Energy Technology Data Exchange (ETDEWEB)
Kearney, D.; Mehos, M.
2010-12-01
Prior to commercial operation, large solar systems in utility-size power plants need to pass a performance acceptance test conducted by the EPC contractor or owners. In lieu of the present absence of engineering code developed for this purpose, NREL has undertaken the development of interim guidelines to provide recommendations for test procedures that can yield results of a high level of accuracy consistent with good engineering knowledge and practice. The fundamental differences between acceptance of a solar power plant and a conventional fossil-fired plant are the transient nature of the energy source and the necessity to utilize an analytical performance model in the acceptance process. These factors bring into play the need to establish methods to measure steady state performance, potential impacts of transient processes, comparison to performance model results, and the possible requirement to test, or model, multi-day performance within the scope of the acceptance test procedure. The power block and BOP are not within the boundaries of this guideline. The current guideline is restricted to the solar thermal performance of parabolic trough systems and has been critiqued by a broad range of stakeholders in CSP development and technology.
Large time behavior of solutions to parabolic equations with Neumann boundary conditions
da Lio, Francesca
2008-03-01
In this paper we are interested in the large time behavior as t-->+[infinity] of the viscosity solutions of parabolic equations with nonlinear Neumann type boundary conditions in connection with ergodic boundary problems which have been recently studied by Barles and the author in [G. Barles, F. Da Lio, On the boundary ergodic problem for fully nonlinear equations in bounded domains with general nonlinear Neumann boundary conditions, Ann. Inst. H. Poincaré Anal. Non Linèaire 22 (5) (2005) 521-541].
Guidelines for reporting parabolic trough solar electric system performance
Energy Technology Data Exchange (ETDEWEB)
Price, H.W.
1997-06-01
The purpose of this activity is to develop a generic methodology which can be used to track and compare the performance of parabolic trough power plants. The approach needs to be general enough to work for all existing and future parabolic trough plant designs, provide meaningful comparisons of year to year performance, and allow for comparisons between dissimilar plant designs. The approach presented here uses the net annual system efficiency as the primary metric for evaluating the performance of parabolic trough power plants. However, given the complex nature of large parabolic trough plants, the net annual system efficiency by itself does not adequately characterize the performance of the plant. The approach taken here is to define a number of additional performance metrics which enable a more comprehensive understanding of overall plant performance.
Fixed point of the parabolic renormalization operator
Lanford III, Oscar E
2014-01-01
This monograph grew out of the authors' efforts to provide a natural geometric description for the class of maps invariant under parabolic renormalization and for the Inou-Shishikura fixed point itself as well as to carry out a computer-assisted study of the parabolic renormalization operator. It introduces a renormalization-invariant class of analytic maps with a maximal domain of analyticity and rigid covering properties and presents a numerical scheme for computing parabolic renormalization of a germ, which is used to compute the Inou-Shishikura renormalization fixed point. Inside, readers will find a detailed introduction into the theory of parabolic bifurcation, Fatou coordinates, Écalle-Voronin conjugacy invariants of parabolic germs, and the definition and basic properties of parabolic renormalization. The systematic view of parabolic renormalization developed in the book and the numerical approach to its study will be interesting to both experts in the field as well as graduate students wishi...
Multirate Numerical Integration for Parabolic PDEs
Savcenco, Valeriu; Savcenco, Eugeniu
2008-09-01
To solve PDE problems with different time scales that are localized in space, multirate time integration is examined. This technique enables one to use large time steps for slowly time-varying spatial regions, and small steps for rapidly varying ones. Multirate time stepping is coupled with the local uniform grid refinement and provides a robust and efficient method for the target problem class. We primarily consider implicit time stepping methods, suitable for parabolic problems. Numerical results are presented for a test problem.
Fabrication and characterization of non-linear parabolic microporous membranes.
Rajasekaran, Pradeep Ramiah; Sharifi, Payam; Wolff, Justin; Kohli, Punit
2015-01-01
Large scale fabrication of non-linear microporous membranes is of technological importance in many applications ranging from separation to microfluidics. However, their fabrication using traditional techniques is limited in scope. We report on fabrication and characterization of non-linear parabolic micropores (PMS) in polymer membranes by utilizing flow properties of fluids. The shape of the fabricated PMS corroborated well with simplified Navier-Stokes equation describing parabolic relationship of the form L - t(1/2). Here, L is a measure of the diameter of the fabricated micropores during flow time (t). The surface of PMS is smooth due to fluid surface tension at fluid-air interface. We demonstrate fabrication of PMS using curable polydimethylsiloxane (PDMS). The parabolic shape of micropores was a result of interplay between horizontal and vertical fluid movements due to capillary, viscoelastic, and gravitational forces. We also demonstrate fabrication of asymmetric "off-centered PMS" and an array of PMS membranes using this simple fabrication technique. PMS containing membranes with nanoscale dimensions are also possible by controlling the experimental conditions. The present method provides a simple, easy to adopt, and energy efficient way for fabricating non-linear parabolic shape pores at microscale. The prepared parabolic membranes may find applications in many areas including separation, parabolic optics, micro-nozzles / -valves / -pumps, and microfluidic and microelectronic delivery systems.
Directory of Open Access Journals (Sweden)
Gurbuz Ferit
2016-01-01
Full Text Available In this paper, the author introduces parabolic generalized local Morrey spaces and gets the boundedness of a large class of parabolic rough operators on them. The author also establishes the parabolic local Campanato space estimates for their commutators on parabolic generalized local Morrey spaces. As its special cases, the corresponding results of parabolic sublinear operators with rough kernel and their commutators can be deduced, respectively. At last, parabolic Marcinkiewicz operator which satisfies the conditions of these theorems can be considered as an example.
48 CFR 1604.7201 - FEHB Program Large Provider Agreements.
2010-10-01
... methodology the carrier used to compute the provider's profit; and, (v) Describe the provider risk provisions... term ends. (c) Large Provider Agreements based on cost analysis are subject to the provisions of FAR 52.215-2, “Audit and Records-Negotiation.” (d) Large Provider Agreements based on price analysis are...
Self-accelerating parabolic cylinder waves in 1-D
Energy Technology Data Exchange (ETDEWEB)
Yuce, C., E-mail: cyuce@anadolu.edu.tr
2016-11-25
Highlights: • We find a new class of self-accelerating waves. • We show that parabolic cylinder waves self-accelerates in a parabolic potential. • We discuss that truncated parabolic cylinder waves propagates large distance without almost being non-diffracted in free space. - Abstract: We introduce a new self-accelerating wave packet solution of the Schrodinger equation in one dimension. We obtain an exact analytical parabolic cylinder wave for the inverted harmonic potential. We show that truncated parabolic cylinder waves exhibits their accelerating feature.
DEFF Research Database (Denmark)
Lomonaco, Luna; Petersen, Carsten Lunde; Shen, Weixiao
2017-01-01
We prove that any C1+BV degree d ≥ 2 circle covering h having all periodic orbits weakly expanding, is conjugate by a C1+BV diffeomorphism to a metrically expanding map. We use this to connect the space of parabolic external maps (coming from the theory of parabolic-like maps) to metrically...
Studies with Parabolic Parabolic Linear Parabolic (PPLP) momentum function in the LHC
Solfaroli Camillocci, Matteo; Timko, Helga; Wenninger, Jorg; CERN. Geneva. ATS Department
2018-01-01
Measurements performed with a Parabolic Parabolic Linear Parabolic (PPLP) momentum function in the LHC. Three attempts have been performed with a pilot bunch and one with nominal bunch (1.1x1011 p/bunch).
Manufacturing parabolic mirrors
CERN PhotoLab
1975-01-01
The photo shows the construction of a vertical centrifuge mounted on an air cushion, with a precision of 1/10000 during rotation, used for the manufacture of very high=precision parabolic mirrors. (See Annual Report 1974.)
Partial differential equations of parabolic type
Friedman, Avner
2008-01-01
This accessible and self-contained treatment provides even readers previously unacquainted with parabolic and elliptic equations with sufficient background to understand research literature. Author Avner Friedman - Director of the Mathematical Biosciences Institute at The Ohio State University - offers a systematic and thorough approach that begins with the main facts of the general theory of second order linear parabolic equations. Subsequent chapters explore asymptotic behavior of solutions, semi-linear equations and free boundary problems, and the extension of results concerning fundamenta
Directory of Open Access Journals (Sweden)
A. K. Alibekov
2015-01-01
Full Text Available The dependence of the apparent location of the hydraulic parameters of parabolic channels in earthen channel and volume of dredging required in their design and construction, on the basis of conditions to ensure the stability of the slope at the maximum water flow rate.
Administrative and clinical denials by a large dental insurance provider
Directory of Open Access Journals (Sweden)
Geraldo Elias MIRANDA
2015-01-01
Full Text Available The objective of this study was to assess the prevalence and the type of claim denials (administrative, clinical or both made by a large dental insurance plan. This was a cross-sectional, observational study, which retrospectively collected data from the claims and denial reports of a dental insurance company. The sample consisted of the payment claims submitted by network dentists, based on their procedure reports, reviewed in the third trimester of 2012. The denials were classified and grouped into ‘administrative’, ‘clinical’ or ‘both’. The data were tabulated and submitted to uni- and bivariate analyses. The confidence intervals were 95% and the level of significance was set at 5%. The overall frequency of denials was 8.2% of the total number of procedures performed. The frequency of administrative denials was 72.88%, whereas that of technical denials was 25.95% and that of both, 1.17% (p < 0.05. It was concluded that the overall prevalence of denials in the studied sample was low. Administrative denials were the most prevalent. This type of denial could be reduced if all dental insurance providers had unified clinical and administrative protocols, and if dentists submitted all of the required documentation in accordance with these protocols.
Directory of Open Access Journals (Sweden)
Cabezón D.
2014-01-01
Full Text Available Wake effect represents one of the main sources of energy loss and uncertainty when designing offshore wind farms. Traditionally analytical models have been used to optimize and estimate power deficits. However these models have shown to underestimate wake effect and consequently overestimate output power [1, 2]. This means that analytical models can be very helpful at optimizing preliminary layouts but not as accurate as needed for an ultimate fine design. Different techniques can be found in the literature to study wind turbine wakes that include simplified kinematic models and more advanced field models, that solve flow equations with different turbulence closure schemes. See the review papers of Crespo et al. [3], Vermeer et al. [4], and Sanderse et al. [5]. Purely elliptic Computational Fluid Dynamics (CFD models based on the actuator disk technique have been developed during the last years [6–8]. They consider wind turbine rotor as a disk where a distribution of axial forces act over the incoming air. It is a fair approach but it can still be computationally expensive for big wind farms in an operative mode. With this technique still active, an alternative approach inspired on the parabolic wake models [9, 10] is proposed. Wind turbine rotors continue to be represented as actuator disks but now the domain is split into subdomains containing one or more wind turbines. The output of each subdomain is mapped onto the input boundary of the next one until the end of the domain is reached, getting a considerable decrease on computational time, by a factor of order 10. As the model is based on the open source CFD solver OpenFOAM, it can be parallelized to speed-up convergence. The near wake is calculated so no initial wind speed deficit profiles have to be supposed as in totally parabolic models and alternative turbulence models, such as the anisotropic Reynolds Stress Model (RSM can be used. Traditional problems of elliptic models related to
Gradient remediability in linear distributed parabolic systems ...
African Journals Online (AJOL)
The aim of this paper is the introduction of a new concept that concerned the analysis of a large class of distributed parabolic systems. It is the general concept of gradient remediability. More precisely, we study with respect to the gradient observation, the existence of an input operator (gradient efficient actuators) ensuring ...
Session: Parabolic Troughs (Presentation)
Energy Technology Data Exchange (ETDEWEB)
Kutscher, C.
2008-04-01
The project description is R and D activities at NREL and Sandia aimed at lowering the delivered energy cost of parabolic trough collector systems and FOA awards to support industry in trought development. The primary objectives are: (1) support development of near-term parabolic trought technology for central station power generation; (2) support development of next-generation trought fields; and (3) support expansion of US trough industry. The major FY08 activities were: (1) improving reflector optics; (2) reducing receiver heat loss (including improved receiver coating and mitigating hydrogen accumulation); (3) measuring collector optical efficiency; (4) optimizing plant performance and reducing cost; (5) reducing plant water consumption; and (6) directly supporting industry needs, including FOA support.
48 CFR 1652.204-74 - Large provider agreements.
2010-10-01
... insert the following clause in all FEHB Program contracts based on cost analysis (experience-rated...; (iv) Describe the methodology the carrier used to compute the provider's profit; and, (v) Describe provider risk provisions. (3) The Contracting officer may request from the carrier any additional...
Li, Zhong-xiao; Li, Zhen-chun
2017-08-01
Adaptive multiple subtraction is an important step for successfully conducting surface-related multiple elimination in marine seismic exploration. 2D adaptive multiple subtraction conducted in the parabolic Radon domain has been proposed to better separate primaries and multiples than 2D adaptive multiple subtraction conducted in the time-offset domain. Additionally, the parabolic Radon domain hybrid demultiple method combining parabolic Radon filtering and parabolic Radon domain 2D adaptive multiple subtraction can better remove multiples than the cascaded demultiple method using time-offset domain 2D adaptive multiple subtraction and the parabolic Radon transform method sequentially. To solve the matching filter in the optimization problem with L1 norm minimization constraint of primaries, traditional parabolic Radon domain 2D adaptive multiple subtraction uses the iterative reweighted least squares (IRLS) algorithm, which is computationally expensive for solving a weighted LS inversion in each iteration. In this paper we introduce the fast iterative shrinkage thresholding algorithm (FISTA) as a faster alternative to the IRLS algorithm for parabolic Radon domain 2D adaptive multiple subtraction. FISTA uses the shrinkage-thresholding operator to promote the sparsity of estimated primaries and solves the 2D matching filter with iterative steps. FISTA based parabolic Radon domain 2D adaptive multiple subtraction reduces the computation time effectively while achieving similar accuracy compared with IRLS based parabolic Radon domain 2D adaptive multiple subtraction. Additionally, the provided examples show that FISTA based parabolic Radon domain 2D adaptive multiple subtraction can better separate primaries and multiples than FISTA based time-offset domain 2D adaptive multiple subtraction. Furthermore, we introduce FISTA based parabolic Radon domain 2D adaptive multiple subtraction into the parabolic Radon domain hybrid demultiple method to improve its computation
Parabolic Fractional Maximal Operator in Modified Parabolic Morrey Spaces
Directory of Open Access Journals (Sweden)
Vagif S. Guliyev
2012-01-01
Full Text Available We prove that the parabolic fractional maximal operator MαP, 0≤α<γ, is bounded from the modified parabolic Morrey space M̃1,λ,P(ℝn to the weak modified parabolic Morrey space WM̃q,λ,P(ℝn if and only if α/γ≤1-1/q≤α/(γ-λ and from M̃p,λ,P(ℝn to M̃q,λ,P(ℝn if and only if α/γ≤1/p-1/q≤α/(γ-λ. Here γ=trP is the homogeneous dimension on ℝn. In the limiting case (γ-λ/α≤p≤γ/α we prove that the operator MαP is bounded from M̃p,λ,P(ℝn to L∞(ℝn. As an application, we prove the boundedness of MαP from the parabolic Besov-modified Morrey spaces BM̃pθ,λs(ℝn to BM̃qθ,λs(ℝn. As other applications, we establish the boundedness of some Schrödinger-ype operators on modified parabolic Morrey spaces related to certain nonnegative potentials belonging to the reverse Hölder class.
Parabolic cyclinder functions : examples of error bounds for asymptotic expansions
R. Vidunas; N.M. Temme (Nico)
2002-01-01
textabstractSeveral asymptotic expansions of parabolic cylinder functions are discussedand error bounds for remainders in the expansions are presented. Inparticular Poincaré-type expansions for large values of the argument$z$ and uniform expansions for large values of the parameter areconsidered.
Temperature Performance Evaluation of Parabolic Dishes Covered ...
African Journals Online (AJOL)
Aweda
Nigerian Journal of Basic and Applied Science (June, 2016), 24(1): 90-97 ... gives more explanation of solar rays reaching the .... (1991) for the evaluation of solar parabolic dish cookers. Table 1: Parabolic Dish Reflector's Parameters.
Plane and parabolic solar panels
Sales, J. H. O.; Suzuki, A. T.
2009-01-01
We present a plane and parabolic collector that absorbs radiant energy and transforms it in heat. Therefore we have a panel to heat water. We study how to increment this capture of solar beams onto the panel in order to increase its efficiency in heating water.
DEFF Research Database (Denmark)
Tian, Zhiyong; Perers, Bengt; Furbo, Simon
2017-01-01
the district heating network to about 70 °C and then the parabolic trough collectors would heat the preheated water to the required supply temperature of the district heating network. Annual measured and simulated thermal performances of both the parabolic trough collector field and the flat plate collector...... in large solar heating plants for a district heating network, a hybrid solar collector field with 5960 m2 flat plate collectors and 4039 m2 parabolic trough collectors in series was constructed in Taars, Denmark. The design principle is that the flat plate collectors preheat the return water from...... field are presented in this paper. The thermal performance of both collector fields with weather data of a Design Reference Year was simulated to have a whole understanding of the application of both collectors under Danish climate conditions as well. These results not only can provide a design basis...
High regularity of the solution of a nonlinear parabolic boundary-value problem
Directory of Open Access Journals (Sweden)
Luminita Barbu
2002-05-01
Full Text Available The aim of this paper is to report some results concerning high regularity of the solution of a nonlinear parabolic problem with a linear parabolic differential equation in one spatial dimension and nonlinear boundary conditions. We show that any regularity can be reached provided that appropriate smoothness of the data and compatibility assumptions are required.
Federal technology alert. Parabolic-trough solar water heating
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-04-01
Parabolic-trough solar water heating is a well-proven renewable energy technology with considerable potential for application at Federal facilities. For the US, parabolic-trough water-heating systems are most cost effective in the Southwest where direct solar radiation is high. Jails, hospitals, barracks, and other facilities that consistently use large volumes of hot water are particularly good candidates, as are facilities with central plants for district heating. As with any renewable energy or energy efficiency technology requiring significant initial capital investment, the primary condition that will make a parabolic-trough system economically viable is if it is replacing expensive conventional water heating. In combination with absorption cooling systems, parabolic-trough collectors can also be used for air-conditioning. Industrial Solar Technology (IST) of Golden, Colorado, is the sole current manufacturer of parabolic-trough solar water heating systems. IST has an Indefinite Delivery/Indefinite Quantity (IDIQ) contract with the Federal Energy Management Program (FEMP) of the US Department of Energy (DOE) to finance and install parabolic-trough solar water heating on an Energy Savings Performance Contract (ESPC) basis for any Federal facility that requests it and for which it proves viable. For an ESPC project, the facility does not pay for design, capital equipment, or installation. Instead, it pays only for guaranteed energy savings. Preparing and implementing delivery or task orders against the IDIQ is much simpler than the standard procurement process. This Federal Technology Alert (FTA) of the New Technology Demonstration Program is one of a series of guides to renewable energy and new energy-efficient technologies.
Asymptotic behavior for cross coupled parabolic equations
Directory of Open Access Journals (Sweden)
Yingzhen XUE
2017-04-01
Full Text Available In order to better describe the heat transfer process of three kinds of mixed substances, namely the reaction of the reactants in the three chemical reactions, a class of three variable cross coupling with non parabolic equations of the whole existence of local source and non local boundary flow and the finite time blow up problem with breaking method for the solution of the first commonly used feature value structure are studied. The structure of the equations of the upper and lower solutions by using the method of ordinary differential equation reference is broken, with comparison theorem, the proof shows that obtained by local source power function and exponential function of parabolic equations is broken, with the sufficient conditions for global existence of clegerate purubolic equations solutions cross coupled by local source power function and non local sources exponential function are proved, as soon as the solution of blowing up in finite time degradation of non local sources of cross coupling, providing better support for the theory of heat transfer and chemical reaction problem.
Numerical Solution of Parabolic Equations
DEFF Research Database (Denmark)
Østerby, Ole
These lecture notes are designed for a one-semester course on finite-difference methods for parabolic equations. These equations which traditionally are used for describing diffusion and heat-conduction problems in Geology, Physics, and Chemistry have recently found applications in Finance Theory...... approximations which depend on a step size, such as numerical integration and solution of ordinary and partial differential equations. An integral part of the error estimation is the estimation of the order of the method and can thus satisfy the inquisitive mind: Is the order what we expect it to be from theopry...
The dynamics of parabolic flight: Flight characteristics and passenger percepts
Karmali, Faisal; Shelhamer, Mark
2008-09-01
Flying a parabolic trajectory in an aircraft is one of the few ways to create freefall on Earth, which is important for astronaut training and scientific research. Here we review the physics underlying parabolic flight, explain the resulting flight dynamics, and describe several counterintuitive findings, which we corroborate using experimental data. Typically, the aircraft flies parabolic arcs that produce approximately 25 s of freefall (0 g) followed by 40 s of enhanced force (1.8 g), repeated 30-60 times. Although passengers perceive gravity to be zero, in actuality acceleration, and not gravity, has changed, and thus we caution against the terms "microgravity" and "zero gravity." Despite the aircraft trajectory including large (45°) pitch-up and pitch-down attitudes, the occupants experience a net force perpendicular to the floor of the aircraft. This is because the aircraft generates appropriate lift and thrust to produce the desired vertical and longitudinal accelerations, respectively, although we measured moderate (0.2 g) aft-ward accelerations during certain parts of these trajectories. Aircraft pitch rotation (average 3°/s) is barely detectable by the vestibular system, but could influence some physics experiments. Investigators should consider such details in the planning, analysis, and interpretation of parabolic-flight experiments.
IR Spectrometer Using 90-degree Off-axis Parabolic Mirrors
Energy Technology Data Exchange (ETDEWEB)
Robert M. Malone, Richard, G. Hacking, Ian J. McKenna, and Daniel H. Dolan
2008-09-02
A gated spectrometer has been designed for real-time, pulsed infrared (IR) studies at the National Synchrotron Light ource at the Brookhaven National Laboratory. A pair of 90-degree, off-axis parabolic mirrors are used to relay the light from an entrance slit to an output IR recording camera. With an initial wavelength range of 1500–4500 nm required, gratings could not be used in the spectrometer because grating orders would overlap. A magnesium oxide prism, placed between these parabolic mirrors, serves as the dispersion element. The spectrometer is doubly telecentric. With proper choice of the air spacing between the prism and the second parabolic mirror, any spectral region of interest within the InSb camera array’s sensitivity region can be recorded. The wavelengths leaving the second parabolic mirror are collimated, thereby relaxing the camera positioning tolerance. To set up the instrument, two different wavelength (visible) lasers are introduced at the entrance slit and made collinear with the optical axis via flip mirrors. After dispersion by the prism, these two laser beams are directed to tick marks located on the outside housing of the gated IR camera. This provides first-order wavelength calibration for the instrument. Light that is reflected off the front prism face is coupled into a high-speed detector to verify steady radiance during the gated spectral imaging. Alignment features include tick marks on the prism and parabolic mirrors. This instrument was designed to complement singlepoint pyrometry, which provides continuous time histories of a small collection of spots from shock-heated targets.
Parabolic dish photovoltaic concentrator development
Beninga, K.; Davenport, R.; Featherby, M.; Sandubrae, J.; Walcott, K.
1991-05-01
Science Applications International Corporation (SAIC) and Tactical Fabs, Inc. (TFI) have fabricated a prototype parabolic dish photovoltaic (PV) concentrator system to demonstrate the functionality of this approach. A 1.5 m diameter parabolic dish was fabricated of a polyester/fiberglass composite, with a silvered polymer reflective surface. An innovative receiver cooling system used outward radial flow of cooling water in a narrow passage. This configuration matches the heat transfer capability of the cooling system to the flux profile on the PV receiver, minimizing temperature variations across the receiver. The photovoltaic cells used in the system were a new, TFI-proprietary design. Interleaved contacts form a bi-polar, rear-contact cell configuration. Because the electrical contacts are made on the rear of the cells, cells can be close-packed to form receiver arrays of arbitrary shape and size. Optical testing of the dish concentrator was performed by SAIC, SERI, and Sandia National Labs. The dish concentrator, designed for solar thermal applications, had a tight focal spot but exhibited flux non-uniformities away from the focal plane. Thermal testing of the receiver cooling system was performed with excellent success. Single PV cells, 4-cell blocks, and 144-cell receiver modules were built and tested. The cells successfully demonstrated the TFI design concept, but due to cell processing problems their efficiency was very low. Sources of the processing problems were identified and solutions were proposed, but funding limitations precluded further cell production. Operation of the complete PV dish system was conducted, and the functionality of the system was demonstrated. However, low cell efficiencies and receiver plane flux non-uniformities caused the system performance to be very low. These problems are not generic to the concept, and solutions to them proposed.
Greene, Jessica; Hibbard, Judith H; Overton, Valerie
2015-04-01
This study examined the impact of Fairview Health Services' primary care provider compensation model, in which 40 percent of compensation was based on clinic-level quality outcomes. Fairview Health Services is a Pioneer accountable care organization in Minnesota. Using publicly reported performance data from 2010 and 2012, we found that Fairview's improvement in quality metrics was not greater than the improvement in other comparable Minnesota medical groups. An analysis of Fairview's administrative data found that the largest predictor of improvement over the first two years of the compensation model was primary care providers' baseline quality performance. Providers whose baseline performance was in the lowest tertile improved three times more, on average, across the three quality metrics studied than those in the middle tertile, and almost six times more than those in the top tertile. As a result, there was a narrowing of variation in performance across all primary care providers at Fairview and a narrowing of the gap in quality between providers who treated the highest-income patient panels and those who treated the lowest-income panels. The large quality incentive fell short of its overall quality improvement aim. However, the results suggest that payment reform may help narrow variation in primary care provider performance, which can translate into narrowing socioeconomic disparities. Project HOPE—The People-to-People Health Foundation, Inc.
International Workshop on Elliptic and Parabolic Equations
Schrohe, Elmar; Seiler, Jörg; Walker, Christoph
2015-01-01
This volume covers the latest research on elliptic and parabolic equations and originates from the international Workshop on Elliptic and Parabolic Equations, held September 10-12, 2013 at the Leibniz Universität Hannover. It represents a collection of refereed research papers and survey articles written by eminent scientist on advances in different fields of elliptic and parabolic partial differential equations, including singular Riemannian manifolds, spectral analysis on manifolds, nonlinear dispersive equations, Brownian motion and kernel estimates, Euler equations, porous medium type equations, pseudodifferential calculus, free boundary problems, and bifurcation analysis.
Let's play with the parabolic antenna!
Ishihara, Yuko
2006-03-01
By collaborating with the Nobeyama Radio Observatory, we developed a teaching material where one can play and learn how a parabolic antenna collects radio waves. The antenna is now on exhibit at Koriyama City Fureai Science Center. Superballs help the user to visualize the mechanism of a parabolic antenna. The antenna used in the exhibit was originally a part of a radio telescope. More than a year has passed since the development and the exhibition. We report about the applied use of the antenna inside and outside our science center and about parabolic antennas in other museums and observatories.
A compact representation of drawing movements with sequences of parabolic primitives.
Polyakov, Felix; Drori, Rotem; Ben-Shaul, Yoram; Abeles, Moshe; Flash, Tamar
2009-07-01
Some studies suggest that complex arm movements in humans and monkeys may optimize several objective functions, while others claim that arm movements satisfy geometric constraints and are composed of elementary components. However, the ability to unify different constraints has remained an open question. The criterion for a maximally smooth (minimizing jerk) motion is satisfied for parabolic trajectories having constant equi-affine speed, which thus comply with the geometric constraint known as the two-thirds power law. Here we empirically test the hypothesis that parabolic segments provide a compact representation of spontaneous drawing movements. Monkey scribblings performed during a period of practice were recorded. Practiced hand paths could be approximated well by relatively long parabolic segments. Following practice, the orientations and spatial locations of the fitted parabolic segments could be drawn from only 2-4 clusters, and there was less discrepancy between the fitted parabolic segments and the executed paths. This enabled us to show that well-practiced spontaneous scribbling movements can be represented as sequences ("words") of a small number of elementary parabolic primitives ("letters"). A movement primitive can be defined as a movement entity that cannot be intentionally stopped before its completion. We found that in a well-trained monkey a movement was usually decelerated after receiving a reward, but it stopped only after the completion of a sequence composed of several parabolic segments. Piece-wise parabolic segments can be generated by applying affine geometric transformations to a single parabolic template. Thus, complex movements might be constructed by applying sequences of suitable geometric transformations to a few templates. Our findings therefore suggest that the motor system aims at achieving more parsimonious internal representations through practice, that parabolas serve as geometric primitives and that non-Euclidean variables are
A Modified Wide Angle Parabolic Wave Equation
St. Mary, Donald F.; Lee, Ding; Botseas, George
1987-08-01
We demonstrate the implicit finite difference discretization of a higher order parabolic-like partial differential equation approximating the reduced wave equation in the far field and show that the discretization is unconditionally stable. We discuss a method of associating an angle of dispersion with parabolic approximations, present an example which can be used to compare methods on the basis of dispersion angle, and make comparisons among well-known methods and the new method.
Development and testing of Parabolic Dish Concentrator No. 1
Dennison, E. W.; Thostesen, T. O.
1984-12-01
Parabolic Dish Concentrator No. 1 (PDC-1) is a 12-m-diameter prototype concentrator with low life-cycle costs for use with thermal-to-electric energy conversion devices. The concentrator assembly features panels made of a resin transfer molded balsa core/fiberglass sandwich with plastic reflective film as the reflective surface and a ribbed framework to hold the panels in place. The concentrator assembly tracks in azimuth and elevation on a base frame riding on a circular track. It is shown that the panels do not exhibit the proper parabolic contour. However, thermal gradients were discovered in the panels with daily temperature changes. The PDC-1 has sufficient optical quality to operate satisfactorily in a dish-electric system. The PDC-1 development provides the impetus for creating innovative optical testing methods and valuable information for use in designing and fabricating concentrators of future dish-electric systems.
Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint
Energy Technology Data Exchange (ETDEWEB)
Stynes, J. K.; Ihas, B.
2012-04-01
As we pursue efforts to lower the capital and installation costs of parabolic trough solar collectors, it is essential to maintain high optical performance. While there are many optical tools available to measure the reflector slope errors of parabolic trough solar collectors, there are few tools to measure the absorber alignment. A new method is presented here to measure the absorber alignment in two dimensions to within 0.5 cm. The absorber alignment is measured using a digital camera and four photogrammetric targets. Physical contact with the receiver absorber or glass is not necessary. The alignment of the absorber is measured along its full length so that sagging of the absorber can be quantified with this technique. The resulting absorber alignment measurement provides critical information required to accurately determine the intercept factor of a collector.
Early Peritonitis in a Large Peritoneal Dialysis Provider System in Colombia.
Vargas, Edgar; Blake, Peter G; Sanabria, Mauricio; Bunch, Alfonso; López, Patricia; Vesga, Jasmín; Buitrago, Alberto; Astudillo, Kindar; Devia, Martha; Sánchez, Ricardo
♦ BACKGROUND: Peritonitis is the most important complication of peritoneal dialysis (PD), and early peritonitis rate is predictive of the subsequent course on PD. Our aim was to calculate the early peritonitis rate and to identify characteristics and predisposing factors in a large nationwide PD provider network in Colombia. ♦ METHODS: This was a historical observational cohort study of all adult patients starting PD between January 1, 2012, and December 31, 2013, in 49 renal facilities in the Renal Therapy Services in Colombia. We studied the peritonitis rate in the first 90 days of treatment, its causative micro-organisms, its predictors and its variation with time on PD and between individual facilities. ♦ RESULTS: A total of 3,525 patients initiated PD, with 176 episodes of peritonitis during 752 patient-years of follow-up for a rate of 0.23 episodes per patient year equivalent to 1 every 52 months. In 41 of 49 units, the rate was better than 1 per 33 months, and in 45, it was better than 1 per 24 months. Peritonitis rates did not differ with age, ethnicity, socioeconomic status, or PD modality. We identified high incidence risk periods at 2 to 5 weeks after initiation of PD and again at 10 to 12 weeks. ♦ CONCLUSION: An excellent peritonitis rate was achieved across a large nationwide network. This occurred in the context of high nationwide PD utilization and despite high rates of socioeconomic deprivation. We propose that a key factor in achieving this was a standardized approach to management of patients. Copyright © 2017 International Society for Peritoneal Dialysis.
Gas Turbine/Solar Parabolic Trough Hybrid Designs: Preprint
Energy Technology Data Exchange (ETDEWEB)
Turchi, C. S.; Ma, Z.; Erbes, M.
2011-03-01
A strength of parabolic trough concentrating solar power (CSP) plants is the ability to provide reliable power by incorporating either thermal energy storage or backup heat from fossil fuels. Yet these benefits have not been fully realized because thermal energy storage remains expensive at trough operating temperatures and gas usage in CSP plants is less efficient than in dedicated combined cycle plants. For example, while a modern combined cycle plant can achieve an overall efficiency in excess of 55%; auxiliary heaters in a parabolic trough plant convert gas to electricity at below 40%. Thus, one can argue the more effective use of natural gas is in a combined cycle plant, not as backup to a CSP plant. Integrated solar combined cycle (ISCC) systems avoid this pitfall by injecting solar steam into the fossil power cycle; however, these designs are limited to about 10% total solar enhancement. Without reliable, cost-effective energy storage or backup power, renewable sources will struggle to achieve a high penetration in the electric grid. This paper describes a novel gas turbine / parabolic trough hybrid design that combines solar contribution of 57% and higher with gas heat rates that rival that for combined cycle natural gas plants. The design integrates proven solar and fossil technologies, thereby offering high reliability and low financial risk while promoting deployment of solar thermal power.
Explicit Nonlinear Finite Element Geometric Analysis of Parabolic Leaf Springs under Various Loads
Directory of Open Access Journals (Sweden)
Y. S. Kong
2013-01-01
Full Text Available This study describes the effects of bounce, brake, and roll behavior of a bus toward its leaf spring suspension systems. Parabolic leaf springs are designed based on vertical deflection and stress; however, loads are practically derived from various modes especially under harsh road drives or emergency braking. Parabolic leaf springs must sustain these loads without failing to ensure bus and passenger safety. In this study, the explicit nonlinear dynamic finite element (FE method is implemented because of the complexity of experimental testing A series of load cases; namely, vertical push, wind-up, and suspension roll are introduced for the simulations. The vertical stiffness of the parabolic leaf springs is related to the vehicle load-carrying capability, whereas the wind-up stiffness is associated with vehicle braking. The roll stiffness of the parabolic leaf springs is correlated with the vehicle roll stability. To obtain a better bus performance, two new parabolic leaf spring designs are proposed and simulated. The stress level during the loadings is observed and compared with its design limit. Results indicate that the newly designed high vertical stiffness parabolic spring provides the bus a greater roll stability and a lower stress value compared with the original design. Bus safety and stability is promoted, as well as the load carrying capability.
Optimisation and characterisation of parabolic membrane mirrors
Hellmuth, T.; Khrennikov, K.; Kronast, W.; Huster, R.; Mescheder, U.
2008-04-01
MOEMS-based thin silicon membrane mirrors with a useable diameter of 5mm and fast (up to 1kHz) tunable focal length (80 mm to 1m) have been realized. A ring shaped counter electrode is used to achieve a parabolic membrane deformation by electrostatic forces. A circular kerf at the outer perimeter of the membrane provides a soft suspension to the rim and thus reduces the needed driving voltage. FEM has been used for optimisation of the design, especially of the soft suspension, which is realized by a controlled thinning of the outer rim of the Si-membrane. A critical issue for demanding applications is the membrane distortion induced by material stress and the fabrication process. Membrane residual stress reduction has been obtained by using SOI-technology (c-silicon) and by optimisation of the Al deposition process (Al-coated Si-membrane). For dynamic tests of the optical mirror properties a stroboscopic interferometer has been realized. A pulsed laser diode with a pulse duration of 10μs is used as a light source which is synchronized with the modulated electrical field driving the membrane mirror. The interference pattern is recorded with a CCD and evaluated with conventional phaseshift techniques. The geometry is similar to a Mach-Zehnder interferometer. The reference path length can be varied with a piezoceramic to induce the phase shift.
In-Center Nutrition Practices of Clinics within a Large Hemodialysis Provider in the United States.
Benner, Debbie; Burgess, Mary; Stasios, Maria; Brosch, Becky; Wilund, Ken; Shen, Sa; Kistler, Brandon
2016-05-06
Eating during hemodialysis treatment remains a controversial topic. It is perceived that more restrictive practices in the United States contribute to poorer nutritional status and elevated mortality compared with some other parts of the world. However, in-center food practices in the United States have not been previously described. In 2011, we conducted a survey of clinic practices and clinician (dietitian, facility administrator, and medical director) opinions related to in-center food consumption within a large dialysis organization. After the initial survey, we provided clinicians with educational materials about eating during treatment. In 2014, we performed a follow-up survey. Differences in practices and opinions were analyzed using chi-squared tests and logistic regression. In 2011, 343 of 1199 clinics (28.6%) did not allow eating during treatment, 222 clinics (18.2%) did not allow drinking during treatment, and 19 clinics (1.6%) did not allow eating at the facility before or after treatment. In 2014, the proportion of clinics that did not allow eating during treatment had declined to 22.6% (321 of 1422 clinics), a significant shift in practice (Pnutritional status. Among clinicians, a higher percentage encouraged eating during treatment (53.1% versus 37.4%; P<0.05), and facility administrators and medical directors were less concerned about the seven reasons commonly cited for restricting eating during treatment in 2014 compared with 2011 (P<0.05 for all). We found that 28.6% and 22.6% of hemodialysis clinics within the United States restricted eating during treatment in 2011 and 2014, respectively, a rate more than double that found in an international cohort on which we previously published. However, practices and clinician opinions are shifting toward allowing patients to eat. Additional research is warranted to understand the effect that these practices have on patient outcomes and outline best practices. Copyright © 2016 by the American Society of
Culture rather than genes provides greater scope for the evolution of large-scale human prosociality
Bell, Adrian V; Peter J Richerson; McElreath, Richard
2009-01-01
Whether competition among large groups played an important role in human social evolution is dependent on how variation, whether cultural or genetic, is maintained between groups. Comparisons between genetic and cultural differentiation between neighboring groups show how natural selection on large groups is more plausible on cultural rather than genetic variation.
Reduction of effective terahertz focal spot size by means of nested concentric parabolic reflectors
Neumann, V.A.; Laurita, N.J.; Pan, LiDong; Armitage, N.P.
2016-01-01
An ongoing limitation of terahertz spectroscopy is that the technique is generally limited to the study of relatively large samples of order 4 mm across due to the generally large size of the focal beam spot. We present a nested concentric parabolic reflector design which can reduce the terahertz
Modeling, Simulation and Performance Evaluation of Parabolic Trough
African Journals Online (AJOL)
Mekuannint
MODELING, SIMULATION AND PERFORMANCE EVALUATION OF. PARABOLIC TROUGH. SOLAR COLLECTOR POWER GENERATION SYSTEM. Mekuannint Mesfin and Abebayehu Assefa. Department of Mechanical Engineering. Addis Ababa University. ABSTRACT. Model of a parabolic trough power plant, taking.
A Parabolic Model Presentation of Solar Radiation Data at a ...
African Journals Online (AJOL)
Ife, Nigeria has been analysed and simple parabolic models established for predicting them. The models appear in the form of parabolic equations with three parameters. The necessary physical interpretations of the model parameters, their ...
Providing the Public with Online Access to Large Bibliographic Data Bases.
Firschein, Oscar; Summit, Roger K.
DIALOG, an interactive, computer-based information retrieval language, consists of a series of computer programs designed to make use of direct access memory devices in order to provide the user with a rapid means of identifying records within a specific memory bank. Using the system, a library user can be provided access to sixteen distinct and…
Energy Technology Data Exchange (ETDEWEB)
Kearney, D.
2011-05-01
Prior to commercial operation, large solar systems in utility-size power plants need to pass a performance acceptance test conducted by the engineering, procurement, and construction (EPC) contractor or owners. In lieu of the present absence of ASME or other international test codes developed for this purpose, the National Renewable Energy Laboratory has undertaken the development of interim guidelines to provide recommendations for test procedures that can yield results of a high level of accuracy consistent with good engineering knowledge and practice. The Guidelines contained here are specifically written for parabolic trough collector systems with a heat-transport system using a high-temperature synthetic oil, but the basic principles are relevant to other CSP systems.
Temperature Performance Evaluation of Parabolic Dishes Covered ...
African Journals Online (AJOL)
Aweda
ABSTRACT: Solar radiation reaching the earth is considered to be affected by some parameters like diffusion. This radiation is reflected or scattered by air molecules, cloud and aerosols (dust). Parabolic dishes made of different materials (glass, foil and painted surface) were used to concentrate energy on a.
Modeling, simulation and performance evaluation of parabolic ...
African Journals Online (AJOL)
Model of a parabolic trough power plant, taking into consideration the different losses associated with collection of the solar irradiance and thermal losses is presented. MATLAB software is employed to model the power plant at reference state points. The code is then used to find the different reference values which are ...
Use of adaptive optimal control to provide energy conservation in large buildings
Energy Technology Data Exchange (ETDEWEB)
Farris, D.R.; Miller, D.E.
1979-01-01
The use of an adaptive linear regulator approach for controlling heating, ventilating, and air-conditioning (HVAC) systems in large buildings is discussed. The control manifestations of this approach are compared with those found in conventional applications. The salient features of the approach are discussed, and simulation results are presented. Implementation is discussed, and economic estimates for commercial use of this approach are also presented.
Computer aided FEA simulation of EN45A parabolic leaf spring
Directory of Open Access Journals (Sweden)
Krishan Kumar
2013-04-01
Full Text Available This paper describes computer aided finite element analysis of parabolic leaf spring. The present work is an improvement in design of EN45A parabolic leaf spring used by a light commercial automotive vehicle. Development of a leaf spring is a long process which requires lots of test to validate the design and manufacturing variables. A three-layer parabolic leaf spring of EN45A has been taken for this work. The thickness of leaves varies from center to the outer side following a parabolic pattern. These leaf springs are designed to become lighter, but also provide a much improved ride to the vehicle through a reduction on interleaf friction. The CAD modeling of parabolic leaf spring has been done in CATIA V5 and for analysis the model is imported in ANSYS-11 workbench. The finite element analysis (FEA of the leaf spring has been carried out by initially discretizing the model into finite number of elements and nodes and then applying the necessary boundary conditions. Maximum displacement, directional displacement, equivalent stress and weight of the assembly are the output targets of this analysis for comparison & validation of the work.
On purpose simulation model for molten salt CSP parabolic trough
Caranese, Carlo; Matino, Francesca; Maccari, Augusto
2017-06-01
The utilization of computer codes and simulation software is one of the fundamental aspects for the development of any kind of technology and, in particular, in CSP sector for researchers, energy institutions, EPC and others stakeholders. In that extent, several models for the simulation of CSP plant have been developed with different main objectives (dynamic simulation, productivity analysis, techno economic optimization, etc.), each of which has shown its own validity and suitability. Some of those models have been designed to study several plant configurations taking into account different CSP plant technologies (Parabolic trough, Linear Fresnel, Solar Tower or Dish) and different settings for the heat transfer fluid, the thermal storage systems and for the overall plant operating logic. Due to a lack of direct experience of Molten Salt Parabolic Trough (MSPT) commercial plant operation, most of the simulation tools do not foresee a suitable management of the thermal energy storage logic and of the solar field freeze protection system, but follow standard schemes. ASSALT, Ase Software for SALT csp plants, has been developed to improve MSPT plant's simulations, by exploiting the most correct operational strategies in order to provide more accurate technical and economical results. In particular, ASSALT applies MSPT specific control logics for the electric energy production and delivery strategy as well as the operation modes of the Solar Field in off-normal sunshine condition. With this approach, the estimated plant efficiency is increased and the electricity consumptions required for the plant operation and management is drastically reduced. Here we present a first comparative study on a real case 55 MWe Molten Salt Parabolic Trough CSP plant placed in the Tibetan highlands, using ASSALT and SAM (System Advisor Model), which is a commercially available simulation tool.
Parabolic dish collectors - A solar option
Truscello, V. C.
1981-01-01
A description is given of several parabolic-dish high temperature solar thermal systems currently undergoing performance trials. A single parabolic dish has the potential for generating 20 to 30 kW of electricity with fluid temperatures from 300 to 1650 C. Each dish is a complete power-producing unit, and may function either independently or as part of a group of linked modules. The two dish designs under consideration are of 11 and 12 meter diameters, yielding receiver operating temperatures of 925 and 815 C, respectively. The receiver designs described include (1) an organic working fluid (toluene) Rankine cycle engine; (2) a Brayton open cycle unit incorporating a hybrid combustion chamber and nozzle and a shaft-coupled permanent magnet alternator; and (3) a modified Stirling cycle device originally designed for automotive use. Also considered are thermal buffer energy storage and thermochemical transport and storage.
Who dares to join a parabolic flight?
Montag, Christian; Zander, Tina; Schneider, Stefan
2016-12-01
Parabolic flights represent an important tool in space research to investigate zero gravity on airplanes. Research on these flights often target psychological and biological processes in humans to investigate if and how we can adapt to this unique environment. This research is costly, hard to conduct and clearly heavily relies on humans participating in experiments in this (unnatural) situation. The present study investigated N =66 participants and N =66 matched control persons to study if participants in such experimental flights differ in terms of their personality traits from non-parabonauts. The main finding of this study demonstrates that parabonauts score significantly lower on harm avoidance, a trait closely linked to being anxious. As anxious humans differ from non-anxious humans in their biology, the present observations need to be taken into account when aiming at the generalizability of psychobiological research findings conducted in zero gravity on parabolic flights.
Moving interfaces and quasilinear parabolic evolution equations
Prüss, Jan
2016-01-01
In this monograph, the authors develop a comprehensive approach for the mathematical analysis of a wide array of problems involving moving interfaces. It includes an in-depth study of abstract quasilinear parabolic evolution equations, elliptic and parabolic boundary value problems, transmission problems, one- and two-phase Stokes problems, and the equations of incompressible viscous one- and two-phase fluid flows. The theory of maximal regularity, an essential element, is also fully developed. The authors present a modern approach based on powerful tools in classical analysis, functional analysis, and vector-valued harmonic analysis. The theory is applied to problems in two-phase fluid dynamics and phase transitions, one-phase generalized Newtonian fluids, nematic liquid crystal flows, Maxwell-Stefan diffusion, and a variety of geometric evolution equations. The book also includes a discussion of the underlying physical and thermodynamic principles governing the equations of fluid flows and phase transitions...
Surface Plasmon Polariton microscope with Parabolic Reflectors
Drezet, Aurelien; Koller, Daniel; Hohenau, Andreas; Leitner, Alfred; Aussenegg, Franz R.; Krenn, Joachim R.
2010-01-01
We report the realization of a two--dimensional optical microscope for surface plasmons polaritons (SPPs) based on parabolic Bragg mirrors. These mirrors are built from lithographically fabricated gold nanostructures on gold thin films. We show by direct imaging by leakage radiation microscopy that the magnification power of the SPP microscope follows basic predictions of geometrical optics. Spatial resolution down to the value set by the diffraction limit is demonstrated.
Building a parabolic solar concentrator prototype
Energy Technology Data Exchange (ETDEWEB)
Escobar-Romero, J F M; Montiel, S Vazquez y; Granados-AgustIn, F; Rodriguez-Rivera, E; Martinez-Yanez, L [INAOE, Luis Enrique Erro 1, Tonantzintla, Pue., 72840 (Mexico); Cruz-Martinez, V M, E-mail: jfmescobar@yahoo.com [Universidad Tecnologica de la Mixteca, Camino a Acatilma Km 2.5, Huajuapan de Leon, Oax., 69000 (Mexico)
2011-01-01
In order to not further degrade the environment, people have been seeking to replace non-renewable natural resources such as fossil fuels by developing technologies that are based on renewable resources. An example of these technologies is solar energy. In this paper, we show the building and test of a solar parabolic concentrator as a prototype for the production of steam that can be coupled to a turbine to generate electricity or a steam engine in any particular industrial process.
A short proof of increased parabolic regularity
Directory of Open Access Journals (Sweden)
Stephen Pankavich
2015-08-01
Full Text Available We present a short proof of the increased regularity obtained by solutions to uniformly parabolic partial differential equations. Though this setting is fairly introductory, our new method of proof, which uses a priori estimates and an inductive method, can be extended to prove analogous results for problems with time-dependent coefficients, advection-diffusion or reaction diffusion equations, and nonlinear PDEs even when other tools, such as semigroup methods or the use of explicit fundamental solutions, are unavailable.
Similarity and generalized finite-difference solutions of parabolic partial differential equations.
Clausing, A. M.
1971-01-01
Techniques are presented for obtaining generalized finite-difference solutions to partial differential equations of the parabolic type. It is shown that the advantages of similarity in the solution of similar problems are generally not lost if the solution to the original partial differential equations is effected in the physical plane by finite-difference methods. The analysis results in a considerable saving in computational effort in the solution of both similar and nonsimilar problems. Several examples, including both the heat-conduction equation and the boundary-layer equations, are given. The analysis also provides a practical means of estimating the accuracy of finite-difference solutions to parabolic equations.
Energy Technology Data Exchange (ETDEWEB)
Vandewalle, S. [Caltech, Pasadena, CA (United States)
1994-12-31
Time-stepping methods for parabolic partial differential equations are essentially sequential. This prohibits the use of massively parallel computers unless the problem on each time-level is very large. This observation has led to the development of algorithms that operate on more than one time-level simultaneously; that is to say, on grids extending in space and in time. The so-called parabolic multigrid methods solve the time-dependent parabolic PDE as if it were a stationary PDE discretized on a space-time grid. The author has investigated the use of multigrid waveform relaxation, an algorithm developed by Lubich and Ostermann. The algorithm is based on a multigrid acceleration of waveform relaxation, a highly concurrent technique for solving large systems of ordinary differential equations. Another method of this class is the time-parallel multigrid method. This method was developed by Hackbusch and was recently subject of further study by Horton. It extends the elliptic multigrid idea to the set of equations that is derived by discretizing a parabolic problem in space and in time.
Performance evaluation of low cost domestic parabolic solar cooker
Energy Technology Data Exchange (ETDEWEB)
Tandale, M.S. [Dr. Babasaheb Ambedkar Technological Univ., Lonere (India). Dept. of Mechanical Engineering; Khandekar, T.N. [Rizvi College of Engineering, Mumbai (India). Dept. of Mechanical Engineering
2007-07-01
India's domestic sector is one of the largest consumers of primary energy, with 90 per cent of household energy attributed to cooking. The demand for cooking energy is increasing annually at a rate of 8.1 per cent. In the residential sector, 75 per cent of energy requirements are met by fuel wood and agricultural waste, while the rest is met by kerosene and liquefied petroleum gas. Solar energy is regarded as a clean and safe source of energy to substitute for conventional fuels. This paper presented historical background on the solar cooker, with particular reference to the development of a low-cost domestic parabolic type solar cooker. The cooker has an aperture area of 1.5 m{sup 2} and provides an adequate temperature for cooking or frying for a family of 3 to 4 persons. The performance of the cooker was tested using international testing standards. The maximum efficiency of the solar cooker was found to be 13.76 per cent. The assembly and disassembly times was 30 to 40 minutes. It was determined that the competitive price of this portable, parabolic solar cooker encourages the substitution of solar energy for conventional energy and can improve the quality of life. 7 refs., 3 tabs., 1 fig.
Cauchy problem for some fractional nonlinear ultra-parabolic equations
Directory of Open Access Journals (Sweden)
Fatma Al-Musalhi
2016-07-01
Full Text Available Blowing-up solutions to nonlocal nonlinear ultra-parabolic equations is presented. The obtained results will contribute in the development of ultra-parabolic equations and enrich the existing non-extensive literature on fractional nonlinear ultra-parabolic problems. Our method of proof relies on a suitable choice of a test function and the weak formulation approach of the sought for solutions.
Bifurcation and stability for a nonlinear parabolic partial differential equation
Chafee, N.
1973-01-01
Theorems are developed to support bifurcation and stability of nonlinear parabolic partial differential equations in the solution of the asymptotic behavior of functions with certain specified properties.
The parabolic Anderson model random walk in random potential
König, Wolfgang
2016-01-01
This is a comprehensive survey on the research on the parabolic Anderson model – the heat equation with random potential or the random walk in random potential – of the years 1990 – 2015. The investigation of this model requires a combination of tools from probability (large deviations, extreme-value theory, e.g.) and analysis (spectral theory for the Laplace operator with potential, variational analysis, e.g.). We explain the background, the applications, the questions and the connections with other models and formulate the most relevant results on the long-time behavior of the solution, like quenched and annealed asymptotics for the total mass, intermittency, confinement and concentration properties and mass flow. Furthermore, we explain the most successful proof methods and give a list of open research problems. Proofs are not detailed, but concisely outlined and commented; the formulations of some theorems are slightly simplified for better comprehension.
Vector domain decomposition schemes for parabolic equations
Vabishchevich, P. N.
2017-09-01
A new class of domain decomposition schemes for finding approximate solutions of timedependent problems for partial differential equations is proposed and studied. A boundary value problem for a second-order parabolic equation is used as a model problem. The general approach to the construction of domain decomposition schemes is based on partition of unity. Specifically, a vector problem is set up for solving problems in individual subdomains. Stability conditions for vector regionally additive schemes of first- and second-order accuracy are obtained.
Optimal Wentzell Boundary Control of Parabolic Equations
Energy Technology Data Exchange (ETDEWEB)
Luo, Yousong, E-mail: yousong.luo@rmit.edu.au [RMIT University, School of Mathematical and Geospatial Sciences (Australia)
2017-04-15
This paper deals with a class of optimal control problems governed by an initial-boundary value problem of a parabolic equation. The case of semi-linear boundary control is studied where the control is applied to the system via the Wentzell boundary condition. The differentiability of the state variable with respect to the control is established and hence a necessary condition is derived for the optimal solution in the case of both unconstrained and constrained problems. The condition is also sufficient for the unconstrained convex problems. A second order condition is also derived.
Qualitative properties of monotone linear parabolic operators
Directory of Open Access Journals (Sweden)
István Faragó
2008-07-01
Full Text Available When we construct mathematical or numerical models in order to solve a real-life problem, it is important to preserve the characteristic properties of the original process. The models have to possess the equivalents of these properties. Parabolic partial equations generally serve as the mathematical models of heat conduction or diffusion processes, where the most important properties are the monotonicity, the nonnegativity preservation and the maximum principles. In this paper, the validity of the equivalents of these qualitative properties are investigated for the second order linear partial differential operator. Conditions are given that guarantee the qualitative properties. On some examples we investigate these conditions.
Parabolic dunes in north-eastern Brazil
Duran, O; Bezerra, L J C; Herrmann, H J; Maia, L P
2007-01-01
In this work we present measurements of vegetation cover over parabolic dunes with different degree of activation along the north-eastern Brazilian coast. We are able to extend the local values of the vegetation cover density to the whole dune by correlating measurements with the gray-scale levels of a high resolution satellite image of the dune field. The empirical vegetation distribution is finally used to validate the results of a recent continuous model of dune motion coupling sand erosion and vegetation growth.
Weston-Green, Katrina; Wallace, Margaret
2016-09-01
A growing body of evidence demonstrates a critical role for effective, meaningful feedback to enhance student learning. Effective feedback can become part of the learning cycle that is not only a learning opportunity for the student but can also be used to inform the teacher and ongoing curriculum development. Feedback is considered particularly important during the first year of university and can even be viewed as a retention strategy that can help attenuate student performance anxieties and solidify perceptions of academic support. Unfortunately, the provision of individualized, timely feedback can be particularly challenging in first-year courses as they tend to be large and diverse cohort classes that pose challenges of time and logistics. Various forms of generic feedback can provide rapid and cost-effect feedback to large cohorts but may be of limited benefit to students other than signaling weaknesses in knowledge. The present study describes a method that was used to provide formative task-related feedback to a large cohort of first-year physiology and anatomy students. Based on student evaluations presented in this study, this method provided feedback in a manner that engaged students, uncovered underlying misconceptions, facilitated peer discussion, and provided opportunity for new instruction while allowing the lecturer to recognize common gaps in knowledge and inform ongoing curriculum development. Copyright © 2016 The American Physiological Society.
A combination of parabolic and grid slope interpolation for 2D tissue displacement estimations.
Albinsson, John; Ahlgren, Åsa Rydén; Jansson, Tomas; Cinthio, Magnus
2017-08-01
Parabolic sub-sample interpolation for 2D block-matching motion estimation is computationally efficient. However, it is well known that the parabolic interpolation gives a biased motion estimate for displacements greater than |y.2| samples (y = 0, 1, …). Grid slope sub-sample interpolation is less biased, but it shows large variability for displacements close to y.0. We therefore propose to combine these sub-sample methods into one method (GS15PI) using a threshold to determine when to use which method. The proposed method was evaluated on simulated, phantom, and in vivo ultrasound cine loops and was compared to three sub-sample interpolation methods. On average, GS15PI reduced the absolute sub-sample estimation errors in the simulated and phantom cine loops by 14, 8, and 24% compared to sub-sample interpolation of the image, parabolic sub-sample interpolation, and grid slope sub-sample interpolation, respectively. The limited in vivo evaluation of estimations of the longitudinal movement of the common carotid artery using parabolic and grid slope sub-sample interpolation and GS15PI resulted in coefficient of variation (CV) values of 6.9, 7.5, and 6.8%, respectively. The proposed method is computationally efficient and has low bias and variance. The method is another step toward a fast and reliable method for clinical investigations of longitudinal movement of the arterial wall.
Quasilinear parabolic variational inequalities with multi-valued lower-order terms
Carl, Siegfried; Le, Vy K.
2014-10-01
In this paper, we provide an analytical frame work for the following multi-valued parabolic variational inequality in a cylindrical domain : Find and an such that where is some closed and convex subset, A is a time-dependent quasilinear elliptic operator, and the multi-valued function is assumed to be upper semicontinuous only, so that Clarke's generalized gradient is included as a special case. Thus, parabolic variational-hemivariational inequalities are special cases of the problem considered here. The extension of parabolic variational-hemivariational inequalities to the general class of multi-valued problems considered in this paper is not only of disciplinary interest, but is motivated by the need in applications. The main goals are as follows. First, we provide an existence theory for the above-stated problem under coercivity assumptions. Second, in the noncoercive case, we establish an appropriate sub-supersolution method that allows us to get existence, comparison, and enclosure results. Third, the order structure of the solution set enclosed by sub-supersolutions is revealed. In particular, it is shown that the solution set within the sector of sub-supersolutions is a directed set. As an application, a multi-valued parabolic obstacle problem is treated.
Rotating hydraulic adjustment in a parabolic channel
Helfrich, K.
2003-04-01
Rotating hydraulics forms the basis of our interpretation of flows through oceanic straits and abyssal passages. These theories are used to predict overflow transport and characteristics of hydraulic features such as jumps. However, details of the transient hydraulic adjustment and the properties of hydraulic jumps and bores have been explored only for unrealistic rectangular cross-section channel geometry. Here the classic problem of upstream influence due to the introduction of an obstacle is extended to a rotating channel with parabolic cross-section. The critical obstacle height for upstream influence as a function of Froude number is found under the assumptions of single-layer (reduced-gravity) semi-geostrophic flow with uniform potential vorticity. The theoretical development is supplemented with two-dimensional numerical simulations of the transient adjustment to hydraulically controlled states. The numerical results reveal novel features including upstream propagating disturbances that consist of both a localized shock-like feature and non-local rarefaction upstream of the shock. The non-locality poses an impediment for the development of a shock-joining theory. Downstream hydraulic jumps from super to subcritical flow occur as both depth and width transitions. However, the lateral expansions in a parabolic channel are not as abrupt as their rectangular channel counterparts. This may help explain the lack of oceanic observations of abrupt hydraulic jumps downstream of abyssal sills.
Directory of Open Access Journals (Sweden)
M. Tshipa
2017-12-01
Full Text Available A theoretical investigation of the effects of spatial variation of confining electric potential on photoionization cross section (PCS in a spherical quantum dot is presented. The potential profiles considered here are the shifted parabolic potential and the inverse lateral shifted parabolic potential compared with the well-studied parabolic potential. The primary findings are that parabolic potential and the inverse lateral shifted parabolic potential blue shift the peaks of the PCS while the shifted parabolic potential causes a red shift.
Manipulation of dielectric particles with nondiffracting parabolic beams.
Ortiz-Ambriz, Antonio; Gutiérrez-Vega, Julio C; Petrov, Dmitri
2014-12-01
The trapping and manipulation of microscopic particles embedded in the structure of nondiffracting parabolic beams is reported. The particles acquire orbital angular momentum and exhibit an open trajectory following the parabolic fringes of the beam. We observe an asymmetry in the terminal velocity of the particles caused by the counteracting gradient and scattering forces.
Surface plasmon polariton beam focusing with parabolic nanoparticle chains
DEFF Research Database (Denmark)
Radko, Ilya P.; Bozhevolnyi, Sergey I.; Evlyukhin, Andrey B.
2007-01-01
We report on the focusing of surface plasmon polariton (SPP) beams with parabolic chains of gold nanoparticles fabricated on thin gold films. SPP focusing with different parabolic chains is investigated in the wavelength range of 700–860 nm, both experimentally and theoretically. Mapping of SPP...
Paul, Cassandra; Weiss, Brenda
2013-01-01
Many instructors choose to assess their students using open-ended written exam items that require students to show their understanding of physics by solving a problem and/or explaining a concept. Grading these items is fairly time consuming, and in large courses time constraints prohibit providing significant individualized feedback on students' exams. Instructors typically cross out areas of the response that are incorrect and write the total points awarded or subtracted. Sometimes, instructors will also write a word or two to indicate the error. This paper describes a grading method that provides greater individualized feedback, clearly communicates to students expected performance levels, takes no more time than traditional grading methods for open-ended responses, and seems to encourage more students to take advantage of the feedback provided.
The First European Parabolic Flight Campaign with the Airbus A310 ZERO-G
Pletser, Vladimir; Rouquette, Sebastien; Friedrich, Ulrike; Clervoy, Jean-Francois; Gharib, Thierry; Gai, Frederic; Mora, Christophe
2016-12-01
Aircraft parabolic flights repetitively provide up to 23 seconds of reduced gravity during ballistic flight manoeuvres. Parabolic flights are used to conduct short microgravity investigations in Physical and Life Sciences and in Technology, to test instrumentation prior to space flights and to train astronauts before a space mission. The use of parabolic flights is complementary to other microgravity carriers (drop towers, sounding rockets), and preparatory to manned space missions on board the International Space Station and other manned spacecraft, such as Shenzhou and the future Chinese Space Station. After 17 years of using the Airbus A300 ZERO-G, the French company Novespace, a subsidiary of the ' Centre National d'Etudes Spatiales' (CNES, French Space Agency), based in Bordeaux, France, purchased a new aircraft, an Airbus A310, to perform parabolic flights for microgravity research in Europe. Since April 2015, the European Space Agency (ESA), CNES and the ` Deutsches Zentrum für Luft- und Raumfahrt e.V.' (DLR, the German Aerospace Center) use this new aircraft, the Airbus A310 ZERO-G, for research experiments in microgravity. The first campaign was a Cooperative campaign shared by the three agencies, followed by respectively a CNES, an ESA and a DLR campaign. This paper presents the new Airbus A310 ZERO-G and its main characteristics and interfaces for scientific experiments. The experiments conducted during the first European campaign are presented.
Yan, Na; Baas, Andreas C. W.
2016-04-01
Parabolic dunes are a quintessential example of the co-evolution of soil, landform, and vegetation, and they are found around the world, on coasts, river valleys, lake shores, and margins of deserts and steppes. These areas are often sensitive to changes in natural and anthropogenic forcings and socio-economic activities. Some studies have indicated parabolic dunes can lose vegetation and transform into barchan and transverse dunes by environmental change such as decreased precipitation or lowered water table, as well as anthropogenic stress such as increased burning and grazing. These transformations and shifts between states of eco-geomorphic systems may have significant implications on land management and social-economic development. This study utilises the Extended-DECAL - parameterised by field measurements of dune topography and vegetation characteristics combined with remote sensing - to explore how increases in drought stress, wind strength, and grazing stress may lead to the activation of stabilised parabolic dunes into highly mobile barchans. The modelling results show that the mobility of an initial parabolic dune at the outset of perturbations determines to a large extent the capacity of a system to absorb the environmental change, and a slight increase in vegetation cover of an initial parabolic dune can increase the activation threshold significantly. Plants with a higher deposition tolerance increase the activation threshold for the climatic impact and sand transport rate, whereas the erosion tolerance of plants influences the patterns of resulting barchans. The change in the characteristics of eco-geomorphic interaction zones may indirectly reflect the dune stability and predict an ongoing transformation, whilst the activation angle may be potentially used as a proxy of environmental stresses. In contrast to the natural environmental changes which tend to affect relatively weak and young plants, grazing stress can exert a broader impact on all
Microgravity Active Vibration Isolation System on Parabolic Flights
Dong, Wenbo; Pletser, Vladimir; Yang, Yang
2016-07-01
The Microgravity Active Vibration Isolation System (MAIS) aims at reducing on-orbit vibrations, providing a better controlled lower gravity environment for microgravity physical science experiments. The MAIS will be launched on Tianzhou-1, the first cargo ship of the China Manned Space Program. The principle of the MAIS is to suspend with electro-magnetic actuators a scientific payload, isolating it from the vibrating stator. The MAIS's vibration isolation capability is frequency-dependent and a decrease of vibration of about 40dB can be attained. The MAIS can accommodate 20kg of scientific payload or sample unit, and provide 30W of power and 1Mbps of data transmission. The MAIS is developed to support microgravity scientific experiments on manned platforms in low earth orbit, in order to meet the scientific requirements for fluid physics, materials science, and fundamental physics investigations, which usually need a very quiet environment, increasing their chances of success and their scientific outcomes. The results of scientific experiments and technology tests obtained with the MAIS will be used to improve future space based research. As the suspension force acting on the payload is very small, the MAIS can only be operative and tested in a weightless environment. The 'Deutsches Zentrum für Luft- und Raumfahrt e.V.' (DLR, German Aerospace Centre) granted a flight opportunity to the MAIS experiment to be tested during its 27th parabolic flight campaign of September 2015 performed on the A310 ZERO-G aircraft managed by the French company Novespace, a subsidiary of the 'Centre National d'Etudes Spatiales' (CNES, French Space Agency). The experiment results confirmed that the 6 degrees of freedom motion control technique was effective, and that the vibration isolation performance fulfilled perfectly the expectations based on theoretical analyses and simulations. This paper will present the design of the MAIS and the experiment results obtained during the
A parabolic model of drag coefficient for storm surge simulation in the South China Sea
Peng, Shiqiu; Li, Yineng
2015-01-01
Drag coefficient (Cd) is an essential metric in the calculation of momentum exchange over the air-sea interface and thus has large impacts on the simulation or forecast of the upper ocean state associated with sea surface winds such as storm surges. Generally, Cd is a function of wind speed. However, the exact relationship between Cd and wind speed is still in dispute, and the widely-used formula that is a linear function of wind speed in an ocean model could lead to large bias at high wind speed. Here we establish a parabolic model of Cd based on storm surge observations and simulation in the South China Sea (SCS) through a number of tropical cyclone cases. Simulation of storm surges for independent Tropical cyclones (TCs) cases indicates that the new parabolic model of Cd outperforms traditional linear models. PMID:26499262
DEFF Research Database (Denmark)
Willems, Sara M; Wright, Daniel J.; Day, Felix R
2017-01-01
Hand grip strength is a widely used proxy of muscular fitness, a marker of frailty, and predictor of a range of morbidities and all-cause mortality. To investigate the genetic determinants of variation in grip strength, we perform a large-scale genetic discovery analysis in a combined sample of 195...... with involvement of psychomotor impairment (PEX14, LRPPRC and KANSL1). Mendelian randomization analyses are consistent with a causal effect of higher genetically predicted grip strength on lower fracture risk. In conclusion, our findings provide new biological insight into the mechanistic underpinnings of grip...
Multigrid and preconditioning strategies for implicit PDE solvers for degenerate parabolic equations
Semplice, Matteo; Donatelli, Marco; Serra-Capizzano, Stefano
2009-01-01
The novel contribution of this paper relies in the proposal of a fully implicit numerical method designed for nonlinear degenerate parabolic equations, in its convergence/stability analysis, and in the study of the related computational cost. In fact, due to the nonlinear nature of the underlying mathematical model, the use of a fixed point scheme is required and every step implies the solution of large, locally structured, linear systems. A special effort is devoted to the spectral analysis ...
Hao, Dapeng; Wang, Guangyu; Yin, Zuojing; Li, Chuanxing; Cui, Yan; Zhou, Meng
2014-11-01
One important piece of information about the human Mendelian disorders is the mode of inheritance. Recent studies of human genetic diseases on a large scale have provided many novel insights into the underlying molecular mechanisms. However, most successful analyses ignored the mode of inheritance of diseases, which severely limits our understanding of human disease mechanisms relating to the mode of inheritance at the large scale. Therefore, we here conducted a systematic large-scale study of the inheritance mode of Mendelian disorders, to bring new insight into human diseases. Our analyses include the comparison between dominant and recessive disease genes on both genomic and proteomic characteristics, Mendelian mutations, protein network properties and disease connections on both the genetic and the population levels. We found that dominant disease genes are more functionally central, topological central and more sensitive to disease outcome. On the basis of these findings, we suggested that dominant diseases should have higher genetic heterogeneity and should have more comprehensive connections with each other compared with recessive diseases, a prediction we confirm by disease network and disease comorbidity.
Radio wave propagation and parabolic equation modeling
Apaydin, Gokhan
2018-01-01
A thorough understanding of electromagnetic wave propagation is fundamental to the development of sophisticated communication and detection technologies. The powerful numerical methods described in this book represent a major step forward in our ability to accurately model electromagnetic wave propagation in order to establish and maintain reliable communication links, to detect targets in radar systems, and to maintain robust mobile phone and broadcasting networks. The first new book on guided wave propagation modeling and simulation to appear in nearly two decades, Radio Wave Propagation and Parabolic Equation Modeling addresses the fundamentals of electromagnetic wave propagation generally, with a specific focus on radio wave propagation through various media. The authors explore an array of new applications, and detail various v rtual electromagnetic tools for solving several frequent electromagnetic propagation problems. All of the methods described are presented within the context of real-world scenari...
Two new designs of parabolic solar collectors
Directory of Open Access Journals (Sweden)
Karimi Sadaghiyani Omid
2014-01-01
Full Text Available In this work, two new compound parabolic trough and dish solar collectors are presented with their working principles. First, the curves of mirrors are defined and the mathematical formulation as one analytical method is used to trace the sun rays and recognize the focus point. As a result of the ray tracing, the distribution of heat flux around the inner wall can be reached. Next, the heat fluxes are calculated versus several absorption coefficients. These heat flux distributions around absorber tube are functions of angle in polar coordinate system. Considering, the achieved heat flux distribution are used as a thermal boundary condition. After that, Finite Volume Methods (FVM are applied for simulation of absorber tube. The validation of solving method is done by comparing with Dudley's results at Sandia National Research Laboratory. Also, in order to have a good comparison between LS-2 and two new designed collectors, some of their parameters are considered equal with together. These parameters are consist of: the aperture area, the measures of tube geometry, the thermal properties of absorber tube, the working fluid, the solar radiation intensity and the mass flow rate of LS-2 collector are applied for simulation of the new presented collectors. After the validation of the used numerical models, this method is applied to simulation of the new designed models. Finally, the outlet results of new designed collector are compared with LS-2 classic collector. Obviously, the obtained results from the comparison show the improving of the new designed parabolic collectors efficiency. In the best case-study, the improving of efficiency are about 10% and 20% for linear and convoluted models respectively.
Design of a Thermal Imaging Diagnostic Using 90-Degree, Off-Axis, Parabolic Mirrors
Energy Technology Data Exchange (ETDEWEB)
Malone, Robert M.; Becker, Steven A.; Dolan, Daniel H.; Hacking, Richard G.; Hickman, Randy J.; Kaufman, Morris I.; Stevens, Gerald D.; Turley, William D.
2006-09-01
Thermal imaging is an important, though challenging, diagnostic for shockwave experiments. Shock-compressed materials undergo transient temperature changes that cannot be recorded with standard (greater than ms response time) infrared detectors. A further complication arises when optical elements near the experiment are destroyed. We have designed a thermal-imaging system for studying shock temperatures produced inside a gas gun at Sandia National Laboratories. Inexpensive, diamond-turned, parabolic mirrors relay an image of the shocked target to the exterior of the gas gun chamber through a sapphire vacuum port. The 3000–5000-nm portion of this image is directed to an infrared camera which acquires a snapshot of the target with a minimum exposure time of 150 ns. A special mask is inserted at the last intermediate image plane, to provide dynamic thermal background recording during the event. Other wavelength bands of this image are split into high-speed detectors operating at 900–1700 nm, and at 1700–3000 nm for timeresolved pyrometry measurements. This system incorporates 90-degree, off-axis parabolic mirrors, which can collect low f/# light over a broad spectral range, for high-speed imaging. Matched mirror pairs must be used so that aberrations cancel. To eliminate image plane tilt, proper tip-to-tip orientation of the parabolic mirrors is required. If one parabolic mirror is rotated 180 degrees about the optical axis connecting the pair of parabolic mirrors, the resulting image is tilted by 60 degrees. Different focal-length mirrors cannot be used to magnify the image without substantially sacrificing image quality. This paper analyzes performance and aberrations of this imaging diagnostic.
Baker, Michael G; Zhang, Jane; Blakely, Tony; Crane, Julian; Saville-Smith, Kay; Howden-Chapman, Philippa
2016-02-16
Despite the importance of adequate, un-crowded housing as a prerequisite for good health, few large cohort studies have explored the health effects of housing conditions. The Social Housing Outcomes Worth (SHOW) Study was established to assess the relationship between housing conditions and health, particularly between household crowding and infectious diseases. This paper reports on the methods and feasibility of using a large administrative housing database for epidemiological research and the characteristics of the social housing population. This prospective open cohort study was established in 2003 in collaboration with Housing New Zealand Corporation which provides housing for approximately 5% of the population. The Study measures health outcomes using linked anonymised hospitalisation and mortality records provided by the New Zealand Ministry of Health. It was possible to match the majority (96%) of applicant and tenant household members with their National Health Index (NHI) number allowing linkage to anonymised coded data on their hospitalisations and mortality. By December 2011, the study population consisted of 11,196 applicants and 196,612 tenants. Half were less than 21 years of age. About two-thirds identified as Māori or Pacific ethnicity. Household incomes were low. Of tenant households, 44% containing one or more smokers compared with 33% for New Zealand as a whole. Exposure to household crowding, as measured by a deficit of one or more bedrooms, was common for applicants (52%) and tenants (38%) compared with New Zealanders as whole (10%). This project has shown that an administrative housing database can be used to form a large cohort population and successfully link cohort members to their health records in a way that meets confidentiality and ethical requirements. This study also confirms that social housing tenants are a highly deprived population with relatively low incomes and high levels of exposure to household crowding and environmental
Degenerate parabolic equations appearing in atmospheric dispersion of pollutants
Directory of Open Access Journals (Sweden)
Veli Shakhmurov
2016-12-01
Full Text Available Linear and nonlinear degenerate abstract parabolic equations with variable coefficients are studied. Here the equation and boundary conditions are degenerated on all boundary and contain some parameters. The linear problem is considered on the moving domain. The separability properties of elliptic and parabolic problems in mixed $L_p$ spaces are obtained. Moreover, the existence and uniqueness of optimal regular solution of mixed problem for nonlinear parabolic equation is established. Note that, these problems arise in fluid mechanics and environmental engineering.
Towards standardization of in-site parabolic trough collector testing in solar thermal power plants
Sallaberry, Fabienne; Valenzuela, Loreto; de Jalón, Alberto García; Leon, Javier; Bernad, Ignacio David
2016-05-01
This paper presents a summary of the testing procedure and a validation of the methodology of parabolic trough collector in solar thermal power plants. The applied testing methodology is the one proposed within the Spanish standardization sub-committee AEN/CTN 206/SC117 working group WG2 related to the components for solar thermal power plants. This methodology is also proposed within the international committee IEC TC 117 (Standard draft IEC 62862-3-2 Ed. 1.0). This study is done at Plataforma Solar de Almería (PSA) in Almeria within the European project STAGE-STE. This paper presents the results of the optical and thermal efficiency of a large-size parabolic trough collector. The obtained values are similar to the previous analysis on this collector by PSA. The results of the tracking system have a good accuracy compared to the acceptance angle of the concentrator.
DEVELOPMENT AND PRELIMINARY TESTING OF A PARABOLIC TROUGH SOLAR WATER HEATER
Directory of Open Access Journals (Sweden)
O. A. Lasode
2011-06-01
Full Text Available Solar energy is a high-temperature, high-energy radiant energy source, with tremendous advantages over other alternative energy sources. It is a reliable, robust renewable resource which is largely undeveloped. The design and fabrication of parabolic trough solar water heater for water heating was executed. The procedure employed includes the design, construction and testing stages. The equipment which is made up of the reflector surface (curved mirror, reflector support, absorber pipe and a stand was fabricated using locally sourced materials. The results obtained. compared favourably with other research works in the literature. It depicts that employing a suitable design, selection of time of heating and proper focusing of the reflected rays to the focal spot region, solar radiation can efficiently be utilized for water heating in a tropical environment. This work presents a parabolic trough solar water heater as a suitable renewable energy technology for reducing water-heating costs.
Gas Turbine/Solar Parabolic Trough Hybrid Design Using Molten Salt Heat Transfer Fluid: Preprint
Energy Technology Data Exchange (ETDEWEB)
Turchi, C. S.; Ma, Z.
2011-08-01
Parabolic trough power plants can provide reliable power by incorporating either thermal energy storage (TES) or backup heat from fossil fuels. This paper describes a gas turbine / parabolic trough hybrid design that combines a solar contribution greater than 50% with gas heat rates that rival those of natural gas combined-cycle plants. Previous work illustrated benefits of integrating gas turbines with conventional oil heat-transfer-fluid (HTF) troughs running at 390?C. This work extends that analysis to examine the integration of gas turbines with salt-HTF troughs running at 450 degrees C and including TES. Using gas turbine waste heat to supplement the TES system provides greater operating flexibility while enhancing the efficiency of gas utilization. The analysis indicates that the hybrid plant design produces solar-derived electricity and gas-derived electricity at lower cost than either system operating alone.
Classification of conformal representations induced from the maximal cuspidal parabolic
Energy Technology Data Exchange (ETDEWEB)
Dobrev, V. K., E-mail: dobrev@inrne.bas.bg [Scuola Internazionale Superiore di Studi Avanzati (Italy)
2017-03-15
In the present paper we continue the project of systematic construction of invariant differential operators on the example of representations of the conformal algebra induced from the maximal cuspidal parabolic.
Quasiconformal mappings and degenerate elliptic and parabolic equations
Directory of Open Access Journals (Sweden)
Filippo Chiarenza
1987-11-01
Full Text Available In this paper two Harnak inequalities are proved concerning a degenerate elliptic and a degenerate parabolic equation. In both cases the weight giving the degeneracy is a power of the jacobian of a quasiconformal mapping.
Solving Variable Coefficient Fourth-Order Parabolic Equation by ...
African Journals Online (AJOL)
In this paper, a Modified initial guess Variational Iteration Method (MigVIM) is used to solve a non-homogeneous variable coefficient fourth order parabolic partial differential equations. The new method shows rapid convergence to the exact solution.
Hoar, T. J.; Anderson, J. L.; Collins, N.; Kershaw, H.; Hendricks, J.; Raeder, K.; Mizzi, A. P.; Barré, J.; Gaubert, B.; Madaus, L. E.; Aydogdu, A.; Raeder, J.; Arango, H.; Moore, A. M.; Edwards, C. A.; Curchitser, E. N.; Escudier, R.; Dussin, R.; Bitz, C. M.; Zhang, Y. F.; Shrestha, P.; Rosolem, R.; Rahman, M.
2016-12-01
Strongly-coupled ensemble data assimilation with multiple high-resolution model components requires massive state vectors which need to be efficiently stored and accessed throughout the assimilation process. Supercomputer architectures are tending towards increasing the number of cores per node but have the same or less memory per node. Recent advances in the Data Assimilation Research Testbed (DART), a freely-available community ensemble data assimilation facility that works with dozens of large geophysical models, have addressed the need to run with a smaller memory footprint on a higher node count by utilizing MPI-2 one-sided communication to do non-blocking asynchronous access of distributed data. DART runs efficiently on many computational platforms ranging from laptops through thousands of cores on the newest supercomputers. Benefits of the new DART implementation will be shown. In addition, overviews of the most recently supported models will be presented: CAM-CHEM, WRF-CHEM, CM1, OpenGGCM, FESOM, ROMS, CICE5, TerrSysMP (COSMO, CLM, ParFlow), JULES, and CABLE. DART provides a comprehensive suite of software, documentation, and tutorials that can be used for ensemble data assimilation research, operations, and education. Scientists and software engineers at NCAR are available to support DART users who want to use existing DART products or develop their own applications. Current DART users range from university professors teaching data assimilation, to individual graduate students working with simple models, through national laboratories and state agencies doing operational prediction with large state-of-the-art models.
Directory of Open Access Journals (Sweden)
Yang Liu
2012-01-01
Full Text Available A new positive definite expanded mixed finite element method is proposed for parabolic partial integrodifferential equations. Compared to expanded mixed scheme, the new expanded mixed element system is symmetric positive definite and both the gradient equation and the flux equation are separated from its scalar unknown equation. The existence and uniqueness for semidiscrete scheme are proved and error estimates are derived for both semidiscrete and fully discrete schemes. Finally, some numerical results are provided to confirm our theoretical analysis.
Current-voltage relation for thin tunnel barriers: Parabolic barrier model
DEFF Research Database (Denmark)
Hansen, Kim; Brandbyge, Mads
2004-01-01
We derive a simple analytic result for the current-voltage curve for tunneling of electrons through a thin uniform insulating layer modeled by a parabolic barrier. Our model, which goes beyond the Wentzel–Kramers–Brillouin approximation, is applicable also in the limit of highly transparant...... barriers subject to high voltages, and thus provides a more realistic description for this situation compared to the widely used rectangular barrier model. ©2004 American Institute of Physics....
Periodic optical delay line based on a tilted parabolic generatrix helicoid reflective mirror.
Wang, Yuebin; Wang, Changlei; Xing, Qirong; Liu, Feng; Li, Yanfeng; Chai, Lu; Wang, Qingyue; Fang, Fengzhou; Zhang, Xiaodong
2009-04-10
We report the design and testing of a novel linear scanning periodic optical delay line (ODL) by use of a helicoid reflective mirror based on a tilted parabolic generatrix that was driven by an electrical motor for a periodic change in the optical path length of the reflected light beam. The divergence and pulse front distortion of the optical beam reflected by the helicoid reflective mirror were simulated based on differential geometry. With a round-trip pass arrangement, a scanning range of delay time as large as 100 ps was obtained by spinning the helicoid reflective mirror with a pitch distance of 7.5 mm. This periodic ODL was used in an optical second-harmonic generation autocorrelator to test the linearity and temporal resolution in comparison with the autocorrelation signal obtained using an ODL structured with a motorized linear translation stage. Experiments demonstrate that our helicoid optical delay device may provide exceptional performance for optical interference, high-resolution terahertz time-domain spectroscopy, and general optical pump-probe experiments.
Owhadi, Houman; Zhang, Lei
2017-10-01
Implicit schemes are popular methods for the integration of time dependent PDEs such as hyperbolic and parabolic PDEs. However the necessity to solve corresponding linear systems at each time step constitutes a complexity bottleneck in their application to PDEs with rough coefficients. We present a generalization of gamblets introduced in [62] enabling the resolution of these implicit systems in near-linear complexity and provide rigorous a-priori error bounds on the resulting numerical approximations of hyperbolic and parabolic PDEs. These generalized gamblets induce a multiresolution decomposition of the solution space that is adapted to both the underlying (hyperbolic and parabolic) PDE (and the system of ODEs resulting from space discretization) and to the time-steps of the numerical scheme.
Affective states and adaptation to parabolic flights
Collado, Aurélie; Langlet, Cécile; Tzanova, Tzvetomira; Hainaut, Jean-Philippe; Monfort, Vincent; Bolmont, Benoît
2017-05-01
This exploratory study investigates (i) inter-individual variations of affective states before a parabolic flight (i.e., PF) on the basis of quality of adaptation to physical demands, and (ii) intra-individual variations of affective states during a PF. Mood-states, state-anxiety and salivary cortisol were assessed in two groups with a different quality of adaptation (an Adaptive Group, i.e., AG, and a Maladaptive Group, i.e., MG) before and during a PF. Before PF, MG scored higher on mood states (Anger-Hostility, Fatigue-Inertia) than AG. During the flight, while AG seemed to present ;normal; affective responses to the demanding environment (e.g., increase in salivary cortisol), MG presented increases in mood states such as Confusion-Bewilderment or Tension-Anxiety. The findings suggest that the psychological states of MG could have disturbed their ability to integrate sensory information from an unusual environment, which led to difficulties in coping with the physical demands of PF.
Parabolic Trough Receiver Heat Loss Testing (Poster)
Energy Technology Data Exchange (ETDEWEB)
Price, H.; Netter, J.; Bingham, C.; Kutscher, C.; Burkholder, F.; Brandemuehl, M.
2007-03-01
Parabolic trough receivers, or heat collection elements (HCEs), absorb sunlight focused by the mirrors and transfer that thermal energy to a fluid flowing within them. Thje absorbing tube of these receivers typically operates around 400 C (752 F). HCE manufacturers prevent thermal loss from the absorbing tube to the environment by using sputtered selective Cermet coatings on the absorber and by surrounding the absorber with a glass-enclosed evacuated annulus. This work quantifies the heat loss of the Solel UVAC2 and Schott PTR70 HCEs. At 400 C, the HCEs perform similarly, losing about 400 W/m of HCE length. To put this in perspective, the incident beam radiation on a 5 m mirror aperture is about 4500 W/m, with about 75% of that energy ({approx} 3400 W/m) reaching the absorber surface. Of the 3400 W/m on the absorber, about 3000 W/m is absorbed into the working fluid while 400 W/m is lost to the environment.
Parabolic Trough Solar Collector Initial Trials
Directory of Open Access Journals (Sweden)
Ghalya Pikra
2012-03-01
Full Text Available This paper discusses initial trials of parabolic trough solar collector (PTSC in Bandung. PTSC model consists of concentrator, absorber and tracking system. Concentrator designs are made with 2m aperture width, 6m length and 0.75m focal distance. The design is equipped with an automatic tracking system which is driven using 12V and 24Watt DC motor with 0.0125rpm rotational speed. Absorber/receiver is designed with evacuated tube type, with 1 inch core diameter and tube made of AISI304 and coated with black oxide, the outer tube is borosilicate glass with a 70 mm diameter and 1.5 m length. Working fluid stored in single type of thermal storage tank, a single phase with 37.7 liter volume. PTSC model testing carried out for 2 hours and 10 minutes produces heat output and input of 11.5 kW and 0.64 kW respectively.
Non-parabolic isothermal oxidation kinetics of low pressure plasma sprayed MCrAlY bond coat
Zhang, Bang-Yan; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu
2017-06-01
The non-parabolic isothermal oxidation kinetics of low pressure plasma sprayed MCrAlY bond coat was investigated. To qualitatively explain the abnormal growth phenomenon of thermally grown oxides (TGO), the changes that occurred to their microstructure during the oxidation process were studied. Based on these observations, a modified model was developed to understand and quantitatively predict the non-parabolic oxidation and growth kinetics of TGO. This modified model, which fits well with experimental results, provides a novel method to quantitatively predict the long-term growth behaviour of TGO, and thereby benefits the development of long-life and highly reliable thermal barrier coatings.
Directory of Open Access Journals (Sweden)
Mandy Muller
Full Text Available Human Papillomaviruses (HPV cause widespread infections in humans, resulting in latent infections or diseases ranging from benign hyperplasia to cancers. HPV-induced pathologies result from complex interplays between viral proteins and the host proteome. Given the major public health concern due to HPV-associated cancers, most studies have focused on the early proteins expressed by HPV genotypes with high oncogenic potential (designated high-risk HPV or HR-HPV. To advance the global understanding of HPV pathogenesis, we mapped the virus/host interaction networks of the E2 regulatory protein from 12 genotypes representative of the range of HPV pathogenicity. Large-scale identification of E2-interaction partners was performed by yeast two-hybrid screenings of a HaCaT cDNA library. Based on a high-confidence scoring scheme, a subset of these partners was then validated for pair-wise interaction in mammalian cells with the whole range of the 12 E2 proteins, allowing a comparative interaction analysis. Hierarchical clustering of E2-host interaction profiles mostly recapitulated HPV phylogeny and provides clues to the involvement of E2 in HPV infection. A set of cellular proteins could thus be identified discriminating, among the mucosal HPV, E2 proteins of HR-HPV 16 or 18 from the non-oncogenic genital HPV. The study of the interaction networks revealed a preferential hijacking of highly connected cellular proteins and the targeting of several functional families. These include transcription regulation, regulation of apoptosis, RNA processing, ubiquitination and intracellular trafficking. The present work provides an overview of E2 biological functions across multiple HPV genotypes.
Klitsner, I. N.; Borok, G. M.; Neinstein, L.; MacKenzie, R.
1992-01-01
Adolescents are at risk for pregnancy, sexually transmitted diseases, suicide, homicide, accidents, and substance abuse. Adolescent medicine involves an overlap of many skills needed to provide routine medical care, as well as care for those conditions that require psychosocial assessment. We report the results of a mail survey covering care of this age group by practitioners of pediatrics, internal medicine, obstetrics and gynecology, family practice, and adolescent medicine in a large, multispecialty, prepaid group practice. The mail survey covered 10 areas of adolescent care. Adolescent medicine physicians expressed the highest level of perceived knowledge and competence in these areas, with family practitioners ranked second. More than 50% of internists and pediatricians felt only fair to poor competence for a variety of adolescent conditions, whereas a third of internists and pediatricians reported that they liked to care for adolescents. Physicians in all 4 of the primary care specialties reported a need for a teen health center for both consultation and education. These results are similar to those reported for pediatricians and primary care physicians in private practice and for residents in internal medicine. PMID:1615655
Energy Technology Data Exchange (ETDEWEB)
Tzimis, A.; Savvidis, P. G. [Department of Materials Science and Technology, University of Crete, 71003 Heraklion, Crete (Greece); Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, 71110 Heraklion, Crete (Greece); Trifonov, A. V.; Ignatiev, I. V. [Spin Optics Laboratory, State University of Saint-Petersburg, 1 Ulianovskaya, 198504 St. Petersburg (Russian Federation); Christmann, G.; Tsintzos, S. I. [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, 71110 Heraklion, Crete (Greece); Hatzopoulos, Z. [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, 71110 Heraklion, Crete (Greece); Department of Physics, University of Crete, 71003 Heraklion, Crete (Greece); Kavokin, A. V. [Spin Optics Laboratory, State University of Saint-Petersburg, 1 Ulianovskaya, 198504 St. Petersburg (Russian Federation); School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)
2015-09-07
We report observation of strong light-matter coupling in an AlGaAs microcavity (MC) with an embedded single parabolic quantum well. The parabolic potential is achieved by varying aluminum concentration along the growth direction providing equally spaced energy levels, as confirmed by Brewster angle reflectivity from a reference sample without MC. It acts as an active region of the structure which potentially allows cascaded emission of terahertz (THz) light. Spectrally and time resolved pump-probe spectroscopy reveals characteristic quantum beats whose frequencies range from 0.9 to 4.5 THz, corresponding to energy separation between relevant excitonic levels. The structure exhibits strong stimulated nonlinear emission with simultaneous transition to weak coupling regime. The present study highlights the potential of such devices for creating cascaded relaxation of bosons, which could be utilized for THz emission.
Full parabolic trough qualification from prototype to demonstration loop
Janotte, Nicole; Lüpfert, Eckhard; Pottler, Klaus; Schmitz, Mark
2017-06-01
On the example of the HelioTrough® collector development the full accompanying and supporting qualification program for large-scale parabolic trough collectors for solar thermal power plants is described from prototype to demonstration loop scale. In the evaluation process the actual state and the optimization potential are assessed. This includes the optical and geometrical performance determined by concentrator shape, deformation, assembly quality and local intercept factor values. Furthermore, its mechanical performance in terms of tracking accuracy and torsional stiffness and its thermal system performance on the basis of the overall thermal output and heat loss are evaluated. Demonstration loop tests deliver results of collector modules statistical slope deviation of 1.9 to 2.6 mrad, intercept factor above 98%, peak optical performance of 81.6% and heat loss coefficients from field tests. The benefit of such a closely monitored development lies in prompt feedback on strengths, weaknesses and potential improvements on the new product at any development stage from first module tests until demonstration loop evaluation. The product developer takes advantage of the achieved technical maturity, already before the implementation in a commercial power plant. The well-understood performance characteristics allow the reduction of safety margins making the new HelioTrough collector competitive from the start.
Global Existence and Blowup for a Parabolic Equation with a Non-Local Source and Absorption
DEFF Research Database (Denmark)
Ling, Zhi; Lin, Zhigui; Pedersen, Michael
2013-01-01
In this paper we consider a double fronts free boundary problem for a parabolic equation with a non-local source and absorption. The long time behaviors of the solutions are given and the properties of the free boundaries are discussed. Our results show that if the initial value is sufficiently l...... large, then the solution blows up in finite time, while the global fast solution exists for sufficiently small initial data, and the intermediate case with suitably large initial data gives the existence of the global slow solution....
Review of Large Spacecraft Deployable Membrane Antenna Structures
Liu, Zhi-Quan; Qiu, Hui; Li, Xiao; Yang, Shu-Li
2017-11-01
The demand for large antennas in future space missions has increasingly stimulated the development of deployable membrane antenna structures owing to their light weight and small stowage volume. However, there is little literature providing a comprehensive review and comparison of different membrane antenna structures. Space-borne membrane antenna structures are mainly classified as either parabolic or planar membrane antenna structures. For parabolic membrane antenna structures, there are five deploying and forming methods, including inflation, inflation-rigidization, elastic ribs driven, Shape Memory Polymer (SMP)-inflation, and electrostatic forming. The development and detailed comparison of these five methods are presented. Then, properties of membrane materials (including polyester film and polyimide film) for parabolic membrane antennas are compared. Additionally, for planar membrane antenna structures, frame shapes have changed from circular to rectangular, and different tensioning systems have emerged successively, including single Miura-Natori, double, and multi-layer tensioning systems. Recent advances in structural configurations, tensioning system design, and dynamic analysis for planar membrane antenna structures are investigated. Finally, future trends for large space membrane antenna structures are pointed out and technical problems are proposed, including design and analysis of membrane structures, materials and processes, membrane packing, surface accuracy stability, and test and verification technology. Through a review of large deployable membrane antenna structures, guidance for space membrane-antenna research and applications is provided.
Verification of the Microgravity Active Vibration Isolation System based on Parabolic Flight
Zhang, Yong-kang; Dong, Wen-bo; Liu, Wei; Li, Zong-feng; Lv, Shi-meng; Sang, Xiao-ru; Yang, Yang
2017-12-01
The Microgravity active vibration isolation system (MAIS) is a device to reduce on-orbit vibration and to provide a lower gravity level for certain scientific experiments. MAIS system is made up of a stator and a floater, the stator is fixed on the spacecraft, and the floater is suspended by electromagnetic force so as to reduce the vibration from the stator. The system has 3 position sensors, 3 accelerometers, 8 Lorentz actuators, signal processing circuits and a central controller embedded in the operating software and control algorithms. For the experiments on parabolic flights, a laptop is added to MAIS for monitoring and operation, and a power module is for electric power converting. The principle of MAIS is as follows: the system samples the vibration acceleration of the floater from accelerometers, measures the displacement between stator and floater from position sensitive detectors, and computes Lorentz force current for each actuator so as to eliminate the vibration of the scientific payload, and meanwhile to avoid crashing between the stator and the floater. This is a motion control technic in 6 degrees of freedom (6-DOF) and its function could only be verified in a microgravity environment. Thanks for DLR and Novespace, we get a chance to take the DLR 27th parabolic flight campaign to make experiments to verify the 6-DOF control technic. The experiment results validate that the 6-DOF motion control technique is effective, and vibration isolation performance perfectly matches what we expected based on theoretical analysis and simulation. The MAIS has been planned on Chinese manned spacecraft for many microgravity scientific experiments, and the verification on parabolic flights is very important for its following mission. Additionally, we also test some additional function by microgravity electromagnetic suspension, such as automatic catching and locking and working in fault mode. The parabolic flight produces much useful data for these experiments.
Verification of the Microgravity Active Vibration Isolation System based on Parabolic Flight
Zhang, Yong-kang; Dong, Wen-bo; Liu, Wei; Li, Zong-feng; Lv, Shi-meng; Sang, Xiao-ru; Yang, Yang
2017-09-01
The Microgravity active vibration isolation system (MAIS) is a device to reduce on-orbit vibration and to provide a lower gravity level for certain scientific experiments. MAIS system is made up of a stator and a floater, the stator is fixed on the spacecraft, and the floater is suspended by electromagnetic force so as to reduce the vibration from the stator. The system has 3 position sensors, 3 accelerometers, 8 Lorentz actuators, signal processing circuits and a central controller embedded in the operating software and control algorithms. For the experiments on parabolic flights, a laptop is added to MAIS for monitoring and operation, and a power module is for electric power converting. The principle of MAIS is as follows: the system samples the vibration acceleration of the floater from accelerometers, measures the displacement between stator and floater from position sensitive detectors, and computes Lorentz force current for each actuator so as to eliminate the vibration of the scientific payload, and meanwhile to avoid crashing between the stator and the floater. This is a motion control technic in 6 degrees of freedom (6-DOF) and its function could only be verified in a microgravity environment. Thanks for DLR and Novespace, we get a chance to take the DLR 27th parabolic flight campaign to make experiments to verify the 6-DOF control technic. The experiment results validate that the 6-DOF motion control technique is effective, and vibration isolation performance perfectly matches what we expected based on theoretical analysis and simulation. The MAIS has been planned on Chinese manned spacecraft for many microgravity scientific experiments, and the verification on parabolic flights is very important for its following mission. Additionally, we also test some additional function by microgravity electromagnetic suspension, such as automatic catching and locking and working in fault mode. The parabolic flight produces much useful data for these experiments.
Absorber Tube with Internal Pin-Fins for Solar Parabolic Trough Collector
Directory of Open Access Journals (Sweden)
Kalidasan B.
2016-01-01
Full Text Available Solar parabolic trough collectors exploit solar energy for power generation in solar thermal power stations. These systems require long arrays of reflective troughs with absorber tube running along the axis of parabolic dish. A successful attempt to reduce the length of arrays was accomplished by experimentally analysing the modifications done in absorber tube. Two out of three tubes were fabricated and they were employed to obtain the performance parameters through experimentation conducted at VIT University, Vellore, India. Distilled water was used as the working fluid. Maximum efficiency of 39.12% was obtained at 451.6 W/m2 of direct normal irradiance (DNI for absorber tube with internal pin-fins and without glass tube (AFWGt compared to 8.15% obtained at same value of DNI and other conditions for simple absorber tube without glass cover (AWGt. Cylindrical parabolic trough available at the university was utilized, providing the basis for designing and fabrication of the tubes. Plots for varying mass flow rate at interval of 10 minutes were made against instantaneous thermal efficiency and heat utilized, for direct normal irradiance vs. temperature difference across the tubes and instantaneous thermal efficiency. Through the experimentation conducted, better performance was procured compared to earlier works. Thus, the proposal infers that absorber tube with internal fins has good scope for its application, both domestically as well as industrially. It also calls for further research and development of proposed techniques so as to achieve better performance curves.
Bayesian Inference for Linear Parabolic PDEs with Noisy Boundary Conditions
Ruggeri, Fabrizio
2016-01-06
In this work we develop a hierarchical Bayesian setting to infer unknown parameters in initial-boundary value problems (IBVPs) for one-dimensional linear parabolic partial differential equations. Noisy boundary data and known initial condition are assumed. We derive the likelihood function associated with the forward problem, given some measurements of the solution field subject to Gaussian noise. Such function is then analytically marginalized using the linearity of the equation. Gaussian priors have been assumed for the time-dependent Dirichlet boundary values. Our approach is applied to synthetic data for the one-dimensional heat equation model, where the thermal diffusivity is the unknown parameter. We show how to infer the thermal diffusivity parameter when its prior distribution is lognormal or modeled by means of a space-dependent stationary lognormal random field. We use the Laplace method to provide approximated Gaussian posterior distributions for the thermal diffusivity. Expected information gains and predictive posterior densities for observable quantities are numerically estimated for different experimental setups.
Bayesian Inference for Linear Parabolic PDEs with Noisy Boundary Conditions
Ruggeri, Fabrizio
2015-01-07
In this work we develop a hierarchical Bayesian setting to infer unknown parameters in initial-boundary value problems (IBVPs) for one-dimensional linear parabolic partial differential equations. Noisy boundary data and known initial condition are assumed. We derive the likelihood function associated with the forward problem, given some measurements of the solution field subject to Gaussian noise. Such function is then analytically marginalized using the linearity of the equation. Gaussian priors have been assumed for the time-dependent Dirichlet boundary values. Our approach is applied to synthetic data for the one-dimensional heat equation model, where the thermal diffusivity is the unknown parameter. We show how to infer the thermal diffusivity parameter when its prior distribution is lognormal or modeled by means of a space-dependent stationary lognormal random field. We use the Laplace method to provide approximated Gaussian posterior distributions for the thermal diffusivity. Expected information gains and predictive posterior densities for observable quantities are numerically estimated for different experimental setups.
Mechanical design of a low cost parabolic solar dish concentrator
Directory of Open Access Journals (Sweden)
Hamza Hijazi
2016-03-01
Full Text Available The objective of this research was to design a low cost parabolic solar dish concentrator with small-to moderate size for direct electricity generation. Such model can be installed in rural areas which are not connected to governmental grid. Three diameters of the dish; 5, 10 and 20 m are investigated and the focal point to dish diameter ratio is set to be 0.3 in all studied cases. Special attention is given to the selection of the appropriate dimensions of the reflecting surfaces to be cut from the available sheets in the market aiming to reduce both cutting cost and sheets cost. The dimensions of the ribs and rings which support the reflecting surface are optimized in order to minimize the entire weight of the dish while providing the minimum possible total deflection and stresses in the beams. The study applies full stress analysis of the frame of the dish using Autodesk Inventor. The study recommends to use landscape orientation for the reflective facets and increase the ribs angle and the distance between the connecting rings. The methodology presented is robust and can be extended to larger dish diameters.
Slope Error Measurement Tool for Solar Parabolic Trough Collectors: Preprint
Energy Technology Data Exchange (ETDEWEB)
Stynes, J. K.; Ihas, B.
2012-04-01
The National Renewable Energy Laboratory (NREL) has developed an optical measurement tool for parabolic solar collectors that measures the combined errors due to absorber misalignment and reflector slope error. The combined absorber alignment and reflector slope errors are measured using a digital camera to photograph the reflected image of the absorber in the collector. Previous work using the image of the reflection of the absorber finds the reflector slope errors from the reflection of the absorber and an independent measurement of the absorber location. The accuracy of the reflector slope error measurement is thus dependent on the accuracy of the absorber location measurement. By measuring the combined reflector-absorber errors, the uncertainty in the absorber location measurement is eliminated. The related performance merit, the intercept factor, depends on the combined effects of the absorber alignment and reflector slope errors. Measuring the combined effect provides a simpler measurement and a more accurate input to the intercept factor estimate. The minimal equipment and setup required for this measurement technique make it ideal for field measurements.
Performance Simulation Comparison for Parabolic Trough Solar Collectors in China
Directory of Open Access Journals (Sweden)
Jinping Wang
2016-01-01
Full Text Available Parabolic trough systems are the most used concentrated solar power technology. The operating performance and optical efficiency of the parabolic trough solar collectors (PTCs are different in different regions and different seasons. To determine the optimum design and operation of the parabolic trough solar collector throughout the year, an accurate estimation of the daily performance is needed. In this study, a mathematical model for the optical efficiency of the parabolic trough solar collector was established and three typical regions of solar thermal utilization in China were selected. The performance characteristics of cosine effect, shadowing effect, end loss effect, and optical efficiency were calculated and simulated during a whole year in these three areas by using the mathematical model. The simulation results show that the optical efficiency of PTCs changes from 0.4 to 0.8 in a whole year. The highest optical efficiency of PTCs is in June and the lowest is in December. The optical efficiency of PTCs is mainly influenced by the solar incidence angle. The model is validated by comparing the test results in parabolic trough power plant, with relative error range of 1% to about 5%.
Fabrication, Designing & Performance Analysis of Solar Parabolic Trough
Directory of Open Access Journals (Sweden)
Mayur G. Tayade,
2014-07-01
Full Text Available A parabolic trough solar collector uses a parabolic cylinder to reflect and concentrate sun radiations towards a receiver tube located at the focus line of the parabolic cylinder. The receiver absorbs the incoming radiations and transforms them into thermal energy, the latter being transported and collected by a fluid medium circulating within the receiver tube.This method of concentrated solar collection has the advantage of high efficiency and low cost, and can be used either for thermal energy collection, for generating electricity or for both, This paper focused on the fabrication and designing of solar parabolic trough, The designing of trough is depend upon the following parameters : Aperture of the concentrator , Inner diameter of absorber tube, Outer diameter of absorber tube, Inner diameter of glass tube, Outer diameter of glass tube, Length of parabolic trough, Concentration ratio, Collector aperture area, Specular reflectivity of concentrator, Glass cover transitivity for solar radiation, Absorber tube emissivity/emissivity, Intercept factor, Emissivity of absorber tube surface and Emissivity of glass. The performance analysis will be based on the Experimental data collection and calculations with reference to: Thermal performance calculations, Overall loss coefficient and heat correlations. Heat transfer coefficient on the inside surface of the absorber tube and Heat transfer coefficient between the absorber tube and the Cover.
A Contribution for the Construction of Parabolic Mirrors
de Paula, L A N; Assis, A K T
2008-01-01
We present a new procedure for the construction of parabolic mirrors using low cost materials. We build a spinning system composed of nylon threads, fish hooks and a plastic bucket. We pour liquid plaster into the bucket and set it in constant rotational motion relative to the earth. A liquid substance assumes a parabolic profile when spinning at constant angular velocity relative to an inertial frame under the influence of an uniform vertical gravitational field. By keeping the bucket under rotation for a long time, the plaster solidifies into a parabolic format. We utilize this solidified plaster paraboloid as a model to construct a counter-mould of glass fibre and resin. Over this counter-mould it is placed stretched laminated foil and then it is poured thick plaster over it. In this way it is obtained a parabolic mirror made of laminated foil and plaster. Our only objective here is to present a new method for the construction of parabolic mirror using low cost materials. This allows further exploration of...
Willems, Sara M.; Wright, D.J.; Day, Felix R.; Trajanoska, Katerina; Joshi, P.K.; Morris, John A.; Matteini, Amy M.; Garton, Fleur C.; Grarup, Niels; Oskolkov, Nikolay; Thalamuthu, Anbupalam; Mangino, Massimo; Liu, Jun; Demirkan, Ayse; Lek, Monkol; Xu, Liwen; Wang, Guan; Oldmeadow, Christopher; Gaulton, Kyle J.; Lotta, Luca A.; Miyamoto-Mikami, Eri; Rivas, Manuel A.; White, Tom; Loh, Po Ru; Aadahl, Mette; Amin, Najaf; Attia, John R.; Austin, Krista; Benyamin, Beben; Brage, Søren; Cheng, Yu Ching; Ciȩszczyk, Paweł; Derave, Wim; Eriksson, Karl Fredrik; Eynon, Nir; Linneberg, Allan; Lucia, Alejandro; Massidda, Myosotis; Mitchell, Braxton D.; Miyachi, Motohiko; Murakami, Haruka; Padmanabhan, Sandosh; Pandey, Ashutosh; Papadimitriou, Ioannis; Rajpal, Deepak K.; Sale, Craig; Schnurr, Theresia M.; Sessa, Francesco; Shrine, Nick; Tobin, Martin D.; Varley, Ian; Wain, Louise V.; Wray, Naomi R.; Lindgren, Cecilia M.; MacArthur, Daniel G.; Waterworth, Dawn M.; McCarthy, Mark I.; Pedersen, Oluf; Khaw, Kay Tee; Kiel, Douglas P.; Pitsiladis, Yannis; Fuku, Noriyuki; Franks, Paul W.; North, Kathryn N.; Duijn, Van C.M.; Mather, Karen A.; Hansen, Torben; Hansson, Ola; Spector, Tim D.; Murabito, Joanne M.; Richards, J.B.; Rivadeneira, Fernando; Langenberg, Claudia; Perry, John R.B.; Wareham, Nick J.; Scott, Robert A.; Oei, Ling; Zheng, Hou Feng; Forgetta, Vincenzo; Leong, Aaron; Ahmad, Omar S.; Laurin, Charles; Mokry, Lauren E.; Ross, Stephanie; Elks, Cathy E.; Bowden, Jack; Warrington, Nicole M.; Murray, Anna; Ruth, Katherine S.; Tsilidis, Konstantinos K.; Medina-Gómez, Carolina; Estrada, Karol; Bis, Joshua C.; Chasman, Daniel I.; Demissie, Serkalem; Enneman, Anke W.; Hsu, Yi Hsiang; Ingvarsson, Thorvaldur; Kähönen, Mika; Kammerer, Candace; Lacroix, Andrea Z.; Li, Guo; Liu, Ching Ti; Liu, Yongmei; Lorentzon, Mattias; Mägi, Reedik; Mihailov, Evelin; Milani, Lili; Moayyeri, Alireza; Nielson, Carrie M.; Sham, Pack Chung; Siggeirsdotir, Kristin; Sigurdsson, Gunnar; Stefansson, Kari; Trompet, Stella; Thorleifsson, Gudmar; Vandenput, Liesbeth; Velde, Van Der Nathalie; Viikari, Jorma; Xiao, Su Mei; Zhao, Jing Hua; Evans, Daniel S.; Cummings, Steven R.; Cauley, Jane; Duncan, Emma L.; Groot, De Lisette C.P.G.M.; Esko, Tonu; Gudnason, Vilmundar; Harris, Tamara B.; Jackson, Rebecca D.; Jukema, J.W.; Ikram, Arfan M.A.; Karasik, David; Kaptoge, Stephen; Kung, Annie Wai Chee; Lehtimäki, Terho; Lyytikäinen, Leo Pekka; Lips, Paul; Luben, Robert; Metspalu, Andres; Meurs, van Joyce B.; Minster, Ryan L.; Orwoll, Erick; Oei, Edwin; Psaty, Bruce M.; Raitakari, Olli T.; Ralston, Stuart W.; Ridker, Paul M.; Robbins, John A.; Smith, Albert V.; Styrkarsdottir, Unnur; Tranah, Gregory J.; Thorstensdottir, Unnur; Uitterlinden, Andre G.; Zmuda, Joseph; Zillikens, M.C.; Ntzani, Evangelia E.; Evangelou, Evangelos; Ioannidis, John P.A.; Evans, David M.; Ohlsson, Claes
2017-01-01
Hand grip strength is a widely used proxy of muscular fitness, a marker of frailty, and predictor of a range of morbidities and all-cause mortality. To investigate the genetic determinants of variation in grip strength, we perform a large-scale genetic discovery analysis in a combined sample of
DEFF Research Database (Denmark)
Willems, Sara M.; Wright, Daniel J.; Day, Felix R.
2017-01-01
Hand grip strength is a widely used proxy of muscular fitness, a marker of frailty, and predictor of a range of morbidities and all-cause mortality. To investigate the genetic determinants of variation in grip strength, we perform a large-scale genetic discovery analysis in a combined sample of 1...
Design of shape memory alloy actuated intelligent parabolic antenna for space applications
Kalra, Sahil; Bhattacharya, Bishakh; Munjal, B. S.
2017-09-01
The deployment of large flexible antennas is becoming critical for space applications today. Such antenna systems can be reconfigured in space for variable antenna footprint, and hence can be utilized for signal transmission to different geographic locations. Due to quasi-static shape change requirements, coupled with the demand of large deflection, shape memory alloy (SMA) based actuators are uniquely suitable for this system. In this paper, we discuss the design and development of a reconfigurable parabolic antenna structure. The reflector skin of the antenna is vacuum formed using a metalized polycarbonate shell. Two different strategies are chosen for the antenna actuation. Initially, an SMA wire based offset network is formed on the back side of the reflector. A computational model is developed using equivalent coefficient of thermal expansion (ECTE) for the SMA wire. Subsequently, the interaction between the antenna and SMA wire is modeled as a constrained recovery system, using a 1D modified Brinson model. Joule effect based SMA phase transformation is considered for the relationship between input voltage and temperature at the SMA wire. The antenna is modeled using ABAQUS based finite element methodology. The deflection found through the computational model is compared with that measured in experiment. Subsequently, a point-wise actuation system is developed for higher deflection. For power-minimization, an auto-locking device is developed. The performance of the new configuration is compared with the offset-network configuration. It is envisaged that the study will provide a comprehensive procedure for the design of intelligent flexible structures especially suitable for space applications.
Interaction Potential between Parabolic Rotator and an Outside Particle
Directory of Open Access Journals (Sweden)
Dan Wang
2014-01-01
Full Text Available At micro/nanoscale, the interaction potential between parabolic rotator and a particle located outside the rotator is studied on the basis of the negative exponential pair potential 1/Rn between particles. Similar to two-dimensional curved surfaces, we confirm that the potential of the three-dimensional parabolic rotator and outside particle can also be expressed as a unified form of curvatures; that is, it can be written as the function of curvatures. Furthermore, we verify that the driving forces acting on the particle may be induced by the highly curved micro/nano-parabolic rotator. Curvatures and the gradient of curvatures are the essential elements forming the driving forces. Through the idealized numerical experiments, the accuracy of the curvature-based potential is preliminarily proved.
Design, Construction and Testing of a Parabolic Solar Steam Generator
Directory of Open Access Journals (Sweden)
Joshua FOLARANMI
2009-07-01
Full Text Available This paper reports the design, construction and testing of a parabolic dish solar steam generator. Using concentrating collector, heat from the sun is concentrated on a black absorber located at the focus point of the reflector in which water is heated to a very high temperature to form steam. It also describes the sun tracking system unit by manual tilting of the lever at the base of the parabolic dish to capture solar energy. The whole arrangement is mounted on a hinged frame supported with a slotted lever for tilting the parabolic dish reflector to different angles so that the sun is always directed to the collector at different period of the day. On the average sunny and cloud free days, the test results gave high temperature above 200°C.
First Middle East Aircraft Parabolic Flights for ISU Participant Experiments
Pletser, Vladimir; Frischauf, Norbert; Cohen, Dan; Foster, Matthew; Spannagel, Ruven; Szeszko, Adam; Laufer, Rene
2017-06-01
Aircraft parabolic flights are widely used throughout the world to create microgravity environment for scientific and technology research, experiment rehearsal for space missions, and for astronaut training before space flights. As part of the Space Studies Program 2016 of the International Space University summer session at the Technion - Israel Institute of Technology, Haifa, Israel, a series of aircraft parabolic flights were organized with a glider in support of departmental activities on `Artificial and Micro-gravity' within the Space Sciences Department. Five flights were organized with manoeuvres including several parabolas with 5 to 6 s of weightlessness, bank turns with acceleration up to 2 g and disorientation inducing manoeuvres. Four demonstration experiments and two experiments proposed by SSP16 participants were performed during the flights by on board operators. This paper reports on the microgravity experiments conducted during these parabolic flights, the first conducted in the Middle East for science and pedagogical experiments.
Kremer, Y; Léger, J-F; Lapole, R; Honnorat, N; Candela, Y; Dieudonné, S; Bourdieu, L
2008-07-07
Acousto-optic deflectors (AOD) are promising ultrafast scanners for non-linear microscopy. Their use has been limited until now by their small scanning range and by the spatial and temporal dispersions of the laser beam going through the deflectors. We show that the use of AOD of large aperture (13mm) compared to standard deflectors allows accessing much larger field of view while minimizing spatio-temporal distortions. An acousto-optic modulator (AOM) placed at distance of the AOD is used to compensate spatial and temporal dispersions. Fine tuning of the AOM-AOD setup using a frequency-resolved optical gating (GRENOUILLE) allows elimination of pulse front tilt whereas spatial chirp is minimized thanks to the large aperture AOD.
The development of a virtual database to provide on-line access to a large archive of clinical data.
Stevens, L. E.; Huff, S.M.; Haug, P. J.
1992-01-01
The archival database of the HELP Hospital Information System at LDS Hospital is too large to be stored on line. The archival data are important for clinical and research applications. Demountable disk packs have been used to store the archival database. This method of storage has four significant disadvantages. A virtual database was developed to overcome the limitations of this data-management scheme. This virtual database enables the transparent use of appropriate low-cost network-based st...
DEFF Research Database (Denmark)
Willems, Sara M; Wright, Daniel J.; Day, Felix R
2017-01-01
Hand grip strength is a widely used proxy of muscular fitness, a marker of frailty, and predictor of a range of morbidities and all-cause mortality. To investigate the genetic determinants of variation in grip strength, we perform a large-scale genetic discovery analysis in a combined sample of 195...... strength and the causal role of muscular strength in age-related morbidities and mortality....
Gomes-Pereira, José Nuno; Carmo, Vanda; Catarino, Diana; Jakobsen, Joachim; Alvarez, Helena; Aguilar, Ricardo; Hart, Justin; Giacomello, Eva; Menezes, Gui; Stefanni, Sergio; Colaço, Ana; Morato, Telmo; Santos, Ricardo S.; Tempera, Fernando; Porteiro, Filipe
2017-11-01
Many fish species are well-known obligatory inhabitants of shallow-water tropical coral reefs but such associations are difficult to study in deep-water environments. We address the association between two deep-sea fish with low mobility and large sessile invertebrates using a compilation of 20 years of unpublished in situ observations. Data were collected on Northeast Atlantic (NEA) island slopes and seamounts, from the Azores to the Canary Islands, comprising 127 new records of the circalittoral Labridae Lappanella fasciata and 15 of the upper bathyal Ophiididae Benthocometes robustus. Observations by divers, remote operated vehicles (ROV SP, Luso, Victor, Falcon Seaeye), towed vehicles (Greenpeace) and manned submersibles (LULA, Nautile) validated the species association to cold water corals (CWC) and large hydrozoans. L. fasciata occurred from lower infralittoral (41 m) throughout the circalittoral, down to the upper bathyal at 398 m depth. Smaller fishes (invertebrates (> 10 cm) occurring at biological information and dietary information reinforcing the trophic linkage between the CWC habitat and this predator. Gathered evidence renders CWC and hydroid gardens as Essential Fish Habitats for both species, being therefore sensitive to environmental and anthropogenic impacts on these Vulnerable Marine Ecosystems. The Mediterranean distribution of L. fasciata is extended to NEA seamounts and island slopes and the amphi-Atlantic distribution of B. robustus is bridged with molecular data support. Both species are expected to occur throughout the Macaronesia and Mediterranean island slopes and shallow seamounts on habitats with large sessile invertebrates.
The parabolic equation method for outdoor sound propagation
DEFF Research Database (Denmark)
Arranz, Marta Galindo
The parabolic equation method is a versatile tool for outdoor sound propagation. The present study has focused on the Cranck-Nicolson type Parabolic Equation method (CNPE). Three different applications of the CNPE method have been investigated. The first two applications study variations...... of the ground in a homogeneous atmosphere. Propagation of sound above a mixed impedance ground and up-slope sound propagation is investigated. In the third application the influence of the atmosphere is studied, characterized and implemented in the CNPE-model. The refraction of the sound due to the wind...
Focusing of Intense Laser via Parabolic Plasma Concave Surface
Zhou, Weimin; Gu, Yuqiu; Wu, Fengjuan; Zhang, Zhimeng; Shan, Lianqiang; Cao, Leifeng; Zhang, Baohan
2015-12-01
Since laser intensity plays an important role in laser plasma interactions, a method of increasing laser intensity - focusing of an intense laser via a parabolic plasma concave surface - is proposed and investigated by three-dimensional particle-in-cell simulations. The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude. Compared with the improvement via laser optics approaches, this scheme is much more economic and appropriate for most femtosecond laser facilities. supported by National Natural Science Foundation of China (Nos. 11174259, 11175165), and the Dual Hundred Foundation of China Academy of Engineering Physics
Small petal tools performance for parabolizing optical surfaces.
Ortiz-Lima, Carlos Manuel; Cordero-Dávila, Alberto; González-García, Jorge
2016-11-20
Small rigid petal tools, driven by a traditional polishing machine, were used to parabolize 20 mirrors 14 cm in diameter and 192 cm of curvature radius. Small rigid circular tools (SCTs), driven manually, were used to parabolize another 20 identical surfaces. A Ronchi test with a square grid was used to evaluate the performance of both techniques. If small rigid petal tools are used, the surface quality, the reproducibility in the production process, and the time spent required to generate the surfaces are markedly better than using SCTs.
Moduli of Parabolic Higgs Bundles and Atiyah Algebroids
DEFF Research Database (Denmark)
Logares, Marina; Martens, Johan
2010-01-01
In this paper we study the geometry of the moduli space of (non-strongly) parabolic Higgs bundles over a Riemann surface with marked points. We show that this space possesses a Poisson structure, extending the one on the dual of an Atiyah algebroid over the moduli space of parabolic vector bundles....... By considering the case of full flags, we get a Grothendieck–Springer resolution for all other flag types, in particular for the moduli spaces of twisted Higgs bundles, as studied by Markman and Bottacin and used in the recent work of Laumon–Ngô. We discuss the Hitchin system, and demonstrate that all...
Gilbert, Kenneth E
2015-01-01
The original formulation of the Green's function parabolic equation (GFPE) can have numerical accuracy problems for large normalized surface impedances. To solve the accuracy problem, an improved form of the GFPE has been developed. The improved GFPE formulation is similar to the original formulation, but it has the surface-wave pole "subtracted." The improved GFPE is shown to be accurate for surface impedances varying over 2 orders of magnitude, with the largest having a magnitude exceeding 1000. Also, the improved formulation is slightly faster than the original formulation because the surface-wave component does not have to be computed separately.
Blow-Up Analysis for a Quasilinear Degenerate Parabolic Equation with Strongly Nonlinear Source
Directory of Open Access Journals (Sweden)
Pan Zheng
2012-01-01
Full Text Available We investigate the blow-up properties of the positive solution of the Cauchy problem for a quasilinear degenerate parabolic equation with strongly nonlinear source ut=div(|∇um|p−2∇ul+uq, (x,t∈RN×(0,T, where N≥1, p>2 , and m, l, q>1, and give a secondary critical exponent on the decay asymptotic behavior of an initial value at infinity for the existence and nonexistence of global solutions of the Cauchy problem. Moreover, under some suitable conditions we prove single-point blow-up for a large class of radial decreasing solutions.
National Research Council Canada - National Science Library
Weatherly, Kirk
2000-01-01
This thesis examines two implementations of the parabolic equation approximation to the acoustic wave equation aimed at removing three errors inherent to the wide-angle parabolic equation (WAPE) model...
On the regularity of optimal control for a parabolic system of order 2m
Directory of Open Access Journals (Sweden)
Ornella Fiodo
1992-05-01
Full Text Available An optimal control problem for a parabolic operator of order 2m with the boundary conditions containing the control is considered. A regularity theorem for the parabolic problem and the regularity of the optimal control is proved.
Doubly Nonlinear Parabolic Systems In Inhomogeneous Musielak- Orlicz-Sobolev Spcaes
Directory of Open Access Journals (Sweden)
Ahmed Aberqi
2017-12-01
Full Text Available In this paper, we discuss the solvability of the nonlinear parabolic systems associated to the nonlinear parabolic equation: \\frac{\\partial b_{i}(x,u_{i}}{\\partial t} -div(a(x,t,u_{i},\
Hogg, Oliver T.; Huvenne, Veerle A. I.; Griffiths, Huw J.; Dorschel, Boris; Linse, Katrin
2016-10-01
Global biodiversity is in decline, with the marine environment experiencing significant and increasing anthropogenic pressures. In response marine protected areas (MPAs) have increasingly been adopted as the flagship approach to marine conservation, many covering enormous areas. At present, however, the lack of biological sampling makes prioritising which regions of the ocean to protect, especially over large spatial scales, particularly problematic. Here we present an interdisciplinary approach to marine landscape mapping at the sub-Antarctic island of South Georgia as an effective protocol for underpinning large-scale (105-106 km2) MPA designations. We have developed a new high-resolution (100 m) digital elevation model (DEM) of the region and integrated this DEM with bathymetry-derived parameters, modelled oceanographic data, and satellite primary productivity data. These interdisciplinary datasets were used to apply an objective statistical approach to hierarchically partition and map the benthic environment into physical habitats types. We assess the potential application of physical habitat classifications as proxies for biological structuring and the application of the landscape mapping for informing on marine spatial planning.
Energy Technology Data Exchange (ETDEWEB)
Bevelhimer, Mark S.; Deng, Z. Daniel; Scherelis, Constantin
2016-01-01
Underwater noise associated with the installation and operation of hydrokinetic turbines in rivers and tidal zones presents a potential environmental concern for fish and marine mammals. Comparing the spectral quality of sounds emitted by hydrokinetic turbines to natural and other anthropogenic sound sources is an initial step at understanding potential environmental impacts. Underwater recordings were obtained from passing vessels of different sizes and other underwater sound sources in both static and flowing waters. Static water measurements were taken in a lake with minimal background noise. Flowing water measurements were taken at a previously proposed deployment site for hydrokinetic turbines on the Mississippi River, where the sound of flowing water is included in background measurements. The size of vessels measured ranged from a small fishing boat with a 60 HP outboard motor to an 18-unit barge train being pushed upstream by tugboat. As expected, large vessels with large engines created the highest sound levels, and when compared to the sound created by an operating HK turbine were many times greater. A comparison of sound levels from the same sources at different distances using both spherical and cylindrical sound attenuation functions suggests that spherical model results more closely approximate observed values.
Zheng, Yiwen; Gliddon, Catherine M; Aitken, Phillip; Stiles, Lucy; Machado, Marie-Laure; Philoxene, Bruno; Denise, Pierre; Smith, Paul F; Besnard, Stephane
2017-07-27
Both parabolic flight, i.e. a condition of altered gravity, and loss of vestibular function, have been suggested to affect spatial learning and memory, which is known to be influenced by neurogenesis in the hippocampus. In this study we investigated whether short alternated micro- and hyper-gravity stimulations during parabolic flight and/or loss of vestibular function, would alter cell proliferation in the hippocampal dentate gyrus of rats, by measuring the number of bromodeoxyuridine (BrdU)-incorporated cells. Rats were randomly allocated to the following experimental groups: (1) sham transtympanic saline injection only (n=5); (2) bilateral vestibular deafferentation (BVD) by sodium arsanilate transtympanic injection only (n=5); (3) sham treatment and parabolic flight (n=5); (4) BVD and parabolic flight (n=6). Forty-two days following transtympanic injection, the animals were subjected to parabolic flight in an awake restrained condition after habituation. A modified Airbus A300 aircraft was flown on a parabolic path, creating 20s of 1.8G during both climbing and descending and 22s of 0G at the apex of each parabola. The no flight animals were subjected to the same housing for the same duration. Immediately after the parabolic flight or control ground condition, animals were injected with BrdU (300mg/kg, i.p). Twenty-four hs after BrdU injection, rats were sacrificed. BrdU immunolabelling was performed and the number of BrdU+ve cells in the dentate gyrus of the hippocampus was quantified using a modified fractionator method. BVD caused a large and significant reduction in the number of BrdU-positive cells compared to sham animals (P≤0.0001); however, flight and all interactions were non-significant. These results indicate that BVD significantly decreased cell proliferation irrespective of the short exposure to altered/modified gravity. Copyright © 2017 Elsevier B.V. All rights reserved.
Technical Note: Universal Specific Energy Curve For Parabolic ...
African Journals Online (AJOL)
From the general relationship between specific energy and flow depth for all open channels, the specific relationship for parabolic open channels was obtained here. By introducing suitable scaling parameters of the same length dimensions as the specific energy and flow depth, a rela-tionship was obtained between a ...
Linking hyperbolic and parabolic p.d.e.’s.
Zwart, Heiko J.; Le Gorrec, Yann; Maschke, B.M.
2011-01-01
In this article we show that from the existence and uniqueness of solutions to a hyperbolic partial differential equation (p.d.e.) existence and uniqueness of parabolic and other hyperbolic p.d.e.’s can be derived. Among others, we show that starting with the (undamped) wave equation we obtain
Improved Green's function parabolic equation method for atmospheric sound propagation
Salomons, E.M.
1998-01-01
The numerical implementation of the Green's function parabolic equation (GFPE) method for atmospheric sound propagation is discussed. Four types of numerical errors are distinguished: (i) errors in the forward Fourier transform; (ii) errors in the inverse Fourier transform; (iii) errors in the
Development and preliminary testing of a parabolic trough solar ...
African Journals Online (AJOL)
It depicts that employing a suitable design, selection of time of heating and proper focusing of the reflected rays to the focal spot region, solar radiation can efficiently be utilized for water heating in a tropical environment. This work presents a parabolic trough solar water heater as a suitable renewable energy technology for ...
Viscosity solutions of fully nonlinear functional parabolic PDE
Directory of Open Access Journals (Sweden)
Liu Wei-an
2005-01-01
Full Text Available By the technique of coupled solutions, the notion of viscosity solutions is extended to fully nonlinear retarded parabolic equations. Such equations involve many models arising from optimal control theory, economy and finance, biology, and so forth. The comparison principle is shown. Then the existence and uniqueness are established by the fixed point theory.
Lateral migration of a capsule in a parabolic flow.
Nix, S; Imai, Y; Ishikawa, T
2016-07-26
Red blood cells migrate to the center of the blood vessel in a process called axial migration, while other blood cells, such as white blood cells and platelets, are disproportionately found near the blood vessel wall. However, much is still unknown concerning the lateral migration of cells in the blood; the specific effect of hydrodynamic factors such as a wall or a shear gradient is still unclear. In this study, we investigate the lateral migration of a capsule using the boundary integral method, in order to compute exactly an infinite computational domain for an unbounded parabolic flow and a semi-infinite computational domain for a near-wall parabolic flow in the limit of Stokes flow. We show that the capsule lift velocity in an unbounded parabolic flow is linear with respect to the shear gradient, while the lift velocity in a near-wall parabolic flow is dependent on the distance to the wall. Then, using these relations, we give an estimation of the relative effect of the shear gradient as a function of channel width and distance between the capsule and the wall. This estimation can be used to determine cases in which the effect of the shear gradient or wall can be neglected; for example, the formation of the cell-free layer in blood vessels is determined to be unaffected by the magnitude of the shear gradient. Copyright © 2015 Elsevier Ltd. All rights reserved.
A prototype parabolic trough solar concentrators for steam production
African Journals Online (AJOL)
Three parabolic trough solar concentrators (PTSCs) of dimensions: -aperture width of 1.2 m, Collector length of 5.8 m and aperture area of 6.95 m2 were investigated. The absorber pipe was a copper tube which carried water as the heat transfer fluid, were designed, fabricated, characterized and their efficiencies compared ...
Performance simulation of parabolic trough solar collector using two ...
African Journals Online (AJOL)
The Parabolic trough solar collector is considered as one of the most proven, mature and commercial concentrating solar systems implemented in arid and semi-arid regions for energy production. It focuses sunlight onto a solar receiver by using mirrors and is finally converted to a useful thermal energy by means of a heat ...
On some perturbation techniques for quasi-linear parabolic equations
Directory of Open Access Journals (Sweden)
Igor Malyshev
1990-01-01
Full Text Available We study a nonhomogeneous quasi-linear parabolic equation and introduce a method that allows us to find the solution of a nonlinear boundary value problem in explicit form. This task is accomplished by perturbing the original equation with a source function, which is then found as a solution of some nonlinear operator equation.
Real parabolic vector bundles over a real curve
Indian Academy of Sciences (India)
weights are integral multiples of 1/N, and the category of real -equivariant vector bundles on (Y,σY ). ... The notion of parabolic vector bundles over a compact Riemann surface was introduced by Seshadri [4] and their .... stable. If F is a direct sum of stable vector bundles having the same slope, then F is called polystable.
Non-symmetrical separated flow along the parabolic wing
Gaifullin, A. M.; Zhvick, V. V.
2017-10-01
Inviscid incompressible separated flow along the parabolic wing is explored. The partition is placed in the symmetry plane. The problem is considered without an assumption of flow symmetry. Self-similar solution is constructed. Both symmetrical and non-symmetrical solutions are observed. Fields of self-similar trajectories and stability are analysed.
Multipoint problem with for factorized parabolic operator with variable coefficients
Directory of Open Access Journals (Sweden)
I. R. Tymkiv
2011-12-01
Full Text Available The correctness of the problem with multipoints conditions with respect time-variable and conditions of the Dirichlet by Petrovski linear parabolic equation with variable coefficients in a limited cylindrical domen. The conditions of existence and uniqueness of the classical solution of the problem are established. The metrical theorems on evalution from below of small denominators of the problem are proved.
Parabolic equations with VMO coefficients in Morrey spaces
Directory of Open Access Journals (Sweden)
Lubomira G. Softova
2001-07-01
Full Text Available Global regularity in Morrey spaces is derived for the regular oblique derivative for linear uniformly parabolic operators. The principal coefficients of the operator are supposed to be discontinuous, belonging to Sarason's class of functions with vanishing mean oscillation (VMO.
Strong solvability for a class of nonlinear parabolic equations
Directory of Open Access Journals (Sweden)
Lubomira Softova
1997-05-01
Full Text Available Existence of strong solutions to Cauchy-Dirichlet problem for nonlinear parabolic equation is established. The nonlinear operator is prescribed by Carathéodory's function which satisfies an ellipticity condition due to S. Campanato. The main results are reached through Aleksandrov-Bakel'man-Pucci type maximum principle and topological fixed point theorem.
Integral representations for computing real parabolic cylinder functions
A. Gil (Amparo); J. Segura (Javier); N.M. Temme (Nico)
2004-01-01
textabstractIntegral representations are derived for the parabolic cylinder functions U(a,x), V(a,x) and W(a,x) and their derivatives. The new integrals will be used in numerical algorithms based on quadrature. They follow from contour integrals in the complex plane, by using methods from asymptotic
Integral representations for computing real parabolic cylinder functions
A. Gil (Amparo); J. Segura (Javier); N.M. Temme (Nico)
2005-01-01
htmlabstractIntegral representations are derived for the parabolic cylinder functions U(a,x), V(a,x) and W(a,x) and their derivatives. The new integrals will be used in numerical algorithms based on quadrature. They follow from contour integrals in the complex plane, by using methods from asymptotic
Numerical and asymptotic aspects of parabolic cylinder functions
N.M. Temme (Nico)
2000-01-01
textabstractSeveral uniform asymptotics expansions of the Weber parabolic cylinder functions are considered, one group in terms of elementary functions, another group in terms of Airy functions. Starting point for the discussion are asymptotic expansions given earlier by F.W.J. Olver. Some of his
Pevnick, Joshua M; Fuller, Garth; Duncan, Ray; Spiegel, Brennan M R
2016-01-01
Personal fitness trackers (PFT) have substantial potential to improve healthcare. To quantify and characterize early adopters who shared their PFT data with providers. We used bivariate statistics and logistic regression to compare patients who shared any PFT data vs. patients who did not. A patient portal was used to invite 79,953 registered portal users to share their data. Of 66,105 users included in our analysis, 499 (0.8%) uploaded data during an initial 37-day study period. Bivariate and regression analysis showed that early adopters were more likely than non-adopters to be younger, male, white, health system employees, and to have higher BMIs. Neither comorbidities nor utilization predicted adoption. Our results demonstrate that patients had little intrinsic desire to share PFT data with their providers, and suggest that patients most at risk for poor health outcomes are least likely to share PFT data. Marketing, incentives, and/or cultural change may be needed to induce such data-sharing.
Cook, Natalie; Maganti, Manjula; Dobriyal, Aditi; Sheinis, Michal; Wei, Alice C; Ringash, Jolie; Krzyzanowska, Monika K
2016-07-01
Little is known about how electronic mail (e-mail) is currently used in oncology practice to facilitate patient care. The objective of our study was to understand the current e-mail practices and preferences of patients and physicians in a large comprehensive cancer center. Separate cross-sectional surveys were administered to patients and physicians (staff physicians and clinical fellows) at the Princess Margaret Cancer Centre. Logistic regression was used to identify factors associated with current e-mail use. Record review was performed to assess the impact of e-mail communication on care. The survey was completed by 833 patients. E-mail contact with a member of the health care team was reported by 41% of respondents. The team members contacted included administrative assistants (52%), nurses (45%), specialist physicians (36%), and family physicians (18%). Patient factors associated with a higher likelihood of e-mail contact with the health care team included younger age, higher education, higher income, enrollment in a clinical trial, and receipt of multiple treatments. Eighty percent of physicians (n = 63 of 79) reported previous contact with a patient via e-mail. Physician factors associated with a greater likelihood of e-mail contact with patients included older age, more senior clinical position, and higher patient volume. Nine hundred sixty-two patient records were reviewed, with e-mail correspondence documented in only 9% of cases. E-mail is commonly used for patient care but is poorly documented. The use of e-mail in this setting can be developed with appropriate guidance; however, there may be concerns about widening the gap between certain groups of patients. Copyright © 2016 by American Society of Clinical Oncology.
Pletser, Vladimir; Rouquette, Sebastien; Friedrich, Ulrike; Clervoy, Jean-Francois; Gharib, Thierry; Gai, Frederic; Mora, Christophe
2015-09-01
Aircraft parabolic flights repetitively provide up to 23 s of reduced gravity during ballistic flight manoeuvres. Parabolic flights are used to conduct short microgravity investigations in Physical and Life Sciences and in Technology, to test instrumentation prior to space flights and to train astronauts before a space mission. The use of parabolic flights is complementary to other microgravity carriers (drop towers, sounding rockets), and preparatory to manned space missions on board the International Space Station and other manned spacecraft, such as Shenzhou and the Chinese Space Station CSS. The European Space Agency (ESA), the 'Centre National d'Etudes Spatiales' (CNES, French Space Agency) and the 'Deutsches Zentrum für Luft- und Raumfahrt e.V.' (DLR, the German Aerospace Centre) have used the Airbus A300 ZERO-G for research experiments in microgravity, and at Moon and Mars gravity levels, from 1997 until October 2014. The French company Novespace, a subsidiary of CNES, based in Bordeaux, France, is in charge of the organisation of Airbus A300 ZERO-G flights. A total of 104 parabolic flight campaigns have been organised by ESA, CNES and DLR since 1997, including 38 ESA, 34 CNES and 23 DLR microgravity campaigns, two Joint European ESA-CNES-DLR Partial-g Parabolic Flight Campaigns, and seven ESA Student campaigns. After 17 years of good and loyal services, this European workhorse for microgravity research in parabolic flights has been retired. The successor aircraft, the Airbus A310 ZERO-G, is being prepared for a first ESA-CNES-DLR cooperative campaign in Spring 2015. This paper looks back over 17 years of microgravity research in parabolic flights with the A300 ZERO-G, and introduces the new A310 ZERO-G that will be used from 2015 onwards.
Milner, Rachel; Parrish, Jonathan; Wright, Adrienne; Gnarpe, Judy; Keenan, Louanne
2015-01-01
In a large-enrollment, introductory biochemistry course for nonmajors, the authors provide students with formative feedback through practice questions in PDF format. Recently, they investigated possible benefits of providing the practice questions via an online game (Brainspan). Participants were randomly assigned to either the online game group…
Rhon, Daniel; Greenlee, Tina; Fritz, Julie
2017-07-14
To describe the use of manipulative treatment for shoulder and spine conditions among various provider types. Retrospective observational cohort. Single military hospital. Consecutive sample of patients (N=7566) seeking care for an initial spine or shoulder condition from January 1 to December 31, 2009. Manipulative treatment (eg, manual therapy, spinal and joint manipulation). Manipulation treatment was identified with procedure billing codes in the medical records. Spine and shoulder conditions were identified by using the International Classification of Diseases, 9th Revision codes. All data were abstracted from the Department of Defense Military Health System Management and Analysis Tool. Of 7566 total patients seeking care, 2014 (26.6%) received manipulative treatment at least once, and 1870 of those received this treatment in a military facility (24.7%). Manipulative treatment was used most often for thoracic conditions and least often for shoulder conditions (50.8% and 24.2% of all patients). There was a total of 6706 unique medical visits with a manipulative treatment procedure (average of 3.3 manipulative treatment procedure visits per patient). Manipulative treatment utilization rates for shoulder and spine conditions ranged from 26.6% to 50.2%. Chiropractors used manipulation the most and physical therapists the least. Published by Elsevier Inc.
ESA Parabolic Flight, Drop Tower and Centrifuge Opportunities for University Students
Callens, Natacha; Ventura-Traveset, Javier; Zornoza Garcia-Andrade, Eduardo; Gomez-Calero, Carlos; van Loon, Jack J. W. A.; Pletser, Vladimir; Kufner, Ewald; Krause, Jutta; Lindner, Robert; Gai, Frederic; Eigenbrod, Christian
The European Space Agency (ESA) Education Office was established in 1998 with the purpose of motivating young people to study science, engineering and technology subjects and to ensure a qualified workforce for ESA and the European space sector in the future. To this end the ESA Education Office is supporting several hands-on activities including small student satellites and student experiments on sounding rockets, high altitude balloons as well as microgravity and hypergravity platforms. This paper is intended to introduce three new ESA Education Office hands-on activities called "Fly Your Thesis!", "Drop Your Thesis!" and "Spin Your Thesis!". These activities give re-spectively access to aircraft parabolic flight, drop tower and centrifuge campaigns to European students. These educational programmes offer university students the unique opportunity to design, build, and eventually perform, in microgravity or hypergravity, a scientific or techno-logical experiment which is linked to their syllabus. During the "Fly Your Thesis!" campaigns, the students accompany their experiments onboard the A300 Zero-G aircraft, operated by the company Novespace, based in Bordeaux, France, for a series of three flights of 30 parabolas each, with each parabola providing about 20s of microgravity [1]. "Drop Your Thesis!" campaigns are held in the ZARM Drop Tower, in Bremen, Germany. The installation delivers 4.74s of microgravity in dropping mode and 9.3s in the catapulting mode [2]. Research topics such as fluid physics, fundamental physics, combustion, biology, material sciences, heat transfer, astrophysics, chemistry or biochemistry can greatly benefit from using microgravity platforms. "Spin Your Thesis!" campaigns take place in the Large Diameter Centrifuge (LDC) facility, at ESTEC, Noordwijk, in the Netherlands. This facility offers an acceleration from 1 to 20 times Earth's gravity [3]. The use of hypergravity allows completing the scientific picture of how gravity has an
Directory of Open Access Journals (Sweden)
David Viktor Dylus
2016-01-01
Full Text Available Abstract Background The evolutionary mechanisms involved in shaping complex gene regulatory networks (GRN that encode for morphologically similar structures in distantly related animals remain elusive. In this context, echinoderm larval skeletons found in brittle stars and sea urchins provide an ideal system. Here, we characterize for the first time the development of the larval skeleton in the ophiuroid Amphiura filiformis and compare it systematically with its counterpart in sea urchin. Results We show that ophiuroids and euechinoids, that split at least 480 Million years ago (Mya, have remarkable similarities in tempo and mode of skeletal development. Despite morphological and ontological similarities, our high-resolution study of the dynamics of genetic regulatory states in A. filiformis highlights numerous differences in the architecture of their underlying GRNs. Importantly, the A.filiformis pplx, the closest gene to the sea urchin double negative gate (DNG repressor pmar1, fails to drive the skeletogenic program in sea urchin, showing important evolutionary differences in protein function. hesC, the second repressor of the DNG, is co-expressed with most of the genes that are repressed in sea urchin, indicating the absence of direct repression of tbr, ets1/2, and delta in A. filiformis. Furthermore, the absence of expression in later stages of brittle star skeleton development of key regulatory genes, such as foxb and dri, shows significantly different regulatory states. Conclusion Our data fill up an important gap in the picture of larval mesoderm in echinoderms and allows us to explore the evolutionary implications relative to the recently established phylogeny of echinoderm classes. In light of recent studies on other echinoderms, our data highlight a high evolutionary plasticity of the same nodes throughout evolution of echinoderm skeletogenesis. Finally, gene duplication, protein function diversification, and cis-regulatory element
Energy Technology Data Exchange (ETDEWEB)
Ajona, J.I.; Alberdi, J.; Gamero, E.; Blanco, J.
1992-07-01
In the local control, the sun position related to the trough collector is measured by two photo-resistors. The provided electronic signal is then compared with reference levels in order to get a set of B logical signals which form a byte. This byte and the commands issued by a programmable controller are connected to the inputs of o P.R.O.M. memory which is programmed with the logical equations of the control system. The memory output lines give the control command of the parabolic trough collector motor. (Author)
Critical Blow-Up and Global Existence for Discrete Nonlinear p-Laplacian Parabolic Equations
Directory of Open Access Journals (Sweden)
Soon-Yeong Chung
2014-01-01
Full Text Available The goal of this paper is to investigate the blow-up and the global existence of the solutions to the discrete p-Laplacian parabolic equation utx,t=Δp,wux,t+λux,tp-2ux,t, x,t∈S×0,∞, ux,t=0, x,t∈∂S×0,∞, ux,0=u0, depending on the parameters p>1 and λ>0. Besides, we provide several types of the comparison principles to this equation, which play a key role in the proof of the main theorems. In addition, we finally give some numerical examples which exploit the main results.
Christoforou, Cleopatra
2017-12-10
We extend the relative entropy identity to the class of hyperbolic-parabolic systems whose hyperbolic part is symmetrizable. The resulting identity is useful to provide measure valued weak versus strong uniqueness theorems for the hyperbolic problem. Also, it yields a convergence result in the zero-viscosity limit to smooth solutions in an Lp framework. The relative entropy identity is also developed for the system of gas dynamics for viscous and heat conducting gases, and for the system of thermoviscoelasticity with viscosity and heat-conduction. Existing differences between the example and the general hyperbolic theory are underlined.
Directory of Open Access Journals (Sweden)
E. Tohidi
2014-01-01
Full Text Available The problem of solving several types of one-dimensional parabolic partial differential equations (PDEs subject to the given initial and nonlocal boundary conditions is considered. The main idea is based on direct collocation and transforming the considered PDEs into their associated algebraic equations. After approximating the solution in the Legendre matrix form, we use Legendre operational matrix of differentiation for representing the mentioned algebraic equations clearly. Three numerical illustrations are provided to show the accuracy of the presented scheme. High accurate results with respect to the Bernstein Tau technique and Sinc collocation method confirm this accuracy.
Design philosophy and construction of a high concentration compound parabolic concentrator
CSIR Research Space (South Africa)
Roos, TH
2010-09-01
Full Text Available stream_source_info Roos_2010.pdf.txt stream_content_type text/plain stream_size 19653 Content-Encoding UTF-8 stream_name Roos_2010.pdf.txt Content-Type text/plain; charset=UTF-8 THE DESIGN PHILOSOPHY AND CONSTRUCTION... and actual efficiency will be determined using a hemispherical cavity calorimeter. Keywords: CPC, compound parabolic concentrator, sandwich 1. Introduction A 25m2 target-aligned research heliostat has been developed at CSIR [1] to provide the concentrated...
Harmonization of standards for parabolic trough collector testing in solar thermal power plants
Sallaberry, Fabienne; Valenzuela, Loreto; Palacin, Luis G.; Leon, Javier; Fischer, Stephan; Bohren, Andreas
2017-06-01
The technology of parabolic trough collectors (PTC) is used widely in concentrating Solar Power (CSP) plants worldwide. However this type of large-size collectors cannot be officially tested by an accredited laboratory and certified by an accredited certification body so far, as there is no standard adapted to its particularity, and the current published standard for solar thermal collectors are not completely applicable to them. Recently some standardization committees have been working on this technology. This paper aims to give a summary of the standardized testing methodology of large-size PTC for CSP plants, giving the physical model chosen for modeling the thermal performance of the collector in the new revision of standard ISO 9806 and the points still to be improved in the standard draft IEC 62862-3-2. In this paper, a summary of the testing validation performed on one parabolic trough collector installed in one of the test facilities at the Plataforma Solar de Almería (PSA) with this new model is also presented.
Energy Technology Data Exchange (ETDEWEB)
Madessa, Habtamu Bayera
2012-07-01
tracking system that could be integrated with a small scale concentrating parabolic dish. This includes the design and testing of a polar mounted electronic-based analogue and digital type sun tracking system. A Photovoltaic (Pv) based direct sun tracking system that actuates the tracking motor based on the shading effect was also developed and tested. As described in Paper 5, the direct type of sun tracking system was found to be a very simple system which provided a sufficient tracking accuracy. Paper 6 describes ray tracing program simulations to study the optical performance of concentrating solar reflections and absorption systems. The program was further extended to study the possibility of transporting concentrated solar rays from the focus of a parabolic dish to an application area via a mirror channel guide (Paper 7). Finally, an overall test was conducted to investigate the performance of prototype for the small scale parabolic dish solar concentrator with rock bed as a heat storage unit, with the results presented in Paper 8. They show that the small scale system can capture and store solar thermal energy. As a heat transfer medium, air requires careful design and construction of the receiver, circulating fan and heat transport pipe. The small scale system yields modest storage temperatures. A scaled system with a higher concentration ratio is necessary in order to achieve higher temperatures. (Author)
Laser propagation and compton scattering in parabolic plasma channel
Dongguo, L; Yokoya, K; Hirose, T
2003-01-01
A Gaussian laser beam propagating in a parabolic plasma channel is discussed in this paper. For a weak laser, plasma density perturbation induced by interaction between the laser field and plasma is very small, the refractive index can be assumed to be constant with respect to time variable. For a parabolic plasma channel, through the static propagation equation, we obtain an analytical solution of the profile function of the Gaussian laser beam for an unmatched case and give the general condition for the matched case. As the laser intensity increases, an effect due to strong laser fields is included. We discuss how to design and select the distribution of plasma density for a certain experiment in which a plasma channel is utilized to guide a laser beam. The number of scattered photons (X-rays) generated through Compton backscattering in a plasma channel is discussed. (author)
'Parabolic' trapped modes and steered Dirac cones in platonic crystals.
McPhedran, R C; Movchan, A B; Movchan, N V; Brun, M; Smith, M J A
2015-05-08
This paper discusses the properties of flexural waves governed by the biharmonic operator, and propagating in a thin plate pinned at doubly periodic sets of points. The emphases are on the design of dispersion surfaces having the Dirac cone topology, and on the related topic of trapped modes in plates for a finite set (cluster) of pinned points. The Dirac cone topologies we exhibit have at least two cones touching at a point in the reciprocal lattice, augmented by another band passing through the point. We show that these Dirac cones can be steered along symmetry lines in the Brillouin zone by varying the aspect ratio of rectangular lattices of pins, and that, as the cones are moved, the involved band surfaces tilt. We link Dirac points with a parabolic profile in their neighbourhood, and the characteristic of this parabolic profile decides the direction of propagation of the trapped mode in finite clusters.
Irrigation market for solar thermal parabolic dish systems
Habib-Agahi, H.; Jones, S. C.
1981-01-01
The potential size of the onfarm-pumped irrigation market for solar thermal parabolic dish systems in seven high-insolation states is estimated. The study is restricted to the displacement of three specific fuels: gasoline, diesel and natural gas. The model was developed to estimate the optimal number of parabolic dish modules per farm based on the minimum cost mix of conventional and solar thermal energy required to meet irrigation needs. The study concludes that the potential market size for onfarm-pumped irrigation applications ranges from 101,000 modules when a 14 percent real discount rate is assumed to 220,000 modules when the real discount rate drops to 8 percent. Arizona, Kansas, Nebraska, New Mexico and Texas account for 98 percent of the total demand for this application, with the natural gas replacement market accounting for the largest segment (71 percent) of the total market.
Experimental and simulation studies of parabolic trough collector design for obtaining solar energy
Directory of Open Access Journals (Sweden)
Syed Ameen Murtuza
2017-12-01
Full Text Available Concentrated solar power has great potential for large scale renewable energy sources, and is currently an eye catching one for its utilization with wide area of improvement. Especially, parabolic trough solar collectors (PTSCs are gaining popularity due to their increased efficiency as compared to photovoltaics. In this work, an effort has been made to evaluate the performance of a designed 5-m length PTSC model. Heat collecting element was made of stainless steel with water as working fluid. The authentication of the proposed model is justified based on the results obtained on a yearly scale with respect to average inlet and outlet temperatures, surface temperatures and thermal efficiency for the climatic conditions of Ramanagaram. It was observed that March to May yielded better outlet temperatures ranging from 93âÂ°C to 103âÂ°C. Experiments were carried out at different flow rates of 0.4âLPM, 0.8âLPM and 1.2âLPM and corresponding Reynolds number was calculated. It was seen that February to May gave good surface and outlet temperatures as compared with other months while the liquid flow is laminar. Simulation studies were carried out using ANSYS software on receiver tube to ensure the robustness and design effectiveness under static loading conditions. Keywords: Parabolic trough solar collector, Receiver tube, Solar thermal, Static structural analysis
A stability analysis for a semilinear parabolic partial differential equation
Chafee, N.
1973-01-01
The parabolic partial differential equation considered is u sub t = u sub xx + f(u), where minus infinity x plus infinity and o t plus infinity. Under suitable hypotheses pertaining to f, a class of initial data is exhibited: phi(x), minus infinity x plus infinity, for which the corresponding solutions u(x,t) appraoch zero as t approaches the limit of plus infinity. This convergence is uniform with respect to x on any compact subinterval of the real axis.
A parameter identification problem involving a nonlinear parabolic differential equation
Ressel, Rudolf Andreas
2012-01-01
This work contributes to the analysis of a parameter identification task for a certain type of parabolic PDE. The first part of this work proposes an analytical approach for the parameter identification problem. The PDE is a nonlinear reaction-diffusion equation modeling the gene expression of the embryogenesis of Drosophila melanogaster. The problem is formulated in an evolution equation setting, suitable solution and parameter spaces are introduced for that purpose. We utilize novel results...
Adaptive discontinuous Galerkin methods for nonlinear parabolic problems
Metcalfe, Stephen Arthur
2015-01-01
This work is devoted to the study of a posteriori error estimation and adaptivity in parabolic problems with a particular focus on spatial discontinuous Galerkin (dG) discretisations. We begin by deriving an a posteriori error estimator for a linear non-stationary convection-diffusion problem that is discretised with a backward Euler dG method. An adaptive algorithm is then proposed to utilise the error estimator. The effectiveness of both the error estimator and the proposed algorithm is sho...
Long term behaviour of singularly perturbed parabolic degenerated equation
Faye, Ibrahima; Frenod, Emmanuel; Seck, Diaraf
2011-01-01
In this paper we consider models for short-term, mean-term and long-term morphodynamics of dunes and megariples. We give an existence and uniqueness result for long term dynamics of dunes. This result is based on a time-space periodic solution existence result for degenerated parabolic equation that we set out. Finally the mean-term and long-term models are homogenized.
Regularity problem for quasilinear elliptic and parabolic systems
Koshelev, Alexander
1995-01-01
The smoothness of solutions for quasilinear systems is one of the most important problems in modern mathematical physics. This book deals with regular or strong solutions for general quasilinear second-order elliptic and parabolic systems. Applications in solid mechanics, hydrodynamics, elasticity and plasticity are described. The results presented are based on two main ideas: the universal iterative method, and explicit, sometimes sharp, coercivity estimates in weighted spaces. Readers are assumed to have a standard background in analysis and PDEs.
Clear-Air Propagation Modeling using Parabolic Equation Method
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V. Kvicera
2003-12-01
Full Text Available Propagation of radio waves under clear-air conditions is affected bythe distribution of atmospheric refractivity between the transmitterand the receiver. The measurement of refractivity was carried out onthe TV Tower Prague to access evolution of a refractivity profile. Inthis paper, the parabolic equation method is used in modelingpropagation of microwaves when using the measured data. This paperbriefly describes the method and shows some practical results ofsimulation of microwave propagation using real vertical profiles ofatmospheric refractivity.
Homogenization of a nonlinear degenerate parabolic differential equation
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A. K. Nandakumaran
2001-03-01
Full Text Available In this article, we study the homogenization of the nonlinear degenerate parabolic equation $$ partial_t b({x /varepsilon},u_varepsilon - mathop{ m div} a({x /varepsilon},{t /varepsilon}, u_varepsilon,abla u_varepsilon=f(x,t, $$ with mixed boundary conditions(Neumann and Dirichlet and obtain the limit equation as $varepsilon o 0$. We also prove corrector results to improve the weak convergence of $abla u_varepsilon$ to strong convergence.
Discontinuous Galerkin Finite Element Method for Parabolic Problems
Kaneko, Hideaki; Bey, Kim S.; Hou, Gene J. W.
2004-01-01
In this paper, we develop a time and its corresponding spatial discretization scheme, based upon the assumption of a certain weak singularity of parallel ut(t) parallel Lz(omega) = parallel ut parallel2, for the discontinuous Galerkin finite element method for one-dimensional parabolic problems. Optimal convergence rates in both time and spatial variables are obtained. A discussion of automatic time-step control method is also included.
Parabolic-trough solar collectors and their applications
Energy Technology Data Exchange (ETDEWEB)
Fernandez-Garcia, A.; Zarza, E.; Valenzuela, L. [CIEMAT-Plataforma Solar de Almeria, Ctra. Senes, km. 4, Tabernas (Almeria) 04200 (Spain); Perez, M. [Departamento de Fisica Aplicada, Universidad de Almeria, Almeria 04120 (Spain)
2010-09-15
This paper presents an overview of the parabolic-trough collectors that have been built and marketed during the past century, as well as the prototypes currently under development. It also presents a survey of systems which could incorporate this type of concentrating solar system to supply thermal energy up to 400 C, especially steam power cycles for electricity generation, including examples of each application. (author)
Stability and Boundedness of Solutions to Nonautonomous Parabolic Integrodifferential Equations
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Michael Gil'
2016-01-01
Full Text Available We consider a class of linear nonautonomous parabolic integrodifferential equations. We will assume that the coefficients are slowly varying in time. Conditions for the boundedness and stability of solutions to the considered equations are suggested. Our results are based on a combined usage of the recent norm estimates for operator functions and theory of equations on the tensor product of Hilbert spaces.
Null controllability for linear parabolic cascade systems with interior degeneracy
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Idriss Boutaayamou
2016-11-01
Full Text Available We study the null controllability problem for linear degenerate parabolic systems with one control force through Carleman estimates for the associated adjoint problem. The novelty of this article is that for the first time it is considered a problem with an interior degeneracy and a control set that only requires to contain an interval lying on one side of the degeneracy points. The obtained result improves and complements a number of earlier works. As a consequence, observability inequalities are established.
Estimates of parabolic cylinder functions on the real axis
Pokrovski, Alexis
2005-01-01
We estimate simple combination of the parabolic cylinder functions and their derivatives. These estimates are important for the spectral analysis of non-analytically perturbed quantum harmonic oscillator. The estimates are valid in rather complicated domains and refine there the classical result of Olver. We determine the part of the real x-axis, which is within the domains of the estimates. This requires a detailed study of the image of the real x-axis in the standard quasiclassical variable.
Parabolic similariton Yb-fiber laser with triangular pulse evolution
Wang, Sijia; Wang, Lei
2016-04-01
We propose a novel mode-locked fiber laser design which features a passive nonlinear triangular pulse formation and self-similar parabolic pulse amplification intra cavity. Attribute to the nonlinear reshaping progress in the passive fiber, a triangular-profiled pulse with negative-chirp is generated and paved the way for rapid and efficient self-similar parabolic evolution in a following short-length high-gain fiber. In the meanwhile, the accompanied significantly compressed narrow spectrum from this passive nonlinear reshaping also gives the promise of pulse stabilization and gain-shaping robustness without strong filtering. The resulting short average intra-cavity pulse duration, low amplified spontaneous emission (ASE) and low intra-cavity power loss are essential for the low-noise operation. Simulations predict this modelocked fiber laser allows for high-energy ultra-short transform-limited pulse generation exceeding the gain bandwidth. The output pulse has a de-chirped duration (full-width at half maximum, FWHM) of 27 fs. In addition to the ultrafast laser applications, the proposed fiber laser scheme can support low-noise parabolic and triangular pulse trains at the same time, which are also attractive in optical pulse shaping, all-optical signal processing and high-speed communication applications.
Energy Technology Data Exchange (ETDEWEB)
None
1975-06-01
This report presents the results of a quick, six-week technical and economic evaluation of the compound parabolic concentrator (CPC) solar collector. The purpose of this effort was to provide an initial phase of a goals study that is directed toward recommending relative priorities for development of the compound parabolic concentrator concept. The findings of this study are of a very preliminary nature. Conclusions based on study findings at this depth should be considered preliminary and subject to revision and review in later phases.
Energy Technology Data Exchange (ETDEWEB)
Price, H.; Kearney, D.
1999-01-31
Technology roadmapping is a needs-driven technology planning process to help identify, select, and develop technology alternatives to satisfy a set of market needs. The DOE's Office of Power Technologies' Concentrating Solar Power (CSP) Program recently sponsored a technology roadmapping workshop for parabolic trough technology. The workshop was attended by an impressive cross section of industry and research experts. The goals of the workshop were to evaluate the market potential for trough power projects, develop a better understanding of the current state of the technology, and to develop a conceptual plan for advancing the state of parabolic trough technology. This report documents and extends the roadmap that was conceptually developed during the workshop.
DEFF Research Database (Denmark)
Nozaki, Daijiro; Avdoshenko, Stanislav M.; Sevincli, Haldun
2013-01-01
Recently the interest in quantum interference (QI) phenomena in molecular devices (molecular junctions) has been growing due to the unique features observed in the transmission spectra. In order to design single molecular devices exploiting QI effects as desired, it is necessary to provide simple...... to predict the appearance of quantum interference, Fano resonances or anti- resonances, and its position in the conductance spectrum by introducing a simple graphical representation (parabolic model). Using it we can easily visualize the relation between the key electronic parameters and the positions...... of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. We also demonstrate Fano and anti-resonance in T-shaped molecular junctions using a simple tight-binding model. This parabolic model enables one to infer on-site energies of T-shaped molecules...
Memon, Sajid
2012-01-01
In this article, a posteriori error estimates are derived for mixed finite element Galerkin approximations to second order linear parabolic initial and boundary value problems. Using mixed elliptic reconstructions, a posteriori error estimates in L∞(L2)- and L2(L2)-norms for the solution as well as its flux are proved for the semidiscrete scheme. Finally, based on a backward Euler method, a completely discrete scheme is analyzed and a posteriori error bounds are derived, which improves upon earlier results on a posteriori estimates of mixed finite element approximations to parabolic problems. Results of numerical experiments verifying the efficiency of the estimators have also been provided. © 2012 Society for Industrial and Applied Mathematics.
Perez-Poch, Antoni; González, Daniel Ventura; López, David
2016-12-01
We report on different research and educational activities related to parabolic flights conducted in Barcelona since 2008. We use a CAP10B single-engine aerobatic aircraft flying out of Sabadell Airport and operating in visual flight conditions providing up to 8 seconds of hypogravity for each parabola. Aside from biomedical experiments being conducted, different student teams have flown in parabolic flights in the framework of the international contest `Barcelona Zero-G Challenge', and have published their results in relevant symposiums and scientific journals. The platform can certainly be a good testbed for a proof-of-concept before accessing other microgravity platforms, and has proved to be excellent for motivational student campaigns.
Chong, Kok-Keong; Yew, Tiong-Keat; Wong, Chee-Woon; Tan, Ming-Hui; Tan, Woei-Chong; Lai, An-Chow; Lim, Boon-Han; Lau, Sing-Liong; Rahman, Faidz Abdul
2015-04-01
Solar concentrating device plays an important role by making use of optical technology in the design, which can be either reflector or lens to deliver high flux of sunlight onto the Concentrator Photovoltaic (CPV) module receiver ranging from hundreds to thousand suns. To be more competitive compared with fossil fuel, the current CPV systems using Fresnel lens and Parabolic dish as solar concentrator that are widely deployed in United States, Australia and Europe are facing great challenge to produce uniformly focused sunlight on the solar cells as to reduce the cost of electrical power generation. The concept of non-imaging optics is not new, but it has not fully explored by the researchers over the world especially in solving the problem of high concentration solar energy, which application is only limited to be a secondary focusing device or low concentration device using Compound Parabolic Concentrator. With the current advancement in the computer processing power, we has successfully invented the non-imaging dish concentrator (NIDC) using numerical simulation method to replace the current parabolic dish as primary focusing device with high solar concentration ratio (more than 400 suns) and large collective area (from 25 to 125 m2). In this paper, we disclose our research and development on dense array CPV system based on non-imaging optics. The geometry of the NIDC is determined using a special computational method. In addition, an array of secondary concentrators, namely crossed compound parabolic concentrators, is also proposed to further focus the concentrated sunlight by the NIDC onto active area of solar cells of the concentrator photovoltaic receiver. The invention maximizes the absorption of concentrated sunlight for the electric power generation system.
Free vibration of functionally graded parabolic and circular panels with general boundary conditions
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Zhang Hong
2017-01-01
Full Text Available The purpose of this content is to investigate the free vibration of functionally graded parabolic and circular panels with general boundary conditions by using the Fourier-Ritz method. The first-order shear deformation theory is adopted to consider the effects of the transverse shear and rotary inertia of the panel structures. The functionally graded panel structures consist of ceramic and metal which are assumed to vary continuously through the thickness according to the power-law distribution, and two types of power-law distributions are considered for the ceramic volume fraction. The improved Fourier series method is applied to construct the new admissible function of the panels to surmount the weakness of the relevant discontinuities with the original displacement and its derivatives at the boundaries while using the traditional Fourier series method. The boundary spring technique is adopted to simulate the general boundary condition. The unknown coefficients appearing in the admissible function are determined by using the Ritz procedure based on the energy functional of the panels. The numerical results show the present method has good convergence, reliability and accuracy. Some new results for functionally graded parabolic and circular panels with different material distributions and boundary conditions are provided, which may serve as benchmark solutions.
Performance Analysis of Fractional-Order PID Controller for a Parabolic Distributed Solar Collector
Elmetennani, Shahrazed
2017-09-01
This paper studies the performance of a fractional-order proportional integral derivative (FOPID) controller designed for parabolic distributed solar collectors. The control problem addressed in concentrated solar collectors aims at forcing the produced heat to follow a desired reference despite the unevenly varying solar irradiance. In addition to the unpredictable variations of the energy source, the parabolic solar collectors are subject to inhomogeneous distributed efficiency parameters affecting the heat production. The FOPID controller is well known for its simplicity with better tuning flexibility along with robustness with respect to disturbances. Thus, we propose a control strategy based on FOPID to achieve the control objectives. First, the FOPID controller is designed based on a linear approximate model describing the system dynamics under nominal working conditions. Then, the FOPID gains and differentiation orders are optimally tuned in order to fulfill the robustness design specifications by solving a nonlinear optimization problem. Numerical simulations are carried out to evaluate the performance of the proposed FOPID controller. A comparison to the robust integer order PID is also provided. Robustness tests are performed for the nominal model to show the effectiveness of the FOPID. Furthermore, the proposed FOPID is numerically tested to control the distributed solar collector under real working conditions.
Directory of Open Access Journals (Sweden)
Xiaoyan Liu
2015-01-01
Full Text Available A multitude of the researches focus on the factors of the thermal efficiency of a parabolic trough solar collector, that is, the optical-thermal efficiency. However, it is limited to a single or double factors for available system. The aim of this paper is to investigate the multifactors effect on the system’s efficiency in cold climate region. Taking climatic performance into account, an average outlet temperature of LS-2 collector has been simulated successfully by coupling SolTrace software with CFD software. Effects of different factors on instantaneous efficiency have been determined by orthogonal experiment and single factor experiment. After that, the influence degree of different factors on the collector instantaneous efficiency is obtained clearly. The results show that the order of effect extent for average maximal deviation of each factor is inlet temperature, solar radiation intensity, diameter, flow rate, condensation area, pipe length, and ambient temperature. The encouraging results will provide a reference for the exploitation and utilization of parabolic trough solar collector in cold climate region.
Parabolic Flight Evaluation of Bacterial Adhesion on Multiple Antimicrobial Surface Treatments
Birmele, Michele
2011-01-01
This report describes the development of a test method and the evaluation of the effectiveness of antimicrobial technologies in reduced gravity based on parabolic flight experiments. Microbial growth is a common occurrence on fully immersed wetted surfaces in spacecraft environmental control and life support systems despite the use of chemical and/or physical \\disinfection. Many materials and surface treatments with antimicrobial properties are commercially available but none have been vetted for spaceflight applications. Herein a test method is explained that included ground and reduced gravity parabolic flight experiments with a standard microorganism recovered from spacecraft, Pseudomonas aeruginosa, added at a concentration of 1 x 10(exp 5) cells per milliliter (mL) onto challenge material coupon surfaces. Several experimental materials were observed to slightly reduce microbial attachment in reduced gravity flight experiments, but none were capable of eliminating all challenge bacteria. Lunar gravity had an increased antimicrobial effect in 28 out of 36 test coupons compared to microgravity when provided otherwise identical conditions for growth, suggesting trace .amounts of gravity may be required for maximum antimicrobial performance. Bacterial cells exposed to variable gravity had more than twice as ,much intracellular adenosine triphosphate (ATP) when compared to control cells exposed only to Earth gravity due to a short duration response to environmental stress. An ATP luminescence assay was the method most amenable to development of an in-flight microbial monitoring assay
Simulation analysis of position error of parabolic trough concentrator mirror installation
Tian, Guo-liang; Yan, Bi-xi; Dong, Mingli; Wang, Jun; Sun, Peng
2015-02-01
The research showed the simulation of position error when assembling a reflective mirror of parabolic trough concentrator. The shape of a reflective mirror is like a parabolic cylinder model, relying on the back of the four-point mounted on a special setup, making it unable to move. Therefore, it is of great importance of the machining precision of special bracket. We need to analyze the influence of reflective mirror`s intercept factor in order to guide the processing precision. It is assumed that each reflective mirror is rigid, we have calculated the intercept factor of reflector with mounting points' random error of different standard deviation, comparing the simulating results with TRACEPRO. As a sequence, we can approve the feasibility of the algorithm, and give the effect of different random errors on the light-gathering efficiency. On the basis, we provide the machining accuracy of bracket. The simulation results show that when the mounting points' standard deviation of position error is less than 0.5 mm, the intercept factor of receiver has reached upwards of 92% with 60 mm diameter for receiver, which can satisfy the design requirements.
Water Use in Parabolic Trough Power Plants: Summary Results from WorleyParsons' Analyses
Energy Technology Data Exchange (ETDEWEB)
Turchi, C. S.; Wagner, M. J.; Kutscher, C. F.
2010-12-01
The National Renewable Energy Laboratory (NREL) contracted with WorleyParsons Group, Inc. to examine the effect of switching from evaporative cooling to alternative cooling systems on a nominal 100-MW parabolic trough concentrating solar power (CSP) plant. WorleyParsons analyzed 13 different cases spanning three different geographic locations (Daggett, California; Las Vegas, Nevada; and Alamosa, Colorado) to assess the performance, cost, and water use impacts of switching from wet to dry or hybrid cooling systems. NREL developed matching cases in its Solar Advisor Model (SAM) for each scenario to allow for hourly modeling and provide a comparison to the WorleyParsons results.Our findings indicate that switching from 100% wet to 100% dry cooling will result in levelized cost of electricity (LCOE) increases of approximately 3% to 8% for parabolic trough plants throughout most of the southwestern United States. In cooler, high-altitude areas like Colorado's San Luis Valley, WorleyParsons estimated the increase at only 2.5%, while SAM predicted a 4.4% difference. In all cases, the transition to dry cooling will reduce water consumption by over 90%. Utility time-of-delivery (TOD) schedules had similar impacts for wet- and dry-cooled plants, suggesting that TOD schedules have a relatively minor effect on the dry-cooling penalty.
Dupraz, K.; Cassou, K.; Martens, A.; Zomer, F.
2015-10-01
The ABCD matrix for parabolic reflectors is derived for any incident angles. It is used in numerical studies of four-mirror cavities composed of two flat and two parabolic mirrors. Constraints related to laser beam injection efficiency, optical stability, cavity-mode, beam-waist size and high stacking power are satisfied. A dedicated alignment procedure leading to stigmatic cavity-modes is employed to overcome issues related to the optical alignment of parabolic reflectors.
On canonical quasi-geodesic mappings of recurrent-parabolic spaces
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Ірина Миколаївна Курбатова
2018-01-01
Full Text Available Studying of the entered earlier quasi-geodesic mappings of recurrent parabolic spaces continues. The express class of such mappings - canonical quasi-geodesic mappings is allocated. Geometrical objects, invariant under considered mappings are constructed. Metrics of the recurrent parabolic spaces admitting canonical quasi-geodesic mappings on the flat space are found. The recurrent parabolic spaces with vector fields of particular type admitting canonical quasi-geodesic mappings are indicated.
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Wen-ku Shi
2016-01-01
Full Text Available The composite stiffness of parabolic leaf springs with variable stiffness is difficult to calculate using traditional integral equations. Numerical integration or FEA may be used but will require computer-aided software and long calculation times. An efficient method for calculating the composite stiffness of parabolic leaf springs with variable stiffness is developed and evaluated to reduce the complexity of calculation and shorten the calculation time. A simplified model for double-leaf springs with variable stiffness is built, and a composite stiffness calculation method for the model is derived using displacement superposition and material deformation continuity. The proposed method can be applied on triple-leaf and multileaf springs. The accuracy of the calculation method is verified by the rig test and FEA analysis. Finally, several parameters that should be considered during the design process of springs are discussed. The rig test and FEA analytical results indicate that the calculated results are acceptable. The proposed method can provide guidance for the design and production of parabolic leaf springs with variable stiffness. The composite stiffness of the leaf spring can be calculated quickly and accurately when the basic parameters of the leaf spring are known.
Error Analysis for Discontinuous Galerkin Method for Parabolic Problems
Kaneko, Hideaki
2004-01-01
In the proposal, the following three objectives are stated: (1) A p-version of the discontinuous Galerkin method for a one dimensional parabolic problem will be established. It should be recalled that the h-version in space was used for the discontinuous Galerkin method. An a priori error estimate as well as a posteriori estimate of this p-finite element discontinuous Galerkin method will be given. (2) The parameter alpha that describes the behavior double vertical line u(sub t)(t) double vertical line 2 was computed exactly. This was made feasible because of the explicitly specified initial condition. For practical heat transfer problems, the initial condition may have to be approximated. Also, if the parabolic problem is proposed on a multi-dimensional region, the parameter alpha, for most cases, would be difficult to compute exactly even in the case that the initial condition is known exactly. The second objective of this proposed research is to establish a method to estimate this parameter. This will be done by computing two discontinuous Galerkin approximate solutions at two different time steps starting from the initial time and use them to derive alpha. (3) The third objective is to consider the heat transfer problem over a two dimensional thin plate. The technique developed by Vogelius and Babuska will be used to establish a discontinuous Galerkin method in which the p-element will be used for through thickness approximation. This h-p finite element approach, that results in a dimensional reduction method, was used for elliptic problems, but the application appears new for the parabolic problem. The dimension reduction method will be discussed together with the time discretization method.
Design and Optimization of Elliptical Cavity Tube Receivers in the Parabolic Trough Solar Collector
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Fei Cao
2017-01-01
Full Text Available The nonfragile cavity receiver is of high significance to the solar parabolic trough collector (PTC. In the present study, light distributions in the cavity under different tracking error angles and PTC configurations are analyzed. A new elliptical cavity geometry is proposed and analyzed. It is obtained from this study that light distribution on the tube receiver is asymmetrical when tracking error occurs. On increasing the tracking error angle, more lights are sheltered by the cavity outer surface. The PTC focal distance has negative correlation with the cavity open length, whereas the PTC concentration ratio has positive correlation with the cavity open length. Increasing the tracking error angle and increasing the PTC focal distance would both decrease the cavity blackness. Introducing a flat plate reflector at the elliptical cavity open inlet can largely increase the cavity darkness.
A comparative study of the parabolized Navier-Stokes code using various grid-generation techniques
Kaul, U. K.; Chaussee, D. S.
1985-01-01
The parabolized Navier-Stokes (PNS) equations are used to calculate the flow-field characteristics about the hypersonic research aircraft X-24C. A comparison of the results obtained using elliptic, hyperbolic and algebraic grid generators is presented. The outer bow shock is treated as a sharp discontinuity, and the discontinuities within the shock layer are captured. Surface pressures and heat-transfer results at angles of attack of 6 deg and 20 deg, obtained using the three grid generators, are compared. The PNS equations are marched downstream over the body in both Cartesian and cylindrical base coordinate systems, and the results are compared. A robust marching procedure is demonstrated by successfully using large marching-step sizes with the implicit shock fitting procedure. A correlation is found between the marching-step size, Reynolds number and the angle of attack at fixed values of smoothing and stability coefficients for the marching scheme.
Simulation of continuously deforming parabolic problems by Galerkin finite-elements method
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Yahia S. Halabi
1986-01-01
Full Text Available A general numerical finite element scheme is described for parabolic problems with phase change wherein the elements of the domain are allowed to deform continuously. The scheme is based on the Galerkin approximation in space, and finite difference approximation for the time derivatives. The numerical scheme is applied to the two-phase Stefan problems associated with the melting and solidification of a substance. Basic functions based on Hermite polynomials are used to allow exact specification of flux-latent heat balance conditions at the phase boundary. Numerical results obtained by this scheme indicates that the method is stable and produces an accurate solutions for the heat conduction problems with phase change; even when large time steps used. The method is quite general and applicable for a variety of problems involving transition zones and deforming regions, and can be applied for one multidimensional problems.
Current and Future Costs for Parabolic Trough and Power Tower Systems in the US Market: Preprint
Energy Technology Data Exchange (ETDEWEB)
Turchi, C.; Mehos, M.; Ho, C. K.; Kolb, G. J.
2010-10-01
NREL's Solar Advisor Model (SAM) is employed to estimate the current and future costs for parabolic trough and molten salt power towers in the US market. Future troughs are assumed to achieve higher field temperatures via the successful deployment of low melting-point, molten-salt heat transfer fluids by 2015-2020. Similarly, it is assumed that molten salt power towers are successfully deployed at 100MW scale over the same time period, increasing to 200MW by 2025. The levelized cost of electricity for both technologies is predicted to drop below 11 cents/kWh (assuming a 10% investment tax credit and other financial inputs outlined in the paper), making the technologies competitive in the marketplace as benchmarked by the California MPR. Both technologies can be deployed with large amounts of thermal energy storage, yielding capacity factors as high as 65% while maintaining an optimum LCOE.
Harnack's Inequality for Degenerate and Singular Parabolic Equations
DiBenedetto, Emmanuele; Vespri, Vincenzo
2012-01-01
Degenerate and singular parabolic equations have been the subject of extensive research for the last 25 years. Despite important achievements, the issue of the Harnack inequality for non-negative solutions to these equations, both of p-Laplacian and porous medium type, while raised by several authors, has remained basically open. Recently considerable progress has been made on this issue, to the point that, except for the singular sub-critical range, both for the p-laplacian and the porous medium equations, the theory is reasonably complete. It seemed therefore timely to trace a comprehensive
Marching grid generation using parabolic partial differential equations
Nakamura, S.
1982-01-01
The feasibility of using parabolic partial differential equations for grid generation is examined. Source terms in the form of a linear interpolation between the current grid and the outer boundary are used in generating a grid for a two-dimensional airfoil flow. Grid generation equations are derived by assuming that grid spacings are locally nonuniform on the computational domain. The grid spacing control method is described in detail, and the local orthogonality of the grid lines is discussed. An O-mesh and an H-mesh generated by the described method are shown.
Asymptotic Behavior for a Class of Nonclassical Parabolic Equations
Yanjun Zhang; Qiaozhen Ma
2013-01-01
This paper is devoted to the qualitative analysis of a class of nonclassical parabolic equations ut-εΔut-ωΔu+f(u)=g(x) with critical nonlinearity, where ε∈[0,1] and ω>0 are two parameters. Firstly, we establish some uniform decay estimates for the solutions of the problem for g(x)∈H-1(Ω), which are independent of the parameter ε. Secondly, some uniformly (with respect to ε∈[0,1]) asymptotic regularity about the solutions has been established for g(x)∈L2(Ω), which shows that the solutions are ...
A mixed semilinear parabolic problem from combustion theory
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Claudia Lederman
2001-01-01
Full Text Available We prove existence, uniqueness, and regularity of the solution to a mixed initial boundary-value problem. The equation is semilinear uniformly parabolic with principal part in divergence form, in a non-cylindrical space-time domain. Here we extend our results in cite{LVWmix} to a more general domain. As in cite{LVWmix}, we assume only mild regularity on the coefficients, on the non-cylindrical part of the lateral boundary (where the Dirichlet data are given, and on the Dirichlet data.
Analytic semigroups and optimal regularity in parabolic problems
Lunardi, Alessandra
2012-01-01
The book shows how the abstract methods of analytic semigroups and evolution equations in Banach spaces can be fruitfully applied to the study of parabolic problems. Particular attention is paid to optimal regularity results in linear equations. Furthermore, these results are used to study several other problems, especially fully nonlinear ones. Owing to the new unified approach chosen, known theorems are presented from a novel perspective and new results are derived. The book is self-contained. It is addressed to PhD students and researchers interested in abstract evolution equations and in p
Limits of femtosecond fiber amplification by parabolic pre-shaping
Fu, Walter; Tang, Yuxing; McComb, Timothy S.; Lowder, Tyson L.; Wise, Frank W.
2017-03-01
We explore parabolic pre-shaping as a means of generating and amplifying ultrashort pulses. We develop a theoretical framework for modeling the technique and use its conclusions to design a femtosecond fiber amplifier. Starting from 9 ps pulses, we obtain 4.3 $\\mu$J, nearly transform-limited pulses 275 fs in duration, simultaneously achieving over 40 dB gain and 33-fold compression. Finally, we show that this amplification scheme is limited by Raman scattering, and outline a method by which the pulse duration and energy may be further improved and tailored for a given application.
Theoretical Study of the Compound Parabolic Trough Solar Collector
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Dr. Subhi S. Mahammed
2012-06-01
Full Text Available Theoretical design of compound parabolic trough solar collector (CPC without tracking is presented in this work. The thermal efficiency is obtained by using FORTRAN 90 program. The thermal efficiency is between (60-67% at mass flow rate between (0.02-0.03 kg/s at concentration ratio of (3.8 without need to tracking system.The total and diffused radiation is calculated for Tikrit city by using theoretical equations. Good agreement between present work and the previous work.
ON A PARABOLIC FREE BOUNDARY EQUATION MODELING PRICE FORMATION
MARKOWICH, P. A.
2009-10-01
We discuss existence and uniqueness of solutions for a one-dimensional parabolic evolution equation with a free boundary. This problem was introduced by Lasry and Lions as description of the dynamical formation of the price of a trading good. Short time existence and uniqueness is established by a contraction argument. Then we discuss the issue of global-in-time-extension of the local solution which is closely related to the regularity of the free boundary. We also present numerical results. © 2009 World Scientific Publishing Company.
H-infinity control of switched linear parabolic systems
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Leping Bao
2014-06-01
Full Text Available The $H_{\\infty}$ control problem of a class of switched linear parabolic systems is considered. By applying the multiple Lyapunov function method and the average dwell time scheme, sufficient conditions for exponential stability and the $H_{\\infty}$ control synthesis are established in terms of LMIs and a family of switching signals. The advantage in this work lies in the fact that sufficient conditions completely depend on the system parameters and the system can be analyzed by using numerical softwares. At the end of the paper, an example is given to illustrate the obtained result.
Integral representations for computing real parabolic cylinder functions
Gil, Amparo; Segura, Javier; Temme, Nico
2004-01-01
htmlabstractIntegral representations are derived for the parabolic cylinder functions U(a,x), V(a,x) and W(a,x) and their derivatives. The new integrals will be used in numerical algorithms based on quadrature. They follow from contour integrals in the complex plane, by using methods from asymptotic analysis (saddle point and steepest descent methods), and are stable starting points for evaluating the functions U(a,x), V(a,x) and W(a,x) and their derivatives by quadrature rules. In particular...
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Barbara Castelnuovo
Full Text Available INTRODUCTION: Starting in June 2010 the Infectious Diseases Institute (IDI clinic (a large urban HIV out-patient facility switched to provider-based Electronic Medical Records (EMR from paper EMR entered in the database by data-entry clerks. Standardized clinics forms were eliminated but providers still fill free text clinical notes in physical patients' files. The objective of this study was to compare the rate of errors in the database before and after the introduction of the provider-based EMR. METHODS AND FINDINGS: Data in the database pre and post provider-based EMR was compared with the information in the patients' files and classified as correct, incorrect, and missing. We calculated the proportion of incorrect, missing and total error for key variables (toxicities, opportunistic infections, reasons for treatment change and interruption. Proportions of total errors were compared using chi-square test. A survey of the users of the EMR was also conducted. We compared data from 2,382 visits (from 100 individuals of a retrospective validation conducted in 2007 with 34,957 visits (from 10,920 individuals of a prospective validation conducted in April-August 2011. The total proportion of errors decreased from 66.5% in 2007 to 2.1% in 2011 for opportunistic infections, from 51.9% to 3.5% for ART toxicity, from 82.8% to 12.5% for reasons for ART interruption and from 94.1% to 0.9% for reasons for ART switch (all P<0.0001. The survey showed that 83% of the providers agreed that provider-based EMR led to improvement of clinical care, 80% reported improved access to patients' records, and 80% appreciated the automation of providers' tasks. CONCLUSIONS: The introduction of provider-based EMR improved the quality of data collected with a significant reduction in missing and incorrect information. The majority of providers and clients expressed satisfaction with the new system. We recommend the use of provider-based EMR in large HIV programs in Sub
Cooper, Jennifer L.
2003-10-01
There is a need for a method to predict the attenuation of sound over a varied terrain and for realistic weather conditions. Parabolic equation based propagation codes can deal successfully with a sound speed that is a function of height (as could be caused by wind or temperature gradients) as well as varying ground heights and impedances. The ability to predict the received sound levels for a set of digitized terrain and sound speed data is desired. The accuracy of the Green's function parabolic equation (GFPE) has already been confirmed for propagation over flat ground with a slowly varying sound speed profile and/or with atmospheric turbulence. The approach here will be to compare to a benchmark solution for each different kind of terrain (i.e. flat, slope, step, barrier) with constant sound speed to verify the numeric code and to define the limits of accuracy in the GFPE for these situations. The GFPE is based on a one-way wave equation, so the numerical model will not be able to accurately predict the pressure behind multiple barriers or for other situations in which backward reflections can affect the received pressure. We will define the additional limits to the applicability of this model based on many comparisons with analytical solutions for propagation beyond barriers with constant sound speed. The sloping terrain will be treated as a series of stairsteps---a digitized ground height. Buildings and steps will be merely larger stairsteps. Although the GFPE has already been documented, as well as wide angle parabolic equations (PEs) and PEs using conformal mapping or similar rudimentary stair-stepping terrain maps, a PE that works with large discontinuities has not been documented, nor has there been work on a propagation model over complicated terrain profiles (in the past most work has been done in underwater acoustics for oceans with a sloping bottom condition but no variation in the slope was presented). The main emphasis here will be on the assumptions
Optical properties of Dirac electrons in a parabolic well.
Kim, S C; Lee, J W; Yang, S-R Eric
2013-09-01
A single electron transitor may be fabricated using qunatum dots. A good model for the confinement potential of a quantum dot is a parabolic well. Here we consider such a parabolic dot made of graphene. Recently, we found counter intuitively that resonant quasi-boundstates of both positive and negative energies exist in the energy spectrum. The presence of resonant quasi-boundstates of negative energies is a unique property of massless Dirac fermions. As magnetic field B gets smaller the energy width of these states become broader and for sufficiently weak value of B resonant quasi-bound states disappear into a quasi-continuum. In the limit of small B resonant and nonresonant states transform into discrete anomalous states with a narrow probability density peak inside the well and another broad peak under the potential barrier. In this paper we compute the optical strength between resonant quasi-bound states as a function of B, and investigate how the signature of resonant quasi-bound states of Dirac electrons may appear in optical measurements.
A quasi-linear parabolic system of chemotaxis
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available We consider a quasi-linear parabolic system with respect to unknown functions u and v on a bounded domain of n -dimensional Euclidean space. We assume that the diffusion coefficient of u is a positive smooth function A ( u , and that the diffusion coefficient of v is a positive constant. If A ( u is a positive constant, the system is referred to as so-called Keller-Segel system. In the case where the domain is a bounded domain of two-dimensional Euclidean space, it is shown that some solutions to Keller-Segel system blow up in finite time. In three and more dimensional cases, it is shown that solutions to so-called Nagai system blow up in finite time. Nagai system is introduced by Nagai. The diffusion coefficients of Nagai system are positive constants. In this paper, we describe that solutions to the quasi-linear parabolic system exist globally in time, if the positive function A ( u rapidly increases with respect to u .
Parabolic starlike mappings of the unit ball $B^n$
Directory of Open Access Journals (Sweden)
Samira Rahrovi
2016-02-01
Full Text Available Let $f$ be a locally univalent function on the unit disk $U$. We consider the normalized extensions of $f$ to the Euclidean unit ball $B^nsubseteqmathbb{C}^n$ given by$$Phi_{n,gamma}(f(z=left(f(z_1,(f'(z_1^gammahat{z}right,$$ where $gammain[0,1/2]$, $z=(z_1,hat{z}in B^n$ and$$Psi_{n,beta}(f(z=left(f(z_1,(frac{f(z_1}{z_1}^betahat{z}right,$$in which $betain[0,1]$, $f(z_1neq 0$ and $z=(z_1,hat{z}inB^n$. In the case $gamma=1/2$, the function $Phi_{n,gamma}(f$ reduces to the well known Roper-Suffridge extension operator. By using different methods, we prove that if $f$ is parabolic starlike mapping on $U$ then $Phi_{n,gamma}(f$ and $Psi_{n,beta}(f$ are parabolic starlike mappings on $B^n$.
Exergetic analysis of parabolic trough solar thermal power plants
Petrakopoulou, F.; Ruperez, B.; San Miguel, G.
2014-12-01
A very important component to achieve sustainable development in the energy sector is the improvement of energy efficiency of widely applied thermodynamic processes. Evaluation and optimization methods of energy processes play a crucial role in fulfilling this goal. A suitable method for the evaluation and optimization of energy conversion systems has been proven to be the exergetic analysis. In this work, two parabolic trough solar thermal power plants are simulated in detail using commercial software, and they are further analysed and compared using an exergetic analysis. The first plant uses a thermal fluid to produce the steam required in a steam generator, while the second one produces the steam directly in the solar field. The analysis involves the evaluation of the individual components of the power plants, as well as the performance evaluation of the overall structures. The main goal is to detect thermodynamic inefficiencies of the two different configurations and propose measures to minimize those. We find that the two examined plants have similar main sources of exergy destruction: the solar field (parabolic trough solar collectors), followed by the steam generator. This reveals the importance of an optimal design of these particular components, which could reduce inefficiencies present in the system. The differences in the exergy destruction and exergetic efficiencies of individual components of the two plants are analyzed in detail based on comparable operational conditions.
Thermal and optical efficiency investigation of a parabolic trough collector
Directory of Open Access Journals (Sweden)
C. Tzivanidis
2015-09-01
Full Text Available Solar energy utilization is a promising Renewable Energy source for covering a variety of energy needs of our society. This study presents the most well-known solar concentrating system, the parabolic trough collector, which is operating efficiently in high temperatures. The simulation tool of this analysis is the commercial software Solidworks which simulates complicated problems with an easy way using the finite elements method. A small parabolic trough collector model is designed and simulated for different operating conditions. The goal of this study is to predict the efficiency of this model and to analyze the heat transfer phenomena that take place. The efficiency curve is compared to a one dimensional numerical model in order to make a simple validation. Moreover, the temperature distribution in the absorber and inside the tube is presented while the heat flux distribution in the outer surface of the absorber is given. The heat convection coefficient inside the tube is calculated and compared with the theoretical one according to the literature. Also the angle efficiency modifier is calculated in order to predict the thermal and optical efficiency for different operating conditions. The final results show that the PTC model performs efficiently and all the calculations are validated.
Thermal analysis of a compound parabolic concentrator for refrigeration applications
Energy Technology Data Exchange (ETDEWEB)
Ortega, Naghelli; Best, Roberto [Centro de Investigacion en Energia, UNAM, Temixco, Morelos (Mexico)
2000-07-01
The refrigeration system designed at the Centro de Investigacion en Energia (CIE), Mexico is able to produce, in optimal conditions, one hundred kilograms per day of ice by means of solar energy. A continuous absorption ammonia-water refrigeration cycle is employed. In its actual state, heat supply to the system is provided through a bank of evacuated tube solar collectors. Their principal difficulties encountered in this system are the indirect heat losses due to the coupling of the falling film generator to the solar heating subsystem that requires a heat transfer gradient and higher collector operating temperatures. Also the high initial cost of the evacuated tube collectors is a barrier for an economical feasible system. Currently, new types of solar collectors are being considered, more efficient and reliable, with a potentially lower cost. This type of collectors known as Compound Parabolic Collectors (CPC) succeed in working at the required temperatures for absorption refrigeration systems. Therefore, a new system is suggested and it is proposed to use a CPC array, where heat losses by the indirect heating system are avoided. In this work a simple method was developed in order to establish the energy balances in a CPC, with a steel tubular receiver without an evacuated glass shell. The receptor's model considers a bidimensional system in stationary state and it supposes a continuous medium. Four nonlinear, simultaneous equations were obtained to predict heat exchange among various components in the system. These equations were utilized in a computer program to analyze the collector performance under various operating conditions. Consequently, the prediction of temperature distribution with respect to position permits to calculate length and arrangement of the CPC for a determined refrigeration application. [Spanish] El sistema de refrigeracion en el Centro de Investigacion en Energia (CIE) Mexico es capaz de producir en condiciones optimas 100
A comparison principle for singular parabolic equations in the Heisenberg group
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Pablo Ochoa
2015-04-01
Full Text Available In this work, we prove a comparison principle for singular parabolic equations with boundary conditions in the context of the Heisenberg group. In particular, this result applies to interesting equations, such as the parabolic infinite Laplacian, the mean curvature flow equation and more general homogeneous diffusions.
Tapering of Polymer Optical Fibers for Compound Parabolic Concentrator Fiber Tip Fabrication
DEFF Research Database (Denmark)
Hassan, Hafeez Ul; Fasano, Andrea; Nielsen, Kristian
2015-01-01
We propose a process for Polymer Optical Fiber (POF) Compound Parabolic Compound (CPC) tip manufacturing using a heat and pull fiber tapering technique. The POF, locally heated above its glass transition temperature, is parabolically tapered down in diameter, after which it is cut to the desired...
Life Span of Positive Solutions for the Cauchy Problem for the Parabolic Equations
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Yusuke Yamauchi
2012-01-01
Full Text Available Since 1960's, the blow-up phenomena for the Fujita type parabolic equation have been investigated by many researchers. In this survey paper, we discuss various results on the life span of positive solutions for several superlinear parabolic problems. In the last section, we introduce a recent result by the author.
Null exact controllability of the parabolic equations with equivalued surface boundary condition
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available This paper is devoted to showing the null exact controllability for a class of parabolic equations with equivalued surface boundary condition. Our method is based on the duality argument and global Carleman-type estimate for a parabolic operator.
Directory of Open Access Journals (Sweden)
2009-02-01
Full Text Available We give conditions for the parabolic evolution operator to be analytic with respect to a coefficient operator. We also show that the solution of a homogeneous parabolic evolution equation is analytic with respect to the coefficient operator and to the initial data. We apply our results to example that can not be studied by the standard methods.
Computing the real parabolic cylinder functions U(a,x), V(a,x)
A. Gil (Amparo); J. Segura (Javier); N.M. Temme (Nico)
2006-01-01
htmlabstractMethods for the computation of real parabolic cylinder functions U(a,x) and V(a,x) and their derivatives are described. We give details on power series, asymptotic series, recursion and quadrature. A combination of these methods can be used for computing parabolic cylinder functions for
Control of parabolic PDEs with time-varying spatial domain: Czochralski crystal growth process
Ng, James; Aksikas, Ilyasse; Dubljevic, Stevan
2013-09-01
This paper considers the optimal control problem for a class of convection-diffusion-reaction systems modelled by partial differential equations (PDEs) defined on time-varying spatial domains. The class of PDEs is characterised by the presence of a time-dependent convective-transport term which is associated with the time evolution of the spatial domain boundary. The functional analytic description of the PDE yields the representation of the initial and boundary value problem as a nonautonomous parabolic evolution equation on an appropriately defined infinite-dimensional function space. The properties of the time-varying evolution operator to guarantee existence and well posedness of the initial and boundary value problem are demonstrated which serves as the basis for the optimal control problem synthesis. An industrial application of the crystal temperature regulation problem for the Czochralski crystal growth process is considered and numerical simulation results are provided.
Off-axis parabolic mirror optics for polarized Raman spectroscopy at low temperature
Chelwani, N.; Hoch, D.; Jost, D.; Botka, B.; Scholz, J.-R.; Richter, R.; Theodoridou, M.; Kretzschmar, F.; Böhm, T.; Kamarás, K.; Hackl, R.
2017-05-01
We report the development of a detection optics for the integration of Raman scattering and scanning probe microscopy at low temperature based on a parabolic mirror. In our set-up, half of the paraboloid mirror covers a solid angle of π corresponding to a numerical aperture of N.A. ≈ 0.85. The optical system can be used for far- and near-field spectroscopy. In the far field, the polarizations can be maintained to within 80%-90%. In combination with a scanning microscope (AFM/STM), tunneling or near-field experiments are possible with less than 10% loss of aperture. Our set-up provides ideal conditions for the future development of tip-enhanced Raman spectroscopy at low temperature.
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Leandro Cerchietti
Full Text Available ALK positive diffuse large B-cell lymphomas (DLBCL are a distinct lymphoma subtype associated with a poor outcome. Most of them feature a t(2;17 encoding a clathrin (CLTC-ALK fusion protein. The contribution of deregulated ALK-activity in the pathogenesis and maintenance of these DLBCLs is not yet known. We established and characterized the first CLTC-ALK positive DLBCL cell line (LM1. LM1 formed tumors in NOD-SCID mice. The selective ALK inhibitor NVP-TAE684 inhibited growth of LM1 cells in vitro at nanomolar concentrations. NVP-TAE684 repressed ALK-activated signalling pathways and induced apoptosis of LM1 DLBCL cells. Inhibition of ALK-activity resulted in sustained tumor regression in the xenotransplant tumor model. These data indicate a role of CLTC-ALK in the maintenance of the malignant phenotype thereby providing a rationale therapeutic target for these otherwise refractory tumors.
Identifying Initial Condition in Degenerate Parabolic Equation with Singular Potential
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K. Atifi
2017-01-01
Full Text Available A hybrid algorithm and regularization method are proposed, for the first time, to solve the one-dimensional degenerate inverse heat conduction problem to estimate the initial temperature distribution from point measurements. The evolution of the heat is given by a degenerate parabolic equation with singular potential. This problem can be formulated in a least-squares framework, an iterative procedure which minimizes the difference between the given measurements and the value at sensor locations of a reconstructed field. The mathematical model leads to a nonconvex minimization problem. To solve it, we prove the existence of at least one solution of problem and we propose two approaches: the first is based on a Tikhonov regularization, while the second approach is based on a hybrid genetic algorithm (married genetic with descent method type gradient. Some numerical experiments are given.
Strong Superconvergence of Finite Element Methods for Linear Parabolic Problems
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Kening Wang
2009-01-01
Full Text Available We study the strong superconvergence of a semidiscrete finite element scheme for linear parabolic problems on =Ω×(0,], where Ω is a bounded domain in ℛ(≤4 with piecewise smooth boundary. We establish the global two order superconvergence results for the error between the approximate solution and the Ritz projection of the exact solution of our model problem in 1,(Ω and ( with 2≤<∞ and the almost two order superconvergence in 1,∞(Ω and ∞(. Results of the =∞ case are also included in two space dimensions (=1 or 2. By applying the interpolated postprocessing technique, similar results are also obtained on the error between the interpolation of the approximate solution and the exact solution.
Test results, Industrial Solar Technology parabolic trough solar collector
Energy Technology Data Exchange (ETDEWEB)
Dudley, V.E. [EG and G MSI, Albuquerque, NM (United States); Evans, L.R.; Matthews, C.W. [Sandia National Labs., Albuquerque, NM (United States)
1995-11-01
Sandia National Laboratories and Industrial Solar Technology are cost-sharing development of advanced parabolic trough technology. As part of this effort, several configurations of an IST solar collector were tested to determine the collector efficiency and thermal losses with black chrome and black nickel receiver selective coatings, combined with aluminized film and silver film reflectors, using standard Pyrex{reg_sign} and anti-reflective coated Pyrex{reg_sign} glass receiver envelopes. The development effort has been successful, producing an advanced collector with 77% optical efficiency, using silver-film reflectors, a black nickel receiver coating, and a solgel anti-reflective glass receiver envelope. For each receiver configuration, performance equations were empirically derived relating collector efficiency and thermal losses to the operating temperature. Finally, equations were derived showing collector performance as a function of input insolation value, incident angle, and operating temperature.
High-order adaptive methods for parabolic systems
Adjerid, S.; Flaherty, J. E.; Moore, P. K.; Wang, Y. J.
1992-11-01
We consider the adaptive solution of parabolic partial differential systems in one and two space dimensions by finite element procedures that automatically refine and coarsen computational meshes, vary the degree of the piecewise polynomial basis and, in one dimension, move the computational mesh. Two-dimensional meshes of triangular, quadrilateral, or a mixture of triangular and quadrilateral elements are generated using a finite quadtree procedure that is also used for data management. A posteriori estimates, used to control adaptive enrichment, are generated from the hierarchical polynomial basis. Temporal integration, within a method-of-lines framework, uses either backward difference methods or a variant of the singly implicit Runge-Kutta (SIRK) methods. A high-level user interface facilitates use of the adaptive software.
Adaptive distributed parameter and input estimation in linear parabolic PDEs
Mechhoud, Sarra
2016-01-01
In this paper, we discuss the on-line estimation of distributed source term, diffusion, and reaction coefficients of a linear parabolic partial differential equation using both distributed and interior-point measurements. First, new sufficient identifiability conditions of the input and the parameter simultaneous estimation are stated. Then, by means of Lyapunov-based design, an adaptive estimator is derived in the infinite-dimensional framework. It consists of a state observer and gradient-based parameter and input adaptation laws. The parameter convergence depends on the plant signal richness assumption, whereas the state convergence is established using a Lyapunov approach. The results of the paper are illustrated by simulation on tokamak plasma heat transport model using simulated data.
Bilinear reduced order approximate model of parabolic distributed solar collectors
Elmetennani, Shahrazed
2015-07-01
This paper proposes a novel, low dimensional and accurate approximate model for the distributed parabolic solar collector, by means of a modified gaussian interpolation along the spatial domain. The proposed reduced model, taking the form of a low dimensional bilinear state representation, enables the reproduction of the heat transfer dynamics along the collector tube for system analysis. Moreover, presented as a reduced order bilinear state space model, the well established control theory for this class of systems can be applied. The approximation efficiency has been proven by several simulation tests, which have been performed considering parameters of the Acurex field with real external working conditions. Model accuracy has been evaluated by comparison to the analytical solution of the hyperbolic distributed model and its semi discretized approximation highlighting the benefits of using the proposed numerical scheme. Furthermore, model sensitivity to the different parameters of the gaussian interpolation has been studied.
Using parabolic mirrors for complete imaging of apple surfaces.
Reese, Daniel; Lefcourt, Alan M; Kim, Moon S; Martin Lo, Y
2009-10-01
Automated imaging systems offer the potential to inspect the quality and safety of fruits consumed by the public. One problem that has hindered adoption of automated technologies has been the inability to image the complete surface of an individual fruit. A particular problem is that both the stem and calyx are concave structures. The goal of this project was to examine tradeoffs for using multiple mirrors to image the surface of apples. For testing, individual apples were suspended using two thin wires, mirrors were placed around an apple, and movies were captured at 90 images per sec. Apples were rotated in all dimensions to examine the efficacy of different mirror configurations. It was determined that specific configurations of two, four, or six parabolic concave mirrors could image an entire surface. A configuration using two mirrors and multiple images acquired as apples roll by was also found to be viable.
Fifth parabolic dish solar thermal power program annual review: proceedings
Energy Technology Data Exchange (ETDEWEB)
None
1984-03-01
The primary objective of the Review was to present the results of activities within the Parabolic Dish Technology and Module/Systems Development element of the Department of Energy's Solar Thermal Energy Systems Program. The Review consisted of nine technical sessions covering overall Project and Program aspects, Stirling and Brayton module development, concentrator and engine/receiver development, and associated hardware and test results to date; distributed systems operating experience; international dish development activities; and non-DOE-sponsored domestic dish activities. A panel discussion concerning business views of solar electric generation was held. These Proceedings contain the texts of presentations made at the Review, as submitted by their authors at the beginning of the Review; therefore, they may vary slightly from the actual presentations in the technical sessions.
Evaluation of Surface Slope Irregularity in Linear Parabolic Solar Collectors
Directory of Open Access Journals (Sweden)
F. Francini
2012-01-01
Full Text Available The paper describes a methodology, very simple in its application, for measuring surface irregularities of linear parabolic collectors. This technique was principally developed to be applied in cases where it is difficult to use cumbersome instruments and to facilitate logistic management. The instruments to be employed are a digital camera and a grating. If the reflector surface is defective, the image of the grating, reflected on the solar collector, appears distorted. Analyzing the reflected image, we can obtain the local slope of the defective surface. These profilometric tests are useful to identify and monitor the mirror portions under mechanical stress and to estimate the losses caused by the light rays deflected outside the absorber.
Development of sheet-metal parabolic-trough reflector panels
Biester, A. W.
1982-06-01
Efforts to develop accurate, durable, and mass producible sheet metal parabolic trough solar collectors and the associated support for the collectors are described. The design considered is similar to an automobile hood, a two-piece sheet metal structure consisting of a formed steel frame or stiffening panel and a smooth contoured skin. The two pieces may be bonded or welded to form a rigid structure, and a reflective surface applied such as a film, glass mirror, or any of the presently utilized materials. The work encompassed material selection, adhesive selection and testing, tool design and fabrication, prototype panel production, and design and development of torque tube assemblies on which the trough is inclined. Results of adhesive bonding studies are given. It is found that high volume technology can be used to produce accurate and structurally sound reflector panels, and one configuration was selected for fabrication in suitable quantities for performance testing.
Approximation of entropy solutions to degenerate nonlinear parabolic equations
Abreu, Eduardo; Colombeau, Mathilde; Panov, Evgeny Yu
2017-12-01
We approximate the unique entropy solutions to general multidimensional degenerate parabolic equations with BV continuous flux and continuous nondecreasing diffusion function (including scalar conservation laws with BV continuous flux) in the periodic case. The approximation procedure reduces, by means of specific formulas, a system of PDEs to a family of systems of the same number of ODEs in the Banach space L^∞, whose solutions constitute a weak asymptotic solution of the original system of PDEs. We establish well posedness, monotonicity and L^1-stability. We prove that the sequence of approximate solutions is strongly L^1-precompact and that it converges to an entropy solution of the original equation in the sense of Carrillo. This result contributes to justify the use of this original method for the Cauchy problem to standard multidimensional systems of fluid dynamics for which a uniqueness result is lacking.
Makovický, Peter; Matlach, Radek; Pokorná, Olga; Mošna, František; Makovický, Pavol
2015-01-01
The bloodstain pattern analysis (BPA) is useful in the forensic medicine. In Czechoslovakian criminology is this method not commonly used. The objective of this work is to calculate the impact length, height and distance splashing of blood drops. The results are compared with the real values for specific cases. It is also compared to calculate the angle of incidence of blood drops, using sinα with a form using tgα. For this purposes we used two different character cases from practice with well-preserved condition and readable blood stains. Selected blood stains were documented in order to calculate the angle of incidence of blood drops and to calculateorigin splashes. For this drop of blood, the distance of impact of the drops of blood (x), the height of the sprayed blood drops (y) and the length of the flight path the drop of blood (l). The obtained data was retrospectively analysed for the two models. The first straight line is represented by the triangle (M1) and the other is the parabolic model (M2). The formulae were derived using the Euler substitution. The results show that the angle of incidence of the drop of blood can be calculated as sinα and the tgα. When applying, the triangle is appropriate to consider the application and sinα parabolic requires the calculation of the angle of incidence drops of blood tgα. Parabola is useful for the BPA. In Czechoslovakian should be providing workplace training seminars BPA primarily intended for forensic investigators.We recommend the use of this method during investigations, verification of acts in forensic practice.
Directory of Open Access Journals (Sweden)
Susanne Voelkel
2013-04-01
Full Text Available The aim of this action research project was to improve student learning by encouraging more “time on task” and to improve self-assessment and feedback through the introduction of weekly online tests in a Year 2 lecture module in biological sciences. Initially voluntary online tests were offered to students and those who participated achieved higher exam marks than those who did not, but completion rate was low. Making the tests compulsory led to high completion rates, but class performance decreased, indicating that using the same assessment for formative and for summative purposes is not always beneficial for learning. Finally, these problems were resolved by introducing a two-stage approach: the first stage of each test was formative and provided prompt feedback. However, students had to achieve 80% to progress to the second summative stage of the test. The two-stage online tests led to significantly improved class performance. This novel test design ensures that students go through at least two attempts and therefore fully benefit from the learning opportunities presented by the formative stage. Two-stage online tests present the opportunity to provide regular feedback in large classes and to improve performance not only of good but also of “weak” students.
Areeda, J. S.; Smith, J. R.; Lundgren, A. P.; Maros, E.; Macleod, D. M.; Zweizig, J.
2017-01-01
Gravitational-wave observatories around the world, including the Laser Interferometer Gravitational-Wave Observatory (LIGO), record a large volume of gravitational-wave output data and auxiliary data about the instruments and their environments. These data are stored at the observatory sites and distributed to computing clusters for data analysis. LigoDV-web is a web-based data viewer that provides access to data recorded at the LIGO Hanford, LIGO Livingston and GEO600 observatories, and the 40 m prototype interferometer at Caltech. The challenge addressed by this project is to provide meaningful visualizations of small data sets to anyone in the collaboration in a fast, secure and reliable manner with minimal software, hardware and training required of the end users. LigoDV-web is implemented as a Java Enterprise Application, with Shibboleth Single Sign On for authentication and authorization, and a proprietary network protocol used for data access on the back end. Collaboration members with proper credentials can request data be displayed in any of several general formats from any Internet appliance that supports a modern browser with Javascript and minimal HTML5 support, including personal computers, smartphones, and tablets. Since its inception in 2012, 634 unique users have visited the LigoDV-web website in a total of 33 , 861 sessions and generated a total of 139 , 875 plots. This infrastructure has been helpful in many analyses within the collaboration including follow-up of the data surrounding the first gravitational-wave events observed by LIGO in 2015.
Electronic Nose Functionality for Breath Gas Analysis during Parabolic Flight
Dolch, Michael E.; Hummel, Thomas; Fetter, Viktor; Helwig, Andreas; Lenic, Joachim; Moukhamedieva, Lana; Tsarkow, Dimitrij; Chouker, Alexander; Schelling, Gustav
2017-06-01
The presence of humans in space represents a constant threat for their health and safety. Environmental factors such as living in a closed confinement, as well as exposure to microgravity and radiation, are associated with significant changes in bone metabolism, muscular atrophy, and altered immune response, which has impacts on human performance and possibly results in severe illness. Thus, maintaining and monitoring of crew health status has the highest priority to ensure whole mission success. With manned deep space missions to moon or mars appearing at the horizon where short-term repatriation back to earth is impossible the availability of appropriate diagnostic platforms for crew health status is urgently needed. In response to this need, the present experiment evaluated the functionality and practicability of a metal oxide based sensor system (eNose) together with a newly developed breath gas collecting device under the condition of altering acceleration. Parabolic flights were performed with an Airbus A300 ZeroG at Bordeaux, France. Ambient air and exhaled breath of five healthy volunteers was analyzed during steady state flight and parabolic flight maneuvres. All volunteers completed the study, the breath gas collecting device valves worked appropriately, and breathing through the collecting device was easy and did not induce discomfort. During breath gas measurements, significant changes in metal oxide sensors, mainly sensitive to aromatic and sulphur containing compounds, were observed with alternating conditions of acceleration. Similarly, metal oxide sensors showed significant changes in all sensors during ambient air measurements. The eNose as well as the newly developed breath gas collecting device, showed appropriate functionality and practicability during alternating conditions of acceleration which is a prerequisite for the intended use of the eNose aboard the International Space Station (ISS) for breath gas analysis and crew health status
Energy Technology Data Exchange (ETDEWEB)
Woodward, P. R.
2003-03-26
This report summarizes the results of the project entitled, ''Piecewise-Parabolic Methods for Parallel Computation with Applications to Unstable Fluid Flow in 2 and 3 Dimensions'' This project covers a span of many years, beginning in early 1987. It has provided over that considerable period the core funding to my research activities in scientific computation at the University of Minnesota. It has supported numerical algorithm development, application of those algorithms to fundamental fluid dynamics problems in order to demonstrate their effectiveness, and the development of scientific visualization software and systems to extract scientific understanding from those applications.
Energy Technology Data Exchange (ETDEWEB)
Cochet, Alexandre [Centre Georges-Francois Leclerc, Department of Nuclear Medicine, Dijon Cedex (France); Le2i UMR CNRS 6306, Dijon (France); Dygai-Cochet, Inna; Riedinger, Jean-Marc; Berriolo-Riedinger, Alina; Toubeau, Michel [Centre Georges-Francois Leclerc, Department of Nuclear Medicine, Dijon Cedex (France); Humbert, Olivier; Brunotte, Francois [Centre Georges-Francois Leclerc, Department of Nuclear Medicine, Dijon Cedex (France); Le2i UMR CNRS 6306, Dijon (France); CHU Dijon, MRI and Spectroscopy Unit, Dijon (France); Guiu, Severine; Coudert, Bruno [Centre Georges-Francois Leclerc, Department of Oncology, Dijon (France); Coutant, Charles; Fumoleau, Pierre [Centre Georges-Francois Leclerc, Department of Surgery, Dijon (France)
2014-03-15
The objective of this study was to assess the impact on management and the prognostic value of {sup 18}F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT for initial staging of newly diagnosed large breast cancer (BC) when compared with conventional staging. We prospectively included 142 patients with newly diagnosed BC and at least grade T2 tumour. All patients were evaluated with complete conventional imaging (CI) procedures (mammogram and/or breast ultrasound, bone scan, abdominal ultrasound and/or CT, X-rays and/or CT of the chest), followed by FDG PET/CT exploration, prior to treatment. The treatment plan based on CI staging was compared with that based on PET/CT findings. CI and PET/CT findings were confirmed by imaging and clinical follow-up and/or pathology when assessable. Progression-free survival (PFS) was analysed using the Cox proportional hazards regression model. According to CI staging, 79 patients (56 %) were stage II, 46 (32 %) stage III and 17 (12 %) stage IV (distant metastases). Of the patients, 30 (21 %) were upstaged by PET/CT, including 12 (8 %) from stage II or III to stage IV. On the other hand, 23 patients (16 %) were downstaged by PET/CT, including 4 (3 %) from stage IV to stage II or III. PET/CT had a high or medium impact on management planning for 18 patients (13 %). Median follow-up was 30 months (range 9-59 months); 37 patients (26 %) experienced recurrence or progression of disease during follow-up and 17 patients (12 %) died. The Cox model indicated that CI staging was significantly associated with PFS (p = 0.01), but PET/CT staging provided stronger prognostic stratification (p < 0.0001). Moreover, Cox regression multivariate analysis showed that only PET/CT staging remained associated with PFS (p < 0.0001). FDG PET/CT provides staging information that more accurately stratifies prognostic risk in newly diagnosed large BC when compared with conventional explorations alone. (orig.)
Ball, Chad G.; Keaney, Marilyn A.; Chun, Rosaleen; Groleau, Michelle; Tyssen, Michelle; Keyte, Jennifer; Broderick, Timothy J.; Kirkpatrick, Andrew W.
2010-03-01
BackgroundMultiple nations are actively pursuing manned exploration of space beyond low-earth orbit. The responsibility to improve surgical care for spaceflight is substantial. Although the use of parabolic flight as a terrestrial analogue to study surgery in weightlessness (0 g) is well described, minimal data is available to guide the appropriate delivery of anesthesia. After studying anesthetized pigs in a 0 g parabolic flight environment, our group developed a comprehensive protocol describing prolonged anesthesia in a parabolic flight analogue space surgery study (PFASSS). Novel challenges included a physically remote vivarium, prolonged (>10 h) anesthetic requirements, and the provision of veterinary operating room/intensive care unit (ICU) equivalency on-board an aircraft with physical dimensions of laboratory sessions were conducted with combinations of anesthetic, pre-medication, and induction protocols on Yorkshire-cross specific pathogen-free (SPF) pigs. Several constant rate infusion (CRI) intravenous anesthetic combinations were tested. In each regimen, opioids were administered to ensure analgesia. Ventilation was supported mechanically with blended gradients of oxygen. The best performing terrestrial 1 g regime was flight tested in parabolic flight for its effectiveness in sustaining optimal and prolonged anesthesia, analgesia, and maintaining hemodynamic stability. Each flight day, a fully anesthetized, ventilated, and surgically instrumented pig was transported to the Flight Research Laboratory (FRL) in a temperature-controlled animal ambulance. A modular on-board surgical/ICU suite with appropriate anesthesia/ICU and surgical support capabilities was employed. ResultsThe mean duration of anesthesia (per flight day) was 10.28 h over four consecutive days. A barbiturate and ketamine-based CRI anesthetic regimen supplemented with narcotic analgesia by bolus administration offered the greatest prolonged hemodynamic stability through an IV route
Biosignal alterations generated by parabolic flights of small aerobatic aircrafts
Simon, M. Jose; Perez-Poch, Antoni; Ruiz, Xavier; Gavalda, Fina; Saez, Nuria
Since the pioneering works of Prof. Strughold in 1948, the aerospace medicine aimed to characterize the modifications induced in the human body by changes in the gravity level. In this respect, it is nowadays well known that one of the most serious problems of these kind of environments is the fluid shift. If this effect is enough severe and persistent, serious changes in the hemodynamic of the brain (cerebral blood flow and blood oxigenation level) appear which could be detected as alterations in the electroencephalogram, EEG [1]. Also, this fluid redistribution, together with the relocation of the heart in the thorax, induces detectable changes in the electrocardiogram, ECG [2]. Other kind of important problems are related with vestibular instability, kinetosis and illusory sensations. In particular since the seventies [3,4] it is known that in parabolic flights and due to eye movements triggered by the changing input from the otholith system, fixed real targets appeared to have moved downward while visual afterimages appeared to have moved upward (oculogravic illusions). In order to cover all the above-mentioned potential alterations, the present work, together with the gravity level, continuously monitors the electroencephalogram, EEG, the electrocardiogram, ECG and the electrooculogram, EOG of a normal subject trying to detect correlations between the different alterations observed in these signals and the changes of gravity during parabolic flights. The small aerobatic aircraft used is a CAP10B and during the flight the subject is located near the pilot. To properly cover all the range of accelerations we have used two sensitive triaxial accelerometers covering the high and low ranges of acceleration. Biosignals have been gathered using a Biopac data unit together with the Acknowledge software package (from BionicÔ). It is important to finally remark that, due to the obvious difference between the power of the different engines, the accelerometric
Pletser, Vladimir; Clervoy, Jean-Fran; Gharib, Thierry; Gai, Frederic; Mora, Christophe; Rosier, Patrice
Aircraft parabolic flights provide repetitively up to 20 seconds of reduced gravity during ballis-tic flight manoeuvres. Parabolic flights are used to conduct short microgravity investigations in Physical and Life Sciences and in Technology, to test instrumentation prior to space flights and to train astronauts before a space mission. The European Space Agency (ESA) has organized since 1984 more than fifty parabolic flight campaigns for microgravity research experiments utilizing six different airplanes. More than 600 experiments were conducted spanning several fields in Physical Sciences and Life Sciences, namely Fluid Physics, Combustion Physics, Ma-terial Sciences, fundamental Physics and Technology tests, Human Physiology, cell and animal Biology, and technical tests of Life Sciences instrumentation. Since 1997, ESA uses the Airbus A300 'Zero G', the largest airplane in the world used for this type of experimental research flight and managed by the French company Novespace, a subsidiary of the French space agency CNES. From 2010 onwards, ESA and Novespace will offer the possibility of flying Martian and Moon parabolas during which reduced gravity levels equivalent to those on the Moon and Mars will be achieved repetitively for periods of more than 20 seconds. Scientists are invited to submit experiment proposals to be conducted at these partial gravity levels. This paper presents the technical capabilities of the Airbus A300 Zero-G aircraft used by ESA to support and conduct investigations at Moon-, Mars-and micro-gravity levels to prepare research and exploration during space flights and future planetary exploration missions. Some Physiology and Technology experiments performed during past ESA campaigns at 0, 1/6 an 1/3 g are presented to show the interest of this unique research tool for microgravity and partial gravity investigations.
Romanelli, Gherardo; Mignone, Andrea; Cervone, Angelo
2017-10-01
Pulsed fusion propulsion might finally revolutionise manned space exploration by providing an affordable and relatively fast access to interplanetary destinations. However, such systems are still in an early development phase and one of the key areas requiring further investigations is the operation of the magnetic nozzle, the device meant to exploit the fusion energy and generate thrust. One of the last pulsed fusion magnetic nozzle design is the so called multi-coil parabolic reaction chamber: the reaction is thereby ignited at the focus of an open parabolic chamber, enclosed by a series of coaxial superconducting coils that apply a magnetic field. The field, beside confining the reaction and preventing any contact between hot fusion plasma and chamber structure, is also meant to reflect the explosion and push plasma out of the rocket. Reflection is attained thanks to electric currents induced in conductive skin layers that cover each of the coils, the change of plasma axial momentum generates thrust in reaction. This working principle has yet to be extensively verified and computational Magneto-Hydro Dynamics (MHD) is a viable option to achieve that. This work is one of the first detailed ideal-MHD analysis of a multi-coil parabolic reaction chamber of this kind and has been completed employing PLUTO, a freely distributed computational code developed at the Physics Department of the University of Turin. The results are thus a preliminary verification of the chamber's performance. Nonetheless, plasma leakage through the chamber structure has been highlighted. Therefore, further investigations are required to validate the chamber design. Implementing a more accurate physical model (e.g. Hall-MHD or relativistic-MHD) is thus mandatory, and PLUTO shows the capabilities to achieve that.
Nonlocal operators, parabolic-type equations, and ultrametric random walks
Energy Technology Data Exchange (ETDEWEB)
Chacón-Cortes, L. F., E-mail: fchaconc@math.cinvestav.edu.mx; Zúñiga-Galindo, W. A., E-mail: wazuniga@math.cinvestav.edu.mx [Centro de Investigacion y de Estudios Avanzados del I.P.N., Departamento de Matematicas, Av. Instituto Politecnico Nacional 2508, Col. San Pedro Zacatenco, Mexico D.F., C.P. 07360 (Mexico)
2013-11-15
In this article, we introduce a new type of nonlocal operators and study the Cauchy problem for certain parabolic-type pseudodifferential equations naturally associated to these operators. Some of these equations are the p-adic master equations of certain models of complex systems introduced by Avetisov, V. A. and Bikulov, A. Kh., “On the ultrametricity of the fluctuation dynamicmobility of protein molecules,” Proc. Steklov Inst. Math. 265(1), 75–81 (2009) [Tr. Mat. Inst. Steklova 265, 82–89 (2009) (Izbrannye Voprosy Matematicheskoy Fiziki i p-adicheskogo Analiza) (in Russian)]; Avetisov, V. A., Bikulov, A. Kh., and Zubarev, A. P., “First passage time distribution and the number of returns for ultrametric random walks,” J. Phys. A 42(8), 085003 (2009); Avetisov, V. A., Bikulov, A. Kh., and Osipov, V. A., “p-adic models of ultrametric diffusion in the conformational dynamics of macromolecules,” Proc. Steklov Inst. Math. 245(2), 48–57 (2004) [Tr. Mat. Inst. Steklova 245, 55–64 (2004) (Izbrannye Voprosy Matematicheskoy Fiziki i p-adicheskogo Analiza) (in Russian)]; Avetisov, V. A., Bikulov, A. Kh., and Osipov, V. A., “p-adic description of characteristic relaxation in complex systems,” J. Phys. A 36(15), 4239–4246 (2003); Avetisov, V. A., Bikulov, A. H., Kozyrev, S. V., and Osipov, V. A., “p-adic models of ultrametric diffusion constrained by hierarchical energy landscapes,” J. Phys. A 35(2), 177–189 (2002); Avetisov, V. A., Bikulov, A. Kh., and Kozyrev, S. V., “Description of logarithmic relaxation by a model of a hierarchical random walk,” Dokl. Akad. Nauk 368(2), 164–167 (1999) (in Russian). The fundamental solutions of these parabolic-type equations are transition functions of random walks on the n-dimensional vector space over the field of p-adic numbers. We study some properties of these random walks, including the first passage time.
Directory of Open Access Journals (Sweden)
Chunrong Mi
2017-01-01
Full Text Available Species distribution models (SDMs have become an essential tool in ecology, biogeography, evolution and, more recently, in conservation biology. How to generalize species distributions in large undersampled areas, especially with few samples, is a fundamental issue of SDMs. In order to explore this issue, we used the best available presence records for the Hooded Crane (Grus monacha, n = 33, White-naped Crane (Grus vipio, n = 40, and Black-necked Crane (Grus nigricollis, n = 75 in China as three case studies, employing four powerful and commonly used machine learning algorithms to map the breeding distributions of the three species: TreeNet (Stochastic Gradient Boosting, Boosted Regression Tree Model, Random Forest, CART (Classification and Regression Tree and Maxent (Maximum Entropy Models. In addition, we developed an ensemble forecast by averaging predicted probability of the above four models results. Commonly used model performance metrics (Area under ROC (AUC and true skill statistic (TSS were employed to evaluate model accuracy. The latest satellite tracking data and compiled literature data were used as two independent testing datasets to confront model predictions. We found Random Forest demonstrated the best performance for the most assessment method, provided a better model fit to the testing data, and achieved better species range maps for each crane species in undersampled areas. Random Forest has been generally available for more than 20 years and has been known to perform extremely well in ecological predictions. However, while increasingly on the rise, its potential is still widely underused in conservation, (spatial ecological applications and for inference. Our results show that it informs ecological and biogeographical theories as well as being suitable for conservation applications, specifically when the study area is undersampled. This method helps to save model-selection time and effort, and allows robust and rapid
Less trouble with orbits: The semi-classical hydrogen problem in parabolic and spherical coordinates
Bucher, Manfred
2014-01-01
Historically, the eccentricity of Sommerfeld orbits from quantization conditions in either parabolic or spherical coordinates was found to differ in almost all cases. To do the orbit comparison correctly, one must use amended instead of traditional Sommerfeld orbits.
Ka Band Parabolic Deployable Antenna (KaPDA) for Interplanetary CubeSat Communications Project
National Aeronautics and Space Administration — Ka Band Parabolic Deployable Antenna (KaPDA) for Interplanetary CubeSat Communications allowing moving up from UHF, S or X to get higher gain for a given diameter.
Parabolic Theory as a High-Dimensional Limit of Elliptic Theory
Davey, Blair
2017-10-01
The aim of this article is to show how certain parabolic theorems follow from their elliptic counterparts. This technique is demonstrated through new proofs of five important theorems in parabolic unique continuation and the regularity theory of parabolic equations and geometric flows. Specifically, we give new proofs of an L 2 Carleman estimate for the heat operator, and the monotonicity formulas for the frequency function associated to the heat operator, the two-phase free boundary problem, the flow of harmonic maps, and the mean curvature flow. The proofs rely only on the underlying elliptic theorems and limiting procedures belonging essentially to probability theory. In particular, each parabolic theorem is proved by taking a high-dimensional limit of the related elliptic result.
An existence theorem for parabolic equations on $R^N$ with discontinuous nonlinearity
Directory of Open Access Journals (Sweden)
Péter Simon
2001-01-01
Full Text Available We prove existence of solutions for parabolic initial value problems $\\partial_t u = \\Delta u + f(u$ on $R^N$ , where $f : R \\rightarrow R$ is a bounded, but possibly discontinuous function.
Space dimension can prevent the blow-up of solutions for parabolic problems
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Alkis S. Tersenov
2007-11-01
Full Text Available In the present paper, we investigate the preventive role of space dimension for semilinear parabolic problems. Conditions guaranteeing the absence of the blow-up of the solutions are formulated.
Existence and continuity of global attractors for a degenerate semilinear parabolic equation
Directory of Open Access Journals (Sweden)
Cung The Anh
2009-05-01
Full Text Available In this article, we study the existence and the upper semicontinuity with respect to the nonlinearity and the shape of the domain of global attractors for a semilinear degenerate parabolic equation involving the Grushin operator.
Sound field computations in the Bay of Bengal using parabolic equation method
Digital Repository Service at National Institute of Oceanography (India)
Navelkar, G.S.; Somayajulu, Y.K.; Murty, C.S.
Effect of the cold core eddy in the Bay of Bengal on acoustic propagation was analysed by parabolic equation (PE) method. Source depth, frequency and propagation range considered respectively for the two numerical experiments are 150 m, 400 Hz, 650...
Asymptotic behavior of solutions to nonlinear parabolic equation with nonlinear boundary conditions
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Diabate Nabongo
2008-01-01
Full Text Available We show that solutions of a nonlinear parabolic equation of second order with nonlinear boundary conditions approach zero as t approaches infinity. Also, under additional assumptions, the solutions behave as a function determined here.
Wind Tunnel Tests of Parabolic Trough Solar Collectors: March 2001--August 2003
Energy Technology Data Exchange (ETDEWEB)
Hosoya, N.; Peterka, J. A.; Gee, R. C.; Kearney, D.
2008-05-01
Conducted extensive wind-tunnel tests on parabolic trough solar collectors to determine practical wind loads applicable to structural design for stress and deformation, and local component design for concentrator reflectors.
Initial boundary value problems for second order parabolic systems in cylinders with polyhedral base
National Research Council Canada - National Science Library
Luong, Vu Trong; Loi, Do Van
2011-01-01
The purpose of this article is to establish the well posedness and the regularity of the solution of the initial boundary value problem with Dirichlet boundary conditions for second-order parabolic...
The Projective Parabolic Geometry of Riemannian, K\\"ahler and Quaternion-K\\"ahler Metrics
Frost, George E.
2016-01-01
We present a uniform framework generalising and extending the classical theories of projective differential geometry, c-projective geometry, and almost quaternionic geometry. Such geometries, which we call \\emph{projective parabolic geometries}, are abelian parabolic geometries whose flat model is an R-space $G\\cdot\\mathfrak{p}$ in the infinitesimal isotropy representation $\\mathbb{W}$ of a larger self-dual symmetric R-space $H\\cdot\\mathfrak{q}$. We also give a classification of projective pa...
Marian Malec; Lucjan Sapa
2007-01-01
This paper deals with a finite difference method for a wide class of weakly coupled nonlinear second-order partial differential systems with initial condition and weakly coupled nonlinear implicit boundary conditions. One part of each system is of the parabolic type (degenerated parabolic equations) and the other of the elliptic type (equations with a parameter) in a cube in \\(\\mathbf{R}^{1+n}\\). A suitable finite difference scheme is constructed. It is proved that the scheme has a unique sol...
Iterative Methods for Solving Nonlinear Parabolic Problem in Pension Saving Management
Koleva, M. N.
2011-11-01
In this work we consider a nonlinear parabolic equation, obtained from Riccati like transformation of the Hamilton-Jacobi-Bellman equation, arising in pension saving management. We discuss two numerical iterative methods for solving the model problem—fully implicit Picard method and mixed Picard-Newton method, which preserves the parabolic characteristics of the differential problem. Numerical experiments for comparison the accuracy and effectiveness of the algorithms are discussed. Finally, observations are given.
Directory of Open Access Journals (Sweden)
Allaberen Ashyralyev
2014-04-01
Full Text Available We study initial-boundary value problems for fractional parabolic equations with the Dirichlet-Neumann conditions. We obtain a stable difference schemes for this problem, and obtain theorems on coercive stability estimates for the solution of the first order of accuracy difference scheme. A procedure of modified Gauss elimination method is applied for the solution of the first and second order of accuracy difference schemes of one-dimensional fractional parabolic differential equations.
Efficient parabolic evaluation of coupling terms in hybrid quantum/classical simulations
Energy Technology Data Exchange (ETDEWEB)
Bastida, Adolfo, E-mail: bastida@um.es [Departamento de Quimica Fisica, Facultad de Quimica, Universidad de Murcia, 30100 Murcia (Spain); Soler, Miguel Angel; Zuniga, Jose; Requena, Alberto [Departamento de Quimica Fisica, Facultad de Quimica, Universidad de Murcia, 30100 Murcia (Spain); Miguel, Beatriz [Departamento de Ingenieria Quimica y Ambiental, Universidad Politecnica de Cartagena, 30203 Cartagena (Spain)
2009-03-30
A parabolic interpolation function of time is proposed to evaluate the non-adiabatic coupling matrix elements and the adiabatic energies at intermediate times within the classical time integration interval in hybrid quantum/classical simulations. The accuracy and the computational efficiency of this parabolic approximation are illustrated by carrying out a numerical application to the well-studied vibrational relaxation of I{sub 2} in liquid xenon.
Poincare inequality and Campanato estimates for weak solutions of parabolic equations
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Junichi Aramaki
2016-07-01
Full Text Available We shall show that the Poincare type inequality holds for the weak solution of a parabolic equation. The key is to control the $L^p$ norm of the first derivative of the weak solution with respect to the time variable. The inequality is necessary to get an estimate in the Campanato space $\\mathcal{L}^{p,\\mu }$ for general parabolic equations.
Computing the real parabolic cylinder functions U(a,x), V(a,x)
Gil, Amparo; Segura, Javier; Temme, Nico
2006-01-01
htmlabstractMethods for the computation of real parabolic cylinder functions U(a,x) and V(a,x) and their derivatives are described. We give details on power series, asymptotic series, recursion and quadrature. A combination of these methods can be used for computing parabolic cylinder functions for unrestricted values of the order a and the variable x except for the overflow/underflow limitations. By factoring the dominant exponential factor, scaled functions can be computed without practical...
Cheeda, V. K.; Kumar, A.; Ramamurthi, K.
2014-03-01
Flow blockages are used to promote the transition of a flame to a detonation. The structure of shock waves formed with different configurations of blockages was experimentally determined for subsonic incoming flow. High speed subsonic flows could develop ahead of a turbulent flame and the interaction of such flows with blockages could lead to the formation of interacting shock waves, slipstreams, and expansion waves. A blow-down test setup was designed to study the interacting shock pattern formed with different configurations of blockages. The flow was found to accelerate to low supersonic velocities during its passage over the blockages. The shock structure downstream of the blockages was found to depend on the shape, size, and number of blockages as well as the spacing between them. While a parabolic-shaped blockage provided shocks of maximum strength, large blockage ratio values did not permit the formation of shocks. The shear layer, formed in the flow downstream of the blockages, reflected the expansion fan as shock waves and was found to be a major feature influencing the formation of the interacting structure of oblique shocks. The structure and strength of the shock waves are analyzed using hodograms. The formation of the interacting family of shock waves using different configurations of blockages and the spacings between them are discussed.
Parabolic Trough Photovoltaic/Thermal Collectors: Design and Simulation Model
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Laura Vanoli
2012-10-01
Full Text Available This paper presents a design procedure and a simulation model of a novel concentrating PVT collector. The layout of the PVT system under investigation was derived from a prototype recently presented in literature and commercially available. The prototype consisted in a parabolic trough concentrator and a linear triangular receiver. In that prototype, the bottom surfaces of the receiver are equipped with mono-crystalline silicon cells whereas the top surface is covered by an absorbing surface. The aperture area of the parabola was covered by a glass in order to improve the thermal efficiency of the system. In the modified version of the collector considered in this paper, two changes are implemented: the cover glass was eliminated and the mono-crystalline silicon cells were replaced by triple-junction cells. In order to analyze PVT performance, a detailed mathematical model was implemented. This model is based on zero-dimensional energy balances. The simulation model calculates the temperatures of the main components of the system and the main energy flows Results showed that the performance of the system is excellent even when the fluid temperature is very high (>100 °C. Conversely, both electrical and thermal efficiencies dramatically decrease when the incident beam radiation decreases.
Perception of Egocentric Distance during Gravitational Changes in Parabolic Flight.
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Gilles Clément
Full Text Available We explored the effect of gravity on the perceived representation of the absolute distance of objects to the observers within the range from 1.5-6 m. Experiments were performed on board the CNES Airbus Zero-G during parabolic flights eliciting repeated exposures to short periods of microgravity (0 g, hypergravity (1.8 g, and normal gravity (1 g. Two methods for obtaining estimates of perceived egocentric distance were used: verbal reports and visually directed motion toward a memorized visual target. For the latter method, because normal walking is not possible in 0 g, blindfolded subjects translated toward the visual target by pulling on a rope with their arms. The results showed that distance estimates using both verbal reports and blind pulling were significantly different between normal gravity, microgravity, and hypergravity. Compared to the 1 g measurements, the estimates of perceived distance using blind pulling were shorter for all distances in 1.8 g, whereas in 0 g they were longer for distances up to 4 m and shorter for distances beyond. These findings suggest that gravity plays a role in both the sensorimotor system and the perceptual/cognitive system for estimating egocentric distance.
Photocatalytic disinfection of water using low cost compound parabolic collectors
Energy Technology Data Exchange (ETDEWEB)
McLoughlin, O.A.; Gill, L.W. [Dublin Univ. (Ireland). Dept. of Civil, Structural and Environmental Engineering; Ibanez, F.; Gernjak, W.; Malato Rodriguez, S. [Plataforma Solar de Almeria (CIEMAT), Tabemas (Spain)
2004-11-01
The objective of this work was to assess the effectiveness of using near UV light to disinfect water supplies for potential applications in developing countries. A pilot scale photoreactor comprised of non-tracking compound parabolic collectors installed at Plataforma Solar de Almeria was examined and a comparison of disinfection efficiency using E. coli K-12 was carried out with a reactor configuration of 3 and 1 m{sup 2} illuminated area. Tests were also carried out using suspensions of titanium dioxide (TiO{sub 2}) at concentrations ranging from 0 to 9 mg/l. The removal of E. coli K-12 from initial concentrations of 1 x 10{sup 5} CFU/ml to below the limit of detection was achieved both with and without the use of TiO{sub 2}. Levels of inactivation in 35 l of inoculated water of up to 4-log removal were achieved in under 30 min. The addition of TiO{sub 2} created an enhancement to the process only at the 3 mg/l dose. However, the results have also suggested the possibility that another disinfection mechanism, possibly governed by the frequency of intermittent UV light exposure, was regulating the overall inactivation kinetics of the trials. (Author)
Experimental performance analysis for mini-parabolic solar reflecting collectors
Energy Technology Data Exchange (ETDEWEB)
Barakos, G.; Kaplanis, S.; Spyrogiannoulas, A. [Technological Educational Inst. of Patras, Patra (Greece)
2007-07-01
This paper presented a detailed analysis of the thermal behaviour of a mini-parabolic solar reflecting collector installed on the roof of a building. A data logging system was used to monitor fluid inlet and outlet temperatures in the absorber; total solar radiation incident on the aperture surface; ambient temperatures; and fluid flow measurements. The aim of the study was to increase the reliability of the collector, maximize output, and optimize the geometrical and physical characteristics of the collector's components. Experiments were conducted over a 4-day period in October and November 2006 at a location in Greece. Data obtained during the experiments showed that as the mass flow rate increased, the outlet and inlet temperatures decreased. The system's efficiency increased as the mass flow rate increased. Losses were decreased when temperatures in the tube absorber remained low. The results of several subsequent experiments confirmed that higher mass flow rates increase the efficiency of the collectors.15 refs., 10 figs.
Development of a Small Modular Parabolic trough Collector
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Hoffschmidt, B.; Schwarzer, K.; Spate, F.; Kotter, J.; Ebert, M.; Sierck, O.
2006-07-01
A small parabolic trough collector is developed with the purpose to achieve a high efficiency at temperatures up to 300 degree Celsius. The collector has an aperture area of 1 m width and 2 m length. Therefore it can be used very easily for roof installations. Tests at the collector test stand of the Solar-Institut Juelich show good results up to 100 degree celsius. The power is about 1 kW. The collector's efficiency is above 50%. Stagnation experiments have shown temperatures around 590 degree celsius at a direct radiation of 730 W/square meters and 7 degree Celsius ambient temperature. The collector consists of a form giving rib construction of stainless steel covered with an aluminum reflector with a reflection coefficient of 95%. A standard vacuum tube (Sidney-principle) 200 cm long is used as absorber. Anti Reflex Glass with a solar transmission of more than 95% is used as cover. The tracking system is consisting of a stepper motor, transmission, sun sensor and electronic steering. (Author)
de Schrijver, E.; Chameleva, H.; Degroote, C.; D'Haese, Z.; Paice, C.; Plas, H.; Van den Bossche, A.; Vander Donckt, L.; Vander Vost, J.
2015-09-01
Flight opportunities on high-altitude ASGARD balloons offered to secondary schools worldwide since 20 1 1 have led to an ever more rapidly increasing number of project proposals. The introduction of beginners' and ‘advanced classes of experiments is hoped to draw in even larger numbers of interested school teams. Furthermore, and in cooperation with ESERO (European Space Education Resources Office), workshops and documentation are being prepared to introduce teachers and students alike to the world of microcontrollers and sensors. A student parabolic flight programme called BIFROST (Brussels' Initiative to provide Flight Research Opportunities to STudents) was initiated to meet the rising demand for hands-on space education projects and the desire to cover the widest possible range of scientific and/or technical domains, which essentially calls for a variety of flight platforms: cansats, balloons and parabolic flight.
Energy Technology Data Exchange (ETDEWEB)
Buerger, R.; Frid, H.; Karlsen, K.H.
2002-07-01
We consider a free boundary problem of a quasilinear strongly degenerate parabolic equation arising from a model of pressure filtration of flocculated suspensions. We provide definitions of generalized solutions of the free boundary problem in the framework of L2 divergence-measure fields. The formulation of boundary conditions is based on a Gauss-Green theorem for divergence-measure fields on bounded domains with Lipschitz deformable boundaries and avoids referring to traces of the solution. This allows to consider generalized solutions from a larger class than BV. Thus it is not necessary to derive the usual uniform estimates on spatial and time derivatives of the solutions of the corresponding regularized problem requires in the BV approach. We first prove existence and uniqueness of the solution of the regularized parabolic free boundary problem and then apply the vanishing viscosity method to prove existence of a generalized solution to the degenerate free boundary problem. (author)
Yue, Yunhao; Zhou, Baoming; Shi, Jie; Chen, Cheng; Li, Nan; Xu, Zhiwei; Liu, Liangsen; Kuang, Liyun; Ma, Meijun; Fu, Hongjun
2017-05-01
This paper reported a method to fabricate graphene oxide sheets supported Ag nanoparticles (AgNPs/GOS) with single crystalline structure and parabolic distribution without surfactant or functional agent. We used imidazole silver nitrate as intercalation precursor into the layers of graphite oxide, and subsequently reduction and growth of interlamellar AgNPs were induced via γ-irradiation. The results illustrated that the synergism of interlamellar limitation of graphite oxide and fragmentation ability of γ-irradiation could prevent coalescent reaction of AgNPs with other oligomeric clusters, and the single crystalline and small-sized (below 13.9 nm) AgNPs were prepared. Moreover, the content and size of AgNPs exhibited parabolic distribution on GOS surface because the graphite oxide exfoliated to GOS from the edge to the central area of layers. In addition, complete exfoliation degree of GOS and large-sized AgNPs were obtained simultaneously under suitable silver ions concentration. Optimized composites exhibited outstanding surface-enhanced Raman scattering properties for crystal violet with enhancement factor of 1.3 × 106 and detection limit of 1.0 × 10-7 M, indicating that the AgNPs/GOS composites could be applied to trace detection of organic dyes molecules. Therefore, this study presented a strategy for developing GOS supported nanometal with single crystalline structure and parabolic distribution based on γ-irradiation.
Energy Technology Data Exchange (ETDEWEB)
Yue, Yunhao; Zhou, Baoming; Shi, Jie; Chen, Cheng; Li, Nan; Xu, Zhiwei, E-mail: xuzhiwei@tjpu.edu.cn; Liu, Liangsen; Kuang, Liyun; Ma, Meijun; Fu, Hongjun
2017-05-01
Highlights: • Graphene oxide sheets supported Ag nanoparticles composites are successfully prepared via γ-irradiation without surfactant or functional agent. • Ag nanoparticles exhibit single crystalline structure and parabolic distribution on the surface of graphene oxide sheets. • Proposing a view that the growth of intercellular AgNPs can be limited by graphite oxide. - Abstract: This paper reported a method to fabricate graphene oxide sheets supported Ag nanoparticles (AgNPs/GOS) with single crystalline structure and parabolic distribution without surfactant or functional agent. We used imidazole silver nitrate as intercalation precursor into the layers of graphite oxide, and subsequently reduction and growth of interlamellar AgNPs were induced via γ-irradiation. The results illustrated that the synergism of interlamellar limitation of graphite oxide and fragmentation ability of γ-irradiation could prevent coalescent reaction of AgNPs with other oligomeric clusters, and the single crystalline and small-sized (below 13.9 nm) AgNPs were prepared. Moreover, the content and size of AgNPs exhibited parabolic distribution on GOS surface because the graphite oxide exfoliated to GOS from the edge to the central area of layers. In addition, complete exfoliation degree of GOS and large-sized AgNPs were obtained simultaneously under suitable silver ions concentration. Optimized composites exhibited outstanding surface-enhanced Raman scattering properties for crystal violet with enhancement factor of 1.3 × 10{sup 6} and detection limit of 1.0 × 10{sup −7} M, indicating that the AgNPs/GOS composites could be applied to trace detection of organic dyes molecules. Therefore, this study presented a strategy for developing GOS supported nanometal with single crystalline structure and parabolic distribution based on γ-irradiation.
Quasi-parabolic reflecting bottom surfaces of the Drygalski Antarctic floating ice tongue
Directory of Open Access Journals (Sweden)
E. Zuccheretti
2001-06-01
Full Text Available Very high frequency deep radio sounding systems for ice thickness measurements are practically the only useful apparatuses for large scale radar flight surveys in polar regions. The morphology of the bottom surface of an Antarctic floating ice tongue, in the Ross Sea area, East Antarctica, was studied using the arrival times of signal echoes of the radio sounding system. The amplitude variations of radar signals from the reflecting surface were analyzed to determine the gain or the loss of the reflectors. Such surfaces show quasi-parabolic geometrical shapes at the ice/water interface with both concave and convex faces towards the sounding system. Electromagnetic analysis performed on radar echoes indicates that amplitude variations detected by the antenna are focusing or defocusing effects only due to the reflector's shape. A factor in the radar equation that represents the surface shape when coherent reflectors are involved is introduced. This factor allows us to determine more precisely the morphology and electromagnetic characteristics of the interface between the media investigated by means of radio echo sounding.
Heat and electricity from the Sun using parabolic dish collector systems
Truscello, V. C.; Williams, A. N.
1980-01-01
Point focus distributed receiver solar thermal technology for the production of electric power and of industrial process heat is addressed. The thermal power systems project which emphasizes the development of cost effective systems which will accelerate the commercialization and industrialization of plants up to 10 MWe, using parabolic dish collectors is described. The projected size of the isolated load market in the 1990-2000 time period is 300 to 1000 MW/year. Although this market is small in comparison to the grid connected utility market, it is indicated that by assuming only a 20 percent market penetration, up to 10,000 power modules per year would be required to meet this need. At a production rate of 25,000 units/year and assuming no energy storage, levelized bus bar energy costs of 75 mills/kWeh are projected. These numbers are based on what is believed to be a conservative estimate regarding engine-generator conversion efficiency (40 percent) for the 1990 time period. With a more optimistic estimate of efficiency (i.e., 45 percent), the bus bar cost decreases to about 67 mills/kWeh. At very large production rates (400,000 modules/years), the costs decrease to 58 mills/kWeh. Finally, the present status of the technology development effort is discussed.
Bilinear Approximate Model-Based Robust Lyapunov Control for Parabolic Distributed Collectors
Elmetennani, Shahrazed
2016-11-09
This brief addresses the control problem of distributed parabolic solar collectors in order to maintain the field outlet temperature around a desired level. The objective is to design an efficient controller to force the outlet fluid temperature to track a set reference despite the unpredictable varying working conditions. In this brief, a bilinear model-based robust Lyapunov control is proposed to achieve the control objectives with robustness to the environmental changes. The bilinear model is a reduced order approximate representation of the solar collector, which is derived from the hyperbolic distributed equation describing the heat transport dynamics by means of a dynamical Gaussian interpolation. Using the bilinear approximate model, a robust control strategy is designed applying Lyapunov stability theory combined with a phenomenological representation of the system in order to stabilize the tracking error. On the basis of the error analysis, simulation results show good performance of the proposed controller, in terms of tracking accuracy and convergence time, with limited measurement even under unfavorable working conditions. Furthermore, the presented work is of interest for a large category of dynamical systems knowing that the solar collector is representative of physical systems involving transport phenomena constrained by unknown external disturbances.
Heat and electricity from the Sun using parabolic dish collector systems
Truscello, V. C.; Williams, A. N.
1980-05-01
Point focus distributed receiver solar thermal technology for the production of electric power and of industrial process heat is addressed. The thermal power systems project which emphasizes the development of cost effective systems which will accelerate the commercialization and industrialization of plants up to 10 MWe, using parabolic dish collectors is described. The projected size of the isolated load market in the 1990-2000 time period is 300 to 1000 MW/year. Although this market is small in comparison to the grid connected utility market, it is indicated that by assuming only a 20 percent market penetration, up to 10,000 power modules per year would be required to meet this need. At a production rate of 25,000 units/year and assuming no energy storage, levelized bus bar energy costs of 75 mills/kWeh are projected. These numbers are based on what is believed to be a conservative estimate regarding engine-generator conversion efficiency (40 percent) for the 1990 time period. With a more optimistic estimate of efficiency (i.e., 45 percent), the bus bar cost decreases to about 67 mills/kWeh. At very large production rates (400,000 modules/years), the costs decrease to 58 mills/kWeh. Finally, the present status of the technology development effort is discussed.
Directory of Open Access Journals (Sweden)
Álvaro Lentz–Herrea
2009-04-01
Full Text Available The Northwest of Mexico is a well known region with the highest ambient temperatures along the summer and the highest levels of irradiance, which make it feasible to install solar field concentrators. This work provides beam irradiance data that can be used to design a solar north–south parabolic trough system. The variation between the value of beam solar irradiance estimated by a pyranometer and the direct irradiance received by the aperture area of a parabolic trough concentrator (PTC is well–known as cosθ. This variation was evaluated every day of the year, obtaining values of average irradiance for Cerro Prieto (CP lat. 32°39', long. 115° 21', and San Luis Rio Colorado (SLR lat. 32°30', long. 114°46', with which they were elaborated the available energy and cumulative frequency curves (CFC. These are useful to know the number of hours of field solar concentrators which can operate at different levels of energy, as well as the steam production of a solar–geothermal hybrid system to produce electricity.
Goswami, Deepjyoti
2013-05-01
In the first part of this article, a new mixed method is proposed and analyzed for parabolic integro-differential equations (PIDE) with nonsmooth initial data. Compared to the standard mixed method for PIDE, the present method does not bank on a reformulation using a resolvent operator. Based on energy arguments combined with a repeated use of an integral operator and without using parabolic type duality technique, optimal L2 L2-error estimates are derived for semidiscrete approximations, when the initial condition is in L2 L2. Due to the presence of the integral term, it is, further, observed that a negative norm estimate plays a crucial role in our error analysis. Moreover, the proposed analysis follows the spirit of the proof techniques used in deriving optimal error estimates for finite element approximations to PIDE with smooth data and therefore, it unifies both the theories, i.e., one for smooth data and other for nonsmooth data. Finally, we extend the proposed analysis to the standard mixed method for PIDE with rough initial data and provide an optimal error estimate in L2, L 2, which improves upon the results available in the literature. © 2013 Springer Science+Business Media New York.
Optimising position control of a solar parabolic trough
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Puramanathan Naidoo
2011-03-01
Full Text Available In today’s climate of growing energy needs and increasing environmental concerns, alternatives to the use of non-renewable and polluting fossil fuels have to be investigated. One such alternative is solar energy. This study is based on the implementation of a mathematical computation – the PSA (Plataforma Solar de Almeria computation developed at PSA (the European Test Centre for solar energy applications – embedded in a control algorithm to locate the position of the sun. Tests were conducted on a solar parabolic trough (SPT constructed at the Solar Thermal Applications Research Laboratory of the Mangosuthu University of Technology (Durban, South Africa for optimal position control using the PSA value. The designed control algorithm embedded in an industrial Siemens S7-314 C-2PtP programmable logic controller compared the PSA computation to a measured position of the SPT to optimally rotate the SPT to a desired position with the constant movement of the sun. The two main angles of the sun relative to the position of the SPT on earth, the zenith angle and the azimuth angle, both calculated in the PSA from the vertical and horizontal planes, respectively, were applied to the control algorithm to generate an appropriate final tracking angle within a 0.007 radian (0° 24′ 3.6″ tolerance, in accordance to the construction specifications and solar collector testing standards of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE, 1991. These values, together with the longitude and latitude applicable to the geographical location of the SPT, were processed in the control software to rotate the SPT to an optimal position with respect to the position of the sun in its daily path, for solar-to-thermal conversion.
Performance and durability testing of parabolic trough receivers
Lei, Dongqiang; Fu, Xuqiang; Zhao, Dongming; Yuan, Guofeng; Wang, Zhifeng; Guo, Minghuan
2017-06-01
The paper describes the key performance and durability testing facilities of the parabolic trough receiver developed by Institute of Electrical Engineering, Chinese Academy of Sciences. The indoor heat loss test can be applied at 4-7 different temperature levels within 200-550 on receivers. The optical efficiency test bench consists of 12 metal halide lamps as the solar simulator and a 5 m length half-elliptical cylinder reflector with flat end reflectors. 3 ultra-precision temperature sensors are used in receiver each end to get the temperature difference. The residual gas analysis test bench is applied to analyze and predict the vacuum lifetime of the receiver. It can test the variations of composition and partial pressure of residual gases with temperature and time in the receiver annulus space by a high sensitivity quadrupole mass spectrometer gas analyzer. A coating accelerated ageing test bench, which is also used to test the thermal cycle, has been developed. This test bench uses the absorber tube of the recevier as the resistance heater to heat up the whole receiver. The coating lifetime can be predicted by the Arrhenius parameters. For the cycling test, the compressed air is used to directly cool the inner surface of the absorber tube. The thermal cycling test is performed with temperature cycles from 150 °C to 450 °C for 160 cycles. The maximum thermal cycling frequency is 8 cycles per day. The mechanical fatigue test bench is used to test the bellows and the glass-to-metal seals durability at the same time. Both bellows are expanded and compressed to 6.5 mm in turn with 10,000 cycles. A new rotating test bench was also developed to test the thermal efficiency of the receiver.
Srogi, L.; Willis, K. V.; Lutz, T. M.; Plank, T. A.; Pollock, M.; Connolly, B.; Wood, A. M.
2016-12-01
Small, shallow portions of large magmatic systems cool more rapidly and potentially have less subsolidus overprinting than large mafic intrusions, but it is unclear whether they are small-scale analogs for the same crystallization processes. The Morgantown-Jacksonwald magmatic system (MJS), western Newark Basin, Pennsylvania, is part of the 201-Ma Central Atlantic Magmatic Province (CAMP) formed during Pangean rifting. The MJS consists of several interconnected intrusions exposed in cross-section from the Jacksonwald basalt at the paleosurface to 6 km depth (variably LREE-enriched rims; some negative Eu anomalies. REE patterns calculated for liquids in equilibrium with opx using published Kd values are roughly parallel to but significantly higher than REE in host chill margin diabase. CSDs of opx and matrix plagioclase from several samples within 10m of the basal contact will be used to evaluate models of crystal growth vs. mechanical sorting. Modes and mineral compositions are not consistent with MELTS fractionation models: opx crystallizes in place of pigeonite; pyroxenes are zoned in Ca not Fe-Mg; late-crystallizing quartz and K-feldspar are lacking. These features suggest crystallization buffered by earlier phases in the crystal mush with some melt migration, similar to processes that produce more extreme layering in large mafic intrusions.
Pustal, J; Traulsen, I; Preißler, R; Müller, K; Beilage, T Große; Börries, U; Kemper, N
2015-01-01
One possible way to support raising large litter sizes in pigs is to offer supplementary, artificial milk ad libitum in the farrowing pen in addition to the sow's milk. In order to evaluate the potential use of this method and its effects on performance and health, supplemented (n = 60) and control sows (n = 60) with their litters were tested over 15 batches in one herd during one year. In the supplemented group (SG), piglets had access to supplementary milk in addition to sow's milk from their 2nd day of life until weaning (day 27). The litters of SG sows were adjusted to contain as many piglets as the sow had functional teats, whereas in the control group (CG), piglets were set to the number of functional teats minus one, due to animal welfare reasons. With supplementary milk provision, the weaning of large litters was achieved without any negative impacts on performance and health. On average, 13.5 and 12.4 piglets were weaned in SG and CG, respectively (P 0.05) and average daily weight gain of the piglets (SG: 0.25 kg v. CG: 0.25 kg; P > 0.05) did not differ, total litter weight was consequently higher in SG than in CG (104.9 kg v. 96.7 kg; P 0.05). With regard to documented medical treatments, facial lesions were treated less frequently in piglets of SG (46 v. 32 treatments; P 0.05). To summarise, in the presented case offering ad libitum supplementary, artificial milk supported the sow in raising large litters by compensating possible negative impacts of high piglet numbers on the weight gain of piglets and the body condition of the sows.
Tactile Cueing as a Gravitational Substitute for Spatial Navigation During Parabolic Flight
Montgomery, K. L.; Beaton, K. H.; Barba, J. M.; Cackler, J. M.; Son, J. H.; Horsfield, S. P.; Wood, S. J.
2010-01-01
INTRODUCTION: Spatial navigation requires an accurate awareness of orientation in your environment. The purpose of this experiment was to examine how spatial awareness was impaired with changing gravitational cues during parabolic flight, and the extent to which vibrotactile feedback of orientation could be used to help improve performance. METHODS: Six subjects were restrained in a chair tilted relative to the plane floor, and placed at random positions during the start of the microgravity phase. Subjects reported their orientation using verbal reports, and used a hand-held controller to point to a desired target location presented using a virtual reality video mask. This task was repeated with and without constant tactile cueing of "down" direction using a belt of 8 tactors placed around the mid-torso. Control measures were obtained during ground testing using both upright and tilted conditions. RESULTS: Perceptual estimates of orientation and pointing accuracy were impaired during microgravity or during rotation about an upright axis in 1g. The amount of error was proportional to the amount of chair displacement. Perceptual errors were reduced during movement about a tilted axis on earth. CONCLUSIONS: Reduced perceptual errors during tilts in 1g indicate the importance of otolith and somatosensory cues for maintaining spatial awareness. Tactile cueing may improve navigation in operational environments or clinical populations, providing a non-visual non-auditory feedback of orientation or desired direction heading.
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Muhammad Umair
2014-03-01
Full Text Available Simulation study of a solar adsorption refrigeration system using a wing type compound parabolic concentrator (CPC is presented. The system consists of the wing type collector set at optimum angles, adsorption bed, a condenser and a refrigerator. The wing type collector captures the solar energy efficiently in the morning and afternoon and provides the effective temperature for a longer period of time compared to that achieved by a linear collector. The objectives of the study were to evaluate the system behavior, the effect of wing length, and to compare the performance of the systems with wing type and linear CPCs. A detailed dynamic simulation model was developed based on mass and energy balance equations. The simulation results show that the system performance with wing type CPC increases by up to 6% in the summer and up to 2% in the winter, compared to the performance with a linear CPC having same collector length. The ice production also increases up to 13% in the summer with the wing type CPC. This shows that the wing type CPC is helpful to increase the performance of the system compared to the linear CPC with the same collector length and without the need for tracking.
Prediction of far-field wind turbine noise propagation with parabolic equation.
Lee, Seongkyu; Lee, Dongjai; Honhoff, Saskia
2016-08-01
Sound propagation of wind farms is typically simulated by the use of engineering tools that are neglecting some atmospheric conditions and terrain effects. Wind and temperature profiles, however, can affect the propagation of sound and thus the perceived sound in the far field. A better understanding and application of those effects would allow a more optimized farm operation towards meeting noise regulations and optimizing energy yield. This paper presents the parabolic equation (PE) model development for accurate wind turbine noise propagation. The model is validated against analytic solutions for a uniform sound speed profile, benchmark problems for nonuniform sound speed profiles, and field sound test data for real environmental acoustics. It is shown that PE provides good agreement with the measured data, except upwind propagation cases in which turbulence scattering is important. Finally, the PE model uses computational fluid dynamics results as input to accurately predict sound propagation for complex flows such as wake flows. It is demonstrated that wake flows significantly modify the sound propagation characteristics.
Norwich Technologies' Advanced Low-Cost Receivers for Parabolic Troughs
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Stettenheim, Joel [Norwich Technologies, White River Junction, VT (United States); McBride, Troy O. [Norwich Technologies, White River Junction, VT (United States); Brambles, Oliver J. [Norwich Technologies, White River Junction, VT (United States); Cashin, Emil A. [Norwich Technologies, White River Junction, VT (United States)
2013-12-31
This report summarizes the successful results of our SunShot project, Advanced Low-Cost Receivers for Parabolic Troughs. With a limited budget of $252K and in only 12 months, we have (1) developed validated optical and thermal models and completed rigorous optimization analysis to identify key performance characteristics as part of developing first-generation laboratory prototype designs, (2) built optical and thermal laboratory prototypes and test systems with associated innovative testing protocols, and (3) performed extensive statistically relevant testing. We have produced fully functioning optical and thermal prototypes and accurate, validated models shown to capture important underlying physical mechanisms. The test results from the first-generation prototype establish performance exceeding the FOA requirement of thermal efficiency >90% for a CSP receiver while delivering an exit fluid temperature of > 650 °C and a cost < $150/kWth. Our vacuum-free SunTrap receiver design provides improvements over conventional vacuum-tube collectors, allowing dramatic reductions in thermal losses at high operating temperature.
Dynamic Modeling of the Solar Field in Parabolic Trough Solar Power Plants
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Lourdes A. Barcia
2015-11-01
Full Text Available Parabolic trough solar power plants use a thermal fluid to transfer thermal energy from solar radiation to a water-steam Rankine cycle in order to drive a turbine that, coupled to an electrical generator, produces electricity. These plants have a heat transfer fluid (HTF system with the necessary elements to transform solar radiation into heat and to transfer that thermal energy to the water-steam exchangers. In order to get the best possible performance in the Rankine cycle and, hence, in the thermal plant, it is necessary that the thermal fluid reach its maximum temperature when leaving the solar field (SF. Also, it is mandatory that the thermal fluid does not exceed the maximum operating temperature of the HTF, above which it degrades. It must be noted that the optimal temperature of the thermal fluid is difficult to obtain, since solar radiation can change abruptly from one moment to another. The aim of this document is to provide a model of an HTF system that can be used to optimize the control of the temperature of the fluid without interfering with the normal operation of the plant. The results obtained with this model will be contrasted with those obtained in a real plant.
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Teffera M. Asfaw
2017-01-01
Full Text Available Let X be a real locally uniformly convex reflexive Banach space with locally uniformly convex dual space X⁎. Let T:X⊇D(T→2X⁎ be maximal monotone, S:X→2X⁎ be bounded and of type (S+, and C:D(C→X⁎ be compact with D(T⊆D(C such that C lies in Γστ (i.e., there exist σ≥0 and τ≥0 such that Cx≤τx+σ for all x∈D(C. A new topological degree theory is developed for operators of the type T+S+C. The theory is essential because no degree theory and/or existence result is available to address solvability of operator inclusions involving operators of the type T+S+C, where C is not defined everywhere. Consequently, new existence theorems are provided. The existence theorem due to Asfaw and Kartsatos is improved. The theory is applied to prove existence of weak solution (s for a nonlinear parabolic problem in appropriate Sobolev spaces.
Polzien, R. E.; Rodriguez, D.
1981-01-01
Aspects of incorporating a thermal energy transport system (ETS) into a field of parabolic dish collectors for industrial process heat (IPH) applications were investigated. Specific objectives are to: (1) verify the mathematical optimization of pipe diameters and insulation thicknesses calculated by a computer code; (2) verify the cost model for pipe network costs using conventional pipe network construction; (3) develop a design and the associated production costs for incorporating risers and downcomers on a low cost concentrator (LCC); (4) investigate the cost reduction of using unconventional pipe construction technology. The pipe network design and costs for a particular IPH application, specifically solar thermally enhanced oil recovery (STEOR) are analyzed. The application involves the hybrid operation of a solar powered steam generator in conjunction with a steam generator using fossil fuels to generate STEOR steam for wells. It is concluded that the STEOR application provides a baseline pipe network geometry used for optimization studies of pipe diameter and insulation thickness, and for development of comparative cost data, and operating parameters for the design of riser/downcomer modifications to the low cost concentrator.
White, Patrick; Arnold, Robert; Bull, Janet; Cicero, Brandon
2018-01-01
Bone metastases are a common complication in patients with advanced cancer but little is known regarding current practice patterns of palliative care providers when prescribing corticosteroids as adjuvant therapy for painful bone metastases. To identify current practice patterns among palliative care providers when prescribing corticosteroids for the treatment of painful bone metastases. A cross-sectional, online survey of the membership of the American Academy of Hospice and Palliative Medicine. Providers were asked to report how frequently they prescribed corticosteroids as adjuvant therapy in patients with painful bone metastases, and to specify the corticosteroid, dosage, treatment duration, and the gastroprotective strategy most frequently utilized. Seven hundred sixty-five participants responded to the survey and 600 (78%) of respondents completed the survey. Ninety-eight percent of respondents completing the survey reported having prescribed corticosteroids as adjuvant pain therapy, and 66% ordered corticosteroids for the majority of their patients with painful bone metastases. Dexamethasone was the most widely prescribed corticosteroid. Eight milligrams divided twice daily was the most common dosage selected and once started, it was usually continued indefinitely. Corticosteroids are commonly prescribed as adjuvant therapy in the treatment of painful bone metastases in patients with limited life expectancy. Dexamethasone is the most commonly selected corticosteroid by American palliative care providers with variation existing among providers regarding dosing schedule, treatment duration, and gastroprotective strategies. Clinical trials comparing a total daily dose of four versus eight milligrams of dexamethasone would be clinically useful to inform evidence-based practice.
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Druskin, V.; Knizhnerman, L.
1994-12-31
The authors solve the Cauchy problem for an ODE system Au + {partial_derivative}u/{partial_derivative}t = 0, u{vert_bar}{sub t=0} = {var_phi}, where A is a square real nonnegative definite symmetric matrix of the order N, {var_phi} is a vector from R{sup N}. The stiffness matrix A is obtained due to semi-discretization of a parabolic equation or system with time-independent coefficients. The authors are particularly interested in large stiff 3-D problems for the scalar diffusion and vectorial Maxwell`s equations. First they consider an explicit method in which the solution on a whole time interval is projected on a Krylov subspace originated by A. Then they suggest another Krylov subspace with better approximating properties using powers of an implicit transition operator. These Krylov subspace methods generate optimal in a spectral sense polynomial approximations for the solution of the ODE, similar to CG for SLE.
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Aguilar, J. O.; Calam, J. S.; Acosta, R.; Cuevas, J. D.; Hernandez, J.; Jaramillo, O. A.; Perez-Rabago, C.; Flores, J. J.
2008-07-01
Design and construction of 1.06 m width and 2.44 m large parabolic trough collector with 0.26 m focal length and 90 degree centigrade rim angle are presented. The design of collector components was made using CAD/CAM commercial software and they were machined with computerized numerical control (CNC). The ray tracing analysis showed that the optimal absorber diameter is 5 mm, neglecting errors or imperfections however, for mechanical and standardization reasons, it was decided to use and absorbent tube diameter of 19,05. Structural stress by finite element analysis it showed that the minimum safety factor was 4,21 and 34,22 MPa the maximum value of stress. Considering that the aluminum allowable stress is 145 MPa, then the proposed prototype resist the design loads without deformed permanently. (Author)
Parabolic systems of Shilov-type with coefficients of bounded smoothness and nonnegative genus
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V. A. Litovchenko
2017-07-01
Full Text Available The Shilov-type parabolic systems are parabolically stable systems for changing its coefficients unlike of parabolic systems by Petrovskii. That's why the modern theory of the Cauchy problem for class by Shilov-type systems is developing abreast how the theory of the systems with constant or time-dependent coefficients alone. Building the theory of the Cauchy problem for systems with variable coefficients is actually today. A new class of linear parabolic systems with partial derivatives to the first order by the time $t$ with variable coefficients that includes a class of the Shilov-type systems with time-dependent coefficients and non-negative genus is considered in this work. A main part of differential expression concerning space variable $x$ of each such system is parabolic (by Shilov expression. Coefficients of this expression are time-dependent, but coefficients of a group of younger members may depend also a space variable. We built the fundamental solution of the Cauchy problem for systems from this class by the method of sequential approximations. Conditions of minimal smoothness on coefficients of the systems by variable $x$ are founded, the smoothness of solution is investigated and estimates of derivatives of this solution are obtained. These results are important for investigating of the correct solution of the Cauchy problem for this systems in different functional spaces, obtaining forms of description of the solution of this problem and its properties.
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Yang Ding
2016-09-01
Full Text Available Like mammals, fish possess an interferon regulatory factor 3 (IRF3/IRF7-dependent type I IFN responses, but the exact mechanism by which IRF3/IRF7 regulate the type I IFNs remains largely unknown. In this study, we identified two type I IFNs in the Perciforme fish large yellow croaker Larimichthys crocea, one of which belongs to the fish IFNd subgroup, and the other is assigned to a novel subgroup of group I IFNs in fish, tentatively termed IFNh. The two IFN genes are constitutively expressed in all examined tissues, but with varied expression levels. Both IFN genes can be rapidly induced in head kidney and spleen tissues by polyinosinic-polycytidylic acid. The recombinant IFNh was shown to be more potent to trigger a rapid induction of the antiviral genes MxA and PKR than the IFNd, suggesting that they may play distinct roles in regulating early antiviral immunity. Strikingly, IFNd, but not IFNh, could induce the gene expression of itself and IFNh through a positive feedback loop mediated by the IFNd-dependent activation of IRF3 and IRF7. Furthermore, our data demonstrate that the induction of IFNd can be enhanced by the dimeric formation of IRF3 and IRF7, while the IFNh expression mainly involves IRF3. Taken together, our findings demonstrate that the IFN responses are diverse in fish and are likely to be regulated by distinct mechanisms.
Struzenberg, L. L.; West, J. S.
2011-01-01
This paper describes the use of targeted Loci/CHEM CFD simulations to evaluate the effects of a dual-engine first-stage hot-fire test on an evolving integrated launch pad/test article design. This effort was undertaken as a part of the NESC Independent Assessment of the Taurus II Stage Test Series. The underlying conceptual model included development of a series of computational models and simulations to analyze the plume induced environments on the pad, facility structures and test article. A pathfinder simulation was first developed, capable of providing quick-turn around evaluation of plume impingement pressures on the flame deflector. Results from this simulation were available in time to provide data for an ongoing structural assessment of the deflector. The resulting recommendation was available in a timely manner and was incorporated into construction schedule for the new launch stand under construction at Wallops Flight Facility. A series of Reynolds-Averaged Navier-Stokes (RANS) quasi-steady simulations representative of various key elements of the test profile was performed to identify potential concerns with the test configuration and test profile. As required, unsteady Hybrid-RANS/LES simulations were performed, to provide additional insight into critical aspects of the test sequence. Modifications to the test-specific hardware and facility structures thermal protection as well as modifications to the planned hot-fire test profile were implemented based on these simulation results.
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Marian Malec
2007-01-01
Full Text Available This paper deals with a finite difference method for a wide class of weakly coupled nonlinear second-order partial differential systems with initial condition and weakly coupled nonlinear implicit boundary conditions. One part of each system is of the parabolic type (degenerated parabolic equations and the other of the elliptic type (equations with a parameter in a cube in \\(\\mathbf{R}^{1+n}\\. A suitable finite difference scheme is constructed. It is proved that the scheme has a unique solution, and the numerical method is consistent, convergent and stable. The error estimate is given. Moreover, by the method, the differential problem has at most one classical solution. The proof is based on the Banach fixed-point theorem, the maximum principle for difference functional systems of the parabolic type and some new difference inequalities. It is a new technique of studying the mixed-type systems. Examples of physical applications and numerical experiments are presented.
Development and test of an end reflector for parabolic trough collectors
Energy Technology Data Exchange (ETDEWEB)
Fend, T.; Bohmer, M.; Binner, P.; Deidewig, F. [Deutsches Zentrum fur Luft-und Raumfahrt e.V., Solare Energietechnik, Koln (Germany); Leon, J.; Kemme, R. [Plataforma Solar de Almeria (Spain)
1999-03-01
Within the DLR-Project PAREX (PArabolRinnen EXperiment) it could be shown by experiments and calculations, that collector efficiencies of parabolic troughs car be increased by up to 2% by means of the use of an end reflector, which is placed at the north end of each trough (in case of a north-south oriented plant at the northern hemisphere). Calculations show that the intensity of the incident concentrated radiation on the surface of the absorber increases by a factor of two. A first prototype of a 0,7 m{sup 2} end reflector was tested at the DLR in the PARMESAN (PArabolRinnenMESsANlage) test facility. The radiation profile around the absorber was measured and compared to the calculated results. A second 6,4 m{sup 2} end reflector was designed and built up at the LS-3 test loop at the Plataforma Solar de Almeria (PSA). (authors)
A gradient estimate for solutions to parabolic equations with discontinuous coefficients
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Jishan Fan
2013-04-01
Full Text Available Li-Vogelius and Li-Nirenberg gave a gradient estimate for solutions of strongly elliptic equations and systems of divergence forms with piecewise smooth coefficients, respectively. The discontinuities of the coefficients are assumed to be given by manifolds of codimension 1, which we called them emph{manifolds of discontinuities}. Their gradient estimate is independent of the distances between manifolds of discontinuities. In this paper, we gave a parabolic version of their results. That is, we gave a gradient estimate for parabolic equations of divergence forms with piecewise smooth coefficients. The coefficients are assumed to be independent of time and their discontinuities are likewise the previous elliptic equations. As an application of this estimate, we also gave a pointwise gradient estimate for the fundamental solution of a parabolic operator with piecewise smooth coefficients. Both gradient estimates are independent of the distances between manifolds of discontinuities.
Mondal, Sudip; Hegarty, Evan; Martin, Chris; Gökçe, Sertan Kutal; Ghorashian, Navid; Ben-Yakar, Adela
2016-10-01
Next generation drug screening could benefit greatly from in vivo studies, using small animal models such as Caenorhabditis elegans for hit identification and lead optimization. Current in vivo assays can operate either at low throughput with high resolution or with low resolution at high throughput. To enable both high-throughput and high-resolution imaging of C. elegans, we developed an automated microfluidic platform. This platform can image 15 z-stacks of ~4,000 C. elegans from 96 different populations using a large-scale chip with a micron resolution in 16 min. Using this platform, we screened ~100,000 animals of the poly-glutamine aggregation model on 25 chips. We tested the efficacy of ~1,000 FDA-approved drugs in improving the aggregation phenotype of the model and identified four confirmed hits. This robust platform now enables high-content screening of various C. elegans disease models at the speed and cost of in vitro cell-based assays.
Shcherbakov, Alexandre S.; Luna Castellanos, Abraham; Tepichin Rodriguez, Eduardo; Balderas Mata, Sandra E.
2008-02-01
We develop our previous considerations for one of the most important problems related to optimizing the performance data of a new acousto-optical spectrometer for the analysis of radio-astronomical signals. The main attention is paid to estimating the side lobes of light distributions inherent in an individual resolvable spot in the output Fourier plane, governing the dynamic range of that spectrometer. At first, we analyze the Akhieser mechanism responsible for linear attenuation of both longitudinal and shear elastic waves in isotropic solid states. Similar analysis can be directly applied to crystalline materials as well in all the cases of passing elastic wave along the acoustic axis in crystals. Then, we estimate the influence of the acoustic attenuation along a large-aperture acousto-optical cells operating in a one- and two-phonon light scattering regimes. In so doing, the optimal operating points are discussed for both these regimes. Finally, the combined effect of the acoustic attenuation and the incident light beam apodization is studied from the points of view of optimizing the levels of side lobes and minima in light distribution of an individual resolvable spot in focal plane of the integrating lens and, consequently, estimating potential limitations of the dynamic range.
Hwang, Yeonsoo; Yoon, Dukyong; Ahn, Eun Kyoung; Hwang, Hee; Park, Rae Woong
2016-12-01
To determine the risk factors and rate of medication administration error (MAE) alerts by analyzing large-scale medication administration data and related error logs automatically recorded in a closed-loop medication administration system using radio-frequency identification and barcodes. The subject hospital adopted a closed-loop medication administration system. All medication administrations in the general wards were automatically recorded in real-time using radio-frequency identification, barcodes, and hand-held point-of-care devices. MAE alert logs recorded during a full 1 year of 2012. We evaluated risk factors for MAE alerts including administration time, order type, medication route, the number of medication doses administered, and factors associated with nurse practices by logistic regression analysis. A total of 2 874 539 medication dose records from 30 232 patients (882.6 patient-years) were included in 2012. We identified 35 082 MAE alerts (1.22% of total medication doses). The MAE alerts were significantly related to administration at non-standard time [odds ratio (OR) 1.559, 95% confidence interval (CI) 1.515-1.604], emergency order (OR 1.527, 95%CI 1.464-1.594), and the number of medication doses administered (OR 0.993, 95%CI 0.992-0.993). Medication route, nurse's employment duration, and working schedule were also significantly related. The MAE alert rate was 1.22% over the 1-year observation period in the hospital examined in this study. The MAE alerts were significantly related to administration time, order type, medication route, the number of medication doses administered, nurse's employment duration, and working schedule. The real-time closed-loop medication administration system contributed to improving patient safety by preventing potential MAEs. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Weilburg, Jeffrey B; Sistrom, Christopher L; Rosenthal, Daniel I; Stout, Markus B; Dreyer, Keith J; Rockett, Helaine R; Baron, Jason M; Ferris, Timothy G; Thrall, James H
2017-09-01
Purpose To quantify the effect of a comprehensive, long-term, provider-led utilization management (UM) program on high-cost imaging (computed tomography, magnetic resonance imaging, nuclear imaging, and positron emission tomography) performed on an outpatient basis. Materials and Methods This retrospective, 7-year cohort study included all patients regularly seen by primary care physicians (PCPs) at an urban academic medical center. The main outcome was the number of outpatient high-cost imaging examinations per patient per year ordered by the patient's PCP or by any specialist. The authors determined the probability of a patient undergoing any high-cost imaging procedure during a study year and the number of examinations per patient per year (intensity) in patients who underwent high-cost imaging. Risk-adjusted hierarchical models were used to directly quantify the physician component of variation in probability and intensity of high-cost imaging use, and clinicians were provided with regular comparative feedback on the basis of the results. Observed trends in high-cost imaging use and provider variation were compared with the same measures for outpatient laboratory studies because laboratory use was not subject to UM during this period. Finally, per-member per-year high-cost imaging use data were compared with statewide high-cost imaging use data from a major private payer on the basis of the same claim set. Results The patient cohort steadily increased in size from 88 959 in 2007 to 109 823 in 2013. Overall high-cost imaging utilization went from 0.43 examinations per year in 2007 to 0.34 examinations per year in 2013, a decrease of 21.33% (P < .0001). At the same time, similarly adjusted routine laboratory study utilization decreased by less than half that rate (9.4%, P < .0001). On the basis of unadjusted data, outpatient high-cost imaging utilization in this cohort decreased 28%, compared with a 20% decrease in statewide utilization (P = .0023). Conclusion
Numerical solution of the stochastic parabolic equation with the dependent operator coefficient
Energy Technology Data Exchange (ETDEWEB)
Ashyralyev, Allaberen [Department of Elementary Mathematics Education, Fatih University, 34500, Istanbul (Turkey); Department of Mathematics, ITTU, Ashgabat (Turkmenistan); Okur, Ulker [Institute for Stochastics and Applications, Department of Mathematics, University of Stuttgart, 70569, Stuttgart (Germany)
2015-09-18
In the present paper, a single step implicit difference scheme for the numerical solution of the stochastic parabolic equation with the dependent operator coefficient is presented. Theorem on convergence estimates for the solution of this difference scheme is established. In applications, this abstract result permits us to obtain the convergence estimates for the solution of difference schemes for the numerical solution of initial boundary value problems for parabolic equations. The theoretical statements for the solution of this difference scheme are supported by the results of numerical experiments.
Integration of equations of parabolic type by the method of nets
Saul'Yev, V K; Stark, M; Ulam, S
1964-01-01
International Series of Monographs in Pure and Applied Mathematics, Volume 54: Integration of Equations of Parabolic Type by the Method of Nets deals with solving parabolic partial differential equations using the method of nets. The first part of this volume focuses on the construction of net equations, with emphasis on the stability and accuracy of the approximating net equations. The method of nets or method of finite differences (used to define the corresponding numerical method in ordinary differential equations) is one of many different approximate methods of integration of partial diff
A multiplicity result for a class of quasilinear elliptic and parabolic problems
Directory of Open Access Journals (Sweden)
M. R. Grossinho
1997-04-01
Full Text Available We prove the existence of infinitely many solutions for a class of quasilinear elliptic and parabolic equations, subject respectively to Dirichlet and Dirichlet-periodic boundary conditions. We assume that the primitive of the nonlinearity at the right-hand side oscillates at infinity. The proof is based on the construction of upper and lower solutions, which are obtained as solutions of suitable comparison equations. This method allows the introduction of conditions on the potential for the study of parabolic problems, as well as to treat simultaneously the singular and the degenerate case.
Parabolic Higgs bundles and Teichmüller spaces for punctured surfaces
Biswas, I; Govindarajan, S; Biswas, Indranil; Gastesi, Pablo; Govindarajan, Suresh
1995-01-01
In this paper we study the relation between parabolic Higgs bundles and irreducible representations of the fundamental group of punctured Riemann surfaces established by Simpson. We generalize a result of Hitchin, identifying those parabolic Higgs bundles that correspond to Fuchsian representations. We also study the Higgs bundles that give representations whose image is contained, after conjugation, in SL(k,\\Bbb R). We compute the real dimension of one of the components of this space of representations, which in the absence of punctures is the generalized Teichm\\"uller space introduced by Hitchin, and which in the case of k=2 is the Teichm\\"uller space of the Riemann surface.
Investigation on medium temperature heat pipe receiver used in parabolic trough solar collector
Energy Technology Data Exchange (ETDEWEB)
Zhan, Dongdong; Zhang, Hong; Liu, Yun; Li, Sihai; Zhuang, Jun [Nanjing Univ. of Technology (China). Inst. of Thermal Energy Engineering
2008-07-01
In this paper, a novel medium temperature (250{proportional_to}500 C) heat pipe receiver was developed for parabolic trough solar collector and the feasibility study on the receiver was carried out. The lifetime analysis, thermal analysis and economic analysis of the heat pipe receiver were presented. The result showed that the heat pipe receiver was flexible, easily maintained, low manufacture cost and could be working reliability in the temperature and heat flux conditions of parabolic trough solar collector with a high heat collect efficiency. (orig.)
Distribution-valued weak solutions to a parabolic problem arising in financial mathematics
Directory of Open Access Journals (Sweden)
Michael Eydenberg
2009-07-01
Full Text Available We study distribution-valued solutions to a parabolic problem that arises from a model of the Black-Scholes equation in option pricing. We give a minor generalization of known existence and uniqueness results for solutions in bounded domains $Omega subset mathbb{R}^{n+1}$ to give existence of solutions for certain classes of distributions $fin mathcal{D}'(Omega$. We also study growth conditions for smooth solutions of certain parabolic equations on $mathbb{R}^nimes (0,T$ that have initial values in the space of distributions.
Hofberger, Johannes A.; Ramirez, Aldana M.; van den Bergh, Erik; Zhu, Xinguang; Bouwmeester, Harro J.; Schuurink, Robert C.; Schranz, M. Eric
2015-01-01
An important component of plant evolution is the plethora of pathways producing more than 200,000 biochemically diverse specialized metabolites with pharmacological, nutritional and ecological significance. To unravel dynamics underlying metabolic diversification, it is critical to determine lineage-specific gene family expansion in a phylogenomics framework. However, robust functional annotation is often only available for core enzymes catalyzing committed reaction steps within few model systems. In a genome informatics approach, we extracted information from early-draft gene-space assemblies and non-redundant transcriptomes to identify protein families involved in isoprenoid biosynthesis. Isoprenoids comprise terpenoids with various roles in plant-environment interaction, such as pollinator attraction or pathogen defense. Combining lines of evidence provided by synteny, sequence homology and Hidden-Markov-Modelling, we screened 17 genomes including 12 major crops and found evidence for 1,904 proteins associated with terpenoid biosynthesis. Our terpenoid genes set contains evidence for 840 core terpene-synthases and 338 triterpene-specific synthases. We further identified 190 prenyltransferases, 39 isopentenyl-diphosphate isomerases as well as 278 and 219 proteins involved in mevalonate and methylerithrol pathways, respectively. Assessing the impact of gene and genome duplication to lineage-specific terpenoid pathway expansion, we illustrated key events underlying terpenoid metabolic diversification within 250 million years of flowering plant radiation. By quantifying Angiosperm-wide versatility and phylogenetic relationships of pleiotropic gene families in terpenoid modular pathways, our analysis offers significant insight into evolutionary dynamics underlying diversification of plant secondary metabolism. Furthermore, our data provide a blueprint for future efforts to identify and more rapidly clone terpenoid biosynthetic genes from any plant species. PMID
Hofberger, Johannes A; Ramirez, Aldana M; Bergh, Erik van den; Zhu, Xinguang; Bouwmeester, Harro J; Schuurink, Robert C; Schranz, M Eric
2015-01-01
An important component of plant evolution is the plethora of pathways producing more than 200,000 biochemically diverse specialized metabolites with pharmacological, nutritional and ecological significance. To unravel dynamics underlying metabolic diversification, it is critical to determine lineage-specific gene family expansion in a phylogenomics framework. However, robust functional annotation is often only available for core enzymes catalyzing committed reaction steps within few model systems. In a genome informatics approach, we extracted information from early-draft gene-space assemblies and non-redundant transcriptomes to identify protein families involved in isoprenoid biosynthesis. Isoprenoids comprise terpenoids with various roles in plant-environment interaction, such as pollinator attraction or pathogen defense. Combining lines of evidence provided by synteny, sequence homology and Hidden-Markov-Modelling, we screened 17 genomes including 12 major crops and found evidence for 1,904 proteins associated with terpenoid biosynthesis. Our terpenoid genes set contains evidence for 840 core terpene-synthases and 338 triterpene-specific synthases. We further identified 190 prenyltransferases, 39 isopentenyl-diphosphate isomerases as well as 278 and 219 proteins involved in mevalonate and methylerithrol pathways, respectively. Assessing the impact of gene and genome duplication to lineage-specific terpenoid pathway expansion, we illustrated key events underlying terpenoid metabolic diversification within 250 million years of flowering plant radiation. By quantifying Angiosperm-wide versatility and phylogenetic relationships of pleiotropic gene families in terpenoid modular pathways, our analysis offers significant insight into evolutionary dynamics underlying diversification of plant secondary metabolism. Furthermore, our data provide a blueprint for future efforts to identify and more rapidly clone terpenoid biosynthetic genes from any plant species.
Weaver, A. S.; Funk, J. H.; Funk, N. W.; Sheehan, C. C.; Humphreys, B. T.; Perusek, G. P.
2015-01-01
Long-duration space flight poses many hazards to the health of the crew. Among those hazards is the physiological deconditioning of the musculoskeletal and cardiovascular systems due to prolonged exposure to microgravity. To combat this erosion of physical condition space flight may take on the crew, the Human Research Program (HRP) is charged with developing Advanced Exercise Concepts to maintain astronaut health and fitness during long-term missions, while keeping device mass, power, and volume to a minimum. The goal of this effort is to preserve the physical capability of the crew to perform mission critical tasks in transit and during planetary surface operations. The HULK is a pneumatic-based exercise system, which provides both resistive and aerobic modes to protect against human deconditioning in microgravity. Its design targeted the International Space Station (ISS) Advanced Resistive Exercise Device (ARED) high level performance characteristics and provides up to 600 foot pounds resitive loading with the capability to allow for eccentric to concentric (E:C) ratios of higher than 1:1 through a DC motor assist component. The device's rowing mode allows for high cadence aerobic activity. The HULK parabolic flight campaign, conducted through the NASA Flight Opportunities Program at Ellington Field, resulted in the creation of device specific data sets including low fidelity motion capture, accelerometry and both inline and ground reaction forces. These data provide a critical link in understanding how to vibration isolate the device in both ISS and space transit applications. Secondarily, the study of human exercise and associated body kinematics in microgravity allows for more complete understanding of human to machine interface designs to allow for maximum functionality of the device in microgravity.
Design, manufacturing and installation of a new 100 m (L) solar parabolic collector in Shiraz, Iran
Azizian, Kian; Yaghoubi, Mahmood; Hessami, Reza
2017-06-01
After successful design and test of Shiraz 250 kW parabolic trough solar pilot plant it was decided to develop a commercial scale new parabolic trough collector. In this paper the process of basic and detail design, assumptions and also models used for optimal design will be discussed. Manufacturing of collector and installation of its' several parts and future activities will be presented.
Directory of Open Access Journals (Sweden)
Cervellino Juan C.
2003-01-01
Full Text Available OBJECTIVE: The National Institute of Social Services for Retirees and Pensioners (NISSRP is a nationwide health care financing agency and service provider in Argentina. Among its services, the NISSRP provides outpatient drug coverage to more than 3.3 million beneficiaries, mainly senior citizens and disabled persons. In 1997, to help cope with its rising costs, the NISSRP agreed to transfer the risk for the cost of outpatient medications and cancer-treatment drugs to a consortium of pharmaceutical companies in exchange for a fixed monthly payment. The objective of this study was to determine the impact that this new approach had on three things: (1 the level of expenditures for the medicines that were included in the agreement, (2 the pattern of nonrational prescribing for NISSRP beneficiaries, and (3 this pattern's relationship with macroeconomic variables and the pattern of prescribing for Argentina as a whole. METHODS: We compared outpatient-medicine consumption in 1999 with consumption before the agreement went into effect. RESULTS: The actual amount that NISSRP beneficiaries spent out-of-pocket climbed from US$ 336.13 million in 1996 to US$ 473.36 million in 1999, an increase of almost 41%. The nominal amount "spent" by the NISSRP in 1999 was US$ 601.11 million, versus a real amount of US$ 374.75 million in 1996, an "increase" of 60% (that increase for the NISSRP was only theoretical since the agreement specified the fixed monthly amount that the NISSRP would have to pay to the pharmaceutical consortium. In contrast with the increased real spending by NISSRP beneficiaries, Argentina's economy remained stable over the assessed period, with the consumer price index even falling by 0.8%. We found high levels of nonrational drug use in the NISSRP system in both 1996 and 1999, indicating a serious ongoing problem. CONCLUSIONS: An agreement with pharmaceutical companies, like the one we have described, might add an element of financial
Cui, Lei; Tong, Fei-Fei; Shi, Feng
2011-09-01
Researches on breaking-induced currents by waves are summarized firstly in this paper. Then, a combined numerical model in orthogonal curvilinear coordinates is presented to simulate wave-induced current in areas with curved boundary or irregular coastline. The proposed wave-induced current model includes a nearshore current module established through orthogonal curvilinear transformation form of shallow water equations and a wave module based on the curvilinear parabolic approximation wave equation. The wave module actually serves as the driving force to provide the current module with required radiation stresses. The Crank-Nicolson finite difference scheme and the alternating directions implicit method are used to solve the wave and current module, respectively. The established surf zone currents model is validated by two numerical experiments about longshore currents and rip currents in basins with rip channel and breakwater. The numerical results are compared with the measured data and published numerical results.
Spooner, Brian S.; Guikema, James A.; Barnes, Grady
1990-01-01
Alpha-fetoprotein (AFP), a single-chain polypeptide which is synthesized by the liver and yolk sac of the human fetus, provided a model ligand for assessing the effects of microgravity on ligand binding to surface-immobilized model receptor molecules. Monoclonal antibodies, used as receptors for AFP, were immobilized by covalent attachment to latex microparticles. Zero gravity environment was obtained by parabolic flight aboard NASA 930, a modified KC-135 aircraft. Buring the onset of an episode of zero gravity, ligand and receptor were mixed. Timed incubation (20 s) was terminated by centrifugation, the supernatant removed, and microparticies were assessed for bound AFP by immunochemical methods. The extent of binding was not influenced by microgravity, when compared with 1-G controls, which suggests that aberrant cellular activities observed in microgravity are not the simple expression of altered macromolecular interactions.
Fast Time and Space Parallel Algorithms for Solution of Parabolic Partial Differential Equations
Fijany, Amir
1993-01-01
In this paper, fast time- and Space -Parallel agorithms for solution of linear parabolic PDEs are developed. It is shown that the seemingly strictly serial iterations of the time-stepping procedure for solution of the problem can be completed decoupled.
Analysis of the stress-deformed condition of the disassembly parabolic antenna
Odinets, M. N.; Kaygorodtseva, N. V.; Krysova, I. V.
2018-01-01
Active development of satellite communications and computer-aided design systems raises the problem of designing parabolic antennas on a new round of development. The aim of the work was to investigate the influence of the design of the mirror of a parabolic antenna on its endurance under wind load. The research task was an automated analysis of the stress-deformed condition of various designs of computer models of a paraboloid mirror (segmented or holistic) at modeling the exploitation conditions. The peculiarity of the research was that the assembly model of the antenna’s mirror was subjected to rigid connections on the contacting surfaces of the segments and only then the finite element grid was generated. The analysis showed the advantage of the design of the demountable antenna, which consists of cyclic segments, in front of the construction of the holistic antenna. Calculation of the stress-deformed condition of the antennas allows us to conclude that dividing the design of the antenna’s mirror on parabolic and cyclic segments increases it strength and rigidity. In the future, this can be used to minimize the mass of antenna and the dimensions of the disassembled antenna. The presented way of modeling a mirror of a parabolic antenna using to the method of the finite-element analysis can be used in the production of antennas.
Recent Progress in the Development and Application of the Parabolic Equation
1984-05-07
difficulty by using a very snmall step size. According to Henrici [3], the selection of the step size to satisfy the corrector’s convergence is such that Ar...Difference Computer Model for Solving the Parabolic Equation, NUSC Technical Report 6659 (1982). - " 3. P. Henrici , Oiscrete Variable Methods in
Lashmet, P. K.; Woodrow, P. T.
1975-01-01
Numerical instabilities often arise in the use of high-ordered collocation approximations for numerically solving parabolic partial differential equations. These problems may be reduced by formulations involving evaluation of collocation polynomials rather than combination of the polynomials into a power series. As an illustration, two formulations using shifted Legendre polynomials of order 26 and less are compared.
Giriraj MEHTI
2017-01-01
Aim of the paper is to obtain solution of parabolic, elliptical and coupled partial differential equation using Reduced Differential Transform Method (RDTM). The results are compared with solution obtained by other methods. It is observed that RDTM is easy to implement, accurate and efficient. It reduces volume of computation and save time.
Directory of Open Access Journals (Sweden)
Giriraj MEHTI
2017-04-01
Full Text Available Aim of the paper is to obtain solution of parabolic, elliptical and coupled partial differential equation using Reduced Differential Transform Method (RDTM. The results are compared with solution obtained by other methods. It is observed that RDTM is easy to implement, accurate and efficient. It reduces volume of computation and save time.
Discrete nonnegativity for nonlinear cooperative parabolic PDE systems with non-monotone coupling
Faragó I.; Karátson J.; Korotov S
2013-01-01
Discrete nonnegativity principles are established for finite element approximations of nonlinear parabolic PDE systems with mixed boundary conditions. Previous results of the authors are extended such that diagonal dominance (or essentially monotonicity) of the nonlinear coupling can be relaxed, allowing to include much more general situations in suitable models. © 2016 International Association for Mathematics and Computers in Simulation (IMACS).
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I. D. Pukalskiy
2014-12-01
Full Text Available By application of maximum principle and apriori estimates it is studied the inclined derivative problem for a linear parabolic equation with power singularity in the coefficients with respect to space variables and impulse conditions respect to time variable. It is established the uniqueness and the existence of the solution of the stated problem in Holder spaces.
On the Finite Volume Element Method for Self-Adjoint Parabolic Integrodifferential Equations
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Mohamed Bahaj
2013-01-01
Full Text Available Finite volume element schemes for non-self-adjoint parabolic integrodifferential equations are derived and stated. For the spatially discrete scheme, optimal-order error estimates in , , and , norms for are obtained. In this paper, we also study the lumped mass modification. Based on the Crank-Nicolson method, a time discretization scheme is discussed and related error estimates are derived.
Inverse Problems for a Parabolic Integrodifferential Equation in a Convolutional Weak Form
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Kairi Kasemets
2013-01-01
Full Text Available We deduce formulas for the Fréchet derivatives of cost functionals of several inverse problems for a parabolic integrodifferential equation in a weak formulation. The method consists in the application of an integrated convolutional form of the weak problem and all computations are implemented in regular Sobolev spaces.
Simple Verification of the Parabolic Shape of a Rotating Liquid and a Boat on Its Surface
Sabatka, Z.; Dvorak, L.
2010-01-01
This article describes a simple and inexpensive way to create and to verify the parabolic surface of a rotating liquid. The liquid is water. The second part of the article deals with the problem of a boat on the surface of a rotating liquid. (Contains 1 table, 10 figures and 5 footnotes.)
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Mykola Bokalo
2017-03-01
Full Text Available We consider an optimal control problem for systems described by a Fourier problem for parabolic equations. We prove the existence of solutions, and obtain necessary conditions of the optimal control in the case of final observation when the control functions occur in the coefficients.
DEFF Research Database (Denmark)
Hassan, Hafeez Ul; Janting, Jakob; Aasmul, Soren
2016-01-01
We present in-vitro sensing of glucose using a newly developed efficient optical fiber glucose sensor based on a Compound Parabolic Concentrator (CPC) tipped polymer optical fiber (POF). A batch of 9 CPC tipped POF sensors with a 35 mm fiber length is shown to have an enhanced fluorescence pickup...
A Concentrator Photovoltaic System Based on a Combination of Prism-Compound Parabolic Concentrators
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Ngoc Hai Vu
2016-08-01
Full Text Available We present a cost-effective concentrating photovoltaic system composed of a prism and a compound parabolic concentrator (P-CPC. In this approach, the primary collector consists of a prism, a solid compound parabolic concentrator (CPC, and a slab waveguide. The prism, which is placed on the input aperture of CPC, directs the incoming sunlight beam to be parallel with the main axes of parabolic rims of CPC. Then, the sunlight is reflected at the parabolic rims and concentrated at the focal point of these parabolas. A slab waveguide is coupled at the output aperture of the CPC to collect focused sunlight beams and to guide them to the solar cell. The optical system was modeled and simulated with commercial ray tracing software (LightTools™. Simulation results show that the optical efficiency of a P-CPC can achieve up to 89%. when the concentration ratio of the P-CPC is fixed at 50. We also determine an optimal geometric structure of P-CPC based on simulation. Because of the simplicity of the P-CPC structure, a lower-cost mass production process is possible. A simulation based on optimal structure of P-CPC was performed and the results also shown that P-CPC has high angular tolerance for input sunlight. The high tolerance of the input angle of sunlight allows P-CPC solar concentrator utilize a single sun tracking system instead of a highly precise dual suntracking system as cost effective solution.
Comparison of resonant tunneling in AlGaAs/GaAs parabolic and ...
Indian Academy of Sciences (India)
quantum well is fabricated by annealing rectangular quantum well (RQW) under suitable conditions [7–10]. Since the pioneering work of Tsu and Esaki [11], the ... have been a few attempts to study this in the parabolic quantum well (PQW) and triangular ... where L =L1 +2L2 and F =Va/L with Va being the applied voltage.
Stability of Difference Schemes for Fractional Parabolic PDE with the Dirichlet-Neumann Conditions
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Zafer Cakir
2012-01-01
boundary conditions are presented. Stability estimates and almost coercive stability estimates with ln (1/(+|ℎ| for the solution of these difference schemes are obtained. A procedure of modified Gauss elimination method is used for solving these difference schemes of one-dimensional fractional parabolic partial differential equations.
L^p-continuity of solutions to parabolic free boundary problems
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Abdeslem Lyaghfouri
2015-07-01
Full Text Available In this article, we consider a class of parabolic free boundary problems. We establish some properties of the solutions, including L^infinity-regularity in time and a monotonicity property, from which we deduce strong L^p-continuity in time.
Energy Technology Data Exchange (ETDEWEB)
Davenport, C. M.
1977-02-01
The mathematical basis for an ultraprecise digital differential analyzer circuit for use as a parabolic interpolator on numerically controlled machines has been established, and scaling and other error-reduction techniques have been developed. An exact computer model is included, along with typical results showing tracking to within an accuracy of one part per million.
Riemann integral of a random function and the parabolic equation with a general stochastic measure
Radchenko, Vadym
2012-01-01
For stochastic parabolic equation driven by a general stochastic measure, the weak solution is obtained. The integral of a random function in the equation is considered as a limit in probability of Riemann integral sums. Basic properties of such integrals are studied in the paper.
Veestraeten, D.
2015-01-01
The Laplace transforms of the transition probability density and distribution functions for the Ornstein-Uhlenbeck process contain the product of two parabolic cylinder functions, namely Dv(x)Dv(y) and Dv(x)Dv−1(y), respectively. The inverse transforms of these products have as yet not been
A Note on the Blow-up Pattern for a Parabolic Equation
Kohda, Atsuhito; Suzuki, Takashi
1999-01-01
We consider here some conditions on initial value for parabolic problem which guarantee the blow-up of a solution. Then we study the behaviour of blow-up solution near blow-up time, that is blow-up patterns.
Blow-Up and Global Existence for a Quasilinear Parabolic System
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Chunchen Wu
2014-01-01
Full Text Available The problem of solutions to a class of quasilinear coupling parabolic system was studied. By constructing weak upper-solutions and weak lower-solutions, we obtain the global existence and blow-up of solutions under appropriate conditions.
Asymptotic behavior of solutions to a degenerate quasilinear parabolic equation with a gradient term
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Huilai Li
2015-12-01
Full Text Available This article concerns the asymptotic behavior of solutions to the Cauchy problem of a degenerate quasilinear parabolic equations with a gradient term. A blow-up theorem of Fujita type is established and the critical Fujita exponent is formulated by the spacial dimension and the behavior of the coefficient of the gradient term at infinity.
Global existence and finite time blow-up for a parabolic system on hyperbolic space
Wu, Hui; Yang, Xiaoping
2018-01-01
In this paper, we study the global existence and finite time blow-up of positive solutions for a parabolic system on hyperbolic space. Using the heat semigroup and constructing subsolutions and supersolutions, we obtain the Fujita type results. In the case of a critical exponent, the critical exponent is not a blow-up exponent.
Nonlocal singular problem with integral condition for a second-order parabolic equation
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Ahmed Lakhdar Marhoune
2015-03-01
Full Text Available We prove the existence and uniqueness of a strong solution for a parabolic singular equation in which we combine Dirichlet with integral boundary conditions given only on parts of the boundary. The proof uses a priori estimate and the density of the range of the operator generated by the problem considered.
On the Compactness of the Commutator of the Parabolic Marcinkiewicz Integral with Variable Kernel
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Yanping Chen
2014-01-01
Full Text Available The authors prove that the commutator of the parabolic Marcinkiewicz integral gΩ with variable kernel is a compact operator on Lp(Rn (1
Time-optimal control of infinite order distributed parabolic systems involving time lags
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G.M. Bahaa
2014-06-01
Full Text Available A time-optimal control problem for linear infinite order distributed parabolic systems involving constant time lags appear both in the state equation and in the boundary condition is presented. Some particular properties of the optimal control are discussed.
High-order time-accurate schemes for parabolic singular perturbation problems with convection
P.W. Hemker (Piet); G.I. Shishkin (Gregori); L.P. Shishkina
2001-01-01
textabstractWe consider the first boundary value problem for a singularly perturbed para-bo-lic PDE with convection on an interval. For the case of sufficiently smooth data, it is easy to construct a standard finite difference operator and a piecewise uniform mesh, condensing in the boundary layer,
Stability of entropy solutions for Levy mixed hyperbolic-parabolic equations
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Kenneth H. Karlsen
2011-09-01
Full Text Available We analyze entropy solutions for a class of Levy mixed hyperbolic-parabolic equations containing a non-local (or fractional diffusion operator originating from a pure jump Levy process. For these solutions we establish uniqueness (L^1 contraction property and continuous dependence results.
On basin of zero-solutions to a semilinear parabolic equation with Ornstein-Uhlenbeck operator
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Fujita Yasuhiro
2006-01-01
Full Text Available We consider the basin of the zero-solution to a semilinear parabolic equation on with the Ornstein-Uhlenbeck operator. Our aim is to show that the Ornstein-Uhlenbeck operator contributes to enlargement of the basin by using the logarithmic Sobolev inequality.
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A.H. Qamlo
2014-04-01
Full Text Available In this paper, we study the existence of a solution to n × n parabolic systems with variable coefficients involving Schrödinger operators defined on an unbounded domain of Rn. We then discuss the necessary and sufficient conditions of optimality for these systems.
The Nehari problem for infinite-dimensional linear systems of parabolic type
Curtain, RF; Ichikawa, A
A complete solution is obtained to the suboptimal Nehari extension problem for transfer functions of parabolic systems with Dirichlet boundary control and smooth observations. The solutions are given in terms of the realization (-A, B, C), where A is a uniformly strongly elliptic operator of order
Galerkin. methods for even-order parabolic. equations in one space variable
M. Bakker (Miente)
1982-01-01
textabstractFor parabolic equations in one space variable with a strongly coercive self-adjoint $2m$th order spatial operator, a $k$th degree Faedo-Galerkin method is developed which has local convergence of order $2(k + 1 - m)$ at the knots for the first $m - 1$ spatial derivatives and, if $k \\geqq
Existence of Renormalized Solutions for p(x-Parabolic Equation with three unbounded nonlinearities
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Youssef Akdim
2016-04-01
Full Text Available In this article, we study the existence of renormalized solution for the nonlinear $p(x$-parabolic problem of the form:\\\\ $\\begin{cases} \\frac{\\partial b(x,u}{\\partial t} - div (a(x,t,u,\
On the Ext algebras of parabolic Verma modules and A infinity-structures
DEFF Research Database (Denmark)
Klamt, Angela; Stroppel, Catharina
2012-01-01
We study the Ext-algebra of the direct sum of all parabolic Verma modules in the principal block of the Bernstein–Gelfand–Gelfand category O for the Hermitian symmetric pair (gln+m,gln¿glm) and present the corresponding quiver with relations for the cases n=1,2. The Kazhdan–Lusztig combinatorics ...
Algorithm 850: Real parabolic cylinder functions U(a,x), V(a,x)
A. Gil (Amparo); J. Segura (Javier); N.M. Temme (Nico)
2006-01-01
textabstractFortran 90 programs for the computation of real parabolic cylinder functions are presented. The code computes the functions U(a, x), V (a, x) and their derivatives for real a and $x(xgeq 0)$. The code also computes scaled functions. The range of computation for scaled PCFs is practically
Algorithm 914: Parabolic Cylinder Function $W(a,x)$ and its Derivative
A. Gil (Amparo); J. Segura (Javier); N.M. Temme (Nico)
2011-01-01
textabstractA Fortran 90 program for the computation of the real parabolic cylinder functions $W(a,\\pm x),\\,\\,x\\ge 0$ and their derivatives is presented. The code also computes scaled functions for $a>50$. The functions $W(a,\\pm x)$ are a numerically satisfactory pair of solutions of the
Sensor for measuring hydrogen partial pressure in parabolic trough power plant expansion tanks
Glatzmaier, Greg C.; Cooney, Daniel A.
2017-06-01
The National Renewable Energy Laboratory and Acciona Energy North America are working together to design and implement a process system that provides a permanent solution to the issue of hydrogen buildup at parabolic trough power plants. We are pursuing a method that selectively removes hydrogen from the expansion tanks that serve as reservoirs for the heat transfer fluid (HTF) that circulates in the collector field and power block components. Our modeling shows that removing hydrogen from the expansion tanks at a design rate reduces and maintains dissolved hydrogen in the circulating HTF to a selected target level. Our collaborative work consists of several tasks that are needed to advance this process concept to a development stage, where it is ready for implementation at a commercial power plant. Our main effort is to design and evaluate likely process-unit operations that remove hydrogen from the expansion tanks at a specified rate. Additionally, we designed and demonstrated a method and instrumentation to measure hydrogen partial pressure and concentration in the expansion-tank headspace gas. We measured hydrogen partial pressure in the headspace gas mixture using a palladium-alloy membrane, which is permeable exclusively to hydrogen. The membrane establishes a pure hydrogen gas phase that is in equilibrium with the hydrogen in the gas mixture. We designed and fabricated instrumentation, and demonstrated its effectiveness in measuring hydrogen partial pressures over a range of three orders of magnitude. Our goal is to install this instrument at the Nevada Solar One power plant and to demonstrate its effectiveness in measuring hydrogen levels in the expansion tanks under normal plant operating conditions.
Porous media matric potential and water content measurements during parabolic flight
Norikane, Joey H.; Jones, Scott B.; Steinberg, Susan L.; Levine, Howard G.; Or, Dani
2005-01-01
Control of water and air in the root zone of plants remains a challenge in the microgravity environment of space. Due to limited flight opportunities, research aimed at resolving microgravity porous media fluid dynamics must often be conducted on Earth. The NASA KC-135 reduced gravity flight program offers an opportunity for Earth-based researchers to study physical processes in a variable gravity environment. The objectives of this study were to obtain measurements of water content and matric potential during the parabolic profile flown by the KC-135 aircraft. The flight profile provided 20-25 s of microgravity at the top of the parabola, while pulling 1.8 g at the bottom. The soil moisture sensors (Temperature and Moisture Acquisition System: Orbital Technologies, Madison, WI) used a heat-pulse method to indirectly estimate water content from heat dissipation. Tensiometers were constructed using a stainless steel porous cup with a pressure transducer and were used to measure the matric potential of the medium. The two types of sensors were placed at different depths in a substrate compartment filled with 1-2 mm Turface (calcined clay). The ability of the heat-pulse sensors to monitor overall changes in water content in the substrate compartment decreased with water content. Differences in measured water content data recorded at 0, 1, and 1.8 g were not significant. Tensiometer readings tracked pressure differences due to the hydrostatic force changes with variable gravity. The readings may have been affected by changes in cabin air pressure that occurred during each parabola. Tensiometer porous membrane conductivity (function of pore size) and fluid volume both influence response time. Porous media sample height and water content influence time-to-equilibrium, where shorter samples and higher water content achieve faster equilibrium. Further testing is needed to develop these sensors for space flight applications.
Comparative Modeling of a Parabolic Trough Collectors Solar Power Plant with MARS Models
Directory of Open Access Journals (Sweden)
Jose Ramón Rogada
2017-12-01
Full Text Available Power plants producing energy through solar fields use a heat transfer fluid that lends itself to be influenced and changed by different variables. In solar power plants, a heat transfer fluid (HTF is used to transfer the thermal energy of solar radiation through parabolic collectors to a water vapor Rankine cycle. In this way, a turbine is driven that produces electricity when coupled to an electric generator. These plants have a heat transfer system that converts the solar radiation into heat through a HTF, and transfers that thermal energy to the water vapor heat exchangers. The best possible performance in the Rankine cycle, and therefore in the thermal plant, is obtained when the HTF reaches its maximum temperature when leaving the solar field (SF. In addition, it is necessary that the HTF does not exceed its own maximum operating temperature, above which it degrades. The optimum temperature of the HTF is difficult to obtain, since the working conditions of the plant can change abruptly from moment to moment. Guaranteeing that this HTF operates at its optimal temperature to produce electricity through a Rankine cycle is a priority. The oil flowing through the solar field has the disadvantage of having a thermal limit. Therefore, this research focuses on trying to make sure that this fluid comes out of the solar field with the highest possible temperature. Modeling using data mining is revealed as an important tool for forecasting the performance of this kind of power plant. The purpose of this document is to provide a model that can be used to optimize the temperature control of the fluid without interfering with the normal operation of the plant. The results obtained with this model should be necessarily contrasted with those obtained in a real plant. Initially, we compare the PID (proportional–integral–derivative models used in previous studies for the optimization of this type of plant with modeling using the multivariate adaptive
Sensor for Measuring Hydrogen Partial Pressure in Parabolic Trough Power Plant Expansion Tanks
Energy Technology Data Exchange (ETDEWEB)
Glatzmaier, Greg C.; Cooney, Daniel A.
2017-06-27
The National Renewable Energy Laboratory and Acciona Energy North America are working together to design and implement a process system that provides a permanent solution to the issue of hydrogen buildup at parabolic trough power plants. We are pursuing a method that selectively removes hydrogen from the expansion tanks that serve as reservoirs for the heat transfer fluid (HTF) that circulates in the collector field and power block components. Our modeling shows that removing hydrogen from the expansion tanks at a design rate reduces and maintains dissolved hydrogen in the circulating HTF to a selected target level. Our collaborative work consists of several tasks that are needed to advance this process concept to a development stage, where it is ready for implementation at a commercial power plant. Our main effort is to design and evaluate likely process-unit operations that remove hydrogen from the expansion tanks at a specified rate. Additionally, we designed and demonstrated a method and instrumentation to measure hydrogen partial pressure and concentration in the expansion-tank headspace gas. We measured hydrogen partial pressure in the headspace gas mixture using a palladium-alloy membrane, which is permeable exclusively to hydrogen. The membrane establishes a pure hydrogen gas phase that is in equilibrium with the hydrogen in the gas mixture. We designed and fabricated instrumentation, and demonstrated its effectiveness in measuring hydrogen partial pressures over a range of three orders of magnitude. Our goal is to install this instrument at the Nevada Solar One power plant and to demonstrate its effectiveness in measuring hydrogen levels in the expansion tanks under normal plant operating conditions.
Schneider, Stefan; Brümmer, Vera; Mierau, Andreas; Carnahan, Heather; Dubrowski, Adam; Strüder, Heiko K
2008-03-01
Previous studies showed that changing forces of gravity as they typically occur during parabolic flights might be responsible for adaptional processes of the CNS. However, until now it has not been differentiated between primary influences of weightlessness and secondary influences due to psycho-physiological factors (e.g., physical or mental strain). With the aim of detecting parabolic flight related changes in central cortical activity, a resting EEG was deduced in 16 subjects before, during and after parabolic flights. After subdividing EEG into alpha-, beta-,delta- and theta-wave bands, an increase in beta-power was noticeable inflight, whereas alpha(1)-power was increased postflight. No changes could be observed for the control group. To control possible effects of cortical activation, a manual tracking task with mirror inversion was performed during either the phase of weightlessness or during the normal gravity phase of a parabolic flight. No differences in performance nor in adaptation could be observed between both groups. A third group, performing under normal and stress-free conditions in a lab showed similar tracking values. We assume that the specific increase in brain activity is a sign of an increase in arousal inflight. This does support previous assumptions of non-specific stressors during parabolic flights and has to be considered as a relevant factor for experiments on central nerve adaptation. Although no influences of stress and/or weightlessness on motor performance and adaptation could be observed, we suggest that an "inflight" control group seems to be more adequate than a laboratory control group to investigate gravity-dependent changes in motor control.
GOSWAMI, DEEPJYOTI
2014-01-01
AWe propose and analyse an alternate approach to a priori error estimates for the semidiscrete Galerkin approximation to a time-dependent parabolic integro-differential equation with nonsmooth initial data. The method is based on energy arguments combined with repeated use of time integration, but without using parabolic-type duality techniques. An optimal L2-error estimate is derived for the semidiscrete approximation when the initial data is in L2. A superconvergence result is obtained and then used to prove a maximum norm estimate for parabolic integro-differential equations defined on a two-dimensional bounded domain. © 2014 Australian Mathematical Society.
Medicare Provider Data - Hospice Providers
U.S. Department of Health & Human Services — The Hospice Utilization and Payment Public Use File provides information on services provided to Medicare beneficiaries by hospice providers. The Hospice PUF...
Calculated scan characteristics of a large spherical reflector antenna
Agrawal, P. K.; Croswell, W. F.; Kauffman, J. F.
1979-01-01
A previously published numerical method to calculate the radiation properties of parabolic reflectors has been modified to also include very large spherical reflectors. The method has been verified by comparing the calculated and the measured results for a 120-wavelength spherical reflector.
Directory of Open Access Journals (Sweden)
Bakhtiyor Kadirkulov
2014-02-01
Full Text Available In this article, we study a boundary value problem for a parabolic-hyperbolic equation with Caputo fractional derivative. Under certain conditions, we prove its unique solvability using methods of integral equations and Green's functions.
A 3D Parabolic Equation (PE) Based Technique for Predicting Propagation Path Loss in an Urban Area
National Research Council Canada - National Science Library
Thiem, Keem
2001-01-01
.... The PE method offers the computational advantages, where one can approximate the elliptic operator governing the true wave behavior by a much simpler parabolic operator that permits marching in range...
The Analytical Solution of Parabolic Volterra Integro-Differential Equations in the Infinite Domain
Directory of Open Access Journals (Sweden)
Yun Zhao
2016-09-01
Full Text Available This article focuses on obtaining analytical solutions for d-dimensional, parabolic Volterra integro-differential equations with different types of frictional memory kernel. Based on Laplace transform and Fourier transform theories, the properties of the Fox-H function and convolution theorem, analytical solutions for the equations in the infinite domain are derived under three frictional memory kernel functions. The analytical solutions are expressed by infinite series, the generalized multi-parameter Mittag-Leffler function, the Fox-H function and the convolution form of the Fourier transform. In addition, graphical representations of the analytical solution under different parameters are given for one-dimensional parabolic Volterra integro-differential equations with a power-law memory kernel. It can be seen that the solution curves are subject to Gaussian decay at any given moment.
Directory of Open Access Journals (Sweden)
T. E. Boukelia
2016-05-01
Full Text Available The Parabolic trough solar collector is considered as one of the most proven, mature and commercial concentrating solar systems implemented in arid and semi-arid regions for energy production. It focuses sunlight onto a solar receiver by using mirrors and is finally converted to a useful thermal energy by means of a heat transfer fluid. The aims of this study are (i to develop a new methodology for simulation and performance evaluation of parabolic trough solar collector, in addition (i to compare the efficiencies of this system using two different fluids; thermic oil and molten solar salt. The validation of obtained results using this methodology shows a good agreement with those obtained by the experimental tests. Furthermore, this study favors the using of thermic oil as heat transfer fluid in the receiver instead of molten salt due to the high efficiency of the concentrator based on the first fluid in comparison to the second one.
Heat Loss Testing of Schott's 2008 PTR70 Parabolic Trough Receiver
Energy Technology Data Exchange (ETDEWEB)
Burkholder, Frank [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kutscher, Chuck [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2009-05-01
Two Schott 2008 model year PTR70 HCEs were tested on NREL's heat loss test stand from 100 - 500 deg C in 50 deg C increments. Absorber emittance was determined from the laboratory testing so that the performance of the HCEs could be modeled in a parabolic trough collector. Collector/HCE simulation results for many different field operation conditions were used to create heat loss correlationcoefficients for Excelergy and SAM. SAM estimates that the decreased emittance of the 2008 PTR70 will decrease the LCOE for parabolic trough power plants by 0.5 cents/kWh and increase the electricity generated by 5% relative to previous PTR70s. These conclusions assume that the 2008 PTR70 is supplied at the same cost and with the same optical performance as earlier PTR70 models.
A parabolic model to control quantum interference in T-shaped molecular junctions
DEFF Research Database (Denmark)
Nozaki, Daijiro; Sevincli, Haldun; Avdoshenko, Stanislav M.
2013-01-01
Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical...... to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal...... resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group...
Well-Posedness of Nonlocal Parabolic Differential Problems with Dependent Operators
Directory of Open Access Journals (Sweden)
Allaberen Ashyralyev
2014-01-01
Full Text Available The nonlocal boundary value problem for the parabolic differential equation v'(t+A(tv(t=f(t (0≤t≤T, v(0=v(λ+φ, 0<λ≤T in an arbitrary Banach space E with the dependent linear positive operator A(t is investigated. The well-posedness of this problem is established in Banach spaces C0β,γ(Eα-β of all Eα-β-valued continuous functions φ(t on [0,T] satisfying a Hölder condition with a weight (t+τγ. New Schauder type exact estimates in Hölder norms for the solution of two nonlocal boundary value problems for parabolic equations with dependent coefficients are established.
Thermal performance of functionally graded parabolic annular fins having constant weight
Energy Technology Data Exchange (ETDEWEB)
Gaba, Vivek Kumar; Tiwari, Anil Kumar; Bhowmick, Shubhankar [National Institute of Technology Raipur, Raipur (India)
2014-10-15
The proposed work reports the performance of parabolic annular fins of constant weight made of functionally graded materials. The work involves computation of temperature gradient, efficiency and effectiveness of such fins and compares the performances for different functionally graded parabolic fin profiles obtained by varying grading parameters and profile parameters respectively keeping the weight of the fins constant. The functional grading of thermal conductivity is based on a power function of radial co-ordinate which consists of parameters, namely grading parameters, varying which different grading combinations are studied. A general second order ordinary differential equation has been derived for all the profiles and material grading. The efficiency and effectiveness of the annular fins of different profile and grading combinations have been calculated and plotted and the results reveal the dependence of fin performance on profile and grading parameter.
Femtosecond laser micromachining of compound parabolic concentrator fiber tipped glucose sensors
DEFF Research Database (Denmark)
Hassan, Hafeez Ul; Lacraz, Amédée; Kalli, Kyriacos
2017-01-01
We report on highly accurate femtosecond (fs) laser micromachining of a compound parabolic concentrator (CPC) fiber tip on a polymer optical fiber (POF). The accuracy is reflected in an unprecedented correspondence between the numerically predicted and experimentally found improvement in fluoresc......We report on highly accurate femtosecond (fs) laser micromachining of a compound parabolic concentrator (CPC) fiber tip on a polymer optical fiber (POF). The accuracy is reflected in an unprecedented correspondence between the numerically predicted and experimentally found improvement...... in fluorescence pickup efficiency of a Förster resonance energy transfer-based POF glucose sensor. A Zemax model of the CPC-tipped sensor predicts an optimal improvement of a factor of 3.96 compared to the sensor with a plane-cut fiber tip. The fs laser micromachined CPC tip showed an increase of a factor of 3...
Self-Fourier transform and self-Fourier beams due to parabolic potential
Zhang, Yiqi; Zhong, Weiping; Zhang, Yanpeng
2014-01-01
We theoretically and numerically investigate the propagation of light beams including Hermite-Gaussian, Bessel-Gaussian and finite energy Airy beams in free space with parabolic potential. Expectedly, the beams undergo harmonic oscillation during propagation, but quite unexpectedly they also perform self-Fourier transform, that is, periodic change from the beam to its Fourier transform and back. The oscillating period of parity-asymmetric beams is twice that of the parity-symmetric beams. In addition to oscillation, we find that finite-energy Airy beams exhibit periodic inversion during propagation. Based on the parabolic potential, we introduce a class of optically-interesting beams that are self-Fourier beams, i.e., the corresponding Fourier transforms are themselves. We outline interesting venues for future research.
On explicit and numerical solvability of parabolic initial-boundary value problems
Directory of Open Access Journals (Sweden)
Lepsky Olga
2006-01-01
Full Text Available A homogeneous boundary condition is constructed for the parabolic equation in an arbitrary cylindrical domain ( being a bounded domain, and being the identity operator and the Laplacian which generates an initial-boundary value problem with an explicit formula of the solution . In the paper, the result is obtained not just for the operator , but also for an arbitrary parabolic differential operator , where is an elliptic operator in of an even order with constant coefficients. As an application, the usual Cauchy-Dirichlet boundary value problem for the homogeneous equation in is reduced to an integral equation in a thin lateral boundary layer. An approximate solution to the integral equation generates a rather simple numerical algorithm called boundary layer element method which solves the 3D Cauchy-Dirichlet problem (with three spatial variables.
Spectral Deferred Corrections for Parabolic Partial Differential Equations
2015-06-08
time, and therefore, requires an implicit method for its solution. Spectral Deferred Correction ( SDC ) methods use repeated iterations of a low-order...method (e.g. im- plicit Euler method) to generate a high-order scheme. As a result, SDC methods of arbitrary order can be constructed with the desired...stability properties necessary for the solution of stiff differential equations. Furthermore, for large-scale systems, SDC methods are more
Guan, Chao; Hasi, Eerdun; Zhang, Ping; Tao, Binbin; Liu, Dan; Zhou, Yanguang
2017-10-01
Since the 1970s, parabolic dunes at the southern fringe of the Hobq Desert, Inner Mongolia, China have exhibited many different shapes (V-shaped, U-shaped, and palmate) each with a unique mode of development. In the study area, parabolic dunes are mainly distributed in Regions A, B, and C with an intermittent river running from the south to the north. We used high-resolution remote-sensing images from 1970 to 2014 and RTK-GPS measurements to study the development modes of different dune shapes; the modes are characterized by the relationship between the intermittent river and dunes, formation of the incipient dune patterns, the predominant source supply of dunes, and the primary formation of different shapes (V-shaped, U-shaped, and palmate). Most parabolic dunes in Region A are V-shaped and closer to the bank of the river. The original barchans in this region exhibit "disconnected arms" behavior. With the sand blown out of the riverbed through gullies, the nebkhas on the disconnected arms acquire the external sand source through the "fertile island effect", thereby developing into triangular sand patches and further developing into V-shaped parabolic dunes. Most parabolic dunes in Regions B and C are palmate. The residual dunes cut by the re-channelization of river from transverse dune fields on the west bank are the main sand source of Region B. The parabolic dunes in Region C are the original barchans having then been transformed. The stoss slopes of V-shaped parabolic dunes along the riverbank are gradual and the dunes are flat in shape. The dune crest of V-shaped parabolic dune is the deposition area, which forms the "arc-shaped sand ridge". Their two arms are non-parallel; the lateral airflow of the arms jointly transport sand to the middle part of dunes, resulting in a narrower triangle that gradually becomes V-shaped. Palmate parabolic dunes have a steeper stoss slope and height. The dune crest of the palmate parabolic dune is the erosion area, which forms
The flow of an incompressible electroconductive fluid past a thin airfoil. The parabolic profile
Directory of Open Access Journals (Sweden)
Adrian CARABINEANU
2014-04-01
Full Text Available We study the two-dimensional steady flow of an ideal incompressible perfectly conducting fluid past an insulating thin parabolic airfoil. We consider the linearized Euler and Maxwell equations and Ohm's law. We use the integral representations for the velocity, magnetic induction and pressure and the boundary conditions to obtain an integral equation for the jump of the pressure across the airfoil. We give some graphic representations for the lift coefficient, velocity and magnetic induction.
Band warping, band non-parabolicity, and Dirac points in electronic and lattice structures
Resca, Lorenzo; Mecholsky, Nicholas A.; Pegg, Ian L.
2017-10-01
We illustrate at a fundamental level the physical and mathematical origins of band warping and band non-parabolicity in electronic and vibrational structures. We point out a robust presence of pairs of topologically induced Dirac points in a primitive-rectangular lattice using a p-type tight-binding approximation. We analyze two-dimensional primitive-rectangular and square Bravais lattices with implications that are expected to generalize to more complex structures. Band warping is shown to arise at the onset of a singular transition to a crystal lattice with a larger symmetry group, which allows the possibility of irreducible representations of higher dimensions, hence band degeneracy, at special symmetry points in reciprocal space. Band warping is incompatible with a multi-dimensional Taylor series expansion, whereas band non-parabolicities are associated with multi-dimensional Taylor series expansions to all orders. Still band non-parabolicities may merge into band warping at the onset of a larger symmetry group. Remarkably, while still maintaining a clear connection with that merging, band non-parabolicities may produce pairs of conical intersections at relatively low-symmetry points. Apparently, such conical intersections are robustly maintained by global topology requirements, rather than any local symmetry protection. For two p-type tight-binding bands, we find such pairs of conical intersections drifting along the edges of restricted Brillouin zones of primitive-rectangular Bravais lattices as lattice constants vary relatively to each other, until these conical intersections merge into degenerate warped bands at high-symmetry points at the onset of a square lattice. The conical intersections that we found appear to have similar topological characteristics as Dirac points extensively studied in graphene and other topological insulators, even though our conical intersections have none of the symmetry complexity and protection afforded by the latter more
Hall, Eric Joseph
2013-01-01
First we consider implicit finite difference schemes on uniform grids in time and space for second order linear stochastic partial differential equations of parabolic type. Under sufficient regularity conditions, we prove the existence of an appropriate asymptotic expansion in powers of the the spatial mesh and hence we apply Richardson's method to accelerate the convergence with respect to the spatial approximation to an arbitrarily high order. Then we extend these results to equations where...
High-order evolving surface finite element method for parabolic problems on evolving surfaces
Kovács, Balázs
2016-01-01
High-order spatial discretisations and full discretisations of parabolic partial differential equations on evolving surfaces are studied. We prove convergence of the high-order evolving surface finite element method, by showing high-order versions of geometric approximation errors and perturbation error estimates and by the careful error analysis of a modified Ritz map. Furthermore, convergence of full discretisations using backward difference formulae and implicit Runge-Kutta methods are als...
Lucjan Sapa
2012-01-01
The theorems on the estimates of solutions for nonlinear second-order partial differential functional equations of parabolic type with Dirichlet's condition and for suitable implicit finite difference functional schemes are proved. The proofs are based on the comparison technique. The convergent and stable difference method is considered without the assumption of the global generalized Perron condition posed on the functional variable but with the local one only. It is a consequence of our es...
Gravitactic signal transduction elements in astasia longa investigated during parabolic flights
Richter, Peter R.; Schuster, Martin; Lebert, Michael; Häder, Donat-P.
2003-12-01
Euglena gracilis and its close relative Astasia longa show a pronounced negative gravitactic behavior. Many experiments revealed that gravitaxis is most likely mediated by an active physiological mechanism. The goal of the present study was to examine elements in the sensory transduction by means of inhibitors of gravitaxis and the intracellular calcium concentration during short microgravity periods. During the course of six parabolic flights (ESA 31 th parabolic flight campaign and DLR 6 th parabolic flight campaign) the effects of trifluoperazine (calmodulin inhibitor), caffeine (phosphodiesterase inhibitor) and gadolinium (blocks mechano-sensitive ion channels) was investigated. Due to the extreme parabolic flight maneuvers of the aircraft alternating phases of 1.8×gn (about 20 s) and microgravity (about 22 s) were achieved (gn: acceleration of Earth's gravity field). The duration of the microgravity periods was sufficient to detect a loss of cell orientation in the samples. In the presence of gadolinium impaired gravitaxis was found during acceleration, while caffeine-treated cells showed, compared to the controls, a very precise gravitaxis and faster reorientation in the 1.8×gn period following microgravity. A transient increase of the intracellular calcium upon increased acceleration was detected also in inhibitor-treated samples. Additionally, it was found that the cells showed a higher calcium signal when they deviated from the vertical swimming direction. In the presence of trifluoperazine a slightly higher general calcium signal was detected compared to untreated controls, while gadolinium was found to decrease the intracellular calcium concentration. In the presence of caffeine no clear changes of intracellular calcium were detected compared to the control.
Moving Least Squares Method for a One-Dimensional Parabolic Inverse Problem
Directory of Open Access Journals (Sweden)
Baiyu Wang
2014-01-01
Full Text Available This paper investigates the numerical solution of a class of one-dimensional inverse parabolic problems using the moving least squares approximation; the inverse problem is the determination of an unknown source term depending on time. The collocation method is used for solving the equation; some numerical experiments are presented and discussed to illustrate the stability and high efficiency of the method.
Miguel Ángel Hernández-Román; Alejandro Manzano-Ramírez; Jorge Pineda-Piñón; Jorge Ortega-Moody
2014-01-01
This paper presents a theoretical and practical analysis of the application of the thermoeconomic method. A furnace for heating air is evaluated using the methodology. The furnace works with solar energy, received from a parabolic trough collector and with electricity supplied by an electric power utility. The methodology evaluates the process by the first and second law of thermodynamics as the first step then the cost analysis is applied for getting the thermoeconomic cost. For this study, ...
2006-10-01
equation for sound waves in inhomogeneous moving media”, Acustica united with Acta Acustica , Vol 83(3), pp 455-460,1997. [3] L. Dallois, Ph. Blanc...propagation in a turbulent atmosphere within the parabolic approximation”, Acustica united with Acta Acustica , Vol 87(1), pp 659-669, 2001 [6] M. Karweit...approaches", Acta Acustica united with Acustica , 89 (6), 980-991, (2003). [40] Ph. Voisin, Ph. Blanc-Benon, "The influence of meteorological
Self-similar singular solution of doubly singular parabolic equation with gradient absorption term
Directory of Open Access Journals (Sweden)
Shi Peihu
2006-01-01
Full Text Available We deal with the self-similar singular solution of doubly singular parabolic equation with a gradient absorption term for , and in . By shooting and phase plane methods, we prove that when there exists self-similar singular solution, while there is no any self-similar singular solution. In case of existence, the self-similar singular solution is the self-similar very singular solutions which have compact support. Moreover, the interface relation is obtained.
Energy Technology Data Exchange (ETDEWEB)
Forristall, R.
2003-10-01
This report describes the development, validation, and use of a heat transfer model implemented in Engineering Equation Solver. The model determines the performance of a parabolic trough solar collector's linear receiver, also called a heat collector element. All heat transfer and thermodynamic equations, optical properties, and parameters used in the model are discussed. The modeling assumptions and limitations are also discussed, along with recommendations for model improvement.
Self-Fourier transform and self-Fourier beams due to parabolic potential
Zhang, Yiqi; Liu, Xing; Belić, Milivoj R.; Zhong, Weiping; Petrović, Milan S.; Zhang, Yanpeng
2014-01-01
We investigate the propagation of light beams including Hermite-Gauss, Bessel-Gauss and finite energy Airy beams in a linear medium with parabolic potential. Expectedly, the beams undergo oscillation during propagation, but quite unexpectedly they also perform automatic Fourier transform, that is, periodic change from the beam to its Fourier transform and back. The oscillating period of parity-asymmetric beams is twice that of the parity-symmetric beams. In addition to oscillation, the finite...
Page 1 Parabolic ample bundles – III 45 Now assume that E, is ...
Indian Academy of Sciences (India)
with Galois group G. Proposition 3.2 says that V is numerically flat, i.e., both V and V" are nef. Now Proposition 2.6 says that V is semistable with c1(W) = 0 = cz (V). Since V is semistable, from [Bill it follows that E, is parabolic semistable. Since the first and the second Chern class of V vanish, from [Bi:3] it follows that the first ...
On a third order parabolic equation with a nonlocal boundary condition
Directory of Open Access Journals (Sweden)
Abdelfatah Bouziani
2000-01-01
Full Text Available In this paper we demonstrate the existence, uniqueness and continuous dependence of a strong solution upon the data, for a mixed problem which combine classical boundary conditions and an integral condition, such as the total mass, flux or energy, for a third order parabolic equation. We present a functional analysis method based on an a priori estimate and on the density of the range of the operator generated by the studied problem.
Pullback attractors for non-autonomous parabolic equations involving Grushin operators
Directory of Open Access Journals (Sweden)
Cung The Anh
2010-01-01
Full Text Available Using the asymptotic a priori estimate method, we prove the existence of pullback attractors for a non-autonomous semilinear degenerate parabolic equation involving the Grushin operator in a bounded domain. We assume a polynomial type growth on the nonlinearity, and an exponential growth on the external force. The obtained results extend some existing results for non-autonomous reaction-diffusion equations.
A Boundary Value Problem with Multivariables Integral Type Condition for Parabolic Equations
Directory of Open Access Journals (Sweden)
A. L. Marhoune
2009-01-01
Full Text Available We study a boundary value problem with multivariables integral type condition for a class of parabolic equations. We prove the existence, uniqueness, and continuous dependence of the solution upon the data in the functional wieghted Sobolev spaces. Results are obtained by using a functional analysis method based on two-sided a priori estimates and on the density of the range of the linear operator generated by the considered problem.
Existence of solutions to nonlinear parabolic unilateral problems with an obstacle depending on time
Directory of Open Access Journals (Sweden)
Nabila Bellal
2014-10-01
Full Text Available Using the penalty method, we prove the existence of solutions to nonlinear parabolic unilateral problems with an obstacle depending on time. To find a solution, the original inequality is transformed into an equality by adding a positive function on the right-hand side and a complementary condition. This result can be seen as a generalization of the results by Mokrane in [11] where the obstacle is zero.
Mixed Problem with an Integral Two-Space-Variables condition for a Third Order Parabolic Equation
Directory of Open Access Journals (Sweden)
Oussaeif Taki Eddine
2016-10-01
Full Text Available This paper is concerned with the existence and uniqueness of a strong solution to a mixed problem which combine Dirichlet and integral two space variables conditions for a third order linear parabolic equation. The proof uses a functional analysis method presented, which it is based on an energy inequality and the density of the range of the operator generated by the problem.
An efficient approach for solving a class of nonlinear 2D parabolic PDEs
Directory of Open Access Journals (Sweden)
Dongjin Kim
2004-01-01
Full Text Available We consider a class of nonlinear 2D parabolic equations that allow for an efficient application of an operator splitting technique and a suitable linearization of the discretized problem. We apply our scheme to study the finite extinction phenomenon for the porous-medium equation with strong absorption. A comparison of accuracy and computational efficiency of the resulting algorithms for several test problems is presented.
Low-Pass Parabolic FFT Filter for Airborne and Satellite Lidar Signal Processing
Zhongke Jiao; Bo Liu; Enhai Liu; Yongjian Yue
2015-01-01
In order to reduce random errors of the lidar signal inversion, a low-pass parabolic fast Fourier transform filter (PFFTF) was introduced for noise elimination. A compact airborne Raman lidar system was studied, which applied PFFTF to process lidar signals. Mathematics and simulations of PFFTF along with low pass filters, sliding mean filter (SMF), median filter (MF), empirical mode decomposition (EMD) and wavelet transform (WT) were studied, and the practical engineering value of PFFTF for l...
10D massive type IIA supergravities as the uplift of parabolic M2-brane torus bundles
Energy Technology Data Exchange (ETDEWEB)
Garcia del Moral, Maria Pilar [Universidad de Antofagasta (Chile). Dept. de Fisica; Restuccia, Alvaro [Universidad de Antofagasta (Chile). Dept. de Fisica; Universidad Simon Bolivar, Caracas (Venezuela, Bolivarian Republic of). Dept. de Fisica
2016-04-15
We remark that the two 10D massive deformations of the N = 2 maximal type IIA supergravity (Romans and HLW supergravity) are associated to the low energy limit of the uplift to 10D of M2-brane torus bundles with parabolic monodromy linearly and non-linearly realized respectively. Romans supergravity corresponds to M2-brane compactified on a twice-punctured torus bundle. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Directory of Open Access Journals (Sweden)
M. Denche
1999-01-01
Full Text Available In the present paper we study nonlocal problems for ordinary differential equations with a discontinuous coefficient for the high order derivative. We establish sufficient conditions, known as regularity conditions, which guarantee the coerciveness for both the space variable and the spectral parameter, as well as guarantee the completeness of the system of root functions. The results obtained are then applied to the study of a nonlocal parabolic transmission problem.
Directory of Open Access Journals (Sweden)
M. G. Crandall
1999-07-01
Full Text Available We study existence of continuous weak (viscosity solutions of Dirichlet and Cauchy-Dirichlet problems for fully nonlinear uniformly elliptic and parabolic equations. Two types of results are obtained in contexts where uniqueness of solutions fails or is unknown. For equations with merely measurable coefficients we prove solvability of the problem, while in the continuous case we construct maximal and minimal solutions. Necessary barriers on external cones are also constructed.
A parabolic model to control quantum interference in T-shaped molecular junctions.
Nozaki, Daijiro; Sevinçli, Hâldun; Avdoshenko, Stanislav M; Gutierrez, Rafael; Cuniberti, Gianaurelio
2013-09-07
Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical interest to develop simple methods controlling the emergence and the positions of QI effects like anti-resonances or Fano line shapes in conductance spectra. In this work, starting from a well-known generic molecular junction with a side group (T-shaped molecule), we propose a simple graphical method to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions.
Thermal buffering of receivers for parabolic dish solar thermal power plants
Manvi, R.; Fujita, T.; Gajanana, B. C.; Marcus, C. J.
A parabolic dish solar thermal power plant comprises a field of parabolic dish power modules where each module is composed of a two-axis tracking parabolic dish concentrator which reflects sunlight (insolation) into the aperture of a cavity receiver at the focal point of the dish. The heat generated by the solar flux entering the receiver is removed by a heat transfer fluid. In the dish power module, this heat is used to drive a small heat engine/generator assembly which is directly connected to the cavity receiver at the focal point. A computer analysis is performed to assess the thermal buffering characteristics of receivers containing sensible and latent heat thermal energy storage. Parametric variations of the thermal inertia of the integrated receiver-buffer storage systems coupled with different fluid flow rate control strategies are carried out to delineate the effect of buffer storage, the transient response of the receiver-storage systems and corresponding fluid outlet temperature. It is concluded that addition of phase change buffer storage will substantially improve system operational characteristics during periods of rapidly fluctuating insolation due to cloud passage.
Optical analysis and performance evaluation of a solar parabolic dish concentrator
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Pavlović Saša R.
2016-01-01
Full Text Available In this study, the optical design of a solar parabolic dish concentrator is presented. The parabolic dish concentrator consists from 11 curvilinear trapezoidal reflective petals made of polymethyl methacrylate with special reflective coating. The dish diameter is equal to 3.8 m and the theoretical focal point distance is 2.26 m. Numerical simulations are made with the commercial software TracePro from Lambda Research, USA, and the final optimum position between absorber and reflector was calculated to 2.075 m; lower than focus distance. This paper presents results for the optimum position and the optimum diameter of the receiver. The decision for selecting these parameters is based on the calculation of the total flux over the flat and corrugated pipe receiver surface; in its central region and in the peripheral region. The simulation results could be useful reference for designing and optimizing of solar parabolic dish concentrators as for as for CFD analysis, heat transfer and fluid flow analysis in corrugated spiral heat absorbers. [Projekat Ministarstva nauke Republike Srbije, br. III42006: Research and development of energy and environmentally highly effective polygeneration systems based on renewable energy resources i br. III45016: Fabrication and characterization of nanophotonic functional structures in biomedicine and informatics
Almost monotonicity formulas for elliptic and parabolic operators with variable coefficients
Matevosyan, Norayr
2010-10-21
In this paper we extend the results of Caffarelli, Jerison, and Kenig [Ann. of Math. (2)155 (2002)] and Caffarelli and Kenig [Amer. J. Math.120 (1998)] by establishing an almost monotonicity estimate for pairs of continuous functions satisfying u± ≥ 0 Lu± ≥ -1, u+ · u_ = 0 ;in an infinite strip (global version) or a finite parabolic cylinder (localized version), where L is a uniformly parabolic operator Lu = LA,b,cu := div(A(x, s)∇u) + b(x,s) · ∇u + c(x,s)u - δsu with double Dini continuous A and uniformly bounded b and c. We also prove the elliptic counterpart of this estimate.This closes the gap between the known conditions in the literature (both in the elliptic and parabolic case) imposed on u± in order to obtain an almost monotonicity estimate.At the end of the paper, we demonstrate how to use this new almost monotonicity formula to prove the optimal C1,1-regularity in a fairly general class of quasi-linear obstacle-type free boundary problems. © 2010 Wiley Periodicals, Inc.
Study on the optical properties of the off-axis parabolic collimator with eccentric pupil
Li, Gang; Gao, Xin; Duan, Jing; Zhang, Henjin
2017-02-01
The off-axis parabolic collimator with eccentric pupil has the advantages of wide spectrum, simple structure, easy assembly and adjustment, high performance price ratio. So, it is widely used for parameters testing and image quality calibration of ground-based and space-based cameras. In addition to the Strehl ratio, resolution, wavefront aberration, modulation transfer function, the general evaluation criteria on the imaging quality of the optical system, the beam parallelism characterize the collimator angle resolving capability and collimation condition of the collimator with the target board, can be measured easily ,quickly and operation process is simple, but the study mainly focus on how to measure it so far. In order to solve Quantitative calculation of this problem, firstly, the discussion of aberration condition of the off- axis parabolic is carried out based on the primary aberration theory. Secondly, analysis on the influencing factor on collimator optical properties is given, including the geometrical aberrations of spherical aberration, coma, astigmatism , the relation between the position of the eccentric pupil and the aberration and optical element surface wavefront aberration, after that, according to the basis of diffraction and wavefront aberration theory, the paper deduced calculation method of the beam parallelism, at last, an example of a 400mm diameter off-axis parabolic collimator with eccentric pupil is given to calculate, the practical results shows that calculation data is well in accordance with actual measurement data and results can meet the demand and has a guiding significance to the actual project manufacture and the theory analysis.
Jeng, Shiann-Shiun; Lin, Hsing-Chen; Lin, Chi-Huei
2012-12-01
In this paper, we propose the parabolic approximation of equi-section division (PAESD) utilizing the symmetry property and amplitude approximation of a sinusoidal waveform to design a direct digital frequency synthesizer (DDFS). The sinusoidal phase of a one-quarter period is divided into equi-sections. The proposed method utilizes the curvature equivalence to derive each parabolic curve function, and then the value of the error function between each parabolic curve function and the sinusoidal function is stored in an error-compensation ROM to reconstruct the real sinusoidal waveform. The upper/lower bound of the maximum error value stored in the error-compensation ROM is derived to determine the minimum required memory word length relative to the number of bits of the equi-sections. Thus, the minimum size of the total ROMs of the DDFS using the PAESD without error-compensation ROM is compressed to 544 bits; the total compression ratio, compared with the minimum size of the total ROMs of the DDFS using the basic look-up table (LUT), is approximately 843:1, achieved by consuming additional circuits [71 adaptive look-up tables (ALUTs), 3 digital signal processor (DSP) block 9-bit elements]. Consequently, the results show that the proposed ROM compression method can effectively achieve a better compression ratio than the state-of-the-art solutions without affecting the spectrum performance of an average spurious-free dynamic range (SFDR) of -85 dBc.
Numerical method for singularly perturbed delay parabolic partial differential equations
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Wang Yulan
2017-01-01
Full Text Available The barycentric interpolation collocation method is discussed in this paper, which is not valid for singularly perturbed delay partial differential equations. A modified version is proposed to overcome this disadvantage. Two numerical examples are provided to show the effectiveness of the present method.
Multigrid Reduction in Time for Nonlinear Parabolic Problems
Energy Technology Data Exchange (ETDEWEB)
Falgout, R. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Manteuffel, T. A. [Univ. of Colorado, Boulder, CO (United States); O' Neill, B. [Univ. of Colorado, Boulder, CO (United States); Schroder, J. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-01-04
The need for parallel-in-time is being driven by changes in computer architectures, where future speed-ups will be available through greater concurrency, but not faster clock speeds, which are stagnant.This leads to a bottleneck for sequential time marching schemes, because they lack parallelism in the time dimension. Multigrid Reduction in Time (MGRIT) is an iterative procedure that allows for temporal parallelism by utilizing multigrid reduction techniques and a multilevel hierarchy of coarse time grids. MGRIT has been shown to be effective for linear problems, with speedups of up to 50 times. The goal of this work is the efficient solution of nonlinear problems with MGRIT, where efficient is defined as achieving similar performance when compared to a corresponding linear problem. As our benchmark, we use the p-Laplacian, where p = 4 corresponds to a well-known nonlinear diffusion equation and p = 2 corresponds to our benchmark linear diffusion problem. When considering linear problems and implicit methods, the use of optimal spatial solvers such as spatial multigrid imply that the cost of one time step evaluation is fixed across temporal levels, which have a large variation in time step sizes. This is not the case for nonlinear problems, where the work required increases dramatically on coarser time grids, where relatively large time steps lead to worse conditioned nonlinear solves and increased nonlinear iteration counts per time step evaluation. This is the key difficulty explored by this paper. We show that by using a variety of strategies, most importantly, spatial coarsening and an alternate initial guess to the nonlinear time-step solver, we can reduce the work per time step evaluation over all temporal levels to a range similar with the corresponding linear problem. This allows for parallel scaling behavior comparable to the corresponding linear problem.
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Qingdong Xuan
2017-12-01
Full Text Available Solar concentrating system is an effective way of combing solar energy with the building to satisfy the needs besides of electricity and hot water, also includes building heating, refrigeration, dehumidification, which require higher quality heat source. This paper put forward a novel static asymmetric lens-walled compound parabolic concentrator (ALCPC, which is composed of the mirror CPC and lens-walled structure, and can make full use of the total internal reflection and specular reflection. The optical performance of the ALCPC under the real application condition was established by software Lighttools®. Furthermore, the optimization structure by rotating the absorber away from the wall at some specific angles was also adopted for a wider scope applications. The results showed that the ALCPC has a large acceptance angle of 59° with highest optical efficiency of around 90% for most of the incident angles and has a relatively uniform flux distribution. In addition, annual performance analysis of the ALCPC was also done for Beijing (39°54’N, 116°23’E. The ALCPC as a static concentrator would be a good solution for the building south wall integration.
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Christos F. Markides
2017-04-01
Full Text Available A recently introduced solution for the stress- and displacement-fields, developed in a multi-layered circular ring, composed of a finite number of linearly elastic concentric layers, subjected to a parabolic distribution of ra-dial stresses, is here extended to encompass a more general loading scheme, closer to actual conditions. The loading scheme includes, besides the para¬-bolic radial stresses, a combination of uniform pressures acting along the outer- and inner- most boundaries of the layered ring. The analytic solution of the problem is achieved by adopting Savin’s pioneering approach for an infinite plate with a hole strengthened by rings. Taking advantage of the results provided by the ana¬lytic solution, a numerical model, simulating the configuration of a three-layered ring (quite commonly encountered in practic¬al applications is validated. The numerical model is then used for a parametric analysis enlightening some crucial aspects of the overall response of the ring.
Yan, Na; Baas, Andreas C. W.
2015-01-01
The formation and evolution of parabolic aeolian dunes depend on vegetation, and as such are particularly sensitive to changes in environmental controls (e.g., temperature, precipitation, and wind regime) as well as to human disturbances (e.g., grazing, agriculture, and recreation). Parabolic dunes can develop from the stabilisation of highly mobile barchan dunes and transverse dunes as well as from blowouts, as a consequence of colonisation and establishment of vegetation when aeolian sand transport is reduced and/or when water stress is relieved (by increasing precipitation, for instance). Conversely, existing parabolic dunes can be activated and may be transformed into barchan dunes and/or transverse dunes when vegetation suffers environmental or anthropogenic stresses. Predicted increases in temperature and drought severity in various regions raise concerns that dune activation and transformations may intensify, and this intensification would have far-reaching implications for environmental, social, and economic sustainability. To date, a broad examination of the development of parabolic dunes and their related transformations across a variety of climate gradients has been absent. This paper reviews existing literature, compares data on the morphology and development of parabolic dunes in a comprehensive global inventory, and scrutinises the mechanisms of different dune transformations and the eco-geomorphic interactions involved. This knowledge is then integrated into a conceptual framework to facilitate understanding and prediction of potential aeolian dune transformations induced by changes in environmental controls and human activities. This conceptual framework can aid judicious land management policies for better adaptations to climatic changes.
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Fei Chen
2015-01-01
Full Text Available The geometrical optics model about the offset effect of solar rays by the thickness of concentrating mirror and the diametric solar model were established. The radiant flux density on the surface of the receiver for parabolic trough solar concentrator was obtained by numerical calculation with the established models. Charge-coupled device (CCD was used for testing gray image on the surface of the receiver for parabolic trough solar concentrator. The image was analyzed by Matlab and the radiant flux density on the surface of the receiver for parabolic trough solar concentrator was achieved. It was found that the result of the theory is consistent with that of the experiment, and the relative deviation on the focal length width was 8.7%. The geometrical structure of receiver based on parabolic trough solar concentrator was optimized, a new parabolic receiver has been proposed, and it has been shown that the optimized geometrical structure of receiver was beneficial to improve the working performance of the entire system.
Driscoll, Daniel G.; Bunkers, Matthew J.; Carter, Janet M.; Stamm, John F.; Williamson, Joyce E.
2010-01-01
The Black Hills area of western South Dakota has a history of damaging flash floods that have resulted primarily from exceptionally strong rain-producing thunderstorms. The best known example is the catastrophic storm system of June 9-10, 1972, which caused severe flooding in several major drainages near Rapid City and resulted in 238 deaths. More recently, severe thunderstorms caused flash flooding near Piedmont and Hermosa on August 17, 2007. Obtaining a thorough understanding of peak-flow characteristics for low-probability floods will require a comprehensive long-term approach involving (1) documentation of scientific information for extreme events such as these; (2) long-term collection of systematic peak-flow records; and (3) regional assessments of a wide variety of peak-flow information. To that end, the U.S. Geological Survey cooperated with the South Dakota Department of Transportation and National Weather Service to produce this report, which provides documentation regarding the August 17, 2007, storm and associated flooding and provides a context through examination of other large storm and flood events in the Black Hills area. The area affected by the August 17, 2007, storms and associated flooding generally was within the area affected by the larger storm of June 9-10, 1972. The maximum observed 2007 precipitation totals of between 10.00 and 10.50 inches occurred within about 2-3 hours in a small area about 5 miles west of Hermosa. The maximum documented precipitation amount in 1972 was 15.0 inches, and precipitation totals of 10.0 inches or more were documented for 34 locations within an area of about 76 square miles. A peak flow of less than 1 cubic foot per second occurred upstream from the 2007 storm extent for streamflow-gaging station 06404000 (Battle Creek near Keystone); whereas, the 1972 peak flow of 26,200 cubic feet per second was large, relative to the drainage area of only 58.6 square miles. Farther downstream along Battle Creek, a 2007
Existence and regularity of a global attractor for doubly nonlinear parabolic equations
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Abderrahmane El Hachimi
2002-05-01
Full Text Available In this paper we consider a doubly nonlinear parabolic partial differential equation $$ frac{partial eta (u}{partial t}-Delta _{p}u+f(x,t,u=0 quad hbox{in }Omega imesmathbb{R}^{+}, $$ with Dirichlet boundary condition and initial data given. We prove the existence of a global compact attractor by using a dynamical system approach. Under additional conditions on the nonlinearities $Beta$, $f$, and on $p$, we prove more regularity for the global attractor and obtain stabilization results for the solutions.
Noniterative three-dimensional grid generation using parabolic partial differential equations
Edwards, T. A.
1985-01-01
A new algorithm for generating three-dimensional grids has been developed and implemented which numerically solves a parabolic partial differential equation (PDE). The solution procedure marches outward in two coordinate directions, and requires inversion of a scalar tridiagonal system in the third. Source terms have been introduced to control the spacing and angle of grid lines near the grid boundaries, and to control the outer boundary point distribution. The method has been found to generate grids about 100 times faster than comparable grids generated via solution of elliptic PDEs, and produces smooth grids for finite-difference flow calculations.
Xu, Wenjun; Tang, Chen; Zhang, Junjiang; Su, Yonggang; Su, Ray Kai Leung
2015-05-20
Oriented partial differential equation (OPDE)-based filtering methods have been demonstrated to be a powerful tool for denoising while preserving all fringes. In this paper we propose new OPDE-filtering models, named parabolic-hyperbolic oriented partial differential equations (PH-OPDEs), based on variational methods. We test the proposed PH-OPDEs on two computer-simulated and two experimentally obtained ESPI fringe patterns with poor quality, and compare our models with related OPDE models. The experimental results have demonstrated that the new models have significantly better performance in numerical stability and computational efficiency as compared with the previous OPDE models.
Coupling and noise induced spiking-bursting transition in a parabolic bursting model
Ji, Lin; Zhang, Jia; Lang, Xiufeng; Zhang, Xiuhui
2013-03-01
The transition from tonic spiking to bursting is an important dynamic process that carry physiologically relevant information. In this work, coupling and noise induced spiking-bursting transition is investigated in a parabolic bursting model with specific discussion on their cooperation effects. Fast/slow analysis shows that weak coupling may help to induce the bursting by changing the geometric property of the fast subsystem so that the original unstable periodical solution are stabilized. It turned out that noise can play the similar stabilization role and induce bursting at appropriate moderate intensity. However, their cooperation may either strengthen or weaken the overall effect depending on the choice of noise level.
Ubieta, Eduardo; Hoyo, Itzal del; Valenzuela, Loreto; Lopez-Martín, Rafael; Peña, Víctor de la; López, Susana
2017-06-01
A simulation model of a parabolic-trough solar collector developed in Modelica® language is calibrated and validated. The calibration is performed in order to approximate the behavior of the solar collector model to a real one due to the uncertainty in some of the system parameters, i.e. measured data is used during the calibration process. Afterwards, the validation of this calibrated model is done. During the validation, the results obtained from the model are compared to the ones obtained during real operation in a collector from the Plataforma Solar de Almeria (PSA).
Compound parabolic concentrator optical fiber tip for FRET-based fluorescent sensors
DEFF Research Database (Denmark)
Hassan, Hafeez Ul; Nielsen, Kristian; Aasmul, Soren
2015-01-01
polymer optical fiber for an excitation and emission wavelength of 550 nm and 650nm, respectively. The model suggests an increase of a factor of 1.6 to 4 in the collected fluorescent power for an ideal CPC tip, as compared to the plane-cut fiber tip for fiber lengths between 5 and 45mm......The Compound Parabolic Concentrator (CPC) optical fiber tip shape has been proposed for intensity based fluorescent sensors working on the principle of FRET (Förster Resonance Energy Transfer). A simple numerical Zemax model has been used to optimize the CPC tip geometry for a step-index multimode...
Photonic Bloch-dipole-Zener Oscillations in Binary Parabolic Optical Waveguide Arrays
Zheng, Ming Jie; Yu, Kin Wah
2011-01-01
We have studied the propagation and Zener tunneling of light in the binary parabolic optical waveguide array (BPOWA), which consists of two evanescently coupled dissimilar optical waveguides. Due to Bragg reflections, BPOWA attains two minibands separated by a minigap at the zone boundary. Various coherent superpositions of optical oscillations and Zener tunneling occur for different parameters on the phase diagram. In particular, Bloch-Zener oscillation and a different type of Bloch-dipole-Zener oscillation are obtained by the field-evolution analysis. The results may have potential applications in optical splitting and waveguiding devices and shed light on the coherent phenomena in optical lattices.
Finite-horizon optimal investment with transaction costs: A parabolic double obstacle problem
Dai, Min; Yi, Fahuai
This paper concerns optimal investment problem of a CRRA investor who faces proportional transaction costs and finite time horizon. From the angle of stochastic control, it is a singular control problem, whose value function is governed by a time-dependent HJB equation with gradient constraints. We reveal that the problem is equivalent to a parabolic double obstacle problem involving two free boundaries that correspond to the optimal buying and selling policies. This enables us to make use of the well-developed theory of obstacle problem to attack the problem. The C regularity of the value function is proven and the behaviors of the free boundaries are completely characterized.
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Lucjan Sapa
2012-01-01
Full Text Available The theorems on the estimates of solutions for nonlinear second-order partial differential functional equations of parabolic type with Dirichlet's condition and for suitable implicit finite difference functional schemes are proved. The proofs are based on the comparison technique. The convergent and stable difference method is considered without the assumption of the global generalized Perron condition posed on the functional variable but with the local one only. It is a consequence of our estimates theorems. In particular, these results cover quasi-linear equations. However, such equations are also treated separately. The functional dependence is of the Volterra type.
An adaptive wavelet-galerkin method for parabolic partial differentia equations
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Victoria Vampa
2015-01-01
Full Text Available In this paper an Adaptive Wavelet-Galerkin method for the solution of parabolic partial differential equations modeling physical problems with different spatial and temporal scales is developed. A semi-implicit time difference scheme is applied and B-spline multiresolution structure on the interval is used. As in many cases these solutions are known to present localized sharp gradients, local error estimators are designed and an efficient adaptive strategy to choose the appropriate scale for each time is developed. Finally, experiments were performed to illustrate the applicability and efficiency of the proposed method.
Stability of a laser cavity with non-parabolic phase transformation elements
CSIR Research Space (South Africa)
Litvin, IA
2013-05-01
Full Text Available aberration in high–power transversally pumped laser rods,” Opt. Commun. 259(1), 223–235 (2006). 14. A. G. Fox and T. Li, “Resonant Modes in a Maser Interferometer,” Bell Syst. Tech. J. 40, 453–488 (1961). 15. O. Svelto, Principles of Lasers, 3rd edition.... Consequently the intra-cavity implementation of any non-conventional phase transformation elements or taking into account the thermal lensing which in general has a non-parabolic phase transformation [13], leads to a solution of the complicated Fox...
Higher-order schemes for the Laplace transformation method for parabolic problems
Douglas, C.
2011-01-01
In this paper we solve linear parabolic problems using the three stage noble algorithms. First, the time discretization is approximated using the Laplace transformation method, which is both parallel in time (and can be in space, too) and extremely high order convergent. Second, higher-order compact schemes of order four and six are used for the the spatial discretization. Finally, the discretized linear algebraic systems are solved using multigrid to show the actual convergence rate for numerical examples, which are compared to other numerical solution methods. © 2011 Springer-Verlag.
DEFF Research Database (Denmark)
Hassan, Hafeez Ul; Nielsen, Kristian; Aasmul, Søren
2015-01-01
We demonstrate that the light excitation and capturing efficiency of fluorescence based fiber-optical sensors can be significantly increased by using a CPC (Compound Parabolic Concentrator) tip instead of the standard plane-cut tip. We use Zemax modelling to find the optimum CPC tip profile...... and fiber length of a polymer optical fiber diabetes sensor for continuous monitoring of glucose levels. We experimentally verify the improved performance of the CPC tipped sensor and the predicted production tolerances. Due to physical size requirements when the sensor has to be inserted into the body...
Identification of an unknown source term for a time fractional fourth-order parabolic equation
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Sara Aziz
2016-11-01
Full Text Available In this article, we considered two inverse source problems for fourth-order parabolic differential equation with fractional derivative in time. Determination of a space dependent source term from the data given at some time t=T is considered in one problem while other addresses the recovery of a time dependent source term from the integral type over-determination condition. Existence and uniqueness of the solution of both inverse source problems are proved. The stability results for the inverse problems are presented.
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Valan-Arasu Amirtham
2007-01-01
Full Text Available The modeling of a parabolic trough collector with hot water generation system with a well-mixed type storage tank using a computer simulation program is presented in this paper. This is followed by an experimental verification of the model and an analysis of the experimental results. The maximum difference between the predicted and the actual storage tank water temperature values is found as 9.59% only. This variation is due to the difference between the actual weather during the test period compared to hourly values and the convection losses from the collector receiver, which were not constant as accounted by the computer simulation program. .
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Fernando F. Gonçalves
2014-01-01
Full Text Available We study the spatial discretisation of the Cauchy problem for a multidimensional linear parabolic PDE of second order, with nondivergent operator and unbounded time- and space-dependent coefficients. The equation free term and the initial data are also allowed to grow. Under a nondegeneracy assumption, we consider the PDE solvability in the framework of the variational approach and approximate in space the PDE problem's generalised solution, with the use of finite-difference methods. The rate of convergence is estimated.
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Fatima G. Khushtova
2016-03-01
Full Text Available In this paper Cauchy problem for a parabolic equation with Bessel operator and with Riemann–Liouville partial derivative is considered. The representation of the solution is obtained in terms of integral transform with Wright function in the kernel. It is shown that when this equation becomes the fractional diffusion equation, obtained solution becomes the solution of Cauchy problem for the corresponding equation. The uniqueness of the solution in the class of functions that satisfy the analogue of Tikhonov condition is proved.
Existence and decay of solutions of some nonlinear parabolic variational inequalities
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Mitsuhiro Nakao
1980-01-01
Full Text Available This paper discusses the existence and decay of solutions u(t of the variational inequality of parabolic type: ≧0for ∀v∈Lp([0,∞;V(p≧2 with v(t∈K a.e. in [0,∞, where K is a closed convex set of a separable uniformly convex Banach space V, A is a nonlinear monotone operator from V to V* and B is a nonlinear operator from Banach space W to W*. V and W are related as V⊂W⊂H for a Hilbert space H. No monotonicity assumption is made on B.
Doubly nonlinear parabolic equations related to the p-Laplacian operator: Semi-discretization
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Fatiha Benzekri
2003-11-01
Full Text Available We study the doubly nonlinear parabolic equation $$ frac{partialBeta(u} {partial t}-riangle_p u + f(x,t,u = 0 quadhbox{in } Omegaimesmathbb{R}^+, $$ with Dirichlet boundary conditions and initial data. We investigate a time-discretization of the continuous problem by the Euler forward scheme. In addition to proving existence, uniqueness and stability questions, we study the long time behavior of the solution to the discrete problem. We prove the existence of a global attractor, and obtain its regularity under additional conditions.
Global Attractors for Semilinear Parabolic Problems Involving X-Elliptic Operators
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Stefanie Sonner
2015-12-01
Full Text Available We consider semilinear parabolic equations involving an operator that is X-elliptic with respect to a family of vector fields X with suitable properties. The vector fields determine the natural functional setting associated to the problem and the admissible growth of the non-linearity. We prove the global existence of solutions and characterize their longtime behavior. In particular, we show the existence and finite fractal dimension of the global attractor of the generated semigroup and the convergence of solutions to an equilibrium solution when time tends to infinity.
Classical and weak solutions for semilinear parabolic equations with Preisach hysteresis
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Mathias Jais
2008-01-01
Full Text Available We consider the solvability of the semilinear parabolic differential equation \\[\\frac{\\partial u}{\\partial t}(x,t- \\Delta u(x,t + c(x,tu(x,t = \\mathcal{P}(u + \\gamma (x,t\\] in a cylinder \\(D=\\Omega \\times (0,T\\, where \\(\\mathcal{P}\\ is a hysteresis operator of Preisach type. We show that the corresponding initial boundary value problems have unique classical solutions. We further show that using this existence and uniqueness result, one can determine the properties of the Preisach operator \\(\\mathcal{P}\\ from overdetermined boundary data.
DEFF Research Database (Denmark)
Gammelmark, Søren; Eckardt, André
2013-01-01
We theoretically study the adiabatic preparation of an antiferromagnetic phase in a mixed Mott insulator of two bosonic atom species in a one-dimensional optical lattice. In such a system one can engineer a tunable parabolic inhomogeneity by controlling the difference of the trapping potentials f...... that during the preparation finite size effects will play a crucial role for a system of realistic size. The experiment that we propose can be realized, for example, using atomic mixtures of rubidium 87 with potassium 41, or ytterbium 168 with ytterbium 174....
Algorithm 850: Real parabolic cylinder functions U(a,x), V(a,x)
Gil, Amparo; Segura, Javier; Temme, Nico
2006-01-01
textabstractFortran 90 programs for the computation of real parabolic cylinder functions are presented. The code computes the functions U(a, x), V (a, x) and their derivatives for real a and $x(xgeq 0)$. The code also computes scaled functions. The range of computation for scaled PCFs is practically unrestricted. The aimed relative accuracy for scaled functions is better than 5 10^{-14}. Exceptions to this accuracy are the evaluation of the functions near their zeros and the error caused by t...
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Helge Holden
2003-04-01
Full Text Available We prove existence and uniqueness of entropy solutions for the Cauchy problem of weakly coupled systems of nonlinear degenerate parabolic equations. We prove existence of an entropy solution by demonstrating that the Engquist-Osher finite difference scheme is convergent and that any limit function satisfies the entropy condition. The convergence proof is based on deriving a series of a priori estimates and using a general $L^p$ compactness criterion. The uniqueness proof is an adaption of Kruzkov's ``doubling of variables'' proof. We also present a numerical example motivated by biodegradation in porous media.
Mang, Andreas; Toma, Alina; Schuetz, Tina A; Becker, Stefan; Eckey, Thomas; Mohr, Christian; Petersen, Dirk; Buzug, Thorsten M
2012-07-01
A novel unconditionally stable, explicit numerical method is introduced to the field of modeling brain cancer progression on a tissue level together with an inverse problem (IP) based on optimal control theory that allows for automated model calibration with respect to observations in clinical imaging data. Biophysical models of cancer progression on a tissue level are in general based on the assumption that the spatiotemporal spread of cancerous cells is determined by cell division and net migration. These processes are typically described in terms of a parabolic partial differential equation (PDE). In the present work a parallelized implementation of an unconditionally stable, explicit Euler (EE(⋆) ) time integration method for the solution of this PDE is detailed. The key idea of the discussed EE(⋆) method is to relax the strong stability requirement on the spectral radius of the coefficient matrix by introducing a subdivision regime for a given outer time step. The performance is related to common implicit numerical methods. To quantify the numerical error, a simplified model that has a closed form solution is considered. To allow for a systematic, phenomenological validation a novel approach for automated model calibration on the basis of observations in medical imaging data is developed. The resulting IP is based on optimal control theory and manifests as a large scale, PDE constrained optimization problem. The numerical error of the EE(⋆) method is at the order of standard implicit numerical methods. The computing times are well below those obtained for implicit methods and by that demonstrate efficiency. Qualitative and quantitative analysis in 12 patients demonstrates that the obtained results are in strong agreement with observations in medical imaging data. Rating simulation success in terms of the mean overlap between model predictions and manual expert segmentations yields a success rate of 75% (9 out of 12 patients). The discussed EE(⋆) method
DEFF Research Database (Denmark)
Petersen, Carsten Lunde; Roesch, Pascale
2010-01-01
Vi definerer parabolske stråler i analogi med ydre stråler for polynomier. We anvender dernæst disse stråler/kurver til at definere parabolske puzzles, inspireret af Yoccoz puzzles for kvadratiske polynomier, men modificeret nær det parabolske fikspunkt, hvor dynamikken er både attraktiv og repul...
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Vladimir Blazek
2005-01-01
Full Text Available All astronauts often feel uncomfortable during first encounter microgravity because of fluid shifts from the lower extremities to the head caused by weightlessness. Parabolic flights offer a great possibility for research of this phenomenon under “zero gravity”. With a combination of the optoelectronic sensor concepts PPG and PPGI and an ultrasound device it should be possible to measure all relevant parameters for description and further explanation of rapid fluid shifts along the body axis in humans during parabolic flights. A research team of the RWTH Aachen University and the Charité University Berlin will participate in the 7th German Parabolic Flight Campaign in September 2005 and perform the experiments under micro gravitation. A combination of used non-invasive strategies will reveal new insights into the human hemodynamics under microgravity conditions. The optoelectronic part of this interdisciplinary research experiment, details from the measuring setup, data collecting and post processing will be discussed.
Xu, Guoying; Chen, Wei; Deng, Shiming; Zhang, Xiaosong; Zhao, Sainan
2015-12-04
Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors' tube/plate wall. The poor durability of the coating can lead to an increased manufacturing cost and unreliability for a solar collector operated at a higher temperature. Therefore, a novel nanofluid-based direct absorption solar collector (NDASC) employing uncoated collector tubes has been proposed, and its operating characteristics for medium-temperature solar collection were theoretically and experimentally studied in this paper. CuO/oil nanofluid was prepared and used as working fluid of the NDASC. The heat-transfer mechanism of the NDASC with parabolic trough concentrator was theoretically evaluated and compared with a conventional indirect absorption solar collector (IASC). The theoretical analysis results suggested that the fluid's temperature distribution in the NDASC was much more uniform than that in the IASC, and an enhanced collection efficiency could be achieved for the NDASC operated within a preferred working temperature range. To demonstrate the feasibility of the proposed NDASC, experimental performances of an NDASC and an IASC with the same parabolic trough concentrator were furthermore evaluated and comparatively discussed.
Analysis of solar water heater with parabolic dish concentrator and conical absorber
Rajamohan, G.; Kumar, P.; Anwar, M.; Mohanraj, T.
2017-06-01
This research focuses on developing novel technique for a solar water heating system. The novel solar system comprises a parabolic dish concentrator, conical absorber and water heater. In this system, the conical absorber tube directly absorbs solar radiation from the sun and the parabolic dish concentrator reflects the solar radiations towards the conical absorber tube from all directions, therefore both radiations would significantly improve the thermal collector efficiency. The working fluid water is stored at the bottom of the absorber tubes. The absorber tubes get heated and increases the temperature of the working fluid inside of the absorber tube and causes the working fluid to partially evaporate. The partially vaporized working fluid moves in the upward direction due to buoyancy effect and enters the heat exchanger. When fresh water passes through the heat exchanger, temperature of the vapour decreases through heat exchange. This leads to condensation of the vapour and forms liquid phase. The working fluid returns to the bottom of the collector absorber tube by gravity. Hence, this will continue as a cyclic process inside the system. The proposed investigation shows an improvement of collector efficiency, enhanced heat transfer and a quality water heating system.
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Guoying Xu
2015-12-01
Full Text Available Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors’ tube/plate wall. The poor durability of the coating can lead to an increased manufacturing cost and unreliability for a solar collector operated at a higher temperature. Therefore, a novel nanofluid-based direct absorption solar collector (NDASC employing uncoated collector tubes has been proposed, and its operating characteristics for medium-temperature solar collection were theoretically and experimentally studied in this paper. CuO/oil nanofluid was prepared and used as working fluid of the NDASC. The heat-transfer mechanism of the NDASC with parabolic trough concentrator was theoretically evaluated and compared with a conventional indirect absorption solar collector (IASC. The theoretical analysis results suggested that the fluid’s temperature distribution in the NDASC was much more uniform than that in the IASC, and an enhanced collection efficiency could be achieved for the NDASC operated within a preferred working temperature range. To demonstrate the feasibility of the proposed NDASC, experimental performances of an NDASC and an IASC with the same parabolic trough concentrator were furthermore evaluated and comparatively discussed.
Sound propagation in a turbulent atmosphere near the ground: a parabolic equation approach.
Ostashev, V E; Salomons, E M; Clifford, S F; Lataitis, R J; Wilson, D K; Blanc-Benon, P; Juvé, D
2001-05-01
The interference of the direct wave from the point source to the receiver and the wave reflected from the impedance ground in a turbulent atmosphere is studied. A parabolic equation approach for calculating the sound pressure p at the receiver is formulated. Then, the parabolic equation is solved by the Rytov method yielding expressions for the complex phases of direct and ground-reflected waves. Using these expressions, a formula for the mean squared sound pressure [absolute value(p)2] is derived for the case of anisotropic spectra of temperature and wind velocity fluctuations. This formula contains the "coherence factor," which characterizes the coherence between direct and ground-reflected waves. It is shown that the coherence factor is equal to the normalized coherence function of a spherical sound wave for line-of-sight propagation. For the case of isotropic turbulence, this result allows one to obtain analytical formulas for [absolute value(p)2] for the Kolmogorov, Gaussian, and von Karman spectra of temperature and wind velocity fluctuations. Using these formulas, the effects of temperature and wind velocity fluctuations, and the effects of different spectra of these fluctuations on the mean squared sound pressure, are numerically studied. Also the effect of turbulent anisotropy on the interference of direct and ground reflected waves is numerically studied. Finally, it is shown that the mean squared sound pressure [absolute value(p)2] calculated for the von Karman spectrum of temperature fluctuations agrees well with experimental data obtained in a laboratory experiment.
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Hrushikesh Bhujangrao Kulkarni
2016-02-01
Full Text Available Concentrating collectors absorbs solar energy and convert it into heat for generating hot water, steam at required temperature, which can be further used for solar thermal applications. The developing countries like India where solar energy is abundantly available; there is need to develop technology for harnessing solar energy for power production, but the main problem associated with concentrating solar power technology is the high cost of installation and low output efficiency. To solve this problem, a prototype cylindrical parabolic solar collector having aperture area of 1.89 m2 is designed and developed using low cost highly reflecting and absorbing material to reduce initial cost of project and improve thermal efficiency. ASHRAE Standard 93, 1986 was used to evaluate the thermal performance and it was observed that this system can generate hot water at an average temperature of 500C per day with an average efficiency of 49% which is considerable higher than flat plate solar collectors. Hot water produced by this system can be useful for domestic, agricultural, industrial process heat applications.Article History: Received Sept 19, 2015; Received in revised form Dec 23, 2015; Accepted February 2, 2016; Available online How to Cite This Article: Bhujangrao, K.H. (2016. Design and Development of Prototype Cylindrical Parabolic Solar Collector for Water Heating Application. International Journal of Renewable Energy Development, 5(1, 49-55 http://dx.doi.org/10.14710/ijred.5.1.49-55
Study of the parabolic and elliptic approaches validities for a turbulent co-flowing jet
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Mahmoud Houda
2012-01-01
Full Text Available An axisymmetric turbulent jet discharged in a co-flowing stream was studied with the aid of parabolic and elliptic approaches. The simulations were performed with two in-house codes. Detailed comparisons of data show good agreement with the corresponding experiments; and different behaviors of jet dilution were found in initial region at different ranges of velocities ratios. It has been found that the two approaches give practically the same results for the velocities ratios Ru ≤ 1.5. Further from this value, the elliptic approach highlights the appearance of the fall velocity zone and that’s due to the presence of a trough low pressure. This fall velocity has not been detected by the parabolic approach and that’s due to the jet entrainment by the ambient flow. The intensity of this entrainment is directly related to the difference between the primary (jet and the secondary flow (co-flow. In fact, by increasing the velocities ratios Ru, the sucked flux by the outer stream becomes more important; the fall velocity intensifies and changes into a recirculation zone for Ru ≥ 5.
Ansari, A. R.; Bakr, S. A.; Shishkin, G. I.
2007-08-01
A Dirichlet boundary value problem for a delay parabolic differential equation is studied on a rectangular domain in the x-t plane. The second-order space derivative is multiplied by a small singular perturbation parameter, which gives rise to parabolic boundary layers on the two lateral sides of the rectangle. A numerical method comprising a standard finite difference operator (centred in space, implicit in time) on a rectangular piecewise uniform fitted mesh of NxxNt elements condensing in the boundary layers is proved to be robust with respect to the small parameter, or parameter-uniform, in the sense that its numerical solutions converge in the maximum norm to the exact solution uniformly well for all values of the parameter in the half-open interval (0,1]. More specifically, it is shown that the errors are bounded in the maximum norm by , where C is a constant independent not only of Nx and Nt but also of the small parameter. Numerical results are presented, which validate numerically this theoretical result and show that a numerical method consisting of the standard finite difference operator on a uniform mesh of NxxNt elements is not parameter-robust.
Castillo, Karl D; Ries, Justin B; Bruno, John F; Westfield, Isaac T
2014-12-22
Anthropogenic increases in atmospheric CO2 over this century are predicted to cause global average surface ocean pH to decline by 0.1-0.3 pH units and sea surface temperature to increase by 1-4°C. We conducted controlled laboratory experiments to investigate the impacts of CO2-induced ocean acidification (pCO2 = 324, 477, 604, 2553 µatm) and warming (25, 28, 32°C) on the calcification rate of the zooxanthellate scleractinian coral Siderastrea siderea, a widespread, abundant and keystone reef-builder in the Caribbean Sea. We show that both acidification and warming cause a parabolic response in the calcification rate within this coral species. Moderate increases in pCO2 and warming, relative to near-present-day values, enhanced coral calcification, with calcification rates declining under the highest pCO2 and thermal conditions. Equivalent responses to acidification and warming were exhibited by colonies across reef zones and the parabolic nature of the corals' response to these stressors was evident across all three of the experiment's 30-day observational intervals. Furthermore, the warming projected by the Intergovernmental Panel on Climate Change for the end of the twenty-first century caused a fivefold decrease in the rate of coral calcification, while the acidification projected for the same interval had no statistically significant impact on the calcification rate-suggesting that ocean warming poses a more immediate threat than acidification for this important coral species.
Babbick, Maren; Barjaktarović, Žarko; Hampp, Ruediger
Plants sense gravity by specialized cells (statocytes) and adjust growth and development accordingly. It has, however, also been shown that plant cells which are not part of specialized tissues are also able to sense gravitational forces. Therefore we used undifferentiated, homogeneous cell cultures of Arabidopsis thaliana (cv. Columbia) in order to identify early alterations in gene expression as a response to altered gravitational field strengths. In this contribution we report on cell cultures exposed to parabolic flights (approximately 20 sec of microgravity). For this short-term exposure study, we specifically checked for genes at the beginning of signal transduction chains, such as those coding for transcription factors (TFs). TFs are small proteins that regulate expression of their target genes by binding to specific promoter sequences. Our main focus were members of the so-called WRKY TF family. WRKY TFs are known to be involved in various physiological processes like senescence and pathogen defense. By quantifying transcriptional changes of these genes by real-time RT-PCR, we wanted to find out, how gene expression is affected by both hyperand microgravity conditions during a parabolic flight. For this purpose Arabidopsis thaliana callus cultures were metabolically quenched by the injection of RNAlater at the end of the microgravity-phase of each parabola. The data we present will show how fast changes in amounts of transcripts will occur, and to what degree the expression profiles are comparable with data obtained from exposures to hypergravity and simulated microgravity.
A Novel Parabolic Trough Concentrating Solar Heating for Cut Tobacco Drying System
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Jiang Tao Liu
2014-01-01
Full Text Available A novel parabolic trough concentrating solar heating for cut tobacco drying system was established. The opening width effect of V type metal cavity absorber was investigated. A cut tobacco drying mathematical model calculated by fourth-order Runge-Kutta numerical solution method was used to simulate the cut tobacco drying process. And finally the orthogonal test method was used to optimize the parameters of cut tobacco drying process. The result shows that the heating rate, acquisition factor, and collector system efficiency increase with increasing the opening width of the absorber. The simulation results are in good agreement with experimental data for cut tobacco drying process. The relative errors between simulated and experimental values are less than 8%, indicating that this mathematical model is accurate for the cut tobacco airflow drying process. The optimum preparation conditions are an inlet airflow velocity of 15 m/s, an initial cut tobacco moisture content of 26%, and an inlet airflow temperature of 200°C. The thermal efficiency of the dryer and the final cut tobacco moisture content are 66.32% and 14.15%, respectively. The result shows that this parabolic trough concentrating solar heating will be one of the heat recourse candidates for cut tobacco drying system.
Hirai, Hiroaki; Kitaya, Yoshiaki; Hirai, Takehiro
A fundamental study was conducted to establish an experimental system for space farming. Since to ensure optimal light for plant cultivation in space is of grave importance, this study examined the performance of light sources and radiation sensors under microgravity conditions created during the parabolic airplane flight. Three kinds of light sources, a halogen bulb, a fluorescent tube, and blue and red LEDs, and ten models of radiation sensors available in the market were used for the experiment. Surface temperature of the light sources, output signals from the radiation sensors, spectroscopic characteristics were measured at the gravity levels of 0.01, 1.0 and 1.8 G for 20 seconds each during parabolic airplane flights. As a result, the performance of the halogen lamp was affected the most by the gravity level among the three light sources. Under the microgravity conditions which do not raise heat convection, the temperature of the halogen lamp rose and the output of the radiation sensors increased. Spectral distributions of the halogen lamp indicated that peak wavelength appeared the highest at the level of 0.01G, which contributed to the increase in light intensity. In the case of red and blue LEDs, which are promising light sources in space farming, the temperature of both LED chips rose but irradiance from red LED increased and that from blue LED decreased under microgravity conditions due to the different thermal characteristics.
Gao, Jing; Lu, Qi-Peng; Peng, Zhong-Qi; Ding, Hai-Quan; Gao, Hong-Zhi
2013-05-01
High signal-to-noise ratio (SNR) of system is necessary to obtain accurate blood components in near infrared noninvasive biochemical analysis. In order to improve SNR of analytical system, high-efficiency double compound parabolic concentrator (DCPC) system was researched, which was aimed at increasing light utilization efficiency. Firstly, with the request of collection efficiency in near infrared noninvasive biochemical analysis, the characteristic of emergent rays through compound parabolic concentrator (CPC) was analyzed. Then the maximum focusing angle range of the first stage CPC was determined. Secondly, the light utilization efficiency of truncated type was compared with standard DCPC, thus the best structure parameters of DCPC system were optimized. Lastly, combined with optical parameters of skin tissue, calculations were operated when incident wavelength is 1 000 nm. The light utilization efficiency of DCPC system, CPC-focusing mirror system, and non-optical collecting system was calculated. The results show that the light utilization efficiency of the three optical systems is 1.46%, 0.84% and 0.26% respectively. So DCPC system enhances collecting ability for human diffuse reflection light, and helps improve SNR of noninvasive biochemical analysis system and overall analysis accuracy effectively.
Measurement of Hydrogen Purge Rates in Parabolic Trough Receiver Tubes: Preprint
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Glatzmaier, G. C.
2010-10-01
The purpose of this research is to investigate and develop methods to remove hydrogen centrally from commercial parabolic trough power plants. A mathematical model was developed that tracks the generation and transport of hydrogen within an operating plant. Modeling results predicted the steady-state partial pressure of hydrogen within the receiver annuli to be ~1 torr. This result agrees with measured values for the hydrogen partial pressure. The model also predicted the rate at which hydrogen must be actively removed from the expansion tank to reduce the partial pressure of hydrogen within the receiver annuli to less than 0.001 torr. Based on these results, mitigation strategies implemented at operating parabolic trough power plants can reduce hydrogen partial pressure to acceptable levels. Transient modeling predicted the time required to reduce the hydrogen partial pressures within receiver annuli to acceptable levels. The times were estimated as a function of bellows temperature, getter quantity, and getter temperature. This work also includes an experimental effort that will determine the time required to purge hydrogen from a receiver annulus with no getter.
Development of a finite element model for the simulation of parabolic impact of sandwich panels
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Ramakrishnan Karthik Ram
2015-01-01
Full Text Available Sandwich panels are lightweight structures of two thin high strength facesheets bonded to either side of a thick low density core such as foams and honeycombs. It is necessary to study the impact response of sandwich structures in order to ensure the reliability and safety of these structures. The response of sandwich panels to impact loading is usually studied for impact at normal angle of incidence. In real engineering situations, the structures are more frequently loaded at some oblique angle or with a complex trajectory. It is easy to carry out normal impact tests using devices like the drop tower, but impacts at oblique angles are difficult to characterise experimentally. A tri-dimensional impact device called Hexapod has been developed to experimentally study the impact loading of sandwich plates with a parabolic trajectory. The Hexapod is a modified Gough-Stewart platform that can be moved independently in the six degrees of freedom, corresponding to three translation axes and three rotation axes. In this paper, an approach for modelling the parabolic impact of sandwich structures with thin metallic facesheets and polymer foam core using commercial finite element code LS-DYNA software is presented. The results of the FE model of sandwich panels are compared with experimental data in terms of the time history of vertical and horizontal components of force. A comparison of the strain history obtained from Digital Image Correlation and LS-Dyna model are also presented.
Ou, Yongsheng
The need for new sources of energy is expected to become a critical problem within the next few decades. Nuclear fusion arises as a potential source of energy with sufficient energy density to supply the world population with its steadily increasing energy demands. The need to optimize the tokamak concept for the design of an economical, possibly steady state, fusion power plant have motivated extensive international research aimed at finding the so-called "advanced tokamak (AT) operation scenarios." It has been demonstrated that simultaneous real-time control of the current and pressure profiles could lead to the steady state sustainment of an internal transport barrier (ITB), and so to a stationary optimized plasma regime. It has also been suggested that global current profile control, eventually combined with pressure profile control, can be an effective mechanism for neoclassical tearing mode (NTM) control and avoidance. The control of linear or quasi-linear parabolic diffusion-reaction partial differential equations (PDE) has been extensively studied using interior control (see [1] and references therein) or boundary control (see [2] and references therein). Recently, the control of bilinear parabolic partial differential equations via actuation of the diffusive coefficient term, named diffusivity control here, has caught increasing interest. The diffusive coefficient term in a parabolic PDE is not necessary fixed or uncontrollable. For example, the diffusivity control problem arises in the control of the current density profile in magnetically confined fusion plasmas [3], where physical actuators such as plasma total current, line-averaged density and non-inductive total power are used to steer the plasma current density to a desired profile in a designated time period. By modulating these physical actuators it is possible not only to vary the amount of non-inductive current driven into the system (interior control) and the total plasma current (boundary
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Zhai Rongrong
2013-01-01
Full Text Available The thermal oil is applied as the heat transfer fluid in a solar parabolic trough collector system. Firstly, the system dynamic model was established and validated by the real operating data in typical summer and spring days in references. Secondly, the alteration characteristics of different solar radiation, inlet water temperature and flow rate, and collectors’ area and length are analyzed and compared with the normal working condition. The model can be used for studying, system designing, and better understanding of the performance of parabolic trough systems.
Mcaninch, G. L.; Myers, M. K.
1980-01-01
The parabolic approximation for the acoustic equations of motion is applied to the study of the sound field generated by a plane wave at or near grazing incidence to a finite impedance boundary. It is shown how this approximation accounts for effects neglected in the usual plane wave reflection analysis which, at grazing incidence, erroneously predicts complete cancellation of the incident field by the reflected field. Examples are presented which illustrate that the solution obtained by the parabolic approximation contains several of the physical phenomena known to occur in wave propagation near an absorbing boundary.
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Denzin, R.; Lange, P.; Savaidis, G. [MAN Nutzfahrzeuge AG, Muenchen (Germany). Abt. fuer Betriebsfestigkeit und Pruefstanderprobung
2003-07-01
The stress-strain behaviour of hot-peened one-leaf parabolic springs made of 50CrV4-Nb for light trucks has been determined by measurements under service conditions. The results obtained on the test rig for payload and quasistatic driving situations were in good agreement with the corresponding ones measured during driving the prototype vehicle on the test track. To investigate the failure behaviour of the springs on the test rig, standardized load spectra in accordance with Grubisic and Fischer's, procedure were taken as a basis. All specimens provided failure at the rear side of the spring arm. In the theoretical damage analysis, systematic variation of the input data within allowable limit values yields wide deviations in the calculated fatigue life values and failure-ciritical locations. Hence, the accurate determination of the input data by means of fatigue tests is an indispensable task that needs to be done. (orig.)
Mechhoud, Sarra
2017-12-14
In this paper, the adaptive bilinear control of a first-order 1-D hyperbolic partial differential equation (PDE) with an unknown time-varying source term is investigated where only boundary measurements are available. By means of boundary injection, the bilinear adaptive law is developed in the Lyapunov approach. It consists of a state observer and an input adaptation law combined with a bilinear control method derived using an energy-like principle. Both global asymptotic practical convergence of the tracking error and input-to-state stability of the system are guaranteed. A potential application of this control strategy is the one-loop solar collector parabolic trough where the solar irradiance is the unknown input (source term) and the flow rate is the control variable. The objective is to drive the boundary temperature at the outlet to track a desired profile. Simulation results are provided to illustrate the performance of the proposed method.
Goswami, Deepjyoti
2011-09-01
In this article, we propose and analyze an alternate proof of a priori error estimates for semidiscrete Galerkin approximations to a general second order linear parabolic initial and boundary value problem with rough initial data. Our analysis is based on energy arguments without using parabolic duality. Further, it follows the spirit of the proof technique used for deriving optimal error estimates for finite element approximations to parabolic problems with smooth initial data and hence, it unifies both theories, that is, one for smooth initial data and other for nonsmooth data. Moreover, the proposed technique is also extended to a semidiscrete mixed method for linear parabolic problems. In both cases, optimal L2-error estimates are derived, when the initial data is in L2. A superconvergence phenomenon is also observed, which is then used to prove L∞-estimates for linear parabolic problems defined on two-dimensional spatial domain again with rough initial data. Copyright © Taylor & Francis Group, LLC.
Parabolic solar cooker: Cooking with heat pipe vs direct spiral copper tubes
Craig, Omotoyosi O.; Dobson, Robert T.
2016-05-01
Cooking with solar energy has been seen by many researchers as a solution to the challenges of poverty and hunger in the world. This is no exception in Africa, as solar coking is viewed as an avenue to eliminate the problem of food insecurity, insufficient energy supply for household and industrial cooking. There are several types of solar cookers that have been manufactured and highlighted in literature. The parabolic types of solar cookers are known to reach higher temperatures and therefore cook faster. These cookers are currently being developed for indoor cooking. This technology has however suffered low cooking efficiency and thus leads to underutilization of the high heat energy captured from the sun in the cooking. This has made parabolic solar cookers unable to compete with other conventional types of cookers. Several methods to maximize heat from the sun for indirect cooking has been developed, and the need to improve on them of utmost urgency. This paper investigates how to optimize the heat collected from the concentrating types of cookers by proposing and comparing two types of cooking sections: the spiral hot plate copper tube and the heat pipe plate. The system uses the concentrating solar parabolic dish technology to focus the sun on a conical cavity of copper tubes and the heat is stored inside an insulated tank which acts both as storage and cooking plate. The use of heat pipes to transfer heat between the oil storage and the cooking pot was compared to the use of a direct natural syphon principle which is achieved using copper tubes in spiral form like electric stove. An accurate theoretical analysis for the heat pipe cooker was achieved by solving the boiling and vaporization in the evaporator side and then balancing it with the condensation and liquid-vapour interaction in the condenser part while correct heat transfer, pressure and height balancing was calculated in the second experiment. The results show and compare the cooking time, boiling
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Rubio Gerardo
2011-03-01
Full Text Available We consider the Cauchy problem in ℝd for a class of semilinear parabolic partial differential equations that arises in some stochastic control problems. We assume that the coefficients are unbounded and locally Lipschitz, not necessarily differentiable, with continuous data and local uniform ellipticity. We construct a classical solution by approximation with linear parabolic equations. The linear equations involved can not be solved with the traditional results. Therefore, we construct a classical solution to the linear Cauchy problem under the same hypotheses on the coefficients for the semilinear equation. Our approach is using stochastic differential equations and parabolic differential equations in bounded domains. Finally, we apply the results to a stochastic optimal consumption problem. Nous considérons le problème de Cauchy dans ℝd pour une classe d’équations aux dérivées partielles paraboliques semi linéaires qui se pose dans certains problèmes de contrôle stochastique. Nous supposons que les coefficients ne sont pas bornés et sont localement Lipschitziennes, pas nécessairement différentiables, avec des données continues et ellipticité local uniforme. Nous construisons une solution classique par approximation avec les équations paraboliques linéaires. Les équations linéaires impliquées ne peuvent être résolues avec les résultats traditionnels. Par conséquent, nous construisons une solution classique au problème de Cauchy linéaire sous les mêmes hypothèses sur les coefficients pour l’équation semi-linéaire. Notre approche utilise les équations différentielles stochastiques et les équations différentielles paraboliques dans les domaines bornés. Enfin, nous appliquons les résultats à un problème stochastique de consommation optimale.
Wu, Liang; Ehlin-Henriksson, Barbro; Zhou, Xiaoying; Zhu, Hong; Ernberg, Ingemar; Kis, Lorand L; Klein, George
2017-12-01
Diffuse large B-cell lymphoma (DLBCL), the most common type of malignant lymphoma, accounts for 30% of adult non-Hodgkin lymphomas. Epstein-Barr virus (EBV) -positive DLBCL of the elderly is a newly recognized subtype that accounts for 8-10% of DLBCLs in Asian countries, but is less common in Western populations. Five DLBCL-derived cell lines were employed to characterize patterns of EBV latent gene expression, as well as response to cytokines and chemotaxis. Interleukin-4 and interleukin-21 modified LMP1, EBNA1 and EBNA2 expression depending on cell phenotype and type of EBV latent programme (type I, II or III). These cytokines also affected CXCR4- or CCR7-mediated chemotaxis in two of the cell lines, Farage (type III) and Val (type II). Further, we investigated the effect of EBV by using dominant-negative EBV nuclear antigen 1(dnEBNA1) to eliminate EBV genomes. This resulted in decreased chemotaxis. By employing an alternative way to eliminate EBV genomes, Roscovitine, we show an increase of apoptosis in the EBV-positive lines. These results show that EBV plays an important role in EBV-positive DLBCL lines with regard to survival and chemotactic response. Our findings provide evidence for the impact of microenvironment on EBV-carrying DLBCL cells and might have therapeutic implications. © 2017 John Wiley & Sons Ltd.
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Kelsie H. Okamura
2018-01-01
Full Text Available ObjectivePublic-sector behavioral health systems seeking to implement evidence-based treatments (EBTs may face challenges selecting EBTs given their limited resources. This study describes and illustrates one method to calculate cost related to training and consultation to assist system-level decisions about which EBTs to select.MethodsTraining, consultation, and indirect labor costs were calculated for seven commonly implemented EBTs. Using extant literature, we then estimated the diagnoses and populations for which each EBT was indicated. Diagnostic and demographic information from Medicaid claims data were obtained from a large behavioral health payer organization and used to estimate the number of covered people with whom the EBT could be used and to calculate implementation-associated costs per consumer.ResultsFindings suggest substantial cost to therapists and service systems related to EBT training and consultation. Training and consultation costs varied by EBT, from Dialectical Behavior Therapy at $238.07 to Cognitive Behavioral Therapy at $0.18 per potential consumer served. Total cost did not correspond with the number of prospective consumers served by an EBT.ConclusionA cost-metric that accounts for the prospective recipients of a given EBT within a given population may provide insight into how systems should prioritize training efforts. Future policy should consider the financial burden of EBT implementation in relation to the context of the population being served and begin a dialog in creating incentives for EBT use.
Hollander, Frank den
2008-01-01
This book is an introduction to the theory and applications of large deviations, a branch of probability theory that describes the probability of rare events in terms of variational problems. By focusing the theory, in Part A of the book, on random sequences, the author succeeds in conveying the main ideas behind large deviations without a need for technicalities, thus providing a concise and accessible entry to this challenging and captivating subject. The selection of modern applications, described in Part B of the book, offers a good sample of what large deviation theory is able to achieve
DEFF Research Database (Denmark)
Groemer, Gernot E.; Brimacombe, Joseph; Haas, Thorsten
2005-01-01
We determined the feasibility of laryngoscope-guided tracheal intubation (LG-TI) in microgravity obtained during parabolic flight and tested the hypothesis that LG-TI is similarly successful in the free-floating condition, with the patient's head gripped between the anesthesiologist's knees...
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Erkinjon T. Karimov
2013-06-01
Full Text Available In this work, we study a boundary problem with non-local conditions, by relating values of the unknown function with various characteristics. The parabolic-hyperbolic equation with three lines of type changing is equivalently reduced to a system of Volterra integral equations of the second kind.
Grosse, J.; Wehland, M.; Pietsch, J.; Ma, X.; Ulbrich, C.; Schulz, H.; Saar, K.; Hübner, N.; Hauslage, J.; Hemmersbach, R.; Braun, M.; van Loon, J.; Vagt, N.; Infanger, M.; Eilles, C.; Egli, M.; Richter, P.; Baltz, T.; Einspanier, R.; Sharbati, S.; Grimm, D.
2012-01-01
This study focused on the effects of short-term microgravity (22 s) on the gene expression and morphology of endothelial cells (ECs) and evaluated gravisensitive signaling elements. ECs were investigated during four German Space Agency (Deutsches Zentrum für Luft- und Raumfahrt) parabolic flight
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Aondoyila KUHE
2016-07-01
Full Text Available A single slope solar still, integrated with latent heat thermal energy storage system coupled to a parabolic concentrator was designed with the aim of improving productivity. 14 kg of beeswax was used as phase change material (PCM between the absorber plate and the bottom of the still to keep the operating temperature of the still high enough to produce distilled water even during the sunset hours. The bottom of the still is covered by 0.2 m aluminum sheet painted black on the side facing the parabolic concentrator to help in absorbing solar radiation reflected from the parabolic concentrator and conducting same to the PCM. To determine the effect of PCM, a solar still without PCM was used to compare with the solar still with PCM. The temperature of water, air temperature, inner surface glass temperature and outer surface glass temperature were measured. Experimental results show that the effect of thermal storage in the parabolic concentrator-coupled single slope solar still increased the productivity by 62%.
Energy Technology Data Exchange (ETDEWEB)
Gueven, H.M. (San Diego State Univ., CA (United States). Dept. of Mechanical Engineering)
1994-08-01
In this paper, a closed-form expression for intercept factor is used to carry out the optimization of parabolic trough collector geometry (rim angle and concentration ratio). It is shown that the presented closed-form expression eliminates the need for a detailed ray-trace computer code and facilitates optimization of the collector optical design parameters.
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Davide Guidetti
2013-12-01
Full Text Available We consider the problem of the reconstruction of the convolution kernel, together with the solution, in a semilinear integrodiential parabolic problem in the case that in the boundary conditions, there appear quite general memory operators.
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M. Mamajonov
2014-06-01
Full Text Available This paper studies the methods of investigation of some boundary value problems for a class of parabolic-hyperbolic equations of the third order in the hexagonal concave areas that take advantage of the study of problems of mathematical physics in the magistracy.
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Ionut Florescu
2010-05-01
Full Text Available We study an integro-differential parabolic problem modelling a process with jumps and stochastic volatility in financial mathematics. Under suitable conditions, we prove the existence of solutions in a general domain using the method of upper and lower solutions and a diagonal argument.
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available We derive necessary and sufficient conditions for global-in-time existence of solutions of ordinary differential, stochastic differential, and parabolic equations. The conditions are formulated in terms of complete Riemannian metrics on extended phase spaces (conditions with two-sided estimates or in terms of derivatives of proper functions on extended phase spaces (conditions with one-sided estimates.
Gilding, B.H.; Kersner, R.
1996-01-01
A degenerate parabolic partial differential equation with a time derivative and first- and second-order derivatives with respect to one spatial variable is studied. The coefficients in the equation depend nonlinearly on both the unknown and the first spatial derivative of a function of the unknown.
Pidaparthi, A. S.; Dall, E. P.; Hoffmann, J. E.; Dinter, F.
2016-05-01
The objective of this paper is to analyse the performance of parabolic trough and power tower technologies by selecting two radiometric stations in different geographic locations, with approximately equal annual direct normal irradiance (DNI) values, but with different monthly DNI distributions. The two stations chosen for this study are situated at the University of Free State, Bloemfontein, Free State Province and in Vanrhynsdorp, Western Cape Province. The annual measured DNI values for both these locations in South Africa are in the range of 2500-2700 kWh/m2. The comparison between the different monthly DNI distributions of these selected sites includes an assessment of annual hourly data in order to study the performance analysis of the most mature concentrating solar power (CSP) technologies, namely parabolic trough and power tower plants. The weather data has been obtained from the Southern African Universities Radiometric Network (SAURAN). A comparison between the different monthly DNI distributions of these selected sites includes the assessment of hourly data. Selection of these radiometric stations has also been done on the basis that they have been operational for at least one year. The first year that most SAURAN stations have been online for at least one year is 2014, thus data from this year has been considered. The annual performance analysis shows that parabolic trough plants have a higher energy yield in Vanrhynsdorp while power tower plants seem to be more suitable for Bloemfontein. Power tower plants in both the locations have a higher annual energy yield when compared with parabolic trough plants. A parabolic trough power plant in Vanrhynsdorp in the Western Cape Province has very low monthly electricity generation in the winter months of May, June, July and August. This is partly due to the higher cosine losses in the parabolic trough `one-axis' tracking systems and lower DNI values in the winter months. However, a power tower plant in
Error Analysis of a Finite Element Method for the Space-Fractional Parabolic Equation
Jin, Bangti
2014-01-01
© 2014 Society for Industrial and Applied Mathematics We consider an initial boundary value problem for a one-dimensional fractional-order parabolic equation with a space fractional derivative of Riemann-Liouville type and order α ∈ (1, 2). We study a spatial semidiscrete scheme using the standard Galerkin finite element method with piecewise linear finite elements, as well as fully discrete schemes based on the backward Euler method and the Crank-Nicolson method. Error estimates in the L2(D)- and Hα/2 (D)-norm are derived for the semidiscrete scheme and in the L2(D)-norm for the fully discrete schemes. These estimates cover both smooth and nonsmooth initial data and are expressed directly in terms of the smoothness of the initial data. Extensive numerical results are presented to illustrate the theoretical results.
Modeling Flow Rate to Estimate Hydraulic Conductivity in a Parabolic Ceramic Water Filter
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Ileana Wald
2012-01-01
Full Text Available In this project we model volumetric flow rate through a parabolic ceramic water filter (CWF to determine how quickly it can process water while still improving its quality. The volumetric flow rate is dependent upon the pore size of the filter, the surface area, and the height of water in the filter (hydraulic head. We derive differential equations governing this flow from the conservation of mass principle and Darcy's Law and find the flow rate with respect to time. We then use methods of calculus to find optimal specifications for the filter. This work is related to the research conducted in Dr. James R. Mihelcic's Civil and Environmental Engineering Lab at USF.
Low-pass parabolic FFT filter for airborne and satellite lidar signal processing.
Jiao, Zhongke; Liu, Bo; Liu, Enhai; Yue, Yongjian
2015-10-14
In order to reduce random errors of the lidar signal inversion, a low-pass parabolic fast Fourier transform filter (PFFTF) was introduced for noise elimination. A compact airborne Raman lidar system was studied, which applied PFFTF to process lidar signals. Mathematics and simulations of PFFTF along with low pass filters, sliding mean filter (SMF), median filter (MF), empirical mode decomposition (EMD) and wavelet transform (WT) were studied, and the practical engineering value of PFFTF for lidar signal processing has been verified. The method has been tested on real lidar signal from Wyoming Cloud Lidar (WCL). Results show that PFFTF has advantages over the other methods. It keeps the high frequency components well and reduces much of the random noise simultaneously for lidar signal processing.
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K. SYED JAFAR
2017-03-01
Full Text Available In this paper, the experimental heat transfer, friction loss and thermal performance data for water flowing through the absorber tube fitted with two different twisted tape configurations in parabolic trough collector (PTC are presented. In the present work, a relative experimental study is carried out to investigate the performance of a PTC influenced by heat transfer through fluidabsorber wall mixing mechanism. The major findings of this experiment show that heat transport enhancement in the nail twisted tape collector perform significantly better than plain twisted tapes and also show that the smallest twisted tape ratio enhances the system performance remarkably maximizing the collector efficiency. The results suggest that the twisted tape and nail twisted tape would be a better option for high thermal energy collection in laminar region of the PTC system.
EMG analysis of human postural responses during parabolic flight microgravity episodes
Layne, Charles S.; Spooner, Brian S.
1990-01-01
Anticipatory postural activity in the trunk and legs precedes rapid shoulder flexion in unit gravity. The hypothesis that anticipatory activity is a component of a single neural command for arm movement was tested by monitoring the surface electromyographic activity of the biceps femoris, paraspinals, and deltoid muscles of three subjects during the microgravity phase of parabolic flight. If part of a single command, anticipatory postural activity would be expected to remain intact despite the absence of the body's center of gravity in a reduced gravity environment. However, in at least 75 percent of the microgravity trials anticipatory biceps femoris activity was absent, indicating a separation of postural and agonist muscle activity. Such a finding suggests that anticipatory postural biceps femoris activity may be initiated independently of agonist (deltoid) activity.
Design and modeling of solar parabolic trough power plant with MATLAB
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Mohammad Sanan T.
2017-01-01
Full Text Available With the fact that Malaysia is one of the fast- growing countries, demand of energy increment is rapid. Malaysia is able to obtain ample amount of annual solar radiation due to its location at equator. If this is utilized proficiently and effectively, then, it can suffice the domestic needs as well as the industrial needs in terms of energy consumption. This article proposes a parabolic Trough Power Plant which is designed with 1.2 kW net electric output. Consequently, the results of theoretical calculations are detailed in the article, while, ensuring the analysing of design proposed through the MATLAB software. The results showed that by making use of aperture having an area of approximately 80 m2, maximum useful heat gain of 20701W at 13:00 pm was attained in March. The maximum net power is 11.84 kWh/day in February.
EVALUATION OF A SOLAR DESALINATION SYSTEM, TYPE CYLINDRICAL PARABOLIC CONCENTRATOR FOR SEA WATER
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Carolina Mercado
2015-12-01
Full Text Available In this work, the methodology for the design, construction and commissioning of a solar desalinator, based on a parabolic trough collector and a solar still occurs, is presented. The energy is supplied through the solar collector, which is connected to the distiller. The equipment was set up on the premises of the Universidad Católica del Norte. It is compact, modular, low cost, easy maintenance and long life, with an average production capacity of distilled water of 2.37 l / d, however, it has to be considered that this rate is directly related with weather conditions and sea water flow entering the system, generating an average percentage of 34.04% efficiency. The results obtained with the respective findings, conclusions and recommendations for future projects associated to renewable energy equipment designed analyzed.
Parabolic Trough Reference Plant for Cost Modeling with the Solar Advisor Model (SAM)
Energy Technology Data Exchange (ETDEWEB)
Turchi, C.
2010-07-01
This report describes a component-based cost model developed for parabolic trough solar power plants. The cost model was developed by the National Renewable Energy Laboratory (NREL), assisted by WorleyParsons Group Inc., for use with NREL's Solar Advisor Model (SAM). This report includes an overview and explanation of the model, two summary contract reports from WorleyParsons, and an Excel spreadsheet for use with SAM. The cost study uses a reference plant with a 100-MWe capacity and six hours of thermal energy storage. Wet-cooling and dry-cooling configurations are considered. The spreadsheet includes capital and operating cost by component to allow users to estimate the impact of changes in component costs.
Ramakumar, R.; Bahrami, K.
1981-01-01
This paper discusses the application of field modulated generator systems (FMGS) to dispersed solar-thermal-electric generation from a parabolic dish field with electric transport. Each solar generation unit is rated at 15 kWe and the power generated by an array of such units is electrically collected for insertion into an existing utility grid. Such an approach appears to be most suitable when the heat engine rotational speeds are high (greater than 6000 r/min) and, in particular, if they are operated in the variable speed mode and if utility-grade a.c. is required for direct insertion into the grid without an intermediate electric energy storage and reconversion system. Predictions of overall efficiencies based on conservative efficiency figures for the FMGS are in the range of 25 per cent and should be encouraging to those involved in the development of cost-effective dispersed solar thermal power systems.
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Jian Wang
2009-01-01
Full Text Available We here investigate the existence and uniqueness of the nontrivial, nonnegative solutions of a nonlinear ordinary differential equation: (|f′|p−2f′′+βrf′+αf+(fq′=0 satisfying a specific decay rate: limr→∞rα/βf(r=0 with α:=(p−1/(pq−2p+2 and β:=(q−p+1/(pq−2p+2. Here p>2 and q>p−1. Such a solution arises naturally when we study a very singular self-similar solution for a degenerate parabolic equation with nonlinear convection term ut=(|ux|p−2uxx+(uqx defined on the half line [0,+∞.
CIME course on Regularity Estimates for Nonlinear Elliptic and Parabolic Problems
Lewis, John; Manfredi, Juan J; Salsa, Sandro
2012-01-01
The issue of regularity has played a central role in the theory of Partial Differential Equations almost since its inception, and despite the tremendous advances made it still remains a very fruitful research field. In particular considerable strides have been made in regularity estimates for degenerate and singular elliptic and parabolic equations over the last several years, and in many unexpected and challenging directions. Because of all these recent results, it seemed high time to create an overview that would highlight emerging trends and issues in this fascinating research topic in a proper and effective way. The course aimed to show the deep connections between these topics and to open new research directions through the contributions of leading experts in all of these fields.