment for one- and two-stage anaerobic digestion of sewage sludge.

    PubMed

    Takashima, M; Tanaka, Y

    2010-01-01

    The effectiveness of acidic thermal treatment (ATT) was examined in a 106-day continuous experiment, when applied to one- or two-stage anaerobic digestion of sewage sludge (4.3% TS). The ATT was performed at 170 °C and pH 5 for 1 hour (sulfuric acid for lowering pH). The one-stage process was mesophilic at 20 days hydraulic retention time (HRT), and incorporated the ATT as pre-treatment. The two-stage process consisted of a thermophilic digester at 5 days HRT and a mesophilic digester at 15 days HRT, and incorporated the ATT as interstage-treatment. On average, VSS reduction was 48.7% for the one-stage control, 65.8% for the one-stage ATT, 52.7% for the two-stage control and 67.6% for the two-stage ATT. Therefore, VSS reduction was increased by 15-17%, when the ATT was combined in both one- and two-stage processes. In addition, the dewaterability of digested sludge was remarkably improved, and phosphate release was enhanced. On the other hand, total methane production did not differ significantly, and color generation was noted in the digested sludge solutions with the ATT. In conclusion, the anaerobic digestion with ATT can be an attractive alternative for sludge reduction, handling, and phosphorus recovery.

  8. Accuracy of the One-Stage and Two-Stage Impression Techniques: A Comparative Analysis.

    PubMed

    Jamshidy, Ladan; Mozaffari, Hamid Reza; Faraji, Payam; Sharifi, Roohollah

    2016-01-01

    Introduction. One of the main steps of impression is the selection and preparation of an appropriate tray. Hence, the present study aimed to analyze and compare the accuracy of one- and two-stage impression techniques. Materials and Methods. A resin laboratory-made model, as the first molar, was prepared by standard method for full crowns with processed preparation finish line of 1 mm depth and convergence angle of 3-4°. Impression was made 20 times with one-stage technique and 20 times with two-stage technique using an appropriate tray. To measure the marginal gap, the distance between the restoration margin and preparation finish line of plaster dies was vertically determined in mid mesial, distal, buccal, and lingual (MDBL) regions by a stereomicroscope using a standard method. Results. The results of independent test showed that the mean value of the marginal gap obtained by one-stage impression technique was higher than that of two-stage impression technique. Further, there was no significant difference between one- and two-stage impression techniques in mid buccal region, but a significant difference was reported between the two impression techniques in MDL regions and in general. Conclusion. The findings of the present study indicated higher accuracy for two-stage impression technique than for the one-stage impression technique.

  9. High pressure studies using two-stage diamond micro-anvils grown by chemical vapor deposition

    DOE PAGES

    Vohra, Yogesh K.; Samudrala, Gopi K.; Moore, Samuel L.; ...

    2015-06-10

    Ultra-high static pressures have been achieved in the laboratory using a two-stage micro-ball nanodiamond anvils as well as a two-stage micro-paired diamond anvils machined using a focused ion-beam system. The two-stage diamond anvils’ designs implemented thus far suffer from a limitation of one diamond anvil sliding past another anvil at extreme conditions. We describe a new method of fabricating two-stage diamond micro-anvils using a tungsten mask on a standard diamond anvil followed by microwave plasma chemical vapor deposition (CVD) homoepitaxial diamond growth. A prototype two stage diamond anvil with 300 μm culet and with a CVD diamond second stage ofmore » 50 μm in diameter was fabricated. We have carried out preliminary high pressure X-ray diffraction studies on a sample of rare-earth metal lutetium sample with a copper pressure standard to 86 GPa. Furthermore, the micro-anvil grown by CVD remained intact during indentation of gasket as well as on decompression from the highest pressure of 86 GPa.« less

  10. High pressure studies using two-stage diamond micro-anvils grown by chemical vapor deposition

    SciTech Connect

    Vohra, Yogesh K.; Samudrala, Gopi K.; Moore, Samuel L.; Montgomery, Jeffrey M.; Tsoi, Georgiy M.; Velisavljevic, Nenad

    2015-06-10

    Ultra-high static pressures have been achieved in the laboratory using a two-stage micro-ball nanodiamond anvils as well as a two-stage micro-paired diamond anvils machined using a focused ion-beam system. The two-stage diamond anvils’ designs implemented thus far suffer from a limitation of one diamond anvil sliding past another anvil at extreme conditions. We describe a new method of fabricating two-stage diamond micro-anvils using a tungsten mask on a standard diamond anvil followed by microwave plasma chemical vapor deposition (CVD) homoepitaxial diamond growth. A prototype two stage diamond anvil with 300 μm culet and with a CVD diamond second stage of 50 μm in diameter was fabricated. We have carried out preliminary high pressure X-ray diffraction studies on a sample of rare-earth metal lutetium sample with a copper pressure standard to 86 GPa. Furthermore, the micro-anvil grown by CVD remained intact during indentation of gasket as well as on decompression from the highest pressure of 86 GPa.

  11. Accuracy of the One-Stage and Two-Stage Impression Techniques: A Comparative Analysis

    PubMed Central

    Jamshidy, Ladan; Faraji, Payam; Sharifi, Roohollah

    2016-01-01

    Introduction. One of the main steps of impression is the selection and preparation of an appropriate tray. Hence, the present study aimed to analyze and compare the accuracy of one- and two-stage impression techniques. Materials and Methods. A resin laboratory-made model, as the first molar, was prepared by standard method for full crowns with processed preparation finish line of 1 mm depth and convergence angle of 3-4°. Impression was made 20 times with one-stage technique and 20 times with two-stage technique using an appropriate tray. To measure the marginal gap, the distance between the restoration margin and preparation finish line of plaster dies was vertically determined in mid mesial, distal, buccal, and lingual (MDBL) regions by a stereomicroscope using a standard method. Results. The results of independent test showed that the mean value of the marginal gap obtained by one-stage impression technique was higher than that of two-stage impression technique. Further, there was no significant difference between one- and two-stage impression techniques in mid buccal region, but a significant difference was reported between the two impression techniques in MDL regions and in general. Conclusion. The findings of the present study indicated higher accuracy for two-stage impression technique than for the one-stage impression technique. PMID:28003824

  12. Interval Training

    MedlinePlus

    ... before trying any type of interval training. Recent studies suggest, however, that interval training can be used safely for short periods even in individuals with heart disease. Also keep the risk of overuse injury in mind. If you rush into a strenuous workout before ...

  13. Effects of earthworm casts and zeolite on the two-stage composting of green waste.

    PubMed

    Zhang, Lu; Sun, Xiangyang

    2015-05-01

    Because it helps protect the environment and encourages economic development, composting has become a viable method for organic waste disposal. The objective of this study was to investigate the effects of earthworm casts (EWCs) (at 0.0%, 0.30%, and 0.60%) and zeolite (clinoptilolite, CL) (at 0%, 15%, and 25%) on the two-stage composting of green waste. The combination of EWCs and CL improved the conditions of the composting process and the quality of the compost products in terms of the thermophilic phase, humification, nitrification, microbial numbers and enzyme activities, the degradation of cellulose and hemicellulose, and physico-chemical characteristics and nutrient contents of final composts. The compost matured in only 21days with the optimized two-stage composting method rather than in the 90-270days required for traditional composting. The optimal two-stage composting and the best quality compost were obtained with 0.30% EWCs and 25% CL.

  14. Design and construction of the X-2 two-stage free piston driven expansion tube

    NASA Technical Reports Server (NTRS)

    Doolan, Con

    1995-01-01

    This report outlines the design and construction of the X-2 two-stage free piston driven expansion tube. The project has completed its construction phase and the facility has been installed in the new impulsive research laboratory where commissioning is about to take place. The X-2 uses a unique, two-stage driver design which allows a more compact and lower overall cost free piston compressor. The new facility has been constructed in order to examine the performance envelope of the two-stage driver and how well it couple to sub-orbital and super-orbital expansion tubes. Data obtained from these experiments will be used for the design of a much larger facility, X-3, utilizing the same free piston driver concept.

  15. Rapid two-stage Starnes procedure for a symptomatic neonate with Ebstein anomaly.

    PubMed

    Kajihara, Noriyoshi; Asou, Toshihide; Takeda, Yuko; Kosaka, Yoshimichi; Onakatomi, Yasuko; Miyata, Daiki; Yasui, Seiyo

    2010-12-01

    We present a rapid two-stage Starnes procedure for a seriously symptomatic neonate with the prenatal diagnosis of Ebstein anomaly. At 16 hours after birth, we performed an emergency operation consisting of main pulmonary artery ligation, plication of the right atrial and right ventricular wall, modified Blalock-Taussig shunt, and patent ductus arteriosus ligation, without cardiopulmonary bypass. At age 12 days, we then performed the Starnes procedure using a glutaraldehyde-treated autologous pericardial patch with a 4-mm fenestration to close the tricuspid valve orifice. The infant's postoperative course was excellent. A rapid two-stage Starnes procedure is useful for treating a seriously symptomatic neonate with Ebstein anomaly.

  16. Mechanisms to deploy the two-stage IUS from the shuttle cargo bay

    NASA Technical Reports Server (NTRS)

    Haynie, H. T.

    1980-01-01

    The Inertial Upper Stage (IUS) is a two-stage or three-stage booster used to transport spacecraft from the space shuttle orbit to synchronous orbit or on an interplanetary trajectory. The mechanisms which were designed specifically to perform the two-stage IUS required functions while contained within the cargo bay of the space shuttle during the boost phase and while in a low Earth orbit are discussed. The requirements, configuration, and operation of the mechanisms are described, with particular emphasis on the tilt actuator and the mechanism for decoupling the actuators during boost to eliminate redundant load paths.

  17. Randomized two-stage Phase II clinical trial designs based on Barnard's exact test.

    PubMed

    Shan, Guogen; Ma, Changxing; Hutson, Alan D; Wilding, Gregory E

    2013-01-01

    In areas such as oncology, two-stage designs are often preferred as compared to one-stage designs due to the ability to stop the trial early when faced with evidence of lack of sufficient efficacy and the associated sample size savings. We present exact two-stage designs based on Barnard's exact test for differences in proportions and compare the designs to those proposed by Kepner ( 2010 ) and Jung ( 2010 ). In addition, we present tables of decision rules under a variety of assumed realities for use in trial planning. The procedure is recommended for use due to the substantial sample size savings experienced.

  18. Advancing Early Detection of Autism Spectrum Disorder by Applying an Integrated Two-Stage Screening Approach

    ERIC Educational Resources Information Center

    Oosterling, Iris J.; Wensing, Michel; Swinkels, Sophie H.; van der Gaag, Rutger Jan; Visser, Janne C.; Woudenberg, Tim; Minderaa, Ruud; Steenhuis, Mark-Peter; Buitelaar, Jan K.

    2010-01-01

    Background: Few field trials exist on the impact of implementing guidelines for the early detection of autism spectrum disorders (ASD). The aims of the present study were to develop and evaluate a clinically relevant integrated early detection programme based on the two-stage screening approach of Filipek et al. (1999), and to expand the evidence…

  19. Two-Stage Sampling Procedures for Comparing Means When Population Distributions Are Non-Normal.

    ERIC Educational Resources Information Center

    Luh, Wei-Ming; Olejnik, Stephen

    Two-stage sampling procedures for comparing two population means when variances are heterogeneous have been developed by D. G. Chapman (1950) and B. K. Ghosh (1975). Both procedures assume sampling from populations that are normally distributed. The present study reports on the effect that sampling from non-normal distributions has on Type I error…

  20. Assessing Compliance-Effect Bias in the Two Stage Least Squares Estimator

    ERIC Educational Resources Information Center

    Reardon, Sean; Unlu, Fatih; Zhu, Pei; Bloom, Howard

    2011-01-01

    The proposed paper studies the bias in the two-stage least squares, or 2SLS, estimator that is caused by the compliance-effect covariance (hereafter, the compliance-effect bias). It starts by deriving the formula for the bias in an infinite sample (i.e., in the absence of finite sample bias) under different circumstances. Specifically, it…

  1. Treatment of corn ethanol distillery wastewater using two-stage anaerobic digestion.

    PubMed

    Ráduly, B; Gyenge, L; Szilveszter, Sz; Kedves, A; Crognale, S

    In this study the mesophilic two-stage anaerobic digestion (AD) of corn bioethanol distillery wastewater is investigated in laboratory-scale reactors. Two-stage AD technology separates the different sub-processes of the AD in two distinct reactors, enabling the use of optimal conditions for the different microbial consortia involved in the different process phases, and thus allowing for higher applicable organic loading rates (OLRs), shorter hydraulic retention times (HRTs) and better conversion rates of the organic matter, as well as higher methane content of the produced biogas. In our experiments the reactors have been operated in semi-continuous phase-separated mode. A specific methane production of 1,092 mL/(L·d) has been reached at an OLR of 6.5 g TCOD/(L·d) (TCOD: total chemical oxygen demand) and a total HRT of 21 days (5.7 days in the first-stage, and 15.3 days in the second-stage reactor). Nonetheless the methane concentration in the second-stage reactor was very high (78.9%); the two-stage AD outperformed the reference single-stage AD (conducted at the same reactor loading rate and retention time) by only a small margin in terms of volumetric methane production rate. This makes questionable whether the higher methane content of the biogas counterbalances the added complexity of the two-stage digestion.

  2. Overcoming the bottlenecks of anaerobic digestion of olive mill solid waste by two-stage fermentation.

    PubMed

    Stoyanova, Elitza; Lundaa, Tserennyam; Bochmann, Günther; Fuchs, Werner

    2017-02-01

    Two-stage anaerobic digestion (AD) of two-phase olive mill solid waste (OMSW) was applied for reducing the inhibiting factors by optimizing the acidification stage. Single-stage AD and co-fermentation with chicken manure were conducted coinstantaneous for direct comparison. Degradation of the polyphenols up to 61% was observed during the methanogenic stage. Nevertheless the concentration of phenolic substances was still high; the two-stage fermentation remained stable at OLR 1.5 kgVS/m³day. The buffer capacity of the system was twice as high, compared to the one-stage fermentation, without additives. The two-stage AD was a combined process - thermophilic first stage and mesophilic second stage, which pointed out to be the most profitable for AD of OMSW for the reduced hydraulic retention time (HRT) from 230 to 150 days, and three times faster than the single-stage and the co-fermentation start-up of the fermentation. The optimal HRT and incubation temperature for the first stage were determined to four days and 55°C. The performance of the two-stage AD concerning the stability of the process was followed by the co-digestion of OMSW with chicken manure as a nitrogen-rich co-substrate, which makes them viable options for waste disposal with concomitant energy recovery.

  3. Innovative two-stage anaerobic process for effective codigestion of cheese whey and cattle manure.

    PubMed

    Bertin, Lorenzo; Grilli, Selene; Spagni, Alessandro; Fava, Fabio

    2013-01-01

    The valorisation of agroindustrial waste through anaerobic digestion represents a significant opportunity for refuse treatment and renewable energy production. This study aimed to improve the codigestion of cheese whey (CW) and cattle manure (CM) by an innovative two-stage process, based on concentric acidogenic and methanogenic phases, designed for enhancing performance and reducing footprint. The optimum CW to CM ratio was evaluated under batch conditions. Thereafter, codigestion was implemented under continuous-flow conditions comparing one- and two-stage processes. The results demonstrated that the addition of CM in codigestion with CW greatly improved the anaerobic process. The highest methane yield was obtained co-treating the two substrates at equal ratio by using the innovative two-stage process. The proposed system reached the maximum value of 258 mL(CH4) g(gv(-1), which was more than twice the value obtained by the one-stage process and 10% higher than the value obtained by the two-stage one.

  4. Identifying combined design and analysis procedures in two-stage trials with a binary end point.

    PubMed

    Bowden, Jack; Wason, James

    2012-12-20

    Two-stage trial designs provide the flexibility to stop early for efficacy or futility and are popular because they have a smaller sample size on average than a traditional trial has with the same type I and II error rates. This makes them financially attractive but also has the ethical benefit of reducing, in the long run, the number of patients who are given ineffective treatments. Designs that minimise the expected sample size are often referred to as 'optimal'. However, two-stage designs can impart a substantial bias into the parameter estimate at the end of the trial. In this paper, we argue that the expected performance of one's chosen estimation method should also be considered when deciding on a two-stage trial design. We review the properties of standard and bias-adjusted maximum likelihood estimators as well as mean and median unbiased estimators. We then identify optimal two-stage design and analysis procedures that balance projected sample size considerations with those of estimator performance. We make available software to implement this new methodology.

  5. A Two-Stage Exercise on the Binomial Distribution Using Minitab.

    ERIC Educational Resources Information Center

    Shibli, M. Abdullah

    1990-01-01

    Describes a two-stage experiment that was designed to explain binomial distribution to undergraduate statistics students. A manual coin flipping exercise is explained as the first stage; a computerized simulation using MINITAB software is presented as stage two; and output from the MINITAB exercises is included. (two references) (LRW)

  6. Response Bias Using Two-Stage Data Collection: A Study of Elderly Participants in a Program.

    ERIC Educational Resources Information Center

    Goodfellow, Marianne; And Others

    1988-01-01

    This study assessed the nature of response bias in a two-stage data-collection design (telephone interviews followed by a questionnaire mailing), which was used to examine the effectiveness of a state-level pharmaceutical assistance program for the elderly. Demographic and health factors affecting response (N=1,705 elderly persons) are discussed.…

  7. Use a Log Splitter to Demonstrate Two-Stage Hydraulic Pump

    ERIC Educational Resources Information Center

    Dell, Timothy W.

    2012-01-01

    The two-stage hydraulic pump is commonly used in many high school and college courses to demonstrate hydraulic systems. Unfortunately, many textbooks do not provide a good explanation of how the technology works. Another challenge that instructors run into with teaching hydraulic systems is the cost of procuring an expensive real-world machine…

  8. EVALUATION OF A TWO-STAGE PASSIVE TREATMENT APPROACH FOR MINING INFLUENCE WATERS

    EPA Science Inventory

    A two-stage passive treatment approach was assessed at bench-scale using two Colorado Mining Influenced Waters (MIWs). The first-stage was a limestone drain with the purpose of removing iron and aluminum and mitigating the potential effects of mineral acidity. The second stage w...

  9. A two-stage spectrum sensing scheme based on energy detection and a novel multitaper method

    NASA Astrophysics Data System (ADS)

    Qi, Pei-Han; Li, Zan; Si, Jiang-Bo; Xiong, Tian-Yi

    2015-04-01

    Wideband spectrum sensing has drawn much attention in recent years since it provides more opportunities to the secondary users. However, wideband spectrum sensing requires a long time and a complex mechanism at the sensing terminal. A two-stage wideband spectrum sensing scheme is considered to proceed spectrum sensing with low time consumption and high performance to tackle this predicament. In this scheme, a novel multitaper spectrum sensing (MSS) method is proposed to mitigate the poor performance of energy detection (ED) in the low signal-to-noise ratio (SNR) region. The closed-form expression of the decision threshold is derived based on the Neyman-Pearson criterion and the probability of detection in the Rayleigh fading channel is analyzed. An optimization problem is formulated to maximize the probability of detection of the proposed two-stage scheme and the average sensing time of the two-stage scheme is analyzed. Numerical results validate the efficiency of MSS and show that the two-stage spectrum sensing scheme enjoys higher performance in the low SNR region and lower time cost in the high SNR region than the single-stage scheme. Project supported by the National Natural Science Foundation of China (Grant No. 61301179), the China Postdoctoral Science Foundation (Grant No. 2014M550479), and the Doctorial Programs Foundation of the Ministry of Education, China (Grant No. 20110203110011).

  10. Thermal design of two-stage evaporative cooler based on thermal comfort criterion

    NASA Astrophysics Data System (ADS)

    Gilani, Neda; Poshtiri, Amin Haghighi

    2016-09-01

    Performance of two-stage evaporative coolers at various outdoor air conditions was numerically studied, and its geometric and physical characteristics were obtained based on thermal comfort criteria. For this purpose, a mathematical model was developed based on conservation equations of mass, momentum and energy to determine heat and mass transfer characteristics of the system. The results showed that two-stage indirect/direct cooler can provide the thermal comfort condition when outdoor air temperature and relative humidity are located in the range of 34-54 °C and 10-60 %, respectively. Moreover, as relative humidity of the ambient air rises, two-stage evaporative cooler with the smaller direct and larger indirect cooler will be needed. In building with high cooling demand, thermal comfort may be achieved at a greater air change per hour number, and thus an expensive two-stage evaporative cooler with a higher electricity consumption would be required. Finally, a design guideline was proposed to determine the size of required plate heat exchangers at various operating conditions.

  11. Magnetic induction system for two-stage gun projectile velocity measurements

    SciTech Connect

    Moody, R L; Konrad, C H

    1984-05-01

    A magnetic induction technique for measuring projectile velocities has been implemented on Sandia's two-stage light gas gun. The system has been designed to allow for projectile velocity measurements to an accuracy of approx. 0.2 percent. The velocity system has been successfully tested in a velocity range of 3.5 km/s to 6.5 km/s.

  12. Magnetic gauge instrumentation on the LANL gas-driven two-stage gun

    SciTech Connect

    Alcon, R.R.; Sheffield, S.A.; Martinez, A.R.; Gustavsen, R.L.

    1997-11-01

    The LANL gas-driven two-stage gun was designed and built to do initiation studies on insensitive high explosives as well as equation of state and reaction experiments on other materials. The preferred method of measuring reaction phenomena involves the use of in-situ magnetic particle velocity gauges. In order to accommodate this type of gauging in the two-stage gun, it has a 50-mm-diameter launch tube. The authors have sued magnetic gauging on the 72-mm bore diameter single-stage gun for over 15 years and it has proven a very effective technique for all types of shock wave experiments, including those on high explosives. This technique has now been installed on the gas-driven two-stage gun. They describe the method used, as well as some of the difficulties that arose during the installation. Several magnetic gauge experiments have been completed on plastic materials. Waveforms obtained in some of the experiments will be discussed. Up to 10 in-situ particle velocity measurements can be made in a single experiment. This new technique is now working quite well, as is evidenced by the data. To their knowledge, this is the first time magnetic gauging has been used on a two-stage gun.

  13. Changes to the LANL gas-driven two-stage gun: Magnetic gauge instrumentation, etc.

    SciTech Connect

    Sheffield, S.A.; Gustavsen, R.L.; Martinez, A.R.; Alcon, R.R.

    1996-12-31

    Our gas-driven two-stage gun was designed and built to do initiation studies on insensitive high explosives as well as other equation of state experiments on inert materials. Our preferred method of measuring initiation phenomena involves the use of magnetic particle velocity gauges. In order to accommodate this type of gauging in our two-stage gun, projectile velocity was sacrificed in favor of a larger experimental target area (obtained by using a 50 mm diameter launch tube). We have used magnetic gauging on our 72-mm bore diameter single-stage gun for over 15 years and it has proven a very effective technique to monitor reactive shock wave evolution. This technique has now been adapted to our gas-driven two-stage gun. We describe the method used, as well as some of the difficulties that arose while installing this technique. Several magnetic gauge experiments have been completed on plastic materials. Waveforms obtained in one experiment are given, along with the Hugoniot information that was obtained. This new technique is now working quite well, as is evidenced by the data. To our knowledge, this is the first time magnetic gauging has been used on a two-stage gun. We have also made changes to the burst diaphragm package in the transition section to ensure that the petals do not break off during the opening process and to increase the burst pressure. This will also be discussed briefly.

  14. Biomass waste gasification - Can be the two stage process suitable for tar reduction and power generation?

    SciTech Connect

    Sulc, Jindrich; Stojdl, Jiri; Richter, Miroslav; Popelka, Jan; Svoboda, Karel; Smetana, Jiri; Vacek, Jiri; Skoblja, Siarhei; Buryan, Petr

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Comparison of one stage (co-current) and two stage gasification of wood pellets. Black-Right-Pointing-Pointer Original arrangement with grate-less reactor and upward moving bed of the pellets. Black-Right-Pointing-Pointer Two stage gasification leads to drastic reduction of tar content in gas. Black-Right-Pointing-Pointer One stage gasification produces gas with higher LHV at lower overall ER. Black-Right-Pointing-Pointer Content of ammonia in gas is lower in two stage moving bed gasification. - Abstract: A pilot scale gasification unit with novel co-current, updraft arrangement in the first stage and counter-current downdraft in the second stage was developed and exploited for studying effects of two stage gasification in comparison with one stage gasification of biomass (wood pellets) on fuel gas composition and attainable gas purity. Significant producer gas parameters (gas composition, heating value, content of tar compounds, content of inorganic gas impurities) were compared for the two stage and the one stage method of the gasification arrangement with only the upward moving bed (co-current updraft). The main novel features of the gasifier conception include grate-less reactor, upward moving bed of biomass particles (e.g. pellets) by means of a screw elevator with changeable rotational speed and gradual expanding diameter of the cylindrical reactor in the part above the upper end of the screw. The gasifier concept and arrangement are considered convenient for thermal power range 100-350 kW{sub th}. The second stage of the gasifier served mainly for tar compounds destruction/reforming by increased temperature (around 950 Degree-Sign C) and for gasification reaction of the fuel gas with char. The second stage used additional combustion of the fuel gas by preheated secondary air for attaining higher temperature and faster gasification of the remaining char from the first stage. The measurements of gas composition and tar

  15. Evaluation of the two-stage ditch as a best management practice

    NASA Astrophysics Data System (ADS)

    Hodaj, A.; Bowling, L. C.; Cibin, R.; Chaubey, I.

    2015-12-01

    Artificial drainage has long been an important component of agriculture in the poorly-drained regions of the US Corn Belt. Continued increases in drainage intensity funnel more water into existing drainage ditches, resulting in higher flood stages, more erosive water velocities and decreased time for in-channel nutrient processing. The two-stage ditch is a type of in-stream restoration that involves modification of a trapezoidal drainage ditch to resemble more the features of a natural stream. The idea is to create or simulate extended benches on both sides of the ditch that would develop naturally over a period of time in a stream because of geomorphological processes. These in-channel flood plains provide a greater flow area during high flow events and offer the potential to reduce sediment load and extend the interaction time between water and vegetation on the benches, allowing larger uptake of nutrients and increasing the denitrification rates in the bench soil. The Soil and Water Assessment Tool (SWAT) hydrologic model has recently been modified to represent the two-stage ditch as a conservation practice. Processes that are represented in the model include: velocity reductions due to the change in channel geometry, particle settling, plant nutrient uptake and denitrification on the benches of the two-stage ditch. The model is evaluated using data collected from a two-stage ditch constructed at the Throckmorton Purdue Agricultural Center (TPAC) near Lafayette, Indiana in September 2012. It drains an area of approximately 2.7 km2 of farmland used for corn and soybean production. Simulation results for 30 years of weather data indicated the impact of the two-stage ditch on reducing peak flow rates, flood stage and nutrient loads. For this 30 year period, 1985 - 2014, the results showed reductions of up to 40% of peak flow velocities, 35% reduction per km of two-stage ditch, of sediment basin output, 10 - 80% reduction in total phosphorus output and 0 - 15

  16. A two-stage ultrafiltration and nanofiltration process for recycling dairy wastewater.

    PubMed

    Luo, Jianquan; Ding, Luhui; Qi, Benkun; Jaffrin, Michel Y; Wan, Yinhua

    2011-08-01

    A two-stage ultrafiltration and nanofiltration (UF/NF) process for the treatment of model dairy wastewater was investigated to recycle nutrients and water from the wastewater. Ultracel PLGC and NF270 membranes were found to be the most suitable for this purpose. In the first stage, protein and lipid were concentrated by the Ultracel PLGC UF membrane and could be used for algae cultivation to produce biodiesel and biofuel, and the permeate from UF was concentrated by the NF270 membrane in the second stage to obtain lactose in retentate and reusable water in permeate, while the NF retentate could be recycled for anaerobic digestion to produce biogas. With this approach, most of dairy wastewater could be recycled to produce reusable water and substrates for bioenergy production. Compared with the single NF process, this two-stage UF/NF process had a higher efficiency and less membrane fouling.

  17. A Two Stage Solution Procedure for Production Planning System with Advance Demand Information

    NASA Astrophysics Data System (ADS)

    Ueno, Nobuyuki; Kadomoto, Kiyotaka; Hasuike, Takashi; Okuhara, Koji

    We model for ‘Naiji System’ which is a unique corporation technique between a manufacturer and suppliers in Japan. We propose a two stage solution procedure for a production planning problem with advance demand information, which is called ‘Naiji’. Under demand uncertainty, this model is formulated as a nonlinear stochastic programming problem which minimizes the sum of production cost and inventory holding cost subject to a probabilistic constraint and some linear production constraints. By the convexity and the special structure of correlation matrix in the problem where inventory for different periods is not independent, we propose a solution procedure with two stages which are named Mass Customization Production Planning & Management System (MCPS) and Variable Mesh Neighborhood Search (VMNS) based on meta-heuristics. It is shown that the proposed solution procedure is available to get a near optimal solution efficiently and practical for making a good master production schedule in the suppliers.

  18. Two-Stage Cementless Revision Total Hip Arthroplasty for Infected Primary Hip Arthroplasties.

    PubMed

    Camurcu, Yalkin; Sofu, Hakan; Buyuk, Abdul Fettah; Gursu, Sarper; Kaygusuz, Mehmet Akif; Sahin, Vedat

    2015-09-01

    The main purpose of the present study was to analyze the clinical features, the most common infective agents, and the results of two-stage total hip revision using a teicoplanin-impregnated spacer. Between January 2005 and July 2011, 41 patients were included. At the clinical status analysis, physical examination was performed, Harris hip score was noted, isolated microorganisms were recorded, and the radiographic evaluation was performed. The mean Harris hip score was improved from 38.9 ± 9.6 points to 81.8 ± 5.8 points (P<0.05). Infection was eradicated in 39 hips. Radiographic evidence of stability was noted in 37 acetabular revision components, and all femoral stems. Two-stage revision of the infected primary hip arthroplasty is a time-consuming but a reliable procedure with high rates of success.

  19. Toward Improving Electrocardiogram (ECG) Biometric Verification using Mobile Sensors: A Two-Stage Classifier Approach.

    PubMed

    Tan, Robin; Perkowski, Marek

    2017-02-20

    Electrocardiogram (ECG) signals sensed from mobile devices pertain the potential for biometric identity recognition applicable in remote access control systems where enhanced data security is demanding. In this study, we propose a new algorithm that consists of a two-stage classifier combining random forest and wavelet distance measure through a probabilistic threshold schema, to improve the effectiveness and robustness of a biometric recognition system using ECG data acquired from a biosensor integrated into mobile devices. The proposed algorithm is evaluated using a mixed dataset from 184 subjects under different health conditions. The proposed two-stage classifier achieves a total of 99.52% subject verification accuracy, better than the 98.33% accuracy from random forest alone and 96.31% accuracy from wavelet distance measure algorithm alone. These results demonstrate the superiority of the proposed algorithm for biometric identification, hence supporting its practicality in areas such as cloud data security, cyber-security or remote healthcare systems.

  20. Gas pollutants removal in a single- and two-stage ejector-venturi scrubber.

    PubMed

    Gamisans, Xavier; Sarrà, Montserrrat; Lafuente, F Javier

    2002-03-29

    The absorption of SO(2) and NH(3) from the flue gas into NaOH and H(2)SO(4) solutions, respectively has been studied using an industrial scale ejector-venturi scrubber. A statistical methodology is presented to characterise the performance of the scrubber by varying several factors such as gas pollutant concentration, air flowrate and absorbing solution flowrate. Some types of venturi tube constructions were assessed, including the use of a two-stage venturi tube. The results showed a strong influence of the liquid scrubbing flowrate on pollutant removal efficiency. The initial pollutant concentration and the gas flowrate had a slight influence. The use of a two-stage venturi tube considerably improved the absorption efficiency, although it increased energy consumption. The results of this study will be applicable to the optimal design of venturi-based absorbers for gaseous pollution control or chemical reactors.

  1. An adaptive two-stage dose-response design method for establishing Proof of Concept

    PubMed Central

    Franchetti, Yoko; Anderson, Stewart J.; Sampson, Allan R.

    2013-01-01

    We propose an adaptive two-stage dose-response design where a pre-specified adaptation rule is used to add and/or drop treatment arms between the stages. We extend the multiple comparison procedures-modeling (MCP-Mod) approach into a two-stage design. In each stage, we use the same set of candidate dose-response models and test for a dose-response relationship or proof of concept (PoC) via model-associated statistics. The stage-wise test results are then combined to establish ‘global’ PoC using a conditional error function. Our simulation studies showed good and more robust power in our design method compared to conventional and fixed designs. PMID:23957520

  2. Toward Improving Electrocardiogram (ECG) Biometric Verification using Mobile Sensors: A Two-Stage Classifier Approach

    PubMed Central

    Tan, Robin; Perkowski, Marek

    2017-01-01

    Electrocardiogram (ECG) signals sensed from mobile devices pertain the potential for biometric identity recognition applicable in remote access control systems where enhanced data security is demanding. In this study, we propose a new algorithm that consists of a two-stage classifier combining random forest and wavelet distance measure through a probabilistic threshold schema, to improve the effectiveness and robustness of a biometric recognition system using ECG data acquired from a biosensor integrated into mobile devices. The proposed algorithm is evaluated using a mixed dataset from 184 subjects under different health conditions. The proposed two-stage classifier achieves a total of 99.52% subject verification accuracy, better than the 98.33% accuracy from random forest alone and 96.31% accuracy from wavelet distance measure algorithm alone. These results demonstrate the superiority of the proposed algorithm for biometric identification, hence supporting its practicality in areas such as cloud data security, cyber-security or remote healthcare systems. PMID:28230745

  3. Two-stage combustion for reducing pollutant emissions from gas turbine combustors

    NASA Technical Reports Server (NTRS)

    Clayton, R. M.; Lewis, D. H.

    1981-01-01

    Combustion and emission results are presented for a premix combustor fueled with admixtures of JP5 with neat H2 and of JP5 with simulated partial-oxidation product gas. The combustor was operated with inlet-air state conditions typical of cruise power for high performance aviation engines. Ultralow NOx, CO and HC emissions and extended lean burning limits were achieved simultaneously. Laboratory scale studies of the non-catalyzed rich-burning characteristics of several paraffin-series hydrocarbon fuels and of JP5 showed sooting limits at equivalence ratios of about 2.0 and that in order to achieve very rich sootless burning it is necessary to premix the reactants thoroughly and to use high levels of air preheat. The application of two-stage combustion for the reduction of fuel NOx was reviewed. An experimental combustor designed and constructed for two-stage combustion experiments is described.

  4. Sample size reassessment for a two-stage design controlling the false discovery rate

    PubMed Central

    Zehetmayer, Sonja; Graf, Alexandra C.; Posch, Martin

    2016-01-01

    Sample size calculations for gene expression microarray and NGS-RNA-Seq experiments are challenging because the overall power depends on unknown quantities as the proportion of true null hypotheses and the distribution of the effect sizes under the alternative. We propose a two-stage design with an adaptive interim analysis where these quantities are estimated from the interim data. The second stage sample size is chosen based on these estimates to achieve a specific overall power. The proposed procedure controls the power in all considered scenarios except for very low first stage sample sizes. The false discovery rate (FDR) is controlled despite of the data dependent choice of sample size. The two-stage design can be a useful tool to determine the sample size of high-dimensional studies if in the planning phase there is high uncertainty regarding the expected effect sizes and variability. PMID:26461844

  5. Two stage bioethanol refining with multi litre stacked microbial fuel cell and microbial electrolysis cell.

    PubMed

    Sugnaux, Marc; Happe, Manuel; Cachelin, Christian Pierre; Gloriod, Olivier; Huguenin, Gérald; Blatter, Maxime; Fischer, Fabian

    2016-12-01

    Ethanol, electricity, hydrogen and methane were produced in a two stage bioethanol refinery setup based on a 10L microbial fuel cell (MFC) and a 33L microbial electrolysis cell (MEC). The MFC was a triple stack for ethanol and electricity co-generation. The stack configuration produced more ethanol with faster glucose consumption the higher the stack potential. Under electrolytic conditions ethanol productivity outperformed standard conditions and reached 96.3% of the theoretically best case. At lower external loads currents and working potentials oscillated in a self-synchronized manner over all three MFC units in the stack. In the second refining stage, fermentation waste was converted into methane, using the scale up MEC stack. The bioelectric methanisation reached 91% efficiency at room temperature with an applied voltage of 1.5V using nickel cathodes. The two stage bioethanol refining process employing bioelectrochemical reactors produces more energy vectors than is possible with today's ethanol distilleries.

  6. Matching Characteristics of J35-A-23 Compressor and Two-stage Turbine

    NASA Technical Reports Server (NTRS)

    Dugan, James F., Jr.; Rebeske, John J., Jr.; Finger, Harold B.

    1951-01-01

    Component data on the J35-A-23 compressor and two-stage turbine were used to determine the problems in matching the two units for operatio n in a turbojet engine. Possible operating regions were determined an d an equilibrium operating line was also determined for the assumed c onditions of zero flight speed and a jet nozzle area approximately 5. 5 percent greater than the wide-open nozzle area.

  7. Latent Inhibition as a Function of US Intensity in a Two-Stage CER Procedure

    ERIC Educational Resources Information Center

    Rodriguez, Gabriel; Alonso, Gumersinda

    2004-01-01

    An experiment is reported in which the effect of unconditioned stimulus (US) intensity on latent inhibition (LI) was examined, using a two-stage conditioned emotional response (CER) procedure in rats. A tone was used as the pre-exposed and conditioned stimulus (CS), and a foot-shock of either a low (0.3 mA) or high (0.7 mA) intensity was used as…

  8. Effect of Two-Stage Aging on Microstructure of 7075 Aluminum Alloys

    DTIC Science & Technology

    1981-04-01

    which particular microstructural characteristic is of greatest significance in the stress corrosion behavior of 7075 in a high strength condition. 2...is expected that RRA may provide less improvement in the stress corrosion behavior of 7050 than of I I 7075 . Data from these tests would allow...I v h EFFECT OF TWO-STAGE AGING ON MICROSTRUCTURE OF 7075 ALUMINUM ALLOYS RE- 627 "Final Report E April 1981 "by 7! Jonn M. Papazian OT i. Prepared

  9. A two-stage monolithic buffer amplifier for 20 GHz satellite communication

    NASA Technical Reports Server (NTRS)

    Petersen, W. C.; Gupta, A. K.

    1983-01-01

    Design, fabrication, and test results of a two-stage GaAs monolithic buffer amplifier for 20 GHz satellite communication are described in this paper. A gain of 13 + or - 0.75 dB from 17.7 to 20.2 GHz was obtained from the 1.5 x 1.5 millimeter chip, which includes all necessary bias and dc blocking circuitry.

  10. Impressions in cleft lip and palate--a novel two stage technique.

    PubMed

    Pani, Sharat Chandra; Hedge, Amitha M

    2008-01-01

    Though the field of presurgical orthopedics for the management of children with cleft Lip and Palate (CLAP) has made great advances over the past few decades, little is found in literature regarding the imressions required to fabricate these appliances. The purpose of this paper is to describe a novel two stage technique utilizing greenstick compound and addition silicone impression material to provide a safe, economical and accurate method for recording impressions in children with cleft lip and palate.

  11. [Two-stage hepatectomy for hepatic metastasis and supra renal vena cava reconstruction].

    PubMed

    Nicoluzzi, João Eduardo

    2012-12-01

    Two-stage hepatectomy uses compensatory liver regeneration after a first noncurative hepatectomy to enable a second curative resection. Herein we report the tecnical aspects of the management of a thirty-seven years-old woman with colorectal metastasis to the liver eligible because single resection could not achieve complete treatment, even in combination with chemotherapy, portal embolization, or radiofrequency, but tumors could be totally removed by two sequential resections.

  12. Effects of Endwall Geometry and Stacking on Two-Stage Supersonic Turbine Performance

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.; Griffin, Lisa W.; Huber, Frank W.; Sondak, Douglas L.; Turner, Jim (Technical Monitor)

    2002-01-01

    Two methods are commonly used to control the secondary/separated flows (and associated losses) in supersonic turbines: endwall contouring and airfoil stacking. In the current investigation the flow path between the first-stage vanes and rotors, and the stacking of the first-stage vanes were varied in an effort to improve turbine performance. The geometric variations have been studied by performing a series of unsteady three-dimensional numerical simulations for the two-stage turbine.

  13. Two stage dual gate MESFET monolithic gain control amplifier for Ka-band

    NASA Astrophysics Data System (ADS)

    Sokolov, V.; Geddes, J.; Contolatis, A.

    A monolithic two stage gain control amplifier has been developed using submicron gate length dual gate MESFETs fabricated on ion implanted material. The amplifier has a gain of 12 dB at 30 GHz with a gain control range of over 30 dB. This ion implanted monolithic IC is readily integrable with other phased array receiver functions such as low noise amplifiers and phase shifters.

  14. Two-stage/single-stage reversible pump-turbine with supplying pump

    SciTech Connect

    Brcar, A.

    1980-08-12

    In a hydroelectric facility, a vertically mounted rotatable shaft is connected to a motor-generator and carries a pumpturbine with a supplying pump disposed below and immersed in water, the supplying pump disengaging from the shaft when the pump-turbine is driving the motor-generator and engaging the shaft when the motor-generator is driving the pump-turbine and supplying pump, thereby providing a two-stage pumping mode and a single-stage generating mode.

  15. Development of a two-stage membrane-based wash-water reclamation subsystem

    NASA Technical Reports Server (NTRS)

    Mccray, S. B.

    1988-01-01

    A two-stage membrane-based subsystem was designed and constructed to enable the recycle of wash waters generated in space. The first stage is a fouling-resistant tube-side-feed hollow-fiber ultrafiltration module, and the second stage is a spiral-wound reverse-osmosis module. Throughout long-term tests, the subsystem consistently produced high-quality permeate, processing actual wash water to 95 percent recovery.

  16. Effect of casing treatment on performance of a two-stage high-pressure-ratio fan

    NASA Technical Reports Server (NTRS)

    Urasek, D. C.

    1979-01-01

    A two-stage fan, previously tested with a solid casing, was tested with a casing with circumferential grooves over the tips of both rotors (casing treatment). Tests were conducted at 80 and 100 percent of design speed with uniform flow. The casing treatment improved the flow range and stall margin significantly without changing the characteristics overall performance curves of total-pressure and efficiency as functions of weight flow, other than extending them to lower weight flows.

  17. Effects of earthworm casts and zeolite on the two-stage composting of green waste

    SciTech Connect

    Zhang, Lu Sun, Xiangyang

    2015-05-15

    Highlights: • Earthworm casts (EWCs) and clinoptilolite (CL) were used in green waste composting. • Addition of EWCs + CL improved physico-chemical and microbiological properties. • Addition of EWCs + CL extended the duration of thermophilic periods during composting. • Addition of EWCs + CL enhanced humification, cellulose degradation, and nutrients. • Combined addition of 0.30% EWCs + 25% CL reduced composting time to 21 days. - Abstract: Because it helps protect the environment and encourages economic development, composting has become a viable method for organic waste disposal. The objective of this study was to investigate the effects of earthworm casts (EWCs) (at 0.0%, 0.30%, and 0.60%) and zeolite (clinoptilolite, CL) (at 0%, 15%, and 25%) on the two-stage composting of green waste. The combination of EWCs and CL improved the conditions of the composting process and the quality of the compost products in terms of the thermophilic phase, humification, nitrification, microbial numbers and enzyme activities, the degradation of cellulose and hemicellulose, and physico-chemical characteristics and nutrient contents of final composts. The compost matured in only 21 days with the optimized two-stage composting method rather than in the 90–270 days required for traditional composting. The optimal two-stage composting and the best quality compost were obtained with 0.30% EWCs and 25% CL.

  18. Technology of streptomycin sulfate separation by two-stage foam separation.

    PubMed

    Li, Juan; Wu, Zhaoliang; Li, Rui

    2012-01-01

    Industrial discharges from manufacturing streptomycin sulfate (SS) are inhibitory to biological wastewater treatment and need to be stripped of residual SS. For effective SS recovery from the wastewater, a two-stage foam separation technology was investigated using a column with a vertical ellipsoid-shaped channel (VEC) and a conventional one, and sodium dodecyl sulfate (SDS) served as the collector. The mechanism of enhancing foam drainage by VEC was theoretically analyzed. In the first stage, the column with VEC was used and under the optimal conditions of the liquid-loading volume 300 mL, volumetric airflow rate 100 mL/min, the initial pH 7.0 and the molar ratio of SDS to SS 8.0, an improved SS enrichment ratio of 16.7 was obtained. In the second stage, a conventional column was used and with a volumetric airflow rate of 450 mL/min, the foamate had a SS concentration of about 0.5 g/L, so it was used as the feed solution of the first stage. By the two-stage technology, the total SS recovery percentage reached as high as 99.7%. Thus, it was significantly effective for the two-stage foam separation technology to recover SS from the simulative wastewater.

  19. Economics of spray-dryer FGD system: the two-stage open-loop processes

    SciTech Connect

    Burnett, T.A.; O'Brien, W.E.

    1981-06-01

    Preliminary economics of the Rockwell International Corporation - Wheelabrator Frye, Inc., (RI/WF) two-stage open-loop flue gas desulfurization (FGD) process were determined for both lime and soda ash absorbents. This two-stage open-loop process is a throwaway system in which the alkali raw material (as a solution or slurry) is sprayed into the flue gas stream, dried by the latent heat in the hot flue gas, and collected as dry particulate matter in a baghouse. The fly ash is also collected in the baghouse as an inherent part of the process. An economic evaluation of a limestone slurry FGD process with an electrostatic precipitator (ESP) for particulate matter removal was included for comparison. The basis was a 500-MW power plant burning 3.5% sulfur, 16% ash coal with 90% SO/sub 2/ removal and 0.1 lb/MBtu particulate matter emission. The economic evaluations were made using both TVA and Electric Power Research Institute (EPRI) economic premises. Cost differences between the two-stage open-loop lime and soda ash versions are largely the result of different waste disposal and raw material costs. Both RI/WF versions are more economical than limestone in most process elements except raw material costs. Cost differences between the TVA- and EPRI-based estimates are the result of different methods of estimating indirect costs, levelizing operating costs, and different raw material costs.

  20. Industrial demonstration plant for the gasification of herb residue by fluidized bed two-stage process.

    PubMed

    Zeng, Xi; Shao, Ruyi; Wang, Fang; Dong, Pengwei; Yu, Jian; Xu, Guangwen

    2016-04-01

    A fluidized bed two-stage gasification process, consisting of a fluidized-bed (FB) pyrolyzer and a transport fluidized bed (TFB) gasifier, has been proposed to gasify biomass for fuel gas production with low tar content. On the basis of our previous fundamental study, an autothermal two-stage gasifier has been designed and built for gasify a kind of Chinese herb residue with a treating capacity of 600 kg/h. The testing data in the operational stable stage of the industrial demonstration plant showed that when keeping the reaction temperatures of pyrolyzer and gasifier respectively at about 700 °C and 850 °C, the heating value of fuel gas can reach 1200 kcal/Nm(3), and the tar content in the produced fuel gas was about 0.4 g/Nm(3). The results from this pilot industrial demonstration plant fully verified the feasibility and technical features of the proposed FB two-stage gasification process.

  1. Performance analysis of RDF gasification in a two stage fluidized bed-plasma process.

    PubMed

    Materazzi, M; Lettieri, P; Taylor, R; Chapman, C

    2016-01-01

    The major technical problems faced by stand-alone fluidized bed gasifiers (FBG) for waste-to gas applications are intrinsically related to the composition and physical properties of waste materials, such as RDF. The high quantity of ash and volatile material in RDF can provide a decrease in thermal output, create high ash clinkering, and increase emission of tars and CO2, thus affecting the operability for clean syngas generation at industrial scale. By contrast, a two-stage process which separates primary gasification and selective tar and ash conversion would be inherently more forgiving and stable. This can be achieved with the use of a separate plasma converter, which has been successfully used in conjunction with conventional thermal treatment units, for the ability to 'polish' the producer gas by organic contaminants and collect the inorganic fraction in a molten (and inert) state. This research focused on the performance analysis of a two-stage fluid bed gasification-plasma process to transform solid waste into clean syngas. Thermodynamic assessment using the two-stage equilibrium method was carried out to determine optimum conditions for the gasification of RDF and to understand the limitations and influence of the second stage on the process performance (gas heating value, cold gas efficiency, carbon conversion efficiency), along with other parameters. Comparison with a different thermal refining stage, i.e. thermal cracking (via partial oxidation) was also performed. The analysis is supported by experimental data from a pilot plant.

  2. Rehabilitation outcomes in patients with early and two-stage reconstruction of flexor tendon injuries

    PubMed Central

    Sade, Ilgin; İnanir, Murat; Şen, Suzan; Çakmak, Esra; Kablanoğlu, Serkan; Selçuk, Barin; Dursun, Nigar

    2016-01-01

    [Purpose] The primary aim of this study was to assess rehabilitation outcomes for early and two-stage repair of hand flexor tendon injuries. The secondary purpose of this study was to compare the findings between treatment groups. [Subjects and Methods] Twenty-three patients were included in this study. Early repair (n=14) and two-stage repair (n=9) groups were included in a rehabilitation program that used hand splints. This retrospective evaluated patients according to their demographic characteristics, including age, gender, injured hand, dominant hand, cause of injury, zone of injury, number of affected fingers, and accompanying injuries. Pain, range of motion, and grip strength were evaluated using a visual analog scale, goniometer, and dynamometer, respectively. [Results] Both groups showed significant improvements in pain and finger flexion after treatment compared with baseline measurements. However, no significant differences were observed between the two treatment groups. Similar results were obtained for grip strength and pinch grip, whereas gross grip was better in the early tendon repair group. [Conclusion] Early and two-stage reconstruction of patients with flexor tendon injuries can be performed with similarly favorable responses and effective rehabilitation programs. PMID:27630400

  3. Bias in estimating the causal hazard ratio when using two-stage instrumental variable methods.

    PubMed

    Wan, Fei; Small, Dylan; Bekelman, Justin E; Mitra, Nandita

    2015-06-30

    Two-stage instrumental variable methods are commonly used to estimate the causal effects of treatments on survival in the presence of measured and unmeasured confounding. Two-stage residual inclusion (2SRI) has been the method of choice over two-stage predictor substitution (2SPS) in clinical studies. We directly compare the bias in the causal hazard ratio estimated by these two methods. Under a principal stratification framework, we derive a closed-form solution for asymptotic bias of the causal hazard ratio among compliers for both the 2SPS and 2SRI methods when survival time follows the Weibull distribution with random censoring. When there is no unmeasured confounding and no always takers, our analytic results show that 2SRI is generally asymptotically unbiased, but 2SPS is not. However, when there is substantial unmeasured confounding, 2SPS performs better than 2SRI with respect to bias under certain scenarios. We use extensive simulation studies to confirm the analytic results from our closed-form solutions. We apply these two methods to prostate cancer treatment data from Surveillance, Epidemiology and End Results-Medicare and compare these 2SRI and 2SPS estimates with results from two published randomized trials.

  4. Is the continuous two-stage anaerobic digestion process well suited for all substrates?

    PubMed

    Lindner, Jonas; Zielonka, Simon; Oechsner, Hans; Lemmer, Andreas

    2016-01-01

    Two-stage anaerobic digestion systems are often considered to be advantageous compared to one-stage processes. Although process conditions and fermenter setups are well examined, overall substrate degradation in these systems is controversially discussed. Therefore, the aim of this study was to investigate how substrates with different fibre and sugar contents (hay/straw, maize silage, sugar beet) influence the degradation rate and methane production. Intermediates and gas compositions, as well as methane yields and VS-degradation degrees were recorded. The sugar beet substrate lead to a higher pH-value drop 5.67 in the acidification reactor, which resulted in a six time higher hydrogen production in comparison to the hay/straw substrate (pH-value drop 5.34). As the achieved yields in the two-stage system showed a difference of 70.6% for the hay/straw substrate, and only 7.8% for the sugar beet substrate. Therefore two-stage systems seem to be only recommendable for digesting sugar rich substrates.

  5. A two-stage Stirling-type pulse tube cryocooler with a cold inertance tube

    NASA Astrophysics Data System (ADS)

    Gan, Z. H.; Fan, B. Y.; Wu, Y. Z.; Qiu, L. M.; Zhang, X. J.; Chen, G. B.

    2010-06-01

    A thermally coupled two-stage Stirling-type pulse tube cryocooler (PTC) with inertance tubes as phase shifters has been designed, manufactured and tested. In order to obtain a larger phase shift at the low acoustic power of about 2.0 W, a cold inertance tube as well as a cold reservoir for the second stage, precooled by the cold end of the first stage, was introduced into the system. The transmission line model was used to calculate the phase shift produced by the cold inertance tube. Effect of regenerator material, geometry and charging pressure on the performance of the second stage of the two-stage PTC was investigated based on the well known regenerator model REGEN. Experimental results of the two-stage PTC were carried out with an emphasis on the performance of the second stage. A lowest cooling temperature of 23.7 K and 0.50 W at 33.9 K were obtained with an input electric power of 150.0 W and an operating frequency of 40 Hz.

  6. Two-stage residual inclusion estimation: addressing endogeneity in health econometric modeling.

    PubMed

    Terza, Joseph V; Basu, Anirban; Rathouz, Paul J

    2008-05-01

    The paper focuses on two estimation methods that have been widely used to address endogeneity in empirical research in health economics and health services research-two-stage predictor substitution (2SPS) and two-stage residual inclusion (2SRI). 2SPS is the rote extension (to nonlinear models) of the popular linear two-stage least squares estimator. The 2SRI estimator is similar except that in the second-stage regression, the endogenous variables are not replaced by first-stage predictors. Instead, first-stage residuals are included as additional regressors. In a generic parametric framework, we show that 2SRI is consistent and 2SPS is not. Results from a simulation study and an illustrative example also recommend against 2SPS and favor 2SRI. Our findings are important given that there are many prominent examples of the application of inconsistent 2SPS in the recent literature. This study can be used as a guide by future researchers in health economics who are confronted with endogeneity in their empirical work.

  7. Research on a novel two-stage direct current hybrid circuit breaker.

    PubMed

    Wu, Yifei; Wu, Yi; Rong, Mingzhe; Yang, Fei; Niu, Chunping; Li, Mei; Hu, Yang

    2014-08-01

    The DC hybrid circuit breaker based on high-speed switch (HSS) and parallel connected capacitor has been widely applied in the fault current breaking of DC system. However, when the current is commutated from HSS to the capacitor according to single-stage operation, the capacitor has to absorb a large amount of energy stored in the system inductance within very short time. Meanwhile, a high over-voltage rate of rise is especially prone to be produced between the contacts of HSS, which will lead to a failed breaking. As a result, a novel DC hybrid circuit breaker based on the two-stage operation is proposed and analyzed in this paper. By controlling the thyristors in the commutation branches, the fault current is fast commutated into the capacitor, which can not only realize the arcless open of HSS, but also decrease the over-voltage rate of rise significantly in comparison to the traditional single-stage operation. The simulation model of fault current breaking under different conditions in 10 kV medium voltage DC system is constructed. The simulated over-voltages of single-stage and two-stage operations in the case of fault current breaking are compared and analyzed. Finally, the fault current breaking test in the two-stage operation is investigated experimentally, which validates the feasibility and effectiveness of the simulation model well.

  8. Empirical study of classification process for two-stage turbo air classifier in series

    NASA Astrophysics Data System (ADS)

    Yu, Yuan; Liu, Jiaxiang; Li, Gang

    2013-05-01

    The suitable process parameters for a two-stage turbo air classifier are important for obtaining the ultrafine powder that has a narrow particle-size distribution, however little has been published internationally on the classification process for the two-stage turbo air classifier in series. The influence of the process parameters of a two-stage turbo air classifier in series on classification performance is empirically studied by using aluminum oxide powders as the experimental material. The experimental results show the following: 1) When the rotor cage rotary speed of the first-stage classifier is increased from 2 300 r/min to 2 500 r/min with a constant rotor cage rotary speed of the second-stage classifier, classification precision is increased from 0.64 to 0.67. However, in this case, the final ultrafine powder yield is decreased from 79% to 74%, which means the classification precision and the final ultrafine powder yield can be regulated through adjusting the rotor cage rotary speed of the first-stage classifier. 2) When the rotor cage rotary speed of the second-stage classifier is increased from 2 500 r/min to 3 100 r/min with a constant rotor cage rotary speed of the first-stage classifier, the cut size is decreased from 13.16 μm to 8.76 μm, which means the cut size of the ultrafine powder can be regulated through adjusting the rotor cage rotary speed of the second-stage classifier. 3) When the feeding speed is increased from 35 kg/h to 50 kg/h, the "fish-hook" effect is strengthened, which makes the ultrafine powder yield decrease. 4) To weaken the "fish-hook" effect, the equalization of the two-stage wind speeds or the combination of a high first-stage wind speed with a low second-stage wind speed should be selected. This empirical study provides a criterion of process parameter configurations for a two-stage or multi-stage classifier in series, which offers a theoretical basis for practical production.

  9. River water quality management considering agricultural return flows: application of a nonlinear two-stage stochastic fuzzy programming.

    PubMed

    Tavakoli, Ali; Nikoo, Mohammad Reza; Kerachian, Reza; Soltani, Maryam

    2015-04-01

    In this paper, a new fuzzy methodology is developed to optimize water and waste load allocation (WWLA) in rivers under uncertainty. An interactive two-stage stochastic fuzzy programming (ITSFP) method is utilized to handle parameter uncertainties, which are expressed as fuzzy boundary intervals. An iterative linear programming (ILP) is also used for solving the nonlinear optimization model. To accurately consider the impacts of the water and waste load allocation strategies on the river water quality, a calibrated QUAL2Kw model is linked with the WWLA optimization model. The soil, water, atmosphere, and plant (SWAP) simulation model is utilized to determine the quantity and quality of each agricultural return flow. To control pollution loads of agricultural networks, it is assumed that a part of each agricultural return flow can be diverted to an evaporation pond and also another part of it can be stored in a detention pond. In detention ponds, contaminated water is exposed to solar radiation for disinfecting pathogens. Results of applying the proposed methodology to the Dez River system in the southwestern region of Iran illustrate its effectiveness and applicability for water and waste load allocation in rivers. In the planning phase, this methodology can be used for estimating the capacities of return flow diversion system and evaporation and detention ponds.

  10. A two-stage extraction procedure for insensitive munition (IM) explosive compounds in soils.

    PubMed

    Felt, Deborah; Gurtowski, Luke; Nestler, Catherine C; Johnson, Jared; Larson, Steven

    2016-12-01

    The Department of Defense (DoD) is developing a new category of insensitive munitions (IMs) that are more resistant to detonation or promulgation from external stimuli than traditional munition formulations. The new explosive constituent compounds are 2,4-dinitroanisole (DNAN), nitroguanidine (NQ), and nitrotriazolone (NTO). The production and use of IM formulations may result in interaction of IM component compounds with soil. The chemical properties of these IM compounds present unique challenges for extraction from environmental matrices such as soil. A two-stage extraction procedure was developed and tested using several soil types amended with known concentrations of IM compounds. This procedure incorporates both an acidified phase and an organic phase to account for the chemical properties of the IM compounds. The method detection limits (MDLs) for all IM compounds in all soil types were <5 mg/kg and met non-regulatory risk-based Regional Screening Level (RSL) criteria for soil proposed by the U.S. Army Public Health Center. At defined environmentally relevant concentrations, the average recovery of each IM compound in each soil type was consistent and greater than 85%. The two-stage extraction method decreased the influence of soil composition on IM compound recovery. UV analysis of NTO established an isosbestic point based on varied pH at a detection wavelength of 341 nm. The two-stage soil extraction method is equally effective for traditional munition compounds, a potentially important point when examining soils exposed to both traditional and insensitive munitions.

  11. Two-stage hybrid feature selection algorithms for diagnosing erythemato-squamous diseases.

    PubMed

    Xie, Juanying; Lei, Jinhu; Xie, Weixin; Shi, Yong; Liu, Xiaohui

    2013-01-01

    This paper proposes two-stage hybrid feature selection algorithms to build the stable and efficient diagnostic models where a new accuracy measure is introduced to assess the models. The two-stage hybrid algorithms adopt Support Vector Machines (SVM) as a classification tool, and the extended Sequential Forward Search (SFS), Sequential Forward Floating Search (SFFS), and Sequential Backward Floating Search (SBFS), respectively, as search strategies, and the generalized F-score (GF) to evaluate the importance of each feature. The new accuracy measure is used as the criterion to evaluated the performance of a temporary SVM to direct the feature selection algorithms. These hybrid methods combine the advantages of filters and wrappers to select the optimal feature subset from the original feature set to build the stable and efficient classifiers. To get the stable, statistical and optimal classifiers, we conduct 10-fold cross validation experiments in the first stage; then we merge the 10 selected feature subsets of the 10-cross validation experiments, respectively, as the new full feature set to do feature selection in the second stage for each algorithm. We repeat the each hybrid feature selection algorithm in the second stage on the one fold that has got the best result in the first stage. Experimental results show that our proposed two-stage hybrid feature selection algorithms can construct efficient diagnostic models which have got better accuracy than that built by the corresponding hybrid feature selection algorithms without the second stage feature selection procedures. Furthermore our methods have got better classification accuracy when compared with the available algorithms for diagnosing erythemato-squamous diseases.

  12. Murine susceptibility to two-stage skin carcinogenesis is influenced by the agent used for promotion

    SciTech Connect

    Reiners, J.J. Jr.; Nesnow, S.; Slaga, T.J.

    1984-01-01

    Several approaches were employed to investigate whether murine stock and strain differences in susceptibility to two-stage skin carcinogenesis are due to differences in the metabolism of the initiating aromatic hydrocarbons, or the consequences of the agents used for promotion. A cell-mediated mutagenesis assay was used to quantitatively compare the abilities of cultured newborn SENCAR, DBA/2, C57BL/6 and BALB/c keratinocytes to metabolize dimethylbenz(a)anthracene (DMBA) to mutagenic and cytotoxic metabolites. At equivalent concentrations of DMBA, throughout a 25-fold range in promutagen concentration, C57BL/6, BALB/c and SENCAR keratinocyte-dependent mutant frequencies were very similar and approximately twice DBA/2 keratinocyte-dependent mutant frequencies. In in vivo tumor studies, C57BL/6 mice were more sensitive than SENCAR mice to complete skin carcinogenesis protocols employing repetitive weekly treatments with DMBA and benzo(a)pyrene (BP). At equivalent concentrations of either DMBA or BP, C57BL/6 mice developed carcinomas sooner, and had a greater number of carcinomas per animal. SENCAR mice were very sensitive to two-stage skin carcinogenesis protocols employing BP and DMBA as initiators and benzoyl peroxide and 12-O-tetradecanoylphorbol-13-acetate (TPA) as promoters. C57BL/6 mice were relatively refractory to TPA promotion but sensitive to promotion with benzoyl peroxide. These findings suggest that murine stock and strain-dependent differences in sensitivity to two-stage skin carcinogenesis may not be due to major differences in the metabolism of the initiating hydrocarbons, but are partially the consequences of the agents for promotion. 24 references, 5 figures, 1 table.

  13. An adaptive Simon Two-Stage Design for Phase 2 studies of targeted therapies.

    PubMed

    Jones, Cheryl L; Holmgren, Eric

    2007-09-01

    The field of specialized medicine and clinical development programs for targeted cancer therapies are rapidly expanding. The proposed Phase 2 design allows for preliminary determination of efficacy that may be restricted to a particular sub-population defined by biomarker status (presence/absence). The design is an adaptation of the Simon Two-Stage Design. We provide examples where the adaptation can result in substantial savings in sample size and thus potentially lead to greater efficiency in decision making during the drug development process.

  14. Space Station Freedom carbon dioxide removal assembly two-stage rotary sliding vane pump

    NASA Astrophysics Data System (ADS)

    Matteau, Dennis

    1992-07-01

    The design and development of a positive displacement pump selected to operate as an essential part of the carbon dioxide removal assembly (CDRA) are described. An oilless two-stage rotary sliding vane pump was selected as the optimum concept to meet the CDRA application requirements. This positive displacement pump is characterized by low weight and small envelope per unit flow, ability to pump saturated gases and moderate amount of liquid, small clearance volumes, and low vibration. It is easily modified to accommodate several stages on a single shaft optimizing space and weight, which makes the concept ideal for a range of demanding space applications.

  15. CHaracteristics of Two-Stage Absorption Heat Pump Cycler Driven by Waste Heat From Gas Engine

    NASA Astrophysics Data System (ADS)

    Kojima, Hiroshi; Akisawa, Atsushi; Kashiwagi, Takao

    Recently the energy conservation is expected from the global environment protection view point. In this study, a new concept of a compound gas cooling system using treated sewage water combining a gas engine heat pump and an absorption heat pump is proposed. In this system, the absorption heat pump is driven by the waste heat from the gas engine. In this paper, first, the best absorption cycle for this absorption heat pump is selected for the cooling and heating mode. And finally the simulation model of the two-stage absorption heat pumps for heating mode is demonstrated and the static characteristics are clarified.

  16. Titanium-copper-nitride coated spacers for two-stage revision of infected total hip endoprostheses

    PubMed Central

    Ellenrieder, Martin; Haenle, Maximilian; Lenz, Robert; Bader, Rainer; Mittelmeier, Wolfram

    2011-01-01

    Within the first two years after total hip arthroplasty implant-associated infection has become the second most common reason for a revision surgery. Two-stage implant exchange is frequently conducted using temporary spacers made of antibiotic-loaded cement in order to prevent a bacterial colonization on the spacer. Avoiding several disadvantages of cement spacers, a conventional hemi-endoprosthesis was equipped with a copper-containing implant coating for inhibition of bacterial biofilms. In the present paper details of this novel treatment concept are presented including a case report. PMID:22242097

  17. Use of two-stage membrane countercurrent cascade for natural gas purification from carbon dioxide

    NASA Astrophysics Data System (ADS)

    Kurchatov, I. M.; Laguntsov, N. I.; Karaseva, M. D.

    2016-09-01

    Membrane technology scheme is offered and presented as a two-stage countercurrent recirculating cascade, in order to solve the problem of natural gas dehydration and purification from CO2. The first stage is a single divider, and the second stage is a recirculating two-module divider. This scheme allows natural gas to be cleaned from impurities, with any desired degree of methane extraction. In this paper, the optimal values of the basic parameters of the selected technological scheme are determined. An estimation of energy efficiency was carried out, taking into account the energy consumption of interstage compressor and methane losses in energy units.

  18. Biomass waste gasification - can be the two stage process suitable for tar reduction and power generation?

    PubMed

    Sulc, Jindřich; Stojdl, Jiří; Richter, Miroslav; Popelka, Jan; Svoboda, Karel; Smetana, Jiří; Vacek, Jiří; Skoblja, Siarhei; Buryan, Petr

    2012-04-01

    A pilot scale gasification unit with novel co-current, updraft arrangement in the first stage and counter-current downdraft in the second stage was developed and exploited for studying effects of two stage gasification in comparison with one stage gasification of biomass (wood pellets) on fuel gas composition and attainable gas purity. Significant producer gas parameters (gas composition, heating value, content of tar compounds, content of inorganic gas impurities) were compared for the two stage and the one stage method of the gasification arrangement with only the upward moving bed (co-current updraft). The main novel features of the gasifier conception include grate-less reactor, upward moving bed of biomass particles (e.g. pellets) by means of a screw elevator with changeable rotational speed and gradual expanding diameter of the cylindrical reactor in the part above the upper end of the screw. The gasifier concept and arrangement are considered convenient for thermal power range 100-350 kW(th). The second stage of the gasifier served mainly for tar compounds destruction/reforming by increased temperature (around 950°C) and for gasification reaction of the fuel gas with char. The second stage used additional combustion of the fuel gas by preheated secondary air for attaining higher temperature and faster gasification of the remaining char from the first stage. The measurements of gas composition and tar compound contents confirmed superiority of the two stage gasification system, drastic decrease of aromatic compounds with two and higher number of benzene rings by 1-2 orders. On the other hand the two stage gasification (with overall ER=0.71) led to substantial reduction of gas heating value (LHV=3.15 MJ/Nm(3)), elevation of gas volume and increase of nitrogen content in fuel gas. The increased temperature (>950°C) at the entrance to the char bed caused also substantial decrease of ammonia content in fuel gas. The char with higher content of ash leaving the

  19. Two-stage fixed-bed gasifier with selectable middle gas off-take point

    DOEpatents

    Strickland, Larry D.; Bissett, Larry A.

    1992-01-01

    A two-stage fixed bed coal gasifier wherein an annular region is in registry with a gasification zone underlying a devolatilization zone for extracting a side stream of high temperature substantially tar-free gas from the gasifier. A vertically displaceable skirt means is positioned within the gasifier to define the lower portion of the annular region so that vertical displacement of the skirt means positions the inlet into the annular region in a selected location within or in close proximity to the gasification zone for providing a positive control over the composition of the side stream gas.

  20. Titanium-copper-nitride coated spacers for two-stage revision of infected total hip endoprostheses.

    PubMed

    Ellenrieder, Martin; Haenle, Maximilian; Lenz, Robert; Bader, Rainer; Mittelmeier, Wolfram

    2011-01-01

    Within the first two years after total hip arthroplasty implant-associated infection has become the second most common reason for a revision surgery. Two-stage implant exchange is frequently conducted using temporary spacers made of antibiotic-loaded cement in order to prevent a bacterial colonization on the spacer. Avoiding several disadvantages of cement spacers, a conventional hemi-endoprosthesis was equipped with a copper-containing implant coating for inhibition of bacterial biofilms. In the present paper details of this novel treatment concept are presented including a case report.

  1. Performance of two-stage fan having low-aspect-ratio first-stage rotor blading

    NASA Technical Reports Server (NTRS)

    Urasek, D. C.; Gorrell, W. T.; Cunnan, W. S.

    1979-01-01

    The NASA two stage fan was tested with a low aspect ratio first stage rotor having no midspan dampers. At design speed the fan achieved an adiabatic design efficiency of 0.846, and peak efficiencies for the first stage and rotor of 0.870 and 0.906, respectively. Peak efficiency occurred very close to the stall line. In an attempt to improve stall margin, the fan was retested with circumferentially grooved casing treatment and with a series of stator blade resets. Results showed no improvement in stall margin with casing treatment but increased to 8 percent with stator blade reset.

  2. Two-stage fluidized-bed/cyclonic agglomerating incinerator. Technology spotlight report

    SciTech Connect

    1995-08-01

    The two-stage fluidized-bed/cyclonic agglomerating incinerator combines and improves upon the fluidized-bed, agglomeration/ incineration-technology and the cyclonic-combustion technology developed at Institute of Gas Technolgy (IGT) over many years. The result is a unique and extremely flexible incinerator for solid, liquid, and gaseous wastes. The system can operate over a wide range of conditions and has a destruction and removal efficiency (DRE) greater than 99.99%. Solid inorganic contaminants are contained within aglassy matrix, rendering them benign and suitable for disposal in an ordinary landfill.

  3. Two-stage underwater image restoration based on a physical model

    NASA Astrophysics Data System (ADS)

    Wang, Nan; Qi, Lin; Dong, Junyu; Fan, Hao; Chen, Xingnan; Yu, Hui

    2017-02-01

    Underwater images are blurred due to light scattering and absorption. Image restoration is therefore important in many underwater research and practical tasks. In this paper, we propose an effective two-stage method to restore underwater scene images. Based on an underwater light propagation model, we first remove backscatter by fitting a binary quadratic function. Then we eliminate the forward scattering and non-uniform lighting attenuation using blue-green dark channel prior. The proposed method requires no additional calibration and we show its effectiveness and robustness by restoring images captured under various underwater scenes.

  4. Metamodeling and Optimization of a Blister Copper Two-Stage Production Process

    NASA Astrophysics Data System (ADS)

    Jarosz, Piotr; Kusiak, Jan; Małecki, Stanisław; Morkisz, Paweł; Oprocha, Piotr; Pietrucha, Wojciech; Sztangret, Łukasz

    2016-06-01

    It is often difficult to estimate parameters for a two-stage production process of blister copper (containing 99.4 wt.% of Cu metal) as well as those for most industrial processes with high accuracy, which leads to problems related to process modeling and control. The first objective of this study was to model flash smelting and converting of Cu matte stages using three different techniques: artificial neural networks, support vector machines, and random forests, which utilized noisy technological data. Subsequently, more advanced models were applied to optimize the entire process (which was the second goal of this research). The obtained optimal solution was a Pareto-optimal one because the process consisted of two stages, making the optimization problem a multi-criteria one. A sequential optimization strategy was employed, which aimed for optimal control parameters consecutively for both stages. The obtained optimal output parameters for the first smelting stage were used as input parameters for the second converting stage. Finally, a search for another optimal set of control parameters for the second stage of a Kennecott-Outokumpu process was performed. The optimization process was modeled using a Monte-Carlo method, and both modeling parameters and computed optimal solutions are discussed.

  5. An operational rate control scheme for H.264 with two-stage encoding

    NASA Astrophysics Data System (ADS)

    Kwon, Do-Kyoung; Shen, Mei-Yin; Kuo, C.-C. Jay

    2005-08-01

    An operational rate control (RC) scheme based on two-stage encoding is studied in this research, where frame-layer rate control with a constant bit rate to achieve constant video quality is examined. In the first encoding stage, the R-D optimized mode decision and its associated motion estimation (RDO) as well as DCT/Q, IQ/IDCT and entropy coding are performed for all macroblocks (MBs) for a target frame using an initial quantization parameter (QP), which is the QP of its previous frame. In the second encoding stage, the residual signal from the first stage is encoded using several QP values around the initial QP. Given the target bits and distortion for the current frame, the residual signal is finally encoded using the QP determined by comparing target bits and distortion with actual bits and distortion. To reduce the additional coding complexity of the two-stage encoding, upper and lower bounds around target bits and distortion are employed to reduce the number of encoding required in the second stage. Experimental results are given to show the superior performance of two proposed rate control algorithms, where one targets at the constant bit rate while the other at constant quality.

  6. A two-stage linear discriminant analysis via QR-decomposition.

    PubMed

    Ye, Jieping; Li, Qi

    2005-06-01

    Linear Discriminant Analysis (LDA) is a well-known method for feature extraction and dimension reduction. It has been used widely in many applications involving high-dimensional data, such as image and text classification. An intrinsic limitation of classical LDA is the so-called singularity problems; that is, it fails when all scatter matrices are singular. Many LDA extensions were proposed in the past to overcome the singularity problems. Among these extensions, PCA+LDA, a two-stage method, received relatively more attention. In PCA+LDA, the LDA stage is preceded by an intermediate dimension reduction stage using Principal Component Analysis (PCA). Most previous LDA extensions are computationally expensive, and not scalable, due to the use of Singular Value Decomposition or Generalized Singular Value Decomposition. In this paper, we propose a two-stage LDA method, namely LDA/QR, which aims to overcome the singularity problems of classical LDA, while achieving efficiency and scalability simultaneously. The key difference between LDA/QR and PCA+LDA lies in the first stage, where LDA/QR applies QR decomposition to a small matrix involving the class centroids, while PCA+LDA applies PCA to the total scatter matrix involving all training data points. We further justify the proposed algorithm by showing the relationship among LDA/QR and previous LDA methods. Extensive experiments on face images and text documents are presented to show the effectiveness of the proposed algorithm.

  7. Suppression of sludge formation by two-stage hydrocracking of vacuum residue at high conversion

    SciTech Connect

    Mochida, I.; Zhao, X.; Sakanishi, K. )

    1990-12-01

    This paper reports on hydrocracked products from Arabian light vacuum residue at high conversion into distillate ({gt}50%) that were analyzed in order to reveal how sludge formation was suppressed in the two-stage reaction. Although the asphaltene in the starting residue was highly soluble in the starting maltene in spite of is largest molecular weight, single-stage hydrocracking at a higher temperature of 420{degrees}C increased the aromaticity of the asphaltene through extensive deaklylation and dehydrogenation, leading to sludge formation. In contrast, two-stage hydrocracking at 390{degrees}C--3 h/420{degrees}C--1/h accomplished effective depolymerization of the asphaltene, high conversion being achieved without sludge. The carbon aromaticity (f{sub a}) of the produced asphaltene was maintained rather low, although its amount in the product was much the same regardless of the reaction conditions. The heptane-soluble maltenes in the hydrocracked oils exhibited variable dissolving abilities against the asphaltene according to the content and aromaticity of its aromatic fraction, also influencing sludge formation. Hydrocracking produced paraffins through the hydrogenative deaklylation of long-chain alkylbenzenes, decreasing f{sub a} and the dissolving ability of the hydrocracked maltene.

  8. COMPARISON OF THEORY AND MEASUREMENTS OF A TWO-STAGE LIGHT-GAS GUN

    SciTech Connect

    Levinson, S.; Berry, D.; Pedersen, B.; Bless, S.

    2009-12-28

    A comparison of techniques for obtaining projectile velocity history on a two-stage launcher and discuss gun code accuracy vis-a-vis pressure gauges and the new photonic Doppler velocimetry (PDV) technique is presented. The PDV technique itself is described in a companion paper. The PDV records were differentiated to compute acceleration and, hence, base pressure. Two acceleration episodes are revealed in the data. Base pressure values were compared with measurements from stationary pressure gauges and with predictions of a standard two-stage gun code. The agreement with the pressure gages was satisfactory. Code predictions did not account for the two acceleration stages. However, for the main acceleration episode, the predicted base pressure is in good agreement with the smoothed pressure computed from the PDV record. Both the gauge records and PDV contain short-time pressure spikes which are apparently real. Therefore, use of computed base pressure for projectile design may lead to failures if the projectile is vulnerable to pressure spikes.

  9. Batch (one- and two-stage) production of biodiesel fuel from rapeseed oil.

    PubMed

    Jeong, Gwi-Taek; Park, Don-Hee

    2006-01-01

    Biodiesel fuel is an alternative and renewable energy source, which may help to reduce air pollution, as well as our dependence on petroleum for energy. Several processes have already been developed for the production of biodiesel. Alkali-catalyzed transesterification with short-chain alcohols, for example, generates high yields of methyl esters in short reaction times. In this study, we have evaluated the efficacy of batch (one- and two-stage) transesterification of rapeseed oil in the production of rapeseed methyl ester. The conversion of rapeseed oil exhibited similar reaction patterns and yields in 30- and 1-L reaction systems. Approximately 98% of the rapeseed oil was converted at 400 rpm within 20 min, under the following conditions: 1% (w/w) KOH, 1:10 methanol molar ratio, and at 60 degrees C. In the 30-L, two-stage transesterification process, approx 98.5% of the rapeseed oil was converted at a 1:4.5 molar ratio and 1% (w/w) KOH at 60 degrees C for 30 min (first reaction condition), and at a 1:1 molar ratio and 0.2% (w/w) KOH at 60 degrees C for 30 min (second reaction condition).

  10. Batch (one- and two-stage) production of biodiesel fuel from rapeseed oil.

    PubMed

    Jeong, Gwi-Taek; Park, Don-Hee

    2006-03-01

    Biodiesel fuel is an alternative and renewable energy source, which may help to reduce air pollution, as well as our dependence on petroleum for energy. Several processes have already been developed for the production of biodiesel. Alkali-catalyzed transesterification with short-chain alcohols, for example, generates high yields of methyl esters in short reaction times. In this study, we have evaluated the efficacy of batch (one- and two-stage) transesterification of rapeseed oil in the production of rapeseed methyl ester. The conversion of rapeseed oil exhibited similar reaction patterns and yields in 30- and 1-L reaction systems. Approximately 98% of the rapeseed oil was converted at 400 rpm within 20 min, under the following conditions: 1% (w/w) KOH, 1ratio10 methanol molar ratio, and at 60 degrees C. In the 30-L, two-stage transesterification process, approx 98.5% of the rapeseed oil was converted at a 1ratio4.5 molar ratio and 1% (w/w) KOH at 60 degrees C for 30 min (first reaction condition), and at a 1ratio1 molar ratio and 0.2% (w/w) KOH at 60 degrees C for 30 min (second reaction condition).

  11. Two stage, low temperature, catalyzed fluidized bed incineration with in situ neutralization for radioactive mixed wastes

    SciTech Connect

    Wade, J.F.; Williams, P.M.

    1995-05-17

    A two stage, low temperature, catalyzed fluidized bed incineration process is proving successful at incinerating hazardous wastes containing nuclear material. The process operates at 550{degrees}C and 650{degrees}C in its two stages. Acid gas neutralization takes place in situ using sodium carbonate as a sorbent in the first stage bed. The feed material to the incinerator is hazardous waste-as defined by the Resource Conservation and Recovery Act-mixed with radioactive materials. The radioactive materials are plutonium, uranium, and americium that are byproducts of nuclear weapons production. Despite its low temperature operation, this system successfully destroyed poly-chlorinated biphenyls at a 99.99992% destruction and removal efficiency. Radionuclides and volatile heavy metals leave the fluidized beds and enter the air pollution control system in minimal amounts. Recently collected modeling and experimental data show the process minimizes dioxin and furan production. The report also discusses air pollution, ash solidification, and other data collected from pilot- and demonstration-scale testing. The testing took place at Rocky Flats Environmental Technology Site, a US Department of Energy facility, in the 1970s, 1980s, and 1990s.

  12. On-line monitoring of a two-stage anaerobic digestion process using a BOD analyzer.

    PubMed

    Liu, Jing; Olsson, Gustaf; Mattiasson, Bo

    2004-04-29

    A computer-controlled biochemical oxygen demand (BOD) analyzer has been developed for fast estimation of biochemical oxygen demand (BODst) automatically with the purpose of on-line monitoring of a process for conversion of biomass under field conditions. The instrument was tested by on-line monitoring of the connecting stream between two stages of a two-stage anaerobic process in laboratory scale. In the first stage, hydrolysis of sugar beet leaves and its conversion into volatile fatty acids and other low molecular weight substrates took place. The effluent from the first reactor was used as a feed stream to the second stage, i.e. an anaerobic contact reactor. The feed stream was sampled intermittently, diluted and analyzed by the BOD analyzer automatically in order to estimate the organic loading rate to the reactor. The results from this study demonstrated that the BOD analyzer could be a stand-alone and promising sensor device for rapid on-line monitoring of easily biodegradable organic substances in biological treatment processes.

  13. Aerobic and two-stage anaerobic-aerobic sludge digestion with pure oxygen and air aeration.

    PubMed

    Zupancic, Gregor D; Ros, Milenko

    2008-01-01

    The degradability of excess activated sludge from a wastewater treatment plant was studied. The objective was establishing the degree of degradation using either air or pure oxygen at different temperatures. Sludge treated with pure oxygen was degraded at temperatures from 22 degrees C to 50 degrees C while samples treated with air were degraded between 32 degrees C and 65 degrees C. Using air, sludge is efficiently degraded at 37 degrees C and at 50-55 degrees C. With oxygen, sludge was most effectively degraded at 38 degrees C or at 25-30 degrees C. Two-stage anaerobic-aerobic processes were studied. The first anaerobic stage was always operated for 5 days HRT, and the second stage involved aeration with pure oxygen and an HRT between 5 and 10 days. Under these conditions, there is 53.5% VSS removal and 55.4% COD degradation at 15 days HRT - 5 days anaerobic, 10 days aerobic. Sludge digested with pure oxygen at 25 degrees C in a batch reactor converted 48% of sludge total Kjeldahl nitrogen to nitrate. Addition of an aerobic stage with pure oxygen aeration to the anaerobic digestion enhances ammonium nitrogen removal. In a two-stage anaerobic-aerobic sludge digestion process within 8 days HRT of the aerobic stage, the removal of ammonium nitrogen was 85%.

  14. Two-stage fermentation process for enhanced mannitol production using Candida magnoliae mutant R9.

    PubMed

    Savergave, Laxman S; Gadre, Ramchandra V; Vaidya, Bhalchandra K; Jogdand, Vitthal V

    2013-02-01

    Mutants of Candida magnoliae NCIM 3470 were generated by treatment of ultra-violet radiations, ethyl methyl sulphonate and N-methyl-N'-nitro-N-nitrosoguanidine. Mutants with higher reductase activity were screened by means of 2,3,5-triphenyl tetrazolium chloride agar plate assay. Among the screened mutants, the mutant R9 produced maximum mannitol (i.e. 46 g l(-1)) in liquid fermentation medium containing 250 g l(-1) glucose and hence was selected for further experiments. Preliminary optimization studies were carried out on shake-flask level which increased the mannitol production to 60 g l(-1) in liquid fermentation medium containing 300 g l(-1) glucose. A two-stage fermentation process comprising of growth phase and production phase was employed. During the growth phase, glucose was supplemented and aerobic conditions were maintained. Thereafter, the production phase was initiated by supplementing fructose and switching to anaerobic conditions by discontinuing aeration and decreasing the speed of agitation. The strategy of two-stage fermentation significantly enhanced the production of mannitol up to 240 g l(-1), which is the highest among all fermentative production processes and corresponds to 81 % yield and 4 g l(-1 )h(-1) productivity without formation of any by-product.

  15. Prediction of bio-methane potential and two-stage anaerobic digestion of starfish.

    PubMed

    Kim, Dong-Hoon; Cha, Jaehwan; Lee, Mo-Kwon; Kim, Hyun-Woo; Kim, Mi-Sun

    2013-08-01

    The present work reports the first ever evaluation of the biological CH₄ potential (BMP) of starfish, classified as invasive species. Since starfish contain a large amount of inorganic matter, only the supernatant obtained through grinding and centrifugation was used for BMP test. By applying response surface methodology, the individual and interactive effects of three parameters, inoculum/substrate ratios, substrate concentrations, and buffer capacities on CH₄ production were investigated, and the maximum CH₄ yield of 334 mL CH₄/g COD was estimated. In addition, continuous CH₄ production was attempted using a two-stage (acidogenic sequencing batch reactor+methanogenic up-flow anaerobic sludge blanket reactor (UASBr)) fermentation process. Acidification efficiency was maximized at 2 days of hydraulic retention time with valerate, butyrate, and acetate as main acids, and these were converted to CH₄ with showing 296 mL CH₄/g COD added. Overall, the two-stage fermentation process could convert 44% of organic content in whole starfish to CH₄.

  16. Influence of pressures up to 50bar on two-stage anaerobic digestion.

    PubMed

    Merkle, Wolfgang; Baer, Katharina; Lindner, Jonas; Zielonka, Simon; Ortloff, Felix; Graf, Frank; Kolb, Thomas; Jungbluth, Thomas; Lemmer, Andreas

    2017-05-01

    The concept of pressurized two-stage anaerobic digestion integrates biogas production, purification and pressure boosting within one process. The produced methane-rich biogas can be fed into gas grids with considerably less purification effort. To investigate biogas production under high pressures up to 50bar, a lab scale two-stage anaerobic digestion system was constructed including one continuously operated pressurized methane reactor. This investigation examined the effects of different operating pressures in methane reactor (10, 25, 50bar) on biogas quantity and quality, pH value and process stability. By increasing operating pressures in methane reactor, the pH value decreased from 6.65 at 10bar to 6.55 at 50bar. Simultaneously, methane content increased from 79.08% at 10bar to 90.45% at 50bar. The results show that methane reactors can be operated up to 50bar pressure continuously representing a viable alternative to commonly used gas upgrading methods because of reduced purification effort.

  17. The feasibility of using a two-stage autotrophic nitrogen removal process to treat sewage.

    PubMed

    Ma, Bin; Zhang, Shujun; Zhang, Liang; Yi, Peng; Wang, Junmin; Wang, Shuying; Peng, Yongzhen

    2011-09-01

    The feasibility of using a two-stage autotrophic nitrogen removal process to treat sewage was examined in this study. The obtained results showed that total nitrogen (TN) could be efficiently removed by 88.38% when influent TN and chemical oxygen demand (COD) were 45.87 and 44.40 mg/L, respectively. In the first stage, nitritation was instantly achieved by the bioaugmentation strategy, and can be maintained under limited oxygen condition (below 0.2mg/L). The ratio of nitrite to ammonium in the effluent of the nitritation reactor can be controlled at approximate 1.0 by adjusting aeration rate. In the second stage, anammox was realized in the upflow anaerobic sludge blanket (UASB) reactor, where the total nitrogen removal rate was 0.40 kg Nm(-3)d(-1) under limited-substrate condition. Therefore, the organic matter in sewage can be firstly concentrated in biomass which could generate biogas (energy). Then, nitrogen in sewage could be removed in a two-stage autotrophic nitrogen removal process.

  18. Performance of two-stage vegetable waste anaerobic digestion depending on varying recirculation rates.

    PubMed

    Zuo, Zhuang; Wu, Shubiao; Zhang, Wanqin; Dong, Renjie

    2014-06-01

    Vegetable waste, which characterized by high moisture content, was evaluated as a substrate for biogas production. The effects of recirculation rate (RR) on the performance of two-stage anaerobic digestion were investigated. The system was operated at an organic loading rate of 1.7 g VS/L/d with varying RRs (0, 0.6, 1, and 1.4). Results demonstrated that volumetric biogas production rates in acidogenic reactor increased from approximately 0.2 7 L/L/d to 0.97 L/L/d, when pH is increased from approximately 5.1 to 6.7. These indicate that recirculation of alkaline effluent from the methanogenic reactor helps create a favorable condition for biogas production in the acidogenic reactor. The decrease in chemical oxygen demand (COD) concentrations from approximately 21,000 mg/L to 6800 mg/L was also observed in the acidogenic reactor. This condition may be attributed to dilution under recirculation. The dynamics between hydrolysis and methanogenesis under recirculation indicated that mass transfer capacity between two-stage reactors improved.

  19. Two-Stage Orthogonal Least Squares Methods for Neural Network Construction.

    PubMed

    Zhang, Long; Li, Kang; Bai, Er-Wei; Irwin, George W

    2015-08-01

    A number of neural networks can be formulated as the linear-in-the-parameters models. Training such networks can be transformed to a model selection problem where a compact model is selected from all the candidates using subset selection algorithms. Forward selection methods are popular fast subset selection approaches. However, they may only produce suboptimal models and can be trapped into a local minimum. More recently, a two-stage fast recursive algorithm (TSFRA) combining forward selection and backward model refinement has been proposed to improve the compactness and generalization performance of the model. This paper proposes unified two-stage orthogonal least squares methods instead of the fast recursive-based methods. In contrast to the TSFRA, this paper derives a new simplified relationship between the forward and the backward stages to avoid repetitive computations using the inherent orthogonal properties of the least squares methods. Furthermore, a new term exchanging scheme for backward model refinement is introduced to reduce computational demand. Finally, given the error reduction ratio criterion, effective and efficient forward and backward subset selection procedures are proposed. Extensive examples are presented to demonstrate the improved model compactness constructed by the proposed technique in comparison with some popular methods.

  20. Pilot-scale two-stage process: a combination of acidogenic hydrogenesis and methanogenesis.

    PubMed

    Han, S K; Kim, S H; Kim, H W; Shin, H S

    2005-01-01

    This study was performed to optimize both acidogenic hydrogenesis and methanogenesis, and then to develop a pilot-scale two-stage process producing not only CH4 but also H2. Firstly, acidogenic hydrogenesis of food waste was examined in pilot-scale leaching-bed reactors using dilution rate (D) as a tool to improve the environmental conditions. The maximum efficiency of 71.4% was obtained by adjusting D from 4.5 to 2.5 d(-1) depending on the state of degradation. Secondly, the wastewater from acidogenic hydrogenesis was converted to CH4 in a pilot-scale UASB reactor. The COD removal efficiency exceeded 95% up to the loading rates of 13.1 g COD/Ld, which corresponded to HRT of 0.25 d (6 h). Lastly, a pilot-scale two-stage process was devised based on a combination of acidogenic hydrogenesis and methanogenesis. Over 120 days, the pilot-scale process resulted in large VS reduction of 70.9% at the high loading rate of 12.5 kg VS/m3/d in a short SRT of 8 days.

  1. Evaluation of a two-stage biofilter for treatment of POTW waste air

    SciTech Connect

    Chitwood, D.E.; Devinny, J.S.; Reynolds, F.E. Jr.

    1999-09-30

    Recent efforts have been made to reduce releases of air toxics and smog precursors from wastewater treatment plants. Hydrogen sulfide is commonly the primary odor and is an important target for removal. Its oxidation, however, generates sulfuric acid and sometimes elemental sulfur, which can create substantial operational problems for biofilters. Declining pH may inhibit the organisms that degrade compounds other than hydrogen sulfide and may hasten aging of organic biofilter media. A two-stage biofilter has been designed and installed at the Ohio Valley Sanitary District wastewater treatment plant. The first stage is an enclosed system with a medium of small, inert, porous stones. It is called an acid gas biofilter. The second stage is a section of a traditional open biofilter filled with wood chips. The acid gas biofilter effectively removed H{sub 2}S and volatile organic compounds while causing much lower headloss than traditional biofilters. However, considerable flow heterogeneity in both the acid gas biofilter and the wood chip biofilter was observed. The two-stage system presumably will have a longer bed life because the first stage bed is inert and because the second stage is protected from acidification by removal of H{sub 2}S in the first stage.

  2. A two-stage series diode for intense large-area moderate pulsed X rays production.

    PubMed

    Lai, Dingguo; Qiu, Mengtong; Xu, Qifu; Su, Zhaofeng; Li, Mo; Ren, Shuqing; Huang, Zhongliang

    2017-01-01

    This paper presents a method for moderate pulsed X rays produced by a series diode, which can be driven by high voltage pulse to generate intense large-area uniform sub-100-keV X rays. A two stage series diode was designed for Flash-II accelerator and experimentally investigated. A compact support system of floating converter/cathode was invented, the extra cathode is floating electrically and mechanically, by withdrawing three support pins several milliseconds before a diode electrical pulse. A double ring cathode was developed to improve the surface electric field and emission stability. The cathode radii and diode separation gap were optimized to enhance the uniformity of X rays and coincidence of the two diode voltages based on the simulation and theoretical calculation. The experimental results show that the two stage series diode can work stably under 700 kV and 300 kA, the average energy of X rays is 86 keV, and the dose is about 296 rad(Si) over 615 cm(2) area with uniformity 2:1 at 5 cm from the last converter. Compared with the single diode, the average X rays' energy reduces from 132 keV to 88 keV, and the proportion of sub-100-keV photons increases from 39% to 69%.

  3. A two-stage series diode for intense large-area moderate pulsed X rays production

    NASA Astrophysics Data System (ADS)

    Lai, Dingguo; Qiu, Mengtong; Xu, Qifu; Su, Zhaofeng; Li, Mo; Ren, Shuqing; Huang, Zhongliang

    2017-01-01

    This paper presents a method for moderate pulsed X rays produced by a series diode, which can be driven by high voltage pulse to generate intense large-area uniform sub-100-keV X rays. A two stage series diode was designed for Flash-II accelerator and experimentally investigated. A compact support system of floating converter/cathode was invented, the extra cathode is floating electrically and mechanically, by withdrawing three support pins several milliseconds before a diode electrical pulse. A double ring cathode was developed to improve the surface electric field and emission stability. The cathode radii and diode separation gap were optimized to enhance the uniformity of X rays and coincidence of the two diode voltages based on the simulation and theoretical calculation. The experimental results show that the two stage series diode can work stably under 700 kV and 300 kA, the average energy of X rays is 86 keV, and the dose is about 296 rad(Si) over 615 cm2 area with uniformity 2:1 at 5 cm from the last converter. Compared with the single diode, the average X rays' energy reduces from 132 keV to 88 keV, and the proportion of sub-100-keV photons increases from 39% to 69%.

  4. Numerical simulation and analysis of the flow in a two-staged axial fan

    NASA Astrophysics Data System (ADS)

    Xu, J. Q.; Dou, H. S.; Jia, H. X.; Chen, X. P.; Wei, Y. K.; Dong, M. W.

    2016-05-01

    In this paper, numerical simulation was performed for the internal three-dimensional turbulent flow field in the two-stage axial fan using steady three-dimensional in-compressible Navier-Stokes equations coupled with the Realizable turbulent model. The numerical simulation results of the steady analysis were combined with the flow characteristics of two- staged axial fan, the influence of the mutual effect between the blade and the vane on the flow of the two inter-stages was analyzed emphatically. This paper studied how the flow field distribution in inter-stage is influenced by the wake interaction and potential flow interaction of mutual effect in the impeller-vane inter-stage and the vane-impeller inter-stage. The results showed that: Relatively, wake interaction has an advantage over potential flow interaction in the impeller-vane inter-stage; potential flow interaction has an advantage over wake interaction in the vane-impeller inter-stage. In other words, distribution of flow field in the two interstages is determined by the rotating component.

  5. An integrated two-stage support vector machine approach to forecast inundation maps during typhoons

    NASA Astrophysics Data System (ADS)

    Jhong, Bing-Chen; Wang, Jhih-Huang; Lin, Gwo-Fong

    2017-04-01

    During typhoons, accurate forecasts of hourly inundation depths are essential for inundation warning and mitigation. Due to the lack of observed data of inundation maps, sufficient observed data are not available for developing inundation forecasting models. In this paper, the inundation depths, which are simulated and validated by a physically based two-dimensional model (FLO-2D), are used as a database for inundation forecasting. A two-stage inundation forecasting approach based on Support Vector Machine (SVM) is proposed to yield 1- to 6-h lead-time inundation maps during typhoons. In the first stage (point forecasting), the proposed approach not only considers the rainfall intensity and inundation depth as model input but also simultaneously considers cumulative rainfall and forecasted inundation depths. In the second stage (spatial expansion), the geographic information of inundation grids and the inundation forecasts of reference points are used to yield inundation maps. The results clearly indicate that the proposed approach effectively improves the forecasting performance and decreases the negative impact of increasing forecast lead time. Moreover, the proposed approach is capable of providing accurate inundation maps for 1- to 6-h lead times. In conclusion, the proposed two-stage forecasting approach is suitable and useful for improving the inundation forecasting during typhoons, especially for long lead times.

  6. Two-stage high temperature sludge gasification using the waste heat from hot blast furnace slags.

    PubMed

    Sun, Yongqi; Zhang, Zuotai; Liu, Lili; Wang, Xidong

    2015-12-01

    Nowadays, disposal of sewage sludge from wastewater treatment plants and recovery of waste heat from steel industry, become two important environmental issues and to integrate these two problems, a two-stage high temperature sludge gasification approach was investigated using the waste heat in hot slags herein. The whole process was divided into two stages, i.e., the low temperature sludge pyrolysis at ⩽ 900°C in argon agent and the high temperature char gasification at ⩾ 900°C in CO2 agent, during which the heat required was supplied by hot slags in different temperature ranges. Both the thermodynamic and kinetic mechanisms were identified and it was indicated that an Avrami-Erofeev model could best interpret the stage of char gasification. Furthermore, a schematic concept of this strategy was portrayed, based on which the potential CO yield and CO2 emission reduction achieved in China could be ∼1.92∗10(9)m(3) and 1.93∗10(6)t, respectively.

  7. Biological hydrogen and methane production from bagasse bioethanol fermentation residues using a two-stage bioprocess.

    PubMed

    Cheng, Hai-Hsuan; Whang, Liang-Ming; Chung, Man-Chien; Chan, Kun-Chi

    2016-06-01

    This study investigated the recovery of H2 and CH4 from bagasse bioethanol fermentation residues (bagasse BEFR) using a two-stage bioprocess. In the hydrogen fermentation bioreactor (HFB), carbohydrate removal efficiency was maintained at 82-93% and the highest hydrogen yield was 8.24mL/gCOD at volumetric loading rate (VLR) of 80kgCOD/m(3)/day. The results indicated a positive correlation between hydrogen yield and butyrate-to-acetate ratio, which might be due to the mechanisms of lactate/acetate utilization for hydrogen production and acetogenesis occurring in the HFB. Remaining volatile fatty acids and alcohols in the HFB effluent were further utilized for methane production in methane fermentation bioreactor (MFB), in which the highest methane yield of 345.2mL/gCOD was attained at VLR of 2.5kgCOD/m(3)/day. Overall, the two-stage bioprocess achieved a maximum COD removal of 81% from bagasse BEFR, and converted 0.3% and 72.8% of COD in the forms of H2 and CH4, respectively.

  8. Estimating accuracy of land-cover composition from two-stage cluster sampling

    USGS Publications Warehouse

    Stehman, S.V.; Wickham, J.D.; Fattorini, L.; Wade, T.D.; Baffetta, F.; Smith, J.H.

    2009-01-01

    Land-cover maps are often used to compute land-cover composition (i.e., the proportion or percent of area covered by each class), for each unit in a spatial partition of the region mapped. We derive design-based estimators of mean deviation (MD), mean absolute deviation (MAD), root mean square error (RMSE), and correlation (CORR) to quantify accuracy of land-cover composition for a general two-stage cluster sampling design, and for the special case of simple random sampling without replacement (SRSWOR) at each stage. The bias of the estimators for the two-stage SRSWOR design is evaluated via a simulation study. The estimators of RMSE and CORR have small bias except when sample size is small and the land-cover class is rare. The estimator of MAD is biased for both rare and common land-cover classes except when sample size is large. A general recommendation is that rare land-cover classes require large sample sizes to ensure that the accuracy estimators have small bias. ?? 2009 Elsevier Inc.

  9. Optimal adaptive two-stage designs for early phase II clinical trials.

    PubMed

    Shan, Guogen; Wilding, Gregory E; Hutson, Alan D; Gerstenberger, Shawn

    2016-04-15

    Simon's optimal two-stage design has been widely used in early phase clinical trials for Oncology and AIDS studies with binary endpoints. With this approach, the second-stage sample size is fixed when the trial passes the first stage with sufficient activity. Adaptive designs, such as those due to Banerjee and Tsiatis (2006) and Englert and Kieser (2013), are flexible in the sense that the second-stage sample size depends on the response from the first stage, and these designs are often seen to reduce the expected sample size under the null hypothesis as compared with Simon's approach. An unappealing trait of the existing designs is that they are not associated with a second-stage sample size, which is a non-increasing function of the first-stage response rate. In this paper, an efficient intelligent process, the branch-and-bound algorithm, is used in extensively searching for the optimal adaptive design with the smallest expected sample size under the null, while the type I and II error rates are maintained and the aforementioned monotonicity characteristic is respected. The proposed optimal design is observed to have smaller expected sample sizes compared to Simon's optimal design, and the maximum total sample size of the proposed adaptive design is very close to that from Simon's method. The proposed optimal adaptive two-stage design is recommended for use in practice to improve the flexibility and efficiency of early phase therapeutic development.

  10. Development of a Two-Stage Microalgae Dewatering Process – A Life Cycle Assessment Approach

    PubMed Central

    Soomro, Rizwan R.; Zeng, Xianhai; Lu, Yinghua; Lin, Lu; Danquah, Michael K.

    2016-01-01

    Even though microalgal biomass is leading the third generation biofuel research, significant effort is required to establish an economically viable commercial-scale microalgal biofuel production system. Whilst a significant amount of work has been reported on large-scale cultivation of microalgae using photo-bioreactors and pond systems, research focus on establishing high performance downstream dewatering operations for large-scale processing under optimal economy is limited. The enormous amount of energy and associated cost required for dewatering large-volume microalgal cultures has been the primary hindrance to the development of the needed biomass quantity for industrial-scale microalgal biofuels production. The extremely dilute nature of large-volume microalgal suspension and the small size of microalgae cells in suspension create a significant processing cost during dewatering and this has raised major concerns towards the economic success of commercial-scale microalgal biofuel production as an alternative to conventional petroleum fuels. This article reports an effective framework to assess the performance of different dewatering technologies as the basis to establish an effective two-stage dewatering system. Bioflocculation coupled with tangential flow filtration (TFF) emerged a promising technique with total energy input of 0.041 kWh, 0.05 kg CO2 emissions and a cost of $ 0.0043 for producing 1 kg of microalgae biomass. A streamlined process for operational analysis of two-stage microalgae dewatering technique, encompassing energy input, carbon dioxide emission, and process cost, is presented. PMID:26904075

  11. Development and optimization of a two-stage gasifier for heat and power production

    NASA Astrophysics Data System (ADS)

    Kosov, V. V.; Zaichenko, V. M.

    2016-11-01

    The major methods of biomass thermal conversion are combustion in excess oxygen, gasification in reduced oxygen, and pyrolysis in the absence of oxygen. The end products of these methods are heat, gas, liquid and solid fuels. From the point of view of energy production, none of these methods can be considered optimal. A two-stage thermal conversion of biomass based on pyrolysis as the first stage and pyrolysis products cracking as the second stage can be considered the optimal method for energy production that allows obtaining synthesis gas consisting of hydrogen and carbon monoxide and not containing liquid or solid particles. On the base of the two stage cracking technology, there was designed an experimental power plant of electric power up to 50 kW. The power plant consists of a thermal conversion module and a gas engine power generator adapted for operation on syngas. Purposes of the work were determination of an optimal operation temperature of the thermal conversion module and an optimal mass ratio of processed biomass and charcoal in cracking chamber of the thermal conversion module. Experiments on the pyrolysis products cracking at various temperatures show that the optimum cracking temperature is equal to 1000 °C. From the results of measuring the volume of gas produced in different mass ratios of charcoal and wood biomass processed, it follows that the maximum volume of the gas in the range of the mass ratio equal to 0.5-0.6.

  12. Two-stage estimation for multivariate recurrent event data with a dependent terminal event.

    PubMed

    Chen, Chyong-Mei; Chuang, Ya-Wen; Shen, Pao-Sheng

    2015-03-01

    Recurrent event data arise in longitudinal follow-up studies, where each subject may experience the same type of events repeatedly. The work in this article is motivated by the data from a study of repeated peritonitis for patients on peritoneal dialysis. Due to the aspects of medicine and cost, the peritonitis cases were classified into two types: Gram-positive and non-Gram-positive peritonitis. Further, since the death and hemodialysis therapy preclude the occurrence of recurrent events, we face multivariate recurrent event data with a dependent terminal event. We propose a flexible marginal model, which has three characteristics: first, we assume marginal proportional hazard and proportional rates models for terminal event time and recurrent event processes, respectively; second, the inter-recurrences dependence and the correlation between the multivariate recurrent event processes and terminal event time are modeled through three multiplicative frailties corresponding to the specified marginal models; third, the rate model with frailties for recurrent events is specified only on the time before the terminal event. We propose a two-stage estimation procedure for estimating unknown parameters. We also establish the consistency of the two-stage estimator. Simulation studies show that the proposed approach is appropriate for practical use. The methodology is applied to the peritonitis cohort data that motivated this study.

  13. Two-stage path planning approach for solving multiple spacecraft reconfiguration maneuvers

    NASA Astrophysics Data System (ADS)

    Aoude, Georges S.; How, Jonathan P.; Garcia, Ian M.

    2008-12-01

    The paper presents a two-stage approach for designing optimal reconfiguration maneuvers for multiple spacecraft in close proximity. These maneuvers involve well-coordinated and highly-coupled motions of the entire fleet of spacecraft while satisfying an arbitrary number of constraints. This problem is complicated by the nonlinearity of the attitude dynamics, the non-convexity of some of the constraints, and the coupling that exists in some of the constraints between the positions and attitudes of all spacecraft. While there has been significant research to solve for the translation and/or rotation trajectories for the multiple spacecraft reconfiguration problem, the approach presented in this paper is more general and on a larger scale than the problems considered previously. The essential feature of the solution approach is the separation into two stages, the first using a simplified planning approach to obtain a feasible solution, which is then significantly improved using a smoothing stage. The first stage is solved using a bidirectional Rapidly-exploring Random Tree (RRT) planner. Then the second step optimizes the trajectories by solving an optimal control problem using the Gauss pseudospectral method (GPM). Several examples are presented to demonstrate the effectiveness of the approach for designing spacecraft reconfiguration maneuvers.

  14. Two-stage k-sample designs for the ordered alternative problem.

    PubMed

    Shan, Guogen; Hutson, Alan D; Wilding, Gregory E

    2012-01-01

    In preclinical studies and clinical dose-ranging trials, the Jonckheere-Terpstra test is widely used in the assessment of dose-response relationships. Hewett and Spurrier (1979) presented a two-stage analog of the test in the context of large sample sizes. In this paper, we propose an exact test based on Simon's minimax and optimal design criteria originally used in one-arm phase II designs based on binary endpoints. The convergence rate of the joint distribution of the first and second stage test statistics to the limiting distribution is studied, and design parameters are provided for a variety of assumed alternatives. The behavior of the test is also examined in the presence of ties, and the proposed designs are illustrated through application in the planning of a hypercholesterolemia clinical trial. The minimax and optimal two-stage procedures are shown to be preferable as compared with the one-stage procedure because of the associated reduction in expected sample size for given error constraints.

  15. Design of adaptive two-stage double-arm clinical trials for dichotomous variables.

    PubMed

    Jiang, Zhiwei; Xue, Fubo; Li, Chanjuan; Wang, Ling; Cai, Hongwei; Zhang, Chunmao; Xia, Jielai

    2010-05-01

    It is well known that flexibility is one of the major advantages of an adaptive two-stage design, and the intended adaptation should be as preplanned as possible to maintain the integrity of the clinical trial. The design of adaptive two-stage double-arm clinical trials for dichotomous variables was proposed by simulation and forecasting procedure at the planning stage. To further ensure the integrity of the clinical trial, the sample size scheme for each scenario, which was supposed to be based on the first stage, was provided in the protocol by Monte Carlo simulation. In addition, the study parameters were determined by comparing the assessment indexes such as total sample size, expected sample size and the test power at the first stage. Furthermore, Fisher's combination test and pooled data analysis were considered and compared through the simulation. The latter, which has the larger overall power and the better overall type I error control, with the same sample size was adopted for further simulation and statistical analysis in the clinical trial.

  16. One-stage and two-stage designs for phase II clinical trials with survival endpoints.

    PubMed

    Whitehead, John

    2014-09-28

    This work is motivated by trials in rapidly lethal cancers or cancers for which measuring shrinkage of tumours is infeasible. In either case, traditional phase II designs focussing on tumour response are unsuitable. Usually, tumour response is considered as a substitute for the more relevant but longer-term endpoint of death. In rapidly lethal cancers such as pancreatic cancer, there is no need to use a surrogate, as the definitive endpoint is (sadly) available so soon. In uveal cancer, there is no counterpart to tumour response, and so, mortality is the only realistic response available. Cytostatic cancer treatments do not seek to kill tumours, but to mitigate their effects. Trials of such therapy might also be based on survival times to death or progression, rather than on tumour shrinkage. Phase II oncology trials are often conducted with all study patients receiving the experimental therapy, and this approach is considered here. Simple extensions of one-stage and two-stage designs based on binary responses are presented. Outcomes based on survival past a small number of landmark times are considered: here, the case of three such times is explored in examples. This approach allows exact calculations to be made for both design and analysis purposes. Simulations presented here show that calculations based on normal approximations can lead to loss of power when sample sizes are small. Two-stage versions of the procedure are also suggested.

  17. Rules and mechanisms for efficient two-stage learning in neural circuits.

    PubMed

    Teşileanu, Tiberiu; Ölveczky, Bence; Balasubramanian, Vijay

    2017-04-04

    Trial-and-error learning requires evaluating variable actions and reinforcing successful variants. In songbirds, vocal exploration is induced by LMAN, the output of a basal ganglia-related circuit that also contributes a corrective bias to the vocal output. This bias is gradually consolidated in RA, a motor cortex analogue downstream of LMAN. We develop a new model of such two-stage learning. Using stochastic gradient descent, we derive how the activity in 'tutor' circuits (e.g., LMAN) should match plasticity mechanisms in 'student' circuits (e.g., RA) to achieve efficient learning. We further describe a reinforcement learning framework through which the tutor can build its teaching signal. We show that mismatches between the tutor signal and the plasticity mechanism can impair learning. Applied to birdsong, our results predict the temporal structure of the corrective bias from LMAN given a plasticity rule in RA. Our framework can be applied predictively to other paired brain areas showing two-stage learning.

  18. Two-stage, low noise advanced technology fan. 5: Acoustic final report

    NASA Technical Reports Server (NTRS)

    Sofrin, T. G.; Riloff, N., Jr.

    1975-01-01

    The NASA Q2S(quiet two-stage) fan is a 0.836m (32.9 in.) diameter model of the STF 433 engine fan, selected in a 1972 study for an Advanced Technology Transport (ATT) airplane. Noise-control features include: low tip speed, moderate stage pressure rise, large blade-vane spacings, no inlet guide vanes, and optimum blade and vane numbers. Tests were run on the baseline Q2S fan with standard inlet and discharge ducts. Further tests were made of a translating centerbody sonic inlet device and treated discharge ducts. Results were scaled to JT8D and JT3D engine fan size for comparison with current two-stage fans, and were also scaled to STF 433 fan size to compare calculated ATT flyover noise with FAR 36 limits. Baseline Q2S results scaled to JT8D and JT3D engine fan sizes showed substantial noise reductions. Calculated unsuppressed baseline ATT flyovers averaged about 2.5 EPNdB below FAR 36 limits. Using measured sonic inlet results, scaled baseline Q2S fan results, and calculated attenuations for a 1975 technology duct liner, projected flyover noise calculations for the ATT averaged about FAR 36 limits minus 10 EPNdB. Advances in suppression technology required to meet the 1985 goal of FAR 36 limits minus 20 EPNdB are discussed.

  19. Investigation of gas stripping and pervaporation for improved feasibility of two-stage butanol production process.

    PubMed

    Setlhaku, Mpho; Heitmann, Sebastian; Górak, Andrzej; Wichmann, Rolf

    2013-05-01

    Gas stripping and pervaporation are investigated for butanol recovery in a two-stage acetone-butanol-ethanol (ABE) fermentation process. The first stage is operated in a continuous mode and the second stage as a fed-batch. Gas stripping coupled to the second stage and operated intermittently enabled additional glucose feeding in the second stage and up to 59 g/L butanol and 73 g/L total ABE solvents in the condensate. Concentration of 167 g/L butanol and 269 g/L ABE in the permeate was measured in ex situ pervaporation experiments using a PDMS membrane at temperature of 37 °C and pressure of 10mbars. The "operating window" tool is introduced to evaluate the feasibility of the existing ABE fermentations operated as continuous with cell recycle, as two-stages, with biomass immobilization or with integrated product removal. This tool enables the identification of the most favorable process configuration, which is the combination of cell immobilization and integrated product removal.

  20. Occurrence of two-stage hardening in C-Mn steel wire rods containing pearlitic microstructure

    NASA Astrophysics Data System (ADS)

    Singh, Balbir; Sahoo, Gadadhar; Saxena, Atul

    2016-09-01

    The 8 and 10 mm diameter wire rods intended for use as concrete reinforcement were produced/ hot rolled from C-Mn steel chemistry containing various elements within the range of C:0.55-0.65, Mn:0.85-1.50, Si:0.05-0.09, S:0.04 max, P:0.04 max and N:0.006 max wt%. Depending upon the C and Mn contents the product attained pearlitic microstructure in the range of 85-93% with balance amount of polygonal ferrite transformed at prior austenite grain boundaries. The pearlitic microstructure in the wire rods helped in achieving yield strength, tensile strength, total elongation and reduction in area values within the range of 422-515 MPa, 790-950 MPa, 22-15% and 45-35%, respectively. On analyzing the tensile results it was revealed that the material experienced hardening in two stages separable by a knee strain value of about 0.05. The occurrence of two stage hardening thus in the steel with hardening coefficients of 0.26 and 0.09 could be demonstrated with the help of derived relationships existed between flow stress and the strain.

  1. A two-stage broadcast message propagation model in social networks

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Cheng, Shun-Jun

    2016-11-01

    Message propagation in social networks is becoming a popular topic in complex networks. One of the message types in social networks is called broadcast message. It refers to a type of message which has a unique and unknown destination for the publisher, such as 'lost and found'. Its propagation always has two stages. Due to this feature, rumor propagation model and epidemic propagation model have difficulty in describing this message's propagation accurately. In this paper, an improved two-stage susceptible-infected-removed model is proposed. We come up with the concept of the first forwarding probability and the second forwarding probability. Another part of our work is figuring out the influence to the successful message transmission chance in each level resulting from multiple reasons, including the topology of the network, the receiving probability, the first stage forwarding probability, the second stage forwarding probability as well as the length of the shortest path between the publisher and the relevant destination. The proposed model has been simulated on real networks and the results proved the model's effectiveness.

  2. Study on a high capacity two-stage free piston Stirling cryocooler working around 30 K

    NASA Astrophysics Data System (ADS)

    Wang, Xiaotao; Zhu, Jian; Chen, Shuai; Dai, Wei; Li, Ke; Pang, Xiaomin; Yu, Guoyao; Luo, Ercang

    2016-12-01

    This paper presents a two-stage high-capacity free-piston Stirling cryocooler driven by a linear compressor to meet the requirement of the high temperature superconductor (HTS) motor applications. The cryocooler system comprises a single piston linear compressor, a two-stage free piston Stirling cryocooler and a passive oscillator. A single stepped displacer configuration was adopted. A numerical model based on the thermoacoustic theory was used to optimize the system operating and structure parameters. Distributions of pressure wave, phase differences between the pressure wave and the volume flow rate and different energy flows are presented for a better understanding of the system. Some characterizing experimental results are presented. Thus far, the cryocooler has reached a lowest cold-head temperature of 27.6 K and achieved a cooling power of 78 W at 40 K with an input electric power of 3.2 kW, which indicates a relative Carnot efficiency of 14.8%. When the cold-head temperature increased to 77 K, the cooling power reached 284 W with a relative Carnot efficiency of 25.9%. The influences of different parameters such as mean pressure, input electric power and cold-head temperature are also investigated.

  3. Two-Stage Single-Compartment Models to Evaluate Dissolution in the Lower Intestine.

    PubMed

    Markopoulos, Constantinos; Vertzoni, Maria; Symillides, Mira; Kesisoglou, Filippos; Reppas, Christos

    2015-09-01

    The purpose was to propose two-stage single-compartment models for evaluating dissolution characteristics in distal ileum and ascending colon, under conditions simulating the bioavailability and bioequivalence studies in fasted and fed state by using the mini-paddle and the compendial flow-through apparatus (closed-loop mode). Immediate release products of two highly dosed active pharmaceutical ingredients (APIs), sulfasalazine and L-870,810, and one mesalamine colon targeting product were used for evaluating their usefulness. Change of medium composition simulating the conditions in distal ileum (SIFileum ) to a medium simulating the conditions in ascending colon in fasted state and in fed state was achieved by adding an appropriate solution in SIFileum . Data with immediate release products suggest that dissolution in lower intestine is substantially different than in upper intestine and is affected by regional pH differences > type/intensity of fluid convection > differences in concentration of other luminal components. Asacol® (400 mg/tab) was more sensitive to type/intensity of fluid convection. In all the cases, data were in line with available human data. Two-stage single-compartment models may be useful for the evaluation of dissolution in lower intestine. The impact of type/intensity of fluid convection and viscosity of media on luminal performance of other APIs and drug products requires further exploration.

  4. Development of a Two-Stage Microalgae Dewatering Process - A Life Cycle Assessment Approach.

    PubMed

    Soomro, Rizwan R; Ndikubwimana, Theoneste; Zeng, Xianhai; Lu, Yinghua; Lin, Lu; Danquah, Michael K

    2016-01-01

    Even though microalgal biomass is leading the third generation biofuel research, significant effort is required to establish an economically viable commercial-scale microalgal biofuel production system. Whilst a significant amount of work has been reported on large-scale cultivation of microalgae using photo-bioreactors and pond systems, research focus on establishing high performance downstream dewatering operations for large-scale processing under optimal economy is limited. The enormous amount of energy and associated cost required for dewatering large-volume microalgal cultures has been the primary hindrance to the development of the needed biomass quantity for industrial-scale microalgal biofuels production. The extremely dilute nature of large-volume microalgal suspension and the small size of microalgae cells in suspension create a significant processing cost during dewatering and this has raised major concerns towards the economic success of commercial-scale microalgal biofuel production as an alternative to conventional petroleum fuels. This article reports an effective framework to assess the performance of different dewatering technologies as the basis to establish an effective two-stage dewatering system. Bioflocculation coupled with tangential flow filtration (TFF) emerged a promising technique with total energy input of 0.041 kWh, 0.05 kg CO2 emissions and a cost of $ 0.0043 for producing 1 kg of microalgae biomass. A streamlined process for operational analysis of two-stage microalgae dewatering technique, encompassing energy input, carbon dioxide emission, and process cost, is presented.

  5. Two-stage effects of awareness cascade on epidemic spreading in multiplex networks

    NASA Astrophysics Data System (ADS)

    Guo, Quantong; Jiang, Xin; Lei, Yanjun; Li, Meng; Ma, Yifang; Zheng, Zhiming

    2015-01-01

    Human awareness plays an important role in the spread of infectious diseases and the control of propagation patterns. The dynamic process with human awareness is called awareness cascade, during which individuals exhibit herd-like behavior because they are making decisions based on the actions of other individuals [Borge-Holthoefer et al., J. Complex Networks 1, 3 (2013), 10.1093/comnet/cnt006]. In this paper, to investigate the epidemic spreading with awareness cascade, we propose a local awareness controlled contagion spreading model on multiplex networks. By theoretical analysis using a microscopic Markov chain approach and numerical simulations, we find the emergence of an abrupt transition of epidemic threshold βc with the local awareness ratio α approximating 0.5 , which induces two-stage effects on epidemic threshold and the final epidemic size. These findings indicate that the increase of α can accelerate the outbreak of epidemics. Furthermore, a simple 1D lattice model is investigated to illustrate the two-stage-like sharp transition at αc≈0.5 . The results can give us a better understanding of why some epidemics cannot break out in reality and also provide a potential access to suppressing and controlling the awareness cascading systems.

  6. Two-stage method of estimation for general linear growth curve models.

    PubMed

    Stukel, T A; Demidenko, E

    1997-06-01

    We extend the linear random-effects growth curve model (REGCM) (Laird and Ware, 1982, Biometrics 38, 963-974) to study the effects of population covariates on one or more characteristics of the growth curve when the characteristics are expressed as linear combinations of the growth curve parameters. This definition includes the actual growth curve parameters (the usual model) or any subset of these parameters. Such an analysis would be cumbersome using standard growth curve methods because it would require reparameterization of the original growth curve. We implement a two-stage method of estimation based on the two-stage growth curve model used to describe the response. The resulting generalized least squares (GLS) estimator for the population parameters is consistent, asymptotically efficient, and multivariate normal when the number of individuals is large. It is also robust to model misspecification in terms of bias and efficiency of the parameter estimates compared to maximum likelihood with the usual REGCM. We apply the method to a study of factors affecting the growth rate of salmonellae in a cubic growth model, a characteristic that cannot be analyzed easily using standard techniques.

  7. Final Report on Two-Stage Fast Spectrum Fuel Cycle Options

    SciTech Connect

    Yang, Won Sik; Lin, C. S.; Hader, J. S.; Park, T. K.; Deng, P.; Yang, G.; Jung, Y. S.; Kim, T. K.; Stauff, N. E.

    2016-01-30

    This report presents the performance characteristics of two “two-stage” fast spectrum fuel cycle options proposed to enhance uranium resource utilization and to reduce nuclear waste generation. One is a two-stage fast spectrum fuel cycle option of continuous recycle of plutonium (Pu) in a fast reactor (FR) and subsequent burning of minor actinides (MAs) in an accelerator-driven system (ADS). The first stage is a sodium-cooled FR fuel cycle starting with low-enriched uranium (LEU) fuel; at the equilibrium cycle, the FR is operated using the recovered Pu and natural uranium without supporting LEU. Pu and uranium (U) are co-extracted from the discharged fuel and recycled in the first stage, and the recovered MAs are sent to the second stage. The second stage is a sodium-cooled ADS in which MAs are burned in an inert matrix fuel form. The discharged fuel of ADS is reprocessed, and all the recovered heavy metals (HMs) are recycled into the ADS. The other is a two-stage FR/ADS fuel cycle option with MA targets loaded in the FR. The recovered MAs are not directly sent to ADS, but partially incinerated in the FR in order to reduce the amount of MAs to be sent to the ADS. This is a heterogeneous recycling option of transuranic (TRU) elements

  8. Two-stage double-level rotational osteotomy in the treatment of congenital radioulnar synostosis.

    PubMed

    El-Adl, Wael

    2007-12-01

    Congenital proximal radioulnar synostosis is a rare congenital anomaly that can be extremely disabling, especially when it occurs bilaterally or if there is severe hyperpronation. Currently, osteotomy to achieve a neutral or slightly pronated position is widely accepted for the management of patients who have severe pronation. The present study evaluates the result of two-stage double-level rotational osteotomy of both the radius and ulna in the treatment of severe congenital radioulnar synostosis. Nine children with severe congenital radioulnar synostosis underwent two-stage double-level rotational osteotomy of both the radius and ulna at Mansoura University Hospital. There were seven boys and two girls with a mean age of 5.6 years who were followed up for a mean of 26 months. The position of the forearm was improved from a mean pronation deformity of 76 degrees (60 degrees to 85 degrees) to 30 degrees of pronation in the affected dominant extremities and 20 degrees of supination in non-dominant extremities in all cases. Bony union was achieved by 5.9 weeks with no loss of correction. The advantages of this technique are that it is easy, safe, with absence of severe postoperative complications and requires a small surgical scar. A drawback of the technique is that the rotation correction depends only on a cast, so that a correction loss might occur if the plaster cast loosens.

  9. Rules and mechanisms for efficient two-stage learning in neural circuits

    PubMed Central

    Teşileanu, Tiberiu; Ölveczky, Bence; Balasubramanian, Vijay

    2017-01-01

    Trial-and-error learning requires evaluating variable actions and reinforcing successful variants. In songbirds, vocal exploration is induced by LMAN, the output of a basal ganglia-related circuit that also contributes a corrective bias to the vocal output. This bias is gradually consolidated in RA, a motor cortex analogue downstream of LMAN. We develop a new model of such two-stage learning. Using stochastic gradient descent, we derive how the activity in ‘tutor’ circuits (e.g., LMAN) should match plasticity mechanisms in ‘student’ circuits (e.g., RA) to achieve efficient learning. We further describe a reinforcement learning framework through which the tutor can build its teaching signal. We show that mismatches between the tutor signal and the plasticity mechanism can impair learning. Applied to birdsong, our results predict the temporal structure of the corrective bias from LMAN given a plasticity rule in RA. Our framework can be applied predictively to other paired brain areas showing two-stage learning. DOI: http://dx.doi.org/10.7554/eLife.20944.001 PMID:28374674

  10. Utilising biohydrogen to increase methane production, energy yields and process efficiency via two stage anaerobic digestion of grass.

    PubMed

    Massanet-Nicolau, Jaime; Dinsdale, Richard; Guwy, Alan; Shipley, Gary

    2015-01-01

    Real time measurement of gas production and composition were used to examine the benefits of two stage anaerobic digestion (AD) over a single stage AD, using pelletized grass as a feedstock. Controlled, parallel digestion experiments were performed in order to directly compare a two stage digestion system producing hydrogen and methane, with a single stage system producing just methane. The results indicated that as well as producing additional energy in the form of hydrogen, two stage digestion also resulted in significant increases to methane production, overall energy yields, and digester stability (as indicated by bicarbonate alkalinity and volatile fatty acid removal). Two stage AD resulted in an increase in energy yields from 10.36 MJ kg(-1) VS to 11.74 MJ kg(-1) VS, an increase of 13.4%. Using a two stage system also permitted a much shorter hydraulic retention time of 12 days whilst maintaining process stability.

  11. Structure design of and experimental research on a two-stage laval foam breaker for foam fluid recycling.

    PubMed

    Wang, Jin-song; Cao, Pin-lu; Yin, Kun

    2015-07-01

    Environmental, economical and efficient antifoaming technology is the basis for achievement of foam drilling fluid recycling. The present study designed a novel two-stage laval mechanical foam breaker that primarily uses vacuum generated by Coanda effect and Laval principle to break foam. Numerical simulation results showed that the value and distribution of negative pressure of two-stage laval foam breaker were larger than that of the normal foam breaker. Experimental results showed that foam-breaking efficiency of two-stage laval foam breaker was higher than that of normal foam breaker, when gas-to-liquid ratio and liquid flow rate changed. The foam-breaking efficiency of normal foam breaker decreased rapidly with increasing foam stability, whereas the two-stage laval foam breaker remained unchanged. Foam base fluid would be recycled using two-stage laval foam breaker, which would reduce the foam drilling cost sharply and waste disposals that adverse by affect the environment.

  12. Two-stage atlas subset selection in multi-atlas based image segmentation

    SciTech Connect

    Zhao, Tingting Ruan, Dan

    2015-06-15

    Purpose: Fast growing access to large databases and cloud stored data presents a unique opportunity for multi-atlas based image segmentation and also presents challenges in heterogeneous atlas quality and computation burden. This work aims to develop a novel two-stage method tailored to the special needs in the face of large atlas collection with varied quality, so that high-accuracy segmentation can be achieved with low computational cost. Methods: An atlas subset selection scheme is proposed to substitute a significant portion of the computationally expensive full-fledged registration in the conventional scheme with a low-cost alternative. More specifically, the authors introduce a two-stage atlas subset selection method. In the first stage, an augmented subset is obtained based on a low-cost registration configuration and a preliminary relevance metric; in the second stage, the subset is further narrowed down to a fusion set of desired size, based on full-fledged registration and a refined relevance metric. An inference model is developed to characterize the relationship between the preliminary and refined relevance metrics, and a proper augmented subset size is derived to ensure that the desired atlases survive the preliminary selection with high probability. Results: The performance of the proposed scheme has been assessed with cross validation based on two clinical datasets consisting of manually segmented prostate and brain magnetic resonance images, respectively. The proposed scheme demonstrates comparable end-to-end segmentation performance as the conventional single-stage selection method, but with significant computation reduction. Compared with the alternative computation reduction method, their scheme improves the mean and medium Dice similarity coefficient value from (0.74, 0.78) to (0.83, 0.85) and from (0.82, 0.84) to (0.95, 0.95) for prostate and corpus callosum segmentation, respectively, with statistical significance. Conclusions: The authors

  13. Two-stage Surgery for an Aortoesophageal Fistula Caused by Tuberculous Esophagitis

    PubMed Central

    Choi, Chang Woo; Lim, Jae Woong; Her, Keun

    2015-01-01

    An aortoesophageal fistula (AEF) is an extremely rare, potentially fatal condition, and aortic surgery is usually performed together with extracorporeal circulation. However, this surgical method has a high rate of surgical complications and mortality. This report describes an AEF caused by tuberculous esophagitis that was treated successfully using a two-stage operation. A 52-yr-old man was admitted to the hospital with severe hematemesis and syncope. Based on the computed tomography and diagnostic endoscopic findings, he was diagnosed with an AEF and initially underwent thoracic endovascular aortic repair. Esophageal reconstruction was performed after controlling the mediastinal inflammation. The patient suffered postoperative anastomotic leakage, which was treated by an endoscopic procedure, and the patient was discharged without any further problems. The patient received 9 months of anti-tuberculosis treatment after he was diagnosed with histologically confirmed tuberculous esophagitis; subsequently, he was followed as an outpatient and has had no recurrence of the tuberculosis or any further issues. PMID:26539019

  14. Two-stage electron acceleration by simultaneous stimulated Raman backward and forward scattering

    SciTech Connect

    Bertrand, P.; Ghizzo, A.; Karttunen, S.J.; Paettikangas, T.J.H.; Salomaa, R.R.E.; Shoucri, M.

    1995-08-01

    The coexistence of stimulated Raman forward and backward scattering of intense electromagnetic radiation, which can occur, for instance, in laser fusion plasmas, is investigated. The simultaneous Raman forward and backward scattering is shown to create an electrostatic field structure which is exceptionally efficient in producing highly relativistic electrons. The mechanism of the electron acceleration is analyzed both by Vlasov--Maxwell simulations with self-consistent fields and by test particle calculations with prescribed electrostatic fields. The Vlasov--Maxwell simulations reveal that the two plasma waves generated by the backward and forward scattering are spatially separated, and thus form a two-stage electron ``accelerator.`` {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  15. Recurring two-stage evolutionary programming: a novel approach for numeric optimization.

    PubMed

    Alam, Mohammad Shafiul; Islam, Md Monirul; Yao, Xin; Murase, Kazuyuki

    2011-10-01

    In the application of evolutionary algorithms (EAs) to complex problem solving, it is essential to maintain proper balance between global exploration and local exploitation to achieve a good near-optimum solution to the problem. This paper presents a recurring two-stage evolutionary programming (RTEP) to balance the explorative and exploitative features of the conventional EAs. Unlike most previous works, RTEP is based on repeated and alternated execution of two different stages, namely, the exploration and exploitation stages, each with its own mutation operator, selection strategy, and explorative/exploitative objective. Both analytical and empirical studies have been carried out to understand the necessity of repeated and alternated exploration and exploitation operations in EAs. A suite of 48 benchmark numerical optimization problems has been used in the empirical studies. The experimental results show the remarkable effectiveness of the repeated exploration and exploitation operations employed by RTEP.

  16. Two-stage Raman compression of laser pulses with controllable phase fronts

    SciTech Connect

    Balakin, A. A.; Fraiman, G. M.; Dodin, I. Y.

    2015-05-15

    The phase front of an ultrashort laser pulse undergoing Raman amplification and compression in inhomogeneous plasma can be controlled such that it is unaffected by density gradients and thus remains focusable. This is achieved by performing the Raman backscattering in two stages. At the first stage, the standard nonlinear Raman compression of a seed wave takes place and produces a short ultraintense pulse, which yet may be poorly focusable. At the second stage, this amplified pulse is scattered again, now serving as a pump, off a second copy of the initial seed. This stage, which utilizes a denser and shorter plasma, is intended not for compression but rather for passing a significant fraction of the energy to the second seed quickly. Then, the output pulse that is produced is not just short and ultraintense, but also has the smooth phase front of the original seed.

  17. Synchronous rapid start-up of the methanation and anammox processes in two-stage ASBRs

    NASA Astrophysics Data System (ADS)

    Duan, Y.; Li, W. R.; Zhao, Y.

    2017-01-01

    The “methanation + anaerobic ammonia oxidation autotrophic denitrification” method was adopted by using anaerobic sequencing batch reactors (ASBRs) and realized a satisfactory synchronous removal of chemical oxygen demand (COD) and ammonia-nitrogen (NH4 +-N) in wastewater after 75 days operation. 90% of COD was removed at a COD load of 1.2 kg/(m3•d) and 90% of TN was removed at a TN load of 0.14 kg/(m3•d). The anammox reaction ratio was estimated to be 1: 1.32: 0.26. The results showed that synchronous rapid start-up of the methanation and anaerobic ammonia oxidation processes in two-stage ASBRs was feasible.

  18. Two stage low noise advanced technology fan. 1: Aerodynamic, structural, and acoustic design

    NASA Technical Reports Server (NTRS)

    Messenger, H. E.; Ruschak, J. T.; Sofrin, T. G.

    1974-01-01

    A two-stage fan was designed to reduce noise 20 db below current requirements. The first-stage rotor has a design tip speed of 365.8 m/sec and a hub/tip ratio of 0.4. The fan was designed to deliver a pressure ratio of 1.9 with an adiabatic efficiency of 85.3 percent at a specific inlet corrected flow of 209.2kg/sec/sq m. Noise reduction devices include acoustically treated casing walls, a flowpath exit acoustic splitter, a translating centerbody sonic inlet device, widely spaced blade rows, and the proper ratio of blades and vanes. Multiple-circular-arc rotor airfoils, resettable stators, split outer casings, and capability to go to close blade-row spacing are also included.

  19. Final two-stage MOAO on-sky demonstration with CANARY

    NASA Astrophysics Data System (ADS)

    Gendron, E.; Morris, T.; Basden, A.; Vidal, F.; Atkinson, D.; Bitenc, U.; Buey, T.; Chemla, F.; Cohen, M.; Dickson, C.; Dipper, N.; Feautrier, P.; Gach, J.-L.; Gratadour, D.; Henry, D.; Huet, J.-M.; Morel, C.; Morris, S.; Myers, R.; Osborn, J.; Perret, D.; Reeves, A.; Rousset, G.; Sevin, A.; Stadler, E.; Talbot, G.; Todd, S.; Younger, E.

    2016-07-01

    CANARY is an on-sky Laser Guide Star (LGS) tomographic AO demonstrator in operation at the 4.2m William Herschel Telescope (WHT) in La Palma. From the early demonstration of open-loop tomography on a single deformable mirror using natural guide stars in 2010, CANARY has been progressively upgraded each year to reach its final goal in July 2015. It is now a two-stage system that mimics the future E-ELT: a GLAO-driven woofer based on 4 laser guide stars delivers a ground-layer compensated field to a figure sensor locked tweeter DM, that achieves the final on-axis tomographic compensation. We present the overall system, the control strategy and an overview of its on-sky performance.

  20. Two-stage production of olefins utilizing a faujasite structure zeolite in hydrogenation stage

    SciTech Connect

    Kreuter, W.; Mansmann, M.; Watson, A.; Weber, H.; Wernicke, H.J.

    1980-02-12

    A process is disclosed for the production of olefins in two stages. In the first stage, heavy petroleum fractions are hydrogenated in the presence of hydrogen and a hydrogenation catalyst and, in the second stage, the thus-hydrogenated fractions are subjected to thermal cracking the presence of steam. The improvement comprises employing as the hydrogenation catalyst a zeolite of the faujasite structure combined with elements from groups VIB, VIIB and VIII of the periodic table of the elements, wherein the alkali component of the zeolite is exchanged at least partially for ammonium, hydronium, alkaline earth and/or rare earth ions, and the elements are present in a metallic, ionic, oxidic and/or sulfidic form.

  1. Enhanced acarbose production by Streptomyces M37 using a two-stage fermentation strategy

    PubMed Central

    Ren, Fei; Chen, Long; Xiong, Shuangli; Tong, Qunyi

    2017-01-01

    In this work, we investigated the effect of pH on Streptomyces M37 growth and its acarbose biosynthesis ability. We observed that low pH was beneficial for cell growth, whereas high pH favored acarbose synthesis. Moreover, addition of glucose and maltose to the fermentation medium after 72 h of cultivation promoted acarbose production. Based on these results, a two-stage fermentation strategy was developed to improve acarbose production. Accordingly, pH was kept at 7.0 during the first 72 h and switched to 8.0 after that. At the same time, glucose and maltose were fed to increase acarbose accumulation. With this strategy, we achieved an acarbose titer of 6210 mg/L, representing an 85.7% increase over traditional batch fermentation without pH control. Finally, we determined that the increased acarbose production was related to the high activity of glutamate dehydrogenase and glucose 6-phosphate dehydrogenase. PMID:28234967

  2. Performance of a highly loaded two stage axial-flow fan

    NASA Technical Reports Server (NTRS)

    Ruggeri, R. S.; Benser, W. A.

    1974-01-01

    A two-stage axial-flow fan with a tip speed of 1450 ft/sec (442 m/sec) and an overall pressure ratio of 2.8 was designed, built, and tested. At design speed and pressure ratio, the measured flow matched the design value of 184.2 lbm/sec (83.55kg/sec). The adiabatic efficiency at the design operating point was 85.7 percent. The stall margin at design speed was 10 percent. A first-bending-mode flutter of the second-stage rotor blades was encountered near stall at speeds between 77 and 93 percent of design, and also at high pressure ratios at speeds above 105 percent of design. A 5 deg closed reset of the first-stage stator eliminated second-stage flutter for all but a narrow speed range near 90 percent of design.

  3. Study of Boundary Layer Development in a Two-Stage Low-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.; Ashpis, David E.; Halstead, David E.; Wisler, David C.

    1999-01-01

    Experimental data from jet-engine tests have indicated that unsteady blade row interactions and separation can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study numerical simulations have been performed to study the boundary layer development in a two-stage low-pressure turbine, and to evaluate the transition models available for low Reynolds number flows in turbomachinery. The results of the simulations have been compared with experimental data, including airfoil loadings and integral boundary layer quantities. The predicted unsteady results display similar trends to the experimental data, but significantly overestimate the amplitude of the unsteadiness. The time-averaged results show close agreement with the experimental data.

  4. Bayesian inference using two-stage Laplace approximation for differential equation models

    NASA Astrophysics Data System (ADS)

    Dass, Sarat C.; Lee, Jaeyong; Lee, Kyoungjae

    2016-11-01

    We consider the problem of Bayesian inference for parameters in non-linear regression models whereby the underlying unknown response functions are formed by a set of differential equations. Bayesian methods of inference for unknown parameters rely primarily on the posterior obtained by Bayes rule. For differential equation models, analytic and closed forms for the posterior are not available and one has to resort to approximations. We propose a two-stage Laplace expansion to approximate the marginal likelihood, and hence, the posterior, to obtain an approximate closed form solution. For large sample sizes, the method of inference borrows from non-linear regression theory for maximum likelihood estimates, and is therefore, consistent. Our approach is exact in the limit and does not need the specification of an additional penalty parameter. Examples in this paper include the exponential model and SIR (Susceptible-Infected-Recovered) disease spread model.

  5. Denitrification of drinking water in a two-stage membrane bioreactor by using immobilized biomass.

    PubMed

    Ravnjak, Matjaž; Vrtovšek, Janez; Pintar, Albin

    2013-01-01

    Nitrate removal from polluted groundwater was investigated in a two-stage anoxic/oxic biofilm membrane bioreactor. The process was carried out with ethanol as a carbon source (corresponding C/N ratio of 1.4-2.5) and commercially available Biocontact-N biocarriers (Nisshinbo, Japan) to enable immobilization of highly efficient and long-lasting microbiota. At a residence time of the liquid phase equal to 2.5h, nitrate conversions higher than 99% were obtained without the formation of nitrite and ammonium ions. The concentration of total organic carbon in the reactor discharge was very similar to the content of organic matter in tap water. The biocarriers minimized the occurrence of suspended filamentous bacteria, and the utilization of increased shear force facilitated collisions of floating biocarrier particles with the outer membrane surface, preventing membrane fouling and resulting in stable operation of the system for 40 days.

  6. Two-stage reflective optical system for achromatic 10 nm x-ray focusing

    NASA Astrophysics Data System (ADS)

    Motoyama, Hiroto; Mimura, Hidekazu

    2015-12-01

    Recently, coherent x-ray sources have promoted developments of optical systems for focusing, imaging, and interferometers. In this paper, we propose a two-stage focusing optical system with the goal of achromatically focusing pulses from an x-ray free-electron laser (XFEL), with a focal width of 10 nm. In this optical system, the x-ray beam is expanded by a grazing-incidence aspheric mirror, and it is focused by a mirror that is shaped as a solid of revolution. We describe the design procedure and discuss the theoretical focusing performance. In theory, soft-XFEL lights can be focused to a 10 nm area without chromatic aberration and with high reflectivity; this creates an unprecedented power density of 1020 W cm-2 in the soft-x-ray range.

  7. Heuristic for Critical Machine Based a Lot Streaming for Two-Stage Hybrid Production Environment

    NASA Astrophysics Data System (ADS)

    Vivek, P.; Saravanan, R.; Chandrasekaran, M.; Pugazhenthi, R.

    2017-03-01

    Lot streaming in Hybrid flowshop [HFS] is encountered in many real world problems. This paper deals with a heuristic approach for Lot streaming based on critical machine consideration for a two stage Hybrid Flowshop. The first stage has two identical parallel machines and the second stage has only one machine. In the second stage machine is considered as a critical by valid reasons these kind of problems is known as NP hard. A mathematical model developed for the selected problem. The simulation modelling and analysis were carried out in Extend V6 software. The heuristic developed for obtaining optimal lot streaming schedule. The eleven cases of lot streaming were considered. The proposed heuristic was verified and validated by real time simulation experiments. All possible lot streaming strategies and possible sequence under each lot streaming strategy were simulated and examined. The heuristic consistently yielded optimal schedule consistently in all eleven cases. The identification procedure for select best lot streaming strategy was suggested.

  8. [Study of color blood image segmentation based on two-stage-improved FCM algorithm].

    PubMed

    Wang, Bin; Chen, Huaiqing; Huang, Hua; Rao, Jie

    2006-04-01

    This paper introduces a new method for color blood cell image segmentation based on FCM algorithm. By transforming the original blood microscopic image to indexed image, and by doing the colormap, a fuzzy apparoach to obviating the direct clustering of image pixel values, the quantity of data processing and analysis is enormously compressed. In accordance to the inherent features of color blood cell image, the segmentation process is divided into two stages. (1)confirming the number of clusters and initial cluster centers; (2) altering the distance measuring method by the distance weighting matrix in order to improve the clustering veracity. In this way, the problem of difficult convergence of FCM algorithm is solved, the iteration time of iterative convergence is reduced, the execution time of algarithm is decreased, and the correct segmentation of the components of color blood cell image is implemented.

  9. Histories obtained by two-stage questionnaire with automated transcript in specialist gynaecological practice.

    PubMed

    Robinson, D W; Walmsley, G L; Horrocks, J C; Milson, P; Jenkins, D M; De Dombal, F T; Scott, J S

    1975-11-29

    A two-stage questionnaire which the patient completes at home has been developed for use by gynaecological outpatients. The first stage (root) identifies the patient's problem and obtains general background information. The second stage (branch) deals with the presenting problem in depth. The system has proved highly acceptable to patients. At the clinic a non-medical assistant uses a programmed typewriter to transcribe the data into a typewritten history which is handed to the doctor before he examines the patient. The transcript compares favourably with the conventional hand-written history in content, ease of assimilation, and cost. While the questionnaire itself is an excellent means of collecting information it becomes an efficient means of transmitting information to the clinician only when combined with the transcript facility. There is no storage of confidential information and no scope for unethical disclosure.

  10. Design and Experimental Performance of a Two Stage Partial Admission Turbine, Task B.1/B.4

    NASA Technical Reports Server (NTRS)

    Sutton, R. F.; Boynton, J. L.; Akian, R. A.; Shea, Dan; Roschak, Edmund; Rojas, Lou; Orr, Linsey; Davis, Linda; King, Brad; Bubel, Bill

    1992-01-01

    A three-inch mean diameter, two-stage turbine with partial admission in each stage was experimentally investigated over a range of admissions and angular orientations of admission arcs. Three configurations were tested in which first stage admission varied from 37.4 percent (10 of 29 passages open, 5 per side) to 6.9 percent (2 open, 1 per side). Corresponding second stage admissions were 45.2 percent (14 of 31 passages open, 7 per side) and 12.9 percent (4 open, 2 per side). Angular positions of the second stage admission arcs with respect to the first stage varied over a range of 70 degrees. Design and off-design efficiency and flow characteristics for the three configurations are presented. The results indicated that peak efficiency and the corresponding isentropic velocity ratio decreased as the arcs of admission were decreased. Both efficiency and flow characteristics were sensitive to the second stage nozzle orientation angles.

  11. A Two-Stage Approach for Medical Supplies Intermodal Transportation in Large-Scale Disaster Responses

    PubMed Central

    Ruan, Junhu; Wang, Xuping; Shi, Yan

    2014-01-01

    We present a two-stage approach for the “helicopters and vehicles” intermodal transportation of medical supplies in large-scale disaster responses. In the first stage, a fuzzy-based method and its heuristic algorithm are developed to select the locations of temporary distribution centers (TDCs) and assign medial aid points (MAPs) to each TDC. In the second stage, an integer-programming model is developed to determine the delivery routes. Numerical experiments verified the effectiveness of the approach, and observed several findings: (i) More TDCs often increase the efficiency and utility of medical supplies; (ii) It is not definitely true that vehicles should load more and more medical supplies in emergency responses; (iii) The more contrasting the traveling speeds of helicopters and vehicles are, the more advantageous the intermodal transportation is. PMID:25350005

  12. Nitrification and microalgae cultivation for two-stage biological nutrient valorization from source separated urine.

    PubMed

    Coppens, Joeri; Lindeboom, Ralph; Muys, Maarten; Coessens, Wout; Alloul, Abbas; Meerbergen, Ken; Lievens, Bart; Clauwaert, Peter; Boon, Nico; Vlaeminck, Siegfried E

    2016-07-01

    Urine contains the majority of nutrients in urban wastewaters and is an ideal nutrient recovery target. In this study, stabilization of real undiluted urine through nitrification and subsequent microalgae cultivation were explored as strategy for biological nutrient recovery. A nitrifying inoculum screening revealed a commercial aquaculture inoculum to have the highest halotolerance. This inoculum was compared with municipal activated sludge for the start-up of two nitrification membrane bioreactors. Complete nitrification of undiluted urine was achieved in both systems at a conductivity of 75mScm(-1) and loading rate above 450mgNL(-1)d(-1). The halotolerant inoculum shortened the start-up time with 54%. Nitrite oxidizers showed faster salt adaptation and Nitrobacter spp. became the dominant nitrite oxidizers. Nitrified urine as growth medium for Arthrospira platensis demonstrated superior growth compared to untreated urine and resulted in a high protein content of 62%. This two-stage strategy is therefore a promising approach for biological nutrient recovery.

  13. Two-stage feedforward tracking control system with error-based disturbance observer for optical discs

    NASA Astrophysics Data System (ADS)

    Sakimura, Naohide; Ohashi, Takahiro; Ohishi, Kiyoshi; Miyazaki, Toshimasa

    2014-09-01

    Recently, the scaling up of the storage capacity and data transfer rate of digital storage media has been required. However, increasing in the storage capacity and transfer rate makes optical head control more difficult. Thus, a tracking control system for optical discs must exhibit a high degree of precision control. Consequently, a new two-stage feedforward control (TSFFC) system for high-precision control is proposed in this paper. The proposed system is constructed using two zero phase error tracking (ZPET) control systems based on error prediction and an error-based disturbance observer (EDOB) that uses a notch filter to suppress non periodic disturbances. The proposed control system is designed for DDU-1000 for digital versatile discs (DVDs). The experimental results demonstrate that the proposed system effectively suppresses tracking errors.

  14. Enhanced biodiesel production in Neochloris oleoabundans by a semi-continuous process in two stage photobioreactors.

    PubMed

    Yoon, Se Young; Hong, Min Eui; Chang, Won Seok; Sim, Sang Jun

    2015-07-01

    Under autotrophic conditions, highly productive biodiesel production was achieved using a semi-continuous culture system in Neochloris oleoabundans. In particular, the flue gas generated by combustion of liquefied natural gas and natural solar radiation were used for cost-effective microalgal culture system. In semi-continuous culture, the greater part (~80%) of the culture volume containing vegetative cells grown under nitrogen-replete conditions in a first photobioreactor (PBR) was directly transferred to a second PBR and cultured sequentially under nitrogen-deplete conditions for accelerating oil accumulation. As a result, in semi-continuous culture, the productivities of biomass and biodiesel in the cells were increased by 58% (growth phase) and 51% (induction phase) compared to the cells in batch culture, respectively. The semi-continuous culture system using two stage photobioreactors is a very efficient strategy to further improve biodiesel production from microalgae under photoautotrophic conditions.

  15. Treatment of Ammonia Nitrogen Wastewater in Low Concentration by Two-Stage Ozonization.

    PubMed

    Luo, Xianping; Yan, Qun; Wang, Chunying; Luo, Caigui; Zhou, Nana; Jian, Chensheng

    2015-09-23

    Ammonia nitrogen wastewater (about 100 mg/L) was treated by two-stage ozone oxidation method. The effects of ozone flow rate and initial pH on ammonia removal were studied, and the mechanism of ammonia nitrogen removal by ozone oxidation was discussed. After the primary stage of ozone oxidation, the ammonia removal efficiency reached 59.32% and pH decreased to 6.63 under conditions of 1 L/min ozone flow rate and initial pH 11. Then, the removal efficiency could be over 85% (the left ammonia concentration was lower than 15 mg/L) after the second stage, which means the wastewater could have met the national discharge standards of China. Besides, the mechanism of ammonia removal by ozone oxidation was proposed by detecting the products of the oxidation: ozone oxidation directly and ·OH oxidation; ammonia was mainly transformed into NO₃(-)-N, less into NO₂(-)-N, not into N₂.

  16. Two-stage dilute-acid and organic-solvent lignocellulosic pretreatment for enhanced bioprocessing

    DOE PAGES

    Brodeur, G.; Telotte, J.; Stickel, J. J.; ...

    2016-08-26

    A two stage pretreatment approach for biomass is developed in the current work in which dilute acid (DA) pretreatment is followed by a solvent based pretreatment (N-methyl morpholine N oxide -- NMMO). When the combined pretreatment (DAWNT) is applied to sugarcane bagasse and corn stover, the rates of hydrolysis and overall yields (>90%) are seen to dramatically improve and under certain conditions 48 h can be taken off the time of hydrolysis with the additional NMMO step to reach similar conversions. DAWNT shows a 2-fold increase in characteristic rates and also fractionates different components of biomass -- DA treatment removesmore » the hemicellulose while the remaining cellulose is broken down by enzymatic hydrolysis after NMMO treatment to simple sugars. The remaining residual solid is high purity lignin. Lastly, future work will focus on developing a full scale economic analysis of DAWNT for use in biomass fractionation.« less

  17. Performance of two-stage fan with larger dampers on first-stage rotor

    NASA Technical Reports Server (NTRS)

    Urasek, D. C.; Cunnan, W. S.; Stevans, W.

    1979-01-01

    The performance of a two stage, high pressure-ratio fan, having large, part-span vibration dampers on the first stage rotor is presented and compared with an identical aerodynamically designed fan having smaller dampers. Comparisons of the data for the two damper configurations show that with increased damper size: (1) very high losses in the damper region reduced overall efficiency of first stage rotor by approximately 3 points, (2) the overall performance of each blade row, downstream of the damper was not significantly altered, although appreciable differences in the radial distributions of various performance parameters were noted, and (3) the lower performance of the first stage rotor decreased the overall fan efficiency more than 1 percentage point.

  18. Hydrogen/Oxygen Propellant Densifier Using a Two-Stage Pulse Tube Cryocooler

    NASA Astrophysics Data System (ADS)

    Nguyen, C.; Yeckley, A.; Culler, A.; Haberbusch, M.; Radebaugh, R.

    2004-06-01

    A unique, patent pending, thermoacoustic propellant densifier, that simultaneously densifies liquid hydrogen and liquid oxygen propellants for aerospace vehicles is introduced. The thermoacoustic densifier consists of a two-stage pulse tube cryocooler that operates at 30 Hz using helium as the working fluid. The extremely reliable pulse tube has no moving parts, is water cooled, and is acoustically driven. The pulse tube has been driven by a Thermoacoustic Stirling Heat Engine (TASHE) and a linear flexure bearing compressor. A laboratory prototype was designed, fabricated, and tested at the Sierra Lobo, Inc. facility in Milan, Ohio. Unique design features include a removable 2nd stage for easy testing of low temperature regenerator materials and an advanced aftercooler design geometry. A system description will be presented and experimental data of the pulse tube performance will be compared with REGEN 3.2 and other analytical predictions.

  19. Design of a Two-stage High-capacity Stirling Cryocooler Operating below 30K

    NASA Astrophysics Data System (ADS)

    Wang, Xiaotao; Dai, Wei; Zhu, Jian; Chen, Shuai; Li, Haibing; Luo, Ercang

    The high capacity cryocooler working below 30K can find many applications such as superconducting motors, superconducting cables and cryopump. Compared to the GM cryocooler, the Stirling cryocooler can achieve higher efficiency and more compact structure. Because of these obvious advantages, we have designed a two stage free piston Stirling cryocooler system, which is driven by a moving magnet linear compressor with an operating frequency of 40 Hz and a maximum 5 kW input electric power. The first stage of the cryocooler is designed to operate in the liquid nitrogen temperature and output a cooling power of 100 W. And the second stage is expected to simultaneously provide a cooling power of 50 W below the temperature of 30 K. In order to achieve the best system efficiency, a numerical model based on the thermoacoustic model was developed to optimize the system operating and structure parameters.

  20. Two-stage acceleration of interstellar ions driven by high-energy lepton plasma flows

    NASA Astrophysics Data System (ADS)

    Cui, YunQian; Sheng, ZhengMing; Lu, QuanMing; Li, YuTong; Zhang, Jie

    2015-10-01

    We present the particle-in-cell (PIC) simulation results of the interaction of a high-energy lepton plasma flow with background electron-proton plasma and focus on the acceleration processes of the protons. It is found that the acceleration follows a two-stage process. In the first stage, protons are significantly accelerated transversely (perpendicular to the lepton flow) by the turbulent magnetic field "islands" generated via the strong Weibel-type instabilities. The accelerated protons shows a perfect inverse-power energy spectrum. As the interaction continues, a shockwave structure forms and the protons in front of the shockwave are reflected at twice of the shock speed, resulting in a quasi-monoenergetic peak located near 200 MeV under the simulation parameters. The presented scenario of ion acceleration may be relevant to cosmic-ray generation in some astrophysical environments.

  1. Two stages of parafoveal processing during reading: Evidence from a display change detection task.

    PubMed

    Angele, Bernhard; Slattery, Timothy J; Rayner, Keith

    2016-08-01

    We used a display change detection paradigm (Slattery, Angele, & Rayner Human Perception and Performance, 37, 1924-1938 2011) to investigate whether display change detection uses orthographic regularity and whether detection is affected by the processing difficulty of the word preceding the boundary that triggers the display change. Subjects were significantly more sensitive to display changes when the change was from a nonwordlike preview than when the change was from a wordlike preview, but the preview benefit effect on the target word was not affected by whether the preview was wordlike or nonwordlike. Additionally, we did not find any influence of preboundary word frequency on display change detection performance. Our results suggest that display change detection and lexical processing do not use the same cognitive mechanisms. We propose that parafoveal processing takes place in two stages: an early, orthography-based, preattentional stage, and a late, attention-dependent lexical access stage.

  2. Two-stage neural algorithm for defect detection and characterization uses an active thermography

    NASA Astrophysics Data System (ADS)

    Dudzik, Sebastian

    2015-07-01

    In the paper a two-stage neural algorithm for defect detection and characterization is presented. In order to estimate the defect depth two neural networks trained on data obtained using an active thermography were employed. The first stage of the algorithm is developed to detect the defect by a classification neural network. Then the defects depth is estimated using a regressive neural network. In this work the results of experimental investigations and simulations are shown. Further, the sensitivity analysis of the presented algorithm was conducted and the impacts of emissivity error and the ambient temperature error on the depth estimation errors were studied. The results were obtained using a test sample made of material with a low thermal diffusivity.

  3. Bioconversion to chitosan: a two stage process employing chitin deacetylase from Penicillium oxalicum SAEM-51.

    PubMed

    Pareek, Nidhi; Vivekanand, V; Agarwal, Pragati; Saroj, Samta; Singh, Rajesh P

    2013-07-25

    Chitin deacetylase from Penicillium oxalicum SAEM-51 was evaluated for bioconversion of chitin to chitosan in a two stage chemical and enzymatic process. Variations in morphology, crystallinity and thermal properties following chemical treatment were evaluated by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis. Degree of deacetylation of the substrates was determined using FT-IR and elemental analysis. The pretreatment of substrate led to the decrease in crystallinity and formation of amorphous chitinous substrates to facilitate enzyme reaction. The treated chitin was further subjected to enzymatic deacetylation employing chitin deacetylase from P. oxalicum SAEM-51 to produce chitosan with considerably higher degree of deacetylation. Maximum deacetylation (79.52%) was achieved using superfine chitin, owing to its porous structure and low crystallinity. Further, derivation of reaction variables, i.e. substrate amount and enzyme dose through full-factorial central composite design led to enhanced degree of deacetylation with formation of 90% deacetylated chitosan.

  4. Study of a two-stage photobase generator for photolithography in microelectronics.

    PubMed

    Turro, Nicholas J; Li, Yongjun; Jockusch, Steffen; Hagiwara, Yuji; Okazaki, Masahiro; Mesch, Ryan A; Schuster, David I; Willson, C Grant

    2013-03-01

    The investigation of the photochemistry of a two-stage photobase generator (PBG) is described. Absorption of a photon by a latent PBG (1) (first step) produces a PBG (2). Irradiation of 2 in the presence of water produces a base (second step). This two-photon sequence (1 + hν → 2 + hν → base) is an important component in the design of photoresists for pitch division technology, a method that doubles the resolution of projection photolithography for the production of microelectronic chips. In the present system, the excitation of 1 results in a Norrish type II intramolecular hydrogen abstraction to generate a 1,4-biradiacal that undergoes cleavage to form 2 and acetophenone (Φ ∼ 0.04). In the second step, excitation of 2 causes cleavage of the oxime ester (Φ = 0.56) followed by base generation after reaction with water.

  5. A two-stage approach for medical supplies intermodal transportation in large-scale disaster responses.

    PubMed

    Ruan, Junhu; Wang, Xuping; Shi, Yan

    2014-10-27

    We present a two-stage approach for the "helicopters and vehicles" intermodal transportation of medical supplies in large-scale disaster responses. In the first stage, a fuzzy-based method and its heuristic algorithm are developed to select the locations of temporary distribution centers (TDCs) and assign medial aid points (MAPs) to each TDC. In the second stage, an integer-programming model is developed to determine the delivery routes. Numerical experiments verified the effectiveness of the approach, and observed several findings: (i) More TDCs often increase the efficiency and utility of medical supplies; (ii) It is not definitely true that vehicles should load more and more medical supplies in emergency responses; (iii) The more contrasting the traveling speeds of helicopters and vehicles are, the more advantageous the intermodal transportation is.

  6. Two-stage dilute-acid and organic-solvent lignocellulosic pretreatment for enhanced bioprocessing

    SciTech Connect

    Brodeur, G.; Telotte, J.; Stickel, J. J.; Ramakrishnan, S.

    2016-08-26

    A two stage pretreatment approach for biomass is developed in the current work in which dilute acid (DA) pretreatment is followed by a solvent based pretreatment (N-methyl morpholine N oxide -- NMMO). When the combined pretreatment (DAWNT) is applied to sugarcane bagasse and corn stover, the rates of hydrolysis and overall yields (>90%) are seen to dramatically improve and under certain conditions 48 h can be taken off the time of hydrolysis with the additional NMMO step to reach similar conversions. DAWNT shows a 2-fold increase in characteristic rates and also fractionates different components of biomass -- DA treatment removes the hemicellulose while the remaining cellulose is broken down by enzymatic hydrolysis after NMMO treatment to simple sugars. The remaining residual solid is high purity lignin. Lastly, future work will focus on developing a full scale economic analysis of DAWNT for use in biomass fractionation.

  7. Two-stage dilute-acid and organic-solvent lignocellulosic pretreatment for enhanced bioprocessing.

    PubMed

    Brodeur, G; Telotte, J; Stickel, J J; Ramakrishnan, S

    2016-11-01

    A two stage pretreatment approach for biomass is developed in the current work in which dilute acid (DA) pretreatment is followed by a solvent based pretreatment (N-methyl morpholine N oxide - NMMO). When the combined pretreatment (DAWNT) is applied to sugarcane bagasse and corn stover, the rates of hydrolysis and overall yields (>90%) are seen to dramatically improve and under certain conditions 48h can be taken off the time of hydrolysis with the additional NMMO step to reach similar conversions. DAWNT shows a 2-fold increase in characteristic rates and also fractionates different components of biomass - DA treatment removes the hemicellulose while the remaining cellulose is broken down by enzymatic hydrolysis after NMMO treatment to simple sugars. The remaining residual solid is high purity lignin. Future work will focus on developing a full scale economic analysis of DAWNT for use in biomass fractionation.

  8. Two-stage microfluidic chip for selective isolation of circulating tumor cells (CTCs).

    PubMed

    Hyun, Kyung-A; Lee, Tae Yoon; Lee, Su Hyun; Jung, Hyo-Il

    2015-05-15

    Over the past few decades, circulating tumor cells (CTCs) have been studied as a means of overcoming cancer. However, the rarity and heterogeneity of CTCs have been the most significant hurdles in CTC research. Many techniques for CTC isolation have been developed and can be classified into positive enrichment (i.e., specifically isolating target cells using cell size, surface protein expression, and so on) and negative enrichment (i.e., specifically eluting non-target cells). Positive enrichment methods lead to high purity, but could be biased by their selection criteria, while the negative enrichment methods have relatively low purity, but can isolate heterogeneous CTCs. To compensate for the known disadvantages of the positive and negative enrichments, in this study we introduced a two-stage microfluidic chip. The first stage involves a microfluidic magnetic activated cell sorting (μ-MACS) chip to elute white blood cells (WBCs). The second stage involves a geometrically activated surface interaction (GASI) chip for the selective isolation of CTCs. We observed up to 763-fold enrichment in cancer cells spiked into 5 mL of blood sample using the μ-MACS chip at 400 μL/min flow rate. Cancer cells were successfully separated with separation efficiencies ranging from 10.19% to 22.91% based on their EpCAM or HER2 surface protein expression using the GASI chip at a 100 μL/min flow rate. Our two-stage microfluidic chips not only isolated CTCs from blood cells, but also classified heterogeneous CTCs based on their characteristics. Therefore, our chips can contribute to research on CTC heterogeneity of CTCs, and, by extension, personalized cancer treatment.

  9. Novel two-stage piezoelectric-based ocean wave energy harvesters for moored or unmoored buoys

    NASA Astrophysics Data System (ADS)

    Murray, R.; Rastegar, J.

    2009-03-01

    Harvesting mechanical energy from ocean wave oscillations for conversion to electrical energy has long been pursued as an alternative or self-contained power source. The attraction to harvesting energy from ocean waves stems from the sheer power of the wave motion, which can easily exceed 50 kW per meter of wave front. The principal barrier to harvesting this power is the very low and varying frequency of ocean waves, which generally vary from 0.1Hz to 0.5Hz. In this paper the application of a novel class of two-stage electrical energy generators to buoyant structures is presented. The generators use the buoy's interaction with the ocean waves as a low-speed input to a primary system, which, in turn, successively excites an array of vibratory elements (secondary system) into resonance - like a musician strumming a guitar. The key advantage of the present system is that by having two decoupled systems, the low frequency and highly varying buoy motion is converted into constant and much higher frequency mechanical vibrations. Electrical energy may then be harvested from the vibrating elements of the secondary system with high efficiency using piezoelectric elements. The operating principles of the novel two-stage technique are presented, including analytical formulations describing the transfer of energy between the two systems. Also, prototypical design examples are offered, as well as an in-depth computer simulation of a prototypical heaving-based wave energy harvester which generates electrical energy from the up-and-down motion of a buoy riding on the ocean's surface.

  10. Condition monitoring of distributed systems using two-stage Bayesian inference data fusion

    NASA Astrophysics Data System (ADS)

    Jaramillo, Víctor H.; Ottewill, James R.; Dudek, Rafał; Lepiarczyk, Dariusz; Pawlik, Paweł

    2017-03-01

    In industrial practice, condition monitoring is typically applied to critical machinery. A particular piece of machinery may have its own condition monitoring system that allows the health condition of said piece of equipment to be assessed independently of any connected assets. However, industrial machines are typically complex sets of components that continuously interact with one another. In some cases, dynamics resulting from the inception and development of a fault can propagate between individual components. For example, a fault in one component may lead to an increased vibration level in both the faulty component, as well as in connected healthy components. In such cases, a condition monitoring system focusing on a specific element in a connected set of components may either incorrectly indicate a fault, or conversely, a fault might be missed or masked due to the interaction of a piece of equipment with neighboring machines. In such cases, a more holistic condition monitoring approach that can not only account for such interactions, but utilize them to provide a more complete and definitive diagnostic picture of the health of the machinery is highly desirable. In this paper, a Two-Stage Bayesian Inference approach allowing data from separate condition monitoring systems to be combined is presented. Data from distributed condition monitoring systems are combined in two stages, the first data fusion occurring at a local, or component, level, and the second fusion combining data at a global level. Data obtained from an experimental rig consisting of an electric motor, two gearboxes, and a load, operating under a range of different fault conditions is used to illustrate the efficacy of the method at pinpointing the root cause of a problem. The obtained results suggest that the approach is adept at refining the diagnostic information obtained from each of the different machine components monitored, therefore improving the reliability of the health assessment of

  11. Anti-kindling Induced by Two-Stage Coordinated Reset Stimulation with Weak Onset Intensity

    PubMed Central

    Zeitler, Magteld; Tass, Peter A.

    2016-01-01

    Abnormal neuronal synchrony plays an important role in a number of brain diseases. To specifically counteract abnormal neuronal synchrony by desynchronization, Coordinated Reset (CR) stimulation, a spatiotemporally patterned stimulation technique, was designed with computational means. In neuronal networks with spike timing–dependent plasticity CR stimulation causes a decrease of synaptic weights and finally anti-kindling, i.e., unlearning of abnormally strong synaptic connectivity and abnormal neuronal synchrony. Long-lasting desynchronizing aftereffects of CR stimulation have been verified in pre-clinical and clinical proof of concept studies. In general, for different neuromodulation approaches, both invasive and non-invasive, it is desirable to enable effective stimulation at reduced stimulation intensities, thereby avoiding side effects. For the first time, we here present a two-stage CR stimulation protocol, where two qualitatively different types of CR stimulation are delivered one after another, and the first stage comes at a particularly weak stimulation intensity. Numerical simulations show that a two-stage CR stimulation can induce the same degree of anti-kindling as a single-stage CR stimulation with intermediate stimulation intensity. This stimulation approach might be clinically beneficial in patients suffering from brain diseases characterized by abnormal neuronal synchrony where a first treatment stage should be performed at particularly weak stimulation intensities in order to avoid side effects. This might, e.g., be relevant in the context of acoustic CR stimulation in tinnitus patients with hyperacusis or in the case of electrical deep brain CR stimulation with sub-optimally positioned leads or side effects caused by stimulation of the target itself. We discuss how to apply our method in first in man and proof of concept studies. PMID:27242500

  12. Hydrogen and methane production through two-stage mesophilic anaerobic digestion of olive pulp.

    PubMed

    Koutrouli, Eleni C; Kalfas, Haralabos; Gavala, Hariklia N; Skiadas, Ioannis V; Stamatelatou, Katerina; Lyberatos, Gerasimos

    2009-08-01

    The present study focused on the anaerobic biohydrogen production from olive pulp (two phase olive mill wastes, TPOMW) and the subsequent anaerobic treatment of the effluent for methane production under mesophilic conditions in a two-stage process. Biohydrogen production from water-diluted (1:4) olive pulp was investigated at hydraulic retention times (HRT) of 30 h, 14.5 h and 7.5 h while methane production from the effluent of hydrogenogenic reactor was studied at 20 d, 15 d, 10d and 5d HRT. In comparison with previous studies, it has been shown that the thermophilic hydrogen production process was more efficient than the mesophilic one in both hydrogen production rate and yield. The methanogenic reactor was successfully operated at 20, 15 and 10 days HRT while it failed when an HRT of 5 days was applied. Methane productivity reached the maximum value of 1.13+/-0.08 L/L/d at 10 days HRT whereas the methane yield increased with the HRT. The Anaerobic Digestion Model no. 1 (ADM1) was applied to the obtained experimental data from the methanogenic reactor to simulate the digester response at all HRT tested. The ability of the model to predict the experimental results was evident even in the case of the process failure, thus implying that the ADM1 could be a valuable tool for process design even in the case of a complex feedstock. In general, the two-stage anaerobic digestion proved to be a stable, reliable and effective process for energy recovery and stabilization treatment of olive pulp.

  13. Enhanced bio-energy recovery in a two-stage hydrogen/methane fermentation process.

    PubMed

    Lee, M J; Song, J H; Hwang, S J

    2009-01-01

    A two-stage hydrogen/methane fermentation process has emerged as a feasible engineering system to recover bio-energy from wastewater. Hydrogen-producing bacteria (HPB) generate hydrogen from readily available carbohydrates, and organic acids produced during the hydrogen fermentation step can be degraded to generate methane in the following step. Three strong acids, HCl, H(2)SO(4), and HNO(3), were tested to determine the appropriate pre-treatment method for enhanced hydrogen production. The hydrogen production rates of 230, 290, and 20 L/kg(-glucose)/day was observed for the sludge treated with HCl, H(2)SO(4), and HNO(3), respectively, indicating that the acid pre-treatment using either HCl or H(2)SO(4) resulted in a significant increase in hydrogen production. The fluorescent in situ hybridization method indicated that the acid pre-treatment selectively enriched HPB including Clostridium sp. of cluster I from inoculum sludge. After hydrogen fermentation was terminated, the sludge was introduced to a methane fermentation reactor. This experiment showed methane production rates of 100, 30, and 13 L/kg(-glucose)/day for the sludge pre-treated with HCl, H(2)SO(4), and HNO(3), respectively, implying that both sulfate and nitrate inhibited the activity of methane-producing bacteria. Consequently, the acid pre-treatment might be a feasible option to enhance biogas recovery in the two-stage fermentation process, and HCl was selected as the optimal strong acid for the enrichment of HPB and the continuous production of methane.

  14. Antibiotic-Loaded Spacer for Two-Stage Revision of Infected Total Knee Arthroplasty.

    PubMed

    Vecchini, Eugenio; Micheloni, Gian Mario; Perusi, Francesco; Scaglia, Marco; Maluta, Tommaso; Lavini, Franco; Bondi, Manuel; Dall'Oca, Carlo; Magnan, Bruno

    2017-03-01

    Infection of total knee arthroplasty (TKA) is a challenge in orthopedic surgery. In literature TKA infection is classified according to the time after surgery: acute postoperative; late chronic; acute hematogenous; positive intraoperative microbiological growth. The purpose of this study is to present the results of the use of a preformed antibiotic-loaded spacer in TKA infections, treated by a two-stage revision procedure. A series of 19 consecutive patients (20 knees) with a diagnosis of infected TKA were treated from January 2003 to February 2012. Two-stage reimplantation protocols were completed only in 16 patients and these data were included in the study. We lost three patients at follow-up. An antibiotic-loaded preformed articulating polymethylmethacrylate spacer was applied. Patients were observed 1, 3, and 6 months postoperatively and then yearly for clinical and radiographic examination. The mean American Knee Society Score improved from 68.4 preoperatively (range, from 34 to 108) to 112.7 at final follow-up (range, from 49 to 180). The pain was evaluated as part of clinical score. It improved from an average of 19.3 preoperatively (range, from 10 to 30) to 34.3 at final follow-up (range, from 10 to 50). The average range of motion improved from 40.1 degrees (range, from 6 to 90 degrees) to 79.3 degrees (range, from 45 to 125 degrees). The use of the spacer allows obtaining a reduction of pain, an improvement of quality of life in the period of time between the two surgical stages and an easier reimplantation of TKA.

  15. Design of a Two-Stage Light Gas Gun for Muzzle Velocities of 10 - 11 kms

    NASA Technical Reports Server (NTRS)

    Bogdanoff, David W.

    2016-01-01

    Space debris poses a major risk to spacecraft. In low earth orbit, impact velocities can be 10 11 kms and as high as 15 kms. For debris shield design, it would be desirable to be able to launch controlled shape projectiles to these velocities. The design of the proposed 10 11 kmsec gun uses, as a starting point, the Ames 1.280.22 two stage gun, which has achieved muzzle velocities of 10 11.3 kmsec. That gun is scaled up to a 0.3125 launch tube diameter. The gun is then optimized with respect to maximum pressures by varying the pump tube length to diameter ratio (LD), the piston mass and the hydrogen pressure. A pump tube LD of 36.4 is selected giving the best overall performance. Piezometric ratios for the optimized guns are found to be 2.3, much more favorable than for more traditional two stage light gas guns, which range from 4 to 6. The maximum powder chamber pressures are 20 to 30 ksi. To reduce maximum pressures, the desirable range of the included angle of the cone of the high pressure coupling is found to be 7.3 to 14.6 degrees. Lowering the break valve rupture pressure is found to lower the maximum projectile base pressure, but to raise the maximum gun pressure. For the optimized gun with a pump tube LD of 36.4, increasing the muzzle velocity by decreasing the projectile mass and increasing the powder loads is studied. It appears that saboted spheres could be launched to 10.25 and possibly as high as 10.7 10.8 kmsec, and that disc-like plastic models could be launched to 11.05 kms. The use of a tantalum liner to greatly reduce bore erosion and increase muzzle velocity is discussed. With a tantalum liner, CFD code calculations predict muzzle velocities as high as 12 to 13 kms.

  16. Mineral chemistry of the Tissint meteorite: Indications of two-stage crystallization in a closed system

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Baziotis, Ioannis P.; Asimow, Paul D.; Bodnar, Robert J.; Taylor, Lawrence A.

    2016-12-01

    The Tissint meteorite is a geochemically depleted, olivine-phyric shergottite. Olivine megacrysts contain 300-600 μm cores with uniform Mg# ( 80 ± 1) followed by concentric zones of Fe-enrichment toward the rims. We applied a number of tests to distinguish the relationship of these megacrysts to the host rock. Major and trace element compositions of the Mg-rich core in olivine are in equilibrium with the bulk rock, within uncertainty, and rare earth element abundances of melt inclusions in Mg-rich olivines reported in the literature are similar to those of the bulk rock. Moreover, the P Kα intensity maps of two large olivine grains show no resorption between the uniform core and the rim. Taken together, these lines of evidence suggest the olivine megacrysts are phenocrysts. Among depleted olivine-phyric shergottites, Tissint is the first one that acts mostly as a closed system with olivine megacrysts being the phenocrysts. The texture and mineral chemistry of Tissint indicate a crystallization sequence of: olivine (Mg# 80 ± 1) → olivine (Mg# 76) + chromite → olivine (Mg# 74) + Ti-chromite → olivine (Mg# 74-63) + pyroxene (Mg# 76-65) + Cr-ulvöspinel → olivine (Mg# 63-35) + pyroxene (Mg# 65-60) + plagioclase, followed by late-stage ilmenite and phosphate. The crystallization of the Tissint meteorite likely occurred in two stages: uniform olivine cores likely crystallized under equilibrium conditions; and a fractional crystallization sequence that formed the rest of the rock. The two-stage crystallization without crystal settling is simulated using MELTS and the Tissint bulk composition, and can broadly reproduce the crystallization sequence and mineral chemistry measured in the Tissint samples. The transition between equilibrium and fractional crystallization is associated with a dramatic increase in cooling rate and might have been driven by an acceleration in the ascent rate or by encounter with a steep thermal gradient in the Martian crust.

  17. Performance evaluation of two-stage fuel cycle from SFR to PWR

    SciTech Connect

    Fei, T.; Hoffman, E.A.; Kim, T.K.; Taiwo, T.A.

    2013-07-01

    One potential fuel cycle option being considered is a two-stage fuel cycle system involving the continuous recycle of transuranics in a fast reactor and the use of bred plutonium in a thermal reactor. The first stage is a Sodium-cooled Fast Reactor (SFR) fuel cycle with metallic U-TRU-Zr fuel. The SFRs need to have a breeding ratio greater than 1.0 in order to produce fissile material for use in the second stage. The second stage is a PWR fuel cycle with uranium and plutonium mixed oxide fuel based on the design and performance of the current state-of-the-art commercial PWRs with an average discharge burnup of 50 MWd/kgHM. This paper evaluates the possibility of this fuel cycle option and discusses its fuel cycle performance characteristics. The study focuses on an equilibrium stage of the fuel cycle. Results indicate that, in order to avoid a positive coolant void reactivity feedback in the stage-2 PWR, the reactor requires high quality of plutonium from the first stage and minor actinides in the discharge fuel of the PWR needs to be separated and sent back to the stage-1 SFR. The electricity-sharing ratio between the 2 stages is 87.0% (SFR) to 13.0% (PWR) for a TRU inventory ratio (the mass of TRU in the discharge fuel divided by the mass of TRU in the fresh fuel) of 1.06. A sensitivity study indicated that by increasing the TRU inventory ratio to 1.13, The electricity generation fraction of stage-2 PWR is increased to 28.9%. The two-stage fuel cycle system considered in this study was found to provide a high uranium utilization (>80%). (authors)

  18. Genetic Variants at 1p11.2 and Breast Cancer Risk: A Two-Stage Study in Chinese Women

    PubMed Central

    Liu, Xiao'an; Dai, Juncheng; Jin, Guangfu; Qin, Zhenzhen; Chen, Jiaping; Wang, Shui; Wang, Xinru; Hu, Zhibin; Shen, Hongbing

    2011-01-01

    Background Genome-wide association studies (GWAS) have identified several breast cancer susceptibility loci, and one genetic variant, rs11249433, at 1p11.2 was reported to be associated with breast cancer in European populations. To explore the genetic variants in this region associated with breast cancer in Chinese women, we conducted a two-stage fine-mapping study with a total of 1792 breast cancer cases and 1867 controls. Methodology/Principal Findings Seven single nucleotide polymorphisms (SNPs) including rs11249433 in a 277 kb region at 1p11.2 were selected and genotyping was performed by using TaqMan® OpenArray™ Genotyping System for stage 1 samples (878 cases and 900 controls). In stage 2 (914 cases and 967 controls), three SNPs (rs2580520, rs4844616 and rs11249433) were further selected and genotyped for validation. The results showed that one SNP (rs2580520) located at a predicted enhancer region of SRGAP2 was consistently associated with a significantly increased risk of breast cancer in a recessive genetic model [Odds Ratio (OR)  =  1.66, 95% confidence interval (CI)  =  1.16–2.36 for stage 2 samples; OR  =  1.51, 95% CI  =  1.16–1.97 for combined samples, respectively]. However, no significant association was observed between rs11249433 and breast cancer risk in this Chinese population (dominant genetic model in combined samples: OR  =  1.20, 95% CI  =  0.92–1.57). Conclusions/Significance Genotypes of rs2580520 at 1p11.2 suggest that Chinese women may have different breast cancer susceptibility loci, which may contribute to the development of breast cancer in this population. PMID:21738711

  19. Tunable and switchable thulium-doped fiber laser utilizing Sagnac loops incorporating two-stage polarization maintaining fibers

    NASA Astrophysics Data System (ADS)

    He, Wei; Zhu, Lianqing; Dong, Mingli; Luo, Fei

    2016-05-01

    A ring cavity thulium-doped fiber laser incorporating a Sagnac loop is proposed and experimentally demonstrated. In the designed fiber laser, a 0.4-m-long thulium-doped fiber is selected as the gain medium; the Sagnac loop is composed of two-stage polarization maintaining fibers of lengths 1 m and 2 m, respectively; and one broadband reflection mirror is used as the wavelength reflector. In the experiment, the lasing threshold is 135 mW, and by adjusting the polarization controller, a tunable and stable single-wavelength laser can be realized. The line interval is less than 3 nm within 1832-1865 nm, the power difference of each line is less than 1.111 dB, and the side-mode suppression ratio is larger than 44.7 dB. When 1848.4 and 1846.4 nm single-wavelength lasers are realized, the peak power fluctuation is less than 0.18 dB and 0.206 dB, respectively, within 10 min of scan time. A tunable and stable dual-wavelength laser can be realized by adjusting polarization controller; the power difference is less than 3.68 dB, and the side-mode suppression ratio is more than 35.04 dB. When 1844 and 1863.2 nm lasers are obtained simultaneously, the power shift is less than 0.6 dB and 0.95 dB, respectively, at room temperature. By changing the polarization state, tunable triple-wavelength lasing can be achieved ultimately, and the side-mode suppression ratio is larger than 41 dB.

  20. A PRIOR EVALUATION OF TWO-STAGE CLUSTER SAMPLING FOR ACCURACY ASSESSMENT OF LARGE-AREA LAND-COVER MAPS

    EPA Science Inventory

    Two-stage cluster sampling reduces the cost of collecting accuracy assessment reference data by constraining sample elements to fall within a limited number of geographic domains (clusters). However, because classification error is typically positively spatially correlated, withi...

  1. Adaptive Urban Stormwater Management Using a Two-stage Stochastic Optimization Model

    NASA Astrophysics Data System (ADS)

    Hung, F.; Hobbs, B. F.; McGarity, A. E.

    2014-12-01

    In many older cities, stormwater results in combined sewer overflows (CSOs) and consequent water quality impairments. Because of the expense of traditional approaches for controlling CSOs, cities are considering the use of green infrastructure (GI) to reduce runoff and pollutants. Examples of GI include tree trenches, rain gardens, green roofs, and rain barrels. However, the cost and effectiveness of GI are uncertain, especially at the watershed scale. We present a two-stage stochastic extension of the Stormwater Investment Strategy Evaluation (StormWISE) model (A. McGarity, JWRPM, 2012, 111-24) to explicitly model and optimize these uncertainties in an adaptive management framework. A two-stage model represents the immediate commitment of resources ("here & now") followed by later investment and adaptation decisions ("wait & see"). A case study is presented for Philadelphia, which intends to extensively deploy GI over the next two decades (PWD, "Green City, Clean Water - Implementation and Adaptive Management Plan," 2011). After first-stage decisions are made, the model updates the stochastic objective and constraints (learning). We model two types of "learning" about GI cost and performance. One assumes that learning occurs over time, is automatic, and does not depend on what has been done in stage one (basic model). The other considers learning resulting from active experimentation and learning-by-doing (advanced model). Both require expert probability elicitations, and learning from research and monitoring is modelled by Bayesian updating (as in S. Jacobi et al., JWRPM, 2013, 534-43). The model allocates limited financial resources to GI investments over time to achieve multiple objectives with a given reliability. Objectives include minimizing construction and O&M costs; achieving nutrient, sediment, and runoff volume targets; and community concerns, such as aesthetics, CO2 emissions, heat islands, and recreational values. CVaR (Conditional Value at Risk) and

  2. AREA DETERMINATION OF DIABETIC FOOT ULCER IMAGES USING A CASCADED TWO-STAGE SVM BASED CLASSIFICATION.

    PubMed

    Wang, Lei; Pedersen, Peder; Agu, Emmanuel; Strong, Diane; Tulu, Bengisu

    2016-11-23

    It is standard practice for clinicians and nurses to primarily assess patients' wounds via visual examination. This subjective method can be inaccurate in wound assessment and also represents a significant clinical workload. Hence, computer-based systems, especially implemented on mobile devices, can provide automatic, quantitative wound assessment and can thus be valuable for accurately monitoring wound healing status. Out of all wound assessment parameters, the measurement of the wound area is the most suitable for automated analysis. Most of the current wound boundary determination methods only process the image of the wound area along with a small amount of surrounding healthy skin. In this paper, we present a novel approach that uses Support Vector Machine (SVM) to determine the wound boundary on a foot ulcer image captured with an image capture box, which provides controlled lighting, angle and range conditions. The Simple Linear Iterative Clustering (SLIC) method is applied for effective super-pixel segmentation. A cascaded two-stage classifier is trained as follows: in the first stage a set of k binary SVM classifiers are trained and applied to different subsets of the entire training images dataset, and a set of incorrectly classified instances are collected. In the second stage, another binary SVM classifier is trained on the incorrectly classified set. We extracted various color and texture descriptors from super-pixels that are used as input for each stage in the classifier training. Specifically, we apply the color and Bag-of-Word (BoW) representation of local Dense SIFT features (DSIFT) as the descriptor for ruling out irrelevant regions (first stage), and apply color and wavelet based features as descriptors for distinguishing healthy tissue from wound regions (second stage). Finally, the detected wound boundary is refined by applying a Conditional Random Field (CRF) image processing technique. We have implemented the wound classification on a Nexus

  3. Two-stage induced differentiation of OCT4+/Nanog+ stem-like cells in lung adenocarcinoma

    PubMed Central

    Ma, Meili; Lou, Yuqing; Zhang, Yanwei; Wu, Lixia; Chang, David W.; Zhao, Picheng; Dong, Qianggang; Wu, Xifeng; Han, Baohui

    2016-01-01

    Stem-like cells in solid tumors are purported to contribute to cancer development and poor treatment outcome. The abilities to self-renew, differentiate, and resist anticancer therapies are hallmarks of these rare cells, and steering them into lineage commitment may be one strategy to curb cancer development or progression. Vitamin D is a prohormone that can alter cell growth and differentiation and may induce the differentiation cancer stem-like cells. In this study, octamer-binding transcription factor 4 (OCT4)-positive/Nanog homeobox (Nanog)- positive lung adenocarcinoma stem-like cells (LACSCs) were enriched from spheroid cultured SPC-A1 cells and differentiated by a two-stage induction (TSI) method, which involved knockdown of hypoxia-inducible factor 1-alpha (HIF1α) expression (first stage) followed by sequential induction with 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3, VD3) and suberoylanilide hydroxamic acid (SAHA) treatment (second stage). The results showed the HIF1α-knockdowned cells displayed diminished cell invasion and clonogenic activities. Moreover, the TSI cells highly expressed tumor suppressor protein p63 (P63) and forkhead box J1 (FOXJ1) and lost stem cell characteristics, including absent expression of OCT4 and Nanog. These cells regained sensitivity to cisplatin in vitro while losing tumorigenic capacity and decreased tumor cell proliferation in vivo. Our results suggest that induced transdifferentiation of LACSCs by vitamin D and SAHA may become novel therapeutic avenue to alter tumor cell phenotypes and improve patient outcome. SIGNIFICANCE STATEMENT The development and progression of lung cancer may involve rare population of stem-like cells that have the ability to grow, differentiate, and resist drug treatment. However, current therapeutic strategies have mostly focused on tumor characteristics and neglected the potential source of cells that may contribute to poor clinical outcome. We generated lung adenocarcinoma stem-like cells from

  4. Comparative Analysis of Direct Hospital Care Costs between Aseptic and Two-Stage Septic Knee Revision

    PubMed Central

    Kasch, Richard; Merk, Sebastian; Assmann, Grit; Lahm, Andreas; Napp, Matthias; Merk, Harry; Flessa, Steffen

    2017-01-01

    Background The most common intermediate and long-term complications of total knee arthroplasty (TKA) include aseptic and septic failure of prosthetic joints. These complications cause suffering, and their management is expensive. In the future the number of revision TKA will increase, which involves a greater financial burden. Little concrete data about direct costs for aseptic and two-stage septic knee revisions with an in depth-analysis of septic explantation and implantation is available. Questions/Purposes A retrospective consecutive analysis of the major partial costs involved in revision TKA for aseptic and septic failure was undertaken to compare 1) demographic and clinical characteristics, and 2) variable direct costs (from a hospital department’s perspective) between patients who underwent single-stage aseptic and two-stage septic revision of TKA in a hospital providing maximum care. We separately analyze the explantation and implantation procedures in septic revision cases and identify the major cost drivers of knee revision operations. Methods A total of 106 consecutive patients (71 aseptic and 35 septic) was included. All direct costs of diagnosis, surgery, and treatment from the hospital department’s perspective were calculated as real purchase prices. Personnel involvement was calculated in units of minutes. Results Aseptic versus septic revisions differed significantly in terms of length of hospital stay (15.2 vs. 39.9 days), number of reported secondary diagnoses (6.3 vs. 9.8) and incision-suture time (108.3 min vs. 193.2 min). The management of septic revision TKA was significantly more expensive than that of aseptic failure ($12,223.79 vs. $6,749.43) (p <.001). On the level of the separate hospitalizations the mean direct costs of explantation stage ($4,540.46) were lower than aseptic revision TKA ($6,749.43) which were again lower than those of the septic implantation stage ($7,683.33). All mean costs of stays were not comparable as they

  5. Test and Evaluation of a Pilot Two-Stage Precipitator for Jet Engine Test Cell Exhaust Gas Cleaning

    DTIC Science & Technology

    1976-04-01

    then available for emission control . A two- stage electrostatic precipitator was recommended as .j he most viable alternative to a concept then being...TEST AND EVALUATION OF A "PILOT TWO* STAGE PRECIPITATOR FOR JET ENGINE TEST CELL 0 EXHAUST GA, S CLEANING C44 NAVAL AIR REWORK FACILITY NAVAL AIR...is the release you requested in your telephone conversation of 20 July 1976 with the undersigned. Yourn very tru~ly, Head Specifications Branch a 21

  6. Reducing the risk of foaming and decreasing viscosity by two-stage anaerobic digestion of sugar beet pressed pulp.

    PubMed

    Stoyanova, Elitza; Forsthuber, Boris; Pohn, Stefan; Schwarz, Christian; Fuchs, Werner; Bochmann, Günther

    2014-04-01

    Anaerobic digestion (AD) of sugar beet pressed pulp (SBPP) is a promising treatment concept. It produces biogas as a renewable energy source making sugar production more energy efficient and it turns SBPP from a residue into a valuable resource. In this study one- and two-stage mono fermentation at mesophilic conditions in a continuous stirred tank reactor were compared. Also the optimal incubation temperature for the pre-acidification stage was studied. The fastest pre-acidification, with a hydraulic retention time (HRT) of 4 days, occurred at a temperature of 55 °C. In the methanogenic reactor of the two-stage system stable fermentation at loading rate of 7 kg VS/m³ d was demonstrated. No artificial pH adjustment was necessary to maintain optimum levels in both the pre-acidification and the methanogenic reactor. The total HRT of the two-stage AD was 36 days which is considerably lower compared to the one-stage AD (50 days). The frequently observed problem of foaming at high loading rates was less severe in the two-stage reactor. Moreover the viscosity of digestate in the methanogenic stage of the two-stage fermentation was in average tenfold lower than in the one-stage fermentation. This decreases the energy input for the reactor stirring about 80 %. The observed advantages make the two-stage process economically attractive, despite higher investments for a two reactor system.

  7. Opposed piston linear compressor driven two-stage Stirling Cryocooler for cooling of IR sensors in space application

    NASA Astrophysics Data System (ADS)

    Bhojwani, Virendra; Inamdar, Asif; Lele, Mandar; Tendolkar, Mandar; Atrey, Milind; Bapat, Shridhar; Narayankhedkar, Kisan

    2017-04-01

    A two-stage Stirling Cryocooler has been developed and tested for cooling IR sensors in space application. The concept uses an opposed piston linear compressor to drive the two-stage Stirling expander. The configuration used a moving coil linear motor for the compressor as well as for the expander unit. Electrical phase difference of 80 degrees was maintained between the voltage waveforms supplied to the compressor motor and expander motor. The piston and displacer surface were coated with Rulon an anti-friction material to ensure oil less operation of the unit. The present article discusses analysis results, features of the cryocooler and experimental tests conducted on the developed unit. The two-stages of Cryo-cylinder and the expander units were manufactured from a single piece to ensure precise alignment between the two-stages. Flexure bearings were used to suspend the piston and displacer about its mean position. The objective of the work was to develop a two-stage Stirling cryocooler with 2 W at 120 K and 0.5 W at 60 K cooling capacity for the two-stages and input power of less than 120 W. The Cryocooler achieved a minimum temperature of 40.7 K at stage 2.

  8. Beyond two-stage models for lung carcinogenesis in the Mayak workers: implications for plutonium risk.

    PubMed

    Zöllner, Sascha; Sokolnikov, Mikhail E; Eidemüller, Markus

    2015-01-01

    Mechanistic multi-stage models are used to analyze lung-cancer mortality after Plutonium exposure in the Mayak-workers cohort, with follow-up until 2008. Besides the established two-stage model with clonal expansion, models with three mutation stages as well as a model with two distinct pathways to cancer are studied. The results suggest that three-stage models offer an improved description of the data. The best-fitting models point to a mechanism where radiation increases the rate of clonal expansion. This is interpreted in terms of changes in cell-cycle control mediated by bystander signaling or repopulation following cell killing. No statistical evidence for a two-pathway model is found. To elucidate the implications of the different models for radiation risk, several exposure scenarios are studied. Models with a radiation effect at an early stage show a delayed response and a pronounced drop-off with older ages at exposure. Moreover, the dose-response relationship is strongly nonlinear for all three-stage models, revealing a marked increase above a critical dose.

  9. Beyond Two-Stage Models for Lung Carcinogenesis in the Mayak Workers: Implications for Plutonium Risk

    PubMed Central

    Zöllner, Sascha; Sokolnikov, Mikhail E.; Eidemüller, Markus

    2015-01-01

    Mechanistic multi-stage models are used to analyze lung-cancer mortality after Plutonium exposure in the Mayak-workers cohort, with follow-up until 2008. Besides the established two-stage model with clonal expansion, models with three mutation stages as well as a model with two distinct pathways to cancer are studied. The results suggest that three-stage models offer an improved description of the data. The best-fitting models point to a mechanism where radiation increases the rate of clonal expansion. This is interpreted in terms of changes in cell-cycle control mediated by bystander signaling or repopulation following cell killing. No statistical evidence for a two-pathway model is found. To elucidate the implications of the different models for radiation risk, several exposure scenarios are studied. Models with a radiation effect at an early stage show a delayed response and a pronounced drop-off with older ages at exposure. Moreover, the dose-response relationship is strongly nonlinear for all three-stage models, revealing a marked increase above a critical dose. PMID:26000637

  10. Chemistry of the extractive phase of two stage liquefaction. [9-10-dihydroanthracene and octahydrophenanthrene

    SciTech Connect

    Neuworth, M.B.; Heredy, L.A.; McCoy, L.R.; Skowronski, R.P.; Ratto, J.J.

    1985-04-19

    An experimental program has been conducted to investigate the chemistry of the extractive phase of the Integrated Two-Stage Liquefaction process. The long-term objective of the program is a study of the structural correlations between the starting coal, the coal-derived process solvent, and the primary liquefaction products. The two specific objectives chosen for study under this contract were (1) an investigation of experimental techniques for determining the proportion of cyclic and acyclic alkyl bridges as key weak linkages in coal and coal extract and (2) the generation of experimental information on hydroaromatic structures in coal and their probable role in liquefaction. The experimental technique which was devised for this investigation involved acid-catalyzed depolymerization to cleave methylene and other alkyl bridges in the coal and catalytic dehydrogenation to obtain information on hydroaromatic structures. The results of these experiments were supplemented by structural characterization of the process solvent and the coal extract, experiments using model compounds, and the application of results obtained by others. The experimental work was carried out using Illinois No. 6 coal, coal extract, and process solvent obtained from the PDU coal liquefaction plant operated by C.E. Lummus Crest, Inc. Coal depolymerization was carried out by using phenol-BF/sub 3/ and 3-fluorophenol-BF/sub 3/. Dehydrogenation of coal process solvent fraction and model compounds was carried out using a solvent and a palladium catalyst. The results and conclusions are discussed. 16 refs., 41 figs., 26 tabs.

  11. A gas-loading system for LANL two-stage gas guns

    SciTech Connect

    Gibson, Lloyd Lee; Bartram, Brian Douglas; Dattelbaum, Dana Mcgraw; Lang, John Michael; Morris, John Scott

    2015-09-01

    A novel gas loading system was designed for the specific application of remotely loading high purity gases into targets for gas-gun driven plate impact experiments. The high purity gases are loaded into well-defined target configurations to obtain Hugoniot states in the gas phase at greater than ambient pressures.The small volume of the gas samples is challenging, as slight changing in the ambient temperature result in measurable pressure changes. Therefore, the ability to load a gas gun target and continually monitor the sample pressure prior to firing provides the most stable and reliable target fielding approach. We present the design and evaluation of a gas loading system built for the LANL 50 mm bore two-stage light gas gun. Targets for the gun are made of 6061 Al or OFHC Cu, and assembled to form a gas containment cell with a volume of approximately 1.38 cc. The compatibility of materials was a major consideration in the design of the system, particularly for its use with corrosive gases. Piping and valves are stainless steel with wetted seals made from Kalrez® and Teflon®. Preliminary testing was completed to ensure proper flow rate and that the proper safety controls were in place. The system has been used to successfully load Ar, Kr, Xe, and anhydrous ammonia with purities of up to 99.999 percent. The design of the system and example data from the plate impact experiments will be shown.

  12. Two-stage fan. 4: Performance data for stator setting angle optimization

    NASA Technical Reports Server (NTRS)

    Burger, G. D.; Keenan, M. J.

    1975-01-01

    Stator setting angle optimization tests were conducted on a two-stage fan to improve efficiency at overspeed, stall margin at design speed, and both efficiency and stall margin at partspeed. The fan has a design pressure ratio of 2.8, a flow rate of 184.2 lb/sec (83.55 kg/sec) and a 1st-stage rotor tip speed of 1450 ft/sec (441.96 in/sec). Performance was obtained at 70,100, and 105 percent of design speed with different combinations of 1st-stage and 2nd-stage stator settings. One combination of settings, other than design, was common to all three speeds. At design speed, a 2.0 percentage point increase in stall margin was obtained at the expense of a 1.3 percentage point efficiency decrease. At 105 percent speed, efficiency was improved by 1.8 percentage points but stall margin decreased 4.7 percentage points. At 70 percent speed, no change in stall margin or operating line efficiency was obtained with stator resets although considerable speed-flow requlation occurred.

  13. A gas-loading system for LANL two-stage gas guns

    NASA Astrophysics Data System (ADS)

    Gibson, L. L.; Bartram, B. D.; Dattelbaum, D. M.; Lang, J. M.; Morris, J. S.

    2017-01-01

    A novel gas loading system was designed for the specific application of remotely loading high purity gases into targets for gas-gun driven plate impact experiments. The high purity gases are loaded into well-defined target configurations to obtain Hugoniot states in the gas phase at greater than ambient pressures. The small volume of the gas samples is challenging, as slight changing in the ambient temperature result in measurable pressure changes. Therefore, the ability to load a gas gun target and continually monitor the sample pressure prior to firing provides the most stable and reliable target fielding approach. We present the design and evaluation of a gas loading system built for the LANL 50 mm bore two-stage light gas gun. Targets for the gun are made of 6061 Al or OFHC Cu, and assembled to form a gas containment cell with a volume of approximately 1.38 cc. The compatibility of materials was a major consideration in the design of the system, particularly for its use with corrosive gases. Piping and valves are stainless steel with wetted seals made from Kalrez® and Teflon®. Preliminary testing was completed to ensure proper flow rate and that the proper safety controls were in place. The system has been used to successfully load Ar, Kr, Xe, and anhydrous ammonia with purities of up to 99.999 percent. The design of the system and example data from the plate impact experiments will be shown.

  14. Orbiter Trajectory Analysis for a Two-Stage Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Cowling, Adam L.

    2011-01-01

    Trajectory analysis performed on NASA's reference two-stage-to-orbit launch vehicle upper stage will be presented. The work was completed in support of the Hypersonics Multidisciplinary Analysis and Optimization effort for the NASA-Air Force Joint System Study. Three degree-of-freedom (3-DOF) untrimmed trajectory analysis was performed for the orbiter ascent, closure and re-entry. An iterative closure process resulted in a 333,000 lb initial mass for the orbiter. The re-entry trajectory satisfied heating constraints for all payload out cases and met the constraints with reduced margins for payload in cases. Abort trajectories for engine out at staging, engine out during ascent, and failure to circularize in orbit, gave insight to the robustness of the orbiter. A trimmed ascent trajectory defined an engine gimbal location and the body flap angle best suited for maximizing injected mass. A trimmed re-entry trajectory revealed a need to update the trim routine to accommodate full flap aerodynamic data.

  15. Hydrogen and methane production from household solid waste in the two-stage fermentation process.

    PubMed

    Liu, Dawei; Liu, Dapeng; Zeng, Raymond J; Angelidaki, Irini

    2006-06-01

    A two-stage process combined hydrogen and methane production from household solid waste was demonstrated working successfully. The yield of 43 mL H(2)/g volatile solid (VS) added was generated in the first hydrogen production stage and the methane production in the second stage was 500 mL CH(4)/g VS added. This figure was 21% higher than the methane yield from the one-stage process, which was run as control. Sparging of the hydrogen reactor with methane gas resulted in doubling of the hydrogen production. pH was observed as a key factor affecting fermentation pathway in hydrogen production stage. The optimum pH range for hydrogen production in this system was in the range from 5 to 5.5. The short hydraulic retention time (2 days) applied in the first stage was enough to separate acidogenesis from methanogenesis. No additional control for preventing methanogenesis in the first stage was necessary. Furthermore, this study also provided direct evidence in the dynamic fermentation process that, hydrogen production increase was reflected by acetate to butyrate ratio increase in liquid phase.

  16. Treatment of Ammonia Nitrogen Wastewater in Low Concentration by Two-Stage Ozonization

    PubMed Central

    Luo, Xianping; Yan, Qun; Wang, Chunying; Luo, Caigui; Zhou, Nana; Jian, Chensheng

    2015-01-01

    Ammonia nitrogen wastewater (about 100 mg/L) was treated by two-stage ozone oxidation method. The effects of ozone flow rate and initial pH on ammonia removal were studied, and the mechanism of ammonia nitrogen removal by ozone oxidation was discussed. After the primary stage of ozone oxidation, the ammonia removal efficiency reached 59.32% and pH decreased to 6.63 under conditions of 1 L/min ozone flow rate and initial pH 11. Then, the removal efficiency could be over 85% (the left ammonia concentration was lower than 15 mg/L) after the second stage, which means the wastewater could have met the national discharge standards of China. Besides, the mechanism of ammonia removal by ozone oxidation was proposed by detecting the products of the oxidation: ozone oxidation directly and ·OH oxidation; ammonia was mainly transformed into NO3−-N, less into NO2−-N, not into N2. PMID:26404353

  17. A two-stage Bayesian design for co-development of new drugs and companion diagnostics.

    PubMed

    Karuri, Stella Wanjugu; Simon, Richard

    2012-05-10

    Most new drug development in oncology is based on targeting specific molecules. Genomic profiles and deregulated drug targets vary from patient to patient making new treatments likely to benefit only a subset of patients traditionally grouped in the same clinical trials. Predictive biomarkers are being developed to identify patients who are most likely to benefit from a particular treatment; however, their biological basis is not always conclusive. The inclusion of marker-negative patients in a trial is therefore sometimes necessary for a more informative evaluation of the therapy. In this paper, we present a two-stage Bayesian design that includes both marker-positive and marker-negative patients in a clinical trial. We formulate a family of prior distributions that represent the degree of a priori confidence in the predictive biomarker. To avoid exposing patients to a treatment to which they may not be expected to benefit, we perform an interim analysis that may stop accrual of marker-negative patients or accrual of all patients. We demonstrate with simulations that the design and priors used control type I errors, give adequate power, and enable the early futility analysis of test-negative patients to be based on prior specification on the strength of evidence in the biomarker.

  18. A two-stage storage routing model for green roof runoff detention.

    PubMed

    Vesuviano, Gianni; Sonnenwald, Fred; Stovin, Virginia

    2014-01-01

    Green roofs have been adopted in urban drainage systems to control the total quantity and volumetric flow rate of runoff. Modern green roof designs are multi-layered, their main components being vegetation, substrate and, in almost all cases, a separate drainage layer. Most current hydrological models of green roofs combine the modelling of the separate layers into a single process; these models have limited predictive capability for roofs not sharing the same design. An adaptable, generic, two-stage model for a system consisting of a granular substrate over a hard plastic 'egg box'-style drainage layer and fibrous protection mat is presented. The substrate and drainage layer/protection mat are modelled separately by previously verified sub-models. Controlled storm events are applied to a green roof system in a rainfall simulator. The time-series modelled runoff is compared to the monitored runoff for each storm event. The modelled runoff profiles are accurate (mean Rt(2) = 0.971), but further characterization of the substrate component is required for the model to be generically applicable to other roof configurations with different substrate.

  19. TRM: a powerful two-stage machine learning approach for identifying SNP-SNP interactions.

    PubMed

    Lin, Hui-Yi; Chen, Y Ann; Tsai, Ya-Yu; Qu, Xiaotao; Tseng, Tung-Sung; Park, Jong Y

    2012-01-01

    Studies have shown that interactions of single nucleotide polymorphisms (SNPs) may play an important role in understanding the causes of complex disease. We have proposed an integrated machine learning method that combines two machine-learning methods-Random Forests (RF) and Multivariate Adaptive Regression Splines (MARS)-to identify a subset of important SNPs and detect interaction patterns more effectively and efficiently. In this two-stage RF-MARS (TRM) approach, RF is first applied to detect a predictive subset of SNPs, and then MARS is used to identify the interaction patterns. We evaluated the TRM performances in four models. RF variable selection was based on out-of-bag classification error rate (OOB) and variable important spectrum (IS). Our results support that RF(OOB) had better performance than MARS and RF(IS) in detecting important variables. This study demonstrates that TRM(OOB) , which is RF(OOB) plus MARS, has combined the strengths of RF and MARS in identifying SNP-SNP interactions in a scenario of 100 candidate SNPs. TRM(OOB) had greater true positive rate and lower false positive rate compared with MARS, particularly for searching interactions with a strong association with the outcome. Therefore, the use of TRM(OOB) is favored for exploring SNP-SNP interactions in a large-scale genetic variation study.

  20. Characterisation of the current switch mechanism in two-stage wire array Z-pinches

    SciTech Connect

    Burdiak, G. C.; Lebedev, S. V.; Harvey-Thompson, A. J.; Hall, G. N.; Swadling, G. F.; Suzuki-Vidal, F.; Khoory, E.; Bland, S. N.; Pickworth, L.; Grouchy, P. de; Skidmore, J.; Suttle, L.; Waisman, E. M.

    2015-11-15

    In this paper, we describe the operation of a two-stage wire array z-pinch driven by the 1.4 MA, 240 ns rise-time Magpie pulsed-power device at Imperial College London. In this setup, an inverse wire array acts as a fast current switch, delivering a current pre-pulse into a cylindrical load wire array, before rapidly switching the majority of the generator current into the load after a 100–150 ns dwell time. A detailed analysis of the evolution of the load array during the pre-pulse is presented. Measurements of the load resistivity and energy deposition suggest significant bulk heating of the array mass occurs. The ∼5 kA pre-pulse delivers ∼0.8 J of energy to the load, leaving it in a mixed, predominantly liquid-vapour state. The main current switch occurs as the inverse array begins to explode and plasma expands into the load region. Electrical and imaging diagnostics indicate that the main current switch may evolve in part as a plasma flow switch, driven by the expansion of a magnetic cavity and plasma bubble along the length of the load array. Analysis of implosion trajectories suggests that approximately 1 MA switches into the load in 100 ns, corresponding to a doubling of the generator dI/dt. Potential scaling of the device to higher current machines is discussed.

  1. Regional frequency analysis at ungauged sites using a two-stage resampling generalized ensemble framework

    NASA Astrophysics Data System (ADS)

    Alobaidi, Mohammad H.; Marpu, Prashanth R.; Ouarda, Taha B. M. J.; Chebana, Fateh

    2015-10-01

    Regional frequency analysis (RFA) deals with the estimation of hydrological characteristics at sites where little or no data is available. Recently, machine learning applications to RFA have received considerable attention in terms of their flexibility in modeling as well as superior generalization ability compared to conventional approaches. The proper application of machine learning techniques, however, requires good understanding of the available information about system's dynamics, i.e. system variables. This paper presents two contributions to the literature. First, novel ensemble architecture, using a unique two-stage resampling approach, is proposed. The objective of the proposed ensemble model is to promote diversity within the individual learners and reduce over fitting. Second, the application of the proposed model is demonstrated in RFA case study to obtain improved regional flood quantile estimates at ungauged sites. A jackknife validation procedure is used for the evaluation of the model's performance. The method is applied to data from the province of Quebec, Canada. The model showed similar performance and generalization compared to major ensemble models in the literature, which were investigated in previous studies using the same data set. The proposed model confirmed the diversity requirement in ensemble modeling and, in the same time, validated the proposed model adherence to ensemble learning theory.

  2. Manufacture of gradient micro-structures of magnesium alloys using two stage extrusion dies

    SciTech Connect

    Hwang, Yeong-Maw; Huang, Tze-Hui; Alexandrov, Sergei; Naimark, Oleg Borisovich; Jeng, Yeau-Ren

    2013-12-16

    This paper aims to manufacture magnesium alloy metals with gradient micro-structures using hot extrusion process. The extrusion die was designed to have a straight channel part combined with a conical part. Materials pushed through this specially-designed die generate a non-uniform velocity distribution at cross sections inside the die and result in different strain and strain rate distributions. Accordingly, a gradient microstructure product can be obtained. Using the finite element analysis, the forming temperature, effective strain, and effective strain rate distributions at the die exit were firstly discussed for various inclination angles in the conical die. Then, hot extrusion experiments with a two stage die were conducted to obtain magnesium alloy products with gradient micro-structures. The effects of the inclination angle on the grain size distribution at cross sections of the products were also discussed. Using a die of an inclination angle of 15°, gradient micro-structures of the grain size decreasing gradually from 17 μm at the center to 4 μm at the edge of product were achieved.

  3. Parameter estimation for metabolic networks with two stage Bregman regularization homotopy inversion algorithm.

    PubMed

    Wang, Hong; Wang, Xi-cheng

    2014-02-21

    Metabolism is a very important cellular process and its malfunction contributes to human disease. Therefore, building dynamic models for metabolic networks with experimental data in order to analyze biological process rationally has attracted a lot of attention. Owing to the technical limitations, some unknown parameters contained in models need to be estimated effectively by means of the computational method. Generally, problems of parameter estimation of nonlinear biological network are known to be ill condition and multimodal. In particular, with the increasing amount and enlarging the scope of parameters, many optimization algorithms often fail to find a global solution. In this paper, two-stage variable factor Bregman regularization homotopy method is proposed. Discrete homotopy is used to identify the possible extreme region and continuous homotopy is executed for the purpose of stability of path tracing in the special region. Meanwhile, Latin hypercube sampling is introduced to get the good initial guess value and a perturbation strategy is developed to jump out of the local optimum. Three metabolic network inverse problems are investigated to demonstrate the effectiveness of the proposed method.

  4. Two-stage light-gas magnetoplasma accelerator for hypervelocity impact simulation

    NASA Astrophysics Data System (ADS)

    Khramtsov, P. P.; Vasetskij, V. A.; Makhnach, A. I.; Grishenko, V. M.; Chernik, M. Yu; Shikh, I. A.; Doroshko, M. V.

    2016-11-01

    The development of macroparticles acceleration methods for high-speed impact simulation in a laboratory is an actual problem due to increasing of space flights duration and necessity of providing adequate spacecraft protection against micrometeoroid and space debris impacts. This paper presents results of experimental study of a two-stage light- gas magnetoplasma launcher for acceleration of a macroparticle, in which a coaxial plasma accelerator creates a shock wave in a high-pressure channel filled with light gas. Graphite and steel spheres with diameter of 2.5-4 mm were used as a projectile and were accelerated to the speed of 0.8-4.8 km/s. A launching of particle occurred in vacuum. For projectile velocity control the speed measuring method was developed. The error of this metod does not exceed 5%. The process of projectile flight from the barrel and the process of a particle collision with a target were registered by use of high-speed camera. The results of projectile collision with elements of meteoroid shielding are presented. In order to increase the projectile velocity, the high-pressure channel should be filled with hydrogen. However, we used helium in our experiments for safety reasons. Therefore, we can expect that the range of mass and velocity of the accelerated particles can be extended by use of hydrogen as an accelerating gas.

  5. Two-stage combined treatment of acid mine drainage and municipal wastewater.

    PubMed

    Deng, Dongyang; Lin, Lian-Shin

    2013-01-01

    This study examined the feasibility of the combined treatment of field-collected acid mine drainages (AMD, pH = 4.2 ± 0.9, iron = 112 ± 118 mg/L, sulfate = 1,846 ± 594 mg/L) and municipal wastewater (MWW, avg. chemical oxygen demand (COD) = 234-333 mg/L) using a two-stage process. The process consisted of batch mixing of the two wastes to condition the mixture solutions, followed by anaerobic biological treatment. The mixings performed under a range of AMD/MWW ratios resulted in phosphate removal of 9 to ∼100%, the mixture pH of 6.2-7.9, and COD/sulfate concentration ratio of 0.05-5.4. The biological treatment consistently removed COD and sulfate by >80% from the mixture solutions for COD/sulfate ratios of 0.6-5.4. Alkalinity was produced in the biological treatment causing increased pH and further removal of metals from the solutions. Scanning electron microscopy of produced sludge with energy dispersion analysis suggested chemical precipitation and associated adsorption and co-precipitation as the mechanisms for metal removal (Fe: >99%, Al: ∼100%, Mn: 75 to ∼100%, Ca: 52-81%, Mg: 13-76%, and Na: 56-76%). The study showed promising results for the treatment method and denoted the potential of developing innovative technologies for combined management of the two wastes in mining regions.

  6. Optimization of Boiling Water Reactor Loading Pattern Using Two-Stage Genetic Algorithm

    SciTech Connect

    Kobayashi, Yoko; Aiyoshi, Eitaro

    2002-10-15

    A new two-stage optimization method based on genetic algorithms (GAs) using an if-then heuristic rule was developed to generate optimized boiling water reactor (BWR) loading patterns (LPs). In the first stage, the LP is optimized using an improved GA operator. In the second stage, an exposure-dependent control rod pattern (CRP) is sought using GA with an if-then heuristic rule. The procedure of the improved GA is based on deterministic operators that consist of crossover, mutation, and selection. The handling of the encoding technique and constraint conditions by that GA reflects the peculiar characteristics of the BWR. In addition, strategies such as elitism and self-reproduction are effectively used in order to improve the search speed. The LP evaluations were performed with a three-dimensional diffusion code that coupled neutronic and thermal-hydraulic models. Strong axial heterogeneities and constraints dependent on three dimensions have always necessitated the use of three-dimensional core simulators for BWRs, so that optimization of computational efficiency is required. The proposed algorithm is demonstrated by successfully generating LPs for an actual BWR plant in two phases. One phase is only LP optimization applying the Haling technique. The other phase is an LP optimization that considers the CRP during reactor operation. In test calculations, candidates that shuffled fresh and burned fuel assemblies within a reasonable computation time were obtained.

  7. [Comparison research on two-stage sequencing batch MBR and one-stage MBR].

    PubMed

    Yuan, Xin-Yan; Shen, Heng-Gen; Sun, Lei; Wang, Lin; Li, Shi-Feng

    2011-01-01

    Aiming at resolving problems in MBR operation, like low nitrogen and phosphorous removal efficiency, severe membrane fouling and etc, comparison research on two-stage sequencing batch MBR (TSBMBR) and one-stage aerobic MBR has been done in this paper. The results indicated that TSBMBR owned advantages of SBR in removing nitrogen and phosphorous, which could make up the deficiency of traditional one-stage aerobic MBR in nitrogen and phosphorous removal. During steady operation period, effluent average NH4(+) -N, TN and TP concentration is 2.83, 12.20, 0.42 mg/L, which could reach domestic scenic environment use. From membrane fouling control point of view, TSBMBR has lower SMP in supernatant, specific trans-membrane flux deduction rate, membrane fouling resistant than one-stage aerobic MBR. The sedimentation and gel layer resistant of TSBMBR was only 6.5% and 33.12% of one-stage aerobic MBR. Besides high efficiency in removing nitrogen and phosphorous, TSBMBR could effectively reduce sedimentation and gel layer pollution on membrane surface. Comparing with one-stage MBR, TSBMBR could operate with higher trans-membrane flux, lower membrane fouling rate and better pollutants removal effects.

  8. Study on the Effect of Mutated Bacillus Megaterium in Two-Stage Fermentation of Vitamin C

    NASA Astrophysics Data System (ADS)

    Lü, Shujuan; Wang, Jun; Yao, Jianming; Yu, Zengliang

    2003-10-01

    Bacillus megaterium as a companion strain in two-stage fermentation of vitamin C could secrete some active substances to spur growth of Gluconobacter oxydans to produce 2-KLG. In the fermenting system where Gluconobacter oxydans was combined with GB82-a mutated strain of B. megaterium by ion implantation, the amount of 2-KLG harvested was larger than that produced by the original B. megaterium BP52 [1] being substituted for GB82. In this paper, we studied the effect of the active substances secreted by GB82 to enhance the capability of Gluconobacter oxydans to produce 2-KLG. The supernate of GB82 sampled at different cultivation times all had much more activity to spur Gluconobacter oxydans to yield 2-KLG than that of the original B. megaterium, which might be due to the genetic changes in the active components caused by ion implantation. Furthermore, the active substances of GB82's supernate would lose a part of its activity in extreme environments, which is typical of some proteins.

  9. Two-stage bile preparation with acetone for recovery of fluorescent aromatic compounds (FACs).

    PubMed

    Karami, Ali; Syed, Mohd A; Christianus, Annie; Willett, Kristine L; Mazzeo, Jeffrey R; Courtenay, Simon C

    2012-07-15

    In this study we sought to optimize recovery of fluorescent aromatic compounds (FACs) from the bile of African catfish (Clarias gariepinus) injected with 10mg/kg benzo[a]pyrene (BaP). Fractions of pooled bile were hydrolyzed, combined with ten volumes of methanol, ethanol, acetonitrile, or acetone, centrifuged and supernatants were analyzed by high-performance liquid chromatography with fluorescent detection (HPLC/FL). As well, to test whether FACs were being lost in solids from the centrifugation, pellets were resuspended, hydrolyzed and mixed with six volumes of the organic solvent that produced best FAC recovery from the supernatant, and subjected to HPLC/FL. Highest FAC concentrations were obtained with 2000μl and 1250μl acetone for supernatants and resuspended pellets respectively. FACs concentrations were negatively correlated with biliary protein content but were unaffected by addition of bovine serum albumin (BSA) followed by no incubation indicating that the presence of proteins in the biliary mixture does not simply interfere with detection of FACs. In another experiment, efficiency of acetone addition was compared to two different liquid-liquid extractions (L-LEs). Acetone additions provided significantly higher biliary FACs than the L-LE methods. The new two-stage bile preparation with acetone is an efficient, inexpensive and easily performed method.

  10. Development of a Two-Stage Mars Ascent Vehicle Using In-Situ Propellant Production

    NASA Technical Reports Server (NTRS)

    Paxton, Laurel; Vaughan, David

    2014-01-01

    Mars Sample Return (MSR) and Mars In-Situ Resource Utilization (ISRU) present two main challenges for the advancement of Mars science. MSR would demonstrate Mars lift-off capability, while ISRU would test the ability to produce fuel and oxidizer using Martian resources, a crucial step for future human missions. A two-stage Mars Ascent Vehicle (MAV) concept was developed to support sample return as well as in-situ propellant production. The MAV would be powered by a solid rocket first stage and a LOX-propane second stage. A liquid second-stage provides higher orbit insertion reliability than a solid second stage as well as a degree of complexity eventually required for manned missions. Propane in particular offers comparable performance to methane without requiring cryogenic storage. The total MAV mass would be 119.9 kg to carry an 11 kg payload to orbit. The feasibility of in-situ fuel and oxidizer production was also examined. Two potential schemes were evaluated for production capability, size and power requirements. The schemes examined utilize CO2 and water as starting blocks to produce LOX and a propane blend. The infrastructure required to fuel and launch the MAV was also explored.

  11. Two-Stage Fungal Pre-Treatment for Improved Biogas Production from Sisal Leaf Decortication Residues

    PubMed Central

    Muthangya, Mutemi; Mshandete, Anthony Manoni; Kivaisi, Amelia Kajumulo

    2009-01-01

    Sisal leaf decortications residue (SLDR) is amongst the most abundant agro-industrial residues in Tanzania and is a good feedstock for biogas production. Pre-treatment of the residue prior to its anaerobic digestion (AD) was investigated using a two-stage pre-treatment approach with two fungal strains, CCHT-1 and Trichoderma reesei in succession in anaerobic batch bioreactors. AD of the pre-treated residue with CCTH-1 at 10% (wet weight inoculum/SLDR) inoculum concentration incubated for four days followed by incubation for eight days with 25% (wet weight inoculum/SLDR) of T. reesei gave a methane yield of 0.292 ± 0.04 m3 CH4/kg volatile solids (VS)added. On reversing the pre-treatment succession of the fungal inocula using the same parameters followed by AD, methane yield decreased by about 55%. Generally, an increment in the range of 30–101% in methane yield in comparison to the un-treated SLDR was obtained. The results confirmed the potential of CCHT-1 followed by Trichoderma reesei fungi pre-treatment prior to AD to achieve significant improvement in biogas production from SLDR. PMID:20087466

  12. Performance assessment of two-stage anaerobic digestion of kitchen wastes.

    PubMed

    Bo, Zhang; Pin-Jing, He

    2014-01-01

    This study is aimed at investigating the performance of the two-phase anaerobic digestion of kitchen wastes in a lab-scale setup. The semi-continuous experiment showed that the two-phase anaerobic digestion of kitchen wastes had a bioconversion rate of 83%, biogas yield of 338 mL x (g chemical oxygen demand (COD))(-1) and total solid conversion of 63% when the entire two-phase anaerobic digestion process was subjected to an organic loading rate (OLR) of 10.7 g x (L d)(-1). In the hydrolysis-acidogenesis process, the efficiency of solubilization decreased from 72.6% to 41.1%, and the acidogenesis efficiency decreased from 31.8% to 17.8% with an increase in the COD loading rate. On the other hand, the performance of the subsequent methanogenic process was not susceptible to the increase in the feeding COD loading rate in the hydrolysis-acidogenesis stage. Lactic acid was one of the main fermentation products, accounting for over 40% of the total soluble COD in the fermentation liquid. The batch experiments indicated that the lactic acid was the earliest predominant fermentation product, and distributions of fermentation products were pH dependent. Results showed that increasing the feeding OLR of kitchen wastes made the two-stage anaerobic digestion process more effective. Moreover, there was a potential improvement in the performance of anaerobic digestion of kitchen wastes with a corresponding improvement in the hydrolysis process.

  13. Innovative two-stage mesophilic/thermophilic anaerobic degradation of sonicated sludge: performances and energy balance.

    PubMed

    Gianico, A; Braguglia, C M; Gallipoli, A; Mininni, G

    2015-05-01

    This study investigates for the first time, on laboratory scale, the possible application of an innovative enhanced stabilization process based on sequential mesophilic/thermophilic anaerobic digestion of waste-activated sludge, with low-energy sonication pretreatment. The first mesophilic digestion step was conducted at short hydraulic retention time (3-5 days), in order to favor volatile fatty acid production, followed by a longer thermophilic step of 10 days to enhance the bioconversion kinetics, assuring a complete pathogen removal. The high volatile solid removals, up to 55%, noticeably higher compared to the performances of a single-stage process carried out in same conditions, can guarantee the stability of the final digestate for land application. The ultrasonic pretreatment influenced significantly the fatty acid formation and composition during the first mesophilic step, improving consequently the thermophilic conversion of these compounds into methane. Methane yield from sonicated sludge digestion reached values up to 0.2 Nm(3)/kgVSfed. Positive energy balances highlighted the possible exploitation of this innovative two-stage digestion in place of conventional single-stage processes.

  14. A comprehensive microbial insight into two-stage anaerobic digestion of food waste-recycling wastewater.

    PubMed

    Shin, Seung Gu; Han, Gyuseong; Lim, Juntaek; Lee, Changsoo; Hwang, Seokhwan

    2010-09-01

    Microbial community structures were assessed in a two-stage anaerobic digestion system treating food waste-recycling wastewater. The reactors were operated for 390 d at 10 different hydraulic retention times (HRTs) ranging from 25 to 4 d. Stable operation was achieved with the overall chemical oxygen demand (COD) removal efficiency of 73.0-85.9% at organic loading rate of up to 35.6 g COD/L·d. Performance of the acidogenic reactors, however, changed significantly during operation. This change coincided with transition of the bacterial community from one dominated by Aeriscardovia- and Lactobacillus amylovorus-related species to one dominated by Lactobacillus acetotolerans- and Lactobacillus kefiri-like organisms. In methanogenic reactors, the microbial community structures also changed at this stage along with the shift from Methanoculleus- to Methanosarcina-like organisms. This trend was confirmed by the non-metric multidimensional scaling joint plot of microbial shifts along with performance parameters. These results indicated that the overall process performance was relatively stable compared to the dynamic changes in the microbial structures and the acidogenic performance.

  15. CHRONICLE: A Two-Stage Density-Based Clustering Algorithm for Dynamic Networks

    NASA Astrophysics Data System (ADS)

    Kim, Min-Soo; Han, Jiawei

    Information networks, such as social networks and that extracted from bibliographic data, are changing dynamically over time. It is crucial to discover time-evolving communities in dynamic networks. In this paper, we study the problem of finding time-evolving communities such that each community freely forms, evolves, and dissolves for any time period. Although the previous t-partite graph based methods are quite effective for discovering such communities from large-scale dynamic networks, they have some weak points such as finding only stable clusters of single path type and not being scalable w.r.t. the time period. We propose CHRONICLE, an efficient clustering algorithm that discovers not only clusters of single path type but also clusters of path group type. In order to find clusters of both types and also control the dynamicity of clusters, CHRONICLE performs the two-stage density-based clustering, which performs the 2nd-stage density-based clustering for the t-partite graph constructed from the 1st-stage density-based clustering result for each timestamp network. For a given data set, CHRONICLE finds all clusters in a fixed time by using a fixed amount of memory, regardless of the number of clusters and the length of clusters. Experimental results using real data sets show that CHRONICLE finds a wider range of clusters in a shorter time with a much smaller amount of memory than the previous method.

  16. Two-Stage Categorization in Brand Extension Evaluation: Electrophysiological Time Course Evidence

    PubMed Central

    Wang, Xiaoyi

    2014-01-01

    A brand name can be considered a mental category. Similarity-based categorization theory has been used to explain how consumers judge a new product as a member of a known brand, a process called brand extension evaluation. This study was an event-related potential study conducted in two experiments. The study found a two-stage categorization process reflected by the P2 and N400 components in brand extension evaluation. In experiment 1, a prime–probe paradigm was presented in a pair consisting of a brand name and a product name in three conditions, i.e., in-category extension, similar-category extension, and out-of-category extension. Although the task was unrelated to brand extension evaluation, P2 distinguished out-of-category extensions from similar-category and in-category ones, and N400 distinguished similar-category extensions from in-category ones. In experiment 2, a prime–probe paradigm with a related task was used, in which product names included subcategory and major-category product names. The N400 elicited by subcategory products was more significantly negative than that elicited by major-category products, with no salient difference in P2. We speculated that P2 could reflect the early low-level and similarity-based processing in the first stage, whereas N400 could reflect the late analytic and category-based processing in the second stage. PMID:25438152

  17. Isoglucose production from raw starchy materials based on a two-stage enzymatic system.

    PubMed

    Gromada, Anna; Fiedurek, Jan; Szczodrak, Janusz

    2008-01-01

    A new low-cost glucoamylase preparation for liquefaction and saccharification of starchy raw materials in a one-stage system was developed and characterized. A non-purified biocatalyst with a glucoamylase activity of 3.11 U/mg, an alpha-amylase activity of 0.12 WU/mg and a protein content of 0.04 mg protein/mg was obtained from a shaken-flask culture of the strain Aspergillus niger C-IV-4. Factors influencing the enzymatic hydrolysis of starchy materials such as reaction time, temperature and enzyme and substrate concentration were standardized to maximize the yield of glucose syrup. Thus, a 90% conversion of 5% starch, a 67.5% conversion of 5% potato flour and a 55% conversion of 5% wheat flour to sweet syrups containing up to 87% glucose was reached in 3 h using 1.24 glucoamylase U/mg hydrolyzed substrate. The application of such glucoamylase preparation and a commercially immobilized glucose isomerase for the production of glucose-fructose syrup in a two-stage system resulted in high production of stable glucose/fructose blends with a fructose content of 50%. A high concentration of fructose in obtained sweet syrups was achieved when isomerization was performed both in a batch and repeated batch process.

  18. Thrust augmentation options for the Beta 2 two-stage-to-orbit vehicle

    NASA Technical Reports Server (NTRS)

    Snyder, Christopher A.

    1993-01-01

    NASA LeRC is continuing to study propulsion concepts for a horizontal takeoff and landing, fully reusable, two-stage-to-orbit vehicle. This will be capable of launching and returning a 10,000 pound payload to a 100 nautical mile polar orbit using low-risk technology. The vehicle, Beta 2, is a derivative of the USAF/Boeing Beta vehicle which was designed to deliver a 50,000 pound payload to a similar orbit. Beta 2 stages at Mach 6.5 and about 100,000 ft altitude. The propulsion system for the booster is an over/under turbine bypass engine/ramjet configuration. In this paper, several options for thrust augmentation were studied in order to improve the performance of this engine where there was a critical need. Options studies were turbine engine overspeed in the transonic region, water injection at a various turbine engine locations also during the transonic region, and water injection at the turbine engine face during high speed operation. The methodology, constraints, propulsion performance, and mission study results are presented.

  19. Two-stage, low noise advanced technology fan. Volume 2: Aerodynamic data

    NASA Technical Reports Server (NTRS)

    Harley, K. G.; Odegard, P. A.

    1975-01-01

    Aerodynamic data from static tests of a two-stage advanced technology fan designed to minimize noise are presented. Fan design conditions include delivery of 209.1kg/sec/sq m (42.85 lbm/sec/sq ft) specific corrected flow at an overall pressure ratio of 1.9 and an adiabatic efficiency of 85.3 percent. The 0.836m (2.74ft) diameter first stage rotor has a hub/tip ratio of 0.4 and 365.8m/sec (1200ft/sec) design tip speed. In addition to the moderate tip speed and pressure rise per stage, other noise control design features involve widely spaced blade rows and proper selection of blade-vane ratios. Aerodynamic data are presented for tests with unifrom and with hub and tip radially distorted inlet flow. Aerodynamic data are also presented for tests of this fan with acoustic treatments, including acoustically treated casing walls, a flowpath exit acoustic ring, and a translating centerbody sonic inlet device. A complete tabulation of the overall performance data, the blade element data, and the power spectral density information relating to turbulence levels generated by the sonic inlet obtained during these tests is included. For vol. 1, see N74-33789.

  20. Design of a High-Energy, Two-Stage Pulsed Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Markusic, T. E.; Thio, Y. C. F.; Cassibry, J. T.; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    Design details of a proposed high-energy (approx. 50 kJ/pulse), two-stage pulsed plasma thruster are presented. The long-term goal of this project is to develop a high-power (approx. 500 kW), high specific impulse (approx. 7500 s), highly efficient (approx. 50%),and mechanically simple thruster for use as primary propulsion in a high-power nuclear electric propulsion system. The proposed thruster (PRC-PPT1) utilizes a valveless, liquid lithium-fed thermal plasma injector (first stage) followed by a high-energy pulsed electromagnetic accelerator (second stage). A numerical circuit model coupled with one-dimensional current sheet dynamics, as well as a numerical MHD simulation, are used to qualitatively predict the thermal plasma injection and current sheet dynamics, as well as to estimate the projected performance of the thruster. A set of further modelling efforts, and the experimental testing of a prototype thruster, is suggested to determine the feasibility of demonstrating a full scale high-power thruster.

  1. A two-stage magnetic refrigerator for astronomical applications with reservoir temperatures above 4 K

    NASA Technical Reports Server (NTRS)

    Hagmann, C.; Richards, P. L.

    1993-01-01

    We propose a novel adiabatic demagnetization refrigerator (ADR) to produce temperatures as low as 100 mK starting from a high temperature reservoir between 4 and 8 K. The high temperature reservoir for the ADR can be provided by a mechanical cooler or an unpumped liquid helium bath. This refrigerator can be used to cool bolometric infrared detectors for low background astronomy from mountain tops, balloons or satellites as well as to cool cryogenic x-ray detectors. The two-stage ADR consists of a single magnet with a paramagnetic chromic-cesium-alum (CCA) salt pill to produce the low temperature and paramagnetic gadolinium-gallium-garnet (GGG) as the first stage to intercept heat from the high temperature reservoir. Thermal contact between the paramagnets and the reservoir during magnetization is made with a mechanical heat switch. The ADR is suspended with Kevlar chords under tension for high mechanical stiffness and low parasitic heat leak. In a single cycle, the ADR maintains a temperature of 100 mK for 10 to 100 hours. This time depends strongly on the magnetic field and reservoir temperature but not on the volume of the paramagnetic material as long as the heat leak is dominated by the suspension.

  2. The modelling of trichloroethene photodegradation in Brij 35 surfactant by two-stage reaction.

    PubMed

    Choy, W K; Chu, W

    2001-07-01

    Various clean-up technologies have been developed for the removal and/or destruction of trichloroethene (TCE) in the subsurface. Surfactant-aided soil washing followed by photodegradation could be a promising approach to such a task. The modelling of TCE photodegradation by UV in Brij 35 surfactant micelles is therefore investigated. Two stages of TCE degradation are observed in surfactant Brij 35 systems. A lag phase is observed at the commencement of the degradation, but the duration of the lag phase is significantly reduced as the initial pH increases. As the overall decay of TCE is also found to be faster at higher pH levels, it is suggested that the free radical reaction is dominant at high pH levels, and the formation of lag phases is mainly due to the deficiency of free radicals at lower pH levels. Since the period of the lag phase gradually decreases with the increase of initial pH level, and the two pseudo first-order reaction constants (one for the lag phase and one for the subsequent fast decay) for TCE decay in both stages are also pH dependent, a non-steady-state mathematical model is developed for the prediction of TCE photodegradation in Brij 35 solutions, in which the remaining fraction of TCE (C/C0) in the system can be determined at any instant by using a simple parameter of the initial system pH.

  3. Two-stage transcriptional reprogramming in Saccharomyces cerevisiae for optimizing ethanol production from xylose.

    PubMed

    Cao, Limin; Tang, Xingliang; Zhang, Xinyuan; Zhang, Jingtao; Tian, Xuelei; Wang, Jingyu; Xiong, Mingyong; Xiao, Wei

    2014-07-01

    Conversion of lignocellulosic material to ethanol is a major challenge in second generation bio-fuel production by yeast Saccharomyces cerevisiae. This report describes a novel strategy named "two-stage transcriptional reprogramming (TSTR)" in which key gene expression at both glucose and xylose fermentation phases is optimized in engineered S. cerevisiae. Through a combined genome-wide screening of stage-specific promoters and the balancing of the metabolic flux, ethanol yields and productivity from mixed sugars were significantly improved. In a medium containing 50g/L glucose and 50g/L xylose, the top-performing strain WXY12 rapidly consumed glucose within 12h and within 84h it consistently achieved an ethanol yield of 0.48g/g total sugar, which was 94% of the theoretical yield. WXY12 utilizes a KGD1 inducible promoter to drive xylose metabolism, resulting in much higher ethanol yield than a reference strain using a strong constitutive PGK1 promoter. These promising results validate the TSTR strategy by synthetically regulating the xylose assimilation pathway towards efficient xylose fermentation.

  4. Classification of brain disease in magnetic resonance images using two-stage local feature fusion

    PubMed Central

    Li, Tao; Li, Wu; Yang, Yehui

    2017-01-01

    Background Many classification methods have been proposed based on magnetic resonance images. Most methods rely on measures such as volume, the cerebral cortical thickness and grey matter density. These measures are susceptible to the performance of registration and limited in representation of anatomical structure. This paper proposes a two-stage local feature fusion method, in which deformable registration is not desired and anatomical information is represented from moderate scale. Methods Keypoints are firstly extracted from scale-space to represent anatomical structure. Then, two kinds of local features are calculated around the keypoints, one for correspondence and the other for representation. Scores are assigned for keypoints to quantify their effect in classification. The sum of scores for all effective keypoints is used to determine which group the test subject belongs to. Results We apply this method to magnetic resonance images of Alzheimer's disease and Parkinson's disease. The advantage of local feature in correspondence and representation contributes to the final classification. With the help of local feature (Scale Invariant Feature Transform, SIFT) in correspondence, the performance becomes better. Local feature (Histogram of Oriented Gradient, HOG) extracted from 16×16 cell block obtains better results compared with 4×4 and 8×8 cell block. Discussion This paper presents a method which combines the effect of SIFT descriptor in correspondence and the representation ability of HOG descriptor in anatomical structure. This method has the potential in distinguishing patients with brain disease from controls. PMID:28207873

  5. Terminal differentiation-resistant epidermal cells in mice undergoing two-stage carcinogenesis.

    PubMed

    Miller, D R; Viaje, A; Aldaz, C M; Conti, C J; Slaga, T J

    1987-04-01

    We have used an in vivo-in vitro approach to investigate the cellular aspects of two-stage skin carcinogenesis. Female SENCAR mice initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were promoted twice weekly with 12-O-tetradecanoylphorbol-13-acetate (TPA). Epidermal cultures from untreated or TPA-treated mice had few focus-forming cells resistant to calcium-induced terminal differentiation. Cultures from mice treated with MNNG alone formed numerous foci. Brief promotion (four TPA treatments) of MNNG-treated mice produced fewer but statistically larger foci, suggesting that TPA was selecting against more slowly growing cells. MNNG plus TPA-treated mice with very early papillomas produced more and larger foci than those due to MNNG treatment alone, suggesting that the papillomas may have comprised calcium-resistant cells. These cells may indeed be initiated cells since a permanent cell line arising after MNNG plus brief TPA treatment eventually formed histological papillomas in vivo. If calcium-resistant cells are initiated, then there were many more initiated cells in the skin (with or without TPA treatment) than papillomas expected, implying that either some initiated cells never formed papillomas, or that a significant accumulation of initiated cells had already occurred in the skin within 2 weeks of MNNG treatment. Subsequent TPA promotion of these cells apparently produced a toxic response that passively selected for more rapidly growing initiated cells, which eventually accumulated into papillomas.

  6. Two stages in lymphocyte mediator production by differential susceptibility to blockade using niridazole.

    PubMed Central

    Daniels, J C; Fajardo, I; David, J R

    1975-01-01

    Sera from guinea pigs given niridazole, an anti-schistosomal compound, have been shown to reversibly block the production of antigen-induced migration inhibitory factor by sensitized guinea pig lymph node cells. Since niridazole itself has no effect in vitro, the blockade of production of migration inhibitory factor is probably due to drug metabolites in the serum. We report here further studies on the mechanism of this drug-induced suppression of cellular hypersensitivity; the data show that niridazole active serum does not block the production of migration inhibitory factor once it has been initiated. Indeed, if niridazole active serum is added a little as 60 sec after the addition of antigen, the lymphocytes will produce migration inhibitory factor. These results suggest the presence of at least two stages in production of migration inhibitory factor after the addition of antigen to lymphocytes. The first, lasting less than 60 sec, is susceptible to blockade by niridazole active serum; the second is not. The elucidation of the mechanism of this blockade should lead to further understanding of the early events after antigen triggering of sensitized lymphocytes. PMID:1105584

  7. Two-stage fungal pre-treatment for improved biogas production from sisal leaf decortication residues.

    PubMed

    Muthangya, Mutemi; Mshandete, Anthony Manoni; Kivaisi, Amelia Kajumulo

    2009-11-06

    Sisal leaf decortications residue (SLDR) is amongst the most abundant agro-industrial residues in Tanzania and is a good feedstock for biogas production. Pre-treatment of the residue prior to its anaerobic digestion (AD) was investigated using a two-stage pre-treatment approach with two fungal strains, CCHT-1 and Trichoderma reesei in succession in anaerobic batch bioreactors. AD of the pre-treated residue with CCTH-1 at 10% (wet weight inoculum/SLDR) inoculum concentration incubated for four days followed by incubation for eight days with 25% (wet weight inoculum/SLDR) of T. reesei gave a methane yield of 0.292 +/- 0.04 m(3) CH(4)/kg volatile solids (VS)(added). On reversing the pre-treatment succession of the fungal inocula using the same parameters followed by AD, methane yield decreased by about 55%. Generally, an increment in the range of 30-101% in methane yield in comparison to the un-treated SLDR was obtained. The results confirmed the potential of CCHT-1 followed by Trichoderma reesei fungi pre-treatment prior to AD to achieve significant improvement in biogas production from SLDR.

  8. Experimental development of a two-stage fluidized-bed/cyclonic agglomerating incinerator

    SciTech Connect

    Mensinger, M.C.; Rehmat, A.; Bryan, B.G.; Lau, F.S. ); Shearer, T.L. ); Duggan, P.A. )

    1991-01-01

    The Institute of Gas Technology (IGT) is conducting an experimental program to develop and test through pilot-plant scale of operation, IGT's two-stage fluidized-bed/cyclonic agglomerating incinerator (TSI). The TSI is based on combining the fluidized-bed agglomeration/gasification technology and the cyclonic combustion/incineration technology, which have been developed at IGT over many years. The TSI is a unique and extremely flexible combustor that can operate over a wide range of conditions in the fluidized-bed first stage from low temperature (desorption) to high temperature (agglomeration) including gasification of high-Btu wastes. The TSI can easily and efficiently destroy solid, liquid and gaseous organic wastes, while containing solid inorganic contaminants within an essentially non-leachable glassy matrix, suitable for disposal in an ordinary landfill. This paper presents the results of tests conducted in a batch, fluidized-bed bench-scale unit (BSU) with commercially available clean'' top soil and the same soil spiked with lead and chromium compounds. The objectives of these tests were to determine the operating conditions necessary to achieve soil agglomeration and to evaluate the leaching characteristics of the soil agglomerates formed. 7 refs., 7 figs., 6 tabs.

  9. Two-stage sequential sampling: A neighborhood-free adaptive sampling procedure

    USGS Publications Warehouse

    Salehi, M.; Smith, D.R.

    2005-01-01

    Designing an efficient sampling scheme for a rare and clustered population is a challenging area of research. Adaptive cluster sampling, which has been shown to be viable for such a population, is based on sampling a neighborhood of units around a unit that meets a specified condition. However, the edge units produced by sampling neighborhoods have proven to limit the efficiency and applicability of adaptive cluster sampling. We propose a sampling design that is adaptive in the sense that the final sample depends on observed values, but it avoids the use of neighborhoods and the sampling of edge units. Unbiased estimators of population total and its variance are derived using Murthy's estimator. The modified two-stage sampling design is easy to implement and can be applied to a wider range of populations than adaptive cluster sampling. We evaluate the proposed sampling design by simulating sampling of two real biological populations and an artificial population for which the variable of interest took the value either 0 or 1 (e.g., indicating presence and absence of a rare event). We show that the proposed sampling design is more efficient than conventional sampling in nearly all cases. The approach used to derive estimators (Murthy's estimator) opens the door for unbiased estimators to be found for similar sequential sampling designs. ?? 2005 American Statistical Association and the International Biometric Society.

  10. Two-stage seasonal streamflow forecasts to guide water resources decisions and water rights allocation

    NASA Astrophysics Data System (ADS)

    Block, P. J.; Gonzalez, E.; Bonnafous, L.

    2011-12-01

    Decision-making in water resources is inherently uncertain producing copious risks, ranging from operational (present) to planning (season-ahead) to design/adaptation (decadal) time-scales. These risks include human activity and climate variability/change. As the risks in designing and operating water systems and allocating available supplies vary systematically in time, prospects for predicting and managing such risks become increasingly attractive. Considerable effort has been undertaken to improve seasonal forecast skill and advocate for integration to reduce risk, however only minimal adoption is evident. Impediments are well defined, yet tailoring forecast products and allowing for flexible adoption assist in overcoming some obstacles. The semi-arid Elqui River basin in Chile is contending with increasing levels of water stress and demand coupled with insufficient investment in infrastructure, taxing its ability to meet agriculture, hydropower, and environmental requirements. The basin is fed from a retreating glacier, with allocation principles founded on a system of water rights and markets. A two-stage seasonal streamflow forecast at leads of one and two seasons prescribes the probability of reductions in the value of each water right, allowing water managers to inform their constituents in advance. A tool linking the streamflow forecast to a simple reservoir decision model also allows water managers to select a level of confidence in the forecast information.

  11. A two-stage morphological classifier of foci occurring in cell transformation assays

    NASA Astrophysics Data System (ADS)

    Crosta, Giovanni F.; Urani, Chiara; Bussinelli, Luca

    2009-02-01

    Cell Transformation Assays (CTA) rely on the detection of phenotypic changes, namely foci, induced by chemicals (e.g., xenobiotics or candidate drugs) in mammalian cells such as C3H10T1/2 mouse fibroblasts. A focus is a cell colony and as such is made visible by standardized techniques of light microscopy. Foci exhibit a variety of morphological features, by which three "Types" have been defined. Types II and III consist of cells having undergone neoplastic transformation. The assignment of a focus to a Type is based on the evaluation of phenotypic features by a trained human expert. An automated, two-stage morphological classifier of foci is described herewith. Morphological descriptors are extracted from light microscope images by the "spectrum enhancement" algorithm, which separates structure from texture. Said descriptors are submitted to a classifier, the first stage of which is trained to discriminate transformed cells from normal ones and the 2nd stage to discriminate Type III from Type II. The classifier operating in recognition mode (on images not used for training) is satisfactory in terms of confusion matrix entries. The whole procedure is aimed at removing subjectivity from the scoring and classification of foci and thus make CTA a more powerful tool in carcinogenesis studies.

  12. Syngas production by two-stage method of biomass catalytic pyrolysis and gasification.

    PubMed

    Xie, Qinglong; Kong, Sifang; Liu, Yangsheng; Zeng, Hui

    2012-04-01

    A two-stage technology integrated with biomass catalytic pyrolysis and gasification processes was utilized to produce syngas (H(2)+CO). In the presence of different nickel based catalysts, effects of pyrolysis temperature and gasification temperature on gas production were investigated. Experimental results showed that more syngas and char of high quality could be obtained at a temperature of 750°C in the stage of pyrolysis, and in the stage of gasification, pyrolysis char (produced at 750°C) reacted with steam and the maximum yield of syngas was obtained at 850°C. Syngas yield in this study was greatly increased compared with previous studies, up to 3.29Nm(3)/kg biomass. The pyrolysis process could be well explained by Arrhenius kinetic first-order rate equation. XRD analyses suggested that formation of Mg(0.4)Ni(0.6)O and increase of Ni(0) crystallite size were two main reasons for the deactivation of nickel based catalysts at higher temperature.

  13. Simulation and Analyses of Stage Separation of Two-Stage Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Pamadi, Bandu N.; Neirynck, Thomas A.; Hotchko, Nathaniel J.; Tartabini, Paul V.; Scallion, William I.; Murphy, K. J.; Covell, Peter F.

    2007-01-01

    NASA has initiated the development of methodologies, techniques and tools needed for analysis and simulation of stage separation of next generation reusable launch vehicles. As a part of this activity, ConSep simulation tool is being developed which is a MATLAB-based front-and-back-end to the commercially available ADAMS(Registerd TradeMark) solver, an industry standard package for solving multi-body dynamic problems. This paper discusses the application of ConSep to the simulation and analysis of staging maneuvers of two-stage-to-orbit (TSTO) Bimese reusable launch vehicles, one staging at Mach 3 and the other at Mach 6. The proximity and isolated aerodynamic database were assembled using the data from wind tunnel tests conducted at NASA Langley Research Center. The effects of parametric variations in mass, inertia, flight path angle, altitude from their nominal values at staging were evaluated. Monte Carlo runs were performed for Mach 3 staging to evaluate the sensitivity to uncertainties in aerodynamic coefficients.

  14. Simulation and Analyses of Stage Separation Two-Stage Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Pamadi, Bandu N.; Neirynck, Thomas A.; Hotchko, Nathaniel J.; Tartabini, Paul V.; Scallion, William I.; Murphy, Kelly J.; Covell, Peter F.

    2005-01-01

    NASA has initiated the development of methodologies, techniques and tools needed for analysis and simulation of stage separation of next generation reusable launch vehicles. As a part of this activity, ConSep simulation tool is being developed which is a MATLAB-based front-and-back-end to the commercially available ADAMS(registered Trademark) solver, an industry standard package for solving multi-body dynamic problems. This paper discusses the application of ConSep to the simulation and analysis of staging maneuvers of two-stage-to-orbit (TSTO) Bimese reusable launch vehicles, one staging at Mach 3 and the other at Mach 6. The proximity and isolated aerodynamic database were assembled using the data from wind tunnel tests conducted at NASA Langley Research Center. The effects of parametric variations in mass, inertia, flight path angle, altitude from their nominal values at staging were evaluated. Monte Carlo runs were performed for Mach 3 staging to evaluate the sensitivity to uncertainties in aerodynamic coefficients.

  15. Characterization of a Two-Stage Pulse Tube Cooler for Space Applications

    NASA Astrophysics Data System (ADS)

    Orsini, R.; Nguyen, T.; Colbert, R.; Raab, J.

    2010-04-01

    A two-stage long-life, low mass and efficient pulse tube cooler for space applications has been developed and acceptance tested for flight applications. This paper presents the data collected on four flight coolers during acceptance testing. Flight acceptance test of these cryocoolers includes thermal performance mapping over a range of reject temperatures, launch vibration testing and thermal cycling testing. Designed conservatively for a 10-year life, the coolers are required to provide simultaneous cooling powers at 95 K and 180 K while rejecting to 300 K with less than 187 W input power to the electronics. The total mass of each cooler and electronics system is 8.7 kg. The radiation-hardened and software driven control electronics provides cooler control functions which are fully re-configurable in orbit. These functions include precision temperature control to better than 100 mK p-p. This 2 stage cooler has heritage to the 12 Northrop Grumman Aerospace Systems (NGAS) coolers currently on orbit with 2 operating for more than 11.5 years.

  16. New higher-order Godunov code for modelling performance of two-stage light gas guns

    NASA Technical Reports Server (NTRS)

    Bogdanoff, D. W.; Miller, R. J.

    1995-01-01

    A new quasi-one-dimensional Godunov code for modeling two-stage light gas guns is described. The code is third-order accurate in space and second-order accurate in time. A very accurate Riemann solver is used. Friction and heat transfer to the tube wall for gases and dense media are modeled and a simple nonequilibrium turbulence model is used for gas flows. The code also models gunpowder burn in the first-stage breech. Realistic equations of state (EOS) are used for all media. The code was validated against exact solutions of Riemann's shock-tube problem, impact of dense media slabs at velocities up to 20 km/sec, flow through a supersonic convergent-divergent nozzle and burning of gunpowder in a closed bomb. Excellent validation results were obtained. The code was then used to predict the performance of two light gas guns (1.5 in. and 0.28 in.) in service at the Ames Research Center. The code predictions were compared with measured pressure histories in the powder chamber and pump tube and with measured piston and projectile velocities. Very good agreement between computational fluid dynamics (CFD) predictions and measurements was obtained. Actual powder-burn rates in the gun were found to be considerably higher (60-90 percent) than predicted by the manufacturer and the behavior of the piston upon yielding appears to differ greatly from that suggested by low-strain rate tests.

  17. A two-stage magnetic refrigerator for astronomical applications with reservoir temperatures above 4 K

    NASA Astrophysics Data System (ADS)

    Hagmann, C.; Richards, P. L.

    1993-02-01

    We propose a novel adiabatic demagnetization refrigerator (ADR) to produce temperatures as low as 100 mK starting from a high temperature reservoir between 4 and 8 K. The high temperature reservoir for the ADR can be provided by a mechanical cooler or an unpumped liquid helium bath. This refrigerator can be used to cool bolometric infrared detectors for low background astronomy from mountain tops, balloons or satellites as well as to cool cryogenic x-ray detectors. The two-stage ADR consists of a single magnet with a paramagnetic chromic-cesium-alum (CCA) salt pill to produce the low temperature and paramagnetic gadolinium-gallium-garnet (GGG) as the first stage to intercept heat from the high temperature reservoir. Thermal contact between the paramagnets and the reservoir during magnetization is made with a mechanical heat switch. The ADR is suspended with Kevlar chords under tension for high mechanical stiffness and low parasitic heat leak. In a single cycle, the ADR maintains a temperature of 100 mK for 10 to 100 hours. This time depends strongly on the magnetic field and reservoir temperature but not on the volume of the paramagnetic material as long as the heat leak is dominated by the suspension.

  18. Human Cough as a Two-Stage Jet and Its Role in Particle Transport

    PubMed Central

    Li, Yuguo

    2017-01-01

    The human cough is a significant vector in the transmission of respiratory diseases in indoor environments. The cough flow is characterized as a two-stage jet; specifically, the starting jet (when the cough starts and flow is released) and interrupted jet (after the source supply is terminated). During the starting-jet stage, the flow rate is a function of time; three temporal profiles of the exit velocity (pulsation, sinusoidal and real-cough) were investigated in this study, and our results showed that the cough flow’s maximum penetration distance was in the range of a 50.6–85.5 opening diameter (D) under our experimental conditions. The real-cough and sinusoidal cases exhibited greater penetration ability than the pulsation cases under the same characteristic Reynolds number (Rec) and normalized cough expired volume (Q/AD, with Q as the cough expired volume and A as the opening area). However, the effects of Rec and Q/AD on the maximum penetration distances proved to be more significant; larger values of Rec and Q/AD reflected cough flows with greater penetration distances. A protocol was developed to scale the particle experiments between the prototype in air, and the model in water. The water tank experiments revealed that although medium and large particles deposit readily, their maximum spread distance is similar to that of small particles. Moreover, the leading vortex plays an important role in enhancing particle transport. PMID:28046084

  19. An adaptive two-stage energy-efficiency mechanism for the doze mode in EPON

    NASA Astrophysics Data System (ADS)

    Nikoukar, AliAkbar; Hwang, I.-Shyan; Su, Yu-Min; Liem, Andrew Tanny

    2016-07-01

    Sleep and doze power-saving modes are the common ways to reduce power consumption of optical network units (ONUs) in Ethernet passive optical network (EPON). The doze mode turns off the ONU transmitter when there is no traffic in the upstream direction while the sleep mode turns off the ONU transmitter and receiver. As the result, the sleep mode is more efficient compared to the doze mode, but it introduces additional complexity of scheduling and signaling, losses the clock synchronization and requires long clock recovery time; furthermore, it requires the cooperation of the optical line terminal (OLT) in the downstream direction to queue frames. To improve the energy-saving in the doze mode, a new two-stage mechanism is introduced that the doze sleep duration is extended for longer time with acceptable quality-of-services (QoS) metrics when ONU is idle in the current cycle. By this way the ONU enters the doze mode even in the high load traffic; moreover, the green dynamic bandwidth allocation (GBA) is proposed to calculate the doze sleep duration based on the ONU queue state and incoming traffic ratio. Simulation results show that the proposed mechanism significantly improves the energy-saving 74% and 54% when traffic load is from the light load to the high load in different traffic situations, and also promises the QoS performance.

  20. Electric and hybrid electric vehicles: A technology assessment based on a two-stage Delphi study

    SciTech Connect

    Vyas, A.D.; Ng, H.K.; Santini, D.J.; Anderson, J.L.

    1997-12-01

    To address the uncertainty regarding future costs and operating attributes of electric and hybrid electric vehicles, a two stage, worldwide Delphi study was conducted. Expert opinions on vehicle attributes, current state of the technology, possible advancements, costs, and market penetration potential were sought for the years 2000, 2010, and 2020. Opinions related to such critical components as batteries, electric drive systems, and hybrid vehicle engines, as well as their respective technical and economic viabilities, were also obtained. This report contains descriptions of the survey methodology, analytical approach, and results of the analysis of survey data, together with a summary of other factors that will influence the degree of market success of electric and hybrid electric vehicle technologies. Responses by industry participants, the largest fraction among all the participating groups, are compared with the overall responses. An evaluation of changes between the two Delphi stages is also summarized. An analysis of battery replacement costs for various types is summarized, and variable operating costs for electric and hybrid vehicles are compared with those of conventional vehicles. A market penetration analysis is summarized, in which projected market shares from the survey are compared with predictions of shares on the basis of two market share projection models that use the cost and physical attributes provided by the survey. Finally, projections of market shares beyond the year 2020 are developed by use of constrained logit models of market shares, statistically fitted to the survey data.

  1. A Two-Stage Procedure Toward the Efficient Implementation of PANS and Other Hybrid Turbulence Models

    NASA Technical Reports Server (NTRS)

    Abdol-Hamid, Khaled S.; Girimaji, Sharath S.

    2004-01-01

    The main objective of this article is to introduce and to show the implementation of a novel two-stage procedure to efficiently estimate the level of scale resolution possible for a given flow on a given grid for Partial Averaged Navier-Stokes (PANS) and other hybrid models. It has been found that the prescribed scale resolution can play a major role in obtaining accurate flow solutions. The first step is to solve the unsteady or steady Reynolds Averaged Navier-Stokes (URANS/RANS) equations. From this preprocessing step, the turbulence length-scale field is obtained. This is then used to compute the characteristic length-scale ratio between the turbulence scale and the grid spacing. Based on this ratio, we can assess the finest scale resolution that a given grid for a given flow can support. Along with other additional criteria, we are able to analytically identify the appropriate hybrid solver resolution for different regions of the flow. This procedure removes the grid dependency issue that affects the results produced by different hybrid procedures in solving unsteady flows. The formulation, implementation methodology, and validation example are presented. We implemented this capability in a production Computational Fluid Dynamics (CFD) code, PAB3D, for the simulation of unsteady flows.

  2. Optimization Study of the Ames 0.5 Two-Stage Light Gas Gun

    NASA Technical Reports Server (NTRS)

    Bogdanoff, D. W.

    1996-01-01

    There is a need for more faithful simulation of space debris impacts on various space vehicles. Space debris impact velocities can range up to 14 km/sec and conventional two-stage light gas guns with moderately heavy saboted projectiles are limited to launch velocities of 7-8 km/sec. Any increases obtained in the launch velocities will result in more faithful simulations of debris impacts. It would also be valuable to reduce the maximum gun and projectile base pressures and the gun barrel erosion rate. In this paper, the results of a computational fluid dynamics (CFD) study designed to optimize the performance of the NASA Ames 0.5' gun by systematically varying seven gun operating parameters are reported. Particularly beneficial effects were predicted to occur if (1) the piston mass was decreased together with the powder mass and the hydrogen fill pressure and (2) the pump tube length was decreased. The optimum set of changes in gun operating conditions were predicted to produce an increase in muzzle velocity of 0.7-1.0 km/sec, simultaneously with a substantial decrease in gun erosion. Preliminary experimental data have validated the code predictions. Velocities of up to 8.2 km/sec with a 0.475 cm diameter saboted aluminum sphere have been obtained, along with large reductions in gun erosion rates.

  3. A two-stage cascade model of BOLD responses in human visual cortex.

    PubMed

    Kay, Kendrick N; Winawer, Jonathan; Rokem, Ariel; Mezer, Aviv; Wandell, Brian A

    2013-01-01

    Visual neuroscientists have discovered fundamental properties of neural representation through careful analysis of responses to controlled stimuli. Typically, different properties are studied and modeled separately. To integrate our knowledge, it is necessary to build general models that begin with an input image and predict responses to a wide range of stimuli. In this study, we develop a model that accepts an arbitrary band-pass grayscale image as input and predicts blood oxygenation level dependent (BOLD) responses in early visual cortex as output. The model has a cascade architecture, consisting of two stages of linear and nonlinear operations. The first stage involves well-established computations-local oriented filters and divisive normalization-whereas the second stage involves novel computations-compressive spatial summation (a form of normalization) and a variance-like nonlinearity that generates selectivity for second-order contrast. The parameters of the model, which are estimated from BOLD data, vary systematically across visual field maps: compared to primary visual cortex, extrastriate maps generally have larger receptive field size, stronger levels of normalization, and increased selectivity for second-order contrast. Our results provide insight into how stimuli are encoded and transformed in successive stages of visual processing.

  4. Improved two-stage equalization for coherent Pol-Mux QPSK and 16-QAM systems.

    PubMed

    Zhu, Chen; Tran, An V; Chen, Simin; Du, Liang B; Anderson, Trevor; Lowery, Arthur J; Skafidas, Efstratios

    2012-12-10

    We report a two-stage blind frequency domain equalization method for long-haul coherent polarization-multiplexed (pol-mux) systems using quadrature phase shift keying (QPSK) and 16-quadrature amplitude modulation (16-QAM). In the first stage, blind CD parameter prediction is conducted prior to a CD equalizer. This supports flexible path switching in optical networks. In the second stage, a frequency-domain multi-modulus algorithm (MMA) equalizer is used to cope with the residual fiber impairments and perform polarization de-multiplexing. Compared with the conventional constant modulus algorithm (CMA), MMA shows advantages including better steady state performance and a faster convergence rate. Furthermore, all the estimation and equalization algorithms are implemented in the frequency domain which potentially provides the least complexity for the pol-mux optical coherent systems. The proposed algorithm is experimentally demonstrated with an 800-km 10 Gbaud coherent optical pol-mux system. For QPSK signal, the proposed method achieves error-free transmission and shows superior convergence speed against CMA, and for 16-QAM signals, the proposed MMA outperforms CMA with more than 1-dB improvement in Q-value.

  5. Ecotoxicity of materials from integrated two-stage liquefaction and Exxon Donor Solvent processes

    SciTech Connect

    Dauble, D.D.; Scott, A.J.; Lusty, E.W.; Thomas, B.L.; Hanf, R.W. Jr.

    1983-05-01

    Coal-derived materials from two coal conversion processes were screened for potential ecological toxicity. We examined the toxicity of materials from different engineering or process options to an aquatic invertebrate and also related potential hazard to relative concentration, composition, and stability of water soluble components. For materials tested from the Integrated Two-Stage Liquefaction (ITSL) process, only the LC finer (LCF) 650/sup 0/F distillate was highly soluble in water at 20/sup 0/C. The LCF feed and Total Liquid Product (TLP) were not in liquid state at 20/sup 0/C and were relatively insoluble in water. Relative hazard to daphnids from ITSL materials was as follows: LCF 650/sup 0/F distillate greater than or equal to LCF feed greater than or equal to TLP. For Exxon Donor Solvent (EDS) materials, process solvent produced in the bottoms recycle mode was more soluble in water than once-through process solvent and, hence, slightly more acutely toxic to daphnids. When compared to other coal liquids or petroleum products, the ITSL or EDS liquids were intermediate in toxicity; relative hazard ranged from 1/7 to 1/13 of the Solvent Refined Coal (SRC)-II distillable blend, but was several times greater than the relative hazard for No. 2 diesel fuel oil or Prudhoe Bay crude oil. Although compositonal differences in water-soluble fractions (WSF) were noted among materials, phenolics were the major compound class in all WSFs and probably the primary contributor to acute toxicity.

  6. Two-stage hierarchical group testing for multiple infections with application to the Infertility Prevention Project

    PubMed Central

    Tebbs, Joshua M.; McMahan, Christopher S.; Bilder, Christopher R.

    2015-01-01

    Summary Screening for sexually transmitted diseases has benefited greatly from the use of group testing (pooled testing) to lower costs. With the development of assays that detect multiple infections, screening practices now involve testing pools of individuals for multiple infections simultaneously. Building on the research for single infection group testing procedures, we examine the performance of group testing for multiple infections. Our work is motivated by chlamydia and gonorrhea testing for the Infertility Prevention Project (IPP), a national program in the United States. We consider a two-stage pooling algorithm currently used to perform testing for the IPP. We first derive the operating characteristics of this algorithm for classification purposes (e.g., expected number of tests, misclassification probabilities, etc.) and identify pool sizes that minimize the expected number of tests. We then develop an expectation-maximization algorithm to estimate probabilities of infection using both group and individual retest responses. Our research shows that group testing can offer large cost savings when classifying individuals for multiple infections and can provide prevalence estimates that are actually more efficient than those from individual testing. PMID:24117173

  7. Food Behavior Change in Late-Life Widowhood: A Two-Stage Process

    PubMed Central

    Vesnaver, Elisabeth; Keller, Heather H.; Sutherland, Olga; Maitland, Scott B.; Locher, Julie L.

    2015-01-01

    Widowhood is a common life event for married older women. Prior research has found disruptions in eating behaviors to be common among widows. Little is known about the process underlying these disruptions. The aim of this study was to generate a theoretical understanding of the changing food behaviors of older women during the transition of widowhood. Qualitative methods based on constructivist grounded theory guided by a critical realist worldview were used. Individual active interviews were conducted with 15 community-living women, aged 71 to 86 years, living alone, and widowed six months to 15 years at the time of the interview. Participants described a variety of educational backgrounds and levels of health, were mainly white and of Canadian or European descent, and reported sufficient income to meet their needs. The loss of regular shared meals initiated a two-stage process whereby women first fall into new patterns and then re-establish the personal food system, thus enabling women to redirect their food system from one that satisfied the couple to one that satisfied their personal food needs. Influences on the trajectory of the change process included the couple’s food system, experience with nutritional care, food-related values, and food-related resources. Implications for research and practice are discussed. PMID:26232138

  8. Two-stage gas amplifier for ultrahigh resolution low vacuum scanning electron microscopy

    NASA Astrophysics Data System (ADS)

    Thiel, B. L.; Toth, M.; Schroemges, R. P. M.; Scholtz, J. J.; van Veen, G.; Knowles, W. R.

    2006-03-01

    We describe a magnetic field assisted, two-stage secondary electron gas amplification process for low vacuum scanning electron microscopy. The field of an ultrahigh resolution magnetic immersion objective lens and the electric field of an annular electrode configuration partition the amplification volume into two regions in which the electric and magnetic fields are parallel and crossed, respectively. The fields confine secondary electrons to axial and radial oscillations within the detector volume, until all of the kinetic energy imparted by an anode is dissipated through inelastic collisions with gas molecules. The electron confinement yields high gas amplification efficiency at short working distances and low gas pressures, facilitating high resolution imaging at low electron beam energies. Charging of insulating specimens is stabilized by positive ions produced in the gas ionization cascade. Furthermore, the signal to background level and bandwidth of this detector are superior to those of earlier generations of environmental secondary electron detectors. The combination of low vacuum, short working distance, and low beam energy is attractive to the semiconductor metrology industry, in particular, for critical dimension measurements on photolithographic masks.

  9. Two-stage gas amplifier for ultrahigh resolution low vacuum scanning electron microscopy

    SciTech Connect

    Thiel, B.L.; Toth, M.; Schroemges, R.P.M.; Scholtz, J.J.; Veen, G. van; Knowles, W.R.

    2006-03-15

    We describe a magnetic field assisted, two-stage secondary electron gas amplification process for low vacuum scanning electron microscopy. The field of an ultrahigh resolution magnetic immersion objective lens and the electric field of an annular electrode configuration partition the amplification volume into two regions in which the electric and magnetic fields are parallel and crossed, respectively. The fields confine secondary electrons to axial and radial oscillations within the detector volume, until all of the kinetic energy imparted by an anode is dissipated through inelastic collisions with gas molecules. The electron confinement yields high gas amplification efficiency at short working distances and low gas pressures, facilitating high resolution imaging at low electron beam energies. Charging of insulating specimens is stabilized by positive ions produced in the gas ionization cascade. Furthermore, the signal to background level and bandwidth of this detector are superior to those of earlier generations of environmental secondary electron detectors. The combination of low vacuum, short working distance, and low beam energy is attractive to the semiconductor metrology industry, in particular, for critical dimension measurements on photolithographic masks.

  10. End-wall boundary layer measurements in a two-stage fan

    NASA Technical Reports Server (NTRS)

    Ball, C. L.; Reid, L.; Schmidt, J. F.

    1983-01-01

    Detailed flow measurements made in the casing boundary layer of a two-stage transonic fan are summarized. These measurements were taken at a station upstream of the fan, between all blade rows, and downstream of the last row. Conventional boundary layer parameters were calculated from the measured data. A classical two dimensional casing boundary layer was measured at the fan inlet and extended inward to approximately 15 percent of span. A highly three dimensional boundary layer was measured at the exit of each blade row and extended inward to approximately 10 percent of span. The steep radial gradient of axial velocity noted at the exit of the rotors was reduced substantially as the flow passed through the stators. This reduced gradient is attributed to flow mixing. The amount of flow mixing was reflected in the radial redistribution of total temperature as the flow passed through the stators. The blockage factors calculated from the measured data show an increase in blockage across the rotors and a decrease across the stators. For this fan the calculated blockages for the second stage were essentially the same as those for the first stage.

  11. Characterisation of the current switch mechanism in two-stage wire array Z-pinches

    NASA Astrophysics Data System (ADS)

    Burdiak, G. C.; Lebedev, S. V.; Harvey-Thompson, A. J.; Hall, G. N.; Swadling, G. F.; Suzuki-Vidal, F.; Khoory, E.; Bland, S. N.; Pickworth, L.; de Grouchy, P.; Skidmore, J.; Suttle, L.; Waisman, E. M.

    2015-11-01

    In this paper, we describe the operation of a two-stage wire array z-pinch driven by the 1.4 MA, 240 ns rise-time Magpie pulsed-power device at Imperial College London. In this setup, an inverse wire array acts as a fast current switch, delivering a current pre-pulse into a cylindrical load wire array, before rapidly switching the majority of the generator current into the load after a 100-150 ns dwell time. A detailed analysis of the evolution of the load array during the pre-pulse is presented. Measurements of the load resistivity and energy deposition suggest significant bulk heating of the array mass occurs. The ˜5 kA pre-pulse delivers ˜0.8 J of energy to the load, leaving it in a mixed, predominantly liquid-vapour state. The main current switch occurs as the inverse array begins to explode and plasma expands into the load region. Electrical and imaging diagnostics indicate that the main current switch may evolve in part as a plasma flow switch, driven by the expansion of a magnetic cavity and plasma bubble along the length of the load array. Analysis of implosion trajectories suggests that approximately 1 MA switches into the load in 100 ns, corresponding to a doubling of the generator dI/dt. Potential scaling of the device to higher current machines is discussed.

  12. Detrend-free hemodynamic data assimilation of two-stage Kalman estimator.

    PubMed

    Zhenghui, Hu; Pengcheng, Shi

    2011-01-01

    Spurious temporal drift is abundant in fMRI data, and its removal is a critical preprocessing step in fMRI data assimilation due to the sparse nature and the complexity of the data. Conventional data-driven approaches rest upon specific assumptions of the drift structure and signal statistics, and may lead to inaccurate results. In this paper we present an approach to the assimilation of nonlinear hemodynamic system, with special attention on drift. By treating the drift variation as a random-walk process, the assimilation problem was translated into the identification of a nonlinear system in the presence of time varying bias. We developed two-stage unscented Kalman filter (UKF) to efficiently handle this problem. In this framework the assimilation can implement with original fMRI data without detrending preprocessing. The fMRI responses and drift were estimated simultaneously in an assimilation cycle. The efficacy of this approach is demonstrated in synthetic and real fMRI experiments. Results show that the joint estimation strategy produces more accurate estimation of physiological states, fMRI response and drift than separate processing due to no assumption of structure of the drift that is not available in fMRI data.

  13. Effect of evening primrose and fish oils on two stage skin carcinogenesis in mice.

    PubMed

    Ramesh, G; Das, U N

    1998-09-01

    The effect of fish oil (FO, given in the form of MaxEPA) rich in n-3 fatty acids and evening primrose oil (EPO) rich in n-6 fatty acids on two-stage skin carcinogenesis in mice was studied. Both FO and EPO inhibited the papilloma formation to a significant degree only during the promotion stage which was associated with an increase in lipid peroxidation. Both FO and EPO inhibited the binding of benzo(a)-pyrene to skin cell DNA suggesting that this could be one of the mechanism(s) by which these oils could be preventing papilloma development. Neither EPO nor FO influenced epidermal cell proliferation. In the FO group, LA (linoleic acid), AA (arachidonic acid) and DHA (docosahexaenoic acid) were increased, whereas in the EPO group a significant increase in the AA content was noted. No specific changes in the fatty acid pattern were observed in any of the groups that could be attributed to the papilloma incidence. These results suggest that FO and EPO can influence papilloma formation which can be attributed, at least in part, to their ability to prevent benzo(a)pyrene binding to DNA and to an increase the lipid peroxidation process.

  14. Catalytic two-stage coal hydrogenation process using extinction recycle of heavy liquid fraction

    DOEpatents

    MacArthur, J.B.; Comolli, A.G.; McLean, J.B.

    1989-10-17

    A process is described for catalytic two-stage hydrogenation and liquefaction of coal with selective extinction recycle of all heavy liquid fractions boiling above a distillation cut point of about 600--750 F to produce increased yields of low-boiling hydrocarbon liquid and gas products. In the process, the particulate coal feed is slurried with a process-derived liquid solvent normally boiling above about 650 F and fed into a first stage catalytic reaction zone operated at conditions which promote controlled rate liquefaction of the coal, while simultaneously hydrogenating the hydrocarbon recycle oils. The first stage reactor is maintained at 710--800 F temperature, 1,000--4,000 psig hydrogen partial pressure, and 10-90 lb/hr per ft[sup 3] catalyst space velocity. Partially hydrogenated material withdrawn from the first stage reaction zone is passed directly to the second stage catalytic reaction zone maintained at 760--860 F temperature for further hydrogenation and hydroconversion reactions. A 600--750 F[sup +] fraction containing 0--20 W % unreacted coal and ash solids is recycled to the coal slurrying step. If desired, the cut point lower boiling fraction can be further catalytically hydrotreated. By this process, the coal feed is successively catalytically hydrogenated and hydroconverted at selected conditions, to provide significantly increased yields of desirable low-boiling hydrocarbon liquid products and minimal production of hydrocarbon gases, and no net production of undesirable heavy oils and residuum materials. 2 figs.

  15. Catalytic two-stage coal hydrogenation process using extinction recycle of heavy liquid fraction

    DOEpatents

    MacArthur, James B.; Comolli, Alfred G.; McLean, Joseph B.

    1989-01-01

    A process for catalytic two-stage hydrogenation and liquefaction of coal with selective extinction recycle of all heavy liquid fractions boiling above a distillation cut point of about 600.degree.-750.degree. F. to produce increased yields of low-boiling hydrocarbon liquid and gas products. In the process, the particulate coal feed is slurried with a process-derived liquid solvent normally boiling above about 650.degree. F. and fed into a first stage catalytic reaction zone operated at conditions which promote controlled rate liquefaction of the coal, while simultaneously hydrogenating the hydrocarbon recycle oils. The first stage reactor is maintained at 710.degree.-800.degree. F. temperature, 1000-4000 psig hydrogen partial pressure, and 10-90 lb/hr per ft.sup.3 catalyst space velocity. Partially hydrogenated material withdrawn from the first stage reaction zone is passed directly to the second stage catalytic reaction zone maintained at 760.degree.-860.degree. F. temperature for further hydrogenation and hydroconversion reactions. A 600.degree.-750.degree. F..sup.+ fraction containing 0-20 W % unreacted coal and ash solids is recycled to the coal slurrying step. If desired, the cut point lower boiling fraction can be further catalytically hydrotreated. By this process, the coal feed is successively catalytically hydrogenated and hydroconverted at selected conditions, to provide significantly increased yields of desirable low-boiling hydrocarbon liquid products and minimal production of hydrocarbon gases, and no net production of undesirable heavy oils and residuum materials.

  16. Pressurization System Modeling for a Generic Bimese Two- Stage-to-Orbit Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Mazurkivich, Pete; Chandler, Frank; Nguyen, Han

    2005-01-01

    A pressurization system model was developed for a generic bimese Two-Stage-to-orbit Reusable Launch Vehicle using a cross-feed system and operating with densified propellants. The model was based on the pressurization system model for a crossfeed subscale water test article and was validated with test data obtained from the test article. The model consists of the liquid oxygen and liquid hydrogen pressurization models, each made up of two submodels, Booster and Orbiter tank pressurization models. The tanks are controlled within a 0.2-psi band and pressurized on the ground with ambient helium and autogenously in flight with gaseous oxygen and gaseous hydrogen. A 15-psi pressure difference is maintained between the Booster and Orbiter tanks to ensure crossfeed check valve closure before Booster separation. The analysis uses an ascent trajectory generated for a generic bimese vehicle and a tank configuration based on the Space Shuttle External Tank. It determines the flow rates required to pressurize the tanks on the ground and in flight, and demonstrates the model's capability to analyze the pressurization system performance of a full-scale bimese vehicle with densified propellants.

  17. Two-Stage Path Planning Approach for Designing Multiple Spacecraft Reconfiguration Maneuvers

    NASA Technical Reports Server (NTRS)

    Aoude, Georges S.; How, Jonathan P.; Garcia, Ian M.

    2007-01-01

    The paper presents a two-stage approach for designing optimal reconfiguration maneuvers for multiple spacecraft. These maneuvers involve well-coordinated and highly-coupled motions of the entire fleet of spacecraft while satisfying an arbitrary number of constraints. This problem is particularly difficult because of the nonlinearity of the attitude dynamics, the non-convexity of some of the constraints, and the coupling between the positions and attitudes of all spacecraft. As a result, the trajectory design must be solved as a single 6N DOF problem instead of N separate 6 DOF problems. The first stage of the solution approach quickly provides a feasible initial solution by solving a simplified version without differential constraints using a bi-directional Rapidly-exploring Random Tree (RRT) planner. A transition algorithm then augments this guess with feasible dynamics that are propagated from the beginning to the end of the trajectory. The resulting output is a feasible initial guess to the complete optimal control problem that is discretized in the second stage using a Gauss pseudospectral method (GPM) and solved using an off-the-shelf nonlinear solver. This paper also places emphasis on the importance of the initialization step in pseudospectral methods in order to decrease their computation times and enable the solution of a more complex class of problems. Several examples are presented and discussed.

  18. Efficient estimation in two-stage randomized clinical trials using ranked sets.

    PubMed

    Hossain, Syed Shahadat; Awan, Nabil

    2016-12-14

    Clinical trials designed for survival probability estimation of different treatment policies for chronic diseases like cancer, leukemia, and schizophrenia usually need randomization of treatments in two stages. Since complete remission is rare for these diseases, initially an induction therapy is given for patient's remission. Further treatment, which is often an expensive maintenance therapy, is administered only for the patients with remission. If the maintenance therapy is so expensive that the cost of the trial inflates, only a simple random sample of patients will be treated with the expensive maintenance due to budget constraint. In this article, we have implemented a design using ranked sets instead of simple randomization in the second stage and obtained an unbiased estimator of the overall survival distribution for a particular treatment combination. Through simulation studies under different conditions, we have found that the design we developed based on ranked sets gives an unbiased estimate of the population survival probability which is more efficient than the estimate obtained by the usual design.

  19. Retinal orientation and interactions in rhodopsin reveal a two-stage trigger mechanism for activation

    PubMed Central

    Kimata, Naoki; Pope, Andreyah; Eilers, Markus; Opefi, Chikwado A.; Ziliox, Martine; Hirshfeld, Amiram; Zaitseva, Ekaterina; Vogel, Reiner; Sheves, Mordechai; Reeves, Philip J.; Smith, Steven O.

    2016-01-01

    The 11-cis retinal chromophore is tightly packed within the interior of the visual receptor rhodopsin and isomerizes to the all-trans configuration following absorption of light. The mechanism by which this isomerization event drives the outward rotation of transmembrane helix H6, a hallmark of activated G protein-coupled receptors, is not well established. To address this question, we use solid-state NMR and FTIR spectroscopy to define the orientation and interactions of the retinal chromophore in the active metarhodopsin II intermediate. Here we show that isomerization of the 11-cis retinal chromophore generates strong steric interactions between its β-ionone ring and transmembrane helices H5 and H6, while deprotonation of its protonated Schiff's base triggers the rearrangement of the hydrogen-bonding network involving residues on H6 and within the second extracellular loop. We integrate these observations with previous structural and functional studies to propose a two-stage mechanism for rhodopsin activation. PMID:27585742

  20. Prediction of syngas quality for two-stage gasification of selected waste feedstocks.

    PubMed

    De Filippis, Paolo; Borgianni, Carlo; Paolucci, Martino; Pochetti, Fausto

    2004-01-01

    This paper compares the syngas produced from methane with the syngas obtained from the gasification, in a two-stage reactor, of various waste feedstocks. The syngas composition and the gasification conditions were simulated using a simple thermodynamic model. The waste feedstocks considered are: landfill gas, waste oil, municipal solid waste (MSW) typical of a low-income country, the same MSW blended with landfill gas, refuse derived fuel (RDF) made from the same MSW, the same RDF blended with waste oil and a MSW typical of a high-income country. Energy content, the sum of H2 and CO gas percentages, and the ratio of H2 to CO are considered as measures of syngas quality. The simulation shows that landfill gas gives the best results in terms of both H2+CO and H2/CO, and that the MSW of low-income countries can be expected to provide inferior syngas on all three quality measures. Co-gasification of the MSW from low-income countries with landfill gas, and the mixture of waste oil with RDF from low-income MSW are considered as options to improve gas quality.

  1. OBSERVATIONS OF A TWO-STAGE SOLAR ERUPTIVE EVENT (SEE): EVIDENCE FOR SECONDARY HEATING

    SciTech Connect

    Su Yang; Dennis, Brian R.; Holman, Gordon D.; Wang, Tongjiang; Chamberlin, Phillip C.; Savage, Sabrina; Veronig, Astrid

    2012-02-10

    We present RHESSI, SDO/AIA, SOHO/LASCO, STEREO, and GOES observations of a partially occulted solar eruptive event that occurred at the southwest limb on 2011 March 8. The GOES X-ray light curve shows two peaks separated by almost 2 hr that we interpret as two stages of a single event associated with the delayed eruption of a coronal mass ejection (CME). A hot flux rope formed during the first stage and continued expanding and rising throughout the event. The speed of the flux rope decreased from {approx}120 to 14 km s{sup -1} during the decay phase of the first stage and increased again during the second stage to become the CME with a speed of {approx}516 km s{sup -1}. RHESSI and GOES data analyses show that the plasma temperature reached over 20 MK in the first stage, then decreased to {approx}10 MK and increased to 15 MK in the second stage. This event provides clear evidence for a secondary heating phase. The enhanced EUV and X-ray emission came from the high corona ({approx}60 arcsec above the limb) in the second stage, {approx}40 arcsec higher than the site of the initial flare emission. STEREO-A on-disk observations indicate that the post-flare loops during this stage were of larger scale sizes and spatially distinct from those in the first stage.

  2. Observations of a Two-Stage Solar Eruptive Event (SEE): Evidence for Secondary Heating

    NASA Technical Reports Server (NTRS)

    Su, Yang; Dennis, Brian R.; Holman, Gordon D.; Wang, Tongjiang; Chamberlin, Phillip C.; Savage, Sabrina; Veronig, Astrid

    2012-01-01

    We present RHESSI, SDO/AIA, SOHO/LASCO, STEREO, and GOES observations of a partially occulted solar eruptive event (SEE) that occurred at the South-West limb on 8 March, 2011. The GOES X-ray light curve shows two peaks separated by almost two hours that we interpret as two stages of a single event associated with the delayed eruption of a CME. A hot flux rope formed during the first stage and continued expanding and rising throughout the event. The speed of the flux rope decreased from approx.120 to 14 km/s during the decay phase of the first stage and increased again during the second stage to become the CME with a speed of approx.516 km/s. RHESSI and GOES data analyses show that the plasma temperature reached over 20 MK in the first stage, then decreased to approx.10 MK and increased to 15 MK in the second stage. This event provides clear evidence for a secondary heating phase. The enhanced EUV and X-ray emission came from the high corona ( approx.60 arcsec above the limb) in the second stage, approx.40 arcsec higher than the site of the initial flare emission. STEREO-A on-disk observations indicate that the post-flare loops during this stage were of larger scale sizes and spatially distinct from those in the first stage.

  3. Two stages catalytic pyrolysis of refuse derived fuel: production of biofuel via syncrude.

    PubMed

    Miskolczi, N; Buyong, F; Angyal, A; Williams, P T; Bartha, L

    2010-11-01

    Thermo-catalytic pyrolysis of refuse derived fuels with different catalysts had been conducted in a two stages process due to its important potential value as fuel. The first stage was a pure thermal pyrolysis in a horizontal tubular reactor with feed rate of 0.5kg hourly. The second stage was a semi-batch process in the presence of catalysts. Results showed that the tested catalysts significantly have affected the quantity of products. E.g. gas yield could be increased with 350% related to the catalyst free case using ZSM-5, while that of pyrolytic oil was 115% over Y-zeolite. Gases consisted of mainly CO and CO(2) obtained from the tubular reactor, while dominantly hydrocarbons from the second stage. Ni-Mo-catalyst and Co-Mo-catalyst had shown activity in pyrolytic oil upgrading via in-situ hydrogenation-dehydrogenation reactions. Sulphur, nitrogen and chlorine level in pyrolytic oils could be significantly declined by using of catalysts.

  4. Procedure for Optimum Design of a Two-Stage Spur Gear System

    NASA Astrophysics Data System (ADS)

    Abuid, Bader Ahmed; Ameen, Yahya Muhammed

    In this paper, an optimum design of a two-stage spur gear system is performed. The optimization is based on a multicriterion technique consisting of a Min-Max method combined with a direct search technique. The optimum design includes the minimization of seven objective functions. They are the volume of gears, the center distance and five dynamic factors in the input shaft, first-teeth meshing, intermediate shaft, second meshing and the output shaft. The dynamic factors are estimated using a dynamic model of twelve degrees of freedom. The objective functions are governed by eleven design variables, chosen to be the number of teeth and face width of the pinion of each stage, stiffness of the input, intermediate, and output shafts and the inertia of the four gears of the mechanism. The developed optimum design is found to give compact-gear system with quiet running (minimum dynamic factors) compared with the classical design. The angle between the power transmitting directions is found to have an important role on the objective functions and the optimum design. A value of 180° for this angle is found to be the optimal for all functions.

  5. Two-stage, low noise advanced technology fan. 4: Aerodynamic final report

    NASA Technical Reports Server (NTRS)

    Harley, K. G.; Keenan, M. J.

    1975-01-01

    A two-stage research fan was tested to provide technology for designing a turbofan engine for an advanced, long range commercial transport having a cruise Mach number of 0.85 -0.9 and a noise level 20 EPNdB below current requirements. The fan design tip speed was 365.8m/sec (1200ft/sec);the hub/tip ratio was 0.4; the design pressure ratio was 1.9; and the design specific flow was 209.2 kg/sec/sq m(42.85lbm/sec/sq ft). Two fan-versions were tested: a baseline configuration, and an acoustically treated configuration with a sonic inlet device. The baseline version was tested with uniform inlet flow and with tip-radial and hub-radial inlet flow distortions. The baseline fan with uniform inlet flow attained an efficiency of 86.4% at design speed, but the stall margin was low. Tip-radial distortion increased stall margin 4 percentage points at design speed and reduced peak efficiency one percentage point. Hub-radial distortion decreased stall margin 4 percentage points at all speeds and reduced peak efficiency at design speed 8 percentage points. At design speed, the sonic inlet in the cruise position reduced stall margin one percentage point and efficiency 1.5 to 4.5 percentage points. The sonic inlet in the approach position reduced stall margin 2 percentage points.

  6. Comparing regression methods for the two-stage clonal expansion model of carcinogenesis.

    PubMed

    Kaiser, J C; Heidenreich, W F

    2004-11-15

    In the statistical analysis of cohort data with risk estimation models, both Poisson and individual likelihood regressions are widely used methods of parameter estimation. In this paper, their performance has been tested with the biologically motivated two-stage clonal expansion (TSCE) model of carcinogenesis. To exclude inevitable uncertainties of existing data, cohorts with simple individual exposure history have been created by Monte Carlo simulation. To generate some similar properties of atomic bomb survivors and radon-exposed mine workers, both acute and protracted exposure patterns have been generated. Then the capacity of the two regression methods has been compared to retrieve a priori known model parameters from the simulated cohort data. For simple models with smooth hazard functions, the parameter estimates from both methods come close to their true values. However, for models with strongly discontinuous functions which are generated by the cell mutation process of transformation, the Poisson regression method fails to produce reliable estimates. This behaviour is explained by the construction of class averages during data stratification. Thereby, some indispensable information on the individual exposure history was destroyed. It could not be repaired by countermeasures such as the refinement of Poisson classes or a more adequate choice of Poisson groups. Although this choice might still exist we were unable to discover it. In contrast to this, the individual likelihood regression technique was found to work reliably for all considered versions of the TSCE model.

  7. A Two-Stage-to-Orbit Spaceplane Concept With Growth Potential

    NASA Technical Reports Server (NTRS)

    Mehta, Unmeel B.; Bowles, Jeffrey V.

    2001-01-01

    A two-stage-to-orbit (TSTO) spaceplane concept developed in 1993 is revisited, and new information is provided to assist in the development of the next-generation space transportation vehicles. The design philosophy, TSTO spaceplane concept, and the design method are briefly described. A trade study between cold and hot structures leads to the choice of cold structures with external thermal protection systems. The optimal Mach number for staging the second stage of the TSTO spaceplane (with air-breathing propulsion on the first stage) is 10, based on life-cycle cost analysis. The performance and specification of a prototype/experimental (P/X) TSTO spaceplane with a turbo/ram/scramjet propulsion system and built-in growth potential are presented and discussed. The internal rate of return on investment is the highest for the proposed TSTO spaceplane, vis-A-vis a single-stage-to-orbit (SSTO) rocket vehicle and a TSTO spaceplane without built-in growth. Additional growth potentials for the proposed spaceplane are suggested. This spaceplane can substantially decrease access-to-space cost and risk, and increase safety and reliability in the near term It can be a serious candidate for the next-generation space transportation system.

  8. Two-Stage Adaptive Cutoff (TACO) Design for Building and Validating a Prognostic Biomarker Signature

    PubMed Central

    Polley, Mei-Yin C.; Polley, Eric C.; Huang, Erich P.; Freidlin, Boris; Simon, Richard

    2014-01-01

    Cancer biomarkers are frequently evaluated using archived specimens collected from previously conducted therapeutic trials. Routine collection and banking of high quality specimens is an expensive and time-consuming process. Therefore, care should be taken to preserve these precious resources. Here we propose a novel two-stage adaptive cutoff (TACO) design that affords the possibility to stop the biomarker study early if an evaluation of the model performance is unsatisfactory at an early stage, thereby allowing one to preserve the remaining specimens for future research. In addition, our design integrates important elements necessary to meet statistical rigor and practical demands for developing and validating a prognostic biomarker signature, including maintaining strict separation between the datasets used to build and evaluate the model and producing a locked-down signature to facilitate future validation. We conduct simulation studies to evaluate the operating characteristics of the proposed design. We show that under the null hypothesis when the model performance is deemed undesirable, the proposed design maintains type I error at the nominal level, has high probabilities of terminating the study early, and results in substantial savings in specimens. Under the alternative hypothesis, power is generally high when the total sample size and the targeted degree of improvement in prediction accuracy are reasonably large. We illustrate the use of the procedure with a dataset in patients with diffuse large-B-cell lymphoma. The practical aspects of the proposed designs are discussed. PMID:25263614

  9. Concentration and purification of chromate from electroplating wastewater by two-stage electrodialysis processes.

    PubMed

    Chen, Shiao-Shing; Li, Chi-Wang; Hsu, Hong-Der; Lee, Po-Ching; Chang, Yu-Min; Yang, Chia-Hao

    2009-01-30

    A designed two-stage electrodialysis system is proposed to concentrate and purify chromate from a low pH electroplating wastewater using monovalent selective electrodialysis membranes. With low pH of the raw water (pH 2.2) in the first stage, chromate was presented as HCrO(4)(-) and monovalent ions (HCrO(4)(-), NH(2)SO(3)(-), Na(+) and Cl(-)) were able to pass through the membrane thus chromate was concentrated up to 191%. Higher current density, flowrate and more membrane area all increased the chromium recovery. When pH was adjusted to 8.5 before entering the second stage, the chromate species was presented as divalent CrO(4)(2-) and retained in the concentrated stream, and the rest monovalent ions (NH(2)SO(3)(-), Na(+) and Cl(-)) were separated by passing through the membrane. For example, 45% of the chlorides were separated in this study. The separation efficiencies in the second stage were also increased when the current density, flowrate and membrane area were increased. Electron Spectroscopy for Chemical Analysis was used to examine the surface chromate species for stage 1, and anion exchange membrane showed more chromate fouling comparing to cation exchange membrane due to more adsorption and concentration polarization effects for the anion exchange membrane.

  10. Treatment of anaerobically digested dairy manure in a two-stage biofiltration system.

    PubMed

    Xia, Mengjing; Tao, Wendong; Wang, Ziyuan; Pei, Yuansheng

    2012-01-01

    High concentrations of ammonium and phosphate present a challenge to cost-effective treatment of anaerobically digested dairy manure. This study investigated the efficacy of a two-stage biofiltration system for passive treatment of digested dairy manure. The first stage pebble filters were batch loaded. When the slurry-like digested dairy manure was retained on pebble beds, soluble contaminants were removed before liquid infiltrated over 8-17 days. The pebble filters removed 70% of soluble chemical oxygen demand, 71% of soluble biochemical oxygen demand, 75% of ammonium, and 68% of orthophosphate. Nitrogen removal was attributed to the conventional nitrification - denitrification process and novel nitritation - anammox process. Aerobic ammonium oxidizing and anammox bacteria accounted for 25 and 23% of all bacteria, respectively, in the filtrate of the pebble filters. The longer it took for filtration, the greater the removal efficiency of soluble contaminants. The second stage sand filters had removal efficiencies of 17% for soluble chemical oxygen demand, 45% for soluble biochemical oxygen demand, 43% for ammonium, and 16% for orthophosphate during batch operations at a hydraulic retention time of 7 days. Aerobic ammonium oxidation and anammox were primarily responsible for nitrogen removal in the sand filters. Vegetation made an insignificant difference in treatment performance of the sand filters.

  11. Antioxidant activity and total phenolic content of Moringa oleifera leaves in two stages of maturity.

    PubMed

    Sreelatha, S; Padma, P R

    2009-12-01

    Antioxidants play an important role in inhibiting and scavenging free radicals, thus providing protection to human against infections and degenerative diseases. Current research is now directed towards natural antioxidants originated from plants due to safe therapeutics. Moringa oleifera is used in Indian traditional medicine for a wide range of various ailments. To understand the mechanism of pharmacological actions, antioxidant properties of the Moringa oleifera leaf extracts were tested in two stages of maturity using standard in vitro models. The successive aqueous extract of Moringa oleifera exhibited strong scavenging effect on 2, 2-diphenyl-2-picryl hydrazyl (DPPH) free radical, superoxide, nitric oxide radical and inhibition of lipid per oxidation. The free radical scavenging effect of Moringa oleifera leaf extract was comparable with that of the reference antioxidants. The data obtained in the present study suggests that the extracts of Moringa oleifera both mature and tender leaves have potent antioxidant activity against free radicals, prevent oxidative damage to major biomolecules and afford significant protection against oxidative damage.

  12. Development of advanced heat pump. Part 2: Preliminary test of two-stage compression heat pump

    NASA Astrophysics Data System (ADS)

    Iwatsubo, Tetsushiro; Saikawa, Michinori; Hamamatsu, Teruhide

    1988-03-01

    A heat pump driven by electricity is one of the excellent electricity utilization systems and is promoted to be widely used. An advanced heat pump has been investigated to enlarge its applications in the field of hot water supply for domestic use which will be competitive with city gas and air conditioning in large scale buildings. An experimental unit with two-stage compression system was designed, which has the multi-function of air conditioning and hot water supply, and the trial system was fabricated. In the design, followings were considered; cooperative operations of two compressors by inverter driving, the temperature conditions of both the air for the air conditioning and the heat source, additional setting of the intermediate heat exchanger. The test operation was carried out with checking the start up procedure, the control sequence and so on. The probability of five operation modes: cooling, heating, hot water supply, cooling/hot water supply, and heating/hot water supply, were confirmed. In the mode of heating/hot water supply the hot water temperature was increased to 65 C, the excellent performance in hot water supply was demonstrated.

  13. Optimum performance analysis of a two-stage irreversible magnetization Brayton refrigeration system

    NASA Astrophysics Data System (ADS)

    Zhang, Yue; Lin, Bihong; Chen, Jincan

    2006-10-01

    A two-stage magnetization Brayton refrigeration cycle model using a paramagnetic material as the working substance is established, in which the regeneration and the irreversibility in the adiabatic processes are taken into account. On the basis of the thermodynamic properties of a paramagnetic material, the expressions of some important parameters such as the coefficient of performance, refrigeration load and work input are derived and used to analyse the performance characteristics of the refrigeration cycle. The influence of the inter-magnetization process, irreversibility in the adiabatic processes and regeneration on the performance of the cycle is discussed in detail. The advantage of adding the inter-magnetization process is expounded and the magnetic field ratio related to the inter-magnetization process is optimized. Moreover, the optimal values of the temperatures of the working substance at different state points and the optimally operating region of the cycle are determined. The results obtained here are compared with those derived from some relevant magnetic Brayton refrigeration cycles, and consequently, some significant conclusions are obtained.

  14. A cooperation model based on CVaR measure for a two-stage supply chain

    NASA Astrophysics Data System (ADS)

    Xu, Xinsheng; Meng, Zhiqing; Shen, Rui

    2015-07-01

    In this paper, we introduce a cooperation model (CM) for the two-stage supply chain consisting of a manufacturer and a retailer. In this model, it is supposed that the objective of the manufacturer is to maximise his/her profit while the objective of the retailer is to minimise his/her CVaR while controlling the risk originating from fluctuation in market demand. In reality, the manufacturer and the retailer would like to choose their own decisions as to wholesale price and order quantity to optimise their own objectives, resulting the fact that the expected decision of the manufacturer and that of the retailer may conflict with each other. Then, to achieve cooperation, the manufacturer and the retailer both need to give some concessions. The proposed model aims to coordinate the decisions of the manufacturer and the retailer, and balance the concessions of the two in their cooperation. We introduce an s* - optimal equilibrium solution in this model, which can decide the minimum concession that the manufacturer and the retailer need to give for their cooperation, and prove that the s* - optimal equilibrium solution can be obtained by solving a goal programming problem. Further, the case of different concessions made by the manufacturer and the retailer is also discussed. Numerical results show that the CM is efficient in dealing with the cooperations between the supplier and the retailer.

  15. Removal of cesium from simulated liquid waste with countercurrent two-stage adsorption followed by microfiltration.

    PubMed

    Han, Fei; Zhang, Guang-Hui; Gu, Ping

    2012-07-30

    Copper ferrocyanide (CuFC) was used as an adsorbent to remove cesium. Jar test results showed that the adsorption capacity of CuFC was better than that of potassium zinc hexacyanoferrate. Lab-scale tests were performed by an adsorption-microfiltration process, and the mean decontamination factor (DF) was 463 when the initial cesium concentration was 101.3μg/L, the dosage of CuFC was 40mg/L and the adsorption time was 20min. The cesium concentration in the effluent continuously decreased with the operation time, which indicated that the used adsorbent retained its adsorption capacity. To use this capacity, experiments on a countercurrent two-stage adsorption (CTA)-microfiltration (MF) process were carried out with CuFC adsorption combined with membrane separation. A calculation method for determining the cesium concentration in the effluent was given, and batch tests in a pressure cup were performed to verify the calculated method. The results showed that the experimental values fitted well with the calculated values in the CTA-MF process. The mean DF was 1123 when the dilution factor was 0.4, the initial cesium concentration was 98.75μg/L and the dosage of CuFC and adsorption time were the same as those used in the lab-scale test. The DF obtained by CTA-MF process was more than three times higher than the single-stage adsorption in the jar test.

  16. Two-stage acceleration of protons from relativistic laser-solid interaction

    SciTech Connect

    Liu Jinlu; Sheng, Z. M.; Zheng, J.; Wang, W. M.; Yu, M. Y.; Liu, C. S.; Zhang, J.

    2012-12-21

    A two-stage proton acceleration scheme using present-day intense lasers and a unique target design is proposed. The target system consists of a hollow cylinder, inside which is a hollow cone, which is followed by the main target with a flat front and dish-like flared rear surface. At the center of the latter is a tapered proton layer, which is surrounded by outer proton layers at an angle to it. In the first acceleration stage, protons in both layers are accelerated by target normal sheath acceleration. The center-layer protons are accelerated forward along the axis and the side protons are accelerated and focused towards them. As a result, the side-layer protons radially compress as well as axially further accelerate the front part of the accelerating center-layer protons in the second stage, which are also radially confined and guided by the field of the fast electrons surrounding them. Two-dimensional particle-incell simulation shows that a 79fs 8.5 Multiplication-Sign 10{sup 20} W/cm{sup 2} laser pulse can produce a proton bunch with {approx} 267MeV maximum energy and {approx} 9.5% energy spread, which may find many applications, including cancer therapy.

  17. The role of the upper sample size limit in two-stage bioequivalence designs.

    PubMed

    Karalis, Vangelis

    2013-11-01

    Two-stage designs (TSDs) are currently recommended by the regulatory authorities for bioequivalence (BE) assessment. The TSDs presented until now rely on an assumed geometric mean ratio (GMR) value of the BE metric in stage I in order to avoid inflation of type I error. In contrast, this work proposes a more realistic TSD design where sample re-estimation relies not only on the variability of stage I, but also on the observed GMR. In these cases, an upper sample size limit (UL) is introduced in order to prevent inflation of type I error. The aim of this study is to unveil the impact of UL on two TSD bioequivalence approaches which are based entirely on the interim results. Monte Carlo simulations were used to investigate several different scenarios of UL levels, within-subject variability, different starting number of subjects, and GMR. The use of UL leads to no inflation of type I error. As UL values increase, the % probability of declaring BE becomes higher. The starting sample size and the variability of the study affect type I error. Increased UL levels result in higher total sample sizes of the TSD which are more pronounced for highly variable drugs.

  18. Two-stage revision of hip prosthesis infection using a hip spacer with stabilising proximal cementation.

    PubMed

    Gil Gonzalez, Sergi; Marqués López, Fernando; Rigol Ramon, Pau; Mestre Cortadellas, Carlos; Cáceres Palou, Enric; León García, Alfonso

    2010-01-01

    Two-stage revision hip arthroplasty for infection using an antibiotic-loaded cement spacer has been used frequently with good results. However, spacer instability is also frequent. Proximal cementation of the spacer could avoid spacer dislocation. We retrospectively assessed 35 patients in whom a 2-stage revision hip arthroplasty for infection was carried out using an antibiotic-loaded cement spacer with gentamicin (Spacer-G) in which the spacer was proximally cemented in 16 patients. The mean follow-up was 32 months. We assessed spacer stability and infection elimination. There were 8 spacer dislocations (22.9%), 5 in hips without proximal cementation and 2 in hips with proximal cementation (p>0.05). There was no fracture in any hip. Reinfection occurred in 5 hips (14.3%), in 3 with the same microorganism, while 2 had a different microorganism. Our results indicate that the proximal cementation of the spacer prevents its dislocation. Infection was eliminated in 86% of the hips.

  19. A Two-Stage Model for Lipid Modulation of the Activity of Integral Membrane Proteins

    PubMed Central

    Dodes Traian, Martín M.; Cattoni, Diego I.; Levi, Valeria; González Flecha, F. Luis

    2012-01-01

    Lipid-protein interactions play an essential role in the regulation of biological function of integral membrane proteins; however, the underlying molecular mechanisms are not fully understood. Here we explore the modulation by phospholipids of the enzymatic activity of the plasma membrane calcium pump reconstituted in detergent-phospholipid mixed micelles of variable composition. The presence of increasing quantities of phospholipids in the micelles produced a cooperative increase in the ATPase activity of the enzyme. This activation effect was reversible and depended on the phospholipid/detergent ratio and not on the total lipid concentration. Enzyme activation was accompanied by a small structural change at the transmembrane domain reported by 1-aniline-8-naphtalenesulfonate fluorescence. In addition, the composition of the amphipilic environment sensed by the protein was evaluated by measuring the relative affinity of the assayed phospholipid for the transmembrane surface of the protein. The obtained results allow us to postulate a two-stage mechanistic model explaining the modulation of protein activity based on the exchange among non-structural amphiphiles at the hydrophobic transmembrane surface, and a lipid-induced conformational change. The model allowed to obtain a cooperativity coefficient reporting on the efficiency of the transduction step between lipid adsorption and catalytic site activation. This model can be easily applied to other phospholipid/detergent mixtures as well to other membrane proteins. The systematic quantitative evaluation of these systems could contribute to gain insight into the structure-activity relationships between proteins and lipids in biological membranes. PMID:22723977

  20. Payload Performance Analysis for a Reusable Two-Stage-to-Orbit Vehicle

    NASA Technical Reports Server (NTRS)

    Tartabini, Paul V.; Beaty, James R.; Lepsch, Roger A.; Gilbert, Michael G.

    2015-01-01

    This paper investigates a unique approach in the development of a reusable launch vehicle where, instead of designing the vehicle to be reusable from its inception, as was done for the Space Shuttle, an expendable two stage launch vehicle is evolved over time into a reusable launch vehicle. To accomplish this objective, each stage is made reusable by adding the systems necessary to perform functions such as thermal protection and landing, without significantly altering the primary subsystems and outer mold line of the original expendable vehicle. In addition, some of the propellant normally used for ascent is used instead for additional propulsive maneuvers after staging in order to return both stages to the launch site, keep loads within acceptable limits and perform a soft landing. This paper presents a performance analysis that was performed to investigate the feasibility of this approach by quantifying the reduction in payload capability of the original expendable launch vehicle after accounting for the mass additions, trajectory changes and increased propellant requirements necessary for reusability. Results show that it is feasible to return both stages to the launch site with a positive payload capability equal to approximately 50 percent of an equivalent expendable launch vehicle. Further discussion examines the ability to return a crew/cargo capsule to the launch site and presents technical challenges that would have to be overcome.

  1. Two-stage Framework for a Topology-Based Projection and Visualization of Classified Document Collections

    SciTech Connect

    Oesterling, Patrick; Scheuermann, Gerik; Teresniak, Sven; Heyer, Gerhard; Koch, Steffen; Ertl, Thomas; Weber, Gunther H.

    2010-07-19

    During the last decades, electronic textual information has become the world's largest and most important information source available. People have added a variety of daily newspapers, books, scientific and governmental publications, blogs and private messages to this wellspring of endless information and knowledge. Since neither the existing nor the new information can be read in its entirety, computers are used to extract and visualize meaningful or interesting topics and documents from this huge information clutter. In this paper, we extend, improve and combine existing individual approaches into an overall framework that supports topological analysis of high dimensional document point clouds given by the well-known tf-idf document-term weighting method. We show that traditional distance-based approaches fail in very high dimensional spaces, and we describe an improved two-stage method for topology-based projections from the original high dimensional information space to both two dimensional (2-D) and three dimensional (3-D) visualizations. To show the accuracy and usability of this framework, we compare it to methods introduced recently and apply it to complex document and patent collections.

  2. Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins.

    PubMed

    Huismans, Ritske; Beaumont, Christopher

    2011-05-05

    Uniform lithospheric extension predicts basic properties of non-volcanic rifted margins but fails to explain other important characteristics. Significant discrepancies are observed at 'type I' margins (such as the Iberia-Newfoundland conjugates), where large tracts of continental mantle lithosphere are exposed at the sea floor, and 'type II' margins (such as some ultrawide central South Atlantic margins), where thin continental crust spans wide regions below which continental lower crust and mantle lithosphere have apparently been removed. Neither corresponds to uniform extension. Instead, either crust or mantle lithosphere has been preferentially removed. Using dynamical models, we demonstrate that these margins are opposite end members: in type I, depth-dependent extension results in crustal-necking breakup before mantle-lithosphere breakup and in type II, the converse is true. These two-layer, two-stage breakup behaviours explain the discrepancies and have implications for the styles of the associated sedimentary basins. Laterally flowing lower-mantle cratonic lithosphere may underplate some type II margins, thereby contributing to their anomalous characteristics.

  3. Two-stage sparse coding of region covariance via Log-Euclidean kernels to detect saliency.

    PubMed

    Zhang, Ying-Ying; Yang, Cai; Zhang, Ping

    2017-05-01

    In this paper, we present a novel bottom-up saliency detection algorithm from the perspective of covariance matrices on a Riemannian manifold. Each superpixel is described by a region covariance matrix on Riemannian Manifolds. We carry out a two-stage sparse coding scheme via Log-Euclidean kernels to extract salient objects efficiently. In the first stage, given background dictionary on image borders, sparse coding of each region covariance via Log-Euclidean kernels is performed. The reconstruction error on the background dictionary is regarded as the initial saliency of each superpixel. In the second stage, an improvement of the initial result is achieved by calculating reconstruction errors of the superpixels on foreground dictionary, which is extracted from the first stage saliency map. The sparse coding in the second stage is similar to the first stage, but is able to effectively highlight the salient objects uniformly from the background. Finally, three post-processing methods-highlight-inhibition function, context-based saliency weighting, and the graph cut-are adopted to further refine the saliency map. Experiments on four public benchmark datasets show that the proposed algorithm outperforms the state-of-the-art methods in terms of precision, recall and mean absolute error, and demonstrate the robustness and efficiency of the proposed method.

  4. Developments in laser wakefield accelerators: From single-stage to two-stage

    NASA Astrophysics Data System (ADS)

    Li, Wen-Tao; Wang, Wen-Tao; Liu, Jian-Sheng; Wang, Cheng; Zhang, Zhi-Jun; Qi, Rong; Yu, Chang-Hai; Li, Ru-Xin; Xu, Zhi-Zhan

    2015-01-01

    Laser wakefield accelerators (LWFAs) are compact accelerators which can produce femtosecond high-energy electron beams on a much smaller scale than the conventional radiofrequency accelerators. It is attributed to their high acceleration gradient which is about 3 orders of magnitude larger than the traditional ones. The past decade has witnessed the major breakthroughs and progress in developing the laser wakfield accelerators. To achieve the LWFAs suitable for applications, more and more attention has been paid to optimize the LWFAs for high-quality electron beams. A single-staged LWFA does not favor generating controllable electron beams beyond 1 GeV since electron injection and acceleration are coupled and cannot be independently controlled. Staged LWFAs provide a promising route to overcome this disadvantage by decoupling injection from acceleration and thus the electron-beam quality as well as the stability can be greatly improved. This paper provides an overview of the physical conceptions of the LWFA, as well as the major breakthroughs and progress in developing LWFAs from single-stage to two-stage LWFAs. Project supported by the National Natural Science Foundation of China (Grant Nos. 11127901, 11425418, and 61221064), the National Basic Research Program of China (Grant No. 2011CB808100), and the Science and Technology Talent Project of Shanghai City, China (Grant Nos. 12XD1405200 and 12ZR1451700).

  5. Transitional field behaviour from Southern Hemisphere lavas Evidence for two-stage reversals of the geodynamo

    NASA Astrophysics Data System (ADS)

    Hoffman, K. A.

    1986-03-01

    Palaeomagnetic records from Australasian basalts provide a rare view of transitional field behavior, as seen from mid-southern latitudes. These data suggest that a geomagnetic reversal is accomplished in two steps, separated by an interval of relative dynamo quiescence. A potentially long-lived field configuration, developed early, is observed to be the 'stepping stone' from which both successful and unsuccessful reversal attempts are made. Several aborted attempts involving the same intermediate field geometry may precede an actual polarity transition.

  6. Effect of two-stage coagulant addition on coagulation-ultrafiltration process for treatment of humic-rich water.

    PubMed

    Liu, Ting; Chen, Zhong-lin; Yu, Wen-zheng; Shen, Ji-min; Gregory, John

    2011-08-01

    A novel two-stage coagulant addition strategy applied in a coagulation-ultrafiltration (UF) process for treatment of humic-rich water at neutral pH was investigated in this study. When aluminum sulfate (alum) doses were set at a ratio of 3:1 added during rapid mix stage and half way through flocculation stage, the integrated process of two-stage alum addition achieved almost the same organic matter removal as that of conventional one-stage alum addition at the same overall dose. Whereas membrane fouling could be effectively mitigated by the two-stage addition exhibited by trans-membrane pressure (TMP) developments. The TMP developments were found to be primarily attributed to external fouling on membrane surface, which was closely associated with floc characteristics. The results of jar tests indicated that the average size of flocs formed in two-stage addition mode roughly reached one half larger than that in one-stage addition mode, which implied a beneficial effect on membrane fouling reduction. Moreover, the flocs with more irregular structure and lower effective density resulted from the two-stage alum addition, which caused higher porosity of cake layer formed by such flocs on membrane surface. Microscopic observations of membrane surface demonstrated that internal fouling in membrane pores could be also remarkably limited by two-stage alum addition. It is likely that the freshly formed hydroxide precipitates were distinct in surface characteristics from the aged precipitates due to formation of more active groups or adsorption of more labile aluminum species. Consequently, the flocs could further connect and aggregate to contribute to preferable properties for filtration performance of the coagulation-UF process. As a simple and efficient approach, two-stage coagulant addition strategy could have great practical significance in coagulation-membrane processes.

  7. Two-Stage Acceleration Mechanism for Impulsive Solar Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Zhang, T.; Wu, S.; Tan, A.

    2006-12-01

    Two distinct classes of impulsive and gradual solar energetic particle events have been recognized (Reames, ApJ, 571, L63, 2002). The impulsive events are characterized by 1) abundance enhancements of 3He/4He by a factor of ~ 104, Fe/O by a factor of ~ 10 in Fe/O, ^{22}Ne/20Ne by a factor of ~ 2-3, and (Z > 50)/O by a factor of ~ 102 -104, 2) high charge states of ions, 3) short durations (a few minutes to several hours), 4) small but frequently occurred events ( ~ 1000 per year), and 5) type-III radio bursts. The gradual events are characterized by 1) coronal mass ejection associations, 2) normal abundances and charge states of ions, 3) long durations (several hours to days), 4) large but rarely occurred events (~ 10 per year), and 5) type-I, IV radio bursts. Some solar gradual events can be superhot with temperature up to ~ 40 MK and contain both impulsive and gradual phases, so that these events have the features of both the impulsive and gradual events such as the RHESSI observed 2002 July 23 event (Lin et al., ApJ, 595, L69, 2003). Based on Cartwright and Mogro-Campero (ApJ, 177, L43, 1972) scenario and Fisk (ApJ, 224, 1048, 1978) efforts, Zhang (ApJ, 449, 916, 1995; ApJ, 518, 954, 1999) developed a complete two-stage acceleration model for solar impulsive or 3He-rich events. Plasma waves with frequency close to the harmonics of the 3He- cyclotron frequency efficiently heat 3He and heavy ions with appropriate charge states through the harmonic resonances and electrons through Landau resonances. The preheating of ions significantly increases the number of them that are injected into the flare-acceleration processes, and therefore lead to the enhancements of the ions in solar energetic particle events. The two-stage acceleration model has self- consistently explained various aspects of accelerations of ions and electrons in solar 3He-rich events (Zhang, JGR, 108A, SSH6Z, 2003; ApJ, 617, L77, 2004; Zhang and Wang, ApJ, 588, L57, 2003; ApJ, 613, L165, 2004; Zhang

  8. Simulation-based medical teaching and learning.

    PubMed

    Al-Elq, Abdulmohsen H

    2010-01-01

    One of the most important steps in curriculum development is the introduction of simulation- based medical teaching and learning. Simulation is a generic term that refers to an artificial representation of a real world process to achieve educational goals through experiential learning. Simulation based medical education is defined as any educational activity that utilizes simulation aides to replicate clinical scenarios. Although medical simulation is relatively new, simulation has been used for a long time in other high risk professions such as aviation. Medical simulation allows the acquisition of clinical skills through deliberate practice rather than an apprentice style of learning. Simulation tools serve as an alternative to real patients. A trainee can make mistakes and learn from them without the fear of harming the patient. There are different types and classification of simulators and their cost vary according to the degree of their resemblance to the reality, or 'fidelity'. Simulation- based learning is expensive. However, it is cost-effective if utilized properly. Medical simulation has been found to enhance clinical competence at the undergraduate and postgraduate levels. It has also been found to have many advantages that can improve patient safety and reduce health care costs through the improvement of the medical provider's competencies. The objective of this narrative review article is to highlight the importance of simulation as a new teaching method in undergraduate and postgraduate education.

  9. CFD Modelling of Bore Erosion in Two-Stage Light Gas Guns

    NASA Technical Reports Server (NTRS)

    Bogdanoff, D. W.

    1998-01-01

    A well-validated quasi-one-dimensional computational fluid dynamics (CFD) code for the analysis of the internal ballistics of two-stage light gas guns is modified to explicitly calculate the ablation of steel from the gun bore and the incorporation of the ablated wall material into the hydrogen working cas. The modified code is used to model 45 shots made with the NASA Ames 0.5 inch light gas gun over an extremely wide variety of gun operating conditions. Good agreement is found between the experimental and theoretical piston velocities (maximum errors of +/-2% to +/-6%) and maximum powder pressures (maximum errors of +/-10% with good igniters). Overall, the agreement between the experimental and numerically calculated gun erosion values (within a factor of 2) was judged to be reasonably good, considering the complexity of the processes modelled. Experimental muzzle velocities agree very well (maximum errors of 0.5-0.7 km/sec) with theoretical muzzle velocities calculated with loading of the hydrogen gas with the ablated barrel wall material. Comparison of results for pump tube volumes of 100%, 60% and 40% of an initial benchmark value show that, at the higher muzzle velocities, operation at 40% pump tube volume produces much lower hydrogen loading and gun erosion and substantially lower maximum pressures in the gun. Large muzzle velocity gains (2.4-5.4 km/sec) are predicted upon driving the gun harder (that is, upon using, higher powder loads and/or lower hydrogen fill pressures) when hydrogen loading is neglected; much smaller muzzle velocity gains (1.1-2.2 km/sec) are predicted when hydrogen loading is taken into account. These smaller predicted velocity gains agree well with those achieved in practice. CFD snapshots of the hydrogen mass fraction, density and pressure of the in-bore medium are presented for a very erosive shot.

  10. Protozoan Grazing, Bacterial Activity, and Mineralization in Two-Stage Continuous Cultures

    PubMed Central

    Bloem, Jaap; Starink, Mathieu; Bär-Gilissen, Marie-José B.; Cappenberg, Thomas E.

    1988-01-01

    In two-stage continuous cultures, at bacterial concentrations, biovolumes, and growth rates similar to values found in Lake Vechten, ingestion rates of heterotrophic nanoflagellates (HNAN) increased from 2.3 bacteria HNAN−1 · h−1 at a growth rate of 0.15 day−1 to 9.2 bacteria · HNAN−1 · h−1 at a growth rate of 0.65 day−1. On a yeast extract medium with a C/N/P ratio of 100:15:1.2 (Redfield ratio), a mixed bacterial population showed a yield of 18% (C/C) and a specific carbon content of 211 fg of C · μm−3. The HNAN carbon content and yield were estimated at 127 fg of C · μm−3 and 47% (C/C). Although P was not growth limiting, HNAN accelerated the mineralization of PO4-P from dissolved organic matter by 600%. The major mechanism of P remineralization appeared to be direct consumption of bacteria by HNAN. N mineralization was performed mainly (70%) by bacteria but was increased 30% by HNAN. HNAN did not enhance the decomposition of the relatively mineral-rich dissolved organic matter. An accelerated decomposition of organic carbon by protozoa may be restricted to mineral-poor substrates and may be explained mainly by protozoan nutrient regeneration. Growth and grazing in the cultures were compared with methods for in situ estimates. Thymidine incorporation by actively growing bacteria yielded an empirical conversion factor of 1.1 × 1018 bacteria per mol of thymidine incorporated into DNA. However, nongrowing bacteria also showed considerable incorporation. Protozoan grazing was found to be accurately measured by uptake of fluorescently labeled bacteria, whereas artificial fluorescent microspheres were not ingested, and selective prokaryotic inhibitors blocked not only bacterial growth but also protozoan grazing. PMID:16347801

  11. Two-stage models for lunar and terrestrial anorthosites: Petrogenesis without a magma ocean

    NASA Astrophysics Data System (ADS)

    Longhi, John; Ashwal, Lewis D.

    1985-02-01

    Two-stage diapiric models for lunar ferroan anorthosites and terrestrial massif anorthosites are examined. The lunar model is developed to explain early lunar differentiation in the absence of a magma ocean. If correct, the terrestrial model serves as an analog for the development of lunar anorthositic diapirs. There is field and textural evidence of transport of mostly crystalline anorthositic material within the terrestrial complexes. This evidence, combined with the absence of anorthositic lavas and phase equilibrium constraints inhibiting the production of hyperaluminous magmas, is consistent with the detachment of plagioclase-rich crystalline mushes from large, uppermost mantle plutons and multiple diapiric intrusion of these mushes into the upper sialic crust with attendant anatexis. Rudimentary dynamical calculations suggest that a simple, single-layer source for the diapirs is improbable: either there were several parental magma chambers or there was a single large chamber that was repeatedly replenished. The lunar model is a development of Wetherill's (1975) suggestion that, following accretion, the outer portion of the moon consisted of a stack of overlapping layered intrusions and that reheating of these intrusions mobilized their anorthositic layers, which intruded upwards to produce the anorthositic lunar crust. Dynamical calculations show that gravitational instabilities in anorthositic layers (≤ 1 km thick) could develop into diapirs on a reasonable time scale (50-100 m.y.) only if the outer portion of the moon was partially remelted. We suggest that partial melting of the interior due to the decay of long-lived radionuclides with the subsequent onset of global convection heated the stack of intrusions from below, thus causing melting and allowing the anorthositic diapirs to grow and ascend fairly rapidly. As the convecting zone thickened, a mass expulsion of anorthositic material out of the lunar interior may have occurred.

  12. Chromosome 21 BACE2 haplotype associates with Alzheimer's disease: a two-stage study.

    PubMed

    Myllykangas, Liisa; Wavrant-De Vrièze, Fabienne; Polvikoski, Tuomo; Notkola, Irma-Leena; Sulkava, Raimo; Niinistö, Leena; Edland, Steven D; Arepalli, Sampath; Adighibe, Omanma; Compton, Danielle; Hardy, John; Haltia, Matti; Tienari, Pentti J

    2005-09-15

    Genetic linkage studies have provided evidence for a late-onset Alzheimer's disease (AD) susceptibility locus on chromosome 21q. We have tested, in a two-stage association study, whether allelic or haplotype variation of the beta-amyloid cleaving enzyme-2 (BACE2) locus on chromosome 21q affects the risk of late-onset AD. In stage-1, an unselected population-based sample of Finns aged 85 years or over (n=515) was analysed. Neuropathologic examination including beta-amyloid load quantification was possible in over 50% (n=264) of these subjects. AD patients (n=100) and controls (n=48) were defined by modified neuropathological NIA-RI criteria. Positive associations were taken as a hypothesis, and tested in stage-2 using 483 AD families from the USA. Four single nucleotide polymorphisms (SNPs) of BACE2 gene were tested in stage-1. A SNP close to exon-6 was associated with neuropathologically verified AD (p=0.02) and also with beta-amyloid load in non-selected autopsied subjects after conditioning with APOE genotype (p=0.001). In haplotype analysis a specific, relatively common haplotype (H5) was found to associate with AD (p=0.004) and a second haplotype (H7) showed a weaker association with protection against AD (p=0.04). In stage-2, the SNP association was not replicated, whereas the haplotype H5 association was replicated (p=0.004) and a trend to association was found with the putative protective haplotype H7 (two-sided p=0.08). BACE2 haplotype association with AD in two independent datasets provides further evidence for an AD susceptibility locus on chromosome 21q within or close to BACE2.

  13. Experimental Investigation of a Model of a Two-Stage Turboblower

    NASA Technical Reports Server (NTRS)

    Dovjik, s.; Polikovsky, W.

    1943-01-01

    In the present paper an investigation is made of two stages of a multistage turboblower having a vaneless diffuser behind the impeller and guide vanes at the inlet to the nest stage. The method employed was that of investigating the performance of the successive elements of the blower (the impeller, vaneless diffuser, ets.) whereby the kinematics of the flow through the blower could be followed and the pressure at the different points computed. The character of the flow and the physical significance of the loss coefficients could thereby be determined so as to secure the best agreement of the computed with the actual performance of the blower. Since the tests were carried out for various delivery volumes, the dependence of the coefficients on a number of factors (angle of attack, velocities, etc.) could be obtained. The distribution of the losses that occur during the transformation of dynamic pressure at the impeller exit into static pressure could be found and likewise the range within which the friction coefficient varies in the vaneless diffuser. With the aid of factors having a certain physical significance, the centrifugal blower could be computed on the basis of a more or less schematical consideration of the phenomena occuring during the air flow through it, and the use of arbitrary factors and recourse to the geometrical similtude law thus avoided. The present investigation largely summarizes all the previous work af the CHI Blower Section on the different elements of a centrifugal blower. Some considerations on the analysis of model test data for application to full-scale are presented in the appendix.

  14. Electrolyzed Reduced Water Supplemented with Platinum Nanoparticles Suppresses Promotion of Two-stage Cell Transformation.

    PubMed

    Nishikawa, Ryuhei; Teruya, Kiichiro; Katakura, Yoshinori; Osada, Kazuhiro; Hamasaki, Takeki; Kashiwagi, Taichi; Komatsu, Takaaki; Li, Yuping; Ye, Jun; Ichikawa, Akira; Otsubo, Kazumichi; Morisawa, Shinkatsu; Xu, Qianghua; Shirahata, Sanetaka

    2005-01-01

    In the two-stage cell transformation theory, cancer cells first receive initiation, which is mainly caused by DNA damage, and then promotion, which enhances transformation. Murine Balb/c 3T3 cells are widely used for transformation experiments because they lose contact inhibition ability when transformed. Electrolyzed reduced water (ERW), which is produced near a cathode during electrolysis of water, is an alkaline drinking water that is beneficial to health. ERW contains a high concentration of dissolved hydrogen and scavenge reactive oxygen species (ROS), along with a small amount of platinum (Pt) nanoparticles (Pt nps) derived from Pt-coated titanium electrodes. Pt nps stably disperse in aqueous solution for a long time, and convert hydrogen molecules to active hydrogen (atomic hydrogen) that can scavenge ROS. Therefore, ERW supplemented with synthesized Pt nps is a model strong reduced water. This is the first report that ERW supplemented with synthesized Pt nps strongly prevents transformation of Balb/c 3T3 cells. ERW was prepared by electrolysis of 0.002 M NaOH solution using a batch-type electrolysis device. Balb/c 3T3 cells were treated with 3-methyl cholanthrene (MCA) as an initiation substance, followed by treatment with phorbol-12-myristate-13-acetate (PMA) as a promotion substance. MCA/PMA-induced formation of a transformation focus was strongly suppressed by ERW supplemented with Pt nps but not by ERW or Pt nps individually. ERW supplemented with Pt nps suppressed transformation at the promoter stage, not at initiation, suggesting that ERW supplemented with Pt nps suppressed the PMA-induced augmentation of intracellular ROS. ERW supplemented with Pt nps is a potential new antioxidant against carcinogenesis.

  15. Neural Mechanisms of Human Perceptual Learning: Electrophysiological Evidence for a Two-Stage Process

    PubMed Central

    Hamamé, Carlos M.; Cosmelli, Diego; Henriquez, Rodrigo; Aboitiz, Francisco

    2011-01-01

    Background Humans and other animals change the way they perceive the world due to experience. This process has been labeled as perceptual learning, and implies that adult nervous systems can adaptively modify the way in which they process sensory stimulation. However, the mechanisms by which the brain modifies this capacity have not been sufficiently analyzed. Methodology/Principal Findings We studied the neural mechanisms of human perceptual learning by combining electroencephalographic (EEG) recordings of brain activity and the assessment of psychophysical performance during training in a visual search task. All participants improved their perceptual performance as reflected by an increase in sensitivity (d') and a decrease in reaction time. The EEG signal was acquired throughout the entire experiment revealing amplitude increments, specific and unspecific to the trained stimulus, in event-related potential (ERP) components N2pc and P3 respectively. P3 unspecific modification can be related to context or task-based learning, while N2pc may be reflecting a more specific attentional-related boosting of target detection. Moreover, bell and U-shaped profiles of oscillatory brain activity in gamma (30–60 Hz) and alpha (8–14 Hz) frequency bands may suggest the existence of two phases for learning acquisition, which can be understood as distinctive optimization mechanisms in stimulus processing. Conclusions/Significance We conclude that there are reorganizations in several neural processes that contribute differently to perceptual learning in a visual search task. We propose an integrative model of neural activity reorganization, whereby perceptual learning takes place as a two-stage phenomenon including perceptual, attentional and contextual processes. PMID:21541280

  16. Greater India Basin hypothesis and a two-stage Cenozoic collision between India and Asia

    NASA Astrophysics Data System (ADS)

    Van Hinsbergen, D. J.; Lippert, P. C.; Dupont-Nivet, G.; McQuarrie, N.; Doubrovine, P. V.; Spakman, W.; Torsvik, T. H.

    2012-12-01

    Cenozoic convergence between the Indian and Asian plates pro- duced the archetypical continental collision zone comprising the Himalaya mountain belt and the Tibetan Plateau. How and where India-Asia convergence was accommodated after collision at or before 52 Ma remains a long-standing controversy. Since 52 Ma, the two plates have converged up to 3,600 +/- 35 km, yet the upper crustal shortening documented from the geological record of Asia and the Himalaya is up to approximately 2,350-km less. Here we show that the discrepancy between the convergence and the shortening can be explained by subduction of highly extended continental and oceanic Indian lithosphere within the Himalaya be- tween approximately 50 and 25 Ma. Paleomagnetic data show that this extended continental and oceanic "Greater India" promontory resulted from 2,675 +/- 700 km of North-South extension between 120 and 70 Ma, accommodated between the Tibetan Himalaya and cratonic India. We suggest that the approximately 50 Ma "India"- Asia collision was a collision of a Tibetan-Himalayan microcontinent with Asia, followed by subduction of the largely oceanic Greater India Basin along a subduction zone at the location of the Greater Himalaya. The "hard" India-Asia collision with thicker and contiguous Indian continental lithosphere occurred around 25-20 Ma. This hard collision is coincident with far-field deformation in central Asia and rapid exhumation of Greater Himalaya crystalline rocks, and may be linked to intensification of the Asian monsoon system. This two-stage collision between India and Asia is also reflected in the deep mantle remnants of subduction imaged with seismic tomography.

  17. Two-stage designs to identify the effects of SNP combinations on complex diseases.

    PubMed

    Kang, Guolian; Yue, Weihua; Zhang, Jifeng; Huebner, Marianne; Zhang, Handi; Ruan, Yan; Lu, Tianlan; Ling, Yansu; Zuo, Yijun; Zhang, Dai

    2008-01-01

    The genetic basis of complex diseases is expected to be highly heterogeneous, with many disease genes, where each gene by itself has only a small effect. Based on the nonlinear contributions of disease genes across the genome to complex diseases, we introduce the concept of single nucleotide polymorphism (SNP) synergistic blocks. A two-stage approach is applied to detect the genetic association of synergistic blocks with a disease. In the first stage, synergistic blocks associated with a complex disease are identified by clustering SNP patterns and choosing blocks within a cluster that minimize a diversity criterion. In the second stage, a logistic regression model is given for a synergistic block. Using simulated case-control data, we demonstrate that our method has reasonable power to identify gene-gene interactions. To further evaluate the performance of our method, we apply our method to 17 loci of four candidate genes for paranoid schizophrenia in a Chinese population. Five synergistic blocks are found to be associated with schizophrenia, three of which are negatively associated (odds ratio, OR < 0.3, P < 0.05), while the others are positively associated (OR > 2.0, P < 0.05). The mathematical models of these five synergistic blocks are presented. The results suggest that there may be interactive effects for schizophrenia among variants of the genes neuregulin 1 (NRG1, 8p22-p11), G72 (13q34), the regulator of G-protein signaling-4 (RGS4, 1q21-q22) and frizzled 3 (FZD3, 8p21). Using synergistic blocks, we can reduce the dimensionality in a multi-locus association analysis, and evaluate the sizes of interactive effects among multiple disease genes on complex phenotypes.

  18. Two-stage flux balance analysis of metabolic networks for drug target identification

    PubMed Central

    2011-01-01

    Background Efficient identification of drug targets is one of major challenges for drug discovery and drug development. Traditional approaches to drug target identification include literature search-based target prioritization and in vitro binding assays which are both time-consuming and labor intensive. Computational integration of different knowledge sources is a more effective alternative. Wealth of omics data generated from genomic, proteomic and metabolomic techniques changes the way researchers view drug targets and provides unprecedent opportunities for drug target identification. Results In this paper, we develop a method based on flux balance analysis (FBA) of metabolic networks to identify potential drug targets. This method consists of two linear programming (LP) models, which first finds the steady optimal fluxes of reactions and the mass flows of metabolites in the pathologic state and then determines the fluxes and mass flows in the medication state with the minimal side effect caused by the medication. Drug targets are identified by comparing the fluxes of reactions in both states and examining the change of reaction fluxes. We give an illustrative example to show that the drug target identification problem can be solved effectively by our method, then apply it to a hyperuricemia-related purine metabolic pathway. Known drug targets for hyperuricemia are correctly identified by our two-stage FBA method, and the side effects of these targets are also taken into account. A number of other promising drug targets are found to be both effective and safe. Conclusions Our method is an efficient procedure for drug target identification through flux balance analysis of large-scale metabolic networks. It can generate testable predictions, provide insights into drug action mechanisms and guide experimental design of drug discovery. PMID:21689470

  19. Pilot plant testing of IGT`s two-stage fluidized-bed/cyclonic agglomerating combustor

    SciTech Connect

    Rehmat, A.; Mensinger, M.C.; Richardson, T.L.

    1993-12-31

    The Institute of Gas Technology (IGT) is conducting a multi-year experimental program to develop and test, through pilot-scale operation, IGT`s two-stage fluidized-bed/cyclonic agglomerating combustor (AGGCOM). The AGGCOM process is based on combining the fluidized-bed agglomeration and gasification technology with the cyclonic combustion technology, both of which have been developed at IGT over many years. AGGCOM is a unique and extremely flexible combustor that can operate over a wide range of conditions in the fluidized-bed first stage from low temperature (desorption) to high temperature (agglomeration), including gasification of high-energy-content wastes. The ACCCOM combustor can easily and efficiently destroy solid, liquid, and gaseous organic wastes, while isolating solid inorganic contaminants within an essentially non-leachable glassy matrix, suitable for disposal in ordinary landfills. Fines elutriated from the first stage are captured by a high-efficiency cyclone and returned to the fluidized bed for ultimate incorporation into the agglomerates. Intense mixing in the second-stage cyclonic combustor ensures high destruction and removal efficiencies (DRE) for organic compounds that may be present in the feed material. This paper presents an overview of the experimental development of the AGGCOM process and progress made to date in designing, constructing, and operating the 6-ton/day AGGCOM pilot plant. Results of the bench-scale tests conducted to determine the operating conditions necessary to agglomerate a soil were presented at the 1991 Incineration Conference. On-site construction of the AGGCOM pilot plant was initiated in August 1992 and completed at the end of March 1993, with shakedown testing following immediately thereafter. The initial tests in the AGGCOM pilot plant will focus on the integrated operation of both stages of the combustor and will be conducted with ``clean`` topsoil.

  20. Study of Boundary Layer Development in a Two-Stage Low-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Dorney, Daniel J.; Ashpis, David E.; Halstead, David E.; Wisler, David C.

    1998-01-01

    Experimental data from jet-engine tests have indicated that unsteady blade row (wake) interactions and separation can have a significant impact on the efficiency of turbine stages. The effects of these interactions can be intensified in low-pressure turbine stages because of the low Reynolds number operating environment. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Thus, during the last decade a significant amount of effort has been put into determining the effects of transition and turbulence on the performance of low pressure turbine stages. Experimental investigations have been performed, for example, by Hodson et al. and Halstead et al. These investigations have helped identify/clarify the roles that factors such as the Reynolds number, free stream turbulence intensity, pressure gradient and curvature have in the generation of losses. In parallel to the experimental investigations, there have been significant analytical efforts to improve the modeling of transition. Examples of such efforts include the works of Mayle and Gostelow et al. These newer models show promise of providing accurate transition predictions over a wide range of flow conditions, although they have yet to be implemented into the numerical flow analyses used by the turbine design community. Some recent computational investigations of interest include the works of Chernobrovkin and Lakshminarayana and Eulitz and Engel. The focus of the current effort has been to -use a viscous, unsteady quasi-three-dimensional Navier-Stokes analysis to study boundary layer development in a two-stage low-pressure turbine. A two-layer algebraic turbulence model, along with a natural transition model and a bubble transition model, have been used, The geometry used in the simulations has been the subject of extensive experiments. The predicted results have been compared with experimental data, including airfoil loadings and time

  1. Supersonic Test of the 10-Inch Bifurcated Two-Stage Supersonic Inlet (BTSSI)

    NASA Technical Reports Server (NTRS)

    Carlin, C. M.; Frisch, I.; Kolden, J. J.; Koncsek, J. L.; Marrs, K. J.; Mayer, D. W.; McMahon, S. L.; Milligan, K. H.; Sommerfield, D. M.

    2003-01-01

    Experimental results from testing of a novel supersonic inlet model in NASA Glenn Research Center's 10- by 10-foot supersonic wind tunnel are presented. The patented inlet concept, called Two-Stage Supersonic Inlet (TSSI), incorporates a large cavity, or throat slot, in the supersonic diffuser intended to enhance the stability of the normal shock. The present embodiment of the concept is a bifurcated twin-duct) design. During the course of testing an unusual 'semi-started' mode of operation was encountered. The inlet was able to spill up to 30 percent of the captured airstream without fully expelling the normal shock. In this mode, the total pressure recovery dropped approximately 6 percent without increasing steady-state distortion. Dynamic instrumentation at the cowl lip station indicates the semi-start mode may be a series of unstart/restart cycles with frequency ranging from 0.2 to 20 Hz. Engine face total pressure measurements indicate a modest impact due to this event. However, since the current test article does not have a representative subsonic diffuser (and is in fact separated), it is unclear how this mode of operation would effect an engine. Further investigation of this phenomenon is required before it is fully understood. Prior testing of the TSSI concept allowed extension of fully started inlet operation to regions of significantly reduced supply flow without reducing recovery. The test article was a smaller scale than the present test and was a single duct design. In the present test, the expanded range of stable operation with high recovery was not realized.

  2. Two-stage muscle activity responses in decisions about leg movement adjustments during trip recovery

    PubMed Central

    Potocanac, Zrinka; Pijnappels, Mirjam; Verschueren, Sabine; van Dieën, Jaap

    2015-01-01

    Studies on neural decision making mostly investigated fast corrective adjustments of arm movements. However, fast leg movement corrections deserve attention as well, since they are often required to avoid falling after balance perturbations. The present study aimed at elucidating the mechanisms behind fast corrections of tripping responses by analyzing the concomitant leg muscle activity changes. This was investigated in seven young adults who were tripped in between normal walking trials and took a recovery step by elevating the tripped leg over the obstacle. In some trials, a forbidden landing zone (FZ) was presented behind the obstacle, at the subjects' preferred foot landing position, forcing a step correction. Muscle activity of the tripped leg gastrocnemius medialis (iGM), tibialis anterior (iTA), rectus femoris (iRF), and biceps femoris (iBF) muscles was compared between normal trips presented before any FZ appearance, trips with a FZ, and normal trips presented in between trips with a FZ (“catch” trials). When faced with a real or expected (catch trials) FZ, subjects shortened their recovery steps. The underlying changes in muscle activity consisted of two stages. The first stage involved reduced iGM activity, occurring at a latency shorter than voluntary reaction, followed by reduced iTA and increased iBF and iGM activities occurring at longer latencies. The fast response was not related to step shortening, but longer latency responses clearly were functional. We suggest that the initial response possibly acts as a “pause,” allowing the nervous system to integrate the necessary information and prepare the subsequent, functional movement adjustment. PMID:26561597

  3. A two-stage cyclone using microcentrifuge tubes for personal bioaerosol sampling.

    PubMed

    Lindsley, William G; Schmechel, Detlef; Chen, Bean T

    2006-11-01

    Personal aerosol samplers are widely used to monitor human exposure to airborne materials. For bioaerosols, interest is growing in analyzing samples using molecular and immunological techniques. This paper presents a personal sampler that uses a two-stage cyclone to collect bioaerosols into disposable 1.5 ml Eppendorf-type microcentrifuge tubes. Samples can be processed in the tubes for polymerase chain reaction (PCR) or immunoassays, and the use of multiple stages fractionates aerosol particles by aerodynamic diameter. The sampler was tested using fluorescent microspheres and aerosolized fungal spores. The sampler had first and second stage cut-off diameters of 2.6 microm and 1.6 microm at 2 l min(-1)(geometric standard deviation, GSD = 1.45 and 1.75), and 1.8 microm and 1 microm at 3.5 l min(-1)(GSD = 1.42 and 1.55). The sampler aspiration efficiency was >or=98% at both flow rates for particles with aerodynamic diameters of 3.1 microm or less. For 6.2 microm particles, the aspiration efficiency was 89% at 2 l min(-1) and 96% at 3.5 l min(-1). At 3.5 l min(-1), the sampler collected 92% of aerosolized Aspergillus versicolor and Penicillium chrysogenum spores inside the two microcentrifuge tubes, with less than 0.4% of the spores collecting on the back-up filter. The design and techniques given here are suitable for personal bioaerosol sampling, and could also be adapted to design larger aerosol samplers for longer-term atmospheric and indoor air quality sampling.

  4. Enhancement of pyruvate production by Torulopsis glabrata using a two-stage oxygen supply control strategy.

    PubMed

    Li, Y; Hugenholtz, J; Chen, J; Lun, S-Y

    2002-10-01

    The effect of agitation speeds on the performance of producing pyruvate by a multi-vitamin auxotrophic yeast, Torulopsis glabrata, was investigated in batch fermentation. High pyruvate yield on glucose (0.797 g g(-1)) was achieved under high agitation speed (700 rpm), but the glucose consumption rate was rather low (1.14 g l(-1) h(-1)). Glucose consumption was enhanced under low agitation speed (500 rpm), but the pyruvate yield on glucose decreased to 0.483 g g(-1). Glycerol production was observed under low agitation speed and decreased with increasing agitation speed. Based on process analysis and carbon flux distribution calculation, a two-stage oxygen supply control strategy was proposed, in which the agitation speed was controlled at 700 rpm in the first 16 h and then switched to 500 rpm. This was experimentally proven to be successful. Relatively high concentration of pyruvate (69.4 g l(-1)), high pyruvate yield on glucose (0.636 g g(-1)), and high glucose consumption rate (1.95 g l(-1)h(-1)) were achieved by applying this strategy. The productivity (1.24 g l(-1) h(-1)) was improved by 36%, 23% and 31%, respectively, compared with fermentations in which agitation speeds were kept constant at 700 rpm, 600 rpm, and 500 rpm. Experimental results indicate that the difference between the performances for producing pyruvate under a favorable state of oxygen supply (dissolved oxygen concentration >50%) was caused by the different regeneration pathways of NADH generated from glycolysis.

  5. Two-Stage orders sequencing system for mixed-model assembly

    NASA Astrophysics Data System (ADS)

    Zemczak, M.; Skolud, B.; Krenczyk, D.

    2015-11-01

    In the paper, the authors focus on the NP-hard problem of orders sequencing, formulated similarly to Car Sequencing Problem (CSP). The object of the research is the assembly line in an automotive industry company, on which few different models of products, each in a certain number of versions, are assembled on the shared resources, set in a line. Such production type is usually determined as a mixed-model production, and arose from the necessity of manufacturing customized products on the basis of very specific orders from single clients. The producers are nowadays obliged to provide each client the possibility to determine a huge amount of the features of the product they are willing to buy, as the competition in the automotive market is large. Due to the previously mentioned nature of the problem (NP-hard), in the given time period only satisfactory solutions are sought, as the optimal solution method has not yet been found. Most of the researchers that implemented inaccurate methods (e.g. evolutionary algorithms) to solving sequencing problems dropped the research after testing phase, as they were not able to obtain reproducible results, and met problems while determining the quality of the received solutions. Therefore a new approach to solving the problem, presented in this paper as a sequencing system is being developed. The sequencing system consists of a set of determined rules, implemented into computer environment. The system itself works in two stages. First of them is connected with the determination of a place in the storage buffer to which certain production orders should be sent. In the second stage of functioning, precise sets of sequences are determined and evaluated for certain parts of the storage buffer under certain criteria.

  6. Investigation on the two-stage active magnetic regenerative refrigerator for liquefaction of hydrogen

    SciTech Connect

    Park, Inmyong; Park, Jiho; Jeong, Sangkwon; Kim, Youngkwon

    2014-01-29

    An active magnetic regenerative refrigerator (AMRR) is expected to be useful for hydrogen liquefaction due to its inherent high thermodynamic efficiency. Because the temperature of the cold end of the refrigerator has to be approximately liquid temperature, a large temperature span of the active magnetic regenerator (AMR) is indispensable when the heat sink temperature is liquid nitrogen temperature or higher. Since magnetic refrigerants are only effective in the vicinity of their own transition temperatures, which limit the temperature span of the AMR, an innovative structure is needed to increase the temperature span. The AMR must be a layered structure and the thermophysical matching of magnetic field and flow convection effects is very important. In order to design an AMR for liquefaction of hydrogen, the implementation of multi-layered AMR with different magnetic refrigerants is explored with multi-staging. In this paper, the performance of the multi-layered AMR using four rare-earth compounds (GdNi{sub 2}, Gd{sub 0.1}Dy{sub 0.9}Ni{sub 2}, Dy{sub 0.85}Er{sub 0.15}Al{sub 2}, Dy{sub 0.5}Er{sub 0.5}Al{sub 2}) is investigated. The experimental apparatus includes two-stage active magnetic regenerator containing two different magnetic refrigerants each. A liquid nitrogen reservoir connected to the warm end of the AMR maintains the temperature of the warm end around 77 K. High-pressure helium gas is employed as a heat transfer fluid in the AMR and the maximum magnetic field of 4 T is supplied by the low temperature superconducting (LTS) magnet. The temperature span with the variation of parameters such as phase difference between magnetic field and mass flow rate of magnetic refrigerants in AMR is investigated. The maximum temperature span in the experiment is recorded as 50 K and several performance issues have been discussed in this paper.

  7. Conceptual design of two-stage-to-orbit hybrid launch vehicle

    NASA Astrophysics Data System (ADS)

    1991-07-01

    The object of this design class was to design an earth-to orbit vehicle to replace the present NASA space shuttle. The major motivations for designing a new vehicle were to reduce the cost of putting payloads into orbit and to design a vehicle that could better service the space station with a faster turn-around time. Another factor considered in the design was that near-term technology was to be used. Materials, engines and other important technologies were to be realized in the next 10 to 15 years. The first concept put forth by NASA to meet these objectives was the National Aerospace Plane (NASP). The NASP is a single-stage earth-to-orbit air-breathing vehicle. This concept ran into problems with the air-breathing engine providing enough thrust in the upper atmosphere, among other things. The solution of this design class is a two-stage-to-orbit vehicle. The first stage is air-breathing and the second stage is rocket-powered, similar to the space shuttle. The second stage is mounted on the top of the first stage in a piggy-back style. The vehicle takes off horizontally using only air-breathing engines, flies to Mach six at 100,000 feet, and launches the second stage towards its orbital path. The first stage, or booster, will weigh approximately 800,000 pounds and the second stage, or orbiter will weigh approximately 300,000 pounds. The major advantage of this design is the full recoverability of the first stage compared with the present solid rocket booster that are only partially recoverable and used only a few times. This reduces the cost as well as providing a more reliable and more readily available design for servicing the space station. The booster can fly an orbiter up, turn around, land, refuel, and be ready to launch another orbiter in a matter of hours.

  8. Using collaborative two-stage examinations to address test anxiety in a large enrollment gateway course.

    PubMed

    Fournier, Kimberly A; Couret, Jannelle; Ramsay, Jason B; Caulkins, Joshua L

    2017-01-30

    Large enrollment foundational courses are perceived as "high stakes" because of their potential to act as barriers for progression to the next course or admittance to a program. The nature of gateway courses makes them ideal settings to explore the relationship between anxiety, pedagogical interventions, and student performance. Here, two-stage collaborative examinations were implemented to improve test-taking skills and address widespread test anxiety in an introductory human anatomy course. Test anxiety data were collected (using the Motivated Strategies for Learning Questionnaire) before the first examination and last examination. Most students experienced decreased test anxiety over the course of the semester; however, some students may have experienced performance limiting conditions due to test anxiety at the end of the semester based on academic ability in the course (in "C" students when compared to "A" students: P < 0.00006 and "B" students: P < 0.05), overall academic ability (in academically weaker students: P < 0.025), and demographic factors (in women: P < 0.025). The strongest performances on examinations were primarily observed in already academically strong students (mean individual performance: P < 0.000, mean group performance: P < 0.000). Furthermore, changes in test anxiety were not significantly associated with the group portion of the examinations. Patterns of changes in test anxiety over the course of the semester underscore a complex interaction between test anxiety, student background, and student performance. Results suggest that pathways for test anxiety in "high stakes" courses may be separate from the mechanisms responsible for the benefits of collaborative testing. Anat Sci Educ. © 2017 American Association of Anatomists.

  9. The Timing of Breast Irradiation in Two-Stage Expander/Implant Breast Reconstruction.

    PubMed

    Yan, Chen; Fischer, John P; Freedman, Gary M; Basta, Marten N; Kovach, Stephen J; Serletti, Joseph M; Lin, Lilie; Wu, Liza C

    2016-05-01

    Certain patients who initiate expander/implant (E/I) reconstruction following mastectomy may require radiation therapy (XRT). XRT may be delivered during the tissue expander (TE) expansion process or after exchange for a permanent implant (PI). We studied a series of women treated with E/I reconstruction and XRT to determine whether there is a difference in complication rates between those who had XRT to the TE versus PI. All two-stage E/I reconstructions at our institution from April 2005 to January 2013 were reviewed to identify patients who underwent XRT after TE placement. Our database was queried for reconstructive details, oncologic treatment, and complications. Statistical analyses were performed to establish significance of complication rate differences. Fifty-two patients underwent XRT after TE placement, 42 of which had XRT to the TE and 11 of which had XRT to the PI. The major complication rates (complications requiring emergent reoperation/readmission) were 27% versus 0% (p = 0.05) for XRT to the TE versus XRT to the PI, but there were no significant differences in minor complication rates (outpatient complications). Specifically, the rates of Grade 3/4 capsular contracture were similar between the two groups, 27% for the XRT to the TE group and 36% for the XRT to the PI group. Radiation of the PI versus radiation of the TE did not result in significant differences in overall surgical complication rates but had fewer major complications and no implant failures. Other factors must also be considered, such as patient preference, risk of cancer reoccurrence, and cosmesis. It is essential for a patient to have a team of a plastic surgeon and radiation, surgical, and medical oncologists working together to achieve each patient's goals.

  10. Conceptual design of two-stage-to-orbit hybrid launch vehicle

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The object of this design class was to design an earth-to orbit vehicle to replace the present NASA space shuttle. The major motivations for designing a new vehicle were to reduce the cost of putting payloads into orbit and to design a vehicle that could better service the space station with a faster turn-around time. Another factor considered in the design was that near-term technology was to be used. Materials, engines and other important technologies were to be realized in the next 10 to 15 years. The first concept put forth by NASA to meet these objectives was the National Aerospace Plane (NASP). The NASP is a single-stage earth-to-orbit air-breathing vehicle. This concept ran into problems with the air-breathing engine providing enough thrust in the upper atmosphere, among other things. The solution of this design class is a two-stage-to-orbit vehicle. The first stage is air-breathing and the second stage is rocket-powered, similar to the space shuttle. The second stage is mounted on the top of the first stage in a piggy-back style. The vehicle takes off horizontally using only air-breathing engines, flies to Mach six at 100,000 feet, and launches the second stage towards its orbital path. The first stage, or booster, will weigh approximately 800,000 pounds and the second stage, or orbiter will weigh approximately 300,000 pounds. The major advantage of this design is the full recoverability of the first stage compared with the present solid rocket booster that are only partially recoverable and used only a few times. This reduces the cost as well as providing a more reliable and more readily available design for servicing the space station. The booster can fly an orbiter up, turn around, land, refuel, and be ready to launch another orbiter in a matter of hours.

  11. Evaluation of a two-stage framework for prediction using big genomic data.

    PubMed

    Jiang, Xia; Neapolitan, Richard E

    2015-11-01

    We are in the era of abundant 'big' or 'high-dimensional' data. These data afford us the opportunity to discover predictors of an event of interest, and to estimate occurrence of the event based on values of these predictors. For example, 'genome-wide association studies' examine millions of single-nucleotide polymorphisms (SNPs), along with disease status. We can learn SNPs that affect disease status from these data sets, and use the knowledge learned to predict disease likelihood. Owing to the large number of features, it is difficult for many prediction methods to use all the features directly. The ReliefF algorithm ranks a set of features in terms of how well they predict a target. It can be used to identify good predictors, which can then be provided to a prediction method. We compared the performance of eight prediction methods when predicting binary outcomes using high-dimensional discrete data sets. We performed two-stage prediction, where ReliefF is used in the first stage to identify good predictors. Bayesian network (BN)-based methods performed best overall. Furthermore, ReliefF did not improve their performance. The BN-based methods use the Bayesian Dirichlet Equivalent Uniform score to evaluate candidate models, and use BN inference algorithms to perform prediction. This score and these algorithms were developed for discrete variables. This perhaps explains why they perform better in this domain. Many prediction methods are available, and researchers have little reason for choosing one over the other in the domain of binary prediction using high-dimensional data sets. Our results indicate that the best choices overall are BN-based methods.

  12. Two-stage crystallization of charged colloids under low supersaturation conditions.

    PubMed

    Kratzer, Kai; Arnold, Axel

    2015-03-21

    We report simulations on the homogeneous liquid-fcc nucleation of charged colloids for both low and high contact energy values. As a precursor for crystal formation, we observe increased local order at the position where the crystal will form, but no correlations with the local density. Thus, the nucleation is driven by order fluctuations rather than density fluctuations. Our results also show that the transition involves two stages in both cases, first a transition of liquid → bcc, followed by a bcc → hcp/fcc transition. Both transitions have to overcome free energy barriers, so that a spherical bcc-like cluster is formed first, in which the final fcc structure is nucleated mainly at the surface of the crystallite. This means that the second stage bcc-fcc phase transition is a heterogeneous nucleation in the partially grown solid phase, even though we start from a homogeneous bulk liquid. The height of the bcc → hcp/fcc free energy barrier strongly depends on the contact energies of the colloids. For low contact energy this barrier is low, so that the bcc → hcp/fcc transition occurs spontaneously. For the higher contact energy, the second barrier is too high to be crossed spontaneously by the colloidal system. However, it was possible to ratchet the system over the second barrier and to transform the bcc nuclei into the stable hcp/fcc phase. The transitions are dominated by the first liquid-bcc transition and can be described by classical nucleation theory using an effective surface tension.

  13. An improved sup 222 Rn canister using a two-stage charcoal system

    SciTech Connect

    Scarpitta, S.C.; Harley, N.H. )

    1991-02-01

    A prototype for an improved passive {sup 222}Rn canister (R-Canister) was designed and compared to conventional charcoal canisters for its adsorptive and desorptive characteristics following exposures to {sup 222}Rn at 23{degrees}C in the presence of water vapor. The R-Canister, containing a two-stage charcoal system, minimizes the adverse effects of water vapor by maintaining the amount of adsorbed water vapor in the primary Rn adsorbent below the break-point of the charcoal. This is achieved by the placement of a desiccant charcoal cartridge 6 cm above the primary Rn adsorbent. The optimal bed depth of the primary adsorbent, determined from a diffusion study, was found to be 2.3 cm. The measured value for the effective diffusion coefficient of RN in a peat-based charcoal at 15% humidity and 25{degrees}C is 7.97 x 10(-10) m2 s-1. Exposures to 70% humidity for 7 d increased the buildup time-constant of Rn in the R-Canisters by 33% as compared to R-Canisters exposed to 15% humidity. At relative humidities ranging from 15-70%, the {sup 222}Rn buildup time-constant of the R-Canister ranged from 43-94 h, whereas the desorption time-constant ranged from 46-64 h. Typical buildup time-constants and desorption time-constants for conventional fully-opened charcoal canisters currently in field use ranged from 30-43 h and 17-29 h, respectively, over the same range of humidities.

  14. A two-stage model of orientation integration for Battenberg-modulated micropatterns.

    PubMed

    Baldwin, Alex S; Husk, Jesse S; Meese, Tim S; Hess, Robert F

    2014-01-30

    The visual system pools information from local samples to calculate textural properties. We used a novel stimulus to investigate how signals are combined to improve estimates of global orientation. Stimuli were 29 × 29 element arrays of 4 c/deg log Gabors, spaced 1° apart. A proportion of these elements had a coherent orientation (horizontal/vertical) with the remainder assigned random orientations. The observer's task was to identify the global orientation. The spatial configuration of the signal was modulated by a checkerboard pattern of square checks containing potential signal elements. The other locations contained either randomly oriented elements ("noise check") or were blank ("blank check"). The distribution of signal elements was manipulated by varying the size and location of the checks within a fixed-diameter stimulus. An ideal detector would only pool responses from potential signal elements. Humans did this for medium check sizes and for large check sizes when a signal was presented in the fovea. For small check sizes, however, the pooling occurred indiscriminately over relevant and irrelevant locations. For these check sizes, thresholds for the noise check and blank check conditions were similar, suggesting that the limiting noise is not induced by the response to the noise elements. The results are described by a model that filters the stimulus at the potential target orientations and then combines the signals over space in two stages. The first is a mandatory integration of local signals over a fixed area, limited by internal noise at each location. The second is a task-dependent combination of the outputs from the first stage.

  15. Neuroscience and approach/avoidance personality traits: a two stage (valuation-motivation) approach.

    PubMed

    Corr, Philip J; McNaughton, Neil

    2012-11-01

    Many personality theories link specific traits to the sensitivities of the neural systems that control approach and avoidance. But there is no consensus on the nature of these systems. Here we combine recent advances in economics and neuroscience to provide a more solid foundation for a neuroscience of approach/avoidance personality. We propose a two-stage integration of valuation (loss/gain) sensitivities with motivational (approach/avoidance/conflict) sensitivities. Our key conclusions are: (1) that valuation of appetitive and aversive events (e.g. gain and loss as studied by behavioural economists) is an independent perceptual input stage--with the economic phenomenon of loss aversion resulting from greater negative valuation sensitivity compared to positive valuation sensitivity; (2) that valuation of an appetitive stimulus then interacts with a contingency of presentation or omission to generate a motivational 'attractor' or 'repulsor', respectively (vice versa for an aversive stimulus); (3) the resultant behavioural tendencies to approach or avoid have distinct sensitivities to those of the valuation systems; (4) while attractors and repulsors can reinforce new responses they also, more usually, elicit innate or previously conditioned responses and so the perception/valuation-motivation/action complex is best characterised as acting as a 'reinforcer' not a 'reinforcement'; and (5) approach-avoidance conflict must be viewed as activating a third motivation system that is distinct from the basic approach and avoidance systems. We provide examples of methods of assessing each of the constructs within approach-avoidance theories and of linking these constructs to personality measures. We sketch a preliminary five-element reinforcer sensitivity theory (RST-5) as a first step in the integration of existing specific approach-avoidance theories into a coherent neuroscience of personality.

  16. Two-stage aquifer pumping subject to slow desorption and persistent sources.

    PubMed

    Saez, Jose A; Harmon, Thomas C

    2006-01-01

    This work focuses on improving pump-and-treat remediation by optimizing a two-stage operational scheme to reduce volumes extracted when confronted with nonequilibrium desorption, low-permeability units, and continuous contaminant sources such as non-aqueous phase liquids (NAPL). Q1 and Q2 are the initial short-term high pumping rate and later long-term low pumping rate, respectively. A two-dimensional ground water flow and transport management model was used to test the proposed strategy for plumes developed from finite (NAPL-free) and continuous (NAPL-driven) contaminant sources in homogeneous and nonhomogeneous (zoned) aquifers. Remediation scenarios were simulated over durations of 2000, 6000, and 15,000 d to determine (1) the optimal time to switch from a preset Q1 to Q2 and (2) the value of Q2. The problem was constrained by mass removal requirements, maximum allowable downgradient concentrations, and practical bounds on Q2. Q1 was fixed at preset values 50% to 200% higher than the single-stage pumping rates (i.e., steady pumping rates during entire remediation period) necessary to achieve a desired cleanup level and capture the plume. Results for the NAPL-free homogeneous case under nonequilibrium desorption conditions achieved the same level of cleanup as single-stage pumping, while reducing extracted volumes by up to 36%. Comparable savings were obtained with NAPL-driven sources only when the source concentration was reduced by at least 2 orders of magnitude. For the zoned aquifer, the proposed strategy provided volume savings of up to 24% under NAPL-free and reduced source conditions.

  17. End-wall boundary layer measurements in a two-stage fan

    NASA Technical Reports Server (NTRS)

    Ball, C. L.; Reid, L.; Schmidt, J. F.

    1983-01-01

    Detailed flow measurements made in the casing boundary layer of a two-stage transonic fan are summarized. These measurements were taken at stations upstream of the fan, between all blade rows, and downstream of the last blade row. At the design tip speed of 429 m/sec the fan achieved a peak efficiency of 0.846 at a pressure ratio of 2.471. The boundary layer data were obtained at three weight flows at the design speed: one near choke flow, one near peak efficiency, and one near stall. Conventional boundary layer parameters were calculated from the data measured at each measuring station for each of the three flows. A classical two dimensional casing boundary layer was measured at the fan inlet and extended inward to approximately 15 percent of span. A highly three dimensional boundary layer was measured at the exit of each blade row and extended inward to approximately 10 percent of span. The steep radial gradient of axial velocity noted at the exit of the rotors was reduced substantially as the flow passed through the stators. This reduced gradient is attributed to flow mixing. The amount of flow mixing was reflected in the radial redistribution of total temperature as the flow passed through the stators. The data also show overturning of the tip flow at the stator exits that is consistent with the expected effect of the secondary flow field. The blockage factors calculated from the measured data show an increase in blockage across the rotors and a decrease across the stators.

  18. The influence of Thomson effect in the performance optimization of a two stage thermoelectric cooler

    NASA Astrophysics Data System (ADS)

    Kaushik, S. C.; Manikandan, S.

    2015-12-01

    The exoreversible and irreversible thermodynamic models of a two stage thermoelectric cooler (TTEC) considering Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction effects have been investigated using exergy analysis. New expressions for the interstage temperature, optimum current for the maximum cooling power, energy and exergy efficiency conditions, energy efficiency and exergy efficiency of a TTEC are derived as well. The number of thermocouples in the first and second stages of a TTEC for the maximum cooling power, energy and exergy efficiency conditions are optimized. The results show that the exergy efficiency is lower than the energy efficiency e.g., in an irreversible TTEC with total 30 thermocouples, heat sink temperature (TH) of 300 K and heat source temperature (TC) of 280 K, the obtained maximum cooling power, maximum energy and exergy efficiency are 20.37 W, 0.7147 and 5.10% respectively. It has been found that the Thomson effect increases the cooling power and energy efficiency of the TTEC system e.g., in the exoreversible TTEC the cooling power and energy efficiency increased from 14.87 W to 16.36 W and from 0.4079 to 0.4998 respectively for ΔTC of 40 K when Thomson effect is considered. It has also been found that the heat transfer area at the hot side of an irreversible TTEC should be higher than the cold side for maximum performance operation. This study will help in the designing of the actual multistage thermoelectric cooling systems.

  19. Operation of a two-stage fermentation process producing hydrogen and methane from organic waste.

    PubMed

    Ueno, Yoshiyuki; Fukui, Hisatomo; Goto, Masafumi

    2007-02-15

    A pilot-scale experimental plant for the production of hydrogen and methane by a two-stage fermentation process was constructed and operated using a mixture of pulverized garbage and shredded paper wastes. Thermophilic hydrogen fermentation was established at 60 degrees C in the first bioreactor by inoculating with seed microflora. Following the hydrogenogenic process, methanogenesis in the second bioreactor was conducted at 55 degrees C using an internal recirculation packed-bed reactor (IRPR). After conducting steady-state operations under a few selected conditions, the overall hydraulic retention time was optimized at 8 d (hydrogenogenesis, 1.2 d; methanogenesis, 6.8 d), producing 5.4 m3/m3/d of hydrogen and 6.1 m3/m3/d of methane with chemical oxygen demand and volatile suspended solid removal efficiencies of 79.3% and 87.8%, respectively. Maximum hydrogen production yield was calculated to be 2.4 mol/mol hexose and 56 L/kg COD loaded. The methanogenic performance of the IRPR was stable, although the organic loading rate and the composition of the effluent from the hydrogenogenic process fluctuated substantially. A clone library analysis of the microflora in the hydrogenogenic reactor indicated that hydrogen-producing Thermoanaerobacterium-related organisms in the inoculum were active in the hydrogen fermentation of garbage and paper wastes, although no aseptic operations were applied. We speculate that the operation at high temperature and the inoculation of thermophiles enabled the selective growth of the introduced microorganisms and gave hydrogen fermentation efficiencies comparable to laboratory experiments. This is the first report on fermentative production of hydrogen and methane from organic waste at an actual level.

  20. Greater India Basin hypothesis and a two-stage Cenozoic collision between India and Asia.

    PubMed

    van Hinsbergen, Douwe J J; Lippert, Peter C; Dupont-Nivet, Guillaume; McQuarrie, Nadine; Doubrovine, Pavel V; Spakman, Wim; Torsvik, Trond H

    2012-05-15

    Cenozoic convergence between the Indian and Asian plates produced the archetypical continental collision zone comprising the Himalaya mountain belt and the Tibetan Plateau. How and where India-Asia convergence was accommodated after collision at or before 52 Ma remains a long-standing controversy. Since 52 Ma, the two plates have converged up to 3,600 ± 35 km, yet the upper crustal shortening documented from the geological record of Asia and the Himalaya is up to approximately 2,350-km less. Here we show that the discrepancy between the convergence and the shortening can be explained by subduction of highly extended continental and oceanic Indian lithosphere within the Himalaya between approximately 50 and 25 Ma. Paleomagnetic data show that this extended continental and oceanic "Greater India" promontory resulted from 2,675 ± 700 km of North-South extension between 120 and 70 Ma, accommodated between the Tibetan Himalaya and cratonic India. We suggest that the approximately 50 Ma "India"-Asia collision was a collision of a Tibetan-Himalayan microcontinent with Asia, followed by subduction of the largely oceanic Greater India Basin along a subduction zone at the location of the Greater Himalaya. The "hard" India-Asia collision with thicker and contiguous Indian continental lithosphere occurred around 25-20 Ma. This hard collision is coincident with far-field deformation in central Asia and rapid exhumation of Greater Himalaya crystalline rocks, and may be linked to intensification of the Asian monsoon system. This two-stage collision between India and Asia is also reflected in the deep mantle remnants of subduction imaged with seismic tomography.

  1. Greater India Basin hypothesis and a two-stage Cenozoic collision between India and Asia

    PubMed Central

    van Hinsbergen, Douwe J. J.; Lippert, Peter C.; Dupont-Nivet, Guillaume; McQuarrie, Nadine; Doubrovine, Pavel V.; Spakman, Wim; Torsvik, Trond H.

    2012-01-01

    Cenozoic convergence between the Indian and Asian plates produced the archetypical continental collision zone comprising the Himalaya mountain belt and the Tibetan Plateau. How and where India–Asia convergence was accommodated after collision at or before 52 Ma remains a long-standing controversy. Since 52 Ma, the two plates have converged up to 3,600 ± 35 km, yet the upper crustal shortening documented from the geological record of Asia and the Himalaya is up to approximately 2,350-km less. Here we show that the discrepancy between the convergence and the shortening can be explained by subduction of highly extended continental and oceanic Indian lithosphere within the Himalaya between approximately 50 and 25 Ma. Paleomagnetic data show that this extended continental and oceanic “Greater India” promontory resulted from 2,675 ± 700 km of North–South extension between 120 and 70 Ma, accommodated between the Tibetan Himalaya and cratonic India. We suggest that the approximately 50 Ma “India”–Asia collision was a collision of a Tibetan-Himalayan microcontinent with Asia, followed by subduction of the largely oceanic Greater India Basin along a subduction zone at the location of the Greater Himalaya. The “hard” India–Asia collision with thicker and contiguous Indian continental lithosphere occurred around 25–20 Ma. This hard collision is coincident with far-field deformation in central Asia and rapid exhumation of Greater Himalaya crystalline rocks, and may be linked to intensification of the Asian monsoon system. This two-stage collision between India and Asia is also reflected in the deep mantle remnants of subduction imaged with seismic tomography. PMID:22547792

  2. Two-stage vs single-stage thermophilic anaerobic digestion: comparison of energy production and biodegradation efficiencies.

    PubMed

    Schievano, Andrea; Tenca, Alberto; Scaglia, Barbara; Merlino, Giuseppe; Rizzi, Aurora; Daffonchio, Daniele; Oberti, Roberto; Adani, Fabrizio

    2012-08-07

    Two-stage anaerobic digestion (AD) for integrated biohydrogen and biomethane production from organic materials has been reported to promise higher process efficiency and energy recoveries as compared to traditional one-stage AD. This work presents a comparison between two-stage (reactors R1 and R2) and one-stage (reactor R3) AD systems, fed with identical organic substrates and loading rates, focusing the attention on chemical and microbiological aspects. Contrary to previous experiences, no significant differences in overall energy recovery were found for the two-stage and one-stage AD systems. However, an accumulation in R2 of undegraded intermediate metabolites (volatile fatty acids, ketones, amines, amino acids, and phenols) was observed by GC-MS. These compounds were thought to be both cause and effect of this partial inefficiency of the two-stage system, as confirmed also by the less diverse, and thereby less efficient, population of fermentative bacteria observed (by PCR-DGGE) in R2. The extreme environment of R1 (low pH and high metabolites concentrations) probably acted as selector of metabolic pathways, favoring H(2)-producing bacteria able to degrade such a wide variability of intermediate metabolites while limiting other strains. Therefore, if two-stage AD may potentially lead to higher energy recoveries, further efforts should be directed to ensure process efficiency and stability.

  3. Enhancement of bioenergy production from organic wastes by two-stage anaerobic hydrogen and methane production process.

    PubMed

    Luo, Gang; Xie, Li; Zhou, Qi; Angelidaki, Irini

    2011-09-01

    The present study investigated a two-stage anaerobic hydrogen and methane process for increasing bioenergy production from organic wastes. A two-stage process with hydraulic retention time (HRT) 3d for hydrogen reactor and 12d for methane reactor, obtained 11% higher energy compared to a single-stage methanogenic process (HRT 15 d) under organic loading rate (OLR) 3 gVS/(L d). The two-stage process was still stable when the OLR was increased to 4.5 gVS/(Ld), while the single-stage process failed. The study further revealed that by changing the HRT(hydrogen):HRT(methane) ratio of the two-stage process from 3:12 to 1:14, 6.7%, more energy could be obtained. Microbial community analysis indicated that the dominant bacterial species were different in the hydrogen reactors (Thermoanaerobacterium thermosaccharolyticum-like species) and methane reactors (Clostridium thermocellum-like species). The changes of substrates and HRT did not change the dominant species. The archaeal community structures in methane reactors were similar both in single- and two- stage reactors, with acetoclastic methanogens Methanosarcina acetivorans-like organisms as the dominant species.

  4. Improvement of vibration energy harvesters through a two-stage design: power production at single frequency excitation.

    PubMed

    Fernando, Joseph S; Sun, Qiao

    2013-11-01

    A vibration harvester is usually designed to work in resonance responding to source vibration. Many existing types of harvesters use a single mechanical resonator to amplify the excitation vibrations. However, these harvesters are inherently limited in the amount of power that they can produce, due to their design, particularly in the limited number of design parameters. In our study, we propose a two-stage design to improve a harvester's performance both in power production and in bandwidth widening. In this paper, we demonstrate that a two-stage design can increase the power production when the device is intended to operate under a single frequency excitation. Harvester parameters are optimized to provide maximum power production. Power production comparisons between single-stage and two-stage harvesters are made through numerical simulation and experiments.

  5. Low-, high-coverage, and two-stage DNA sequencing in the design of the genetic association study.

    PubMed

    Xu, Chao; Wu, Kehao; Zhang, Ji-Gang; Shen, Hui; Deng, Hong-Wen

    2017-04-01

    Next-generation sequencing-based genetic association study (GAS) is a powerful tool to identify candidate disease variants and genomic regions. Although low-coverage sequencing offers low cost but inadequacy in calling rare variants, high coverage is able to detect essentially every variant but at a high cost. Two-stage sequencing may be an economical way to conduct GAS without losing power. In two-stage sequencing, an affordable number of samples are sequenced at high coverage as the reference panel, then to impute in a larger sample is sequenced at low coverage. As unit sequencing costs continue to decrease, investigators can now conduct GAS with more flexible sequencing depths. Here, we systematically evaluate the effect of the read depth and sample size on the variant discovery power and association power for study designs using low-coverage, high-coverage, and two-stage sequencing. We consider 12 low-coverage, 12 high-coverage, and 51 two-stage design scenarios with the read depth varying from 0.5× to 80×. With state-of-the-art simulation and analysis packages and in-house scripts, we simulate the complete study process from DNA sequencing to SNP (single nucleotide polymorphism) calling and association testing. Our results show that with appropriate allocation of sequencing effort, two-stage sequencing is an effective approach for conducting GAS. We provide practical guidelines for investigators to plan the optimum sequencing-based GAS including two-stage sequencing design given their specific constraints of sequencing investment.

  6. Effect of ammoniacal nitrogen on one-stage and two-stage anaerobic digestion of food waste

    SciTech Connect

    Ariunbaatar, Javkhlan; Scotto Di Perta, Ester; Panico, Antonio; Frunzo, Luigi; Esposito, Giovanni; Lens, Piet N.L.; Pirozzi, Francesco

    2015-04-15

    Highlights: • Almost 100% of the biomethane potential of food waste was recovered during AD in a two-stage CSTR. • Recirculation of the liquid fraction of the digestate provided the necessary buffer in the AD reactors. • A higher OLR (0.9 gVS/L·d) led to higher accumulation of TAN, which caused more toxicity. • A two-stage reactor is more sensitive to elevated concentrations of ammonia. • The IC{sub 50} of TAN for the AD of food waste amounts to 3.8 g/L. - Abstract: This research compares the operation of one-stage and two-stage anaerobic continuously stirred tank reactor (CSTR) systems fed semi-continuously with food waste. The main purpose was to investigate the effects of ammoniacal nitrogen on the anaerobic digestion process. The two-stage system gave more reliable operation compared to one-stage due to: (i) a better pH self-adjusting capacity; (ii) a higher resistance to organic loading shocks; and (iii) a higher conversion rate of organic substrate to biomethane. Also a small amount of biohydrogen was detected from the first stage of the two-stage reactor making this system attractive for biohythane production. As the digestate contains ammoniacal nitrogen, re-circulating it provided the necessary alkalinity in the systems, thus preventing an eventual failure by volatile fatty acids (VFA) accumulation. However, re-circulation also resulted in an ammonium accumulation, yielding a lower biomethane production. Based on the batch experimental results the 50% inhibitory concentration of total ammoniacal nitrogen on the methanogenic activities was calculated as 3.8 g/L, corresponding to 146 mg/L free ammonia for the inoculum used for this research. The two-stage system was affected by the inhibition more than the one-stage system, as it requires less alkalinity and the physically separated methanogens are more sensitive to inhibitory factors, such as ammonium and propionic acid.

  7. The Two-Stage Examination: A Method to Assess Individual Competence and Collaborative Problem Solving in Medical Students

    PubMed Central

    Morton, David A.; Pippitt, Karly; Lamb, Sara; Colbert-Getz, Jorie M.

    2016-01-01

    Problem Effectively solving problems as a team under stressful conditions is central to medical practice; however, because summative examinations in medical education must test individual competence, they are typically solitary assessments. Approach Using two-stage examinations, in which students first answer questions individually (Stage 1) and then discuss them in teams prior to resubmitting their answers (Stage 2), is one method for rectifying this discordance. On the basis of principles of social constructivism, the authors hypothesized that two-stage examinations would lead to better retention of, specifically, items answered incorrectly at Stage 1. In fall 2014, they divided 104 first-year medical students into two groups of 52 students. Groups alternated each week between taking one- and two-stage examinations such that each student completed 6 one-stage and 6 two-stage examinations. The authors reassessed 61 concepts on a final examination and, using the Wilcoxon signed ranked tests, compared performance for all concepts and for just those students initially missed, between Stages 1 and 2. Outcomes Final examination performance on all previously assessed concepts was not significantly different between the one-and two-stage conditions (P = .77); however, performance on only concepts that students initially answered incorrectly on a prior examination improved by 12% for the two-stage condition relative to the one-stage condition (P = .02, r = 0.17). Next Steps Team assessment may be most useful for assessing concepts students find difficult, as opposed to all content. More research is needed to determine whether these results apply to all medical school topics and student cohorts. PMID:27049544

  8. Assessing the effects of metabolism of environmental agents on cancer tumor development by a two-stage model of carcinogenesis.

    PubMed Central

    Tan, W Y; Singh, K P

    1987-01-01

    By combining the Michaelis-Menten kinetics of metabolism with the two-stage model of Moolgavkar and Knudson (1981) and the extended two-stage model of carcinogenesis proposed by Tan and Gastardo (1985), this paper proceeds to investigate the effects of metabolism of carcinogens on cancer tumor development. It is shown that the nonlinear kinetics of metabolism of carcinogens affect the dose-response relationship mainly through the mutation rates. If the initiator is affected by metabolism, then the metabolism of promoters has very little or negligible effects of the expected incidences and the number of tumors. PMID:3691427

  9. Does animal welfare influence dairy farm efficiency? A two-stage approach.

    PubMed

    Allendorf, J J; Wettemann, P J C

    2015-11-01

    This article investigated how process-based animal welfare indicators (PAI) affected the technical efficiency of German dairy farms. A sample of 115 North-Rhine Westphalian dairy farms was used to estimate their technical efficiency with data envelopment analysis. A censored regression model was then applied to quantify the effects of PAI on technical efficiency. The results indicated that in particular a higher percentage of cow losses, a higher replacement rate, and a longer calving interval had, at their respective mean, a negative marginal effect on the technical efficiency of the sample farms. In contrast, a lower age of first calving, a higher in-milk performance, and a higher somatic cell count were positively correlated with technical efficiency. Some of the PAI followed a polynomial trend (i.e., their influence on technical efficiency did not have a constant sign, and levels for minimum/maximum technical efficiency were present). The minimum efficiency score at constant returns to scale was obtained when farmers had cow losses of 0.4%, a calving interval of 430d, and a cell count of 146,000 per milliliter. However, maximum technical efficiency was obtained at a milk yield of 9,796 kg per cow and year. The corresponding amounts in case of technical efficiency under variable returns to scale were at a similar level, except that milk yield showed a positive linear influence on technical efficiency. Moreover, technical efficiency under variable returns to scale was positively correlated with the fat content of milk. The lowest level of technical efficiency was reached at a fat content of 4.1%. Subsequently, we found that efficient dairy farms did not always correspond with recommended values concerning animal welfare criteria. Finally, the results showed that the assumption of a monotone effect direction of PAI on farm efficiency was inappropriate, and that this issue would need to be addressed in future research.

  10. A stratified two-stage sampling design for digital soil mapping in a Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Blaschek, Michael; Duttmann, Rainer

    2015-04-01

    The quality of environmental modelling results often depends on reliable soil information. In order to obtain soil data in an efficient manner, several sampling strategies are at hand depending on the level of prior knowledge and the overall objective of the planned survey. This study focuses on the collection of soil samples considering available continuous secondary information in an undulating, 16 km²-sized river catchment near Ussana in southern Sardinia (Italy). A design-based, stratified, two-stage sampling design has been applied aiming at the spatial prediction of soil property values at individual locations. The stratification based on quantiles from density functions of two land-surface parameters - topographic wetness index and potential incoming solar radiation - derived from a digital elevation model. Combined with four main geological units, the applied procedure led to 30 different classes in the given test site. Up to six polygons of each available class were selected randomly excluding those areas smaller than 1ha to avoid incorrect location of the points in the field. Further exclusion rules were applied before polygon selection masking out roads and buildings using a 20m buffer. The selection procedure was repeated ten times and the set of polygons with the best geographical spread were chosen. Finally, exact point locations were selected randomly from inside the chosen polygon features. A second selection based on the same stratification and following the same methodology (selecting one polygon instead of six) was made in order to create an appropriate validation set. Supplementary samples were obtained during a second survey focusing on polygons that have either not been considered during the first phase at all or were not adequately represented with respect to feature size. In total, both field campaigns produced an interpolation set of 156 samples and a validation set of 41 points. The selection of sample point locations has been done using

  11. A two-stage method for microcalcification cluster segmentation in mammography by deformable models

    SciTech Connect

    Arikidis, N.; Kazantzi, A.; Skiadopoulos, S.; Karahaliou, A.; Costaridou, L.; Vassiou, K.

    2015-10-15

    Purpose: Segmentation of microcalcification (MC) clusters in x-ray mammography is a difficult task for radiologists. Accurate segmentation is prerequisite for quantitative image analysis of MC clusters and subsequent feature extraction and classification in computer-aided diagnosis schemes. Methods: In this study, a two-stage semiautomated segmentation method of MC clusters is investigated. The first stage is targeted to accurate and time efficient segmentation of the majority of the particles of a MC cluster, by means of a level set method. The second stage is targeted to shape refinement of selected individual MCs, by means of an active contour model. Both methods are applied in the framework of a rich scale-space representation, provided by the wavelet transform at integer scales. Segmentation reliability of the proposed method in terms of inter and intraobserver agreements was evaluated in a case sample of 80 MC clusters originating from the digital database for screening mammography, corresponding to 4 morphology types (punctate: 22, fine linear branching: 16, pleomorphic: 18, and amorphous: 24) of MC clusters, assessing radiologists’ segmentations quantitatively by two distance metrics (Hausdorff distance—HDIST{sub cluster}, average of minimum distance—AMINDIST{sub cluster}) and the area overlap measure (AOM{sub cluster}). The effect of the proposed segmentation method on MC cluster characterization accuracy was evaluated in a case sample of 162 pleomorphic MC clusters (72 malignant and 90 benign). Ten MC cluster features, targeted to capture morphologic properties of individual MCs in a cluster (area, major length, perimeter, compactness, and spread), were extracted and a correlation-based feature selection method yielded a feature subset to feed in a support vector machine classifier. Classification performance of the MC cluster features was estimated by means of the area under receiver operating characteristic curve (Az ± Standard Error) utilizing

  12. Performances of single and two-stage pulse tube cryocoolers under different vacuum levels with and without thermal radiation shields

    NASA Astrophysics Data System (ADS)

    Kasthurirengan, Srinivasan; Behera, Upendra; Nadig, D. S.; Krishnamoorthy, V.

    2012-06-01

    Single and two-stage Pulse Tube Cryocoolers (PTC) have been designed, fabricated and experimentally studied. The single stage PTC reaches a no-load temperature of ~ 29 K at its cold end, the two-stage PTC reaches ~ 2.9 K in its second stage cold end and ~ 60 K in its first stage cold end. The two-stage Pulse Tube Cryocooler provides a cooling power of ~ 250 mW at 4.2 K. The single stage system uses stainless steel meshes along with Pb granules as its regenerator materials, while the two-stage PTC uses combinations of Pb along with Er3Ni / HoCu2 as the second stage regenerator materials. Normally, the above systems are insulated by thermal radiation shields and mounted inside a vacuum chamber which is maintained at high vacuum. To evaluate the performance of these systems in the possible conditions of loss of vacuum with and without radiation shields, experimental studies have been performed. The heat-in-leak under such severe conditions has been estimated from the heat load characteristics of the respective stages. The experimental results are analyzed to obtain surface emissivities and effective thermal conductivities as a function of interspace pressure.

  13. On Two-Stage Multiple Comparison Procedures When There Are Unequal Sample Sizes in the First Stage.

    ERIC Educational Resources Information Center

    Wilcox, Rand R.

    1984-01-01

    Two stage multiple-comparison procedures give an exact solution to problems of power and Type I errors, but require equal sample sizes in the first stage. This paper suggests a method of evaluating the experimentwise Type I error probability when the first stage has unequal sample sizes. (Author/BW)

  14. Modelling of two-stage anaerobic digestion using the IWA Anaerobic Digestion Model No. 1 (ADM1).

    PubMed

    Blumensaat, F; Keller, J

    2005-01-01

    The aim of the study presented was to implement a process model to simulate the dynamic behaviour of a pilot-scale process for anaerobic two-stage digestion of sewage sludge. The model implemented was initiated to support experimental investigations of the anaerobic two-stage digestion process. The model concept implemented in the simulation software package MATLAB/Simulink is a derivative of the IWA Anaerobic Digestion Model No.1 (ADM1) that has been developed by the IWA task group for mathematical modelling of anaerobic processes. In the present study the original model concept has been adapted and applied to replicate a two-stage digestion process. Testing procedures, including balance checks and 'benchmarking' tests were carried out to verify the accuracy of the implementation. These combined measures ensured a faultless model implementation without numerical inconsistencies. Parameters for both, the thermophilic and the mesophilic process stage, have been estimated successfully using data from lab-scale experiments described in literature. Due to the high number of parameters in the structured model, it was necessary to develop a customised procedure that limited the range of parameters to be estimated. The accuracy of the optimised parameter sets has been assessed against experimental data from pilot-scale experiments. Under these conditions, the model predicted reasonably well the dynamic behaviour of a two-stage digestion process in pilot scale.

  15. Two-stage anaerobic digestion process for complete inactivation of enteric bacterial pathogens in human night soil.

    PubMed

    Kunte, D P; Yeole, T Y; Ranade, D R

    2004-01-01

    Anaerobic digestion offers a good alternative for human waste treatment. However, the fate of enteric bacterial pathogens present in human night soil (HNS) remains a major concern for hygienic safety of the process. A two-stage anaerobic digestion process, consisting of separate acidogenic and methanogenic digesters, was designed and its efficacy in the inactivation of Salmonella typhi was compared to a single-stage digestion process. In a single-stage digestion, complete pathogen inactivation was achieved only in the digesters with high levels of volatile fatty acids (VFA approximately equal to 18,000 mg/l) and acidic pH (approximately equal to 6.0). These digesters, however, showed drastic reduction in methane yield. In the two-stage digestion process, S. typhi was completely inactivated in the acidogenic digester and the methanogenic digester was free from the pathogen even after receiving a daily dose of the pathogen. The process also achieved complete inactivation of other enteric pathogens, viz., Shigella dysenteriae and Vibrio cholerae. The two-stage process was efficient in biogas generation from HNS. Thus, the two-stage process ensures complete hygienic safety in anaerobic digestion of human night soil.

  16. QUANTIFYING AGGREGATE CHLORPYRIFOS EXPOSURE AND DOSE TO CHILDREN USING A PHYSICALLY-BASED TWO-STAGE MONTE CARLO PROBABILISTIC MODEL

    EPA Science Inventory

    To help address the Food Quality Protection Act of 1996, a physically-based, two-stage Monte Carlo probabilistic model has been developed to quantify and analyze aggregate exposure and dose to pesticides via multiple routes and pathways. To illustrate model capabilities and ide...

  17. Effects of two-stage and total vs. fence-line weaning on the physiology and performance of beef calves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calves weaned using a two-stage method where nursing is prevented between cow-calf pairs prior to separation (Stage 1) experience less weaning stress after separation (Stage 2) based on behavior and growth measures. The aim of this study was to document changes in various physiological measures of s...

  18. Phase-resolved surface pressure and heat-transfer measurements on the blade of a two-stage turbine

    SciTech Connect

    Dunn, M.G.; Haldeman, C.W. Jr.

    1995-12-01

    Phase-resolved surface pressure, and unsteady pressure measurements are reported for the first-stage blade row of the Space Shuttle Main Engine two-stage fuel-side turbine. Measurements were made at 10, 50, and 90 percent span on both the pressure and suction surfaces of the blade. Phase-resolved and unsteady heat-flux measurements are also reported.

  19. A Two-Stage Multi-Agent Based Assessment Approach to Enhance Students' Learning Motivation through Negotiated Skills Assessment

    ERIC Educational Resources Information Center

    Chadli, Abdelhafid; Bendella, Fatima; Tranvouez, Erwan

    2015-01-01

    In this paper we present an Agent-based evaluation approach in a context of Multi-agent simulation learning systems. Our evaluation model is based on a two stage assessment approach: (1) a Distributed skill evaluation combining agents and fuzzy sets theory; and (2) a Negotiation based evaluation of students' performance during a training…

  20. Using Errors to Teach through a Two-Staged, Structured Review: Peer-Reviewed Quizzes and "What's Wrong with Me?"

    ERIC Educational Resources Information Center

    Coppola, Brian P.; Pontrello, Jason K.

    2014-01-01

    Using errors as a method of learning has been made explicit through a two-staged peer review and discussion. During organic chemistry discussion sessions, quizzes are followed by a structured peer review designed to help students identify and discuss student errors. After the face-to-face discussion, a second stage of review involves analyzing and…

  1. Two-Stage Hands-On Technology Activity to Develop Preservice Teachers' Competency in Applying Science and Mathematics Concepts

    ERIC Educational Resources Information Center

    Lin, Kuen-Yi; Williams, P. John

    2017-01-01

    This paper discusses the implementation of a two-stage hands-on technology learning activity, based on Dewey's learning experience theory that is designed to enhance preservice teachers' primary and secondary experiences in developing their competency to solve hands-on problems that apply science and mathematics concepts. The major conclusions…

  2. EMERGING TECHNOLOGY SUMMARY: PILOT-SCALE DEMONSTRATION OF A TWO-STAGE METHANOTROPHIC BIOREACTOR FOR BIODEGRADATION OF TRICHLOROETHENE IN GROUNDWATER

    EPA Science Inventory

    BioTrol, Inc., developed a two-stage, methanotrophic, bioreactor system for remediation of water contaminated with trichloroethylene (TCE) and other chlorinated, volatile, aliphatic hydrocarbons. The first stage was a suspended-growth culture vessel with a bubbleless methane tran...

  3. Effect of ammoniacal nitrogen on one-stage and two-stage anaerobic digestion of food waste.

    PubMed

    Ariunbaatar, Javkhlan; Scotto Di Perta, Ester; Panico, Antonio; Frunzo, Luigi; Esposito, Giovanni; Lens, Piet N L; Pirozzi, Francesco

    2015-04-01

    This research compares the operation of one-stage and two-stage anaerobic continuously stirred tank reactor (CSTR) systems fed semi-continuously with food waste. The main purpose was to investigate the effects of ammoniacal nitrogen on the anaerobic digestion process. The two-stage system gave more reliable operation compared to one-stage due to: (i) a better pH self-adjusting capacity; (ii) a higher resistance to organic loading shocks; and (iii) a higher conversion rate of organic substrate to biomethane. Also a small amount of biohydrogen was detected from the first stage of the two-stage reactor making this system attractive for biohythane production. As the digestate contains ammoniacal nitrogen, re-circulating it provided the necessary alkalinity in the systems, thus preventing an eventual failure by volatile fatty acids (VFA) accumulation. However, re-circulation also resulted in an ammonium accumulation, yielding a lower biomethane production. Based on the batch experimental results the 50% inhibitory concentration of total ammoniacal nitrogen on the methanogenic activities was calculated as 3.8 g/L, corresponding to 146 mg/L free ammonia for the inoculum used for this research. The two-stage system was affected by the inhibition more than the one-stage system, as it requires less alkalinity and the physically separated methanogens are more sensitive to inhibitory factors, such as ammonium and propionic acid.

  4. Evaluation of a Two-Stage Approach in Trans-Ethnic Meta-Analysis in Genome-Wide Association Studies.

    PubMed

    Hong, Jaeyoung; Lunetta, Kathryn L; Cupples, L Adrienne; Dupuis, Josée; Liu, Ching-Ti

    2016-05-01

    Meta-analysis of genome-wide association studies (GWAS) has achieved great success in detecting loci underlying human diseases. Incorporating GWAS results from diverse ethnic populations for meta-analysis, however, remains challenging because of the possible heterogeneity across studies. Conventional fixed-effects (FE) or random-effects (RE) methods may not be most suitable to aggregate multiethnic GWAS results because of violation of the homogeneous effect assumption across studies (FE) or low power to detect signals (RE). Three recently proposed methods, modified RE (RE-HE) model, binary-effects (BE) model and a Bayesian approach (Meta-analysis of Transethnic Association [MANTRA]), show increased power over FE and RE methods while incorporating heterogeneity of effects when meta-analyzing trans-ethnic GWAS results. We propose a two-stage approach to account for heterogeneity in trans-ethnic meta-analysis in which we clustered studies with cohort-specific ancestry information prior to meta-analysis. We compare this to a no-prior-clustering (crude) approach, evaluating type I error and power of these two strategies, in an extensive simulation study to investigate whether the two-stage approach offers any improvements over the crude approach. We find that the two-stage approach and the crude approach for all five methods (FE, RE, RE-HE, BE, MANTRA) provide well-controlled type I error. However, the two-stage approach shows increased power for BE and RE-HE, and similar power for MANTRA and FE compared to their corresponding crude approach, especially when there is heterogeneity across the multiethnic GWAS results. These results suggest that prior clustering in the two-stage approach can be an effective and efficient intermediate step in meta-analysis to account for the multiethnic heterogeneity.

  5. Meta-analysis using individual participant data: one-stage and two-stage approaches, and why they may differ.

    PubMed

    Burke, Danielle L; Ensor, Joie; Riley, Richard D

    2017-02-28

    Meta-analysis using individual participant data (IPD) obtains and synthesises the raw, participant-level data from a set of relevant studies. The IPD approach is becoming an increasingly popular tool as an alternative to traditional aggregate data meta-analysis, especially as it avoids reliance on published results and provides an opportunity to investigate individual-level interactions, such as treatment-effect modifiers. There are two statistical approaches for conducting an IPD meta-analysis: one-stage and two-stage. The one-stage approach analyses the IPD from all studies simultaneously, for example, in a hierarchical regression model with random effects. The two-stage approach derives aggregate data (such as effect estimates) in each study separately and then combines these in a traditional meta-analysis model. There have been numerous comparisons of the one-stage and two-stage approaches via theoretical consideration, simulation and empirical examples, yet there remains confusion regarding when each approach should be adopted, and indeed why they may differ. In this tutorial paper, we outline the key statistical methods for one-stage and two-stage IPD meta-analyses, and provide 10 key reasons why they may produce different summary results. We explain that most differences arise because of different modelling assumptions, rather than the choice of one-stage or two-stage itself. We illustrate the concepts with recently published IPD meta-analyses, summarise key statistical software and provide recommendations for future IPD meta-analyses. © 2016 The Authors. Statistics in Medicine published by John Wiley & Sons Ltd.

  6. Effectiveness of a two-stage strategy with HPV testing followed by visual inspection with acetic acid for cervical cancer screening in a low-income setting.

    PubMed

    Tebeu, Pierre-Marie; Fokom-Domgue, Joël; Crofts, Victoria; Flahaut, Emmanuel; Catarino, Rosa; Untiet, Sarah; Vassilakos, Pierre; Petignat, Patrick

    2015-03-15

    The World Health Organization recently advocated a two-stage strategy with human papillomavirus (HPV) testing followed by visual inspection of the cervix with acetic acid (VIA) as a suitable option for cervical cancer screening. However, its accuracy has never been directly assessed in the context of primary screening. To evaluate effectiveness of HPV testing on self-obtained specimens (self-HPV) followed by VIA (sequential testing) in a low-income setting, we recruited 540 women aged between 30 and 65 years in two Cameroonian periurban areas. Eligible women were counseled about cervical cancer and how to perform self-sampling. HPV positive and a random sample of HPV-negative women were called back for VIA and biopsy. Disease was defined by interpretation of cervical intraepithelial neoplasia Grade 2 or worse (CIN2+). Performances of VIA, self-HPV and sequential testing were determined after adjustment for verification bias. HPV prevalence was 27.0%. VIA positivity was 12.9% and disease prevalence was 5%. Sensitivity and specificity of VIA for CIN2+ were 36.4% [95% confidence interval (CI): 15.2-64.6%] and 90.4% (95% CI: 85.4-93.7%), respectively. Sensitivity of self-HPV [100.0% (95% CI: 79.6-100.0%)] was 66% higher than that of sequential testing [33.3% (95% CI: 15.2-58.3%)]. Meanwhile, specificity of self-HPV [74.5% (95% CI: 70.6-78.1%)] was 22% lower than that of sequential testing [96.7% (95% CI: 94.8-97.9%)]. A two-stage screening strategy with self-HPV followed by VIA improves specificity of cervical cancer screening, but at the cost of an important loss of sensitivity. Ways to improve VIA performance or other tools are needed to increase positive predictive value of HPV testing.

  7. Cost efficiency of simulation-based acquisition

    NASA Astrophysics Data System (ADS)

    Luzeaux, Dominique J. P.

    2003-09-01

    Reduction of risks and acquisition delays is a major issue for procurement services, as it contributes directly to the cost and availability of the system. A new approach, know as simulation-based acquisition (SBA) has been used increasingly within the last past years. In this paper, we address cost-effectiveness issues of SBA. Using the standard cost estimates familiar to program managers, we show first that the cost overhead of using SBA instead of a "conservative" approach is cancelled and turned into a financial gain as soon as the first unforeseen event arises. Then, we show that reuse within SBA of a system-of-systems induces financial gains which give the design of the encompassing meta-system for free.

  8. Changes to the LANL gas driven two stage gun : projectile velocity measurement and etc.

    SciTech Connect

    Gustavsen, R. L.; Sheffield, S. A.; Alcon, R. R.; Medina, R. S.

    2001-01-01

    stage gun. It was necessary to use optical methods because electrical shorting pins damaged the projectile:, turned .the projectile causing tilted impacts, and sprayed the target with bits of broken pin. The first optical method involved cutting shrzllow grooves in the sides of the projectile at precisely measured intervals. Thc projectile pilssed through a single light beam focused in such a way that the grooves would alternately block and transmit light to a sensing system. This system didn't work because the groovas filled with smoke, blocking the light at all times after the projectile first broke the hearn. The second method used light rcflectetl off the projectile at four different positions. Light from a 400 mW laser was split into four oplical fibers. Half of the light reflected from the end of each B9er 'was retutncd to it phototnulitiplier. When the projectile passed in front of a fiber the amount of returned light increased. This system had a very poor signal to noise ratio: the amount of light returned when the projectile passed in front ofthe fiber was scarcely larger than the noise on the signals. 'I'hc third system used four stations at which laser light was transmitted from one optical fiber to another. 'The projectile passed close by tlhe sending or receiving fiber, rapidly cutting off the transmitted light. This method suffered from a lasix speckle pattern which changed with time thereby giving a constiintly changing inlerisiily. The fiber optic beam splitter used to split the laser light in methods two and three was also very nnstable: the amount of light split into any particular fiber varied with teinperature, vibration, and any movement of fibers. The method which was ultimately successful used it SmW, 670 nni laser diode at each of' four positions. A small lens focused this light to a point through which Ilie projectile passed. Transmitted light was imaged into 700 micron plastic fibers which relayed thhe light to a bank of photomultipliers

  9. Interval arithmetic in calculations

    NASA Astrophysics Data System (ADS)

    Bairbekova, Gaziza; Mazakov, Talgat; Djomartova, Sholpan; Nugmanova, Salima

    2016-10-01

    Interval arithmetic is the mathematical structure, which for real intervals defines operations analogous to ordinary arithmetic ones. This field of mathematics is also called interval analysis or interval calculations. The given math model is convenient for investigating various applied objects: the quantities, the approximate values of which are known; the quantities obtained during calculations, the values of which are not exact because of rounding errors; random quantities. As a whole, the idea of interval calculations is the use of intervals as basic data objects. In this paper, we considered the definition of interval mathematics, investigated its properties, proved a theorem, and showed the efficiency of the new interval arithmetic. Besides, we briefly reviewed the works devoted to interval analysis and observed basic tendencies of development of integral analysis and interval calculations.

  10. Left thoracoscopic two-stage repair of tracheoesophageal fistula with a right aortic arch and a vascular ring

    PubMed Central

    Oshima, Kazuo; Uchida, Hiroo; Tainaka, Takahisa; Tanano, Akihide; Shirota, Chiyoe; Yokota, Kazuki; Murase, Naruhiko; Shirotsuki, Ryo; Chiba, Kosuke; Hinoki, Akinari

    2017-01-01

    A right aortic arch (RAA) is found in 5% of neonates with tracheoesophageal fistulae (TEF) and may be associated with vascular rings. Oesophageal repairs for TEF with an RAA via the right chest often pose surgical difficulties. We report for the first time in the world a successful two-stage repair by left-sided thoracoscope for TEF with an RAA and a vascular ring. We switched from right to left thoracoscopy after finding an RAA. A proximal oesophageal pouch was hemmed into the vascular ring; therefore, we selected a two-stage repair. The TEF was resected and simple internal traction was placed into the oesophagus at the first stage. Detailed examination showed the patent ductus arteriosus (PDA) completing a vascular ring. The subsequent primary oesophago-oesophagostomy and dissection of PDA was performed by left-sided thoracoscope. Therefore, left thoracoscopic repair is safe and feasible for treating TEF with an RAA and a vascular ring. PMID:27143697

  11. Influence of different substrates on the performance of a two-stage high pressure anaerobic digestion system.

    PubMed

    Lemmer, A; Chen, Y; Lindner, J; Wonneberger, A M; Zielonka, S; Oechsner, H; Jungbluth, T

    2015-02-01

    The two-stage autogenerative high-pressure digestion technique is a novel and promising approach for the production of gaseous fuels or upgraded biogas. This new technique is described in the patent DE 10 2011 015415 A1 and integrates biogas production, its upgrading and pressure boosting in one process. Anaerobic digestion under elevated pressure conditions leads to decreasing pH-values in the digestate due to the augmented formation of carboxylic acid. Model calculations carried out to evaluate the two-stage design showed that the pH-value in the pressurized anaerobic filter has a major influence on the methane content of the biogas produced. Within this study, the influence of the nitrogen content as one of the most important buffering substances on the performance of the system has been tested. The results show that higher NH4 contents lead to higher pH-values in the digester and as a consequence to higher methane contents.

  12. [Study on supply and demand relation based on two stages division of market of Chinese materia medica].

    PubMed

    Yang, Guang; Guo, Lan-Ping; Wang, Nuo; Zeng, Yan; Huang, Lu-Qi

    2014-01-01

    The complex production processes and long industrial chain in traditional Chinese medicine (TCM) market result in difficulty in Chinese market microstructure research. Based on the defining the logical relationships among different concepts. This paper divides TCM market into two stages as Chinese materia medica resource market and traditional Chinese Patent Medicines market. Under this foundation, we investigated the supply capacity, approaching rules and motivation system of suppliers in TCM market, analyzed the demand situation in the perspective of demand side, and evaluated the purchasing power in terms of population profile, income, and insurance. Furthermore we also analyzed the price formation mechanism in two stages of TCM market. We hope this study can make a positive and promotion effect on TCM market related research.

  13. Two stage hydrolysis of corn stover at high solids content for mixing power saving and scale-up applications.

    PubMed

    Liu, Ke; Zhang, Jian; Bao, Jie

    2015-11-01

    A two stage hydrolysis of corn stover was designed to solve the difficulties between sufficient mixing at high solids content and high power input encountered in large scale bioreactors. The process starts with the quick liquefaction to convert solid cellulose to liquid slurry with strong mixing in small reactors, then followed the comprehensive hydrolysis to complete saccharification into fermentable sugars in large reactors without agitation apparatus. 60% of the mixing energy consumption was saved by removing the mixing apparatus in large scale vessels. Scale-up ratio was small for the first step hydrolysis reactors because of the reduced reactor volume. For large saccharification reactors in the second step, the scale-up was easy because of no mixing mechanism was involved. This two stage hydrolysis is applicable for either simple hydrolysis or combined fermentation processes. The method provided a practical process option for industrial scale biorefinery processing of lignocellulose biomass.

  14. Speech enhancement via two-stage dual tree complex wavelet packet transform with a speech presence probability estimator

    NASA Astrophysics Data System (ADS)

    Sun, Pengfei; Qin, Jun

    2017-02-01

    In this paper, a two-stage dual tree complex wavelet packet transform (DTCWPT) based speech enhancement algorithm has been proposed, in which a speech presence probability (SPP) estimator and a generalized minimum mean squared error (MMSE) estimator are developed. To overcome the drawback of signal distortions caused by down sampling of WPT, a two-stage analytic decomposition concatenating undecimated WPT (UWPT) and decimated WPT is employed. An SPP estimator in the DTCWPT domain is derived based on a generalized Gamma distribution of speech, and Gaussian noise assumption. The validation results show that the proposed algorithm can obtain enhanced perceptual evaluation of speech quality (PESQ), and segmental signal-to-noise ratio (SegSNR) at low SNR nonstationary noise, compared with other four state-of-the-art speech enhancement algorithms, including optimally modified LSA (OM-LSA), soft masking using a posteriori SNR uncertainty (SMPO), a posteriori SPP based MMSE estimation (MMSE-SPP), and adaptive Bayesian wavelet thresholding (BWT).

  15. The Production of High Purity Phycocyanin by Spirulina platensis Using Light-Emitting Diodes Based Two-Stage Cultivation.

    PubMed

    Lee, Sang-Hyo; Lee, Ju Eun; Kim, Yoori; Lee, Seung-Yop

    2016-01-01

    Phycocyanin is a photosynthetic pigment found in photosynthetic cyanobacteria, cryptophytes, and red algae. In general, production of phycocyanin depends mainly on the light conditions during the cultivation period, and purification of phycocyanin requires expensive and complex procedures. In this study, we propose a new two-stage cultivation method to maximize the quantitative content and purity of phycocyanin obtained from Spirulina platensis using red and blue light-emitting diodes (LEDs) under different light intensities. In the first stage, Spirulina was cultured under a combination of red and blue LEDs to obtain the fast growth rate until reaching an absorbance of 1.4-1.6 at 680 nm. Next, blue LEDs were used to enhance the concentration and purity of the phycocyanin in Spirulina. Two weeks of the two-stage cultivation of Spirulina yielded 1.28 mg mL(-1) phycocyanin with the purity of 2.7 (OD620/OD280).

  16. Laboratory-scale experiments applied to the design of a two-stage submerged combustion evaporation system.

    PubMed

    Yue, Dongbei; Xu, Yudong; Mahar, Rasool Bux; Liu, Fuqiang; Nie, Yongfeng

    2007-01-01

    To simulate a submerged combustion evaporation (SCE) process under laboratory conditions, this study conducted three kinds of indirect-heating evaporation experiments, including normal evaporation, vacuum evaporation, and gas-carrying evaporation experiments on mature municipal solid waste (MSW) landfill leachate. The results showed that the organic concentrations in terms of COD in condensates were always very high at the beginning, then decreased rapidly, and stabilized at a low level, which suggests that only the forepart of vapors need to be safely treated to control the discharge of organic pollutants. This study applied the process in developing a two-stage SCE system, which has been implemented for the treatment of biologically pretreated and concentrated leachate from Membrane Bioreactor (MBR) and Reverse Osmosis (RO) combined process in the Beishenshu MSW Landfill, Beijing, China. The result shows that the two-stage SCE system can successfully further concentrate refractory organic matter in concentrated leachate and remove volatile organics from the vapor.

  17. Two-stage damage diagnosis based on the distance between ARMA models and pre-whitening filters

    NASA Astrophysics Data System (ADS)

    Zheng, H.; Mita, A.

    2007-10-01

    This paper presents a two-stage damage diagnosis strategy for damage detection and localization. Auto-regressive moving-average (ARMA) models are fitted to time series of vibration signals recorded by sensors. In the first stage, a novel damage indicator, which is defined as the distance between ARMA models, is applied to damage detection. This stage can determine the existence of damage in the structure. Such an algorithm uses output only and does not require operator intervention. Therefore it can be embedded in the sensor board of a monitoring network. In the second stage, a pre-whitening filter is used to minimize the cross-correlation of multiple excitations. With this technique, the damage indicator can further identify the damage location and severity when the damage has been detected in the first stage. The proposed methodology is tested using simulation and experimental data. The analysis results clearly illustrate the feasibility of the proposed two-stage damage diagnosis methodology.

  18. Two-stage soil infiltration treatment system for treating ammonium wastewaters of low COD/TN ratios.

    PubMed

    Lei, Zhongfang; Wu, Ting; Zhang, Yi; Liu, Xiang; Wan, Chunli; Lee, Duu-Jong; Tay, Joo-Hwa

    2013-01-01

    Soil infiltration treatment (SIT) is ineffective to treat ammonium wastewaters of total nitrogen (TN) > 100 mg l(-1). This study applied a novel two-stage SIT process for effective TN removal from wastewaters of TN>100 mg l(-1) and of chemical oxygen demand (COD)/TN ratio of 3.2-8.6. The wastewater was first fed into the soil column (stage 1) at hydraulic loading rate (HLR) of 0.06 m(3) m(-2) d(-1) for COD removal and total phosphorus (TP) immobilization. Then the effluent from stage 1 was fed individually into four soil columns (stage 2) at 0.02 m(3) m(-2) d(-1) of HLR with different proportions of raw wastewater as additional carbon source. Over the one-year field test, balanced nitrification and denitrification in the two-stage SIT revealed excellent TN removal (>90%) from the tested wastewaters.

  19. Two-stage reconstruction in congenital pseudarthrosis of the forearm using the Ilizarov technique and vascularized osteoseptocutaneous fibula.

    PubMed

    Mateev, Musa; Imanaliev, Arstan

    2006-04-01

    The authors present nine patients with congenital pseudarthrosis of the forearm. The reconstruction was carried out in two stages. At the first stage, Ilizarov's device was applied to the forearm in order to lengthen the affected extremity and to eliminate deformity. At the second stage, the bone defect was replaced a with free vascularized fibula osteoseptocutaneous graft. All patients had complete survival of the transferred fibula grafts. Bone consolidation was achieved in 4 to 6 months after the reconstruction.

  20. Two-stage metal-catalyst-free growth of high-quality polycrystalline graphene films on silicon nitride substrates.

    PubMed

    Chen, Jianyi; Guo, Yunlong; Wen, Yugeng; Huang, Liping; Xue, Yunzhou; Geng, Dechao; Wu, Bin; Luo, Birong; Yu, Gui; Liu, Yunqi

    2013-02-20

    By using two-stage, metal-catalyst-free chemical vapor deposition (CVD), it is demonstrated that high-quality polycrystalline graphene films can directly grow on silicon nitride substrates. The carrier mobility can reach about 1500 cm(2) V(-1) s(-1) , which is about three times the value of those grown on SiO(2) /Si substrates, and also is better than some examples of metal-catalyzed graphene, reflecting the good quality of the graphene lattice.

  1. Traumatic tibialis anterior tendon rupture: treatment with a two-stage silicone tube and an interposition hamstring tendons graft protocol.

    PubMed

    Kontogeorgakos, Vasileios; Koutalos, Antonios; Hantes, Michael; Manoudis, Gregory; Badras, Leonidas; Malizos, Konstantinos

    2015-03-01

    A novel technique for managing ruptured tibialis anterior tendon complicated by infection and tendon substance loss in a young adult is described. A two-stage reconstruction technique with a silicon tube and tendon autograft was performed. At first, after local control of the infection, scar excision and placement of a silicone tube was performed. Ten weeks later, ipsilateral hamstrings tendons were harvested and bridged the 7 cm tendon gap. Eighteen months later, the patient has excellent clinical and functional outcome.

  2. Feasibility of hydrogen production from ripened fruits by a combined two-stage (dark/dark) fermentation system.

    PubMed

    Hwang, Jae-Hoon; Choi, Jeong-A; Abou-Shanab, Reda A I; Min, Booki; Song, Hocheol; Kim, Yongje; Lee, Eung Seok; Jeon, Byong-Hun

    2011-01-01

    Anaerobic fermentation for hydrogen (H2) production was studied in a two-stage fermentation system fed with different ripened fruit feedstocks (apple, pear, and grape). Among the feedstocks, ripened apple was the most efficient substrate for cumulative H2 production (4463.7 mL-H2 L(-1)-culture) with a maximum H2 yield (2.2 mol H2 mol(-1) glucose) in the first stage at a hydraulic retention time (HRT) of 18 h. The additional cumulative biohydrogen (3337.4 mL-H2 L(-1)-culture) was produced in the second stage with the reused residual substrate from the first stage. The major byproducts in this study were butyrate, acetate, and ethanol, and butyrate was dominant among them in all test runs. During the two-stage system, the energy efficiency (H(2) conversion) obtained from mixed ripened fruits (RF) increased from 4.6% (in the first stage) to 15.5% (in the second stage), which indicated the energy efficiency can be improved by combined hydrogen production process. The RF could be used as substrates for biohydrogen fermentation in a two-stage (dark/dark) fermentation system.

  3. Comparative assessment of single-stage and two-stage anaerobic digestion for the treatment of thin stillage.

    PubMed

    Nasr, Noha; Elbeshbishy, Elsayed; Hafez, Hisham; Nakhla, George; El Naggar, M Hesham

    2012-05-01

    A comparative evaluation of single-stage and two-stage anaerobic digestion processes for biomethane and biohydrogen production using thin stillage was performed to assess the impact of separating the acidogenic and methanogenic stages on anaerobic digestion. Thin stillage, the main by-product from ethanol production, was characterized by high total chemical oxygen demand (TCOD) of 122 g/L and total volatile fatty acids (TVFAs) of 12 g/L. A maximum methane yield of 0.33 L CH(4)/gCOD(added) (STP) was achieved in the two-stage process while a single-stage process achieved a maximum yield of only 0.26 L CH(4)/gCOD(added) (STP). The separation of acidification stage increased the TVFAs to TCOD ratio from 10% in the raw thin stillage to 54% due to the conversion of carbohydrates into hydrogen and VFAs. Comparison of the two processes based on energy outcome revealed that an increase of 18.5% in the total energy yield was achieved using two-stage anaerobic digestion.

  4. Two-stage pervaporation process for effective in situ removal acetone-butanol-ethanol from fermentation broth.

    PubMed

    Cai, Di; Hu, Song; Miao, Qi; Chen, Changjing; Chen, Huidong; Zhang, Changwei; Li, Ping; Qin, Peiyong; Tan, Tianwei

    2017-01-01

    Two-stage pervaporation for ABE recovery from fermentation broth was studied to reduce the energy cost. The permeate after the first stage in situ pervaporation system was further used as the feedstock in the second stage of pervaporation unit using the same PDMS/PVDF membrane. A total 782.5g/L of ABE (304.56g/L of acetone, 451.98g/L of butanol and 25.97g/L of ethanol) was achieved in the second stage permeate, while the overall acetone, butanol and ethanol separation factors were: 70.7-89.73, 70.48-84.74 and 9.05-13.58, respectively. Furthermore, the theoretical evaporation energy requirement for ABE separation in the consolidate fermentation, which containing two-stage pervaporation and the following distillation process, was estimated less than ∼13.2MJ/kg-butanol. The required evaporation energy was only 36.7% of the energy content of butanol. The novel two-stage pervaporation process was effective in increasing ABE production and reducing energy consumption of the solvents separation system.

  5. Reducing sample sizes in two-stage phase II cancer trials by using continuous tumour shrinkage end-points.

    PubMed

    Wason, James M S; Mander, Adrian P; Eisen, Tim G

    2011-05-01

    Reducing the number of patients required for a clinical trial is important for shortening development time. Phase II cancer trials assess the tumour-shrinking effect of a novel compound through a binary end-point formed from the percentage change in total lesion diameter. We compare single-arm two-stage designs which use the binary end-point to those which directly use the continuous end-point. Using the continuous end-point results in lower expected and maximum sample sizes. For larger trials the reduction is around 37%. This assumes that the dichotomisation point of the continuous end-point is chosen to give the best sample size, with the trial design using the binary end-point performing even worse otherwise. We consider a previous trial designed using a Simon two-stage design and show that if the continuous end-point had been used, the expected and maximum sample sizes of the trial would be reduced by around 50%. Using the continuous end-point in a two-stage cancer trial results in large sample size reductions. The methods discussed in this paper work best when the number of complete responses is low, as is true in several types of cancer. We discuss what could be done if this is not the case.

  6. Two-stage (photoautotrophy and heterotrophy) cultivation enables efficient production of bioplastic poly-3-hydroxybutyrate in auto-sedimenting cyanobacterium.

    PubMed

    Monshupanee, Tanakarn; Nimdach, Palida; Incharoensakdi, Aran

    2016-11-15

    Sustainable production of bioplastics by heterotrophic microbes has been restricted by the limited resources of organic substrates and the energy required for biomass harvest. Here, the easy-to-harvest cyanobacterium (Chlorogloea fritschii TISTR 8527), from which the biomass instantaneously settled to the bottom of liquid culture, was utilized to produce poly-3-hydroxybutyrate (PHB) using a two-stage cultivation strategy. The cells were first pre-grown under normal photoautotrophy to increase their biomass and then recultivated under a heterotrophic condition with a single organic substrate to produce the product. Through optimization of this two-stage cultivation, the mass conversion efficiency of acetate substrate to PHB was obtained at 51 ± 7% (w/w), the comparable level to the theoretical biochemical conversion efficiency of acetate to PHB. This two-stage cultivation that efficiently converted the substrate to the product, concurrent with a reduced culture biomass, may be applicable for the production of other biopolymers by cyanobacteria.

  7. On Simon's two-stage design for single-arm phase IIA cancer clinical trials under beta-binomial distribution.

    PubMed

    Liu, Junfeng; Lin, Yong; Shih, Weichung Joe

    2010-05-10

    Simon (Control. Clin. Trials 1989; 10:1-10)'s two-stage design has been broadly applied to single-arm phase IIA cancer clinical trials in order to minimize either the expected or the maximum sample size under the null hypothesis of drug inefficacy, i.e. when the pre-specified amount of improvement in response rate (RR) is not expected to be observed. This paper studies a realistic scenario where the standard and experimental treatment RRs follow two continuous distributions (e.g. beta distribution) rather than two single values. The binomial probabilities in Simon's (Control. Clin. Trials 1989; 10:1-10) design are replaced by prior predictive Beta-binomial probabilities that are the ratios of two beta functions and domain-restricted RRs involve incomplete beta functions to induce the null hypothesis acceptance probability. We illustrate that Beta-binomial mixture model based two-stage design retains certain desirable properties for hypothesis testing purpose. However, numerical results show that such designs may not exist under certain hypothesis and error rate (type I and II) setups within maximal sample size approximately 130. Furthermore, we give theoretical conditions for asymptotic two-stage design non-existence (sample size goes to infinity) in order to improve the efficiency of design search and to avoid needless searching.

  8. [Using a two-stage SBR process for removal of organics and nitrification-denitrification via nitrite].

    PubMed

    Zeng, Wei; Peng, Yongzhen; Wang, Shuying; Zhang, Naidong

    2002-03-01

    High efficiency removal of organics and nitrogen by using a two-stage SBR process was introduced in this paper. Most of organics was removed in the first stage SBR reactor(SBR1) under the aerobic condition. Subsequently the second stage SBR reactor(SBR2) firstly operated under the aerabic condition for simultaneous nitrification and removal of a small amount of residual organics. Nitrification was controlled to the nitrite-type nitrification. Then denitrification happened in SBR2 under the anoxic condition. The petrochemical industry wastewater was used as external carbon sources in the denitrification. The experimental results indicated that in a two-stage SBR system, two kinds of biomass with the different function existed in the different reactors, which was beneficial to improve the treatment efficiency. The effluent COD reduced again because SBR2 removed COD which was left in SBR1 effluent. It resisted the disturbance of the high organic loading to nitrification. Consequently, as compared to a single SBR process, a two-stage SBR not only improved the treatment efficiency, but also saved the energy cost.

  9. Reaction dynamics under confinement: an exact path integral treatment of a two-stage model of stochastic gene expression

    NASA Astrophysics Data System (ADS)

    Sharma, Rati; Cherayil, Binny J.

    2013-10-01

    Gene expression in living systems is inherently stochastic, and tends to produce varying numbers of proteins over repeated cycles of transcription and translation. In this paper, an expression is derived for the steady-state protein number distribution starting from a two-stage kinetic model of the gene expression process involving p proteins and r mRNAs. The derivation is based on an exact path integral evaluation of the joint distribution, P(p,r,t), of p and r at time t, which can be expressed in terms of the coupled Langevin equations for p and r that represent the two-stage model in continuum form. The steady-state distribution of p alone, P(p), is obtained from P(p,r,t) (a bivariate Gaussian) by integrating out the r degrees of freedom and taking the limit t → ∞. P(p) is found to be proportional to the product of a Gaussian and a complementary error function. It provides a generally satisfactory fit to simulation data on the same two-stage process when the translational efficiency (a measure of intrinsic noise levels in the system) is relatively low; it is less successful as a model of the data when the translational efficiency (and noise levels) are high.

  10. Evaluation of aeration pretreatment to prepare an inoculum for the two-stage hydrogen and methane production process.

    PubMed

    Giordano, Andrea; Sarli, Valentina; Lavagnolo, Maria Cristina; Spagni, Alessandro

    2014-08-01

    This study evaluates the effect of aeration pretreatment to prepare an inoculum for H₂ and CH₄ production in a two-stage process. Moreover, the biochemical hydrogen potential and biochemical methane potential of waste from the food industry in a two-stage process was assessed. The results confirmed the possibility of using an aerobic stress for selecting a hydrogen-producing inoculum. The inoculum was fairly stable since no hydrogenotrophic-methanogenic activity was observed in 25 days. The yields measured using glucose as substrate were of approximately 160 and 280 N mL(H₂) g(COD⁻¹) of glucose for hydrogen and methane, respectively, which are in agreement with other studies using heat-shock for the pretreatment of the inoculum. When waste of the food industry (wheat milling) was used as substrate, a lower H₂ yield was achieved by the aerobically-pretreated inoculum if compared to heat-shock; however, when combined with methane production in a two-stage process, much higher CH₄ yield was achieved.

  11. Two-stage (photoautotrophy and heterotrophy) cultivation enables efficient production of bioplastic poly-3-hydroxybutyrate in auto-sedimenting cyanobacterium

    PubMed Central

    Monshupanee, Tanakarn; Nimdach, Palida; Incharoensakdi, Aran

    2016-01-01

    Sustainable production of bioplastics by heterotrophic microbes has been restricted by the limited resources of organic substrates and the energy required for biomass harvest. Here, the easy-to-harvest cyanobacterium (Chlorogloea fritschii TISTR 8527), from which the biomass instantaneously settled to the bottom of liquid culture, was utilized to produce poly-3-hydroxybutyrate (PHB) using a two-stage cultivation strategy. The cells were first pre-grown under normal photoautotrophy to increase their biomass and then recultivated under a heterotrophic condition with a single organic substrate to produce the product. Through optimization of this two-stage cultivation, the mass conversion efficiency of acetate substrate to PHB was obtained at 51 ± 7% (w/w), the comparable level to the theoretical biochemical conversion efficiency of acetate to PHB. This two-stage cultivation that efficiently converted the substrate to the product, concurrent with a reduced culture biomass, may be applicable for the production of other biopolymers by cyanobacteria. PMID:27845413

  12. Influence of bulking agents on physical, chemical, and microbiological properties during the two-stage composting of green waste.

    PubMed

    Zhang, Lu; Sun, Xiangyang

    2016-02-01

    A recyclable organic bulking agent (BA) that can be screened and was developed to optimize green waste (GW) composting. This study investigated the use of wood chips (WC) (at 0%, 15%, and 25%) and/or composted green waste (CGW) (at 0%, 25%, and 35%) as the BAs in the two-stage composting of GW. The combined addition of WC and CGW improved the conditions of composting process and the quality of compost product in terms of composting temperature, porosity, water retention, particle-size distribution, pH, electrical conductivity (EC), cation exchange capacity (CEC), nitrogen losses, humification indices, microbial numbers, enzyme activities, macro- and micro-nutrient contents, and toxicity to germinating seeds. The compost matured in only 22days with the optimized two-stage composting method rather than in the 90-270days typically required for traditional composting. The optimal two-stage composting process and the best quality of compost product were obtained with the combined addition of 15% WC and 35% CGW.

  13. Upstream process optimization of polyhydroxybutyrate (PHB) by Alcaligenes latus using two-stage batch and fed-batch fermentation strategies.

    PubMed

    Wang, Bingqing; Sharma-Shivappa, Ratna R; Olson, Jonathan W; Khan, Saad A

    2012-11-01

    This research focused on optimizing the upstream process time for production of polyhydroxybutyrate (PHB) from sucrose by two-stage batch and fed-batch fermentation with Alcaligenes latus ATCC 29714. The study included selection of strain, two-stage batch fermentations with different time points for switching to nitrogen limited media (14, 16 or 18 h) and fed-batch fermentations with varied time points (similar to two stage) for introducing nitrogen limited media. The optimal strain to produce PHB using sucrose as carbon source was A. latus ATCC 29714 with maximum-specific growth rate of 0.38 ± 0.01 h(-1) and doubling time of 1.80 ± 0.05 h. Inducing nitrogen limitation at 16 h and ending second stage at 26 h gave optimal performance for PHB production, resulting in a PHB content of 46.7 ± 12.2 % (g PHB per g dry cell weight) at the end of fermentation. This was significantly higher (P ≤ 0.05) (approximately 7 %) than the corresponding fed batch run in which nitrogen limitation was initiated at 16 h.

  14. A priori evaluation of two-stage cluster sampling for accuracy assessment of large-area land-cover maps

    USGS Publications Warehouse

    Wickham, J.D.; Stehman, S.V.; Smith, J.H.; Wade, T.G.; Yang, L.

    2004-01-01

    Two-stage cluster sampling reduces the cost of collecting accuracy assessment reference data by constraining sample elements to fall within a limited number of geographic domains (clusters). However, because classification error is typically positively spatially correlated, within-cluster correlation may reduce the precision of the accuracy estimates. The detailed population information to quantify a priori the effect of within-cluster correlation on precision is typically unavailable. Consequently, a convenient, practical approach to evaluate the likely performance of a two-stage cluster sample is needed. We describe such an a priori evaluation protocol focusing on the spatial distribution of the sample by land-cover class across different cluster sizes and costs of different sampling options, including options not imposing clustering. This protocol also assesses the two-stage design's adequacy for estimating the precision of accuracy estimates for rare land-cover classes. We illustrate the approach using two large-area, regional accuracy assessments from the National Land-Cover Data (NLCD), and describe how the a priorievaluation was used as a decision-making tool when implementing the NLCD design.

  15. Simulation-based medical education in pediatrics.

    PubMed

    Lopreiato, Joseph O; Sawyer, Taylor

    2015-01-01

    The use of simulation-based medical education (SBME) in pediatrics has grown rapidly over the past 2 decades and is expected to continue to grow. Similar to other instructional formats used in medical education, SBME is an instructional methodology that facilitates learning. Successful use of SBME in pediatrics requires attention to basic educational principles, including the incorporation of clear learning objectives. To facilitate learning during simulation the psychological safety of the participants must be ensured, and when done correctly, SBME is a powerful tool to enhance patient safety in pediatrics. Here we provide an overview of SBME in pediatrics and review key topics in the field. We first review the tools of the trade and examine various types of simulators used in pediatric SBME, including human patient simulators, task trainers, standardized patients, and virtual reality simulation. Then we explore several uses of simulation that have been shown to lead to effective learning, including curriculum integration, feedback and debriefing, deliberate practice, mastery learning, and range of difficulty and clinical variation. Examples of how these practices have been successfully used in pediatrics are provided. Finally, we discuss the future of pediatric SBME. As a community, pediatric simulation educators and researchers have been a leading force in the advancement of simulation in medicine. As the use of SBME in pediatrics expands, we hope this perspective will serve as a guide for those interested in improving the state of pediatric SBME.

  16. Two-stage rifting of Zealandia-Australia-Antarctica: Evidence from 40Ar/39Ar thermochronometry of the Sisters shear zone, Stewart Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Kula, Joseph; Tulloch, Andy; Spell, Terry L.; Wells, Michael L.

    2007-05-01

    The Sisters shear zone is a newly discovered Late Cretaceous detachment fault system exposed for 40 km along the southeast coast of Stewart Island, southernmost New Zealand. Footwall rocks consist of variably deformed ca. 310 and 105 Ma granites that range from undeformed to protomylonite, mylonite, and ultramylonite. The hanging wall includes non-marine conglomerate and brittley deformed granite. K-feldspar thermochronometry of the footwall indicates moderately rapid cooling (20 30 C°/m.y.) due to tectonic denudation over the interval ca. 89 82 Ma. Return to slow cooling at 82 Ma coincides with the age of the oldest seafloor adjacent to the Campbell Plateau and reflects the mechanical transition from continental extension to lithospheric rupture and formation of the Pacific-Antarctic Ridge. Our findings support a two-stage rift model for continental breakup of this part of the Gondwana margin. Stage one (ca. 101 88 Ma) is the northward propagation of continental extension and the Tasman Ridge as recorded in mylonite dredged from the Ross Sea and the Paparoa core complex. Stage two (ca. 89 82 Ma) is extension between the Campbell Plateau and West Antarctica leading to formation of the Pacific-Antarctic Ridge.

  17. Assessment of Human Patient Simulation-Based Learning

    PubMed Central

    Schwartz, Catrina R.; Odegard, Peggy Soule; Hammer, Dana P.; Seybert, Amy L.

    2011-01-01

    The most common types of assessment of human patient simulation are satisfaction and/or confidence surveys or tests of knowledge acquisition. There is an urgent need to develop valid, reliable assessment instruments related to simulation-based learning. Assessment practices for simulation-based activities in the pharmacy curricula are highlighted, with a focus on human patient simulation. Examples of simulation-based assessment activities are reviewed according to type of assessment or domain being assessed. Assessment strategies are suggested for faculty members and programs that use simulation-based learning. PMID:22345727

  18. Assessment of human patient simulation-based learning.

    PubMed

    Bray, Brenda S; Schwartz, Catrina R; Odegard, Peggy Soule; Hammer, Dana P; Seybert, Amy L

    2011-12-15

    The most common types of assessment of human patient simulation are satisfaction and/or confidence surveys or tests of knowledge acquisition. There is an urgent need to develop valid, reliable assessment instruments related to simulation-based learning. Assessment practices for simulation-based activities in the pharmacy curricula are highlighted, with a focus on human patient simulation. Examples of simulation-based assessment activities are reviewed according to type of assessment or domain being assessed. Assessment strategies are suggested for faculty members and programs that use simulation-based learning.

  19. SU-E-J-128: Two-Stage Atlas Selection in Multi-Atlas-Based Image Segmentation

    SciTech Connect

    Zhao, T; Ruan, D

    2015-06-15

    Purpose: In the new era of big data, multi-atlas-based image segmentation is challenged by heterogeneous atlas quality and high computation burden from extensive atlas collection, demanding efficient identification of the most relevant atlases. This study aims to develop a two-stage atlas selection scheme to achieve computational economy with performance guarantee. Methods: We develop a low-cost fusion set selection scheme by introducing a preliminary selection to trim full atlas collection into an augmented subset, alleviating the need for extensive full-fledged registrations. More specifically, fusion set selection is performed in two successive steps: preliminary selection and refinement. An augmented subset is first roughly selected from the whole atlas collection with a simple registration scheme and the corresponding preliminary relevance metric; the augmented subset is further refined into the desired fusion set size, using full-fledged registration and the associated relevance metric. The main novelty of this work is the introduction of an inference model to relate the preliminary and refined relevance metrics, based on which the augmented subset size is rigorously derived to ensure the desired atlases survive the preliminary selection with high probability. Results: The performance and complexity of the proposed two-stage atlas selection method were assessed using a collection of 30 prostate MR images. It achieved comparable segmentation accuracy as the conventional one-stage method with full-fledged registration, but significantly reduced computation time to 1/3 (from 30.82 to 11.04 min per segmentation). Compared with alternative one-stage cost-saving approach, the proposed scheme yielded superior performance with mean and medium DSC of (0.83, 0.85) compared to (0.74, 0.78). Conclusion: This work has developed a model-guided two-stage atlas selection scheme to achieve significant cost reduction while guaranteeing high segmentation accuracy. The benefit

  20. Exprimental Results of the First Two Stages of an Advanced Transonic Core Compressor Under Isolated and Multi-Stage Conditions.

    NASA Technical Reports Server (NTRS)

    Prahst, Patricia S.; Kulkarni, Sameer; Sohn, Ki H.

    2015-01-01

    NASA's Environmentally Responsible Aviation (ERA) Program calls for investigation of the technology barriers associated with improved fuel efficiency for large gas turbine engines. Under ERA, the highly loaded core compressor technology program attempts to realize the fuel burn reduction goal by increasing overall pressure ratio of the compressor to increase thermal efficiency of the engine. Study engines with overall pressure ratio of 60 to 70 are now being investigated. This means that the high pressure compressor would have to almost double in pressure ratio while keeping a high level of efficiency. NASA and GE teamed to address this challenge by testing the first two stages of an advanced GE compressor designed to meet the requirements of a very high pressure ratio core compressor. Previous test experience of a compressor which included these front two stages indicated a performance deficit relative to design intent. Therefore, the current rig was designed to run in 1-stage and 2-stage configurations in two separate tests to assess whether the bow shock of the second rotor interacting with the upstream stage contributed to the unpredicted performance deficit, or if the culprit was due to interaction of rotor 1 and stator 1. Thus, the goal was to fully understand the stage 1 performance under isolated and multi-stage conditions, and additionally to provide a detailed aerodynamic data set for CFD validation. Full use was made of steady and unsteady measurement methods to understand fluid dynamics loss source mechanisms due to rotor shock interaction and endwall losses. This paper will present the description of the compressor test article and its measured performance and operability, for both the single stage and two stage configurations. We focus the paper on measurements at 97% corrected speed with design intent vane setting angles.

  1. Novel two-stage piezoelectric-based electrical energy generators for low and variable speed rotary machinery

    NASA Astrophysics Data System (ADS)

    Rastegar, J.; Murray, R.

    2010-04-01

    A novel class of two-stage piezoelectric-based electrical energy generators is presented for rotary machinery in which the input speed is low and varies significantly, even reversing. Applications include wind mills, turbo-machinery for harvesting tidal flows, etc. Current technology using magnet-and-coil rotary generators require gearing or similar mechanisms to increase the input speed and make the generation cycle efficient. Variable speed-control mechanisms are also usually needed to achieve high mechanical to electrical energy conversion efficiency. Presented here are generators that do not require gearing or speed control mechanisms, significantly reducing complexity and cost, especially pertaining to maintenance and service. Additionally, these new generators can expand the application of energy harvesting to much slower input speeds than current technology allows. The primary novelty of this technology is the two-stage harvesting system. The harvesting environment (e.g. wind) provides input to the primary system, which is then used to successively excite a secondary system of vibratory elements into resonance - like strumming a guitar. The key advantage is that by having two decoupled systems, the low-andvarying- speed input can be converted into constant and much higher frequency vibrations. Energy is then harvested from the secondary system's vibrating elements with high efficiency using piezoelectric elements or magnet-and-coil generators. These new generators are uncomplicated, and can efficiently operate at widely varying and even reversing input speeds. Conceptual designs are presented for a number of generators and subsystems (e.g. for passing mechanical energy from the primary to the secondary system). Additionally, analysis of a complete two-stage energy harvesting system is discussed with predictions of performance and efficiency.

  2. New LANL Group M-7 two-stage gun: Double-diaphragm and wrap-around gas breech

    SciTech Connect

    Sheffield, S.A.; Martinez, A.R.

    1992-01-01

    A new two-stage gun is being installed in a high explosive testing facility at Los Alamos National Laboratory for the purpose of subjecting insensitive high explosives to controlled projectile impacts so that shock-to-detonation transition can be studied in detail. This gun has been patterned after guns designed by Alois Stilp at Ernst Mach Institut (EMI) in Freiburg and Wintersweiler, Germany. Several changes were made to adapt the design to our needs. The gun has a 100-mm diameter pump tube and 33-mm and 50-mm diameter launch tubes; both pump and launch tubes are 7.6 m long. We plan to use only helium as the reservoir gas. Large hydraulic clamps hold the gun together in three places during a shot; these are located on both sides of the transition section and at the breech. These clamps make gun conversions to different setups relatively simple, i.e., the two-stage gun can be converted into a single-stage gun. A gas breech has been designed which can be operated in either wrap-around or double-diaphragm mode with a maximum operating pressure of 15,000 psi. Two-stage gun calculations indicate that in the gas breech configuration, projectile velocities up to 4 km/s can be obtained using helium in both the breech and the reservoir. The gun has been fabricated and is being installed at the present time. Testing is expected to begin in early 1993 if the startup difficulties do not become excessive.

  3. New LANL Group M-7 two-stage gun: Double-diaphragm and wrap-around gas breech

    SciTech Connect

    Sheffield, S.A.; Martinez, A.R.

    1992-10-01

    A new two-stage gun is being installed in a high explosive testing facility at Los Alamos National Laboratory for the purpose of subjecting insensitive high explosives to controlled projectile impacts so that shock-to-detonation transition can be studied in detail. This gun has been patterned after guns designed by Alois Stilp at Ernst Mach Institut (EMI) in Freiburg and Wintersweiler, Germany. Several changes were made to adapt the design to our needs. The gun has a 100-mm diameter pump tube and 33-mm and 50-mm diameter launch tubes; both pump and launch tubes are 7.6 m long. We plan to use only helium as the reservoir gas. Large hydraulic clamps hold the gun together in three places during a shot; these are located on both sides of the transition section and at the breech. These clamps make gun conversions to different setups relatively simple, i.e., the two-stage gun can be converted into a single-stage gun. A gas breech has been designed which can be operated in either wrap-around or double-diaphragm mode with a maximum operating pressure of 15,000 psi. Two-stage gun calculations indicate that in the gas breech configuration, projectile velocities up to 4 km/s can be obtained using helium in both the breech and the reservoir. The gun has been fabricated and is being installed at the present time. Testing is expected to begin in early 1993 if the startup difficulties do not become excessive.

  4. A 45 PS Time-Interval Counter Board with a PCI Interface

    DTIC Science & Technology

    2007-11-01

    39th Annual Precise Time and Time Interval (PTTI) Meeting A 45 PS TIME-INTERVAL COUNTER BOARD WITH A PCI INTERFACE Ryszard Szplet...precise time-interval and frequency counter board with PCI interface. The counter utilizes two two-stage interpolators that provide 45 ps resolution...synthesis and for generation of the four -phase clock used in the first interpolation stage. The fast arithmetic carry chains are used as high

  5. Inhibitory Effects of Gymnema (Gymnema sylvestre) Leaves on Tumour Promotion in Two-Stage Mouse Skin Carcinogenesis.

    PubMed

    Yasukawa, Ken; Okuda, Sakiko; Nobushi, Yasuhito

    2014-01-01

    Ethanol extracts of gymnema (Gymnema sylvestre) leaves exhibited marked antitumour-promoting activity in an in vivo two-stage carcinogenesis test in mice using 7,12-dimethylbenz[a]anthracene as an initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as a promoter. From the active fraction of the ethanol extract of the gymnema leaves, three triterpenoids were isolated and identified. These compounds were evaluated for their inhibitory effects on TPA-induced inflammation (1 µg/ear) in mice. The tested compounds showed marked anti-inflammatory effects, with a 50% inhibitory dose of 50-555 nmol/ear.

  6. Operating characteristics of a Simon two-stage phase II clinical trial design incorporating continuous toxicity monitoring.

    PubMed

    Ray, H E; Rai, S N

    2012-01-01

    Phase II clinical trials are usually designed to measure efficacy, but safety is also an important end point. Previous authors recommended a method to monitor toxic events after each patient is enrolled, which is also known as continuously monitoring the toxicity. In this work, we investigate combining the usual Simon two-stage design to monitor response with the continuous toxicity monitoring methodology. Theoretical justification is given for the nominal size, probability of early termination, and average sample size under the null hypothesis of the combined testing procedure. A series of simulations are performed to investigate the performance of the combined procedure.

  7. An Overview of the VHITAL Program: A Two-Stage Bismuth Fed Very High Specific Impulse Thruster with Anode Layer

    NASA Technical Reports Server (NTRS)

    Sengupta, Anita; Marrese-Reading, Colleen; Capelli, Mark; Scharfe, David; Tverdokhlebov, Sergey; Semenkin, Sasha; Tverdokhlebov, Oleg; Boyd, Ian; Keidar, Michael; Yalin, Azer; Markusic, Tom; Polzin, Kurt

    2005-01-01

    The Very High Isp Thruster with Anode Layer (VHITAL) is a two stage Hall thruster program that is a part of NASA's Prometheus Program in NASA's New Exploration Systems Mission Directorate (ESMD). It is a potentially viable low-cost alternative to ion engines for near-term NEP applications with the growth potential to support mid-term and far-term NEP missions... This paper will present an overview of the thruster fabrication, pre-existing TAL 160 demonstration, feed system development, lifetime assessment, contamination assessment, and mission study activities performed to date.

  8. Two-stage plasma gun based on a gas discharge with a self-heating hollow emitter.

    PubMed

    Vizir, A V; Tyunkov, A V; Shandrikov, M V; Oks, E M

    2010-02-01

    The paper presents the results of tests of a new compact two-stage bulk gas plasma gun. The plasma gun is based on a nonself-sustained gas discharge with an electron emitter based on a discharge with a self-heating hollow cathode. The operating characteristics of the plasma gun are investigated. The discharge system makes it possible to produce uniform and stable gas plasma in the dc mode with a plasma density up to 3x10(9) cm(-3) at an operating gas pressure in the vacuum chamber of less than 2x10(-2) Pa. The device features high power efficiency, design simplicity, and compactness.

  9. Inhibitory Effects of Gymnema (Gymnema sylvestre) Leaves on Tumour Promotion in Two-Stage Mouse Skin Carcinogenesis

    PubMed Central

    Yasukawa, Ken; Okuda, Sakiko; Nobushi, Yasuhito

    2014-01-01

    Ethanol extracts of gymnema (Gymnema sylvestre) leaves exhibited marked antitumour-promoting activity in an in vivo two-stage carcinogenesis test in mice using 7,12-dimethylbenz[a]anthracene as an initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as a promoter. From the active fraction of the ethanol extract of the gymnema leaves, three triterpenoids were isolated and identified. These compounds were evaluated for their inhibitory effects on TPA-induced inflammation (1 µg/ear) in mice. The tested compounds showed marked anti-inflammatory effects, with a 50% inhibitory dose of 50–555 nmol/ear. PMID:24734106

  10. Anterior cruciate ligament reconstruction tunnel size: causes of tunnel enlargement and implications for single versus two-stage revision reconstruction.

    PubMed

    Rizer, Magda; Foremny, Gregory Brian; Rush, Augustus; Singer, Adam D; Baraga, Michael; Kaplan, Lee D; Jose, Jean

    2017-02-01

    Anterior cruciate ligament (ACL) reconstructions have increased over the past 25 years. The increased incidence of ACL reconstructions has translated into a larger number of graft failures and revision ACL procedures. It is important to understand the causes of graft failure when evaluating for a revision ACL reconstruction and to appreciate changes in tunnel anatomy over time prior to planning revision surgery. In this manuscript, tunnel size for ACL reconstruction and implications for single-stage versus two-stage revision ACL reconstruction will be discussed, as well as causes of tunnel enlargement, including mechanical and biological factors.

  11. Two stage catalytic combustor

    NASA Technical Reports Server (NTRS)

    Alvin, Mary Anne (Inventor); Bachovchin, Dennis (Inventor); Smeltzer, Eugene E. (Inventor); Lippert, Thomas E. (Inventor); Bruck, Gerald J. (Inventor)

    2010-01-01

    A catalytic combustor (14) includes a first catalytic stage (30), a second catalytic stage (40), and an oxidation completion stage (49). The first catalytic stage receives an oxidizer (e.g., 20) and a fuel (26) and discharges a partially oxidized fuel/oxidizer mixture (36). The second catalytic stage receives the partially oxidized fuel/oxidizer mixture and further oxidizes the mixture. The second catalytic stage may include a passageway (47) for conducting a bypass portion (46) of the mixture past a catalyst (e.g., 41) disposed therein. The second catalytic stage may have an outlet temperature elevated sufficiently to complete oxidation of the mixture without using a separate ignition source. The oxidation completion stage is disposed downstream of the second catalytic stage and may recombine the bypass portion with a catalyst exposed portion (48) of the mixture and complete oxidation of the mixture. The second catalytic stage may also include a reticulated foam support (50), a honeycomb support, a tube support or a plate support.

  12. Application of game theory on parameter optimization of the novel two-stage Nash nonlinear grey Bernoulli model

    NASA Astrophysics Data System (ADS)

    Hsin, Pei-Han; Chen, Chun-I.

    2015-10-01

    In grey prediction modeling, there are three parameters in nonlinear grey Bernoulli model (NGBM), including the power n, the coefficient p and the length of raw data used to construct grey forecasting model. Nash NGBM only optimizes n and p by the iterated elimination of weakly dominated strategies of game theory. To optimize above three parameters, this study develops a two-stage game for NNGBM (abbreviated as two-stage NNGBM). In the first stage, find the Nash equilibrium for each possible game. In the second stage, use Minimax principle to find the optimal left topological sequence which has the best forecasting performance. Then, obtain Nash equilibrium which consists of these three parameters. This study also proves that the traditional GM(1, 1), optimal p GM(1, 1) and NGBM(1, 1) are the special cases of the proposed model. In order to show the feasibility of this research, the proposed method is applied to the forecasting of Taiwan's GDP. The results show that five elements in raw data sequence are optimal topological length for constructing NNGBM in the case of Taiwan's GDP forecasting.

  13. Mining Gold Dust under the Genome Wide Significance Level: A Two-Stage Approach to Analysis of GWAS

    PubMed Central

    Shi, Gang; Boerwinkle, Eric; Morrison, Alanna C.; Gu, C. Charles; Chakravarti, Aravinda; Rao, DC

    2013-01-01

    We propose a two-stage approach to analyze genome-wide association (GWA) data in order to identify a set of promising single-nucleotide polymorphisms (SNPs). In stage one, we select a list of top signals from single SNP analyses by controlling false discovery rate (FDR). In stage two, we use the least absolute shrinkage and selection operator (LASSO) regression to reduce false positives. The proposed approach was evaluated using simulated quantitative traits based on genome-wide SNP data on 8,861 Caucasian individuals from the Atherosclerosis Risk in Communities (ARIC) Study. Our first stage, targeted at controlling false negatives, yields better power than using Bonferroni corrected significance level. The LASSO regression reduces the number of significant SNPs in stage two: it reduces false positive SNPs and it reduces true positive SNPs also at simulated causal loci due to linkage disequilibrium. Interestingly, the LASSO regression preserves the power from stage one, i.e., the number of causal loci detected from the LASSO regression in stage two is almost the same as in stage one, while reducing false positives further. Real data on systolic blood pressure in the ARIC study was analyzed using our two-stage approach which identified two significant SNPs, one of which was reported to be genome-significant in a meta-analysis containing a much larger sample size. On the other hand, a single SNP association scan did not yield any significant results. PMID:21254218

  14. Speech enhancement via two-stage dual tree complex wavelet packet transform with a speech presence probability estimator.

    PubMed

    Sun, Pengfei; Qin, Jun

    2017-02-01

    In this paper, a two-stage dual tree complex wavelet packet transform (DTCWPT) based speech enhancement algorithm has been proposed, in which a speech presence probability (SPP) estimator and a generalized minimum mean squared error (MMSE) estimator are developed. To overcome the drawback of signal distortions caused by down sampling of wavelet packet transform (WPT), a two-stage analytic decomposition concatenating undecimated wavelet packet transform (UWPT) and decimated WPT is employed. An SPP estimator in the DTCWPT domain is derived based on a generalized Gamma distribution of speech, and Gaussian noise assumption. The validation results show that the proposed algorithm can obtain enhanced perceptual evaluation of speech quality (PESQ), and segmental signal-to-noise ratio (SegSNR) at low signal-to-noise ratio (SNR) nonstationary noise, compared with four other state-of-the-art speech enhancement algorithms, including optimally modified log-spectral amplitude (OM-LSA), soft masking using a posteriori SNR uncertainty (SMPO), a posteriori SPP based MMSE estimation (MMSE-SPP), and adaptive Bayesian wavelet thresholding (BWT).

  15. Two-stage high-rate biogas (H2 and CH4) production from food waste using anaerobic mixed microflora

    NASA Astrophysics Data System (ADS)

    Xu, K.; Lee, D.; Kobayashi, T.; Ebie, Y.; Li, Y.; Inamori, Y.

    2010-12-01

    To achieve the high-rate H2 and CH4 production from food waste using fermentative anaerobic microflora, the effects of carbonate-alkalinity in the recirculated digestion sludge on continuous two-stage fermentation were investigated. Higher H2 production rate of 2.9 L-H2/L/day was achieved at the recycle ratio of 1.0 in an alkalinity range of 9000 to 10000 mg-CaCO3/L. The maximum CH4 production rate was stably maintained at the range of 1.85 to 1.88 L-CH4/L/day without alkalinity change. Carbonate alkalinity in digestion sludge could reduce the H2 partial pressure in the headspace of the fermentation reactors, and improve a biogas production capacity in the two-stage fermentation process. The average volatile solids degradation rate in the overall process increased as the digestion sludge recycle increased from 0.5 to 1.0. These results show that the alkalinity in recycle of the digestion sludge is crucial factor in determining biogas (H2 and CH4) production capacity and reducing the total solids.

  16. ADM1-based modeling of methane production from acidified sweet sorghum extract in a two stage process.

    PubMed

    Antonopoulou, Georgia; Gavala, Hariklia N; Skiadas, Ioannis V; Lyberatos, Gerasimos

    2012-02-01

    The present study focused on the application of the Anaerobic Digestion Model 1 on the methane production from acidified sorghum extract generated from a hydrogen producing bioreactor in a two-stage anaerobic process. The kinetic parameters for hydrogen and volatile fatty acids consumption were estimated through fitting of the model equations to the data obtained from batch experiments. The simulation of the continuous reactor performance at all HRTs tested (20, 15, and 10d) was very satisfactory. Specifically, the largest deviation of the theoretical predictions against the experimental data was 12% for the methane production rate at the HRT of 20d while the deviation values for the 15 and 10d HRT were 1.9% and 1.1%, respectively. The model predictions regarding pH, methane percentage in the gas phase and COD removal were in very good agreement with the experimental data with a deviation less than 5% for all steady states. Therefore, the ADM1 is a valuable tool for process design in the case of a two-stage anaerobic process as well.

  17. Microbial decolorization of reactive black-5 in a two-stage anaerobic-aerobic reactor using acclimatized activated textile sludge.

    PubMed

    Mohanty, Sagarika; Dafale, Nishant; Rao, Nageswara Neti

    2006-10-01

    A two-stage anaerobic-aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent was used to degrade reactive black 5 dye (RB-5). The anaerobic step was studied in more detail by varying the dye concentration from 100 to 3000 mg l(-1). The results showed that major decolorization was achieved during the anaerobic process. The time required for decolorization by > 90% increased as the concentration of the dye increased. It was also found that maintaining dissolved oxygen (DO) concentration below 0.5 mg l(-1 )and addition of a co-substrate viz., glucose, facilitates anaerobic decolorization reaction remarkably. An attempt was made to identify the metabolites formed in anaerobic process by using high performance liquid chromatography (HPLC) and UV-VIS spectrophotometry. A plate assay was performed for the detection of dominant decolorizing bacteria. Only a few bacterial colonies with high clearing zones (decolorization zones) were found. The results showed that under anaerobic condition RB-5 molecules were reduced and aromatic amines were generated. The aromatic amine metabolite was partly removed in subsequent aerobic bio-treatment. It was possible to achieve more than 90% decolorization and approximately 46% reduction in amine metabolite concentration through two-stage anaerobic-aerobic treatment after a reaction period of 2 days.

  18. Evaluation of straw as a biofilm carrier in the methanogenic stage of two-stage anaerobic digestion of crop residues.

    PubMed

    Andersson, Jonatan; Björnsson, Lovisa

    2002-10-01

    Straw was evaluated as a biofilm carrier in the methanogenic stage of the two-stage anaerobic digestion of crop residues. Three reactor configurations were studied, a straw-packed-bed reactor, a glass packed-bed reactor and a reactor containing suspended plastic carriers. The reactor with the packed straw bed showed the best results. It had the highest methane production, 5.4 11(-1) d(-1), and the chemical oxygen demand (COD) removal ranged from 73-50% at organic loading rates from 2.4-25 g COD l(-1) d(-1). The degradation pattern of volatile fatty acids showed that the degradation of propionate and longer-chain fatty acids was limiting at higher organic loading rates. A stable effluent pH showed that the packed-bed reactors had good ability to withstand the variations in load and volatile fatty acid concentrations that can occur in the two-stage process. The conclusion is that straw would work very well in the intended application. A further benefit is that straw is a common agricultural waste product and requires only limited resources concerning handling and cost.

  19. Techno-economic assessment of the Mobil Two-Stage Slurry Fischer-Tropsch/ZSM-5 process

    SciTech Connect

    El Sawy, A.; Gray, D.; Neuworth, M.; Tomlinson, G.

    1984-11-01

    A techno-economic assessment of the Mobil Two-Stage Slurry Fischer-Tropsch reactor system was carried out. Mobil bench-scale data were evaluated and scaled to a commercial plant design that produced specification high-octane gasoline and high-cetane diesel fuel. Comparisons were made with three reference plants - a SASOL (US) plant using dry ash Lurgi gasifiers and Synthol synthesis units, a modified SASOL plant with a British Gas Corporation slagging Lurgi gasifier (BGC/Synthol) and a BGC/slurry-phase process based on scaled data from the Koelbel Rheinpreussen-Koppers plant. A conceptual commercial version of the Mobil two-stage process shows a higher process efficiency than a SASOL (US) and a BGC/Synthol plant. The Mobil plant gave lower gasoline costs than obtained from the SASOL (US) and BGC/Synthol versions. Comparison with published data from a slurry-phase Fischer-Tropsch (Koelbel) unit indicated that product costs from the Mobil process were within 6% of the Koelbel values. A high-wax version of the Mobil process combined with wax hydrocracking could produce gasoline and diesel fuel at comparable cost to the lowest values achieved from prior published slurry-phase results. 27 references, 18 figures, 49 tables.

  20. A Comparison of Two-Stage Approaches for Fitting Nonlinear Ordinary Differential Equation (ODE) Models with Mixed Effects

    PubMed Central

    Chow, Sy-Miin; Bendezú, Jason J.; Cole, Pamela M.; Ram, Nilam

    2016-01-01

    Several approaches currently exist for estimating the derivatives of observed data for model exploration purposes, including functional data analysis (FDA), generalized local linear approximation (GLLA), and generalized orthogonal local derivative approximation (GOLD). These derivative estimation procedures can be used in a two-stage process to fit mixed effects ordinary differential equation (ODE) models. While the performance and utility of these routines for estimating linear ODEs have been established, they have not yet been evaluated in the context of nonlinear ODEs with mixed effects. We compared properties of the GLLA and GOLD to an FDA-based two-stage approach denoted herein as functional ordinary differential equation with mixed effects (FODEmixed) in a Monte Carlo study using a nonlinear coupled oscillators model with mixed effects. Simulation results showed that overall, the FODEmixed outperformed both the GLLA and GOLD across all the embedding dimensions considered, but a novel use of a fourth-order GLLA approach combined with very high embedding dimensions yielded estimation results that almost paralleled those from the FODEmixed. We discuss the strengths and limitations of each approach and demonstrate how output from each stage of FODEmixed may be used to inform empirical modeling of young children’s self-regulation. PMID:27391255