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1

Solar cooker  

Microsoft Academic Search

A solar unit is described comprising a solar oven having an open end. A generally concave parabolic main reflector is joined to the oven to move therewith and reflect solar radiation away from the oven. The main reflector has a central opening to the oven open end, a generally parabolic convex secondary reflector for reflecting the radiation from the main

Zwach

1987-01-01

2

Cookers for solar homes  

Microsoft Academic Search

Means of piping solar energy into kitchens were investigated. Two different solar cookers utilising the heat-pipe principle were designed, constructed and tested. A cooker utilising an east-west line focusing collector, designated Mecca-1, was developed for this purpose. The second cooker was a flat-plate heat-pipe cooker, Mecca-2. A single heat pipe in each cooker absorbed the energy at the collector, transported

A. M. A. Khalifa; M. Akyurt; M. M. A. Taha

1986-01-01

3

Solar cooker  

SciTech Connect

A solar unit is described comprising a solar oven having an open end. A generally concave parabolic main reflector is joined to the oven to move therewith and reflect solar radiation away from the oven. The main reflector has a central opening to the oven open end, a generally parabolic convex secondary reflector for reflecting the radiation from the main reflector through the central opening to the open end of the oven, means for mounting the secondary reflector on the main reflector for movement, a frame, and means for mounting the oven on the frame for adjustable movement relative to the frame. This permits adjusting the angular position relative to the earth. The last mentioned means includes means for supporting the oven including first and second pairs of pivot members that respectively have a fist pivot axis and a second pivot axis that extends perpendicular to the first pivot axis. The oven extends between each of the first pivot members and each of the second pivot members.

Zwach, D.M.

1987-09-29

4

Portable solar cooker  

SciTech Connect

A portable solar cooker of the type having an insulated housing with an oven compartment enclosed therein and associated reflector elements is adapted for cooking with the housing and oven compartment in a tilted or level position. When employing only the tilting mode for tracking the sun, reflecting panels are removably attached to the top of the cooker housing. When there is a need to maintain the oven compartment level while tracking the sun during the cooking operation, the reflecting panels are removably mounted on a pivotal frame connected to a telescoping strip assembly which, in turn, is removably mounted on the topside of the cooker housing.

Way, L.V.

1980-09-02

5

Solar Cookers International  

NSDL National Science Digital Library

With diminishing supplies of firewood in many impoverished nations, how can rural people cook food for their families? In 1987, 17 solar cooking Californians started Solar Cookers International (SCI), and produced manuals on how to produce and use a simple solar box cooker. Since then, 30,000 families in eastern and southern Africa have learned to use solar cooking with the assistance of SCI. Visitors should definitely check out the ten-minute video on the homepage that explains the spread of the use of the solar cooker in Africa, which began in refugee camps where food had to be cooked for tens of thousands of people. Eventually, its use spread to rural villages, but the video explains it has been a slow process. Visitors interested in the Solar Review Cooker e-newsletter that is published thrice-yearly can sign up to receive it free, under the "Newsletter" tab. It is also available in dozens of languages, including French, Arabic, and Chinese.

6

Solar cooker. [oven  

Microsoft Academic Search

A solar heating device for the cooking of food is described consisting of a parabolic trough reflector and having support legs attached at the approximate center of gravity of the reflector and oven assembly. The reflector longitudinal supports serving to hold a cooking oven consisting of a bottom of transparent plastic and a detachable top made of insulation and lined

1978-01-01

7

Reflective Solar Cooker  

NSDL National Science Digital Library

In this activity, learners use the Sun's energy to cook marshmallows. Learners construct the solar oven out of simple everyday materials. They experiment to see how the color of the marshmallow (vanilla or chocolate) and height of the straws affect cooking time. Use this activity to introduce learners to solar energy and reflection. Note: this activity requires adult supervision.

Observatory, Mcdonald

2011-01-01

8

Portable solar\\/non-solar cooker  

Microsoft Academic Search

A portable, solar cooker of the type having an insulated housing with an oven compartment and associated reflector elements is adapted for cooking with a portion of the housing removed and using a conventional source of heat such as canned heat, gasfired lantern heat, and the like.

1980-01-01

9

The performance of a solar cooker in Egypt  

Microsoft Academic Search

A simple, efficient solar cooker was designed and its performance in the Egyptian climate was evaluated. The cooker is of the hot box type with a plane booster mirror reflector. The performance of the cooker was measured experimentally for over two years under different working conditions. The test conditions included experiments with and without adjusting the cooker's position for maximum

Said M. A. Ibrahim; Medhat K. El-Reidy

1995-01-01

10

The Performance of a Solar Cooker in Egypt  

Microsoft Academic Search

A simple, efficient solar cooker was designed and its performance in the Egyptian climate was evaluated. The cooker is of the hot box type with a plane booster mirror reflector. The performance of the cooker was measured experimentally for over 2 years under different working conditions. The test conditions include experiments with and without adjusting the cooker's position for maximum

SAID M. A. IBRAHIM; MEDHAT K. EL-REIDY

1993-01-01

11

The performance of a solar cooker in Egypt  

Microsoft Academic Search

A simple, efficient solar cooker was designed and its performance in the Egyptian climate was evaluated. The cooker is of the hot box type with a plane booster mirror reflector. The performance of the cooker was measured experimentally for over 2 years under different working conditions. The test conditions include experiments with and without adjusting the cooker's position for maximum

S. M. A. Ibrahim; M. K. El-Reidy

2009-01-01

12

Theoretical and experimental assessment of a double exposure solar cooker  

Microsoft Academic Search

A novel design of solar cooker is introduced in which the absorber is exposed to solar radiation from the top and the bottom sides. A set of plane diffuse reflectors is used to direct the radiation onto the lower side of the absorber plate. The performance of the new cooker and the conventional box type solar cooker is extensively investigated.

Emad H Amer

2003-01-01

13

Solar Cooker Pringles Can Lesson  

NSDL National Science Digital Library

This classroom learning unit gives students hands-on experience using solar energy. The class will use a Pringles can to cook a hot dog using solar energy. In addition to introducing a practical application of solar energy, this unit will also allow students to think about how clean, renewable energy may be used by people in developing countries. This document may be downloaded in PDF file format.

Orzali, Joe

2011-12-12

14

Through the wall solar cooker  

Microsoft Academic Search

This patent describes a solar appliance for extending from the interior of a kitchen through an exterior wall of the building and beyond a predetermined distance in a cantilever manner to receive and concentrate in the appliance outside of the building, solar radiation rays for cooking purposes comprising: a housing, the housing being mounted to extend from a kitchen through

Kerr

1987-01-01

15

Through the wall solar cooker  

SciTech Connect

This patent describes a solar appliance for extending from the interior of a kitchen through an exterior wall of the building and beyond a predetermined distance in a cantilever manner to receive and concentrate in the appliance outside of the building, solar radiation rays for cooking purposes comprising: a housing, the housing being mounted to extend from a kitchen through an external wall of a building and beyond in a cantilever manner and forming a closed oven, the oven comprising a bottom, glass top, a pair of sides and a first end positioned with access from within the kitchen and comprising an oven door, a first reflective panel member mounted above, juxtapositioned to one edge of the glass top for positioning against the outer surface of the external wall and extending laterally therefrom for receiving and directing solar rays impinging thereon through the glass top and into the oven, and a second double-sided reflective panel mounted above and juxtapositioned to the glass top and extending substantially perpendicular to the first reflective panel for receiving solar rays impinging on either side thereof, and directing the solar rays into the oven.

Kerr, B.P.

1987-04-07

16

The comparison of three types of Indonesian solar box cookers  

Microsoft Academic Search

This paper describes the influences which govern solar box cookers: HS 7534, HS 7033 and the newest design HS 5521. The best of solar cooker, type HS 7033 gave oven temperature of 202°C between 12:00 and 12:45 p.m. on October 7, 1997. Thirty-four units of this type have been field tested since September 1997. It was found that these solar

Herliyani Suharta; A. M. Sayigh; K Abdullah; K Mathew

2001-01-01

17

Fabrication of and performance studies on a low cost solar cooker having an inclined aperture plane  

Microsoft Academic Search

A low cost box-type solar cooker made of two paper carton boxes with crumpled newspaper balls as insulation has been fabricated with a tilted aperture plane. Comparative tests of this cooker have been conducted against a normal type costlier solar cooker with 1000 ml load of water in each of the cookers. It has been observed that on a sunny

M. Hussain; Sirajul Islam Khan

1996-01-01

18

A thermodynamic review on solar box type cookers  

Microsoft Academic Search

Globally there is profuse literature on the continuous developments of box type solar cookers and solar ovens. A lot of research work has been carried out in recent passed years in the world which clearly shown the utilization of solar energy towards the greatest needs of mankind obviously solar cooking, fuel saving, non-polluting environment and to save and produce electricity.

Abhishek Saxena; Varun; S. P. Pandey; G. Srivastav

2011-01-01

19

Cookin' with Sun: Design and Build Solar Cookers  

ERIC Educational Resources Information Center

Having students design and construct solar cookers is a great way to teach them about designing to meet human needs and about many basic global issues related to health and the environment. Because the activity includes solid content from the fields of math, science and technology, it is an excellent vehicle for technology educators who want to…

Brand, Lance; Warren, Ande; Fitzgerald, Mike

2006-01-01

20

A novel advanced box-type solar cooker  

SciTech Connect

An advanced version of the box-type solar cooker is presented: a fixed cooking vessel in good thermal contact with a conductive absorber plate is set into the glazing; the results are improved thermal performance, easier access to the cooking vessel and less frequent maintenance due to protection of all absorbing and reflecting surfaces. Outdoor tests show that 5 liters of water per sq m of opening surface can be brought to full boiling in less than one hour. A finite element simulation model of the advanced box cooker is presented. It is shown that the most decisive parameters are absorber-to-pot heat transfer and absorber conductivity. Field tests in Ethiopia and India are under way, local production in India has started.

Grupp, M.; Montagne, P.; Wackernagel, M. (Synopsis Inst., Lodeve (France))

1991-01-01

21

Parabolic trough solar collector  

SciTech Connect

A parabolic trough solar collector using reflective flexible materials is disclosed. A parabolic cylinder mirror is formed by stretching a flexible reflecting material between two parabolic end formers. The formers are held in place by a spreader bar. The resulting mirror is made to track the sun, focusing the sun's rays on a receiver tube. The ends of the reflective material are attached by glue or other suitable means to attachment straps. The flexible mirror is then attached to the formers. The attachment straps are mounted in brackets and tensioned by tightening associated nuts on the ends of the attachment straps. This serves both to stretch the flexible material orthogonal to the receiver tube and to hold the flexible material on the formers. The flexible mirror is stretched in the direction of the receiver tube by adjusting tensioning nuts. If materials with matching coefficients of expansion for temperature and humidity have been chosen, for example, aluminum foil for the flexible mirror and aluminum for the spreader bar, the mirror will stay in adjustment through temperature and humidity excursions. With dissimilar materials, e.g., aluminized mylar or other polymeric material and steel, spacers can be replaced with springs to maintain proper adjustment. The spreader bar cross section is chosen to be in the optic shadow of the receiver tube when tracking and not to intercept rays of the sun that would otherwise reach the receiver tube. This invention can also be used to make non-parabolic mirrors for other apparatus and applications.

Eaton, J.H.

1985-01-15

22

Solar cooker and method of assembly  

Microsoft Academic Search

A method of assembling from kit components a solar oven and in so doing, teaching the assembler the principals involving insulation, reflection, solar ray conversion to heat, temperature conservation and the fine art of cookery is described.

Kerr

1980-01-01

23

Ultra low cost solar cookers: design details and field trials in Tanzania  

Microsoft Academic Search

A family-sized ultra low cost solar cooker has been developed. The hot box style cooker is designed to be built on site by the users with minimal tools, skills or special materials. It consists of a shallow 1 m2 square hole in the ground, insulated with straw and lined with adobe (mud and straw), a glass or plastic roof, and

Paul Robinson

1997-01-01

24

Design and measured performance of a plane reflector augmented box-type solar-energy cooker  

Microsoft Academic Search

The design philosophy, construction and measured performances of a plane-reflector augmented box-type solar-energy cooker are presented. The experimental solar cooker consists of an aluminum plate absorber painted matt black and a double-glazed lid. The bottom and sides are lagged with fibreglass wool insulator. The reflector consists of a wooden-framed commercially available specular plane mirror which is sized to form a

O. V Ekechukwu; N. T Ugwuoke

2003-01-01

25

Shenandoah parabolic dish solar collector  

SciTech Connect

The objectives of the Shenandoah, Georgia, Solar Total Energy System are to design, construct, test, and operate a solar energy system to obtain experience with large-scale hardware systems for future applications. This report describes the initial design and testing activities conducted to select and develop a collector that would serve the need of such a solar total energy system. The parabolic dish was selected as the collector most likely to maximize energy collection as required by this specific site. The fabrication, testing, and installation of the parabolic dish collector incorporating improvements identified during the development testing phase are described.

Kinoshita, G.S.

1985-01-01

26

The oven receiver: An approach toward the revival of concentrating solar cookers  

Microsoft Academic Search

Concentrating type solar cookers are expected to demonstrate high performance because of the large collection area employed. However, the net amount of heat used is still low. This is greatly attributed to the large amount of heat losses from the bare food pots used. Introducing the oven type concept as an alternative approach for collecting the concentrated solar energy would

M. B. Habeebullah; A. M. Khalifa; I. Olwi

1995-01-01

27

Parametric optimization of a box-type solar cooker with an inbuilt paraboloid reflector using Cramer's rule  

Microsoft Academic Search

An attempt was made to optimize the parameters that influence the performance of a box-type solar cooker with an inbuilt paraboloid reflector using Cramer's rule. Explicit expressions were derived for the temperature of the base of the cooking vessel, cooking fluid, stagnant air inside the box and lid of the cooking vessel. Simulation modelling of the cooker was proposed for

D. Venugopal; J. Chandrasekaran; B. Janarthanan; S. Shanmugan; S. Kumar

2011-01-01

28

Parametric optimization of a box-type solar cooker with an inbuilt paraboloid reflector using Cramer's rule  

Microsoft Academic Search

An attempt was made to optimize the parameters that influence the performance of a box-type solar cooker with an inbuilt paraboloid reflector using Cramer's rule. Explicit expressions were derived for the temperature of the base of the cooking vessel, cooking fluid, stagnant air inside the box and lid of the cooking vessel. Simulation modelling of the cooker was proposed for

D. Venugopal; J. Chandrasekaran; B. Janarthanan; S. Shanmugan; S. Kumar

2012-01-01

29

Parabolic Trough Solar Thermal Electric Power Plants  

SciTech Connect

Although many solar technologies have been demonstrated, parabolic trough solar thermal electric power plant technology represents one of the major renewable energy success stories of the last two decades.

Not Available

2003-06-01

30

Oven receiver: An approach toward the revival of concentrating solar cookers  

SciTech Connect

Concentrating type solar cookers are expected to demonstrate high performance because of the large collection area employed. However, the net amount of heat used is still low. This is greatly attributed to the large amount of heat losses from the bare food pots used. Introducing the oven type concept as an alternative approach for collecting the concentrated solar energy would drastically boost the overall cooker efficiency. In this work, the transient heat balance equations were developed for predicting the thermal behavior of an oven type concentrating solar cooker. This simulation was used to show theoretically the great advantage of using a glass-sided oven over the conventional bare receiver pot. The resulting mathematical model was solved using numerical integration. The transient nature of solar radiation and effects of wind speed variation were all taken into consideration. The analysis showed that the oven type receiving pot has both a higher fluid temperature and overall receiver efficiency compared to the bare receiver type, working under similar conditions. 18 refs., 12 figs., 3 tabs.

Habeebullah, M.B.; Khalifa, A.M.; Olwi, I. [King Abdulaziz Univ., Jeddah (Saudi Arabia)] [King Abdulaziz Univ., Jeddah (Saudi Arabia)

1995-04-01

31

A solar cooker using vacuum-tube collectors with integrated heat pipes  

Microsoft Academic Search

A solar cooking system is described which consists of a vacuum-tube collector with integrated long heat pipes directly leading to the oven plate. The cooker was tested during several clear days in Marburg (latitude 51°). The heat-up times were measured under cold- and hot-start conditions. Detailed temperature distributions and their time dependences were measured. The maximum temperature obtained in a

A. Balzar; P. Stumpf; S. Eckhoff; H. Ackermann; M. Grupp

1996-01-01

32

Solar Parabolic Dish Annual Technology Evaluation Report  

NASA Technical Reports Server (NTRS)

The activities of the JPL Solar Thermal Power Systems Parabolic Dish Project for FY 1982 are summarized. Included are discussions on designs of module development including their concentrator, receiver, and power conversion subsystems. Analyses and test results, along with progress on field tests, Small Community Experiment System development, and tests at the Parabolic Dish Test Site are also included.

1983-01-01

33

Solar parabolic dish technology evaluation report  

NASA Technical Reports Server (NTRS)

The activities of the JPL Solar Thermal Power Systems Parabolic Dish Project for FY 1983 are summarized. Included are discussions on designs of module development including concentrator, receiver, and power conversion subsystems together with a separate discussion of field tests, Small Community Experiment system development, and tests at the Parabolic Dish Test Site.

Lucas, J. W.

1984-01-01

34

Solar cookers—cheap technology with high ecological benefits  

Microsoft Academic Search

This study discusses the quality and quantity of energy used for cooking in Costa Rica and in the world as a whole, and then compares the advantages and limitations of solar ovens with conventional firewood and electric stoves. The payback period of a common hot box type solar oven, even if used 6–8 months a year, is around 12–14 months.

Shyam S. Nandwani

1996-01-01

35

Instrumentation error analysis of a paraboloid concentrator type solar cooker  

Microsoft Academic Search

An effective quality control is essential for a large-scale dissemination of solar thermal technologies on the products being offered by the industry to the end users. For this, there is a need to establish test procedures and methodologies for producing performance characteristic parameters, which could provide an equitable basis for comparison of performances of these products. At present, paraboloid concentrator

Ishan Purohit; Pallav Purohit

2009-01-01

36

Solar Thermal Power Systems parabolic dish project  

NASA Technical Reports Server (NTRS)

The status of the Solar Thermal Power Systems Project for FY 1980 is summarized. Included is: a discussion of the project's goals, program structure, and progress in parabolic dish technology. Analyses and test results of concentrators, receivers, and power converters are discussed. Progress toward the objectives of technology feasibility, technology readiness, system feasibility, and system readiness are covered.

Truscello, V. C.

1981-01-01

37

Building a parabolic solar concentrator prototype  

NASA Astrophysics Data System (ADS)

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.

Escobar-Romero, J. F. M.; Montiel, S. Vázquez y.; Granados-Agustín, F.; Cruz-Martínez, V. M.; Rodríguez-Rivera, E.; Martínez-Yáñez, L.

2011-01-01

38

Alignment method for parabolic trough solar concentrators  

DOEpatents

A Theoretical Overlay Photographic (TOP) alignment method uses the overlay of a theoretical projected image of a perfectly aligned concentrator on a photographic image of the concentrator to align the mirror facets of a parabolic trough solar concentrator. The alignment method is practical and straightforward, and inherently aligns the mirror facets to the receiver. When integrated with clinometer measurements for which gravity and mechanical drag effects have been accounted for and which are made in a manner and location consistent with the alignment method, all of the mirrors on a common drive can be aligned and optimized for any concentrator orientation.

Diver, Richard B. (Albuquerque, NM)

2010-02-23

39

Modelling of parabolic trough direct steam generation solar collectors  

Microsoft Academic Search

Solar electric generation systems (SEGS) currently in operation are based on parabolic trough solar collectors using synthetic oil heat transfer fluid in the collector loop to transfer thermal energy to a Rankine cycle turbine via a heat exchanger. To improve performance and reduce costs direct steam generation in the collector has been proposed. In this paper the efficiency of parabolic

S. D. Odeh; G. L. Morrison; M. Behnia

1998-01-01

40

Steam engine research for solar parabolic dish  

NASA Technical Reports Server (NTRS)

The parabolic dish solar concentrator provides an opportunity to generate high grade energy in a modular system. Most of the capital is projected to be in the dish and its installation. Assurance of a high production demand of a standard dish could lead to dramatic cost reductions. High production volume in turn depends upon maximum application flexibility by providing energy output options, e.g., heat, electricity, chemicals and combinations thereof. Subsets of these options include energy storage and combustion assist. A steam engine design and experimental program is described which investigate the efficiency potential of a small 25 kW compound reheat cycle piston engine. An engine efficiency of 35 percent is estimated for a 700 C steam temperature from the solar receiver.

Demler, R. L.

1981-01-01

41

Proceedings of the Fifth Parabolic Dish Solar Thermal Power Program  

NASA Technical Reports Server (NTRS)

The proceedings of the Fifth Parabolic Dish Solar Thermal Power Program Annual Review are presented. 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 were emphasized. Among the topics discussed were: overall Project and Program aspects, Stirling and Brayton module development, concentrator and engine/receiver development along with associated hardware and test results; distributed systems operating experience; international parabolic dish development activities; and non-DOE-sponsored domestic dish activities. Solar electric generation was also addressed.

Lucas, J. W. (editor)

1984-01-01

42

Fifth Parabolic Dish Solar Thermal Power Program Annual Review: Proceedings.  

National Technical Information Service (NTIS)

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 techn...

1984-01-01

43

Solar Parabolic Dish Annual Technology Evaluation Report. Fiscal Year 1982.  

National Technical Information Service (NTIS)

This report summarizes the activities of the JPL Solar Thermal Power Systems Parabolic Dish Project for FY 1982. Included are discussions on designs of module development including their concentrator, receiver, and power conversion subsystems. Analyses an...

1983-01-01

44

Test results, Industrial Solar Technology parabolic trough solar collector  

SciTech Connect

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.

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

45

Solar Thermal Power Plants with Parabolic-Trough Collectors  

NASA Astrophysics Data System (ADS)

Parabolic-trough collectors (PTC) are solar concentrating devices suitable to work in the 150°C- 400°C temperature range. Power plants based on this type of solar collectors are a very efficient way to produce electricity with solar energy. At present, there are eight commercial solar plants (called SEGS-II, III,.. IX) producing electricity with parabolic-trough collectors and their total output power is 340 MW. Though all SEGS plants currently in operation use thermal oil as a heat transfer fluid between the solar field and the power block, direct steam generation (DSG) in the receiver tubes is a promising option to reduce the cost of electricity produced with parabolic- trough power plants. Most of technical uncertainties associated to the DSG technology were studied and solved in the DISS project and it is expected that this new technology will be commercially available in a short term. In Spain, the Royal Decree No. 436/204 (March 12th , 2004) has defined a premium of 0,18€/kWh for the electricity produced by solar thermal power plants, thus promoting the installation of solar thermal power plants up to a limit of 200 MW. Due to the current legal and financial framework defined in Spain, several projects to install commercial solar power plants with parabolic-trough collectors are currently underway.

Zarza, E.; Valenzuela, L.; León, J.

2004-12-01

46

Heat transfer analysis of parabolic trough solar receiver  

Microsoft Academic Search

Solar Parabolic Trough Collectors (PTCs) are currently used for the production of electricity and applications with relatively higher temperatures. A heat transfer fluid circulates through a metal tube (receiver) with an external selective surface that absorbs solar radiation reflected from the mirror surfaces of the PTC. In order to reduce the heat losses, the receiver is covered by an envelope

Ricardo Vasquez Padilla; Gokmen Demirkaya; D. Yogi Goswami; Elias Stefanakos; Muhammad M. Rahman

2011-01-01

47

Federal technology alert. Parabolic-trough solar water heating  

SciTech Connect

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.

NONE

1998-04-01

48

Cascaded latent heat storage for parabolic trough solar power plants  

Microsoft Academic Search

The current revival of solar thermal electricity generating systems (SEGS) unveils the still existing need of economic thermal energy storages (TES) for the temperature range from 250°C to 500°C. The TES-benchmark for parabolic trough power plants is the direct two tank storage, as it was used at the SEGS I plant near Barstow (USA). With the introduction of expensive synthetic

Horst Michels; Robert Pitz-Paal

2007-01-01

49

Beaming-In On Student-Made Solar Technology  

ERIC Educational Resources Information Center

Completion of a unit on heat energy motivated students to devise their own solar collectors, parabolic solar cookers, and designs for a solar home. Using their solar projects, the students tests hypotheses they might have had concerning heating capacities, insulation values, or energy conversions. (MA)

Chiotelis, Charles L.

1978-01-01

50

Performance contracting for parabolic trough solar thermal systems  

SciTech Connect

Several applications of solar energy have proven viable in the energy marketplace, due to competitive technology and economic performance. One example is the parabolic trough solar collectors, which use focused solar energy to maximize efficiency and reduce material use in construction. Technical improvements are complemented by new business practices to make parabolic trough solar thermal systems technically and economically viable in an ever widening range of applications. Technical developments in materials and fabrication techniques reduce production cost and expand applications from swimming pool heating and service hot water, to higher-temperature applications such as absorption cooling and process steam. Simultaneously, new financing mechanisms such as a recently awarded US Department of Energy (DOE) Federal Energy Management Program (FEMP) indefinite quantity Energy Savings Performance Contract (Super ESPC) facilitate and streamline implementation of the technology in federal facilities such as prisons and military bases.

Brown, H.; Hewett, R.; Walker, A. [National Renewable Energy Lab., Golden, CO (United States); Gee, R.; May, K. [Industrial Solar Technology, Golden, CO (United States)

1997-12-31

51

Subsystems design and component development for the parabolic dish module for solar thermal power systems  

NASA Technical Reports Server (NTRS)

Solar thermal power systems parabolic dish activities are summarized. Subsystem designs of concentrators, receivers, engines, power converters, and thermal transport are discussed. Analyses, test results, field tests, small community system development and the parabolic dish test site are also included.

Stein, C. K.

1982-01-01

52

Irrigation market for solar thermal parabolic dish systems  

NASA Technical Reports Server (NTRS)

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.

Habib-Agahi, H.; Jones, S. C.

1981-01-01

53

Irrigation market for solar thermal parabolic dish systems  

NASA Astrophysics Data System (ADS)

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.

Habib-Agahi, H.; Jones, S. C.

1981-09-01

54

Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint  

SciTech Connect

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.

Stynes, J. K.; Ihas, B.

2012-04-01

55

Proceedings: Fourth Parabolic Dish Solar Thermal Power Program Review  

NASA Technical Reports Server (NTRS)

The results of activities within the parabolic dish technology and applications development program are presented. Stirling, organic Rankine and Brayton module technologies, associated hardware and test results to date; concentrator development and progress; economic analyses; and international dish development activities are covered. Two panel discussions, concerning industry issues affecting solar thermal dish development and dish technology from a utility/user perspective, are also included.

1983-01-01

56

Secondary concentrators for parabolic dish solar thermal power systems  

NASA Technical Reports Server (NTRS)

A variety of different concepts are currently being studied with the objective to lower the cost of parabolic mirrors and to provide alternatives. One of the considered approaches involves the use of compound concentrators. A compound solar concentrator is a concentrator in which the sunlight is reflected or refracted more than once. It consists of a primary mirror or lens, whose aperture determines the amount of sunlight gathered, and a smaller secondary mirror or lens. Additional small optical elements may also be incorporated. The possibilities and problems regarding a use of compound concentrators in parabolic dish systems are discussed. Attention is given to concentrating secondary lenses, secondary imaging and concentrating mirrors, conical secondary mirrors, compound elliptic secondary concentrating mirrors, and hyperbolic trumpet secondary concentrating mirrors.

Jaffe, L. D.; Poon, P. T.

1981-01-01

57

Fifth parabolic dish solar thermal power program annual review: proceedings  

SciTech Connect

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.

None

1984-03-01

58

Validation of the FLAGSOL parabolic trough solar power plant performance model  

NASA Astrophysics Data System (ADS)

This paper describes the results of a validation of the FLAGSOL parabolic trough solar power plant performance model. The validation was accomplished by simulating an operating solar electric generating system (SEGS) parabolic trough solar thermal power plant and comparing the model output results with actual plant operating data. This comparison includes instantaneous, daily, and annual total solar thermal electric output, gross solar electric generation, and solar mode parasitic electric consumption. The results indicate that the FLAGSOL model adequately predicts the gross solar electric output of an operating plant, both on a daily and an annual basis.

Price, H. W.; Svoboda, P.; Kearney, D.

1994-10-01

59

Optical characterization of solar furnace system using fixed geometry nonimaging focusing heliostat and secondary parabolic concentrator  

Microsoft Academic Search

A novel solar furnace system has been proposed to be consisted of a Nonimaging Focusing Heliostat and a smaller parabolic concentrator. In this configuration, the primary heliostat consists of 11×11 array of concave mirrors with a total reflective area of 121 m2 while the secondary parabolic concentrator has a focal length of 30 cm. To simplify the design and reduce

Kok-Keong Chong; Chuan-Yang Lim; Wee-Liang Keh; Jian-Hau Fan; Faidz Abdul Rahman

2011-01-01

60

Wind Tunnel Tests of Parabolic Trough Solar Collectors: March 2001--August 2003  

SciTech Connect

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.

Hosoya, N.; Peterka, J. A.; Gee, R. C.; Kearney, D.

2008-05-01

61

Slope Error Measurement Tool for Solar Parabolic Trough Collectors: Preprint  

SciTech Connect

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.

Stynes, J. K.; Ihas, B.

2012-04-01

62

TRNSYS MODELING OF THE SEGS VI PARABOLIC TROUGH SOLAR ELECTRIC GENERATING SYSTEM  

Microsoft Academic Search

A detailed performance model of the 30 MWe SEGS VI parabolic trough plant was created in the TRNSYS simulation environment using the Solar Thermal Electric Component model library. Both solar and power cycle performance were modeled, but natural gas-fired hybrid operation was not. Good agreement between model predictions and plant measurements was found, with errors usually less than 10%, and

Scott A. Jones; Robert Pitz-Paal; Peter Schwarzboezl; Nathan Blair; Robert Cable

2001-01-01

63

Optical analysis of parabolic dish concentrators for solar dynamic power systems in space  

Microsoft Academic Search

An optical analysis of a parabolic solar collection system operating in Earth orbit was performed using ray tracing techniques. The analysis included the effects of: (1) solar limb darkening, (2) parametric variation of mirror surface error, (3) parametric variation of mirror rim angle, and (4) parametric variation of alignment and pointing error. This ray tracing technique used numerical integration to

1985-01-01

64

Simulation of solar lithium bromide–water absorption cooling system with parabolic trough collector  

Microsoft Academic Search

Ahwaz is one of the sweltering cities in Iran where an enormous amount of energy is being consumed to cool residential places in a year. The aim of this research is to simulate a solar single effect lithium bromide–water absorption cooling system in Ahwaz. The solar energy is absorbed by a horizontal N–S parabolic trough collector and stored in an

M. Mazloumi; M. Naghashzadegan; K. Javaherdeh

2008-01-01

65

Efficiency improvement of solar cell using compound parabolic concentrator and sun tracking system  

Microsoft Academic Search

This paper presents how the efficiency of solar cell can be increased with the design of compound parabolic concentrator (CPC) and the implementation of sun tracking system. Sun tracking systems is an application of the machine vision (MV) and collaboration with data acquisition (DAQ) to systems by using a webcamera as a sensor and sound card as an output channel

Eklas Hossain; Riza Muhida; A. Ali

2008-01-01

66

Secondary and Compound Concentrators for Parabolic-Dish Solar-Thermal Power Systems.  

National Technical Information Service (NTIS)

A secondary optical element may be added to a parabolic dish solar concentrator to increase the geometric concentration ratio attainable at a given intercept factor. This secondary may be a Fresnel lens or a mirror, such as a compound elliptic concentrato...

L. D. Jaffe P. T. Poon

1981-01-01

67

Study of a new solar adsorption refrigerator powered by a parabolic trough collector  

Microsoft Academic Search

This paper presents the study of solar adsorption cooling machine, where the reactor is heated by a parabolic trough collector (PTC) and is coupled with a heat pipe (HP). This reactor contains a porous medium constituted of activated carbon, reacting by adsorption with ammonia.We have developed a model, based on the equilibrium equations of the refrigerant, adsorption isotherms, heat and

A. El Fadar; A. Mimet; A. Azzabakh; M. Pérez-García; J. Castaing

2009-01-01

68

Modeling of a Parabolic Trough Solar Field for Acceptance Testing: A Case Study  

SciTech Connect

As deployment of parabolic trough concentrating solar power (CSP) systems ramps up, the need for reliable and robust performance acceptance test guidelines for the solar field is also amplified. Project owners and/or EPC contractors often require extensive solar field performance testing as part of the plant commissioning process in order to ensure that actual solar field performance satisfies both technical specifications and performance guaranties between the involved parties. Performance test code work is currently underway at the National Renewable Energy Laboratory (NREL) in collaboration with the SolarPACES Task-I activity, and within the ASME PTC-52 committee. One important aspect of acceptance testing is the selection of a robust technology performance model. NREL1 has developed a detailed parabolic trough performance model within the SAM software tool. This model is capable of predicting solar field, sub-system, and component performance. It has further been modified for this work to support calculation at subhourly time steps. This paper presents the methodology and results of a case study comparing actual performance data for a parabolic trough solar field to the predicted results using the modified SAM trough model. Due to data limitations, the methodology is applied to a single collector loop, though it applies to larger subfields and entire solar fields. Special consideration is provided for the model formulation, improvements to the model formulation based on comparison with the collected data, and uncertainty associated with the measured data. Additionally, this paper identifies modeling considerations that are of particular importance in the solar field acceptance testing process and uses the model to provide preliminary recommendations regarding acceptable steady-state testing conditions at the single-loop level.

Wagner, M. J.; Mehos, M. S.; Kearney, D. W.; McMahan, A. C.

2011-01-01

69

Use of parabolic trough collectors for residential/light commercial solar cooling systems  

SciTech Connect

Parabolic troughs and some other high-temperature solar collectors should become cost-competitive with flat-plate collectors in the next decade. In this study, the potential for using these collectors as residential/light commercial solar cooling devices is considered. An overview of the effects of high source temperature on the absorption cycle, the desiccant cycle, and the heat-engine-driven vapor compression cycle is given. Coefficients of performance (COP) over 1.0 are possible with all three types of cycles driven by parabolic troughs. A double effect absorption machine was chosen to represent these advanced concept devices and a seasonal performance comparison was made with a flat-plate-driven absorption cycle. Similar seasonal performance was observed for the trough-driven cycle with 40% less collector area than the flat-plate cycle. A similar reduction in backup fuel requirements was also noted.

Copeland, R.J.; Parsons, J.R.

1982-08-01

70

Solar reforming of methane in a direct absorption catalytic reactor on a parabolic dish  

SciTech Connect

The concept of solar driven chemical reactions in a commercial-scale volumetric receiver/reactor on a parabolic concentrator was successfully demonstrated in the CAtalytically Enhanced Solar Absorption Receiver (CAESAR) test. Solar reforming of methane (CH{sub 4}) with carbon dioxide (CO{sub 2}) was achieved in a 64-cm diameter direct absorption reactor on a parabolic dish capable of 150 kW solar power. The reactor was a catalytic volumetric absorber consisting of a multi-layered, porous alumina foam disk coated with rhodium (Rh) catalyst. The system was operated during both steady-state and solar transient (cloud passage) conditions. The total solar power absorbed reached values up to 97 kW and the maximum methane conversion was 70%. Receiver thermal efficiencies ranged up to 85% and chemical efficiencies peaked at 54%. The absorber performed satisfactorily in promoting the reforming reaction during the tests without carbon formation. However, problems of cracking and degradation of the porous matrix, nonuniform dispersion of the Rh through the absorber, and catalyst deactivation due to sintering and possible encapsulation, must be resolved to achieve long-term operation and eventual commercialization. 17 refs., 11 figs., 1 tab.

Muir, J.F.; Hogan, R.E. Jr.; Skocypec, R.D. (Sandia National Labs., Albuquerque, NM (USA)); Buck, R. (Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Stuttgart (Germany, F.R.). Inst. fuer Technische Thermodynamik)

1990-01-01

71

Concentrating Solar Power, Seawater Desalination, Parabolic Troughs, Fresnel Systems  

Microsoft Academic Search

Today's conflicts on oil are tomorrow's conflicts on water has become a popular issue to describe the enduring water and energy crisis, although solution for both energy and water shortage seems to be on hand: Making power and water from sun and sea. Concentrating solar power (CSP) offers a sustainable alternative to fossil fuels for large scale seawater desalination. CSP

V. K. SethiE; Mukesh Pandey; Priti Shukla; R. G. P. V. Bhopal

2012-01-01

72

Optical characterization of solar furnace system using fixed geometry nonimaging focusing heliostat and secondary parabolic concentrator  

NASA Astrophysics Data System (ADS)

A novel solar furnace system has been proposed to be consisted of a Nonimaging Focusing Heliostat and a smaller parabolic concentrator. In this configuration, the primary heliostat consists of 11×11 array of concave mirrors with a total reflective area of 121 m2 while the secondary parabolic concentrator has a focal length of 30 cm. To simplify the design and reduce the cost, fixed geometry of the primary heliostat is adopted to omit the requirement of continuous astigmatic correction throughout a year. The overall performance of the novel solar furnace configuration can be optimized if the heliostat's spinning-axis is fixed in the orientation dependent on the latitude angle so that the annual variation of incidence angle is the least, which ranges from 33° to 57°. Case study of the novel solar furnace system has been performed with the use of ray-tracing method to simulate solar flux distribution profile for two different target distances, i.e. 50 m and 100 m. The simulated results have revealed that the maximum solar concentration ratio ranges from 20,530 suns to 26,074 suns for the target distance of 50 m, and ranges from 40,366 suns to 43,297 suns for the target distance of 100 m.

Chong, Kok-Keong; Lim, Chuan-Yang; Keh, Wee-Liang; Fan, Jian-Hau; Rahman, Faidz Abdul

2011-09-01

73

Thermal buffering of receivers for parabolic dish solar thermal power plants  

NASA Technical Reports Server (NTRS)

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.

Manvi, R.; Fujita, T.; Gajanana, B. C.; Marcus, C. J.

1980-01-01

74

Cost/performance of solar reflective surfaces for parabolic dish concentrators  

NASA Technical Reports Server (NTRS)

Materials for highly reflective surfaces for use in parabolic dish solar concentrators are discussed. Some important factors concerning performance of the mirrors are summarized, and typical costs are treated briefly. Capital investment cost/performance ratios for various materials are computed specifically for the double curvature parabolic concentrators using a mathematical model. The results are given in terms of initial investment cost for reflective surfaces per thermal kilowatt delivered to the receiver cavity for various operating temperatures from 400 to 1400 C. Although second surface glass mirrors are emphasized, first surface, chemically brightened and anodized aluminum surfaces as well as second surface, metallized polymeric films are treated. Conventional glass mirrors have the lowest cost/performance ratios, followed closely by aluminum reflectors. Ranges in the data due to uncertainties in cost and mirror reflectance factors are given.

Bouquet, F.

1980-01-01

75

Experiments with an Induction Cooker  

ERIC Educational Resources Information Center

The induction cooker is a common appliance nowadays. How does it work? Why is it not possible to use aluminium utensils with it? What experiments can be carried out with it (at different levels) and not only in physics lessons? Searching for the answers to these and other questions is the purpose of this article. (Contains 5 figures.)

Zilavy, Peter

2009-01-01

76

Cost-effective solar furnace system using fixed geometry Non-Imaging Focusing Heliostat and secondary parabolic concentrator  

Microsoft Academic Search

A novel cost-effective solar furnace system is proposed to be consisted of a Non-Imaging Focusing Heliostat (NIFH) and a much smaller parabolic concentrator. In order to simplify the design and hence leading to the cost reduction, a fixed geometry of the NIFH heliostat is adopted in the novel solar furnace system by omitting the requirement of continuous astigmatic correction throughout

K. K. Chong; C. Y. Lim; C. W. Hiew

2011-01-01

77

Enhancing Optical Efficiency of a Linear Parabolic Solar Collector through Nanofluids  

NASA Astrophysics Data System (ADS)

This paper explores different types of nanofluids (namely aluminium nanoparticles dispersed in water, ethylene glycol, propylene glycol and therminol VP-1) for their suitability as working fluid in direct absorption linear parabolic solar collectors. Lambert Beer's law has been invoked to compute intensity attenuation as it passes through the nanofluid. Intensity attenuation and subsequent energy transfer takes place through absorption and scattering of solar radiations by the participating media (nanofluid). The current analysis quantitatively compares the solar energy capturing capacity for the four nanofluids. Optical efficiency as a function of receiver radius and volume fraction of nanoparticles has been computed for the four nanofluids, also thermal efficiency as a function of volume fraction has been found out.

Khullar, Vikrant; Tyagi, Himanshu

2011-10-01

78

Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems  

NASA Technical Reports Server (NTRS)

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.

Ramakumar, R.; Bahrami, K.

1981-01-01

79

Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems  

NASA Astrophysics Data System (ADS)

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.

Ramakumar, R.; Bahrami, K.

80

Optical analysis of parabolic dish concentrators for solar dynamic power systems in space  

NASA Technical Reports Server (NTRS)

An optical analysis of a parabolic solar collection system operating in Earth orbit was performed using ray tracing techniques. The analysis included the effects of: (1) solar limb darkening, (2) parametric variation of mirror surface error, (3) parametric variation of mirror rim angle, and (4) parametric variation of alignment and pointing error. This ray tracing technique used numerical integration to combine the effects of rays emanating from different parts of the sun at different intensities with the effects of normally distributed mirror-surface errors to compute the angular intensity distribution of rays leaving the mirror surface. A second numerical integration was then performed over the surface of the parabolic mirror to compute the radial distribution of brightness at the mirror focus. Major results of the analysis included: (1) solar energy can be collected at high temperatures with high efficiency, (2) higher absorber temperatures can be achieved at lower efficiencies, or higher efficiencies can be achieved at lower temperatures, and (3) collection efficiency is near its maximum level across a broad plateau of rim angles from 40 deg to 70 deg.

Jefferies, K. S.

1985-01-01

81

Test results on parabolic dish concentrators for solar thermal power systems  

NASA Technical Reports Server (NTRS)

This paper presents results of development testing of various solar thermal parabolic dish concentrators. The concentrators were mostly designed for the production of electric power using dish-mounted Rankine, Brayton or Stirling cycle engines, intended to be produced at low cost. Measured performance for various dishes included optical efficiencies ranging from 0.32 to 0.86 at a geometric concentration ratio of 500, and from about 0.09 to 0.85 at a geometric concentration ratio of 3000. Some malfunctions were observed. The tests should provide operating information of value in developing concentrators with improved performance and reduced maintenance.

Jaffe, Leonard D.

1989-01-01

82

Solar Energy.  

National Technical Information Service (NTIS)

Water pumps, solar power stations, air conditioners, fresh-water stills, solar homes, solar cookers, fruit driers, devices for (low temperature) steaming of reinforced concrete members, solar refrigerators, solar hothouses, welding and melting of metals p...

A. A. Yershov G. Y. Umarov

1975-01-01

83

Slow Cookers and Food Safety  

MedlinePLUS

... Administrative Forms Standard Forms Skip Navigation Z7_0Q0619C0JGR010IFST1G5B10H1 Web Content Viewer (JSR 286) Actions ${title} Loading... / Topics / ... Safety / Slow Cookers and Food Safety Z7_0Q0619C0JGR010IFST1G5B10H3 Web Content Viewer (JSR 286) Actions ${title} Loading... Z7_ ...

84

Particle Emissions from Domestic Gas Cookers  

Microsoft Academic Search

The authors experimentally studied the formation of submicron particles from a domestic gas cooker in a compartment free from external particle sources. The effects of fuel (methane, natural gas, odorant-free natural gas), primary aeration, flow rate, and fuel sulphur content on particle emissions were investigated. The experiments confirmed reports from literature that blue burning flames of domestic gas cookers emit

Ayten Yilmaz Wagner; Hans Livbjerg; Per Gravers Kristensen; Peter Glarborg

2010-01-01

85

Summary assessment of solar thermal parabolic dish technology for electrical power generation  

NASA Technical Reports Server (NTRS)

An assessment is provided of solar thermal parabolic dish technology for electrical power generation. The assessment is based on the development program undertaken by the Jet Propulsion Laboratory for the U.S. Department of Energy and covers the period from the initiation of the program in 1976 through mid-1984. The program was founded on developing components and subsystems that are integrated into parabolic dish power modules for test and evaluation. The status of the project is summarized in terms of results obtained through testing of modules, and the implications of these findings are assessed in terms of techno-economic projections and market potential. The techno-economic projections are based on continuation of an evolutionary technological development program and are related to the accomplishments of the program as of mid-1984. The accomplishments of the development effort are summarized for each major subsystem including concentrators, receivers, and engines. The ramifications of these accomplishments are assessed in the context of developmental objectives and strategies.

Penda, P. L.; Fujita, T.; Lucas, J. W.

1985-01-01

86

Utility-Scale Parabolic Trough Solar Systems: Performance Acceptance Test Guidelines, April 2009 - December 2010  

SciTech Connect

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.

Kearney, D.

2011-05-01

87

Solar Energy in China.  

National Technical Information Service (NTIS)

The report presents the progress, status and goals of the Chinese national solar energy programmes since 1970's. It applies specially to solar water heating, solar drying, passive solar, solar cookers, and solar photovoltaics. In China, an expertiseteam h...

H. Wennerholm

1993-01-01

88

Parabolic trough technology and economics  

SciTech Connect

The parabolic trough stands out as the most effective solar collector for medium and high temperature applications. Thermal losses are small. Parabolic troughs track the sun, preferably from a north-south axis orientation. Heat is extracted by heat transfer fluid, then brought to a closed loop steam generator. Parabolic trough system schematics for solar process steam, process drying, process hot water, and solar heating and cooling are shown. A map indicates the variation of available output for parabolic troughs throughout the US.

Hutchison, G.

1983-06-01

89

Development of Performance Acceptance Test Guidelines for Large Commercial Parabolic Trough Solar Fields: Preprint  

SciTech Connect

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.

Kearney, D.; Mehos, M.

2010-12-01

90

Vanguard I solar parabolic dish-Stirling engine module. Final report, May 28, 1982-September 30, 1984  

SciTech Connect

Advanco Corporation and the US Department of Energy entered into a cooperative agreement in May 1982 for the design, manufacture, and test of a 25-kWe solar parabolic dish module utilizing a Stirling engine power conversion unit. The product of the cooperative agreement is the Vanguard solar parabolic dish-Stirling engine module. It was designed, fabricated, and shop assembled in Los Angeles, California, and Malmoe, Sweden, and was then installed and tested at Rancho Mirage, California, in accordance with the agreement's specifications. The design features simple fabrication and assembly techniques, low cost, and high operating efficiency. The cover displays the Vanguard module operating on-sun. The concept combines the United Stirling AB (USAB) 4-95 Solar II Stirling engine, the Jet Propulsion Laboratory (JPL) developed mirror facets, the Rockwell/Advanco exocentric gimbal mechanism (EGM), the advanced USAB receiver, and a dry, integrated heat rejection system.

Washom, B.J.

1984-09-30

91

An Optical Characterization Technique for Parabolic Trough Solar Collectors Using Images of the Absorber Reflection  

NASA Astrophysics Data System (ADS)

As the concentrating solar power industry competes to develop a less-expensive parabolic trough collector, assurance is needed that new parabolic trough collectors maintain accurate optical alignment. Previous optical characterization techniques are either too slow, ill-suited for field testing, or do not allow the collector to be tested in realistic orientations. The Observer method presented here enables the rapid optical characterization of parabolic trough collectors in any orientation in the field. The Observer method directly measures the combined optical angular errors in the reflector surface shape and the absorber position, which can be separated into its two components: reflector surface slope and absorber misalignment. The data acquisition requires the placement of photogrammetry targets on and around the collector. Multiple photographs of the absorber and its reflection are taken with a digital camera from different angles with respect to the collector. The images are processed to determine the camera location of each image using photogrammetry bundle analysis. The absorber and its reflection are found in the photographs using image-processing techniques. A Monte Carlo uncertainty model was developed to determine the uncertainty in the Observer measurements. The uncertainty was estimated for a wide array of measurement test scenarios to demonstrate the user's control over the measurement uncertainty. To validate the Observer method, the absorber alignment technique was compared to traditional photogrammetry; the absorber position measured with the two methods compared with a root-mean-square difference of 1.5 mm in the transverse direction and 0.86 mm along the optical axis. The reflector surface slope error measurement was compared to both VSHOT and SOFAST, two well-established optical characterization tools, by measuring a single reflector panel in the laboratory. The VSHOT and SOFAST measurements agreed with the Observer with a root-mean-square difference of 1.6 mrad and 2.1 mrad, respectively. In the field, the Observer method's capability to test collectors in any orientation was demonstrated by mounting the camera on a radio-controlled helicopter and measuring a collector oriented at 90° above the horizon. The absorber measurement capability was demonstrated in the field for a collector facing both horizontally and vertically.

Owkes, Jeanmarie Kathleen

92

Charcoal-methanol adsorption refrigerator powered by a compound parabolic concentrating solar collector  

SciTech Connect

A compound parabolic concentrating solar collector (CPC) of concentration ratio 3.9 and aperture area 2.0 m[sup 2] was used to power an intermittent solid adsorption refrigerator and ice maker using activated charcoal (carbon) as the adsorbing medium and methanol as the working fluid. The copper tube receiver of the CPC was packed with 2.5 kg of imported adsorbent 207E3, which was only utilized when the performance of activated charcoal (ACJ1, produced from local coconut shells) was found to be inferior to the imported adsorbent. Up to 1 kg of ice at an evaporator temperature of [minus]6[degrees]C was produced, with the net solar coefficient of performance (COP) being of the order of 0.02. Maximum receiver/adsorbent temperature recorded was 154[degrees]C on a day when the insolation was 26.8 MJ/m[sup [minus]2]. Temperatures in excess of 150[degrees]C are undesirable since they favour the conversion of methanol to dimethyl ether, a noncondensable gas which inhibits both condensation and adsorption. The major advantage of this system is its ability to produce ice even on overcast days (insolation [approximately] 10 MJ/m[sup [minus]2]).

Headley, O.StC.; Kothdiwala, A.F.; McDoom, I.A. (Univ. of the West Indies, St. Augustine (Trinidad and Tobago))

1994-08-01

93

Conceptual design of a self-deployable, high performance parabolic concentrator for advanced solar-dynamic power systems  

Microsoft Academic Search

NASA has initiated technology development programs to develop advanced solar dynamic power systems and components for space applications beyond 2000. Conceptual design work that was performed is described. The main efforts were the: (1) conceptual design of self-deploying, high-performance parabolic concentrator; and (2) materials selection for a lightweight, shape-stable concentrator. The deployment concept utilizes rigid gore-shaped reflective panels. The assembled

Hans J. Dehne

1991-01-01

94

Solar reforming of methane in a direct absorption catalytic reactor on a parabolic dish: I-test and analysis  

SciTech Connect

The concept of solar driven chemical reaction in a commercial-scale volumetric receiver/reactor on a parabolic concentrator was successfully demonstrated in the CAtalytically Enhanced Solar Absorption Receiver (CAESAR) test. Solar reforming of methane (CH[sub 4]) with carbon dioxide (CO[sub 2]) was achieved in a 64 cm diameter direct absorption reactor on a parabolic dish capable of 150 kW solar power. The reactor was a catalytic volumetric absorber consisting of a multilayered, porous alumina foam disk coated with rhodium (Rh) catalyst. The system was operated during both steady-state and solar transient (cloud passage) conditions. The total solar power absorbed reached values up to 97 kW and the maximum methane conversion was 70%. Receiver thermal efficiencies ranged up to 85% and chemical efficiencies peaked at 54%. The absorber performed satisfactorily in promoting the reforming reaction during the tests without carbon formation. However, problems of cracking and degradation of the porous matrix, nonuniform dispersion of the Rh through the absorber, the catalyst deactivation due to sintering and possible encapsulation, must be resolved to achieve long-term operation and eventual commercialization.

Muir, J.F.; Hogan, R.E. Jr.; Skocypec, R.D. (Sandia National Lab., Albuquerque, NM (United States)); Buck, R. (DLR-ITT, Stuttgart (Germany))

1994-06-01

95

Software used with the flux mapper at the solar parabolic dish test site  

NASA Technical Reports Server (NTRS)

Software for data archiving and data display was developed for use on a Digital Equipment Corporation (DEC) PDP-11/34A minicomputer for use with the JPL-designed flux mapper. The flux mapper is a two-dimensional, high radiant energy scanning device designed to measure radiant flux energies expected at the focal point of solar parabolic dish concentrators. Interfacing to the DEC equipment was accomplished by standard RS-232C serial lines. The design of the software was dicated by design constraints of the flux-mapper controller. Early attemps at data acquisition from the flux-mapper controller were not without difficulty. Time and personnel limitations result in an alternative method of data recording at the test site with subsequent analysis accomplished at a data evaluation location at some later time. Software for plotting was also written to better visualize the flux patterns. Recommendations for future alternative development are discussed. A listing of the programs used in the anaysis is included in an appendix.

Miyazono, C.

1984-01-01

96

Software used with the flux mapper at the solar parabolic dish test site  

NASA Astrophysics Data System (ADS)

Software for data archiving and data display was developed for use on a Digital Equipment Corporation (DEC) PDP-11/34A minicomputer for use with the JPL-designed flux mapper. The flux mapper is a two-dimensional, high radiant energy scanning device designed to measure radiant flux energies expected at the focal point of solar parabolic dish concentrators. Interfacing to the DEC equipment was accomplished by standard RS-232C serial lines. The design of the software was dicated by design constraints of the flux-mapper controller. Early attemps at data acquisition from the flux-mapper controller were not without difficulty. Time and personnel limitations result in an alternative method of data recording at the test site with subsequent analysis accomplished at a data evaluation location at some later time. Software for plotting was also written to better visualize the flux patterns. Recommendations for future alternative development are discussed. A listing of the programs used in the anaysis is included in an appendix.

Miyazono, C.

1984-09-01

97

Secondary and compound concentrators for parabolic dish solar thermal power systems  

NASA Technical Reports Server (NTRS)

A secondary optical element may be added to a parabolic dish solar concentrator to increase the geometric concentration ratio attainable at a given intercept factor. This secondary may be a Fresnel lens or a mirror, such as a compound elliptic concentrator or a hyperbolic trumpet. At a fixed intercept factor, higher overall geometric concentration may be obtainable with a long focal length primary and a suitable secondary matched to it. Use of a secondary to increase the geometric concentration ratio is more likely to e worthwhile if the receiver temperature is high and if errors in the primary are large. Folding the optical path with a secondary may reduce cost by locating the receiver and power conversion equipment closer to the ground and by eliminating the heavy structure needed to support this equipment at the primary focus. Promising folded-path configurations include the Ritchey-Chretien and perhaps some three element geometries. Folding the optical path may be most useful in systems that provide process heat.

Jaffe, L. D.; Poon, P. T.

1981-01-01

98

Secondary and compound concentrators for parabolic-dish solar-thermal power systems  

SciTech Connect

A secondary optical element may be added to a parabolic dish solar concentrator to increase the geometric concentration ratio attainable at a given intercept factor. This secondary may be a Fresnel lens or a mirror, such as a compound elliptic concentrator or a hyperbolic trumpet. At a fixed intercept factor, higher overall geometric concentration may be obtainable with a long focal length primary and a suitable secondary matched to it. Use of a secondary to increase the geometric concentration ratio is more likely to be worthwhile if the receiver temperature is high and if errors in the primary are large. Folding the optical path with a secondary may reduce cost by locating the receiver and power conversion equipment closer to the ground and by eliminating the heavy structure needed to support this equipment at the primary focus. Promising folded-path configurations include the Ritchey-Chretien and perhaps some three-element geometries. Folding the optical path may be most useful in systems that provide process heat.

Jaffe, L.D.; Poon, P.T.

1981-04-15

99

Effect of porous disc receiver configurations on performance of solar parabolic trough concentrator  

NASA Astrophysics Data System (ADS)

In this article, heat transfer enhancement of line focus solar collector with porous disc receiver is studied with water and therminol oil. A three dimensional (3-D) numerical simulation of porous disc enhanced receiver is carried out using commercial CFD software Fluent 6.3 to evolve the optimum configuration. The 3-D numerical model is solved by renormalization-group based k-? turbulent model associated with standard wall function. The effect of porous disc receiver configurations (solid disc at bottom; porous disc at bottom; porous disc at top; and alternative porous disc) on performance of the trough concentrator is investigated. The effect of porous disc geometric parameters (?, ?, W, H and t) and fluid parameters (Pr and m) on heat transfer enhancement of the receiver is also studied. The numerical simulation results show that the flow pattern around the solid and porous discs are entirely different and it significantly influences the local heat transfer coefficient. The porous disc receiver experiences low pressure drop as compared to that of solid disc receiver due to less obstruction. The optimum configuration of porous disc receiver enhances the heat transfer rate of 221 W m-1 and 13.5% with pumping penalty of 0.014 W m-1 for water and for therminol oil-55, heat transfer rate enhances of 575 W m-1 and 31.4% with pumping penalty of 0.074 W m-1 as compared to that of tubular receiver at the mass flow rate of 0.5 kg s-1. The Nusselt number and friction factor correlations are proposed for porous disc receiver to calculate heat transfer characteristics. The porous disc receiver can be used to increase the performance of solar parabolic trough concentrator.

Ravi Kumar, K.; Reddy, K. S.

2012-03-01

100

Conceptual design of a self-deployable, high performance parabolic concentrator for advanced solar-dynamic power systems  

NASA Technical Reports Server (NTRS)

A summary is presented of the concentrator conceptual design work performed under a NASA-funded project. The design study centers around two basic efforts: conceptual design of a self-deploying, high-performance parabolic concentrator; and materials selection for a lightweight, shape-stable concentrator. The primary structural material selected for the concentrator is PEEK/carbon fiber composite. The deployment concept utilizes rigid gore-shaped reflective panels. The assembled concentrator takes a circular shape with a void in the center. The deployable solar concentrator concept is applicable to a range of solar dynamic power systems of 25 kWe to more than 75 kWe.

Dehne, Hans Joachim; Duffy, Donald R.

1989-01-01

101

Development of Molten-Salt Heat Transfer Fluid Technology for Parabolic Trough Solar Power Plants - Public Final Technical Report  

SciTech Connect

Executive Summary This Final Report for the "Development of Molten-Salt Heat Transfer Fluid (HTF) Technology for Parabolic Trough Solar Power Plants” describes the overall project accomplishments, results and conclusions. Phase 1 analyzed the feasibility, cost and performance of a parabolic trough solar power plant with a molten salt heat transfer fluid (HTF); researched and/or developed feasible component options, detailed cost estimates and workable operating procedures; and developed hourly performance models. As a result, a molten salt plant with 6 hours of storage was shown to reduce Thermal Energy Storage (TES) cost by 43.2%, solar field cost by 14.8%, and levelized cost of energy (LCOE) by 9.8% - 14.5% relative to a similar state-of-the-art baseline plant. The LCOE savings range met the project’s Go/No Go criteria of 10% LCOE reduction. Another primary focus of Phase 1 and 2 was risk mitigation. The large risk areas associated with a molten salt parabolic trough plant were addressed in both Phases, such as; HTF freeze prevention and recovery, collector components and piping connections, and complex component interactions. Phase 2 analyzed in more detail the technical and economic feasibility of a 140 MWe,gross molten-salt CSP plant with 6 hours of TES. Phase 2 accomplishments included developing technical solutions to the above mentioned risk areas, such as freeze protection/recovery, corrosion effects of applicable molten salts, collector design improvements for molten salt, and developing plant operating strategies for maximized plant performance and freeze risk mitigation. Phase 2 accomplishments also included developing and thoroughly analyzing a molten salt, Parabolic Trough power plant performance model, in order to achieve the project cost and performance targets. The plant performance model and an extensive basic Engineering, Procurement, and Construction (EPC) quote were used to calculate a real levelized cost of energy (LCOE) of 11.50¢/kWhe , which achieved the Phase 2 Go/No Go target of less than 0.12¢/kWhe. Abengoa Solar has high confidence that the primary risk areas have been addressed in the project and a commercial plant utilizing molten salt is economically and technically feasible. The strong results from the Phase 1 and 2 research, testing, and analyses, summarized in this report, led Abengoa Solar to recommend that the project proceed to Phase 3. However, a commercially viable collector interconnection was not fully validated by the end of Phase 2, combined with the uncertainty in the federal budget, forced the DOE and Abengoa Solar to close the project. Thus the resources required to construct and operate a molten salt pilot plant will be solely supplied by Abengoa Solar.

Grogan, Dylan C. P.

2013-08-15

102

1-10 kWe solar power plant with modular cylindrical-parabolic concentrators of 100 sq m, oriented EW  

Microsoft Academic Search

A number of investigations have been conducted regarding the feasibility to design a solar power plant which employs cylindrical-parabolic concentrators. The subjects studied in the investigations are briefly considered and a description is presented of the current stage of development of such a plant. Attention is given to the solutions selected for the solar power plant to be implemented, taking

S. Petrescu; A. Danescu; S. Bucurenciu

1980-01-01

103

Nexant Parabolic Trough Solar Power Plant Systems Analysis. Task 1: Preferred Plant Size. Report for January 20, 2005 to December 31, 2005.  

National Technical Information Service (NTIS)

The Rankine cycles for commercial parabolic trough solar projects range in capacity from 13.5 MWe at the Solar Electric Generating Station I (SEGS I) plant, to a maximum of 89 MWe at the SEGS VIII / IX plants. The series of SEGS projects showed a consiste...

B. Kelly

2006-01-01

104

Solar food processor  

Microsoft Academic Search

Cooking is one of the unavoidable activities that consumes huge amount of conventional fuel. If this state continues then all the fuel left will get depleted in about 20-30 years. This problem was identified many years ago and solar cookers were introduced. In different parts of the world solar cookers are made, studied and patented but it is not being

R. B. Nisha; S. Madhumitha

2010-01-01

105

Micro-structured reflector surfaces for a stationary asymmetric parabolic solar concentrator  

Microsoft Academic Search

One of the main problems in using parabolic concentrators with standard photovoltaics (PV) cells is the highly non-uniform illumination of the cells. The non-uniform irradiation causes high resistive losses in the standard cells due to their relatively high series resistance. This results in a considerably lowered efficiency. To solve the problem, we introduce three different structured reflectors that will create

Johan Nilsson; Ralf Leutz; Björn Karlsson

2007-01-01

106

Modelling, optimisation and performance evaluation of a parabolic trough solar collector steam generation system  

Microsoft Academic Search

A parabolic trough collector (PTC) system used for steam generation is presented in this paper. PTCs are the preferred type of collectors used for steam generation due to their ability to work at high temperatures with a good efficiency. The modelling program developed called PTCDES is used to predict the quantity of steam produced by the system. The flash vessel

Soteris Kalogirou; Stephen Lloyd; John Ward

1997-01-01

107

Solar energy  

Microsoft Academic Search

Water pumps, solar power stations, air conditioners, fresh-water stills, solar homes, solar cookers, fruit driers, devices for (low temperature) steaming of reinforced concrete members, solar refrigerators, solar hothouses, welding and melting of metals presents a far from complete list of the devices and areas of the possible broad use of solar energy. The first plant of solar equipment is to

G. Y. Umarov; A. A. Yershov

1975-01-01

108

Dielectric compound parabolic concentrating solar collector with a frustrated total internal reflection absorber.  

PubMed

Coupling a dielectric compound parabolic concentrator (DCPC) to an absorber across a vacuum gap by means of frustrated total internal reflection (FTIR) can theoretically approach the maximum concentration permitted by physical laws, thus allowing higher radiative fluxes in thermal applications. The calculated optical performance of 2-D DCPCs with FTIR absorbers indicates that the ratio of gap thickness to optical wavelength must be <0.22 before the optical performance of the DCPC is superior to that of the nondielectric CPC. PMID:20548443

Hull, J R

1989-01-01

109

Performance evaluation and simulation of a Compound Parabolic Concentrator (CPC) trough Solar Thermal Power Plant in Puerto Rico under solar transient conditions  

NASA Astrophysics Data System (ADS)

The increasing fossil fuel costs as well as the need to move in a somewhat sustainable future has led the world in a quest for exploiting the free and naturally available energy from the Sun to produce electric power, and Puerto Rico is no exception. This thesis proposes the design of a simulation model for the analysis and performance evaluation of a Solar Thermal Power Plant in Puerto Rico and suggests the use of the Compound Parabolic Concentrator as the solar collector of choice. Optical and thermal analysis of such collectors will be made using local solar radiation data for determining the viability of this proposed project in terms of the electric power produced and its cost.

Feliciano-Cruz, Luisa I.

110

Design, construction and study of a hybrid solar food processor in the climate of Costa Rica  

Microsoft Academic Search

During the last 25 years, the author has designed, constructed, studied and promoted solar oven, hybrid solar\\/electric oven, solar oven cum drier, solar cooker cum water heater and solar still. In different parts of the world, solar cookers have been made, studied, patented, however, their real uses are very limited due to many reasons—unstable climate, economic, cultural, social and single

Shyam S. Nandwani

2007-01-01

111

Conceptual design of a parabolic dish solar collector using simulation techniques  

NASA Technical Reports Server (NTRS)

The development of solar concentrators in recent years have produced a wide variety of collectors for the utilization of solar energy. This paper presents the simulation techniques used to predict the optical and thermal performance of a paraboloid of revolution type solar collector. Conceptual design of a dish concentrator with a fixed receiver size is obtained by parametrically examining the significant variables.

Gupta, B. P.; Buchholz, R. L.

1976-01-01

112

Feasibility Study on the Use of a Solar Thermoelectric Cogenerator Comprising a Thermoelectric Module and Evacuated Tubular Collector with Parabolic Trough Concentrator  

NASA Astrophysics Data System (ADS)

We have designed a new solar thermoelectric cogeneration system consisting of an evacuated tubular solar collector (ETSC) with a parabolic trough concentrator (PTC) and thermoelectric modules (TEMs) to supply both thermal energy and electricity. The main design concepts are (1) the hot side of the TEM is bonded to the solar selective absorber installed in an evacuated glass tube, (2) the cold side of the TEM is also bonded to the heat sink, and (3) the outer circulated water is heated by residual solar energy after TEM generation. We present an example solar thermal simulation based on energy balance and heat transfer as used in solar engineering to predict the electrical conversion efficiency and solar thermal conversion efficiency for different values of parameters such as the solar insolation, concentration ratio, and TEM ZT values.

Miao, L.; Zhang, M.; Tanemura, S.; Tanaka, T.; Kang, Y. P.; Xu, G.

2012-06-01

113

International Experience in Standards and Labeling Programs for Rice Cookers  

Microsoft Academic Search

China has had an active program on energy efficiency standards for household appliances since the mid-1990s. Rice cooker is among the first to be subject to such mandatory regulation, since it is one of the most prevalent electric appliances in Chinese households. Since first introduced in 1989, the minimum energy efficiency standard for rice cookers has not been revised. Therefore,

Nan Zhou; Nina Zheng

2008-01-01

114

Conceptual design of a self-deployable, high performance parabolic concentrator for advanced solar-dynamic power systems  

NASA Technical Reports Server (NTRS)

NASA has initiated technology development programs to develop advanced solar dynamic power systems and components for space applications beyond 2000. Conceptual design work that was performed is described. The main efforts were the: (1) conceptual design of self-deploying, high-performance parabolic concentrator; and (2) materials selection for a lightweight, shape-stable concentrator. The deployment concept utilizes rigid gore-shaped reflective panels. The assembled concentrator takes an annular shape with a void in the center. This deployable concentrator concept is applicable to a range of solar dynamic power systems of 25 kW sub e to in excess of 75 kW sub e. The concept allows for a family of power system sizes all using the same packaging and deployment technique. The primary structural material selected for the concentrator is a polyethyl ethylketone/carbon fiber composite also referred to as APC-2 or Vitrex. This composite has a nearly neutral coefficient of thermal expansion which leads to shape stable characteristics under thermal gradient conditions. Substantial efforts were undertaken to produce a highly specular surface on the composite. The overall coefficient of thermal expansion of the composite laminate is near zero, but thermally induced stresses due to micro-movement of the fibers and matrix in relation to each other cause the surface to become nonspecular.

Dehne, Hans J.

1991-01-01

115

Commercialization of parabolic dish systems  

NASA Astrophysics Data System (ADS)

The impact of recent federal tax and regulatory legislation on the commercialization of parabolic solar reflector technology is assessed. Specific areas in need of technical or economic improvement are noted.

Washom, B.

1982-07-01

116

Commercialization of parabolic dish systems  

NASA Technical Reports Server (NTRS)

The impact of recent federal tax and regulatory legislation on the commercialization of parabolic solar reflector technology is assessed. Specific areas in need of technical or economic improvement are noted.

Washom, B.

1982-01-01

117

Preliminary study on optimization of pH, oxidant and catalyst dose for high COD content: solar parabolic trough collector.  

PubMed

In the present study, solar photocatalytic oxidation has been investigated through laboratory experiments as an alternative to conventional secondary treatment for the organic content reduction of high COD wastewater. Experiments have been performed on synthetic high COD wastewater for solar photocatalytic oxidation using a parabolic trough reactor. Parameters affecting the oxidation of organics have been investigated.The experimental design followed the sequence of dark adsorption studies of organics, followed by photolytic studies (in absence of catalyst) and finally photocatalytic studies in presence and absence of additional oxidant (H2O2). All the experimental studies have been performed at pH values of 2, 4, 6,8,10 and the initial pH value of the wastewater (normal pH). For photocatalytic studies, TiO2 has been used as a photocatalyst. Optimization of catalyst dose, pH and H2O2 concentration has been done. Maximum reduction of organic content was observed at the normal pH value of the wastewater (pH?=?6.8). The reaction rate was significantly enhanced in presence of hydrogen peroxide. The optimum pH other than the Normal was in the alkaline range. Acidic pH was not found to be favourable for organic content reduction. pH was found to be a dominant factor affecting reaction rate even in presence of H2O2 as an additional oxidant. Also, the solar detoxification process was effective in treating a waste with a COD level of more than 7500 mg/L, which is a otherwise a difficult waste to treat. It can therefore be used as a treatment step in the high organic wastewater treatment during the primary stage also as it effectively reduces the COD content by 86%. PMID:23369352

Singh, Chandan; Chaudhary, Rubina; Gandhi, Kavita

2013-01-01

118

Conceptual design of a self-deployable, high performance parabolic concentrator for advanced solar-dynamic power systems. Final Technical Report  

Microsoft Academic Search

NASA has initiated technology development programs to develop advanced solar dynamic power systems and components for space applications beyond 2000. Conceptual design work that was performed is described. The main efforts were the: (1) conceptual design of self-deploying, high-performance parabolic concentrator; and (2) materials selection for a lightweight, shape-stable concentrator. The deployment concept utilizes rigid gore-shaped reflective panels. The assembled

Dehne

1991-01-01

119

Acceptance Performance Test Guideline for Utility Scale Parabolic Trough and Other CSP Solar Thermal Systems: Preprint  

SciTech Connect

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. Progress on interim guidelines was presented at SolarPACES 2010. Significant additions and modifications were made to the guidelines since that time, resulting in a final report published by NREL in April 2011. This paper summarizes those changes, which emphasize criteria for assuring thermal equilibrium and steady state conditions within the solar field.

Mehos, M. S.; Wagner, M. J.; Kearney, D. W.

2011-08-01

120

Nexant Parabolic Trough Solar Power Plant Systems Analysis; Task 1: Preferred Plant Size, 20 January 2005 - 31 December 2005  

SciTech Connect

The Rankine cycles for commercial parabolic trough solar projects range in capacity from 13.5 MWe at the Solar Electric Generating Station I (SEGS I) plant, to a maximum of 89 MWe at the SEGS VIII/IX plants. The series of SEGS projects showed a consistent reduction in the levelized energy cost due to a combination of improvements in collector field technology and economies of scale in both the Rankine cycle and the operation and maintenance costs. Nonetheless, the question of the optimum Rankine cycle capacity remains an open issue. The capacities of the SEGS VIII/IX plants were limited by Federal Energy Regulatory Commission and Public Utility Regulatory Policy Act requirements to a maximum net output of 80 MWe. Further improvements in the Rankine cycle efficiency, and economies of scale in both the capital and the operating cost, should be available at larger plant sizes. An analysis was conducted to determine the effect of Rankine cycle capacities greater than 80 MWe on the levelized energy cost. The study was conducted through the following steps: (1) Three gross cycle capacities of 88 MWe, 165 MWe, and 220 MWe were selected. (2) Three Rankine cycle models were developed using the GateCycle program. The models were based on single reheat turbine cycles, with main steam conditions of 1,450 lb{sub f}/in{sup 2} and 703 F, and reheat steam conditions of 239 lb{sub f}/in{sup 2} and 703 F. The feedwater heater system consisted of 5 closed heaters and 1 open deaerating heater. The design condenser pressure was 2.5 in. HgA. (3) The optimization function within Excelergy was used to determine the preferred solar multiple for each plant. Two cases were considered for each plant: (a) a solar-only project without thermal storage, and (b) a solar-fossil hybrid project, with 3 hours of thermal storage and a heat transport fluid heater fired by natural gas. (4) For each of the 6 cases, collector field geometries, heat transport fluid pressure losses, and heat transport pump power requirements were calculated with a field piping optimization model. (5) Annual electric energy outputs, capital costs, and annual operating costs were calculated for each case using the default methods within Excelergy, from which estimates of the levelized energy costs were developed. The plant with the lowest energy cost was considered the optimum.

Kelly, B.

2006-07-01

121

Evaluation of the solar water disinfection process (SODIS) against Cryptosporidium parvum using a 25-L static solar reactor fitted with a compound parabolic collector (CPC).  

PubMed

Water samples of 0, 5, and 30 nephelometric turbidity units (NTU) spiked with Cryptosporidium parvum oocysts were exposed to natural sunlight using a 25-L static solar reactor fitted with a compound parabolic collector (CPC). The global oocyst viability was calculated by the evaluation of the inclusion/exclusion of the fluorogenic vital dye propidium iodide and the spontaneous excystation. After an exposure time of 8 hours, the global oocyst viabilities were 21.8 ± 3.1%, 31.3 ± 12.9%, and 45.0 ± 10.0% for turbidity levels of 0, 5, and 30 NTU, respectively, and these values were significantly lower (P < 0.05) that the initial global viability of the isolate (92.1 ± 0.9%). The 25-L static solar reactor that was evaluated can be an alternative system to the conventional solar water disinfection process for improving the microbiological quality of drinking water on a household level, and moreover, it enables treatment of larger volumes of water (> 10 times). PMID:22302852

Fontán-Sainz, María; Gómez-Couso, Hipólito; Fernández-Ibáñez, Pilar; Ares-Mazás, Elvira

2012-02-01

122

Life Cycle Assessment of a Parabolic Trough Concentrating Solar Power Plant and Impacts of Key Design Alternatives: Preprint  

SciTech Connect

Climate change and water scarcity are important issues for today's power sector. To inform capacity expansion decisions, hybrid life cycle assessment is used to evaluate a reference design of a parabolic trough concentrating solar power (CSP) facility located in Daggett, California, along four sustainability metrics: life cycle greenhouse gas (GHG) emissions, water consumption, cumulative energy demand (CED), and energy payback time (EPBT). This wet-cooled, 103 MW plant utilizes mined nitrate salts in its two-tank, thermal energy storage (TES) system. Design alternatives of dry-cooling, a thermocline TES, and synthetically-derived nitrate salt are evaluated. During its life cycle, the reference CSP plant is estimated to emit 26 g CO2eq per kWh, consume 4.7 L/kWh of water, and demand 0.40 MJeq/kWh of energy, resulting in an EPBT of approximately 1 year. The dry-cooled alternative is estimated to reduce life cycle water consumption by 77% but increase life cycle GHG emissions and CED by 8%. Synthetic nitrate salts may increase life cycle GHG emissions by 52% compared to mined. Switching from two-tank to thermocline TES configuration reduces life cycle GHG emissions, most significantly for plants using synthetically-derived nitrate salts. CSP can significantly reduce GHG emissions compared to fossil-fueled generation; however, dry-cooling may be required in many locations to minimize water consumption.

Heath, G. A.; Burkhardt, J. J.; Turchi, C. S.

2011-09-01

123

Life cycle assessment of a parabolic trough concentrating solar power plant and the impacts of key design alternatives.  

PubMed

Climate change and water scarcity are important issues for today's power sector. To inform capacity expansion decisions, hybrid life cycle assessment is used to evaluate a reference design of a parabolic trough concentrating solar power (CSP) facility located in Daggett, CA, along four sustainability metrics: life cycle (LC) greenhouse gas (GHG) emissions, water consumption, cumulative energy demand (CED), and energy payback time (EPBT). This wet-cooled, 103 MW plant utilizes mined nitrates salts in its two-tank, thermal energy storage (TES) system. Design alternatives of dry-cooling, a thermocline TES, and synthetically derived nitrate salt are evaluated. During its LC, the reference CSP plant is estimated to emit 26 g of CO(2eq) per kWh, consume 4.7 L/kWh of water, and demand 0.40 MJ(eq)/kWh of energy, resulting in an EPBT of approximately 1 year. The dry-cooled alternative is estimated to reduce LC water consumption by 77% but increase LC GHG emissions and CED by 8%. Synthetic nitrate salts may increase LC GHG emissions by 52% compared to mined. Switching from two-tank to thermocline TES configuration reduces LC GHG emissions, most significantly for plants using synthetically derived nitrate salts. CSP can significantly reduce GHG emissions compared to fossil-fueled generation; however, dry-cooling may be required in many locations to minimize water consumption. PMID:21391722

Burkhardt, John J; Heath, Garvin A; Turchi, Craig S

2011-03-15

124

Degradation of pharmaceutical beta-blockers by electrochemical advanced oxidation processes using a flow plant with a solar compound parabolic collector  

Microsoft Academic Search

The degradation of the beta-blockers atenolol, metoprolol tartrate and propranolol hydrochloride was studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF). Solutions of 10 L of 100 mg L?1 of total organic carbon of each drug in 0.1 M Na2SO4 with 0.5 mM Fe2+ of pH 3.0 were treated in a recirculation flow plant with an electrochemical reactor coupled with a solar compound parabolic collector. Single

Eloy Isarain-Chávez; Rosa María Rodríguez; Pere Lluís Cabot; Francesc Centellas; Conchita Arias; José Antonio Garrido; Enric Brillas

2011-01-01

125

Comparison of advanced engines for parabolic dish solar thermal power plants  

NASA Technical Reports Server (NTRS)

A paraboloidal dish solar thermal power plant produces electrical energy by a two-step conversion process. The collector subsystem is composed of a two-axis tracking paraboloidal concentrator and a cavity receiver. The concentrator focuses intercepted sunlight (direct, normal insolation) into a cavity receiver whose aperture encircles the focal point of the concentrator. At the internal wall of the receiver the electromagnetic radiation is converted to thermal energy. A heat engine/generator assembly then converts the thermal energy captured by the receiver to electricity. Developmental activity has been concentrated on small power modules which employ 11- to 12-meter diameter dishes to generate nominal power levels of approximately 20 kWe. A comparison of advanced heat engines for the dish power module is presented in terms of the performance potential of each engine with its requirements for advanced technology development. Three advanced engine possibilities are the Brayton (gas turbine), Brayton/Rankine combined cycle, and Stirling engines.

Fujita, T.; Bowyer, J. M.; Gajanana, B. C.

1980-01-01

126

Ground-mounted thermal storage for the parabolic dish solar collector/Stirling engine system  

NASA Astrophysics Data System (ADS)

Several types of pumped-fluid thermal energy transport and phase-change thermal storage systems are examined. The pumped fluid circulates through a symmetrically arranged group of collectors within a large collector field and transports thermal energy to the engine/thermal storage subsystem near the center of the connected cluster. Cost analyses are made on the basis of variations in the designs of the major components. Pressurized liquid transport fluids and saturated liquids that boil in the solar receiver to return as vapors are investigated. A number of liquid metals are considered for each type of thermal energy transport. Conventional insulation and vacuum-jacketed multilayer foil type insulation designs are assessed. Also investigated are tube-intensive and direct-contact type heat exchangers.

Copeland, R. J.; Ullman, J.; Leach, J. W.

127

Wind effects on convective heat loss from a cavity receiver for a parabolic concentrating solar collector  

SciTech Connect

Tests were performed to determine the convective heat loss characteristics of a cavity receiver for a parabolid dish concentrating solar collector for various tilt angles and wind speeds of 0-24 mph. Natural (no wind) convective heat loss from the receiver is the highest for a horizontal receiver orientation and negligible with the reveler facing straight down. Convection from the receiver is substantially increased by the presence of side-on wind for all receiver tilt angles. For head-on wind, convective heat loss with the receiver facing straight down is approximately the same as that for side-on wind. Overall it was found that for wind speeds of 20--24 mph, convective heat loss from the receiver can be as much as three times that occurring without wind.

Ma, R.Y. [California State Polytechnic Univ., Pomoma, CA (United States). Dept. of Mechanical Engineering

1993-09-01

128

Solar energy in China  

Microsoft Academic Search

The report presents the progress, status and goals of the Chinese national solar energy programs since 1970's. It applies specially to solar water heating, solar drying, passive solar, solar cookers, and solar photovoltaics. In China, an expert team has been organized, a number of technology development centers for new and renewable sources of energy have been set up and some

H. Wennerholm

1993-01-01

129

A modified concentrating type solar oven for outdoor cooking  

Microsoft Academic Search

Solar cookers offer a partial solution to many problems for the poor developing areas of the world. In these regions energy used for cooking sometimes comprises four fifths of the total energy demand. Solar cookers are generally four catagories: direct focusing, oven, ovenfocusing and indirect types. The direct focusing types failed to boil water under windy conditions due to excessive

Khalifa

1983-01-01

130

DIFFUSION OF INNOVATION: SOLAR OVEN USE IN LESOTHO (AFRICA)  

Microsoft Academic Search

This paper uses a previously published report coupled with recently collected empirical information on the diffusion of solar cookers among the Basotho of Lesotho. Drawing upon diffusion practice and theory, the authors cite several present-day in- stances where diffusion is taking place. The conclusion, however, is unfortunate, in that the outlook for the use of solar cookers and their effective

Roy R. Grund; William N. Grund

131

Solar energy research and applications in China  

Microsoft Academic Search

Solar collectors and silicon solar cells are being used by a dozen or so provinces and municipalities in China, in barbershops, hotels, restaurants and public bath houses, and solar radiation is being used for distillation and power generation. Vacuum-glass tube solar collectors, solar air driers, solar cookers, solar houses, solar welding devices and solar thermal power installations are some of

L. Wei de

1980-01-01

132

Manufacturing cost analysis of a parabolic dish concentrator (General Electric design) for solar thermal electric power systems in selected production volumes  

NASA Technical Reports Server (NTRS)

The manufacturing cost of a General Electric 12 meter diameter concentrator was estimated. This parabolic dish concentrator for solar thermal system was costed in annual production volumes of 100 - 1,000 - 5,000 - 10,000 - 50,000 100,000 - 400,000 and 1,000,000 units. Presented for each volume are the costs of direct labor, material, burden, tooling, capital equipment and buildings. Also presented is the direct labor personnel and factory space requirements. All costs are based on early 1981 economics.

1981-01-01

133

Solar Oven  

NSDL National Science Digital Library

In many rural parts of the world, people still cook with wood. They often must collect and carry the wood many miles on their backs. They also cut down trees and shrubs instead of letting them grow tall for shade. There is lots of sunshine in these areas, especially if the climate is dry, so a solar cooker would be very useful! Most solar cookers are ovens that convert sunlight into heat energy that is used for cooking. You will design a simple solar oven and improve the design by adding reflectors and insulation while testing heating power with a temperature sensor.

Consortium, The C.

2012-05-21

134

Parabolic dish module experiment  

NASA Astrophysics Data System (ADS)

A development test model of the 8-meter Solar Brayton Parabolic Dish Module has been designed, fabricated, and tested. The test model consists of five major subsystems: Sanders ceramic honeycomb solar receiver; LaJet LEC460 solar concentrator; AiRsearch SABC MKIIIA engine, Abacus 8 kW ac inverter; and a Sanders designed and built system controller. Goals of the tests were to integrate subsystem components into a working module, demonstrate the concept, and generate 5 kWe (hybrid) and 4.7 kWe (solar only) input. All subsystem integration goals were successfully achieved, but system performance efficiency was lower than expected. Contributing causes of the lower performance efficiencies have been identified. Modifications needed to restore performance to the required levels and improve the system life cycle cost have been addressed and are the subject of this final report.

1986-03-01

135

A Nomographic Methodology for Use in Performance Trade-Off Studies of Parabolic Dish Solar Power Modules  

NASA Technical Reports Server (NTRS)

A simple graphical method was developed to undertake technical design trade-off studies for individual parabolic dish models comprising a two-axis tracking parabolic dish with a cavity receiver and power conversion assembly at the focal point. The results of these technical studies are then used in performing the techno-economic analyses required for determining appropriate subsystem sizing. Selected graphs that characterize the performance of subsystems within the module were arranged in the form of a nomogram that would enable an investigator to carry out several design trade-off studies. Key performance parameters encompassed in the nomogram include receiver losses, intercept factor, engine rating, and engine efficiency. Design and operation parameters such as concentrator size, receiver type (open or windowed aperture), receiver aperture size, operating temperature of the receiver and engine, engine partial load characteristics, concentrator slope error, and the type of reflector surface, are also included in the graphical solution. Cost considerations are not included.

Selcuk, M. K.; Fujita, T.

1984-01-01

136

Conceptual design of a self-deployable, high performance parabolic concentrator for advanced solar-dynamic power systems  

Microsoft Academic Search

A summary is presented of the concentrator conceptual design work performed under a NASA-funded project. The design study centers around two basic efforts: conceptual design of a self-deploying, high-performance parabolic concentrator; and materials selection for a lightweight, shape-stable concentrator. The primary structural material selected for the concentrator is PEEK\\/carbon fiber composite. The deployment concept utilizes rigid gore-shaped reflective panels. The

H. J. Dehne; D. R. Duffy

1989-01-01

137

A review of test results on parabolic dish solar thermal power modules with dish-mounted Rankine engines and for production of process steam  

NASA Technical Reports Server (NTRS)

This paper presents results of development testing of various solar thermal parabolic dish modules and assemblies. Most of the tests were at modules and assemblies that used a dish-mounted, organic Rankine cycle turbine for production of electric power. Some tests were also run on equipment for production of process steam or for production of electricity using dish-mounted reciprocating steam engines. These tests indicate that early modules achieve efficiencies of about 18 percent in converting sunlight to electricity (excluding the inverter but including parasitics). A number of malfunctions occurred. The performance measurements, as well as the malfunctions and other operating experience, provided information that should be of value in developing systems with improved performance and reduced maintenance.

Jaffe, Leonard D.

1988-01-01

138

Parabolic Dish Module Experiment. Final Test Report.  

National Technical Information Service (NTIS)

A development test model of the 8-meter Solar Brayton Parabolic Dish Module has been designed, fabricated, and tested. The test model consists of five major subsystems: Sanders ceramic honeycomb solar receiver; LaJet LEC460 solar concentrator; AiRsearch S...

1986-01-01

139

Saturated steam process with direct steam generating parabolic troughs  

Microsoft Academic Search

The direct steam generation (DSG) in parabolic trough collectors is an attractive option regarding the economic improvement of parabolic trough technology for solar thermal electricity generation in the multi Megawatt range. The European DISS project has proven the feasibility of the direct steam generation under real solar conditions in more than 4000 operation hours. Within the European R&D project INDITEP

M. Eck; E. Zarza

2006-01-01

140

Degradation of pharmaceutical beta-blockers by electrochemical advanced oxidation processes using a flow plant with a solar compound parabolic collector.  

PubMed

The degradation of the beta-blockers atenolol, metoprolol tartrate and propranolol hydrochloride was studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF). Solutions of 10 L of 100 mg L?¹ of total organic carbon of each drug in 0.1 M Na?SO? with 0.5 mM Fe²? of pH 3.0 were treated in a recirculation flow plant with an electrochemical reactor coupled with a solar compound parabolic collector. Single Pt/carbon felt (CF) and boron-doped diamond (BDD)/air-diffusion electrode (ADE) cells and combined Pt/ADE-Pt/CF and BDD/ADE-Pt/CF cells were used. SPEF treatments were more potent with the latter cell, yielding 95-97% mineralization with 100% of maximum current efficiency and energy consumptions of about 0.250 kWh g TOC?¹. However, the Pt/ADE-Pt/CF cell gave much lower energy consumptions of about 0.080 kWh g TOC?¹ with slightly lower mineralization of 88-93%, then being more useful for its possible application at industrial level. The EF method led to a poorer mineralization and was more potent using the combined cells by the additional production of hydroxyl radicals (•OH) from Fenton's reaction from the fast Fe²? regeneration at the CF cathode. Organics were also more rapidly destroyed at BDD than at Pt anode. The decay kinetics of beta-blockers always followed a pseudo first-order reaction, although in SPEF, it was accelerated by the additional production of •OH from the action of UV light of solar irradiation. Aromatic intermediates were also destroyed by hydroxyl radicals. Ultimate carboxylic acids like oxalic and oxamic remained in the treated solutions by EF, but their Fe(III) complexes were photolyzed by solar irradiation in SPEF, thus explaining its higher oxidation power. NO?? was the predominant inorganic ion lost in EF, whereas the SPEF process favored the production of NH?? ion and volatile N-derivatives. PMID:21693380

Isarain-Chávez, Eloy; Rodríguez, Rosa María; Cabot, Pere Lluís; Centellas, Francesc; Arias, Conchita; Garrido, José Antonio; Brillas, Enric

2011-08-01

141

Solar reforming of methane in a direct absorption catalytic reactor on a parabolic dish: II-modeling and analysis  

SciTech Connect

The CAtalytically Enhanced Solar Absorption Receiver (CAESAR) test was conducted to determine the thermal, chemical, and mechanical performance of a commercial-scale, dish-mounted, direct catalytic absorption receiver (DCAR) reactor over a range of steady state and transient (cloud) operating conditions. The focus of the test was to demonstrate [open quotes]proof-of-concept[close quotes] and determine global performance such as reactor efficiencies and overall methane conversion. A numerical model was previously developed to provide guidance in the design of the absorber. The one-dimensional, planar, and steady-state model incorporates the following energy transfer mechanisms: solar and infrared radiation, heterogeneous chemical reaction, conduction in the solid phase, and convection between the fluid and solid phases. Improvements to the model and improved property values are presented here. In particular, the solar radiative transfer model is improved by using a three-flux technique to more accurately represent the typically conical incident flux. A spatially varying catalyst loading is incorporated, convective and radiative properties for each layer in the multilayer absorber are determined, and more realistic boundary conditions are applied. Considering that this test was not intended to provide data for code validation, model predictions are shown to generally bound the test axial thermocouple data when test uncertainties are included. Global predictions are made using a technique in which the incident solar flux distribution is subdivided into flux contour bands. Reactor predictions for anticipated operating conditions suggest that a further decrease in optical density (i.e., extinction coefficient) at the front of the absorber inner disk may improve absorber conditions. Code-validation experiments are needed to improve the confidence in the simulation of large-scale reactor operation.

Skocypec, R.D.; Hogan, R.E. Jr.; Muir, J.F. (Sandia National Labs., Albuquerque, NM (United States))

1994-06-01

142

Solar reforming of methane in a direct absorption catalytic reactor on a parabolic dish: 2, Modeling and analysis  

SciTech Connect

The CAtalytically Enhanced Solar Absorption Receiver (CAESAR) experiment was conducted to determine the thermal, chemical, and mechanical performance of a commercial-scale, dish-mounted, direct catalytic absorption receiver (DCAR) reactor over a range of steady state and transient (cloud) operating conditions. The focus of the experiment is on global performance such as receiver efficiencies and overall methane conversion; it was not intended to provide data for code validation. A numerical model was previously developed to provide guidance in the design of the absorber. The one-dimensional, planar and steady-state model incorporates, the following energy transfer mechanisms: solar and infrared radiation, heterogeneous chemical reaction, conduction in the solid phase, and convection between the fluid and solid phases. A number of upgrades to the model and improved property values are presented here. Model predictions are shown to bound the experimental axial thermocouple data when experimental uncertainties are included. Global predictions are made using a technique in which the incident solar flux distribution is subdivided into flux contour bands. Model predictions for each band are then spatially integrated to provide global predictions such as reactor efficiencies and methane conversions. Global predictions are shown to compare well with experimental data. Reactor predictions for anticipated operating conditions suggest a further decrease in optical density at the front of the absorber inner disk may be beneficial. The need to conduct code-validation experiments is identified as essential to improve the confidence in the capability to predict large-scale reactor operation.

Skocypec, R.D.; Hogan, R.E. Jr.; Muir, J.F.

1991-01-01

143

Solar reforming of methane in a direct absorption catalytic reactor on a parabolic dish. 2: Modeling and analysis  

NASA Astrophysics Data System (ADS)

The catalytically enhanced solar absorption receiver (CAESAR) experiment was conducted to determine the thermal, chemical, and mechanical performance of a commercial-scale, dish-mounted, direct catalytic absorption receiver (DCAR) reactor over a range of steady state and transient (cloud) operating conditions. The focus of the experiment is on global performance such as receiver efficiencies and overall methane conversion; it was not intended to provide data for code validation. A numerical model was previously developed to provide guidance in the design of the absorber. The one-dimensional, planar and steady-state model incorporates, the following energy transfer mechanisms: solar and infrared radiation, heterogeneous chemical reaction, conduction in the solid phase, and convection between the fluid and solid phases. A number of upgrades to the model and improved property values are presented here. Model predictions are shown to bound the experimental axial thermocouple data when experimental uncertainties are included. Global predictions are made using a technique in which the incident solar flux distribution is subdivided into flux contour bands. Model predictions for each band are then spatially integrated to provide global predictions such as reactor efficiencies and methane conversions. Global predictions are shown to compare well with experimental data. Reactor predictions for anticipated operating conditions suggest a further decrease in optical density at the front of the absorber inner disk may be beneficial. The need to conduct code-validation experiments is identified as being essential in improving the confidence in the capability to predict large-scale reactor operation.

Skocypec, Russell D.; Hogan, Roy E., Jr.; Muir, James F.

1991-01-01

144

Solar-parabolic dish-Stirling-engine-system module. Task 1: Topical report, market assessment/conceptual design  

SciTech Connect

The major activities reported are: a market study to identify an early market for a dish-Stirling module and assess its commercial potential; preparation of a conceptual system and subsystem design to address this market; and preparation of an early sales implementation plan. A study of the reliability of protection from the effects of walk-off, wherein the sun's image leaves the receiver if the dish is not tracking, is appended, along with an optical analysis and structural analysis. Also appended are the relationship between PURPA and solar thermal energy development and electric utility pricing rationale. (LEW)

Not Available

1982-11-30

145

Optimal Heat Collection Element Shapes for Parabolic Trough Concentrators  

SciTech Connect

For nearly 150 years, the cross section of the heat collection tubes used at the focus of parabolic trough solar concentrators has been circular. This type of tube is obviously simple and easily fabricated, but it is not optimal. It is shown in this article that the optimal shape, assuming a perfect parabolic figure for the concentrating mirror, is instead oblong, and is approximately given by a pair of facing parabolic segments.

Bennett, C

2007-11-15

146

Solar Week Thursday: Shoebox Solar Water Heater  

NSDL National Science Digital Library

This is an activity during Solar Week, a twice-yearly event in March and October during which classrooms are able to interact with scientists studying the Sun. Outside of Solar Week, information, activities, and resources are archived and available online at any time. This is an activity about reflection. In this hands-on activity, learners will build a solar water heater by lining a box with reflective material, adding a translucent cover, and adding water-filled cans that are painted black. The temperature of the water is taken and recorded every fifteen minutes. This activity can use the same solar cooker built for the Solar Week Thursday: Solar Pizza Box Cooker activity. This activity is scheduled to occur during Thursday of Solar Week, and it requires use of a sunny outdoor location for an extended period of time.

147

Cooking Amount Estimation of Rice Cooker by Signed Mahalanobis Distance  

NASA Astrophysics Data System (ADS)

This paper proposes a cooking amount estimation method for rice cookers based on Mahalanobis-Taguchi system. This estimation is important in that it can improve the cooking quality significantly. The proposed method enables us to estimate the amount in the early stage of cooking, thereby to give optimal heat in the whole process. To this end, an existing method adopts the minimal cooking quantity as a standard quantity and conduct estimation via outliers in terms of Mahalanobis distance, but this is easily affected by consumers' usage and nonlinearity peculiar to heat systems. Estimation precision is expected to be higher if the estimation is used by correlation of each characteristic data. The proposed method achieves this by adding sign to the estimation method for treating negative values in Mahalanobis distance, and verifies its effectiveness by experiments.

Suzuki, Arata; Sugimoto, Kenji

148

The French thermo-helio-electricity-KW parabolic dish program  

NASA Technical Reports Server (NTRS)

The testing and development of parabolic dish solar thermal power plants to produce, thermal mechanical, or electrical energy are discussed. The design, construction, and experiments of prototype collectors to prove the feasibility of such collectors is described.

Audibert, M.; Peri, G.

1982-01-01

149

Development Effort of Sheet Molding Compound (SMC) Parabolic Trough Panels.  

National Technical Information Service (NTIS)

The objectives of the development effort are to: investigate the problems of molding parabolic trough solar reflector panels of sheet molding compound (SMC); develop molding techniques and processes by which silvered glass reflector sheets can be integral...

P. A. Kirsch R. L. Champion

1982-01-01

150

Parabolic dish test site: History and operating experience  

NASA Technical Reports Server (NTRS)

The parabolic dish test site (PDTS) was established for testing point-focusing solar concentrator systems operating at temperatures approaching 1650 C. Among tests run were evaluation and performance characterization of parabolic dish concentrators, receivers, power conversion units, and solar/fossil-fuel hybrid systems. The PDTS was fully operational until its closure in June, 1984. The evolution of the test program, a chronological listing of the experiments run, and data summaries for most of the tests conducted are presented.

Selcuk, M. K. (compiler)

1985-01-01

151

Cylindro parabolical solar energy collector  

SciTech Connect

This collector comprises a reflector formed by a plurality of reflecting elements engaged between consecutive frames. Each of the frames is formed by two members moulded from Zanak and fixed to an aluminium beam having a triangular cross-sectional shape. Each pair of members defines arms whereby the reflector is rotatively mounted on a fixed absorber tube. The latter is protected by a transparent hood fixed on supports disposed on each side of the reflector. A device for adjusting the angular position of the reflector is provided at at least one end of the collector.

Boy-Marcotte, J. L. M. R.; Burnouf, C. D.; Chastang, G. J.; Salvaire, L. O.

1985-05-07

152

Direct steam generation in parabolic trough solar power plants: Numerical investigation of the transients and the control of a once-through system  

Microsoft Academic Search

Direct steam generation (DSG) in parabolic troughs was first studied in the early 1980s by Murphy (1982) and Pederson (1982). Intensive research on DSG then started in 1988, when Luz identified this technology as the desired system for a future generation of its power plants. These R and D activities were not terminated by Luz`s demise in 1991, but have

F. Lippke

1996-01-01

153

The Parabolic Spline Method  

NASA Astrophysics Data System (ADS)

A new and efficient parabolic spline based remapping algorithm is developed and tested herein. To ensure mass conservation, the scheme solves an integral form of the transport equation rather than the differential form. The integrals are computed from reconstructed parabolic splines with mass conservation constraints. For higher dimensions, this remapping can be used within a standard directional splitting methodology or within the flow-dependent cascade splitting approach. A grid and sub-grid based monotonic filter is also incorporated into the overall scheme. A truncation error analysis of the scheme is presented and discussed in terms of results from test cases. The analysis shows that although it has a similar truncation error in the converged limit as that of the widely used Piecewise Parabolic Method (PPM) for infinitely differentiable functions, PSM is more accurate than PPM for problems with slow spectral decay. Additionally, an operation count of the scheme is given which demonstrates the computational advantage of PSM compare

Zerroukat, M.; Wood, N.; Staniforth, A.

2006-08-01

154

A Slice of Solar Cooking.  

ERIC Educational Resources Information Center

Presents an inquiry activity in which students design a solar cooking apparatus. Students are also asked to write a paragraph that explains the ways in which science knowledge helped them in the design of their cooker. Includes a grading rubric. (SOE)

Galus, Pamela

2003-01-01

155

Solar energy in China  

NASA Astrophysics Data System (ADS)

The report presents the progress, status and goals of the Chinese national solar energy programs since 1970's. It applies specially to solar water heating, solar drying, passive solar, solar cookers, and solar photovoltaics. In China, an expert team has been organized, a number of technology development centers for new and renewable sources of energy have been set up and some demonstration projects are under way. Shortage of energy in China can not be expected to be overcome in a short period of time. The only way out is to adopt various kinds of energy conservation measures and increase the utilization of NRSE, while expanding the production of conventional energy.

Wennerholm, H.

156

Offset parabolic reflector antennas  

Microsoft Academic Search

The characteristics of offset parabolic reflector antennas are examined with particular reference to their use in satellite communication systems. Consideration is given to single offset reflector analysis, the electrical performance of the single offset reflector antenna, a design procedure for multiple spot-beam antennas, primary feeds for offset reflector antennas, and dual-reflector offset antennas.

A. W. Rudge

1983-01-01

157

Numerical modeling and experimental testing of a solar grill  

SciTech Connect

The sun provides a free, nonpolluting and everlasting source of energy. Considerable research has been carried out to utilize solar energy for purposes such as water heating, high temperature ovens, and conversion to electrical energy. One of the interesting forms for utilizing solar energy is cooking. The main disadvantage of solar energy systems has been the low efficiency attained in most of its practical applications. It is expected, however, that due to continuing decreases in the availability of other energy sources such as oil and coal, along with the safety problems associated with nuclear energy, man's need for utilization of solar energy will increase, thus leading him to find the ways and means to develop adequate and efficient solar-powered systems. In camps, where tents are used to accommodate people, cooking is done via conventional gas stoves. This usually takes place in extremely crowded areas which become highly fireprone. Solar oven cookers seem to be a viable alternative considering both economy and safety. Among the various forms of solar cookers, the oven-type solar cooker is known to be the best in terms of efficiency. One of the most practical and efficient forms of solar oven cookers is the outdoor portable solar grill (Bar-B-Q), developed by Khalifa et al. The solar grill is a light and portable unit that utilizes solar energy to grill meat. One of the best types of grilling with this cooker is the well-known Shish Kebab or Bar-B-Q. A detailed description for the design of the solar grill is provided as follows. This paper is aimed at providing experimental results and formulating a numerical model for the solar grill. Results of the two approaches are then compared to verify the validity of the numerical simulation. An experimental and theoretical investigation was conducted on the solar grill in order to study the factors that affect its design and performance.

Olwi, I.; Khalifa, A. (King Abdulaziz Univ., Jeddah (Saudi Arabia))

1993-02-01

158

The Pressure Cooker: A Module on the Properties of Matter. Tech Physics Series.  

ERIC Educational Resources Information Center

Experiments to provide an understanding of the principles related to the pressure cooker are presented. Objectives included are designed to provide the learner with the ability to calibrate a thermistor for measuring temperature; explain the meaning of latent and specific heat; calculate latent and specific heat; use a Bourdon tube pressure gauge…

Technical Education Research Center, Cambridge, MA.

159

Understanding the Clausius-Clapeyron Equation by Employing an Easily Adaptable Pressure Cooker  

ERIC Educational Resources Information Center

This article describes a simple and inexpensive laboratory exercise developed to understand the effect of pressure on phase equilibrium as described by the Clausius-Clapeyron equation. The only piece of equipment required is a pressure cooker adapted with a pressure gauge and a thermometer in the lid, allowing the measurement of the pressure and…

Galleano, Monica; Boveris, Alberto; Puntarulo, Susana

2008-01-01

160

A modified concentrating type solar oven for outdoor cooking  

SciTech Connect

Solar cookers offer a partial solution to many problems for the poor developing areas of the world. In these regions energy used for cooking sometimes comprises four fifths of the total energy demand. Solar cookers are generally four catagories: direct focusing, oven, ovenfocusing and indirect types. The direct focusing types failed to boil water under windy conditions due to excessive convection losses from the bare cooking pot placed at the concentrator focus. The oven type cookers, such as Telkes oven, observe the rules of energy conservation and thus are more efficient and less affected by windy weather. However, this oven suffers from two major problems. First, tilting the oven could cause food spillage unless a hinged support is used for the pot. This adds complication to the design of Telkes oven. Second, the solar radiation is added to the pot from the top for high solar altitude angles. This leads to poor heat transfer to the food inside the pot. The advantages of concentrating and oven cookers can be obtained by widding of a point focus concentrator to a new oven type receiver. In this paper the concept and design details of such an oven are introduced. Theoretical and experimental analyses of the developed cooker are given.

Khalifa, A.M.A.

1983-12-01

161

Solar Energy Education. Home economics: student activities. Field test edition  

SciTech Connect

A view of solar energy from the standpoint of home economics is taken in this book of activities. Students are provided information on solar energy resources while performing these classroom activities. Instructions for the construction of a solar food dryer and a solar cooker are provided. Topics for study include window treatments, clothing, the history of solar energy, vitamins from the sun, and how to choose the correct solar home. (BCS)

Not Available

1981-03-01

162

Offset parabolic reflector antennas  

Microsoft Academic Search

\\u000a Abstract  The paper provides a tutorial review of a number of offset parabolic reflector configurations including both single and double-reflector\\u000a geometries. The author commences by describing some basic techniques which can be applied to predict the vector radiation\\u000a fields and provides some indication of the validity of these methods. The formulation of a relatively simple analytical model\\u000a for the offset reflector

Alan Walter Rudge

1984-01-01

163

Control concepts for direct steam generation in parabolic troughs  

Microsoft Academic Search

A new prototype parabolic-trough collector system was erected at the Plataforma Solar de Almer??a (PSA) (1996–1998) to investigate direct steam generation (DSG) in a solar thermal power plant under real solar conditions. The system has been under evaluation for efficiency, cost, control and other parameters since 1999. The main objective of the control system is to obtain steam at constant

Loreto Valenzuela; Eduardo Zarza; Manuel Berenguel; Eduardo F. Camacho

2005-01-01

164

[Gas cookers as a source of benz(a)pyrene emission].  

PubMed

The spectrofluorimetric method of bez(a)pyrene was used without separating it from other polycyclic aromatic hydrocarbons. On the basis of that method the content of that compound was measured in air contaminated with gas after burning of gas cookers. The study showed that this compound is not present in Warsow when earth gas is burning, but burning of propane-butane mixture contaminates air with this compound in a considerable degree. PMID:8016553

Koz?owski, J

1993-01-01

165

Analysis and conceptual design of a lunar radiator parabolic shade  

NASA Technical Reports Server (NTRS)

On the moon, the available heat sink temperature for a vertical unshaded radiator at the equator is 322 K. A method of reducing this heat sink temperature using a parabolic trough shading device was investigated. A steady state heat balance was performed to predict the available heat sink temperature. The effect of optical surface properties on system performance was investigated. Various geometric configurations were also evaluated. A flexible shade conceptual design is presented which greatly reduces the weight and stowed volume of the system. The concept makes use of the natural catenary shape assumed by a flexible material when supported at two points. The catenary shape is very near parabolic. The lunar radiator parabolic shade design presented integrates the energy collection and rejection of a solar dynamic power cycle with the moderate temperature waste heat rejection of a lunar habitat.

Ewert, Michael K.; Clark, Craig S.

1991-01-01

166

Pupil Size in Parabolic Flight.  

National Technical Information Service (NTIS)

The pupil size was observed in ten human test subjects during parabolic flight. Microgravity induces a pupillary dilation, whereas in periods of high gravity load a constriction of the pupil is seen. The assumption of a vestibulo pupillary reflex mechanis...

H. W. Kortschot W. J. Oosterveld H. A. A. Dejong

1990-01-01

167

Parabolic Concentrating Collector: A Tutorial.  

National Technical Information Service (NTIS)

A tutorial overview of point-focusing parabolic collectors is presented. Optical and thermal characteristics of such collectors are discussed. Data representing typical achievable collector efficiencies are presented and the importance of balancing collec...

V. C. Truscello

1979-01-01

168

Nanoengineered parabolic liquid mirrors  

NASA Astrophysics Data System (ADS)

We give a progress report on an application of a new class of versatile optical elements pioneered by our laboratory: By coating liquids we create reflective surfaces that can be shaped by rotation into a parabolic mirror. Coated ferrofluids can also be shaped with magnetic fields. Low cost is what makes rotating mercury LM Telescopes interesting. However, they are limited by the fact that they cannot be tilted. We are now working on a new generation of LMs that can be tilted. The goal is to produce large inexpensive LMTs that can be tilted by at least twenty degrees. Early work demonstrated a tilted LM that used a high viscosity liquid. An extrapolation law, confirmed by our experiments, shows that it should be possible to tilt LMs by twenty degrees, assuming a liquid having a few times the viscosity of glycerin. Rotating nanoengineered LMTs are interesting even without tilting, since their lower weight would make then less costly than Hg mirrors and high viscosity makes them less sensitive to winds. We have made two major recent technological breakthroughs: We have made a robotic machine which is capable of producing the large quantities of coating material required for large mirrors. We have also developed a technique that allows us to coat the appropriate class of liquids by simply spraying the nanoengineered coating on them. In this contribution, we present optical tests of our liquids as well as optical shop tests of rotating mirrors.

Borra, E. F.; Brousseau, D.; Gagné, G.; Faucher, L.; Ritcey, A. M.

2006-06-01

169

Solar water-sterilization system with thermally-controlled flow  

Microsoft Academic Search

The presented system is used to produce relatively larger amounts of sterilized water than by merely putting a fixed amount of contaminated water in a small bottle inside a hot box solar cooker (HBSC). For achieving a specified temperature with the HBSC, a thermostat attached to a solenoid valve is placed at the outlet port of the HBSC to ensure

T. S. Saitoh; H. H. El-Ghetany

1999-01-01

170

Progress in solar thermal distributed receiver technology  

NASA Astrophysics Data System (ADS)

A brief discussion is given on the fundamentals of parabolic dish collectors. Private and Department of Energy supported projects which employ parabolic dish collector systems are described. These projects include: the Distribution Receiver Test Facility, Shenandoah Solar Total Energy Project, Vangurd I, Solar Plant No. 1, the Dish/Stirling Solar Electric Generating System, the Organic Rankine Cycle, and the Solarized Automotive Gas Turbine.

Leonard, J. A.; Otts, J. V.

171

Parabolized stability equations  

NASA Technical Reports Server (NTRS)

The parabolized stability equations (PSE) are a new approach to analyze the streamwise evolution of single or interacting Fourier modes in weakly nonparallel flows such as boundary layers. The concept rests on the decomposition of every mode into a slowly varying amplitude function and a wave function with slowly varying wave number. The neglect of the small second derivatives of the slowly varying functions with respect to the streamwise variable leads to an initial boundary-value problem that can be solved by numerical marching procedures. The PSE approach is valid in convectively unstable flows. The equations for a single mode are closely related to those of the traditional eigenvalue problems for linear stability analysis. However, the PSE approach does not exploit the homogeneity of the problem and, therefore, can be utilized to analyze forced modes and the nonlinear growth and interaction of an initial disturbance field. In contrast to the traditional patching of local solutions, the PSE provide the spatial evolution of modes with proper account for their history. The PSE approach allows studies of secondary instabilities without the constraints of the Floquet analysis and reproduces the established experimental, theoretical, and computational benchmark results on transition up to the breakdown stage. The method matches or exceeds the demonstrated capabilities of current spatial Navier-Stokes solvers at a small fraction of their computational cost. Recent applications include studies on localized or distributed receptivity and prediction of transition in model environments for realistic engineering problems. This report describes the basis, intricacies, and some applications of the PSE methodology.

Herbert, Thorwald

1994-01-01

172

Solar thermal technology evaluation, fiscal year 1982. Volume 1: Executive summary  

NASA Technical Reports Server (NTRS)

Three primary solar concepts the central receiver, parabolic dish, and parabolic trough are investigated. To a lesser extent, the hemispherical bowl and salt-gradient solar pond are also being studied. Each technology is described.

1983-01-01

173

Engineering parabolic beams with dynamic intensity profiles.  

PubMed

We present optical fields formed by superposing nondiffracting parabolic beams with distinct longitudinal wave-vector components, generating light profiles that display intensity fluxes following parabolic paths in the transverse plane. Their propagation dynamics vary depending on the physical mechanism originating interference, where the possibilities include constructive and destructive interference between traveling parabolic beams, interference between stationary parabolic modes, and combinations of these. The dark parabolic region exhibited by parabolic beams permits a straightforward superposition of intensity fluxes, allowing formation of a variety of profiles, which can exhibit circular, elliptic, and other symmetries. PMID:24323204

Ruelas, Adrian; Lopez-Aguayo, Servando; Gutiérrez-Vega, Julio C

2013-08-01

174

Non-Formal Environmental Education: The Utilization of Solar Energy for Cooking in a Rural Area in Sudan.  

ERIC Educational Resources Information Center

In El Sururab in rural Sudan, solar energy is used for cooking instead of wood. This study explored the efficiency of a hot-box type of solar cooker for storing heat and its effectiveness for different methods of cooking various foods used daily in El Sururab. Forty local women served as a respondent group. (PVD)

El Zubeir, Z.

1997-01-01

175

Pre- and post-natal exposure of children to EMF generated by domestic induction cookers  

NASA Astrophysics Data System (ADS)

Induction cookers are a type of cooking appliance that uses an intermediate-frequency magnetic field to heat the cooking vessel. The magnetic flux density produced by an induction cooker during operation was measured according to the EN 62233 standard, and the measured values were below the limits set in the standard. The measurements were used to validate a numerical model consisting of three vertically displaced coaxial current loops at 35 kHz. The numerical model was then used to compute the electric field (E) and induced current (J) in 26 and 30 weeks pregnant women and 6 and 11 year old children. Both E and J were found to be below the basic restrictions of the 2010 low-frequency and 1998 ICNRIP guidelines. The maximum computed E fields in the whole body were 0.11 and 0.66 V m-1 in the 26 and 30 weeks pregnant women and 0.28 and 2.28 V m-1 in the 6 and 11 year old children (ICNIRP basic restriction 4.25 V m-1). The maximum computed J fields in the whole body were 46 and 42 mA m-2 in the 26 and 30 weeks pregnant women and 27 and 16 mA m-2 in the 6 and 11 year old children (ICNIRP basic restriction 70 mA m-2).

Kos, Bor; Vali?, Blaž; Miklav?i?, Damijan; Kotnik, Tadej; Gajšek, Peter

2011-10-01

176

Composite isogrid structures for parabolic surfaces  

NASA Technical Reports Server (NTRS)

The invention relates to high stiffness parabolic structures utilizing integral reinforced grids. The parabolic structures implement the use of isogrid structures which incorporate unique and efficient orthotropic patterns for efficient stiffness and structural stability.

Silverman, Edward M. (Inventor); Boyd, Jr., William E. (Inventor); Rhodes, Marvin D. (Inventor); Dyer, Jack E. (Inventor)

2000-01-01

177

Criteria for evaluation of reflective surface for parabolic dish concentrators  

NASA Technical Reports Server (NTRS)

Commercial, second surface glass mirror are emphasized, but aluminum and metallized polymeric films are also included. Criteria for sealing solar mirrors in order to prevent environmental degradation and criteria for bonding sagged or bent mirrors to substrate materials are described. An overview of the technical areas involved in evaluating small mirror samples, sections, and entire large gores is presented. A basis for mirror criteria was established that eventually may become part of inspection and evaluation techniques for three dimensional parabolic reflective surfaces.

Bouquet, F.

1980-01-01

178

Parabolic resonances in near integrable Hamiltonian systems  

Microsoft Academic Search

When an integrable Hamiltonian system, possessing an m-resonant lower dimensional normally parabolic torus is perturbed, a parabolic m-resonance occurs. If, in addition, the iso-energetic non-degeneracy condition for the integrable system fails, the near integrable Hamiltonian exhibits a flat parabolic m-resonance. It is established that most kinds of parabolic resonances are persistent in n(n>=3) d.o.f. near integrable Hamiltonians, without the use

Anna Litvak-Hinenzon; Vered Rom-Kedar

2000-01-01

179

Solar thermal parabolic dish energy applications  

NASA Technical Reports Server (NTRS)

Vu-graphs are presented that show that applications are a viable distributed renewable power generation option. Quality energy can be produced in the form of electricity and high temperature heat. Modular systems are described that can be distributed to new or existing plants and that are mass producible with the associated economies of production.

Pijawka, W.

1981-01-01

180

Fuse Protects Parabolic-Dish Solar Collector  

NASA Technical Reports Server (NTRS)

Sliding barrel and shutter protect against overheating. Downward movement of shutter initiated by melting of fuse wire that suspends it. Shutter lowered or raised under operator's control by depressuring or pressurizing hydraulic cylinder.

Selcuk, M. K.

1983-01-01

181

Parabolic tapers for overmoded waveguides  

DOEpatents

A waveguide taper with a parabolic profile, in which the distance along the taper axis varies as the square of the tapered dimension, provides less mode conversion than equal length linear tapers and is easier to fabricate than other non-linear tapers.

Doane, J.L.

1983-11-25

182

A Solar High Temperature Kiln.  

National Technical Information Service (NTIS)

The feasibility of using solar energy in developing countries for baking ceramic construction materials was investigated. The solar high temperature kiln is described. It uses two parabolic concentrators which direct available radiation into the baking ch...

N. Huettenhoelscher K. Bergmann

1981-01-01

183

THE SOLAR OVEN: DEVELOPMENT AND FIELD-TESTING OF USER-MADE DESIGNS IN INDONESIA  

Microsoft Academic Search

This paper considers the design, use, and social acceptance of solar cookers that are constructed by their users. Several generations of oven design are described and their field testing in Indonesia, are reported, the first generation design having been described in a previous paper. The second generation design reached 175°C in oven temperature, and it used only local materials in

Herliyani Suharta; K Abdullah; A Sayigh

1998-01-01

184

Parabolic Throw with Video Model  

NSDL National Science Digital Library

The Parabolic Throw with Video Model overlays an EJS model on a video of a ball being thrown. The video displays 15 frames per second and a vertical calibration bar. The simulation superimposes a trajectory of a red circle with acceleration x'' = -g, where g is the acceleration due to gravity. The user sets the initial conditions and the value of g in order to match the trajectory shown on the video. This model uses the Xuggle video library and is designed to test the EJS video API. A warning message is displayed if Xuggle is not installed. The Parabolic Throw with Video Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_mech_ParabolicThrowWithVideo.jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item.

Franciscouembre

2011-12-30

185

Effects of the Sun on our Planet  

NSDL National Science Digital Library

Students experiment with plants, light, heat, and water evaporation. They experiment with solar cells to design a simple solar cooker, create a "solar-powered" method to perform a routine task, or build a parabolic solar collector. They explore radio signals during daytime and nighttime. Older students construct an ionosphere monitor to track solar storms and other changes in the ionosphere.

2013-06-12

186

Heat and Chemical Exergy Analysis of Parabolic Trough Collector  

NASA Astrophysics Data System (ADS)

Emissions of greenhouse gases and other pollutants, derived from the combustion of fossil fuels for heat and electricity generation, can be significantly reduced or even completely eliminated by substituting fossil fuels with a clean energy source, e.g. solar energy. However, solar radiation reaching the earth is diluted, intermittent, and, unequally distributed. These disadvantages can be overcome by converting solar energy into chemical energy carriers, i.e. solar fuels, such as solar hydrogen and solar methanol, which can be long-termed stored and long-ranged transported. Since the energy conversion efficiency of thermochemical processes is limited by the Carnot efficiency, the use of concentrated solar radiation as the source of high-temperature process heat provides a thermodynamically efficient path for the conversion of solar energy into chemical fuels. In this study, water-gas shift reaction in parabolic trough collector is evaluated with regarding the heat exergy and chemical exergy analyses and the results are given as tables and graphs.

Öztürk, M.; Üçgül, I.; Özek, N.

2007-04-01

187

Solar powered tracking device  

Microsoft Academic Search

The paper describes the design and operation of a device for tracking the traverse of the sun across the sky, to be used in conjunction with a solar concentrator to ensure maximum solar energy collection. The tracking device consists of two solar energy sensors positioned on opposite sides of a parabolic concentrator which faces south and rotates about the north-south

C. A. Morrison; E. A. Farber; H. A. Ingley; D. B. Wiggins

1976-01-01

188

Study on Pot Forming of Induction Heater Type Rice Cookers by Forging Cast Process  

NASA Astrophysics Data System (ADS)

This paper describes a study result on pot fabrication by the forging cast process of stainless steel with aluminum. Rice cooked with the new bowl-shaped pot for the induction heater type rice cookers is better tasting than rice cooked with the conventional cylindrical one, due to the achievement of better heat conduction and convection. The conventional pot is made of the clad sheet, consisting of stainless steel and aluminum. However, it is rather difficult to form a bowl shape from the clad sheet, primarily due to the problem of a material spring back. The fabrication of a new type of a pot was made possible by means of the adoption of a forging cast process instead of the clad sheet. In this process, iron powder is inserted between stainless steel and aluminum in order to alleviate the large difference on the coefficient of expansion between each material. It was made clear that the application of two kinds of iron particle, namely 10 ?m size powder on the stainless steel side and 44 ?m on the aluminum side, enables the joints to become strong enough. The joint strength of the new pot by this fabrication process was confirmed by the tests of the shear strength and the fatigue tests together with the stress analysis.

Ohnishi, Masayuki; Yamaguchi, Mitsugi; Ohashi, Osamu

189

Dispersion managed self-similar parabolic pulses  

Microsoft Academic Search

We describe the propagation of a parabolic self-similar pulse in an anomalous dispersive nonlinear fibre. Given the capacity of a linearly chirped parabolic pulse to retain its typical shape over a short propagation distance, we introduce the concept of dispersion managed self-similar pulses and outline potential benefits in terms of spectral broadening enhancement.

Christophe FINOT

2008-01-01

190

Parabolic Herz Spaces and their Applications  

NASA Astrophysics Data System (ADS)

The note is a natural continuations of the study started in [7]. In Herz spaces endowed with parabolic metric are proved regularity results of weak solutions to divergence form parabolic equations having discontinuous coefficients, using boundedness of integral operators and commutators generated by VMO functions and Calderón-Zygmund operators.

Ragusa, Maria Alessandra

2010-09-01

191

Imaging of radar targets using parabolic reflectors  

Microsoft Academic Search

Summary form only given. We consider the problem of imaging of radar targets using parabolic reflectors. The radar target is represented as a summation of point sources of appropriate strength and polarization. Using traditional vector electromagnetic (EM) field theory, the EM field produced by these sources in the vicinity of the parabolic reflector (far field) is calculated. Subsequently, the electric

D. Houpis; P. Frangos; N. Uzunoglu

2000-01-01

192

Reflector surface deviations in large parabolic antennas  

Microsoft Academic Search

One of the important factors affecting the efficiency of parabolic reflector antennas is the degree to which the surface of the reflector deviates from the true parabolic shape. For a given reflector surface it is also important to locate the focal point of the best-fit paraboloid relative to the existing feed support structure. A simple method is presented for making

L. Anderson; L. Groth

1963-01-01

193

Interacting electrons in parabolic quantum dots  

Microsoft Academic Search

The problem of interacting electrons in a parabolic confinement has attracted considerable attention recently since experiments on parabolic quantum dots have revealed peculiar properties. We investigate this phenomenon numerically. To this end we diagonalize the Hamiltonian for Coulomb as well as for short range interactions using the Hartree-Fock based exact diagonalization method. In addition to the ground state energy we

Michael Schreiber; Jens Siewert; Thomas Vojta

2001-01-01

194

Overview of software development at the parabolic dish test site  

NASA Technical Reports Server (NTRS)

The development history of the data acquisition and data analysis software is discussed. The software development occurred between 1978 and 1984 in support of solar energy module testing at the Jet Propulsion Laboratory's Parabolic Dish Test Site, located within Edwards Test Station. The development went through incremental stages, starting with a simple single-user BASIC set of programs, and progressing to the relative complex multi-user FORTRAN system that was used until the termination of the project. Additional software in support of testing is discussed including software in support of a meteorological subsystem and the Test Bed Concentrator Control Console interface. Conclusions and recommendations for further development are discussed.

Miyazono, C. K.

1985-01-01

195

Ten Thousand Solar Constants Radiometer  

NASA Technical Reports Server (NTRS)

"Radiometer for Accurate (+ or - 1%) Measurement of Solar Irradiances Equal to 10,000 Solar Constants," gives additional information on radiometer described elsewhere. Self-calibrating, water-cooled, thermopile radiometer measures irradiance produced in solar image formed by parabolic reflector or by multiple-mirror solar installation.

Kendall, J. M., Sr.

1985-01-01

196

Parabolic curves in Lie groups  

SciTech Connect

To interpolate a sequence of points in Euclidean space, parabolic splines can be used. These are curves which are piecewise quadratic. To interpolate between points in a (semi-)Riemannian manifold, we could look for curves such that the second covariant derivative of the velocity is zero. We call such curves Jupp and Kent quadratics or JK-quadratics because they are a special case of the cubic curves advocated by Jupp and Kent. When the manifold is a Lie group with bi-invariant metric, we can relate JK-quadratics to null Lie quadratics which arise from another interpolation problem. We solve JK-quadratics in the Lie groups SO(3) and SO(1,2) and in the sphere and hyperbolic plane, by relating them to the differential equation for a quantum harmonic oscillator00.

Pauley, Michael [School of Mathematics and Statistics, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009 (Australia)

2010-05-15

197

THE DISS PROJECT: DIRECT STEAM GENERATION IN PARABOLIC TROUGHS OPERATION AND MAINTENANCE EXPERIENCE UPDATE ON PROJECT STATUS  

Microsoft Academic Search

The DISS (DIrect Solar Steam) project is a complete R+TD program aimed at developing a new generation of solar thermal power plants with direct steam generation (DSG) in the absorber tubes of parabolic trough collectors. During the first phase of the project (1996-1998), a life-size test facility was implemented at the Plataforma Solar de Almería (PSA) to investigate under real

Eduardo Zarza; Loreto Valenzuela; Javier León; Markus Eck; Klaus Hennecke

198

The Jacobi-matrix method in parabolic coordinates: Expansion of Coulomb functions in parabolic Sturmians  

Microsoft Academic Search

Previous analysis of the Jacobi-matrix method based on the underlying SO(2,1) Lie algebra is extended to the Coulomb Hamiltonian in parabolic coordinates. The general solution of the generic SO(2,1) eigenvalue equation is constructed and special cases, which furnish expansions of the Coulomb functions &psgr;(±)k(r) in a complete set of parabolic Sturmians, are discussed.

P. C. Ojha

1987-01-01

199

Solar  

NSDL National Science Digital Library

What part does solar energy play in satisfying energy demands? This informational piece, part of a series about the future of energy, introduces students to solar energy. Here students read about the uses, benefits, and active and passive methods of solar energy. Information is also presented about limitations, geographical considerations of solar power in the United States, and current uses of solar energy around the world. Thought-provoking questions afford students chances to reflect on what they've read about the uses of solar energy. Articles and information about a solar power plant in the Mohave Desert, the use of solar energy in Iowa, and statistics about solar energy are provided in a sidebar.

Project, Iowa P.

2004-01-01

200

Development effort of sheet molding compound /SMC/ parabolic trough panels  

NASA Astrophysics Data System (ADS)

Technical considerations at efforts to develop parabolic solar reflectors using sheet molding compounds with glass reflectors molded into the troughs are described. Strengthening of mirrored glass sheets followed by application of an adhesive was found to provide good protection for both the silvered back of the mirror and the sheet molding compound after the two were joined in a single press stroke of a compression molding process. Details of the prototype one meter wide troughs with a 19.01 in. focal length are provided, including design solutions such as three external ribs joined to two external coaming ribs to provide the required stiffness. Changes in the size of the sheet molding after curing and in cooling to room temperature were accounted for by modeling with an appropriate standard deviation, and fabricating the trough panel mold to a smaller focal length, 18.95 in. Prospects for transferring the techniques to mass production are considered favorable.

Kirsch, P. A.; Champion, R. L.

201

Parabolicity and Existence of Dirichlet Finite Biharmonic Functions.  

National Technical Information Service (NTIS)

It is known that parabolicity implies non-existence of Dirichlet finite harmonic functions. In contrast, it is shown that there exist parabolic manifolds of any dimension which carry Dirichlet finite biharmonic functions. Moreover, there exist both hyperb...

L. Sario C. Wang

1972-01-01

202

Chaotic motion of comets in near-parabolic orbit: Mapping aproaches  

NASA Astrophysics Data System (ADS)

There exist many comets with near-parabolic orbits in the solar system. Among various theories proposed to explain their origin, the Oort cloud hypothesis seems to be the most reasonable. The theory assumes that there is a cometary cloud at a distance 103 to 107 from the sun and that perturbing forces from planets or stars make orbits of some of these comets become the near-parabolic type. Concerning the evolution of these orbits under planetary perturbations, we can raise the question: Will they stay in the solar system forever or will they escape from it? This is an attractive dynamical problem. If we go ahead by directly solving the dynamical differential equations, we may encounter the difficulty of long-time computation. For the orbits of these comets are near-parabolic and their periods are too long to study on their long-term evolution. With mapping approaches the difficulty will be overcome. In another aspect, the study of this model has special meaning for chaotic dynamics. We know that in the neighborhood of any separatrix i.e. the trajectory with zero frequency of the uperturbed motion of a Hamiltonian system, some chaotic motions have to be expected. Actually, the simplest example of separatrix is the parabolic trajectory of the two-body problem which separates the bounded and unbounded motion. From this point of view, the dynamical study of near-parabolic motion is very important. Petrosky's elegant but more abstract deduction gives a Kepler mapping which describes the dynamics of the cometary motion. In this paper we derive a similar mapping directly and discuss its dynamical characters.

Liu, Jie; Sun, Yi-Sui

1994-09-01

203

Analysis method of parabolic reflector antenna  

Microsoft Academic Search

This paper describes the analysis method of parabolic reflector antenna. The analysis parameters of the antenna system are optimal antenna diameter, offset height, focal point length, feed horn type and horn size, F\\/D and the coordinate of offset horns. The paper deals with the method to determine design core parameters of optimal antenna diameter, feed horn type and horn size,

Jcom-Hun Lee; Seong-Pal Lee

2005-01-01

204

Discontinuous Mixed Covolume Methods for Parabolic Problems  

PubMed Central

We present the semidiscrete and the backward Euler fully discrete discontinuous mixed covolume schemes for parabolic problems on triangular meshes. We give the error analysis of the discontinuous mixed covolume schemes and obtain optimal order error estimates in discontinuous H(div) and first-order error estimate in L2.

Zhu, Ailing

2014-01-01

205

Manufacture of large, lightweight parabolic antennas  

NASA Technical Reports Server (NTRS)

Antenna was produced in segments. Parabole sections were built up as aluminum foil sandwich with core bonded by film adhesive; whole structure was oven-cured after assembly. Structure was assembled with special tool for splice-bonding segments into complete dish, and inflatable bladder to apply pressure at joints during cure.

Hooper, S. W.

1973-01-01

206

Complex demodulation of baroreflex during parabolic flight  

Microsoft Academic Search

In this study we evaluated the usefulness of complex demodulation (CDM) for the assessment of baroreflex sensitivity (BRS) and time delay during dynamic changes of autonomic cardiovascular regulation induced by changing gravity during parabolic flight. BRS and time delay data assessed with CDM in the HF band are influenced by non-baroreflex coupling of heart rate and blood pressure variations. LF

K. Couckuyt; B. Verheyden; F. Beckers; J. Liu; A. E. Aubert

2006-01-01

207

Numerical Homogenization of Nonlinear Random Parabolic Operators  

Microsoft Academic Search

In this paper we study the numerical homogenization of nonlinear random parabolic equations. This procedure is developed within a finite element framework. A careful choice of multiscale finite element bases and the global formulation of the problem on the coarse grid allow us to prove the convergence of the numerical method to the homogenized solution of the equation. The relation

Y. Efendiev; A. Pankov

2004-01-01

208

Status of the current parabolic dish technology  

NASA Technical Reports Server (NTRS)

Vu-graphs are presented that show that point focus distributed receiver distributed generation systems are cost competitive with current utilities. System cost caveats and typical power module costs are described. Major problems inhibiting commercialization of the parabolic dish technology were reviewed.

Sumrall, C.

1981-01-01

209

A Parabolic Equation Propagation Loss Model.  

National Technical Information Service (NTIS)

A parabolic equation model for the prediction of acoustic propagation loss in a range-dependent ocean has been developed for use on the DRCS IBM 370/168 computer. Use of the model is outlined and several examples given. Particular attention is given to th...

G. Gartrell

1978-01-01

210

Group explicit methods for parabolic equations  

Microsoft Academic Search

In this paper, new explicit methods for the finite difference solution of a parabolic partial differential equation are derived. The new methods use stable asymmetric approximations to the partial differential equation which when coupled in groups of 2 adjacent points on the grid result in implicit equations which can be easily converted to explicit form which in turn offer many

D. J. Evans; A. R. B. Abdullah

1983-01-01

211

Low-cost and gram-scale synthesis of water-soluble Cu-In-S/ZnS core/shell quantum dots in an electric pressure cooker  

NASA Astrophysics Data System (ADS)

We report an electric pressure cooker for large-scale synthesis of water-soluble Cu-In-S/ZnS core/shell quantum dots. Low-cost thioglycolic acid and sodium citrate were used as the dual stabilizers. ~3 grams of quantum dots with a tunable emission from 545 to 610 nm and quantum yield up to 40% were obtained in a batch.We report an electric pressure cooker for large-scale synthesis of water-soluble Cu-In-S/ZnS core/shell quantum dots. Low-cost thioglycolic acid and sodium citrate were used as the dual stabilizers. ~3 grams of quantum dots with a tunable emission from 545 to 610 nm and quantum yield up to 40% were obtained in a batch. Electronic supplementary information (ESI) available: Experimental details, PL decay curves, PL lifetimes, EDS spectra, chemical composition, cost analysis. See DOI: 10.1039/c3nr05014a

Chen, Yanyan; Li, Shenjie; Huang, Lijian; Pan, Daocheng

2014-01-01

212

Trough integration into power plants—a study on the performance and economy of integrated solar combined cycle systems  

Microsoft Academic Search

Parabolic trough solar technology has been proven at nine commercial Solar Electric Generating Systems (SEGS) power plants that are operating in the California Mojave desert. These plants utilize steam Rankine cycle power plants, and as a result, most people associate parabolic trough solar technology with steam Rankine cycle power plant technology. Although these plants are clearly optimized for their particular

Jürgen Dersch; Michael Geyer; Ulf Herrmann; Scott A. Jones; Bruce Kelly; Rainer Kistner; Winfried Ortmanns; Robert Pitz-Paal; Henry Price

2004-01-01

213

Performance of a solar-thermal collector  

NASA Technical Reports Server (NTRS)

Possible means of achieving the technology required for field application of solar thermal power systems are discussed. Simplifications in construction techniques as well as in measurement techniques for parabolic trough collectors are described. Actual measurement data is also given.

Higa, W. H.

1975-01-01

214

A solar high temperature kiln  

NASA Astrophysics Data System (ADS)

The feasibility of using solar energy in developing countries for baking ceramic construction materials was investigated. The solar high temperature kiln is described. It uses two parabolic concentrators which direct available radiation into the baking chamber. The Sun tracker has only one axis. Preliminary test results with the prototype kiln were satisfactory.

Huettenhoelscher, N.; Bergmann, K.

1981-11-01

215

Stark effect in parabolic quantum dot  

Microsoft Academic Search

We theoretically investigate the optical properties of the exciton confined in parabolic quantum-dot , with and without electric field, by means of perturbative-variational method. The quantum-dot size enhances the 1s eigenvalue ahd oscillator strength . In smaller dot the relative extension of the exciton wave function is equal to the size of the dot . The 1s exciton bihding energy

S. JAZIRI; G. BASTARD; R. BENNACEUR

1993-01-01

216

The parabolic concentrating collector: A tutorial  

NASA Technical Reports Server (NTRS)

A tutorial overview of point-focusing parabolic collectors is presented. Optical and thermal characteristics are discussed. Data representing typical achievable collector efficiencies are presented and the importance of balancing collector cost with concentrator quality is argued through the development of a figure of merit. Various types of two-axis tracking collectors are described. The Department of Energy program to develop these devices is briefly discussed, as are present and projected costs for these collectors.

Truscello, V. C.

1979-01-01

217

An electrostatic parabolic density drift instability  

NASA Technical Reports Server (NTRS)

Assuming a uniform magnetic field and using the local approximation, the Vlassov theory for an electrostatic instability driven by a parabolic density gradient is considered. It is found that the instability grows only in the case of a sufficiently large, positive second derivative of the density. Linear growth rate parametric dependences are given, in addition to weakly nonlinear calculations on wave-particle transport due to this instability.

Gary, S. P.; Thomsen, M. F.

1982-01-01

218

Do-it-yourself guideline for constructing a solar alcohol distillation system  

Microsoft Academic Search

The development and testing of a solar powered distillation system are described. The system consists of a parabolic dish collector, a two axis sun tracking stand, sun tracking solar cell system, condenser, fermentation tanks, and continuous distillation still. The assembly instructions for the parabolic dish are included as well as the basic steps to follow in mashing and fermenting of

1982-01-01

219

Solar collector module  

SciTech Connect

An extended width parabolic trough solar collector is supported from pylons. Collector is formed from a center module and two wing modules joined together along abutting edges by connecting means. A stressed skin monocoque construction is used for each of the modules.

Hutchison, J.A.

1981-10-27

220

Solar collector module  

SciTech Connect

An extended width parabolic trough solar collector is supported from pylons. Collector is formed from a center module and two wing modules joined together along abutting edges by connecting means. A stressed skin monocoque construction is used for each of the modules.

Hutchison, J.A.

1983-02-08

221

Solar power plant  

Microsoft Academic Search

The specification discloses a solar power plant which utilizes a sun-tracking parabolic collector and a plurality of energy storage and conversion devices, all of which are operated under the control of a novel energy management system. Allocation of energy to a particular storage component or to useful output is dependent upon the state of the system as well as the

W. P. Dampier; R. C. Derby; S. P. Lazzara; S. H. Zelinger

1980-01-01

222

Solar power plant  

Microsoft Academic Search

A Solar Power Plant is described which utilizes a sun-tracking parabolic collector and a number of energy storage and conversion devices, operated under the control of a novel energy management system. Allocation of energy to a particular storage component or to useful output is dependent upon the state of the system as well as the nature of the demand. Outputted

R. C. Derby; S. H. Zelinger; W. P. Dampier; S. P. Lazzara

1978-01-01

223

Do-It-Yourself Guideline for Constructing a Solar Alcohol Distillation System.  

National Technical Information Service (NTIS)

The development and testing of a solar powered distillation system are described. The system consists of a parabolic dish collector, a two axis sun tracking stand, sun tracking solar cell system, condenser, fermentation tanks, and continuous distillation ...

B. W. Kennedy

1982-01-01

224

Femtosecond parabolic pulse shaping in normally dispersive optical fibers.  

PubMed

Formation of parabolic pulses at femtosecond time scale by means of passive nonlinear reshaping in normally dispersive optical fibers is analyzed. Two approaches are examined and compared: the parabolic waveform formation in transient propagation regime and parabolic waveform formation in the steady-state propagation regime. It is found that both approaches could produce parabolic pulses as short as few hundred femtoseconds applying commercially available fibers, specially designed all-normal dispersion photonic crystal fiber and modern femtosecond lasers for pumping. The ranges of parameters providing parabolic pulse formation at the femtosecond time scale are found depending on the initial pulse duration, chirp and energy. Applicability of different fibers for femtosecond pulse shaping is analyzed. Recommendation for shortest parabolic pulse formation is made based on the analysis presented. PMID:23938650

Sukhoivanov, Igor A; Iakushev, Sergii O; Shulika, Oleksiy V; Díez, Antonio; Andrés, Miguel

2013-07-29

225

Determinant line bundle on moduli space of parabolic bundles  

Microsoft Academic Search

In \\\\cite{BR1}, \\\\cite{BR2}, a parabolic determinant line bundle on a moduli space of stable parabolic bundles was constructed, along with a Hermitian structure on it. The construction of the Hermitian structure was indirect: The parabolic determinant line bundle was identified with the pullback of the determinant line bundle on a moduli space of usual vector bundles over a covering curve.

Indranil Biswas

2010-01-01

226

Bifurcation and Stability for a Nonlinear Parabolic Partial Differential Equation.  

National Technical Information Service (NTIS)

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.

N. Chafee

1973-01-01

227

Parabolic Trough VSHOT Optical Characterization in 2005-2006 (Presentation)  

SciTech Connect

This presentation regarding parabolic trough VSHOT optical characterization describes trough deployment and operation phases including: development, manufacture/installation, and maintenance/operation.

Wendelin, T.

2006-02-01

228

Numerical Schemes for Rough Parabolic Equations  

SciTech Connect

This paper is devoted to the study of numerical approximation schemes for a class of parabolic equations on (0,1) perturbed by a non-linear rough signal. It is the continuation of Deya (Electron. J. Probab. 16:1489-1518, 2011) and Deya et al. (Probab. Theory Relat. Fields, to appear), where the existence and uniqueness of a solution has been established. The approach combines rough paths methods with standard considerations on discretizing stochastic PDEs. The results apply to a geometric 2-rough path, which covers the case of the multidimensional fractional Brownian motion with Hurst index H>1/3.

Deya, Aurelien, E-mail: deya@iecn.u-nancy.fr [Universite de Nancy 1, Institut Elie Cartan Nancy (France)

2012-04-15

229

Surface roughness estimation of a parabolic reflector  

NASA Astrophysics Data System (ADS)

Random surface deviations in a reflector antenna reduce the aperture ef- ficiency. This communication presents a method for estimating the mean surface deviation of a parabolic reflector from a set of measured points. The proposed method takes into account systematic measurement errors, such as the offset between the origin of reference frame and the vertex of the surface, and the misalignment between the surface rotation axis and the measurement axis. The results will be applied to perform corrections to the surface of one of the 30 m diameter radiotelescopes at the Instituto Argentino de Radioastronomía (IAR).

Casco, N. A.

230

Spectral methods in time for parabolic problems  

NASA Technical Reports Server (NTRS)

A pseudospectral explicit scheme for solving linear, periodic, parabolic problems is described which has infinite accuracy both in time and in space. The high accuracy is achieved while the time resolution parameter M ( = ) (1/delta t) for time marching algorithm) and the space resolution parameter N B = O(1/detla x) have to satisfy M = O(N sup/+epsilon) epsilon O, compared to the common stability condition M = O(N sup 2) which has to be satisfied in any explicit finite order time algorithm.

Tal-Ezer, H.

1985-01-01

231

On the parallel solution of parabolic equations  

NASA Technical Reports Server (NTRS)

Parallel algorithms for the solution of linear parabolic problems are proposed. The first of these methods is based on using polynomial approximation to the exponential. It does not require solving any linear systems and is highly parallelizable. The two other methods proposed are based on Pade and Chebyshev approximations to the matrix exponential. The parallelization of these methods is achieved by using partial fraction decomposition techniques to solve the resulting systems and thus offers the potential for increased time parallelism in time dependent problems. Experimental results from the Alliant FX/8 and the Cray Y-MP/832 vector multiprocessors are also presented.

Gallopoulos, E.; Saad, Youcef

1989-01-01

232

Large-scale synthesis of well-dispersed copper nanowires in an electric pressure cooker and their application in transparent and conductive networks.  

PubMed

We present a novel large-scale synthetic method for well-separated copper nanowires (CuNWs) in a commercial electric pressure cooker under mild reaction conditions. CuNWs (?2.1 g) can be prepared in a batch with the cost of $4.20/g. Well-dispersed polyvinylpyrrolidone-capped CuNWs were obtained via a ligand-exchange method. The transparent and conductive CuNW networks with excellent electrical conductivity and high optical transmittance (30 ?/? at 86% transmittance, respectively) were fabricated by a spin-coating process. PMID:24750021

Li, Shenjie; Chen, Yanyan; Huang, Lijian; Pan, Daocheng

2014-05-01

233

Parabolic Dish Solar Thermal Power Annual Program Review Proceedings  

NASA Technical Reports Server (NTRS)

The development and testing of concentrators, receivers, and power conversion units are reported. System design and development for engineering experiments are described. Economic analysis and market assessments for advanced development activities are discussed. Technology development issues and application/user needs are highlighted.

Holbeck, H. J.

1981-01-01

234

The solar dynamic power system concept: Terrestrial experiences and their extension to space applications  

Microsoft Academic Search

The characteristics of solar thermal concentration power systems for terrestrial applications are described. Designs and experiences on steam and gas solar plants and components are reported. Comparison of alternatives for use in solar dynamic power systems (photovoltaic, solar dynamic, nuclear) shows an intermediate range of power where a potential exists for the use of solar dynamic systems adopting parabolic dish

A. Lucifredi; E. Ravina; F. Repetto

1986-01-01

235

ON A PARABOLIC EQUATION WITH A SINGULAR LOWER ORDER TERM  

Microsoft Academic Search

We obtain the existence of the weak Green's functions of parabolic equations with lower order coecients in the so called parabolic Kato class which is being proposed as a natural generalization of the Kato class in the study of elliptic equations. As a consequence we are able to prove the existence of solutions of some initial boundary value problems. Moreover,

QI ZHANG

236

The solution of the parabolized Navier-Stokes equations  

NASA Astrophysics Data System (ADS)

Solution of the parabolized Navier-Stokes equation using the stream-function/vorticity method; the velocity/vorticity-gradient method; pressure-uncoupling with the SIVA method; and pressure-uncoupling with the SIMPLE method is summarized. Full-Navier-Stokes solution by SIVA and SIMPLE; the partially-parabolic formulation; and the PHOENICS formulation are described.

Spalding, D. B.

1986-02-01

237

Heat and electricity from the sun using parabolic dish collector systems  

NASA Technical Reports Server (NTRS)

The paper investigates point focus distributed receiver (PFDR) solar thermal technology for the production of electric power and of industrial process heat. Attention is given to a thermal systems project conducted by JPL under DOE sponsorship. It is reported that project emphasis is on the development of cost-effective systems which will accelerate the commercialization and industrialization of plants up to 10 MWe, using parabolic dish collectors. Also discussed are the characteristics of PFDR systems, the cost targets for major systems hardware, and markets for this technology. Finally, the present system status of the technology development effort is discussed.

Truscello, V. C.; Williams, A. N.

1979-01-01

238

SunLab: Advancing Concentrating Solar Power Technology.  

National Technical Information Service (NTIS)

Concentrating solar power (CSP) technologies, including parabolic troughs, power towers, and dish/engines, have the potential to provide the world with tens of thousands of megawatts of clean, renewable, cost-competitive power.

1998-01-01

239

Solar energy modulator  

NASA Technical Reports Server (NTRS)

A module is described with a receiver having a solar energy acceptance opening and supported by a mounting ring along the optic axis of a parabolic mirror in coaxial alignment for receiving solar energy from the mirror, and a solar flux modulator plate for varying the quantity of solar energy flux received by the acceptance opening of the module. The modulator plate is characterized by an annular, plate-like body, the internal diameter of which is equal to or slightly greater than the diameter of the solar energy acceptance opening of the receiver. Slave cylinders are connected to the modulator plate for supporting the plate for axial displacement along the axis of the mirror, therby shading the opening with respect to solar energy flux reflected from the surface of the mirror to the solar energy acceptance opening.

Hale, R. R. (inventor); Mcdougal, A. R.

1984-01-01

240

Homogenization of a parabolic model of ferromagnetism  

NASA Astrophysics Data System (ADS)

This work deals with the homogenization of hysteresis-free processes in ferromagnetic composites. A degenerate, quasilinear, parabolic equation is derived by coupling the Maxwell-Ohm system without displacement current with a nonlinear constitutive law: {?B?}/{?t}+curl{A(x?)/?curlH?}=curlE, B????(H?,?). Here A is a periodic positive-definite matrix, ??(?,y) is maximal monotone and periodic in y, E is an applied field, and ?>0. An associated initial- and boundary-value problem is represented by a minimization principle via an idea of Fitzpatrick. As ??0 a two-scale problem is obtained via two-scale convergence, and an equivalent coarse-scale formulation is derived. This homogenization result is then retrieved via ?-convergence, and the continuity of the solution with respect to the operator ?? and the matrix A is also proved. This is then extended to some relaxation dynamics.

Visintin, Augusto

241

Nonuniform depth grids in parabolic equation solutions.  

PubMed

The parabolic wave equation is solved using a finite-difference solution in depth that involves a nonuniform grid. The depth operator is discretized using Galerkin's method with asymmetric hat functions. Examples are presented to illustrate that this approach can be used to improve efficiency for problems in ocean acoustics and seismo-acoustics. For shallow water problems, accuracy is sensitive to the precise placement of the ocean bottom interface. This issue is often addressed with the inefficient approach of using a fine grid spacing over all depth. Efficiency may be improved by using a relatively coarse grid with nonuniform sampling to precisely position the interface. Efficiency may also be improved by reducing the sampling in the sediment and in an absorbing layer that is used to truncate the computational domain. Nonuniform sampling may also be used to improve the implementation of a single-scattering approximation for sloping fluid-solid interfaces. PMID:23556565

Sanders, William M; Collins, Michael D

2013-04-01

242

Nuclear blast resistant parabolic antenna feed means  

SciTech Connect

The aftermath of a nuclear explosion generates a large amount of heat or infrared energy. When this heat is received by a parabolic reflector type antenna, the level of heat concentrated on the focal area of the feed is very intense. The present invention utilizes a highly heat conductive ceramic plug between the splash plate at the focal area of the feed and the waveguide so that heat can be readily conducted away from the splash plate and thereby minimize operational destruction of this splash plate due to thermal overload. The heat conductor material is a ceramic which is substantially transparent to RF signals being received by, or transmitted from the waveguide of the antenna system.

Dumas, T. A.; Buchmeyer, S. K.; Vet, M.

1985-03-19

243

Energy 101: Concentrating Solar Power  

ScienceCinema

From towers to dishes to linear mirrors to troughs, concentrating solar power (CSP) technologies reflect and collect solar heat to generate electricity. A single CSP plant can generate enough power for about 90,000 homes. This video explains what CSP is, how it works, and how systems like parabolic troughs produce renewable power. For more information on the Office of Energy Efficiency and Renewable Energy's CSP research, see the Solar Energy Technology Program's Concentrating Solar Power Web page at http://www1.eere.energy.gov/solar/csp_program.html.

244

Energy 101: Concentrating Solar Power  

ScienceCinema

From towers to dishes to linear mirrors to troughs, concentrating solar power (CSP) technologies reflect and collect solar heat to generate electricity. A single CSP plant can generate enough power for about 90,000 homes. This video explains what CSP is, how it works, and how systems like parabolic troughs produce renewable power. For more information on the Office of Energy Efficiency and Renewable Energy's CSP research, see the Solar Energy Technology Program's Concentrating Solar Power Web page at http://www1.eere.energy.gov/solar/csp_program.html.

None

2013-05-29

245

Comparison of Non-Parabolic Hydrodynamic Simulations for Semiconductor Devices  

NASA Technical Reports Server (NTRS)

Parabolic drift-diffusion simulators are common engineering level design tools for semiconductor devices. Hydrodynamic simulators, based on the parabolic band approximation, are becoming more prevalent as device dimensions shrink and energy transport effects begin to dominate device characteristic. However, band structure effects present in state-of-the-art devices necessitate relaxing the parabolic band approximation. This paper presents simulations of ballistic diodes, a benchmark device, of Si and GaAs using two different non-parabolic hydrodynamic formulations. The first formulation uses the Kane dispersion relationship in the derivation of the conservation equations. The second model uses a power law dispersion relation {(hk)(exp 2)/2m = xW(exp Y)}. Current-voltage relations show that for the ballistic diodes considered. the non-parabolic formulations predict less current than the parabolic case. Explanations of this will be provided by examination of velocity and energy profiles. At low bias, the simulations based on the Kane formulation predict greater current flow than the power law formulation. As the bias is increased this trend changes and the power law predicts greater current than the Kane formulation. It will be shown that the non-parabolicity and energy range of the hydrodynamic model based on the Kane dispersion relation are limited due to the binomial approximation which was utilized in the derivation.

Smith, A. W.; Brennan, K. F.

1996-01-01

246

Analysis of a solar total energy system  

Microsoft Academic Search

A solar system to provide the electrical, thermal, and hot water requirements of a hypothetical 1000-home community was analyzed. The community is located in Albuquerque, New Mexico, and real 1962 solar and weather data were used. The system is composed of parabolic cylindrical collectors, high and low temperature storage systems, a turbogenerator, cooling towers, auxiliary fossil fuel furnaces, a thermal

B. W. Marshall

1975-01-01

247

An Enhanced Parareal Algorithm for Partitioned Parabolic-Hyperbolic Coupling  

NASA Astrophysics Data System (ADS)

We present a parallel time-marching scheme for coupled parabolic-hyperbolic problems, as a prototype of fluid-structure interaction problems involving a linear structure and a viscous fluid. No linearity assumption is made on the parabolic side. The classical Parareal scheme is applied to the parabolic part, while the modified algorithm proposed by Farhat et al. [1] is applied to the hyperbolic part. This hybrid Parareal treatment relies on the partitioned formulation of the coupled propagator. Numerical evidence shows that the resulting scheme is stable for a wide range of physical and discretization parameters.

Chouly, Franz; Fernández, Miguel A.

2009-09-01

248

Propagation of rotating parabolic cylindrical beams in nonlocal nonlinear medium  

NASA Astrophysics Data System (ADS)

I introduce a class of rotating parabolic cylindrical beams in nonlocal nonlinear media. The rotating speed keeps fixed in the case of strong nonlocality and increases with the nonlocality being weak. For the strong nonlocal case, the analytical solutions of the modified Snyder Mitchell model agree well with the numerical simulations of the nonlocal nonlinear Schrödinger equation. By simulating the propagation of the rotating parabolic cylindrical beams in liquid crystal and nonlinear thermal media numerically, I demonstrate that there exists the rotating parabolic cylindrical cosine Gaussian quasi-soliton state.

Deng, Dongmei

2012-09-01

249

Gain-scheduled control of a solar power plant  

Microsoft Academic Search

The application of gain-scheduled control to a pilot-scale solar power plant is described. A field of parabolic collectors focus the solar radiation onto a tube where oil is pumped through in order to collect the solar power. The control problem is to keep the temperature of the oil leaving the field at its desired value by manipulating the oil pump

Tor A. Johansen; Kenneth J. Hunt; Idar Petersen

2000-01-01

250

Water Use in Parabolic Trough Power Plants: Summary Results from WorleyParsons' Analyses  

SciTech Connect

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.

Turchi, C. S.; Wagner, M. J.; Kutscher, C. F.

2010-12-01

251

Potential for using parabolic trough collectors to supplement power cycle boilers  

NASA Astrophysics Data System (ADS)

The advantage of such a system is that solar energy is used to heat the water in a steam Rankine cycle device up to the superheat regime, thus displacing the fossil fuel usually required. The temperature associated with this portion of the power cycle is typically on the order of 320 C or less, which makes it compatible with current parabolic trough collector systems. A system model which lends itself to optimization studies was constructed and exercised over a range of the multiparameter space involved. The collector field, storage, supplementary fossil boiler and superheater, and turbine/generator traded off to obtain a series of economically optimal systems for various years and solar fractions.

Schimmel, W. P., Jr.; Lukens, L. L.

1981-11-01

252

Two Dimensional Compound Parabolic Concentrating Collectors. Final Report.  

National Technical Information Service (NTIS)

Seven different compound parabolic concentrating (CPC) collector designs were tested by the ray trace method. The comparison of the collector was performed by simulating sunlight striking the designs at various angles of the sun during the course of the d...

J. P. Henry N. T. Gamble S. A. Cassidy

1983-01-01

253

Parabolized Navier-Stokes Equations without Sublayer Assumptions.  

National Technical Information Service (NTIS)

A new implicit, iteractive method of solving the Parabolized Navier-Stokes (PNS) Equations claims to overcome the elliptic character of the embedded subsonic sublayer by explicitly introducing pressure as an additional state variable. The Bhutta-Lewis app...

S. C. Pluntze

1987-01-01

254

Off-axis parabolic optical relays: almost perfect imaging  

NASA Astrophysics Data System (ADS)

Off-axis parabolic elements have found application in Tera-Hertz imaging and new application in two-photon microscopy scan engines. Both these applications demand spatial and temporal precision in photon location. This modelling work examines how close off-axis parabolic elements are to the perfect image relay by calculating the geometrical performance metrics of spot diagrams, point spread functions and wavefront distortion for different arrangements of off-axis parabolas and a parabolic torus when compared to a close-coupled two mirror scan engine. Results identify the off-axis parabolic elements as a superior scan engine particularly in wide-field scan instruments. When within the optimum beam size versus parabola focus length ratio, the imaging of these systems is superb.

Holdsworth, John L.; Sharafutdinova, Galiya; Sanderson, Michael J.; van Helden, Dirk F.

2011-08-01

255

He's variational iteration method for fourth-order parabolic equations  

Microsoft Academic Search

He’s variational iteration method is applied to fourth-order parabolic partial differential equations with variable coefficients. To illustrate the ability and reliability of the method, some examples are given, revealing its effectiveness and simplicity.

Jafar Biazar; H. Ghazvini

2007-01-01

256

On two parabolic systems: Convergence and blowup  

NASA Astrophysics Data System (ADS)

This dissertation studies two parabolic systems. It consists of two parts. In part one (chapter one), we prove a convergence result, namely, the solution (AK,/ BK) of a system of chemical diffusion-reaction equations (with reaction rate K) converges to the solution (A, B) of a diffusion- instantaneous-reaction equation. To prove our main result, we use some L1 and L2 'energy' estimates and a compactness result due to Aubin (1). As a by-product we also prove that as K approaches infinity, the limit solution exhibits phase separation between A and B. In part two (chapter two), we study the blowup rate for a system of heat equations ut=/Delta u,/ vt=/Delta v in a bounded domain ?times(0,T) coupled in the nonlinear Neumann boundary conditions [/partial u/over/partial n]=vp,/ [/partial v/over/partial n]=uq on ?Omega×[ 0,T), where p>0,/ q>0,/ pq>1 and n is the exterior normal vector on ?Omega. Under certain assumptions, we establish exact blowup rate which generalizes the corresponding results of some authors' recent work including Deng (2), Deng-Fila-Levine (3) and Hu-Yin (4). ftn (1) J. P. A scUBIN, Un theoreme de compacite, C. R. Acad. Sci., 256(1963), pp. 5042-5044. (2) K. D scENG, Blow-up rates for parabolic systems, Z. Angew. Math. Phys., 47(1996), No. 1, pp. 132-143. (3) K. D scENG, M. F scILA AND H. A. L scEVINE, On critical exponents for a system of heat equations coupled in the boundary conditions, Acta Math. Univ. Comenian. (N.S.), 36(1994), No. 2, pp. 169-192. (4) B. H scU scAND H. M. Y scIN, The profile near blowup time for solutions of the heat equation with a nonlinear boundary condition, Trans. Amer. Math. Soc., 346(1994), pp. 117-135.

Huang, Yamin

1998-12-01

257

On Pairs of Foliations of a Parabolic Cross-Cap  

Microsoft Academic Search

We study the asymptotic and characteristic curves in the neighbourhood of a parabolic cross-cap, that is, on a singular surface\\u000a with a cross-cap singularity with a parabolic set having a cusp singularity at the singular point. We obtain the topological\\u000a configurations of these foliations both in the domain of a parametrisation of such a surface, and on the surface itself.

J. M. Oliver; Springer Basel AG

2011-01-01

258

General theme report: Working session 2, solar thermal systems  

NASA Astrophysics Data System (ADS)

Currently, over 90 percent of the world's large-scale solar electric energy is generated with concentrating solar thermal power plants. Such plants have the potential to meet many of the world's future energy needs. Research efforts are generally focused on generating electricity, though a variety of other applications are being pursued. Today, the technology for using solar thermal energy is well developed, cost competitive, and in many cases, ready for widespread application. The current state of each of the solar thermal technologies and their applications is reviewed, and recommendations for increasing their use are presented. The technologies reviewed in detail are: parabolic trough systems, central tower systems, and parabolic dish systems.

Alpert, D. J.; Kolb, G. J.

1991-01-01

259

Effects of thermoplastic resin content of anisotropic conductive films on the pressure cooker test reliability of anisotropic conductive film flip-chip assembly  

NASA Astrophysics Data System (ADS)

The flip-chip technology using anisotropic conductive films (ACFs) is gaining growing interest due to its technical advantages such as environmentally friendly, simpler, and lower cost processes. Electrical performances and reliability of ACF flip-chip assembly depend on thermomechanical properties of ACF polymer resins. In this paper, the changes in ACF resin morphology due to the phase separation of thermoplastics, and subsequent changes of physical and mechanical properties were investigated as a function of thermoplastic contents of ACF formulation. Furthermore, the pressure cooker test (PCT) reliability of ACF flip-chip assemblies with various thermoplastic contents was also investigated. As thermoplastic contents increased, coefficient of thermal expansion (CTE) of ACFs increased, and elastic modulus (E?) of ACFs decreased. In contrast, water absorption rate decreased as thermoplastic content increased. As a result, PCT reliability of ACF flip-chip assembly was improved adding up to 50 wt.% content of thermoplastic.

Hwang, J. W.; Yim, M. J.; Paik, K. W.

2005-11-01

260

Lightweight, low-cost solar energy collector  

NASA Technical Reports Server (NTRS)

A lightweight solar concentrator of the reflecting parabolic or trough type is realized via a thin reflecting film, an inflatable structural housing and tensioned fibers. The reflector element itself is a thin, flexible, specularly-reflecting sheet or film. The film is maintained in the parabolic trough shape by means of a plurality of identical tensioned fibers arranged to be parallel to the longitudinal axis of the parabola. Fiber ends are terminated in two identical spaced anchorplates, each containing a plurality of holes which lie on the desired parabolic contour. In a preferred embodiment, these fibers are arrayed in pairs with one fiber contacting the front side of the reflecting film and the other contacting the back side of the reflecting film. The reflective surface is thereby slidably captured between arrays of fibers which control the shape and position of the reflective film. Gas pressure in the inflatable housing generates fiber tension to achieve a truer parabolic shape.

Hochberg, Eric B. (Inventor); Costen, Michael K. (Inventor)

2006-01-01

261

Solar thermionic power systems for terrestrial applications  

Microsoft Academic Search

The results of a feasibility study which showed that a low-temperature, high-efficient thermionic power system can efficiently convert solar energy to electrical energy without heat transport, as required by most solar thermal systems are described. A 3-dimensional (2-axis tracking) 93 sq m parabolic solar concentrator, consisting of mirrors on a foam glass substrate and designed to a concentration ratio (mirror

K. Shimada; M. Swerdling

1977-01-01

262

Effect of misalignment on the performance of a compound parabolic concentrator  

NASA Astrophysics Data System (ADS)

The recent push for cost reductions in solar electricity production deployment has renewed interest in concentrating photovoltaic systems. One strategy in low-concentration systems has been to reduce balance-of-system costs by reducing tracking accuracy requirements and/or eliminating tracking in the azimuth or altitude direction. However, misalignment with the sun, due to a lower-performing tracker or intentional design, hurts the concentrator's performance. The effect of misalignment on the performance of a 8.1x compound parabolic concentrator developed for inclined single-axis tracking is evaluated. Both the ray tracing simulations and measured compound parabolic concentrator results show significant effects from misalignment on the concentrator's performance. Average irradiance decreases significantly as the acceptance angle is approached in the east-west or north-south direction. Additionally, the maximum irradiance value can increase significantly during misalignment and move locations within the exit aperture, having a significant impact on thermal management design. It is important to incorporate these "real world" effects of intentional and unintentional error in sun-tracking, so that the product design is effective and the true cost of less accurate trackers is understood.

Shell, Kara A.; Hollingshead, Dave A.; Schuetz, Mark A.; Reinbolt, Greg S.

2012-01-01

263

Wind loads on heliostats and parabolic dish collectors: Final subcontractor report  

SciTech Connect

A major intent of this study was to define wind load reduction factors for parabolic dish solar collectors within a field protected by upwind collectors, wind protective fences, or other blockages. This information will help researchers improve the economy of parabolic collector support structures and drive mechanisms. The method used in the study was to generalize wind load data obtained during tests on model collectors placed in a modeled atmospheric wind in a boundary-layer wind tunnel. A second objective of the study was to confirm and document a sensitivity in load to level of turbulence, or gustiness, in the approaching wind. A key finding was that wind-load reduction factors for forces (horizontal and vertical) were roughly similar to those for flat heliostats, with some forces significantly less than those for flat shapes. However, load reductions for moments showed a smaller load reduction, particularly for the azimuth moment. The lack of load reduction could be attributed to collector shape, but specific flow features responsible for and methods to induce a load reduction were not explored. 62 figs., 13 tabs.

Peterka, J.A.; Tan, Z.; Bienkiewicz, B.; Cermak, J.E.

1988-11-01

264

Improved Wrede Stand-Alone ORC (Organic Rankine-Cycle) Solar Water Pump with Tracking Concentrators.  

National Technical Information Service (NTIS)

This paper describes the Wrede organic Rankine-cycle solar water pump employing tracking parabolic troughs. System principles and improvements introduced with the fifth-generation pump-unit and the concentrators are briefly discussed. Previous field tests...

P. D. Lund T. C. W. Wrede

1984-01-01

265

Design and thermal analysis of a two stage solar concentrator for combined heat and thermoelectric power generation  

Microsoft Academic Search

A design procedure and thermal performance analysis of a two stage solar energy concentrator suited to combined heat and thermoelectric power generation are presented. The concentrator is comprised of a primary one axis parabolic trough concentrator and a second stage compound parabolic concentrator mounted at the focus of the primary. The thermoelectric device is attached to the absorber plate at

Siddig A. Omer; David G. Infield

2000-01-01

266

A criterion of applicability of the parabolic heat conduction equation  

NASA Astrophysics Data System (ADS)

A criterion ( K MCV) of applicability of the parabolic heat conduction equation to isotropic materials is proposed that quantitatively determines the conditional boundary between linear and nonlinear regimes of nonequilibrium thermodynamics in the one-dimensional formulation of some heat transfer problems. The criterion is related to the heat flux relaxation time ?r. Once this characteristic time is known, the condition K MCV = 0 implies validity of the parabolic heat conduction equation. If ?r is unknown, the adequacy of the parabolic heat conduction model can be judged from the absence of a temporal variation of the K MCV/?r ratio under the main condition that the heat source power is independent of the time.

Kostanovskiy, A. V.; Kostanovskaya, M. E.

2008-06-01

267

Extension of Euler’s method to parabolic equations  

NASA Astrophysics Data System (ADS)

Euler generalized d'Alembert's solution to a wide class of linear hyperbolic equations with two independent variables. He introduced in 1769 the quantities that were rediscovered by Laplace in 1773 and became known as the Laplace invariants. The present paper is devoted to an extension of Euler's method to linear parabolic equations with two independent variables. The new method allows one to derive an explicit formula for the general solution of a wide class of parabolic equations. In particular, the general solution of the Black-Scholes equation is obtained.

Ibragimov, N. H.

2009-04-01

268

A comparison of prototype compound parabolic collector-reactors (CPC) on the road to SOLARDETOX technology.  

PubMed

Solar photocatalytic detoxification of non-biodegradable chlorinated hydrocarbon solvents (NBCS) is carried out in different concentrating and non concentrating devices using TiO2 as a photocatalyst fixed on the inner surface of the reaction tubes or as a slurry catalyst which has to be removed from the treated water. The reaction is most effective using 200 mg/l of TiO2 as a slurry in a non concentrating CPC reactor. The concentrating parabolic trough reactor has a poor activity because of its minor irradiated reactor surface. Catalyst coated glass tubes are less efficient then the used slurry catalyst. Their advantage is that no catalyst has not to be removed from the treated water and there is no loss of activity during treatment. Yet their physical stability is not sufficient to be competitive to the slurry catalyst. Nevertheless the degradation results are very promising and will possibly lead to commercial applications of this technology. PMID:11695470

Funken, K H; Sattler, C; Milow, B; De Oliveira, L; Blanco, J; Fernández, P; Malato, S; Brunott, M; Dischinge, N; Tratzky, S; Musci, M; de Oliveira, J C

2001-01-01

269

Operational experience from solar thermal energy projects  

NASA Astrophysics Data System (ADS)

Over the past few years, Sandia National Laboratories were involved in the design, construction, and operation of a number of DOE-sponsored solar thermal energy systems. Among the systems currently in operation are several industrial process heat projects and the Modular Industrial Solar Retrofit qualification test systems, all of which use parabolic troughs, and the Shenandoah Total Energy Project, which uses parabolic dishes. Operational experience has provided insight to both desirable and undesirable features of the designs of these systems. Features of these systems which are also relevant to the design of parabolic concentrator thermal electric systems are discussed. Other design features discussed are system control functions which were found to be especially convenient or effective, such as local concentrator controls, rainwash controls, and system response to changing isolation. Drive systems are also discussed with particular emphasis of the need for reliability and the usefulness of a manual drive capability.

Cameron, C. P.

1984-03-01

270

Research Applied to Solar-Thermal Power Systems.  

National Technical Information Service (NTIS)

The function of a solar-thermal power system is to supply solar-generated heat to the turbines of an electric power plant. The basic system presently being considered under this program is composed of an array of collectors (consisting of a parabolic refl...

W. B. Bienert E. R. G. Eckert J. M. Hammer R. C. Jordan J. W. Ramsey

1973-01-01

271

Hydrodynamic analysis of direct steam generation solar collectors  

Microsoft Academic Search

Direct steam generation collectors are considered with the aim to improve the performance of a parabolic trough collector leading to a reduction of operating costs of solar electric generation systems. In this study a hydrodynamic steady state model is developed and linked with a thermal model to optimize the performance of once-through direct steam generation solar collectors. The hydrodynamic model

S. D. Odeh; M. Behnia; G. L. Morrison

2000-01-01

272

Receiver\\/reactor concepts for thermochemical transport of solar energy  

Microsoft Academic Search

Thermochemical transport of solar energy based on reversible chemical reactions may be a way to take advantage of the high-temperature capabilities of parabolic dishes, while minimizing pipe network heat loss, since energy is transported at ambient temperatures in chemical form. Receiver\\/Reactor design is a key to making thermochemical transport a reality. In this paper the important parameters for solar receiver

Diver

1986-01-01

273

Solar energy satellites and satellites for energy transmission  

Microsoft Academic Search

The possibility of using large geosynchronous satellite platforms for the collection of solar energy to be transmitted in the form of microwaves to earth antennas is examined in terms of available and predictable advances in technology, and in terms of cost. Three basic design concepts are presented: thermoelectric, whereby a large parabolic reflector concentrates solar energy onto an absorber for

H. Hartbaum

1978-01-01

274

Receiver\\/reactor concepts for thermochemical transport of solar energy  

Microsoft Academic Search

Thermochemical transport of solar energy based on reversible chemical reactions may be a way to take advantage of the high-temperature capabilities of parabolic dishes, while minimizing pipe network heat loss, since energy is transported at ambient temperatures in chemical form. Receiver\\/Reactor design is a key to making thermochemical transport a reality. In this paper the important parameters for solar receiver

Diver

1987-01-01

275

Exergetic analysis of a solar thermal power system  

Microsoft Academic Search

This communication presents a second law analysis based on an exergy concept for a solar thermal power system. Basic energy and exergy analysis for the system components (viz. parabolic trough collector\\/receiver and Rankine heat engine, etc.) are carried out for evaluating the respective losses as well as exergetic efficiency for typical solar thermal power systems under given operating conditions. It

Narendra Singh; S. C. Kaushik; R. D. Misra

2000-01-01

276

Collective Modes and Optical Absorption in Parabolic Quantum Wells and Quantum Dots  

Microsoft Academic Search

Parabolic confinement arises in semiconductor microstructures by design, as in parabolic quantum wells, or as a by-product of the fabrication process, as in quantum -dot and quantum-wire systems. We use a variety of techniques to study collective modes and far-infrared optical absorption in parabolic quantum wells and quantum dots. For a model array of Coulombically-coupled parabolic quantum dots, we use

Jed Dempsey

1991-01-01

277

Performance of a direct steam generation solar thermal power plant for electricity production as a function of the solar multiple  

Microsoft Academic Search

This paper describes the influence of the solar multiple on the annual performance of parabolic trough solar thermal power plants with direct steam generation (DSG). The reference system selected is a 50MWe DSG power plant, with thermal storage and auxiliary natural gas-fired boiler. It is considered that both systems are necessary for an optimum coupling to the electricity grid. Although

M. J. Montes; A. Abánades; J. M. Martínez-Val

2009-01-01

278

One-axis tracking optimization of Concentrating Solar Power plant for electricity production  

Microsoft Academic Search

Among available technologies for energy production from solar source, Concentrating Solar Power could give a significant contribution to develop a more sustainable energy system. This work is aimed to investigate a Concentrating Solar-Trough plant, having nominal power equal to 100 kWe and exploiting linear parabolic collectors, to generate electric energy by means of Organic Rankine Cycle Turbine. In particular, a

Maria Dicorato; Giuseppe Forte; Mariagiovanna Pisani; Enrico De Tuglie

2010-01-01

279

Spherical harmonics approach to parabolic partial differential equations  

NASA Astrophysics Data System (ADS)

This paper is devoted to extend the spherical harmonics technique to the solution of parabolic differential equations and to integro-differential equations. The heat equation and the Black-Scholes equation are solved by using the method of spherical harmonics.

SenGupta, Indranil; Mariani, Maria C.

2012-12-01

280

Long-term average performance benefits of parabolic trough improvements  

SciTech Connect

Improved parabolic trough concentrating collectors will result from better design, improved fabrication techniques, and the development and utilization of improved materials. The difficulty of achieving these improvements varies as does their potential for increasing parabolic trough performance. The purpose of this analysis is to quantify the relative merit of various technology advancements in improving the long-term average performance of parabolic trough concentrating collectors. The performance benefits of improvements are determined as a function of operating temperature for north-south, east-west, and polar mounted parabolic troughs. The results are presented graphically to allow a quick determination of the performance merits of particular improvements. Substantial annual energy gains are shown to be attainable. Of the improvements evaluated, the development of stable back-silvered glass reflective surfaces offers the largest performance gain for operating temperatures below 150/sup 0/C. Above 150/sup 0/C, the development of trough receivers that can maintain a vacuum is the most significant potential improvement. The reduction of concentrator slope errors also has a substantial performance benefit at high operating temperatures.

Gee, R.; Gaul, H.W.; Kearney, D.; Rabl, A.

1980-03-01

281

Mixed finite element formulation for the solution of parabolic problems  

Microsoft Academic Search

A mixed formulation of the finite element method is used to establish a higher-order incremental method for the solution of parabolic equations. The displacement and velocity fields (in the terminology of Solid Mechanics) are approximated independently in time using a hierarchical, adaptive basis. Three time bases are tested, namely polynomial, radial and wavelet bases. The time approximation criterion ensures stability

J. A. Teixeira de Freitas

2002-01-01

282

PE Workshop II. Proceedings of the Second Parabolic Equation Workshop.  

National Technical Information Service (NTIS)

Perhaps the most important and encouraging results of this PE Workshop were that underwater acoustic parabolic equation (PE) models from both the 6.1 basic research modeling community and the 6.3 Navy operational modeling community were applied to the sam...

D. B. King J. A. Davis R. B. Evans S. A. Chin-Bing

1993-01-01

283

An Application of Calculus: Optimum Parabolic Path Problem  

ERIC Educational Resources Information Center

A practical and technological application of calculus problem is posed to motivate freshman students or junior high school students. A variable coefficient of friction is used in modelling air friction. The case in which the coefficient of friction is a decreasing function of altitude is considered. The optimum parabolic path for a flying object…

Atasever, Merve; Pakdemirli, Mehmet; Yurtsever, Hasan Ali

2009-01-01

284

The dynamics of parabolic flight: flight characteristics and passenger percepts  

PubMed Central

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 seconds of freefall (0 g) followed by 40 seconds 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.

Karmali, Faisal; Shelhamer, Mark

2008-01-01

285

Zero dynamics modeling and boundary feedback design for parabolic systems  

Microsoft Academic Search

In this work the authors introduce a notion of zero dynamics for distributed parameter systems governed by linear parabolic equations on bounded domains with controls implemented through first order linear boundary conditions. The idea of zero dynamics presented here is motivated by classical root-locus constructs from finite dimensional linear systems theory. In particular for a scalar proportional output feedback trajectories

Christopher I. Byrnes; David S. Gilliam; A. Isidori; Victor I. Shubov

2006-01-01

286

A Stability Analysis for a Semilinear Parabolic Partial Differential Equation.  

National Technical Information Service (NTIS)

The parabolic partial differential equation considered is u sub t = u sub xx + f(u), where minus infinity ch76 x plus infinity and o ch76 t ch76 plus infinity. Under suitable hypotheses pertaining to f, a class of initial data is exhibited: phi(x), minus ...

N. Chafee

1973-01-01

287

Restrictive padé approximation and parabolic partial differential equations  

Microsoft Academic Search

In this paper, we use the restrictive Pade approximation to approximate the exponential matrix exp(rA). The advantage is that it has the exact value at certain r. We define a new accurate, fast implicit method for the finite difference solution of a parabolic partial differential equations. The stability region is discussed, the obtained results are compared with the exact solution

Hassan N. A. Ismail; Elsayed M. E. Elbarbary

1998-01-01

288

Constrained Parabolic Approximation of Curves in the Finite Element Method.  

National Technical Information Service (NTIS)

In the construction of plane finite elements, curved boundary segments may be approximated by parabolic arcs that pass through the end points of each segment. The two remaining free parameters of the parabola may then be used to optimize the fit while sat...

M. L. Baart R. J. Y. Mcleod

1983-01-01

289

Numerical and asymptotic aspects of parabolic cylinder functions  

Microsoft Academic Search

Several 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 results are modified to improve the asymptotic properties and to enlarge the intervals for using the expansions in

Nico M. Temme

2000-01-01

290

Numerical and Asymptotic Aspects of Parabolic Cylinder Functions  

Microsoft Academic Search

Several 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 results are modified to improve the asymptotic properties and to enlarge the intervals for using the expansions in

Nico M. Temme

2001-01-01

291

Orthostatic Intolerance and Motion Sickness After Parabolic Flight  

NASA Technical Reports Server (NTRS)

Orthostatic intolerance is common in astronauts after prolonged space flight. However, the "push-pull effect" in military aviators suggests that brief exposures to transitions between hypo- and hypergravity are sufficient to induce untoward autonomic cardiovascular physiology in susceptible individuals. We therefore investigated orthostatic tolerance and autonomic cardiovascular function in 16 healthy test subjects before and after a seated 2-hr parabolic flight. At the same time, we also investigated relationships between parabolic flight-induced vomiting and changes in orthostatic and autonomic cardiovascular function. After parabolic flight, 8 of 16 subjects could not tolerate a 30-min upright tilt test, compared to 2 of 16 before flight. Whereas new intolerance in non-Vomiters resembled the clinical postural tachycardia syndrome (POTS), new intolerance in Vomiters was characterized by comparatively isolated upright hypocapnia and cerebral vasoconstriction. As a group, Vomiters also had evidence for increased postflight fluctuations in efferent vagal-cardiac nerve traffic occurring independently of any superimposed change in respiration. Results suggest that syndromes of orthostatic intolerance resembling those occurring after space flight can occur after a brief (i.e., 2-hr) parabolic flight.

Schlegel, Todd T.; Brown, Troy E.; Wood, Scott J.; Benavides, Edgar W.; Bondar, Roberta L.; Stein, Flo; Moradshahi, Peyman; Harm, Deborah L.; Low, Phillip A.

1999-01-01

292

Modeling of Coulomb interaction in parabolic quantum wires  

Microsoft Academic Search

We study the exciton states in a parabolic quantum wire. An exactly solvable model is introduced for calculating the exciton state and the binding energy as a function of the radius of the quantum wire within the envelope-function approximation. In the calculation, we replace the actual Coulomb interaction between the electron and the hole by a Gaussian nonlocal separable potential

C. González-Santander; F. Domínguez-Adame

2009-01-01

293

A three-dimensional parabolic punch problem in linear elasticity  

Microsoft Academic Search

In this paper an analytic solution for a three-dimensional contact problem, in linear elasticity, is constructed through the separation of Laplace's equation in paraboloidal coordinates. A rigid punch under normal loading is applied to an isotropic elastic medium occupying an infinite half-space where the contact region is parabolic and the punch profile is prescribed. This treatment allows for a general

A. Darai; F. M. Arscott

1990-01-01

294

Magnetoplasma excitations in parabolic quantum wells: Hydrodynamic model  

Microsoft Academic Search

We employ a classical hydrodynamic model to study the magnetoplasma excitations of a slab of electron fluid confined in one direction by a parabolic potential, in a tilted magnetic field. The electron gas is treated as a classical charge fluid with an internal pressure p~(n-nc), when n is the number density of electrons and nc is a density at which

Jed Dempsey; B. I. Halperin

1992-01-01

295

Dissection of a model for neuronal parabolic bursting  

Microsoft Academic Search

We have obtained new insight into the mechanisms for bursting in a class of theoretical models. We study Plant's model [24] for Aplysia R-15 to illustrate our view of these so-called “parabolic” bursters, which are characterized by low spike frequency at the beginning and end of a burst. By identifying and analyzing the fast and slow processes we show how

John Rinzel; Young Seek Lee

1987-01-01

296

Orthostatic intolerance and motion sickness after parabolic flight  

NASA Technical Reports Server (NTRS)

Because it is not clear that the induction of orthostatic intolerance in returning astronauts always requires prolonged exposure to microgravity, we investigated orthostatic tolerance and autonomic cardiovascular function in 16 healthy subjects before and after the brief micro- and hypergravity of parabolic flight. Concomitantly, we investigated the effect of parabolic flight-induced vomiting on orthostatic tolerance, R-wave-R-wave interval and arterial pressure power spectra, and carotid-cardiac baroreflex and Valsalva responses. After parabolic flight 1) 8 of 16 subjects could not tolerate 30 min of upright tilt (compared to 2 of 16 before flight); 2) 6 of 16 subjects vomited; 3) new intolerance to upright tilt was associated with exaggerated falls in total peripheral resistance, whereas vomiting was associated with increased R-wave-R-wave interval variability and carotid-cardiac baroreflex responsiveness; and 4) the proximate mode of new orthostatic failure differed in subjects who did and did not vomit, with vomiters experiencing comparatively isolated upright hypocapnia and cerebral vasoconstriction and nonvomiters experiencing signs and symptoms reminiscent of the clinical postural tachycardia syndrome. Results suggest, first, that syndromes of orthostatic intolerance resembling those developing after space flight can develop after a brief (i.e., 2-h) parabolic flight and, second, that recent vomiting can influence the results of tests of autonomic cardiovascular function commonly utilized in returning astronauts.

Schlegel, T. T.; Brown, T. E.; Wood, S. J.; Benavides, E. W.; Bondar, R. L.; Stein, F.; Moradshahi, P.; Harm, D. L.; Fritsch-Yelle, J. M.; Low, P. A.

2001-01-01

297

Numerical simulation of shock wave focusing over parabolic reflectors  

Microsoft Academic Search

The problem of a plane shock wave that propagates in an air media and then is reflected from a parabolic concave reflector and focuses at some region is considered. The shock focusing can greatly magnify the pressure and the temperature. The purpose of this study is to numerically simulate the shock focusing process of the reflection of shock waves from

S. M. Liang; C. S. Wu; F. M. Yu; L. N. Wu

1995-01-01

298

VHF parabolic cylinder antenna for incoherent scatter radar research  

Microsoft Academic Search

A parabolic cylnider reflector antenna has been designed for high-power radar observations of signals scattered from the ionospheric plasma at a frequency of 224 MHz. The antenna is constructed with an offset feed system to reduce aperture blockage. Efficient illumination for circular polarization using crossed dipoles is achieved by means of primary beam forming, which amounts to the construction of

T. Hagfors; P. S. Kildal; H. J. Kaercher; B. Liesenkoetter; G. Schroeer

1982-01-01

299

Approximate solutions of delay parabolic equations with the Neumann condition  

NASA Astrophysics Data System (ADS)

An approximate solution of the initial-boundary value problem for the delay parabolic partial differential equation is considered. Stable difference schemes of first and second orders of accuracy for this problem are investigated. Convergence estimates for the solution of these difference schemes in Hölder norms are established. Theoretical statements are supported by numerical examples.

Ashyralyev, Allaberen; A??rseven, Deniz

2012-09-01

300

Acurex Parabolic Dish Concentrator (PDC-2)  

SciTech Connect

The design approach, rationale for the selected configuration, and the development status of a cost effective point-focus solar concentrator are discussed. The low-cost concentrator reflective surface design is based on the use of a thin, backsilvered mirror glass reflector bonded to a molded structural plastic substrate. The foundation, support, and drive subassembles are described. A hybrid, two-axis, Sun tracking control system based on microprocessor technology was selected. Coarse synthetic tracking is achieved through a microcomputer-based control system to calculate Sun position for transient periods of cloud cover as well as sundown and sunrise positioning. Accurate active tracking is achieved by two-axis optical sensors. Results of the reflective panel demonstration tests investigating slope error, hail impact survivability, temperature/humidity cycling, longitudinal strength/bending stiffness, and torsional stiffness are discussed.

Overly, P.; Bedard, R.

1982-07-01

301

IR Spectrometer Using 90-Degree Off-Axis Parabolic Mirrors  

SciTech Connect

A gated spectrometer has been designed for real-time, pulsed infrared (IR) studies at the National Synchrotron Light Source 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 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 single-point pyrometry, which provides continuous time histories of a small collection of spots from shock-heated targets.

Robert M. Malone, Ian J. McKenna

2008-03-01

302

IR Spectrometer Using 90-degree Off-axis Parabolic Mirrors  

SciTech Connect

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.

Robert M. Malone, Richard, G. Hacking, Ian J. McKenna, and Daniel H. Dolan

2008-09-02

303

Method of installing a solar collector  

SciTech Connect

An extended width parabolic trough solar collector is supported from pylons. Collector is formed from a center module and two wing modules joined together along abutting edges by connecting means. A stressed skin monocoque construction is used for each of the modules.

Hutchison, J.A.

1982-09-14

304

Method of manufacturing solar collector module  

SciTech Connect

An extended width parabolic trough solar collector is supported from pylons. Collector is formed from a center module and two wing modules joined together along abutting edges by connecting means. A stressed skin monocoque construction is used for each of the modules.

Hutchison, J.A.

1982-09-14

305

Semiconductor liquid-junction solar cell  

DOEpatents

A semiconductor liquid junction photocell in which the photocell is in the configuration of a light concentrator and in which the electrolytic solution both conducts current and facilitates the concentration of incident solar radiation onto the semiconductor. The photocell may be in the configuration of a non-imaging concentrator such as a compound parabolic concentrator, or an imaging concentrator such as a lens.

Parkinson, B.A.

1982-10-29

306

Solar sorption refrigerator using a CPC collector  

Microsoft Academic Search

A prototype Compound Parabolic Concentrating (CPC) solar energy collector for a sorption refrigerator is presented. It consists of two CPC reflectors, two absorbers and a single glazing cover. The absorber is made with seamless steel tube covered in a selective surface (absorptance: 0.95) and contains aluminium fins, activated carbon and ammonia. The parabolas are manufactured from aluminium foil and a

Z. Tamainot-Telto; R. E. Critoph

1999-01-01

307

Focus Control System for Solar Thermal Propulsion.  

National Technical Information Service (NTIS)

Solar thermal propulsion (STP) uses a parabolic concentrator like a large magnifying glass to focus the sun's energy and heat a working fluid such as hydrogen to very high temperatures (3,000 K). The hydrogen is then expelled through a nozzle to produce t...

S. R. Wassom

2000-01-01

308

Shenandoah Solar Total-Energy Project  

NASA Astrophysics Data System (ADS)

The design and construction of the world's first solar total energy plant in the private sector was completed and checkout is underway. During its operational phase, the solar plant will furnish electrical power, process steam, and other thermal energy to a nearby knitwear factory. The solar system consists of a collector field containing 114 parabolic dish collectors which supply thermal energy at 4000 C to drive a 400 kW multistage Rankine cycle turbine generator. Some steam is extracted from the turbine and supplied to the knitwear manufacturing processes. The system will be grid connected. Presented are a description of the system and components being installed; a summary of performance testing of the extraction turbine and of four prototype parabolic dish collectors; and a discussion of design considerations and insights which have general applicability to solar thermal system designs.

Leonard, J. A.; Hunke, R. W.

1982-12-01

309

Line-focus solar thermal energy technology development. FY 79 annual report for Department 4720  

SciTech Connect

The primary role of the Solar Energy Projects Department II (4720) is the development, evaluation, and testing of line-focus solar thermal technology. This report of FY 79 progress and accomplishments is divided into two parts: (1) Component and Subsystem Development including the design and analysis of collector modules, their components, and associated materials and processes, and (2) Systems and Applications Development, involving larger configurations of solar thermal line-focus systems. The emphasis is on parabolic troughs, but significant efforts on hemispherical bowls, compound parabolic collectors, and dishes for the Solar Total Energy Project are also described.

Bergeron, K D; Champion, R L; Hunke, R W [eds.

1980-04-01

310

Line-focus solar thermal energy technology development. Report for Department 4720  

NASA Astrophysics Data System (ADS)

The primary role of the Solar Energy Projects Department 2 is the development, evaluation, and testing of lime focus solar thermal technology. This report is divided into two parts: (1) component and subsystem development including the design and analysis of collector modules, their components, and associated materials and processes; and (2) systems and applications development, involving larger configurations of solar thermal line focus systems. The emphasis is on parabolic troughs, but significant efforts on hemispherical bowls, compound parabolic collectors, and dishes for the Solar Total Energy Project are also described.

Bergeron, K. D.; Champion, R. L.; Hunke, R. W.

1980-04-01

311

Build an oven, cook a meal: How solar energy empowered women in Costa Rica  

SciTech Connect

A pilot solar cooking project in the hot, northern province of Guanacaste promises to serve as a model for community groups wanting to build their own solar ovens. An $8,000 (US) grant has been awarded by the Canadian Embassy in Costa Rica to take the Guanacaste project into a second stage in 1990-91. Two construction workshops, with twelve participants in each, are planned in communities near Oriente. Three women from the Oriente group will have paid jobs as organizational facilitators and workshop supervisors. In popular education this is called the multiplier effect - the users of solar cookers construct the ovens themselves, and then instruct others to do the same. 3 refs.

Blankenship, J. (Canadian Univ. Service Organization, San Jose (Costa Rica))

1990-12-01

312

Electromagnetic Casimir forces of parabolic cylinder and knife-edge geometries  

SciTech Connect

An exact calculation of electromagnetic scattering from a perfectly conducting parabolic cylinder is employed to compute Casimir forces in several configurations. These include interactions between a parabolic cylinder and a plane, two parabolic cylinders, and a parabolic cylinder and an ordinary cylinder. To elucidate the effect of boundaries, special attention is focused on the 'knife-edge' limit in which the parabolic cylinder becomes a half-plane. Geometrical effects are illustrated by considering arbitrary rotations of a parabolic cylinder around its focal axis, and arbitrary translations perpendicular to this axis. A quite different geometrical arrangement is explored for the case of an ordinary cylinder placed in the interior of a parabolic cylinder. All of these results extend simply to nonzero temperatures.

Graham, Noah [Department of Physics, Middlebury College, Middlebury, Vermont 05753 (United States); Shpunt, Alexander; Kardar, Mehran [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Emig, Thorsten [Laboratoire de Physique Theorique et Modeles Statistiques, CNRS UMR 8626, Bat. 100, Universite Paris-Sud, 91405 Orsay cedex (France); Rahi, Sahand Jamal [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Studies in Physics and Biology, The Rockefeller University, 1230 York Street, New York, New York 10065 (United States); Jaffe, Robert L. [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Theoretical Physics and Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2011-06-15

313

Environmental responses of solar reflective surfaces  

NASA Technical Reports Server (NTRS)

An assessment is undertaken of the environmental responses of solar reflective surfaces, with emphasis on dish-type concentrator surfaces exposed to the conditions of Southern California. A generalized mathematical model for specific solar reflective surfaces can be formulated on the basis of either experimental or assumed site degradation/corrosion data. In addition, the fabrication parameters of a parabolic reflecting surface and its substrate can be used to model combined reflective characteristics for the postulated environmental conditions.

Bouquet, F. L.

1983-01-01

314

Air Brayton Solar Receiver, phase 1  

NASA Technical Reports Server (NTRS)

A six month analysis and conceptual design study of an open cycle Air Brayton Solar Receiver (ABSR) for use on a tracking, parabolic solar concentrator are discussed. The ABSR, which includes a buffer storage system, is designed to provide inlet air to a power conversion unit. Parametric analyses, conceptual design, interface requirements, and production cost estimates are described. The design features were optimized to yield a zero maintenance, low cost, high efficiency concept that will provide a 30 year operational life.

Zimmerman, D. K.

1979-01-01

315

Optical measurements pertaining to Space Station solar dynamic power systems  

NASA Technical Reports Server (NTRS)

The Space Station solar dynamic power system is a hybrid of solar photovoltaic and solar dynamic systems, the latter of which uses a parabolic reflector to collect solar energy. This paper describes analytical results of an off-axis solar illumination on the intensity distribution in arbitrary target planes perpendicular to the axis of a parabolic reflector. Such computational capability would make it possible to predict optical intensity distributions resulting from off-axis angles of incident radiation on such target planes. To validate the computer code, experimental optical measurements were performed on the multifaceted paraboloidal collecor at the Solar Dynamic Test Facility at Rockedyne's Santa Susana Field Laboratory. The experimental data compared reasonably well with the calculated values.

Holly, S.; Springer, T.; Jefferies, K. S.

1987-01-01

316

All-fiber ring Raman laser generating parabolic pulses  

SciTech Connect

We present theoretical and numerical results for an all-fiber laser using self-similar parabolic pulses ('similaritons') designed to operate using self-similar propagation regimes. The similariton laser features a frequency filter and a Sagnac loop which operate together to generate an integrated all-fiber mode-locked laser. Numerical studies show that this laser generates parabolic pulses with linear chirp in good agreement with analytical predictions. The period for propagating similariton pulses in stable regimes can vary from one to two round trips for different laser parameters. Two-round-trip-period operation in the mode-locked laser appears at bifurcation points for certain cavity parameters. The stability of the similariton regimes has been confirmed by numerical simulations for large numbers of round trips.

Kruglov, V. I.; Mechin, D.; Harvey, J. D. [Physics Department, University of Auckland, Private Bag 92019, Auckland (New Zealand)

2010-02-15

317

Extremal solutions of quasilinear parabolic inclusions with generalized Clarke's gradient  

NASA Astrophysics Data System (ADS)

In this paper we consider an initial boundary value problem for a parabolic inclusion whose multivalued nonlinearity is characterized by Clarke's generalized gradient of some locally Lipschitz function, and whose elliptic operator may be a general quasilinear operator of Leray-Lions type. Recently, extremality results have been obtained in case that the governing multivalued term is of special structure such as, multifunctions given by the usual subdifferential of convex functions or subgradients of so-called dc-functions. The main goal of this paper is to prove the existence of extremal solutions within a sector of appropriately defined upper and lower solutions for quasilinear parabolic inclusions with general Clarke's gradient. The main tools used in the proof are abstract results on nonlinear evolution equations, regularization, comparison, truncation, and special test function techniques as well as tools from nonsmooth analysis.

Carl, S.; Motreanu, D.

318

Parabolic discounting of monetary rewards by physical effort.  

PubMed

When humans and other animals make decisions in their natural environments prospective rewards have to be weighed against costs. It is well established that increasing costs lead to devaluation or discounting of reward. While our knowledge about discount functions for time and probability costs is quite advanced, little is known about how physical effort discounts reward. In the present study we compared three different models in a binary choice task in which human participants had to squeeze a handgrip to earn monetary rewards: a linear, a hyperbolic, and a parabolic model. On the group as well as the individual level, the concave parabolic model explained most variance of the choice data, thus contrasting with the typical hyperbolic discounting of reward value by delay. Research on effort discounting is not only important to basic science but also holds the potential to quantify aberrant motivational states in neuropsychiatric disorders. PMID:24140077

Hartmann, Matthias N; Hager, Oliver M; Tobler, Philippe N; Kaiser, Stefan

2013-11-01

319

Treatment of motion sickness in parabolic flight with buccal scopolamine  

NASA Technical Reports Server (NTRS)

Treatment of acute motion sickness induced by parabolic flight with a preparation of scopolamine placed in the buccal pouch was investigated. Twenty-one subjects flew aboard a KC-135 aircraft operated by NASA which performed parabolic maneuvers resulting in periods of 0-g, 1-g, and 1.8-g. Each subject flew once with a tablet containing scopolamine and once with a placebo in a random order, crossover design. Signs and symptoms of motion sickness were systematically recorded during each parabola by an investigator who was blind to the content of the tablet. Compared with flights using placebo, flights with buccal scopolamine resulted in significantly lower scores for nausea (31-35 percent reduction) and vomiting (50 percent reduction in number of parabolas with vomiting). Side effects of the drug during flight were negligible. It is concluded that buccal scopolamine is more effective than a placebo in treating ongoing motion sickness.

Norfleet, William T.; Degioanni, Joseph J.; Reschke, Millard F.; Bungo, Michael W.; Kutyna, Frank A.; Homick, Jerry L.; Calkins, D. S.

1992-01-01

320

Development and testing of Parabolic Dish Concentrator No. 1  

NASA Technical Reports Server (NTRS)

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.

Dennison, E. W.; Thostesen, T. O.

1984-01-01

321

Optimal Continuous Dependence Estimates for Fractional Degenerate Parabolic Equations  

NASA Astrophysics Data System (ADS)

We derive continuous dependence estimates for weak entropy solutions of degenerate parabolic equations with nonlinear fractional diffusion. The diffusion term involves the fractional Laplace operator, {triangle^{?/2}} for {? in (0,2)} . Our results are quantitative and we exhibit an example for which they are optimal. We cover the dependence on the nonlinearities, and for the first time, the Lipschitz dependence on ? in the BV-framework. The former estimate (dependence on nonlinearity) is robust in the sense that it is stable in the limits {? downarrow 0} and {? \\uparrow 2} . In the limit {? \\uparrow 2} , {triangle^{?/2}} converges to the usual Laplacian, and we show rigorously that we recover the optimal continuous dependence result of Cockburn and Gripenberg (J Differ Equ 151(2):231-251, 1999) for local degenerate parabolic equations (thus providing an alternative proof).

Alibaud, Nathaël; Cifani, Simone; Jakobsen, Espen R.

2014-04-01

322

Solar Tests of Aperture Plate Materials for Solar Thermal Dish Collectors.  

National Technical Information Service (NTIS)

In parabolic dish solar collectors, walk-off of the spot of concentrated sunlight can be a hazard if a malfunction causes the concentration to stop following the sun. Therefore, a test program was carried out to evaluate the behavior of various ceramics, ...

L. D. Jaffe

1983-01-01

323

Proposed solar Rankine cycle system with phase change steam accumulator and CPC solar collector  

Microsoft Academic Search

An advanced solar thermal electric system with CPC (compound parabolic concentrator) collector and steam accumulator of phase-change type was newly proposed. The electricity generation efficiency of the proposed system using water vapor as the working fluid is estimated to be about 16 percent, which is about three times better than that of photovoltaic (PV) cell (about 67 percent) under a

Takeo S. SAITOH; Akira HOSHI

2002-01-01

324

Thermal distortion analysis of a deployable parabolic reflector  

NASA Technical Reports Server (NTRS)

A thermal distortion analysis of the ATS-6 Satellite parabolic reflector was performed using NASTRAN level 15.1. The same NASTRAN finite element method was used to conduct a one g static load analysis and a dynamic analysis of the reflector. In addition, a parametric study was made to determine which parameters had the greatest effect on the thermal distortions. The method used to model the construction of the reflector is described and the results of the analyses are presented.

Bruck, L. R.; Honeycutt, G. H.

1973-01-01

325

Stability Analysis of Difference Methods for Parabolic Initial Value Problems  

Microsoft Academic Search

A decomposition of the numerical solution can be defined by the normal mode representation, that generalizes further the spatial\\u000a eigenmode decomposition of the von Neumann analysis by taking into account the boundary conditions which are not periodic.\\u000a In this paper we present some new theoretical results on normal mode analysis for a linear and parabolic initial value problem.\\u000a Furthermore we

Erc ´ ilia Sousa

2006-01-01

326

Radiative Heat Transfer During Atmosphere Entry at Parabolic Velocity  

NASA Technical Reports Server (NTRS)

Stagnation point radiative heating rates for manned vehicles entering the earth's atmosphere at parabolic velocity are presented and compared with corresponding laminar convective heating rates. The calculations were made for both nonlifting and lifting entry trajectories for vehicles of varying nose radius, weight-to-area ratio, and drag. It is concluded from the results presented that radiative heating will be important for the entry conditions considered.

Yoshikawa, Kenneth K.; Wick, Bradford H.

1961-01-01

327

Real-time optical laboratory solution of parabolic differential equations  

NASA Technical Reports Server (NTRS)

An optical laboratory matrix-vector processor is used to solve parabolic differential equations (the transient diffusion equation with two space variables and time) by an explicit algorithm. This includes optical matrix-vector nonbase-2 encoded laboratory data, the combination of nonbase-2 and frequency-multiplexed data on such processors, a high-accuracy optical laboratory solution of a partial differential equation, new data partitioning techniques, and a discussion of a multiprocessor optical matrix-vector architecture.

Casasent, David; Jackson, James

1988-01-01

328

Receiver behavior in direct steam generation with parabolic troughs  

Microsoft Academic Search

The receiver behavior of parabolic troughs in direct steam generation (DSG) has been studied under different experimental conditions. When cool water was fed into steel receiver pipes (?=2.54cm), the pipes deflected. This bend advanced like a wave from the inlet to the outlet end, having a deflection of about 6.5cm at the center of each section (2.90m long) in the

Rafael Almanza; Alvaro Lentz; Gustavo Jiménez

1998-01-01

329

Synergies between optical and physical variables in intercepting parabolic targets  

PubMed Central

Interception requires precise estimation of time-to-contact (TTC) information. A long-standing view posits that all relevant information for extracting TTC is available in the angular variables, which result from the projection of distal objects onto the retina. The different timing models rooted in this tradition have consequently relied on combining visual angle and its rate of expansion in different ways with tau being the most well-known solution for TTC. The generalization of these models to timing parabolic trajectories is not straightforward. For example, these different combinations rely on isotropic expansion and usually assume first-order information only, neglecting acceleration. As a consequence no optical formulations have been put forward so far to specify TTC of parabolic targets with enough accuracy. It is only recently that context-dependent physical variables have been shown to play an important role in TTC estimation. Known physical size and gravity can adequately explain observed data of linear and free-falling trajectories, respectively. Yet, a full timing model for specifying parabolic TTC has remained elusive. We here derive two formulations that specify TTC for parabolic ball trajectories. The first specification extends previous models in which known size is combined with thresholding visual angle or its rate of expansion to the case of fly balls. To efficiently use this model, observers need to recover the 3D radial velocity component of the trajectory which conveys the isotropic expansion. The second one uses knowledge of size and gravity combined with ball visual angle and elevation angle. Taking into account the noise due to sensory measurements, we simulate the expected performance of these models in terms of accuracy and precision. While the model that combines expansion information and size knowledge is more efficient during the late trajectory, the second one is shown to be efficient along all the flight.

Gomez, Jose; Lopez-Moliner, Joan

2013-01-01

330

Blow-up in the Parabolic Scalar Curvature Equation  

Microsoft Academic Search

The \\\\textit{parabolic scalar curvature equation} is a reaction-diffusion type equation on an $(n-1)$-manifold $\\\\Sigma$, the time variable of which shall be denoted by $r$. Given a function $R$ on $[r_0,r_1)\\\\times\\\\Sigma$ and a family of metrics $\\\\gamma(r)$ on $\\\\Sigma$, when the coefficients of this equation are appropriately defined in terms of $\\\\gamma$ and $R$, positive solutions give metrics of prescribed scalar

Brian Smith

2007-01-01

331

Magnetoexcitons in quantum wires with an anisotropic parabolic potential  

Microsoft Academic Search

We study theoretically exciton properties of quantum wires (QWR's) with an anisotropic two-dimensional parabolic potential in a magnetic field. First, the analytical solution for the single-particle states of the QWR's in the magnetic field is obtained. Then, the energy states are analyzed numerically including the Coulomb interaction between an electron-hole pair. The results show that the experimental results on magnetophotoluminescence

Takuji Tanaka; Yasuhiko Arakawa; Gerrit W. E. Bauer

1994-01-01

332

Ground state description of bound polarons in parabolic quantum wires  

Microsoft Academic Search

:   The Feynman-Haken variational path integral theory is, for the first time, generalized to calculate the ground-state energy\\u000a of an electron coupled simultaneously to a Coulomb potential and to a longitudinal-optical (LO) phonon field in parabolic\\u000a quantum wires. It is shown that the polaronic correction to the ground-state energy is more sensitive to the electron-phonon\\u000a coupling constant than the Coulomb

Qinghu Chen; Yuhang Ren; Zhengkuan Jiao; Kelin Wang

1999-01-01

333

Few-anyon systems in a parabolic dot  

Microsoft Academic Search

The energy levels of two and three anyons in a two-dimensional parabolic quantum dot and a perpendicular magnetic field are computed as power series in 1\\/\\\\|J\\\\|, where J is the angular momentum. The particles interact repulsively through a Coulombic (1\\/r) potential. In the two-anyon problem, the reached accuracy is better than one part in 105. For three anyons, we study

Ricardo Perez; Augusto Gonzalez

1998-01-01

334

Nonrelativistic Coulomb Green’s function in parabolic coordinates  

Microsoft Academic Search

The nonrelativistic Coulomb Green’s function G(+)(r1,r2,k) is evaluated by explicit summation over discrete and continuum eigenstates in parabolic coordinates. This completes the derivation of Meixner, who was able to obtain only the r1=0 and r2?? limiting forms of the Green’s function. Further progress is made possible by an integral representation for a product of two Whittaker functions given by Buchholz.

S. M. Blinder

1981-01-01

335

Closed-form solutions for a noncentral parabolic potential  

Microsoft Academic Search

We have found closed-form solutions of the Schrödinger equation for a particle in a noncentral potential given by a two-body Coulomb potential plus a parabolic barrier. These kinds of potentials arise in the context of the three-body Coulomb continuum problem. Here we study the continuum and discrete spectrum eigenfunctions as well as their asymptotic behavior and the associated transition amplitudes.

G. Gasaneo; F. D. Colavecchia; W. R. Cravero; C. R. Garibotti

1999-01-01

336

Propagation modeling over terrain using the parabolic wave equation  

Microsoft Academic Search

We address the numerical solution of the parabolic wave equation over terrain using the Fourier\\/split-step approach. The method, referred to as a shift map, generalizes that of Beilis and Tappert (1979) who introduced a coordinate transformation technique to flatten the boundary. This technique is extended to a wide-angle form, allowing larger propagation angles with respect to the horizon. A new

Denis J. Donohue; J. R. Kuttler

2000-01-01

337

NONRADIAL SOLVABILITY STRUCTURE OF SUPER-DIFFUSIVE NONLINEAR PARABOLIC EQUATIONS  

Microsoft Academic Search

We study the solvability of the Cauchy problem for the nonlinear parabolic equation @u @t =d iv (u m 1ru) when m< 0i nR2 ,w ithu(x; 0) = f(x) a given nonnegative function. It is known from earlier works of the authors that the asymptotic radial growth r 2=1 m, r =jxj for the spherical averages of f(x )i s

PANAGIOTA DASKALOPOULOS; MANUEL DEL PINO

338

Electronic Raman scattering in double semi-parabolic quantum wells  

NASA Astrophysics Data System (ADS)

The differential cross-section for electronic Raman scattering in double semi-parabolic quantum wells of typical GaAs/AlxGa1-xAs is investigated numerically with the effective-mass approximation. The dependence of the differential cross-section on structural parameters such as the barrier width and the well widths is studied. Our results indicate that the electronic Raman scattering is affected by the geometrical size and can be negligible in the symmetric double-well case.

Zamani, N.; Keshavarz, A.; J. Karimi, M.

2013-05-01

339

Discontinuous Galerkin Finite Element Method for Parabolic Problems  

NASA Technical Reports Server (NTRS)

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.

Kaneko, Hideaki; Bey, Kim S.; Hou, Gene J. W.

2004-01-01

340

A polynomial based iterative method for linear parabolic equations  

Microsoft Academic Search

A new polynomial based method (PBM) is developed to integrate multi-dimensional linear parabolic initial-boundary-value problems. It is based on Lâ-approximations to f(z) = (1 - exp(-z))\\/z, f(0) = 1, over ellipses in the complex plane using expansions of f in Chebychev polynomials. The calculation of the Fourier coefficients requires numerical integration over only a single line segment in the complex

1987-01-01

341

Piecewise parabolic method (PPM) for gas-dynamical simulations  

Microsoft Academic Search

We present the piecewise parabolic method, a higher-order extension of of Godunov's method. There are several new features of this method which distinguish it from other higher-order Godunov-type methods. We use a higher-order spatial interpolation than previously used, which allows for a steeper representation of discontinuities, particularly contact discontinuities. We introduce a simpler and more robust algorithm for calculating the

P. Corlella; PAUL R. WOODWARD

1984-01-01

342

PARABOLIC EQUATIONS OVER THE FIELD OF p-ADIC NUMBERS  

NASA Astrophysics Data System (ADS)

The author constructs and investigates a fundamental solution of Cauchy's problem for a parabolic equation with a p-adic space variable and a real time variable. The question of existence and uniqueness of solutions to Cauchy's problem in classes of bounded and increasing functions is considered, and conditions for nonnegativity of the fundamental solution are found. The problem of determining if the solution stabilizes as t \\to \\infty is solved for a model equation with constant coefficients.

Kochube?, A. N.

1992-06-01

343

A stability analysis for a semilinear parabolic partial differential equation  

NASA Technical Reports Server (NTRS)

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.

Chafee, N.

1973-01-01

344

Concentrating Solar Power Program  

NSDL National Science Digital Library

This information resource related to renewable energy has recently been made available by the US Department of Energy. The Concentrating Solar Power Program is researching solar thermal technologies in order to provide future energy, economic, and environmental security for the US. This site provides an overview of the program, the program's strategic plan, and an analysis of the three technologies being researched: the power tower, dish/engine, and parabolic trough systems. Cost and performance analysis results for each technology are included (Adobe Acrobat [.pdf] format only). [Notes: Originally reviewed in conjunction with other resources. To read the full review, link to the archived Scout Report via the Date of Review above. Site formerly known as "Solar Thermal Electric Program (STEP)."

1997-01-01

345

Space-DRUMS™ experimental development using parabolic reduced gravity flights  

NASA Astrophysics Data System (ADS)

Space-DRUMS™ is a microgravity containerless-processing facility that uses acoustic beams to position large diameter liquid or solid samples within a gas-filled chamber. Its capacity to control the position of large diameter (6 cm) low density solid materials was successfully demonstrated on NASA's DC-9 parabolic aircraft in July 1996; two subsequent flights occurred in 1998 using the KC-135 and A-300 aircraft to further refine the technology used in the system. The working environment for the Space-DRUMS™ facility is the Space Shuttle/Space Station where long duration microgravity experimentation can take place. Since the reduced gravity environment of an A-300 or a KC-135 parabolic flight is much harsher than that of the Space Shuttle in terms of residual acceleration magnitudes experienced by the samples to be held in position; this more extreme environment allows for most Space-DRUMS™ technical payload functionality tests to be conducted. In addition to flight hardware shakedowns, parabolic flights continue to be extensively used to study and evaluate the behavior of candidate-advanced materials proposed for ISS Space-DRUMS™ campaigns. The first samples to be processed in 2001 involve combustion synthesis (also known as SHS-Self-propagating High Temperature Synthesis) of large glass-ceramic and of porous ceramic spheres. Upmassing Space-DRUMS™ for the International Space Station is scheduled for early 2001. .

Guigné, J. Y.; Davidson, R.; Millan, D.

2000-01-01

346

Circulatory filling pressures during transient microgravity induced by parabolic flight  

NASA Technical Reports Server (NTRS)

Theoretical concepts hold that blood in the gravity dependent portion of the body would relocate to more cephalad compartments under microgravity. The result is an increase in blood volume in the thoraic and cardiac chambers. However, experimental data has been somewhat contradictory and nonconclusive. Early studies of peripheral venous pressure and estimates of central venous pressure (CVP) from these data did not show an increase in CVP under microgravity. However, CVP recorded in human volunteers during a parabolic flight revealed an increase in CVP during the microgravity state. On the STS 40 shuttle mission, a payload specialist wore a fluid line that recorded CVP during the first few hours of orbital insertion. These data revealed decreased CVP. When this CVP catheter was tested during parabolic flight in four subjects, two had increased CVP recordings and two had decreased CVP measurements. In 1991, our laboratory performed parabolic flight studies in several chronic-instrumented baboons. It was again noted that centrally recorded right atrial pressure varied with exposure to microgravity, some animals having an increase, and others a decrease.

Latham, Ricky D.; Fanton, John W.; White, C. D.; Vernalis, Mariana N.; Crisman, R. P.; Koenig, S. C.

1993-01-01

347

Solar thermal power plants for solar countries — Technology, economics and market potential  

Microsoft Academic Search

Solar power plants are needed to meet the growing electricity demand and at the same time to take care of the shrinking fossil resources and to reduce global CO2 emissions.In the first part of the paper the state of the art and the technical and economical development of the different solar thermal power plants (e.g. parabolic trough, central receiver and

Helmut Klaiß; Rainer Köhne; Joachim Nitsch; Uwe Sprengel

1995-01-01

348

Solar economy and technology update  

SciTech Connect

The industry, national, and consumer perspectives on solar power are reviewed. With a 30% increase in dealer/installers, and a 30% attrition rate, about 60% of the participants in the market are ''new kids on the block.'' The installed value of the market was $750 million in 1981. There was a 30% decline in volumes, due to the recession, in 1982. As for the national perspective, solar is labor intensive, and generated a billion dollars worth of jobs. As the DOE has abandoned all but high risk ''core technology'' RandD has faltered some. But desiccant heat pumps, polymer collectors, and parabolic collectors are discussed.

Brotherton, T.K.

1983-06-01

349

Solar concentrator with diffuser segments  

NASA Astrophysics Data System (ADS)

Solar energy systems use concentrating optics with photovoltaic cells for optimizing the performance. Advanced concentrators are designed to maximize both the light collection and the spatial uniformity of radiation. This is important because irradiance uniformity is critical for all types of photovoltaic cells. This is difficult to achieve with traditional concentrators, which are built with polished optical surfaces. In this work we propose a new concept of solar concentrator which uses small diffuser segments in key points to increase the irradiation uniformity. We experimentally demonstrate this new concept by analyzing the effects on both efficiency and irradiance uniformity due to the incorporation of scattering ribbons in a compound parabolic concentrator.

Esparza, Diego; Moreno, Ivan

2011-08-01

350

Carrier Dynamics in Parabolic InSb Based Multi Quantum Wells  

NASA Astrophysics Data System (ADS)

We report on time resolved differential transmission experiments in InSb/AlxIn1-xSb multi-parabolic quantum wells in the mid-infrared. The results of our numerical calculations, which included band non-parabolicity and the digital composition of the parabolic wells, allowed us to identify and probe the possible interband transitions. Our results provide new information on the carrier relaxations in this material system.

Bhowmick, Mithun; Merritt, Travis; Nontapot, Kanokwan; Khodaparast, Giti A.; Mishima, Tetsuya D.; Santos, Michael B.

2011-12-01

351

Dynamic model of a solar thermochemical water-splitting reactor with integrated energy collection and storage  

Microsoft Academic Search

Water-splitting solar thermochemical cycles are important in meeting the challenges of global climate change and limited fossil fuels. However, solar radiation varies in availability, leading to unsteady state operation. We propose a solar receiver-reactor with integrated energy collection and storage. The reactor consists of a double-pipe heat exchanger placed at the focal line of a parabolic trough solar concentrator. Molten

Rong Xu; Theodore F. Wiesner

352

Critical review of siting characteristics of small scale solar thermal energy systems  

SciTech Connect

An analysis was made of unique technical issues to be considered in siting solar-thermal energy systems in small communities. Four systems are described: central receiver, parabolic trough, parabolic dish, hemispherical bowl. The difference between central receiver systems and distributed receiver systems are indicated with reference to current applications. Finally, a technical siting comparison is made of the four systems defined, including overall efficiency, end use, land requirements, failure rates, safety considerations, energy backup systems and capital costs.

Sokolow, B.B.; Lobnitz, M.M.; Baruch, S.B.

1981-01-01

353

Error Analysis for Discontinuous Galerkin Method for Parabolic Problems  

NASA Technical Reports Server (NTRS)

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.

Kaneko, Hideaki

2004-01-01

354

Analytical studies of a parabolic line concentrator utilizing an aluminum honeycomb support structure and a thin glass reflector laminate  

SciTech Connect

Results (stresses, displacements, and equivalent slope errors) are presented from finite element analyses made to evaluate a design for a parabolic trough solar concentrator. The concentrator consists of a reflector laminate (made of thin glass bonded to sheet metal backing) which is mechanically formed and bonded to a stiff parabolic support (made of aluminum honeycomb bonded to steel skins) with a 2 meter (6.6 foot) aperture. Analyses were first made to determine a length for the concentrator such that it would meet certain performance and survivability criteria under wind and gravity loadings. These studies were made with a model for the concentrator only. The concentrator model was then combined with a model for a support mechanism, and this combined structure was studied for several wind and gravity loadings. A design characterized by a six meter (twenty foot) long concentrator was found to meet performance criteria and had sufficiently low glass stresses in a 40.23 meter per second ((ninety mile per hour) wind.

Koteras, J.R.

1981-03-01

355

Digital Foucault tester for the measurement of parabolic wave form  

NASA Astrophysics Data System (ADS)

Digital Foucault tester for quantitative estimate the wave form of aspheric surfaces is based on the high precision knife position determination and the image data processing methods. In this paper, we report a set of digital Foucault tester for the measurement of parabolic surface. The movement of the knife-edge is controlled by PC, and the shadow patterns are captured by a CCD in real time and then are fed back to the computer. A new kind of data processing method, which has the advantage of simple arithmetic and high precision, is given in the paper. The method offers a reliable base for Digital Foucault tester.

Wang, Xiao-Peng; Zhu, Ri-Hong; Wang, Lei

2009-07-01

356

PPM: Piecewise-Parabolic Methods for Astrophysical Fluid Dynamics  

NASA Astrophysics Data System (ADS)

A general description of some modern numerical techniques for the simulation of astrophysical fluid flow is presented. The methods are introduced with a thorough discussion of the especially simple case of advection. Attention is focussed on the piecewise-parabolic method (PPM). A description of the SLIC method for treating multifluid problems is also given. The discussion is illustrated by a number of advection and hydrodynamics test problems. Finally, a study of Kelvin-Helmholtz instability of supersonic jets using PPM with SLIC fluid interfaces is presented.

Woodward, P. R.

357

Stabilization of the solution of a doubly nonlinear parabolic equation  

NASA Astrophysics Data System (ADS)

The method of Galerkin approximations is employed to prove the existence of a strong global (in time) solution of a doubly nonlinear parabolic equation in an unbounded domain. The second integral identity is established for Galerkin approximations, and passing to the limit in it an estimate for the decay rate of the norm of the solution from below is obtained. The estimates characterizing the decay rate of the solution as x\\to\\infty obtained here are used to derive an upper bound for the decay rate of the solution with respect to time; the resulting estimate is pretty close to the lower one. Bibliography: 17 titles.

Andriyanova, È. R.; Mukminov, F. Kh

2013-09-01

358

Modeling of Coulomb interaction in parabolic quantum wires  

NASA Astrophysics Data System (ADS)

We study the exciton states in a parabolic quantum wire. An exactly solvable model is introduced for calculating the exciton state and the binding energy as a function of the radius of the quantum wire within the envelope-function approximation. In the calculation, we replace the actual Coulomb interaction between the electron and the hole by a Gaussian nonlocal separable potential and obtain closed expressions for both the envelope-function and the binding energy. Results are compared with those obtained by perturbative methods.

González-Santander, C.; Domínguez-Adame, F.

2009-09-01

359

Exciton States in a Quantum Dot with Parabolic Confinement  

NASA Astrophysics Data System (ADS)

In this study the electronic eigenstructure of an exciton in a parabolic quantum dot (QD) has been calculated with a high accuracy by using Finite element method (FEM). We have converted the coordinates of electron-light-hole system to relative and center of mass coordinate, then placed the Spherical Harmonics into Schrödinger equation analytically and obtained the Schrödinger equation which depends only on the radial variable. Finally we used FEM with only radial variable in order to get the accurate numerical results. We also showed first 21 energy level spectra of exciton depending on confinement and Coulomb interaction parameters.

Do?an, Ü.; Sakiro?lu, S.; Yildiz, A.; Akgüngör, K.; Epik, H.; Sökmen, I.; Sari, H.; Ergün, Y.

360

Piecewise-parabolic methods for astrophysical fluid dynamics  

SciTech Connect

A general description of some modern numerical techniques for the simulation of astrophysical fluid flow is presented. The methods are introduced with a thorough discussion of the especially simple case of advection. Attention is focused on the piecewise-parabolic method (PPM). A description of the SLIC method for treating multifluid problems is also given. The discussion is illustrated by a number of advection and hydrodynamics test problems. Finally, a study of Kelvin-Helmholtz instability of supersonic jets using PPM with SLIC fluid interfaces is presented.

Woodward, P.R.

1983-11-01

361

Parabolized Navier-Stokes methods for hypersonic flows  

NASA Technical Reports Server (NTRS)

A representative sampling of the techniques used in the integration of the Parabolized Navier-Stokes (PNS) equations is presented. Special atention is given to recent algorithms developed specifically for application to high speed flows, characterized by the presence of strong embedded shock waves and real gas effects. It is shown that PNS solvers are being used in the analysis of sonic boom signatures. Methods for modeling physical effects are discussed, including an overview of commonly used turbulence models and a more detailed discussion of techniques for including equilibrium and finite rate real gas effects.

Lawrence, Scott L.

1991-01-01

362

Analyzing parabolic profile path for underwater towed-cable  

NASA Astrophysics Data System (ADS)

This article discusses the dynamic state analysis of underwater towed-cable when tow-ship changes its speed in a direction making parabolic profile path. A three-dimensional model of underwater towed system is studied. The established governing equations for the system have been solved using the central implicit finite-difference method. The obtained difference non-linear coupled equations are solved by Newton's method and satisfactory results were achieved. The solution of this problem has practical importance in the estimation of dynamic loading and motion, and hence it is directly applicable to the enhancement of safety and the effectiveness of the offshore activities.

Srivastava, Vineet K.

2014-06-01

363

Parabolized Navier-Stokes methods for hypersonic flows  

NASA Technical Reports Server (NTRS)

The development and numerical solution of the Parabolized Navier-Stokes (PNS) equations is discussed. Special emphasis is placed on numerical integration algorithms for PNS solvers, most notably recent applications of upwind schemes. Application of this technology to high speed, high Reynolds number flows was the focus, and modeling techniques for real gas effects and turbulence were discussed. Experiences in validating the UPS upwind PNS flow solver for relatively simple body shapes are presented. The test cases range in complexity from two dimensional perfect gas cases to three dimensional finite rate chemistry cases.

Lawrence, S. L.

1992-01-01

364

Solar powered adsorption refrigerator with CPC collection system: Collector design and experimental test  

Microsoft Academic Search

Solar adsorption cooling systems are usually based on the flat plate collector, whereas little attention has been paid to concentrating collectors. Compound parabolic concentrators (CPC) are a versatile class of solar collectors that can be adapted to a large variety of applications and geometries. This work presents a CPC collector whose tubular receiver contains the sorption bed and where only

Manuel I. González; Luis R. Rodríguez

2007-01-01

365

Summary of engineering-scale experiments for the Solar Detoxification of Water project  

Microsoft Academic Search

This report contains a summary of large-scale experiments conducted at Sandia National Laboratories under the Solar Detoxification of Water project. The objectives of the work performed were to determine the potential of using solar radiation to destroy organic contaminants in water by photocatalysis and to develop the process and improve its performance. For these experiments, we used parabolic troughs to

J. E. Pacheco; L. Yellowhorse

1992-01-01

366

Present state of research on selective coatings for solar-energy converters  

Microsoft Academic Search

Recent developments in selective surface coatings for solar cells, flat plate and tubular collectors, and parabolic concentrators are reviewed. Solar cells treated with hydrazine hydrate or alkalies produce a surface with relief, which traps up to 97% of the spectrum. Multilayer cells transparent to the IR are noted for space applications; phosphor coatings to convert ultraviolet radiation to visible light

M. M. Koltun

1980-01-01

367

Fe(III)-solar light induced degradation of diethyl phthalate (DEP) in aqueous solutions  

Microsoft Academic Search

The degradation of diethyl phthalate (DEP) photoinduced by Fe(III) in aqueous solutions has been investigated under solar irradiation in the compound parabolic collector reactor at Plataforma Solar de Almeria. Hydroxyl radicals OH, responsible of the degradation, are formed via an intramolecular photoredox process in the excited state of Fe(III) aquacomplexes. The primary step of the reaction is mainly due to

G. Mailhot; M. Sarakha; B. Lavedrine; J. Cáceres; S. Malato

2002-01-01

368

Integrated solar energy system optimization  

NASA Astrophysics Data System (ADS)

The computer program SYSOPT, intended as a tool for optimizing the subsystem sizing, performance, and economics of integrated wind and solar energy systems, is presented. The modular structure of the methodology additionally allows simulations when the solar subsystems are combined with conventional technologies, e.g., a utility grid. Hourly energy/mass flow balances are computed for interconnection points, yielding optimized sizing and time-dependent operation of various subsystems. The program requires meteorological data, such as insolation, diurnal and seasonal variations, and wind speed at the hub height of a wind turbine, all of which can be taken from simulations like the TRNSYS program. Examples are provided for optimization of a solar-powered (wind turbine and parabolic trough-Rankine generator) desalinization plant, and a design analysis for a solar powered greenhouse.

Young, S. K.

1982-11-01

369

Optical properties of Dirac electrons in a parabolic well.  

PubMed

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. PMID:24205658

Kim, S C; Lee, J W; Yang, S-R Eric

2013-09-01

370

Classical behavior of few-electron parabolic quantum dots  

NASA Astrophysics Data System (ADS)

Quantum dots are intricate and fascinating systems to study novel phenomena of great theoretical and practical interest because low dimensionality coupled with the interplay between strong correlations, quantum confinement and magnetic field creates unique conditions for emergence of fundamentally new physics. In this work we consider two-dimensional semiconductor quantum dot systems consisting of few interacting electrons confined in an isotropic parabolic potential. We study the many-electron quantum ground state properties of such systems in presence of a perpendicular magnetic field as the number of electrons is varied using exact numerical diagonalizations and other approaches. The results derived from the calculations of the quantum model are then compared to corresponding results for a classical model of parabolically confined point charges who interact with a Coulomb potential. We find that, for a wide range of parameters and magnetic fields considered in this work, the quantum ground state energy is very close to the classical energy of the most stable classical configuration under the condition that the classical energy is properly adjusted to incorporate the quantum zero point motion.

Ciftja, O.

2009-06-01

371

Experimental testing of the variable rotated elastic parabolic equation.  

PubMed

A series of laboratory experiments was conducted to obtain high-quality data for acoustic propagation in shallow water waveguides with sloping elastic bottoms. Accurate modeling of transmission loss in these waveguides can be performed with the variable rotated parabolic equation method. Results from an earlier experiment with a flat or sloped slab of polyvinyl chloride (PVC) demonstrated the necessity of accounting for elasticity in the bottom and the ability of the model to produce benchmark-quality agreement with experimental data [J. M. Collis et al., J. Acoust. Soc. Am. 122, 1987-1993 (2007)]. This paper presents results of a second experiment, using two PVC slabs joined at an angle to create a waveguide with variable bottom slope. Acoustic transmissions over the 100-300 kHz band were received on synthetic horizontal arrays for two source positions. The PVC slabs were oriented to produce three different simulated waveguides: flat bottom followed by downslope, upslope followed by flat bottom, and upslope followed by downslope. Parabolic equation solutions for treating variable slopes are benchmarked against the data. PMID:22087895

Simpson, Harry J; Collis, Jon M; Soukup, Raymond J; Collins, Michael D; Siegmann, William L

2011-11-01

372

Shock unsteadiness in a thrust optimized parabolic nozzle  

NASA Astrophysics Data System (ADS)

This paper discusses the nature of shock unsteadiness, in an overexpanded thrust optimized parabolic nozzle, prevalent in various flow separation modes experienced during start up {(? P0 /? t > 0)} and shut down {(? P0/? t < 0)} sequences. The results are based on simultaneously acquired data from real-time wall pressure measurements using Kulite pressure transducers, high-speed schlieren (2 kHz) of the exhaust flow-field and from strain-gauges installed on the nozzle bending tube. Shock unsteadiness in the separation region is seen to increase significantly just before the onset of each flow transition, even during steady nozzle operation. The intensity of this measure ( rms level) is seen to be strongly influenced by relative locations of normal and overexpansion shock, the decrease in radial size of re-circulation zone in the back-flow region, and finally, the local nozzle wall contour. During restricted shock separation, the pressure fluctuations in separation region exhibit periodic characteristics rather than the usually observed characteristics of intermittent separation. The possible physical mechanisms responsible for the generation of flow unsteadiness in various separation modes are discussed. The results are from an experimental study conducted in P6.2 cold-gas subscale test facility using a thrust optimized parabolic nozzle of area-ratio 30.

Verma, S. B.

2009-07-01

373

Well-posedness results for triply nonlinear degenerate parabolic equations  

NASA Astrophysics Data System (ADS)

We study well-posedness of triply nonlinear degenerate elliptic-parabolic-hyperbolic problems of the kind b(-diva˜(u,??(u))+?(u)=f, u|=u in a bounded domain with homogeneous Dirichlet boundary conditions. The nonlinearities b,? and ? are supposed to be continuous non-decreasing, and the nonlinearity a˜ falls within the Leray-Lions framework. Some restrictions are imposed on the dependence of a˜(u,??(u)) on u and also on the set where ? degenerates. A model case is a˜(u,??(u))=f˜(b(u),?(u),?(u))+k(u)a(??(u)), with a nonlinearity ? which is strictly increasing except on a locally finite number of segments, and the nonlinearity a which is of the Leray-Lions kind. We are interested in existence, uniqueness and stability of L entropy solutions. For the parabolic-hyperbolic equation ( b=Id), we obtain a general continuous dependence result on data u,f and nonlinearities b,?,?,a˜. Similar result is shown for the degenerate elliptic problem, which corresponds to the case of b?0 and general non-decreasing surjective ?. Existence, uniqueness and continuous dependence on data u,f are shown in more generality. For instance, the assumptions [b+?](R)=R and the continuity of ??[ permit to achieve the well-posedness result for bounded entropy solutions of this triply nonlinear evolution problem.

Andreianov, B.; Bendahmane, M.; Karlsen, K. H.; Ouaro, S.

374

The solvability of the first initial-boundary problem for parabolic and degenerate parabolic equations in domains with a conical point  

SciTech Connect

The first initial-boundary problem for second-order parabolic and degenerate parabolic equations is investigated in a domain with a conical or angular point. The means of attack is already known and uses weighted classes of smooth or integrable functions. Sufficient conditions for a unique solution to exist and for coercive estimates for the solution to be obtained are formulated in terms of the angular measure of the solid angle and the exponent of the weight. It is also shown that if these conditions fail to hold, then the parabolic problem has elliptic properties, that is, it can have a nonzero kernel or can be nonsolvable, and, in the latter case, it is not even a Fredholm problem. A parabolic equation and an equation with some degeneracy or a singularity at a conical point are considered. Bibliography: 49 titles.

Degtyarev, Sergey P [Institute of Applied Mathematics and Mechanics, Ukraine National Academy of Sciences, Donetsk (Ukraine)

2010-09-02

375

Heat and electricity from the Sun using parabolic dish collector systems  

NASA Astrophysics Data System (ADS)

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.

Truscello, V. C.; Williams, A. N.

1980-05-01

376

Spheroidal corrections to the spherical and parabolic bases of the hydrogen atom  

SciTech Connect

This paper introduces the bases of the hydrogen atom and obtains recursion relations that determine the expansion of the spheroidal basis with respect to its parabolic basis. The leading spheroidal corrections to the spherical and parabolic bases are calculated by perturbation theory.

Mardyan, L.G.; Pogosyan, G.S.; Sisakyan, A.N.

1986-01-01

377

Heavy-ion fusion using a parabolic barrier with Coulomb interaction  

Microsoft Academic Search

In this work, we describe the fusion mechanism between two heavy ions as penetration through a parabolic barrier in the presence of a proper Coulomb interaction with appropriate boundary conditions. The parabolic potential is matched to the Coulomb potential in order to avoid any discontinuity of the potential surface. The Schrödinger equations in the exterior and interior regions containing, respectively,

Q. Haider; F. Bary Malik

1982-01-01

378

Dynamic modal characteristics of transverse vibrations of cantilevers of parabolic thickness  

Microsoft Academic Search

This paper deals with free transverse vibrations of nonuniform homogeneous beams. Cantilevers of rectangular (or elliptical) cross-section with parabolic thickness variation, and cantilevers of circular cross-section with parabolic radius variation, are considered. Factoring their fourth order differential equations of transverse vibrations into a pair of second order differential equations leads to general solutions in terms of hypergeometric functions. Exact natural

Dumitru I. Caruntu

2009-01-01

379

Non-parabolic hydrodynamic formulations for the simulation of inhomogeneous semiconductor devices  

NASA Technical Reports Server (NTRS)

Hydrodynamic models are becoming prevalent design tools for small scale devices and other devices in which high energy effects can dominate transport. Most current hydrodynamic models use a parabolic band approximation to obtain fairly simple conservation equations. Interest in accounting for band structure effects in hydrodynamic device simulation has begun to grow since parabolic models can not fully describe the transport in state of the art devices due to the distribution populating non-parabolic states within the band. This paper presents two different non-parabolic formulations of the hydrodynamic model suitable for the simulation of inhomogeneous semiconductor devices. The first formulation uses the Kane dispersion relationship (hk)(exp 2)/2m = W(1 + alpha(W)). The second formulation makes use of a power law ((hk)(exp 2)/2m = xW(sup y)) for the dispersion relation. Hydrodynamic models which use the first formulation rely on the binomial expansion to obtain moment equations with closed form coefficients. This limits the energy range over which the model is valid. The power law formulation readily produces closed form coefficients similar to those obtained using the parabolic band approximation. However, the fitting parameters (x,y) are only valid over a limited energy range. The physical significance of the band non-parabolicity is discussed as well as the advantages/disadvantages and approximations of the two non-parabolic models. A companion paper describes device simulations based on the three dispersion relationships: parabolic, Kane dispersion, and power low dispersion.

Smith, Arlynn W.; Brennan, Kevin F.

1995-01-01

380

Classification of Invariant Differential Operators for Non-Compact Lie Algebras via Parabolic Relations  

NASA Astrophysics Data System (ADS)

In the present paper we review the progress of the project of classification and construction of invariant differential operators for non-compact semisimple Lie groups. Our starting points is the class of algebras, which we called earlier 'conformal Lie algebras' (CLA), which have very similar properties to the conformal algebras of Minkowski space-time, though our aim is to go beyond this class in a natural way. For this we introduced recently the new notion of parabolic relation between two non-compact semisimple Lie algebras G and G' that have the same complexification and possess maximal parabolic subalgebras with the same complexification. Thus, we consider the exceptional algebra E7(7) which is parabolically related to the CLA E7(?25). Other interesting examples are the orthogonal algebras so(p, q) all of which are parabolically related to the conformal algebra so(n, 2) with p + q = n + 2, the parabolic subalgebras including the Lorentz subalgebra so(n ? 1,1) and its analogs so(p ? 1, q ? 1). Further we consider the algebras sl(2n, Bbb R) and for n = 2k the algebras su* (4k) which are parabolically related to the CLA su(n,n). Further we consider the algebras sp(r,r) which are parabolically related to the CLA sp(2r, Bbb R). We consider also E6(6) and E6(2) which are parabolically related to the hermitian symmetric case E6(-14),

Dobrev, V. K.

2014-05-01

381

Non-Parabolic Hydrodynamic Formulations for the Simulation of Inhomogeneous Semiconductor Devices  

NASA Technical Reports Server (NTRS)

Hydrodynamic models are becoming prevalent design tools for small scale devices and other devices in which high energy effects can dominate transport. Most current hydrodynamic models use a parabolic band approximation to obtain fairly simple conservation equations. Interest in accounting for band structure effects in hydrodynamic device simulation has begun to grow since parabolic models cannot fully describe the transport in state of the art devices due to the distribution populating non-parabolic states within the band. This paper presents two different non-parabolic formulations or the hydrodynamic model suitable for the simulation of inhomogeneous semiconductor devices. The first formulation uses the Kane dispersion relationship ((hk)(exp 2)/2m = W(1 + alphaW). The second formulation makes use of a power law ((hk)(exp 2)/2m = xW(exp y)) for the dispersion relation. Hydrodynamic models which use the first formulation rely on the binomial expansion to obtain moment equations with closed form coefficients. This limits the energy range over which the model is valid. The power law formulation readily produces closed form coefficients similar to those obtained using the parabolic band approximation. However, the fitting parameters (x,y) are only valid over a limited energy range. The physical significance of the band non-parabolicity is discussed as well as the advantages/disadvantages and approximations of the two non-parabolic models. A companion paper describes device simulations based on the three dispersion relationships; parabolic, Kane dispersion and power law dispersion.

Smith, A. W.; Brennan, K. F.

1996-01-01

382

Solar power water distillation unit  

NASA Astrophysics Data System (ADS)

Clean drinking water is the basic necessity for every human being, but about 1.1 billion people in the world lacked proper drinking water. There are many different types of water purification processes such as filtration, reverse osmosis, ultraviolet radiation, carbon absorption, but the most reliable processes are distillation and boiling. Water purification, such as distillation, is especially important in regions where water resources or tap water is not suitable for ingesting without boiling or chemical treatment. In design project It treats the water by combining different methods such as Filtration, Distillation and a technique called concentrated solar power (CSP). Distillation is literally the method seen in nature, whereby: the sun heats the water on the earth's surface, the water is turned into a vapor (evaporation) and rises, leaving contaminants behind, to form clouds. As the upper atmosphere drops in temperature the vapors cool and convert back to water to form water. In this project distillation is achieved by using a parabolic mirror which boils water at high temperature. Filtration is done by sand filter and carbon filter. First sand filter catches the sand particles and the carbon filter which has granules of active carbon is used to remove odor dissolved gases from water. This is the Pre-treatment of water. The filtered water is then collected in a water container at a focus of parabolic mirror where distillation process is done. Another important feature of designed project is the solar tracking of a parabolic mirror which increases the efficiency of a parabolic mirror [1],[2].

Hameed, Kamran; Muzammil Khan, Muhammad; Shahrukh Ateeq, Ijlal; Omair, Syed Muhammad; Ahmer, Muhammad; Wajid, Abdul

2013-06-01

383

Cost and performance evaluation of terrestrial solar thermal power systems  

Microsoft Academic Search

A cost optimization model was developed based on relating systems costs to performance and minimizing the system electric energy production costs. The model was applied to systems representing major categories of solar thermal power systems such as the central receiver, the parabolic dish, the line-focusing and the fixed orientation focusing collectors. Several types of engines and energy storage systems were

N. Elgabalawi

1982-01-01

384

First phase testing of solar thermal engine at United Stirling  

NASA Technical Reports Server (NTRS)

The objective of the program is to demonstrate that the Stirling engine is a practical efficient and reliable energy converter when integrated with a parabolic dish concentrator, and that it has the potential of being cost competitive with fossil fueled electric generating systems of today. The engine, with its receiver (solar heat exchanger), alternator and control system, is described.

Percival, W.; Nelving, H. G.

1981-01-01

385

An Iterative Numerical Method for the Incompressible Mean Flow over Parabolic Bodies.  

NASA Astrophysics Data System (ADS)

A new numerical method for solving the steady incompressible flow over parabolic bodies is presented. This is motivated by the need for obtaining an accurate solution of the basic flow for use in the solution of the unsteady boundary layer flow for determining leading edge receptivity by the method of Haddad & Corke(J. Fluid Mech.), 368, 1998. The method is a solution of the steady, nonlinear Navier-Stokes equations in streamfunction-vorticity form, in parabolic coordinates. A numerical, finite difference iterative technique was developed which is always stable, always convergent, converges to machine-zero accuracy, is very fast, and always converges to the unique solution regardless of the initial conditions for a given physical case. The method will be demonstrated for a family of parabolic bodies at different angles of attack, and compared to other approaches including ADI used by Davis(J. Fluid Mech.), 51, 3, 1972 for parabolic bodies in parabolic coordinates.

Erturk, E.; Corke, T. C.

1998-11-01

386

Air Brayton Solar Receiver, phase 2  

NASA Technical Reports Server (NTRS)

An air Brayton solar receiver (ABSR) is discussed. The ABSR consists of a cylindrical, insulated, offset plate fin heat exchanger which is mounted at the focal plane of a fully tracking parabolic solar collector. The receiver transfer heat from the concentrated solar radiation (which impinges on the inside walls of the heat exchanger) to the working fluid i.e., air. The hot air would then e used to drive a small Brayton cycle heat engine. The engine in turn drives a generator which produces electrical energy. Symmetrical and asymmetrical solar power input into the ABSR are analyzed. The symmetrical cases involve the baseline incident flux and the axially shifted incident fluxes. The asymmetrical cases correspond to the solar fluxes that are obtained by reduced solar input from one half of the concentrator or by receiver offset of plus or minus 1 inch from the concentrator optical axis.

Deanda, L. E.

1981-01-01

387

General theme report: Working session 2, Solar thermal systems  

SciTech Connect

Currently, over 90% of the world's large-scale solar electric energy is generated with concentrating solar thermal power plants. Such plants have the potential to meet many of the world's future energy needs. Research efforts are generally focused on generating electricity, though a variety of other applications are being pursued. Today, the technology for using solar thermal energy is well developed, cost competitive, and in many cases, ready for widespread application. The current state of each of the solar thermal technologies and their applications is reviewed, and recommendations for increasing their use are presented. The technologies reviewed in detail are: parabolic trough systems, central tower systems, and parabolic dish systems. 20 refs., 1 fig., 1 tab.

Alpert, D.J.; Kolb, G.J.

1991-01-01

388

Design requirements for interfaces in solar energy conversion technologies  

NASA Astrophysics Data System (ADS)

Candidate materials for improving the durability and economics of solar energy conversion systems (SECS) are reviewed. A 30-yr lifetime is regarded as necessary for solar collector and concentrator materials in order to offset the high initial costs of SECS in parabolic dish, heliostat, parabolic trough, flat plate collector, OTEC, solar cell, and wind turbine configurations. The materials are required to transfer a maximum amount of intercepted energy without degrading from exposure to UV radiation, wind, water, dust, and temperature cycling. Glass and mirrored surfaces for reflecting or refracting optical subsystems are currently made from soda-lime, boro- and aluminosilicate, and must resist chemicals, abrasion, and permeability, and have good strength, flexibility, coefficient of expansion, and Young's modulus. Additional concerns are present in photochemical, solar cell, and in substrata components and systems.

Butler, B. L.

1982-04-01

389

Effect of the parabolic potential on the binding energy of a hydrogenic impurity in a spherical quantum dot  

Microsoft Academic Search

The binding energy of the ground state of a hydrogenic off-center donor in a spherical quantum dot under a parabolic potential is calculated by a variational method within the effective-mass approximation. The parabolic potential is assumed to be a spherically symmetric potential. The location effects of a hydrogenic donor under a parabolic potential on the binding energy of the ground

Zhigang Xiao; Jiqian Zhu; Fenglai He

1996-01-01

390

Conceptual design of a glass-reinforced concrete solar collector  

NASA Astrophysics Data System (ADS)

An investigation of the properties and characteristics of glassfiber-reinforced concrete (GRC) was made to determine its suitability as a reflector substrate and structure for heliostats and solar collectors. The material properties and characteristics of GRC were established by tests on small flat panels. A conceptual design of a 2-m x 6-m parabolic trough solar collector module and a preliminary production-cost analysis were also completed.

Slemmons, A. J.; Ploeger, D. W.; Lundgren, R.

1981-07-01

391

Applied research concerning the direct steam generation in parabolic troughs  

Microsoft Academic Search

With levelized electricity costs (LEC) of 10–12USCts\\/kWh the well-known SEGS (Solar Electric Generating Systems) plants in California are presently the most successful solar technology for electricity generation [Price and Cable (2001) Proc. ASME Int. Solar Energy Conf. Forum 2001]. The SEGS plants apply a two-circuit system, consisting of the collector circuit and the Rankine cycle of the power block. These

M. Eck; E. Zarza; M. Eickhoff; J. Rheinländer; L. Valenzuela

2003-01-01

392

Large Phased Array Radar Using Networked Small Parabolic Reflectors  

NASA Technical Reports Server (NTRS)

Multifunction phased array systems with radar, telecom, and imaging applications have already been established for flat plate phased arrays of dipoles, or waveguides. In this paper the design trades and candidate options for combining the radar and telecom functions of the Deep Space Network (DSN) into a single large transmit array of small parabolic reflectors will be discussed. In particular the effect of combing the radar and telecom functions on the sizes of individual antenna apertures and the corresponding spacing between the antenna elements of the array will be analyzed. A heterogeneous architecture for the DSN large transmit array is proposed to meet the radar and telecom requirements while considering the budget, scheduling, and strategic planning constrains.

Amoozegar, Farid

2006-01-01

393

Parabolic approximation method for the mode conversion-tunneling equation  

SciTech Connect

The derivation of the wave equation which governs ICRF wave propagation, absorption, and mode conversion within the kinetic layer in tokamaks has been extended to include diffraction and focussing effects associated with the finite transverse dimensions of the incident wavefronts. The kinetic layer considered consists of a uniform density, uniform temperature slab model in which the equilibrium magnetic field is oriented in the z-direction and varies linearly in the x-direction. An equivalent dielectric tensor as well as a two-dimensional energy conservation equation are derived from the linearized Vlasov-Maxwell system of equations. The generalized form of the mode conversion-tunneling equation is then extracted from the Maxwell equations, using the parabolic approximation method in which transverse variations of the wave fields are assumed to be weak in comparison to the variations in the primary direction of propagation. Methods of solving the generalized wave equation are discussed. 16 refs.

Phillips, C.K.; Colestock, P.L.; Hwang, D.Q.; Swanson, D.G.

1987-07-01

394

High-order adaptive methods for parabolic systems  

NASA Astrophysics Data System (ADS)

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.

Adjerid, S.; Flaherty, J. E.; Moore, P. K.; Wang, Y. J.

1992-11-01

395

Explicit upwind algorithm for the parabolized Navier-Stokes equations  

NASA Technical Reports Server (NTRS)

A new explicit upwind algorithm based on Roe's flux-difference splitting (FDS) method has been developed for the three-dimensional Parabolized Navier-Stokes (PNS) equations. For three-dimensional flows, FDS's are determined separately for the two nonmarching directions and modified to account for the calculated shock angle in the crossflow plane. Second-order FDS is applied to the pressure and convection terms with the streamwise pressure gradient limited in the subsonic region to maintain a hyperbolic inviscid equation set. Second-order central differencing is obtained in the two-step algorithm for the shear and heat flux terms. The new algorithm is demonstrated for three laminar flow test cases: supersonic flow over a flat plate, hypersonic flow over a 15 deg ramp, and hypersonic flow past a 10 deg cone at a 24 deg angle of attack. The computed results agree well with experimental measurements.

Korte, John J.; Mcrae, D. Scott

1988-01-01

396

NASTRAN solutions of problems described by simultaneous parabolic differential equations  

NASA Technical Reports Server (NTRS)

NASTRAN solution techniques are shown for a numerical analysis of a class of coupled vector flow processes described by simultaneous parabolic differential equations. To define one physical problem type where equations of this form arise, the differential equations describing the coupled transfers of heat and mass in mechanical equilibrium with negligible mass average velocity are presented and discussed. Also shown are the equations describing seepage when both electrokinetic and hydrodynamic forces occur. Based on a variational statement of the general problem type, the concepts of scalar transfer elements and parallel element systems are introduced. It is shown that adoptation of these concepts allows the direct use of NASTRAN's existing Laplace type elements for uncoupled flow (the heat transfer elements) for treating multicomponent coupled transfer. Sample problems are included which demonstrate the application of these techniques for both steady-state and transient problems.

Mason, J. B.; Walston, W. H., Jr.

1975-01-01

397

Optimal Control of a Parabolic Equation with Dynamic Boundary Condition  

SciTech Connect

We investigate a control problem for the heat equation. The goal is to find an optimal heat transfer coefficient in the dynamic boundary condition such that a desired temperature distribution at the boundary is adhered. To this end we consider a function space setting in which the heat flux across the boundary is forced to be an L{sup p} function with respect to the surface measure, which in turn implies higher regularity for the time derivative of temperature. We show that the corresponding elliptic operator generates a strongly continuous semigroup of contractions and apply the concept of maximal parabolic regularity. This allows to show the existence of an optimal control and the derivation of necessary and sufficient optimality conditions.

Hoemberg, D., E-mail: hoemberg@wias-berlin.de; Krumbiegel, K., E-mail: krumbieg@wias-berlin.de [Weierstrass Institute for Applied Mathematics and Stochastics, Nonlinear Optimization and Inverse Problems (Germany); Rehberg, J., E-mail: rehberg@wias-berlin.de [Weierstrass Institute for Applied Mathematics and Stochastics, Partial Differential Equations (Germany)

2013-02-15

398

The particle acceleration in the parabolic magnetic field  

NASA Astrophysics Data System (ADS)

The problem of the efficiency of particle acceleration for parabolic poloidal magnetic field is considered within the approach of steady axisymmetric MHD flow. For the large Michel magnetization parameter ? it is possible to linearize the stream equation near the force-free solution and to solve the problem self-consistently as was done by Beskin, Kuznetsova & Rafikov for monopole magnetic field. It is shown that on the fast magnetosonic surface the particle Lorentz factor ? does not exceed the standard value ?1/3. On the other hand, in the supersonic region the Lorentz factor grows with the distance z from the equatorial plane as ? ~ (z/RL)1/2 up to the distance z ~ ?2RL, where RL = c/?F is the radius of the light cylinder. Thus, the maximal Lorentz factor is ?max ~ ?, which corresponds to almost the full conversion of the Poynting energy flux into the particle kinetic one.

Beskin, V. S.; Nokhrina, E. E.

2005-11-01

399

Reduction of weakly nonlinear parabolic partial differential equations  

NASA Astrophysics Data System (ADS)

It is known that the Swift-Hohenberg equation ?u/?t=-(?x2+1)2u+?(u-u3) can be reduced to the Ginzburg-Landau equation (amplitude equation) ?A/?t=4?x2A+?(A-3A|A|2) by means of the singular perturbation method. This means that if ? > 0 is sufficiently small, a solution of the latter equation provides an approximate solution of the former one. In this paper, a reduction of a certain class of a system of nonlinear parabolic equations ?u/?t=u+?f(u) is proposed. An amplitude equation of the system is defined and an error estimate of solutions is given. Further, it is proved under certain assumptions that if the amplitude equation has a stable steady state, then a given equation has a stable periodic solution. In particular, near the periodic solution, the error estimate of solutions holds uniformly in t > 0.

Chiba, Hayato

2013-10-01

400

Parabolic dish Stirling module development and test results  

SciTech Connect

Private industry and the U.S. Department of Energy are presently cost sharing the design, manufacture and test of a 25 Kwe parabolic dish Stirling module, known as Vanguard. The Vanguard module achieved a world's record sunlight to electric conversion efficiency of 31.6% in February 1984 at the Rancho Mirage, California test site. The module is presently operating daily in sunrise to sunset tests to determine the long term performance and O and M requirements of this distributed receiver system. Each module can be easily integrated into a larger field of modules to provide power generation opportunities from a single 25 Kwe unit for isolated loads to 30 Mwe systems for integrated utility power generation.

Washom, B.

1984-08-01

401

Using parabolic mirrors for complete imaging of apple surfaces.  

PubMed

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. PMID:19433353

Reese, Daniel; Lefcourt, Alan M; Kim, Moon S; Martin Lo, Y

2009-10-01

402

Nonlocal operators, parabolic-type equations, and ultrametric random walks  

SciTech Connect

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.

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

403

Nonlocal operators, parabolic-type equations, and ultrametric random walks  

NASA Astrophysics Data System (ADS)

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.

Chacón-Cortes, L. F.; Zúñiga-Galindo, W. A.

2013-11-01

404

Simulation of optical pulse compression using parabolic pulse with linear chirp  

NASA Astrophysics Data System (ADS)

It is the key of realizing high speed, large capacity fiber information transmission that achieve ultrashort optical pulse by optical pulse compression. At present, the compression method that is achieving parabolic pulse with linear chirp and compensating the linear chirp is paid more attention. Based on the two schemes for the parabolic pulse with linear chirp by the normal dispersion decreasing fiber or the fiber amplifier with a normal dispersion, more study on the characteristics of the parabolic pulse with linear chirp in the different dispersion decreasing profiles (such as cosine, Gaussian, linear, exponential and hyperbolic) is showed; the results show that, for different dispersion decreasing profiles, the good linear chirp and parabolic shapes that are good for pulse compression can be generated. Moreover, a novel scheme for the parabolic pulse, which is achieved by a dispersion decreasing fiber amplifier with a normal dispersion, is presented. Numerical simulations show that, compared with the parabolic pulses generated in the normal dispersion decreasing fiber or the fiber amplifier, the parabolic pulse generated by the novel scheme has the better linear chirp and the more pulse energy; the gain has an obviously effect on the intensity and quality of the linear chirp, which is that the output pulse has a smaller pulse width and higher pulse power after the chirp is compensated.

Wang, Zun-zhi

2013-08-01

405

Propagation of hypergeometric laser beams in a medium with a parabolic refractive index  

NASA Astrophysics Data System (ADS)

An expression to describe the complex amplitude of a family of paraxial hypergeometric laser beams propagating in a parabolic-index fiber is proposed. A particular case of a Gaussian optical vortex propagating in a parabolic-index fiber is studied. Under definite parameters, the Gaussian optical vortices become the modes of the medium. This is a new family of paraxial modes derived for the parabolic-index medium. A wide class of solutions of nonparaxial Helmholtz equations that describe modes in a parabolic refractive index medium is derived in the cylindrical coordinate system. As the solutions derived are proportional to Kummer’s functions, only those of them which are coincident with the nonparaxial Laguerre-Gaussian modes possess a finite energy, meaning that they are physically implementable. A definite length of the graded-index fiber is treated as a parabolic lens, and expressions for the numerical aperture and the focal spot size are deduced. An explicit expression for the radii of the rings of a binary lens approximating a parabolic-index lens is derived. Finite-difference time-domain simulation has shown that using a binary parabolic-index microlens with a refractive index of 1.5, a linearly polarized Gaussian beam can be focused into an elliptic focal spot which is almost devoid of side-lobes and has a smaller full width at half maximum diameter of 0.45 of the incident wavelength.

Kotlyar, V. V.; Kovalev, A. A.; Nalimov, A. G.

2013-12-01

406

Invariant differential operators for non-compact Lie algebras parabolically related to conformal Lie algebras  

NASA Astrophysics Data System (ADS)

In the present paper we continue the project of systematic construction of invariant differential operators for non-compact semisimple Lie groups. Our starting points is the class of algebras, which we call 'conformal Lie algebras' (CLA), which have very similar properties to the conformal algebras of Minkowski space-time, though our aim is to go beyond this class in a natural way. For this we introduce the new notion of parabolic relation between two non-compact semisimple Lie algebras G and G ' that have the same complexification and possess maximal parabolic subalgebras with the same complexification. Thus, we consider the exceptional algebra E 7(7) which is parabolically related to the CLA E 7(-25) , the parabolic subalgebras including E 6(6) and E 6(-26). Other interesting examples are the orthogonal algebras so(p, q) all of which are parabolically related to the conformal algebra so( n, 2) with p + q = n + 2, the parabolic subalgebras including the Lorentz subalgebra so( n - 1, 1) and its analogs so( p - 1, q - 1). We consider also E6(6) and E6(2) which are parabolically related to the hermitian symmetric case E6(-14) , the parabolic subalgebras including real forms of sl(6). We also give a formula for the number of representations in the main multiplets valid for CLAs and all algebras that are parabolically related to them. In all considered cases we give the main multiplets of indecomposable elementary representations including the necessary data for all relevant invariant differential operators. In the case of so( p, q) we give also the reduced multiplets. We should stress that the multiplets are given in the most economic way in pairs of shadow fields. Furthermore we should stress that the classification of all invariant differential operators includes as special cases all possible conservation laws and conserved currents, unitary or not.

Dobrev, V. K.

2013-02-01

407

Universal solar energy desalination system  

NASA Astrophysics Data System (ADS)

Design considerations to allow site-dependent flexibility in the choice of solar/wind powered desalinization plant configurations are discussed. A prototype design was developed for construction of 6300 cu m per day brackish water treatment in Brownsville, TX. The water is treated to reduce the amount of suspended solids and prevent scaling. A reverse osmosis unit processes the treated liquid to recover water at a ratio of 90%. The power system comprises a parabolic trough solar thermal system with an organic Rankine cycle generator, rock-oil thermal storage, and 200 kW wind turbines. Analysis of the complementarity of the solar and wind subsystems indicates that at any site one system will supplement the other. Energy storage, e.g., battery banks, would increase system costs to unacceptable levels. Climatic conditions will significantly influence the sizing of each segment of the total power system.

Fusco, V. S.

408

Solar thermal electricity generation  

NASA Astrophysics Data System (ADS)

This report presents the results of modeling the thermal performance and economic feasibility of large (utility scale) and small solar thermal power plants for electricity generation. A number of solar concepts for power systems applications have been investigated. Each concept has been analyzed over a range of plant power ratings from 1 MW(sub e) to 300 MW(sub e) and over a range of capacity factors from a no-storage case (capacity factor of about 0.25 to 0.30) up to intermediate load capacity factors in the range of 0.46 to 0.60. The solar plant's economic viability is investigated by examining the effect of various parameters on the plant costs (both capital and O & M) and the levelized energy costs (LEC). The cost components are reported in six categories: collectors, energy transport, energy storage, energy conversion, balance of plant, and indirect/contingency costs. Concentrator and receiver costs are included in the collector category. Thermal and electric energy transport costs are included in the energy transport category. Costs for the thermal or electric storage are included in the energy storage category; energy conversion costs are included in the energy conversion category. The balance of plant cost category comprises the structures, land, service facilities, power conditioning, instrumentation and controls, and spare part costs. The indirect/contingency category consists of the indirect construction and the contingency costs. The concepts included in the study are (1) molten salt cavity central receiver with salt storage (PFCR/R-C-Salt); (2) molten salt external central receiver with salt storage (PFCR/R-E-Salt); (3) sodium external central receiver with sodium storage (PFCR/RE-Na); (4) sodium external central receiver with salt storage (PFCR/R-E-Na/Salt); (5) water/steam external central receiver with oil/rock storage (PFCR/R-E-W/S); (6) parabolic dish with stirling engine conversion and lead acid battery storage (PFDR/SLAB); (7) parabolic dish with stirling engine conversion and redox advanced battery storage (PFDR/S-RAB); and (8) parabolic trough with oil/rock storage (LFDR/R-HT-45). Key annual efficiency and economic results of the study are highlighted in tabular format for plant sizes and capacity factor that resulted in the lowest LEC over the analysis range.

Gasemagha, Khairy Ramadan

1993-01-01

409

Saved by the Sun  

NSDL National Science Digital Library

This activity features video segments from a 2007 PBS program on solar energy. Students follow a seven-step invention process to design, build, and test a solar cooker that will pasteurize water. In addition, they are asked to describe how transmission, absorption, and reflection are used in a solar cooker to heat water and to evaluate what variables contribute to a successful cooker.

Lockwood, Jeff; Teachers, Nova

410

Fast Imaging Solar Spectrograph System in New Solar Telescope  

NASA Astrophysics Data System (ADS)

In 2004, Big Bear Solar Observatory in California, USA launched a project for construction of the world's largest aperture solar telescope (D = 1.6m) called New Solar Telescope(NST). University of Hawaii (UH) and Korea Astronomy and Space Science Institute(KASI) partly collaborate on the project. NST is a designed off-axis parabolic Gregorian reflector with very high spatial resolution(0.07 arcsec at 5000A) and is equipped with several scientific instruments such as Visible Imaging Magnetograph (VIM), InfraRed Imaging Magnetograph IRIM), and so on. Since these scientific instruments are focused on studies of the solar photosphere, we need a post-focus instrument for the NST to study the fine structures and dynamic patterns of the solar chromosphere and low Transition Region (TR) layer, including filaments/prominences, spicules, jets, micro flares, etc. For this reason, we developed and installed a fast imaging solar spectrograph(FISS) system on the NST withadvantages of achieving compact design with high spectral resolution and small aberration as well as recording many solar spectral lines in a single and/or dual band mode. FISS was installed in May, 2010 and now we carry out a test observation. In this talk, we introduce the FISS system and the results of the test observation after FISS installation.

Park, Y.-D.; Kim, Y. H.; Chae, J.; Goode, P. R.; Cho, K. S.; Park, H. M.; Nah, J. K.; Jang, B. H.

2010-12-01

411

Pasteurization of naturally contaminated water with solar energy.  

PubMed Central

A solar box cooker (SBC) was constructed with a cooking area deep enough to hold several 3.7-liter jugs of water, and this was used to investigate the potential of using solar energy to pasteurize naturally contaminated water. When river water was heated either in the SBC or on a hot plate, coliform bacteria were inactivated at temperatures of 60 degrees C or greater. Heating water in an SBC to at least 65 degrees C ensures that the water will be above the milk pasteurization temperature of 62.8 degrees C for at least an hour, which appears sufficient to pasteurize contaminated water. On clear or partly cloudy days, with the SBC facing magnetic south in Sacramento, bottom water temperatures of at least 65 degrees C could be obtained in 11.1 liters of water during the 6 weeks on either side of the summer solstice, in 7.4 liters of water from mid-March through mid-September, and in 3.7 liters of water an additional 2 to 3 weeks at the beginning and end of the solar season. Periodic repositioning of the SBC towards the sun, adjusting the back reflective lid, and preheating water in a simple reflective device increased final water temperatures. Simultaneous cooking and heating water to pasteurizing temperatures was possible. Additional uses of the SBC to pasteurize soil and to decontaminate hospital materials before disposal in remote areas are suggested.

Ciochetti, D A; Metcalf, R H

1984-01-01

412

Generalized Directional Gradients, Backward Stochastic Differential Equations and Mild Solutions of Semilinear Parabolic Equations  

SciTech Connect

We study a forward-backward system of stochastic differential equations in an infinite-dimensional framework and its relationships with a semilinear parabolic differential equation on a Hilbert space, in the spirit of the approach of Pardoux-Peng. We prove that the stochastic system allows us to construct a unique solution of the parabolic equation in a suitable class of locally Lipschitz real functions. The parabolic equation is understood in a mild sense which requires the notion of a generalized directional gradient, that we introduce by a probabilistic approach and prove to exist for locally Lipschitz functions.The use of the generalized directional gradient allows us to cover various applications to option pricing problems and to optimal stochastic control problems (including control of delay equations and reaction-diffusion equations),where the lack of differentiability of the coefficients precludes differentiability of solutions to the associated parabolic equations of Black-Scholes or Hamilton-Jacobi-Bellman type.

Fuhrman, Marco [Dipartimento di Matematica, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano (Italy)], E-mail: marco.fuhrman@polimi.it; Tessitore, Gianmario [Dipartimento di Matematica, Universita di Parma, via d'Azeglio 85, 43100 Parma (Italy)], E-mail: gianmario.tessitore@unipr.it

2005-05-15

413

Shaping of parabolic cylindrical membrane reflectors for the DART precision test bed  

NASA Technical Reports Server (NTRS)

The DART is a new telescope architecture consisting of two cylindrical parabolic reflectors. The system is ideally suited to using tensioned membranes for the reflective surfaces, owing to the zero Gaussian curvature of a cylindrical parabola.

White, C.; Salama, M.; Dragovan, M.; Schroeder, J.; Barber, D.; Dooley, J.

2003-01-01

414

The parabolic Sturmian-function basis representation of the six-dimensional Coulomb Green's function  

NASA Astrophysics Data System (ADS)

The square integrable basis set representation of the resolvent of the asymptotic three-body Coulomb wave operator in parabolic coordinates is obtained. The resulting six-dimensional Green's function matrix is expressed as a convolution integral over separation constants.

Zaytsev, S. A.

2009-01-01

415

Connection Between Spheric and Parabolic Coulomb Wave Functions in a Continuous Spectrum.  

National Technical Information Service (NTIS)

The direct and unverse transformations connecting parabolic and spherical Coulomb wave functions in the continuous spectrum are obtained. The coefficients of this transformations are expressed in term of generalized hypergeometric function sub 3 F sub 2 i...

G. S. Pogosyan V. M. Ter-Antonyan

1980-01-01

416

Transesophageal Echocardiographic Evaluation of Baboons During Microgravity Induced by Parabolic Flight.  

National Technical Information Service (NTIS)

Transthoracic echocardiography (TTE) is a feasible method to noninvasively examine cardiac anatomy during parabolic flight. However, transducer placement on the chest wall is very difficult to maintain during transition to microgravity. In addition, TTE r...

M. N. Vernalis R. D. Latham J. W. Fanton F. A. Geffney

1993-01-01

417

Investigation on the electrical properties of superlattice FETs using a non-parabolic band model  

NASA Astrophysics Data System (ADS)

The effect of non-parabolic energy-bands on the electrical properties of an In0.53Ga0.47As/In0.52Al0.48As superlattice FET has been investigated. An energy dependent effective mass was fitted on k · p simulation results and the new band model was implemented into a self-consistent Schrödinger-Poisson solver. This analysis has shown that non-parabolicity effects lead to noticeable changes of the device characteristics with respect the parabolic band model, namely: an increase of the on-state current and a steeper transition from the off- to the on-state sustained across several decades of current, at the expense of an increased off-state leakage. Moreover, the larger density of states in the non-parabolic model causes a 47% growth of the output conductance at low VDS, as well as an increased drain conductance in saturation.

Maiorano, P.; Gnani, E.; Grassi, R.; Gnudi, A.; Reggiani, S.; Baccarani, G.

2014-08-01

418

A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flows  

Microsoft Academic Search

A general, numerical, marching procedure is presented for the calculation of the transport processes in three-dimensional flows characterised by the presence of one coordinate in which physical influences are exerted in only one direction. Such flows give rise to parabolic differential equations and so can be called three-dimensional parabolic flows. The procedure can be regarded as a boundary-layer method. provided

S. V. PATANKAR; D. B. SPALDING

1972-01-01

419

Increased brain cortical activity during parabolic flights has no influence on a motor tracking task  

Microsoft Academic Search

Previous studies showed that changing forces of gravity as they typically occur during parabolic flights might be responsible\\u000a for adaptional processes of the CNS. However, until now it has not been differentiated between primary influences of weightlessness\\u000a and secondary influences due to psycho-physiological factors (e.g., physical or mental strain). With the aim of detecting\\u000a parabolic flight related changes in central

Stefan Schneider; Vera Brümmer; Andreas Mierau; Heather Carnahan; Adam Dubrowski; Heiko K. Strüder

2008-01-01

420

A parabolic function to modify Thornthwaite estimates of potential evapotranspiration for the eastern United States  

USGS Publications Warehouse

Errors of the Thornthwaite model can be analyzed using adjusted pan evaporation as an index of potential evapotranspiration. An examination of ratios of adjusted pan evaporation to Thornthwaite potential evapotranspiration indicates that the ratios are highest in the winter and lowest during summer months. This trend suggests a parabolic pattern. In this study a parabolic function is used to adjust Thornthwaite estimates of potential evapotranspiration. Forty locations east of the Rocky Mountains are analyzed. -from Author

McCabe, Jr, G. J.

1989-01-01

421

Pulse retiming based on XPM using parabolic pulses formed in a fiber Bragg grating  

Microsoft Academic Search

We experimentally demonstrate a novel all-optical all-fiberized pulse retiming scheme incorporating parabolic pulses generated in a linear fashion through pulse shaping in a superstructured fiber Bragg grating. The scheme relies on chirping the signal to be retimed using cross-phase modulation with the broader parabolic clock pulses, and subsequently retiming it through linear propagation in a dispersive medium. We demonstrate the

F. Parmigiani; P. Petropoulos; M. Ibsen; D. J. Richardson

2006-01-01

422

The Rashba Effect on the Bound Polaron in a Parabolic Quantum Dot  

NASA Astrophysics Data System (ADS)

The bound polaron ground state energy is calculated by the variational method of Pekar considering the influence of the Rashba SO interaction on the condition of electric-LO phonon strong coupling in a parabolic quantum dot (QD). The relations on the bound polaron ground state energy with the parallel confinement length, the electron-LO phonon coupling constant, the perpendicular confinement length and the Coulomb binding parameter are derived for a parabolic quantum dot.

Yin, Ji-Wen; Li, Wei-Ping; Yu, Yi-Fu; Xiao, Jing-Lin

2011-04-01

423

Long-time stability of large-amplitude noncharacteristic boundary layers for hyperbolic–parabolic systems  

Microsoft Academic Search

Extending investigations of Yarahmadian and Zumbrun in the strictly parabolic case, we study time-asymptotic stability of arbitrary (possibly large) amplitude noncharacteristic boundary layers of a class of hyperbolic–parabolic systems including the Navier–Stokes equations of compressible gas, and magnetohydrodynamics with inflow or outflow boundary conditions, establishing that linear and nonlinear stability are both equivalent to an Evans function, or generalized spectral

Toan Nguyen; Kevin Zumbrun

2009-01-01

424

Partition of Unity for a Class of Nonlinear Parabolic Equation on Overlapping Non-Matching Grids  

Microsoft Academic Search

A class of nonlinear parabolic equation on a polygonal domainR2 is inves- tigated in this paper. We introduce a finite element method on overlapping non-matching grids for the nonlinear parabolic equation based on the partition of unity method. We give the construction and convergence analysis for the semi-discrete and the fully discrete finite element methods. Moreover, we prove that the

Qisheng Wang; Kang Deng; Zhiguang Xiong; Yunqing Huang

2007-01-01

425

Invariant Differential Operators for Non-Compact Lie Groups:. Parabolic Subalgebras  

NASA Astrophysics Data System (ADS)

In the present paper, we start the systematic explicit construction of invariant differential operators by giving explicit description of one of the main ingredients — the cuspidal parabolic subalgebras. We explicate also the maximal parabolic subalgebras, since these are also important even when they are not cuspidal. Our approach is easily generalized to the supersymmetric and quantum group settings and is necessary for applications to string theory and integrable models.

Dobrev, V. K.

426

Hydrodynamic and heat transfer characteristics of laminar flow past a parabolic cylinder with constant heat flux  

Microsoft Academic Search

Steady, two-dimensional, symmetric, laminar and incompressible flow past parabolic bodies in a uniform stream with constant heat flux is investigated numerically. The full Navier-Stokes and energy equations in parabolic coordinates with stream function, vorticity and temperature as dependent variables were solved. These equations were solved using a second order accurate finite difference scheme on a non-uniform grid. The leading edge

M. Abu-Qudais; O. M. Haddad; A. M. Maqableh

2001-01-01

427

Numerical simulation of forced convection flow past a parabolic cylinder embedded in porous media  

Microsoft Academic Search

Numerical solutions are presented for steady two-dimensional symmetric flow past a parabolic cylinder embedded in porous media. For this study, the full Navier–Stokes equations (combined with the Brinkman–Forchheimer-extended Darcy model) and energy equation in parabolic coordinates were solved. A second order accurate finite difference scheme on a non-uniform grid was used. A wide range of Reynolds number (Re) is studied

O. M. Haddad; M. A. Al-Nimr; M. A. Abu-Ayyad

2002-01-01

428

Hydrodynamic and heat transfer characteristics of laminar flow past a parabolic cylinder with constant heat flux  

Microsoft Academic Search

Steady, two-dimensional, symmetric, laminar and incompressible flow past parabolic bodies in a uniform stream with constant\\u000a heat flux is investigated numerically. The full Navier–Stokes and energy equations in parabolic coordinates with stream function,\\u000a vorticity and temperature as dependent variables were solved. These equations were solved using a second order accurate finite\\u000a difference scheme on a non-uniform grid. The leading edge

M. Abu-Qudais; O. M. Haddad; A. M. Maqableh

2001-01-01

429

Observation d'un réseau de paraboles focales sous cisaillement dans un smectique A  

Microsoft Academic Search

On sait que, lorsqu'on dilate fortement un échantillon smectique homéotrope, à l'instabilité d'ondulation des couches succède la formation d'un treillis de paraboles focales. Nous montrons que ce même mécanisme subsiste sous cisaillement, l'effet de ce dernier étant de fixer l'orientation de l'instabilité initiale et de conduire à un treillis ordonné. On a étudié l'evolution de ce réseau de paraboles focales

Par P. Oswald; J. Béhar; M. Kléman

1982-01-01

430

On the coupling of hyperbolic and parabolic systems: Analytical and numerical approach  

NASA Technical Reports Server (NTRS)

The coupling of hyperbolic and parabolic systems is discussed in a domain Omega divided into two distinct subdomains omega(+) and omega(-). The main concern is to find the proper interface conditions to be fulfilled at the surface separating the two domains. Next, they are used in the numerical approximation of the problem. The justification of the interface conditions is based on a singular perturbation analysis, i.e., the hyperbolic system is rendered parabolic by adding a small artifical viscosity. As this goes to zero, the coupled parabolic-parabolic problem degenerates into the original one, yielding some conditions at the interface. These are taken as interface conditions for the hyperbolic-parabolic problem. Actually, two alternative sets of interface conditions are discussed according to whether the regularization procedure is variational or nonvariational. It is shown how these conditions can be used in the frame of a numerical approximation to the given problem. Furthermore, a method of resolution is discussed which alternates the resolution of the hyperbolic problem within omega(-) and of the parabolic one within omega(+). The spectral collocation method is proposed, as an example of space discretization (different methods could be used as well); both explicit and implicit time-advancing schemes are considered. The present study is a preliminary step toward the analysis of the coupling between Euler and Navier-Stokes equations for compressible flows.

Gastaldi, Fabio; Quarteroni, Alfio

1988-01-01

431

Performance of Infinitely Wide Parabolic and Inclined Slider Bearings Lubricated with Couple Stress or Magnetic Fluids  

NASA Astrophysics Data System (ADS)

The hydrodynamic and magnetohydrodynamic (MHD) lubrication problem of infinitely wide inclined and parabolic slider bearings is solved numerically using the finite element method. The bearing configurations are discretized into three-node isoparametric quadratic elements. Stiffness integrals obtained from the weak form of the governing equations are solved using Gauss quadrature to obtain a finite number of stiffness matrices. The global system of equations obtained from enforcing nodal continuity of pressure for the bearings are solved using the Gauss-Seidel iterative scheme with a convergence criterion of 10-10. Numerical computations reveal that, when compared for similar profile and couple stress parameters, greater pressure builds up in a parabolic slider compared to an inclined slider, indicating a greater wedge effect in the parabolic slider. The parabolic slider bearing is also shown to develop a greater load capacity when lubricated with magnetic fluids. The superior performance of parabolic slider bearing is more pronounced at greater Hartmann numbers for identical bearing structural parameters. It is also shown that when load carrying capacity is the yardstick for comparison, the parabolic slider bearings are superior to the inclined bearings when lubricated with couple stress or magnetic lubricants.

Oladeinde, Mobolaji Humphrey; Akpobi, John Ajokpaoghene

2011-10-01

432

Explicit Nonlinear Finite Element Geometric Analysis of Parabolic Leaf Springs under Various Loads  

PubMed Central

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.

Kong, Y. S.; Omar, M. Z.; Chua, L. B.; Abdullah, S.

2013-01-01

433

Parabolic Systems with p, q-Growth: A Variational Approach  

NASA Astrophysics Data System (ADS)

We consider the evolution problem associated with a convex integrand {f : {R}^{Nn}to [0,infty)} satisfying a non-standard p, q-growth assumption. To establish the existence of solutions we introduce the concept of variational solutions. In contrast to weak solutions, that is, mappings {u\\colon ?_T to {R}^n} which solve partial_tu-div Df(Du)=0 weakly in {?_T}, variational solutions exist under a much weaker assumption on the gap q - p. Here, we prove the existence of variational solutions provided the integrand f is strictly convex and 2n/n+2 < p le q < p+1. These variational solutions turn out to be unique under certain mild additional assumptions on the data. Moreover, if the gap satisfies the natural stronger assumption 2le p le q < p+ minbig \\{1,4/n big \\}, we show that variational solutions are actually weak solutions. This means that solutions u admit the necessary higher integrability of the spatial derivative Du to satisfy the parabolic system in the weak sense, that is, we prove that uin L^q_locbig(0,T; W^{1,q}_loc(?,{R}^N)big).

Bögelein, Verena; Duzaar, Frank; Marcellini, Paolo

2013-10-01

434

Diffusion phenomenon in the hyperbolic and parabolic regimes  

NASA Astrophysics Data System (ADS)

We discuss the diffusion phenomenon in the parabolic and hyperbolic regimes. New effects related to the finite velocity of the diffusion process are predicted, that can partially explain the strange behavior associated to adsorption phenomenon. For sake of simplicity, the analysis is performed by considering a sample in the shape of a slab limited by two perfectly blocking surfaces, in such a manner that the problem is one-dimensional in the space. Two cases are investigated. In the former, the initial distribution of the diffusing particles is assumed of gaussian type, centered around the symmetry surface in the middle of the sample. In the latter, the initial distribution is localized close to the limiting surfaces. In both cases, we show that the evolution toward to the equilibrium distribution is not monotonic. In particular, close to the limiting surfaces the bulk density of diffusing particles present maxima and minima related to the finite velocity of the diffusion process connected to the second order time derivative in the partial differential equation describing the evolution of the bulk density in the sample.

Sapora, A.; Codegone, M.; Barbero, G.

2013-11-01

435

Parabolic approximation method for the mode conversion-tunneling equation  

SciTech Connect

The derivation of the wave equation that governs ion cyclotron range of frequencies (ICRF) wave propagation, absorption, and mode conversion within the kinetic layer in tokamaks has been extended to include diffraction and focusing effects associated with the finite transverse dimensions of the incident wave fronts. The kinetic layer considered consists of a uniform density, uniform temperature slab model in which the equilibrium magnetic field is oriented in the z-italic-circumflex direction and varies linearly in the x-italic-circumflex direction. An equivalent dielectric tensor, as well as a two-dimensional energy conservation equation, are derived from the linearized Vlasov--Maxwell system of equations. A generalized, but approximate form of the mode conversion-tunneling equation is then extracted from the Maxwell equations, using the parabolic approximation method in which transverse variations of the wave fields are assumed to be weak in comparison to the variations in the primary direction of propagation. Numerical solutions of this approximate wave equation agree well with solutions to the exact wave equation within the kinetic layer.

Phillips, C.K.; Colestock, P.L.; Hwang, D.Q.; Swanson, D.G.

1989-02-01

436

High Speed Analysis Of Free Flights With A Parabolic Thruster  

NASA Astrophysics Data System (ADS)

A laser-based rangefinder with high temporal resolution, synchronized with a laser burst, is employed for fast on-site analysis of pulsed free flights. Additional high speed recordings from two different angles of view allow for full 3D-reconstruction of the trajectory and calibration of the rangefinder data. This reveals the whole dynamics of the flyer including the lateral and angular impulse coupling components as well as information on the detonation process. The employment of an ignition pin enhances the reproducibility of the momentum coupling due to a more reliable plasma ignition during the flight. The impact of initial lateral offset is studied and shows beam-riding properties of the parabolic craft within a small range. Back-driving forces are derived and compared with the theoretical model. The flight stability is evaluated with respect to the minimization and compensation of the lateral and angular momentum in a hovering experiment. Stable laser acceleration ranges up to 3 m altitude. Ballistic free flights close to the laboratory ceiling at 7.8 m are reported.

Scharring, Stefan; Eckel, Hans-Albert; Röser, Hans-Peter

2010-05-01

437

Differential invariants of generic parabolic Monge-Ampère equations  

NASA Astrophysics Data System (ADS)

Some new results on the geometry of classical parabolic Monge-Ampère equations (PMAs) are presented. PMAs are either integrable, or non-integrable according to the integrability of its characteristic distribution. All integrable PMAs are locally equivalent to the equation uxx = 0. We study non-integrable PMAs by associating with each of them a one-dimensional distribution on the corresponding first-order jet manifold, called the directing distribution. According to some property of this distribution, non-integrable PMAs are subdivided into three classes, one generic and two special. Generic PMAs are completely characterized by their directing distributions, and we study canonical models of the latter, projective curve bundles (PCB). A PCB is a one-dimensional sub-bundle of the projectivized cotangent bundle of a four-dimensional manifold. Differential invariants of projective curves composing such a bundle are used to construct a series of contact differential invariants for corresponding PMAs. These give a solution of the equivalence problem for generic PMAs with respect to contact transformations. The introduced invariants measure the nonlinearity of PMAs in an exact manner.

Catalano Ferraioli, D.; Vinogradov, A. M.

2012-07-01

438

High Speed Analysis Of Free Flights With A Parabolic Thruster  

SciTech Connect

A laser-based rangefinder with high temporal resolution, synchronized with a laser burst, is employed for fast on-site analysis of pulsed free flights. Additional high speed recordings from two different angles of view allow for full 3D-reconstruction of the trajectory and calibration of the rangefinder data. This reveals the whole dynamics of the flyer including the lateral and angular impulse coupling components as well as information on the detonation process. The employment of an ignition pin enhances the reproducibility of the momentum coupling due to a more reliable plasma ignition during the flight. The impact of initial lateral offset is studied and shows beam-riding properties of the parabolic craft within a small range. Back-driving forces are derived and compared with the theoretical model. The flight stability is evaluated with respect to the minimization and compensation of the lateral and angular momentum in a hovering experiment. Stable laser acceleration ranges up to 3 m altitude. Ballistic free flights close to the laboratory ceiling at 7.8 m are reported.

Scharring, Stefan; Eckel, Hans-Albert [Institute of Technical Physics, German Aerospace Center, D-70569 Stuttgart, Pfaffenwaldring 38-40 (Germany); Roeser, Hans-Peter [Institute of Space Systems, University of Stuttgart, D-70569 Stuttgart, Pfaffenwaldring 31 (Germany)

2010-05-06

439

High-order parabolic beam approximation for aero-optics  

SciTech Connect

The parabolic beam equations are solved using high-order compact differences for the Laplacians and Runge-Kutta integration along the beam path. The solution method is verified by comparison to analytical solutions for apertured beams and both constant and complex index of refraction. An adaptive 4th-order Runge-Kutta using an embedded 2nd-order method is presented that has demonstrated itself to be very robust. For apertured beams, the results show that the method fails to capture near aperture effects due to a violation of the paraxial approximation in that region. Initial results indicate that the problem appears to be correctable by successive approximations. A preliminary assessment of the effect of turbulent scales is undertaken using high-order Lagrangian interpolation. The results show that while high fidelity methods are necessary to accurately capture the large scale flow structure, the method may not require the same level of fidelity in sampling the density for the index of refraction. The solution is used to calculate a phase difference that is directly compared with that commonly calculated via the optical path difference. Propagation through a supersonic boundary layer shows that for longer wavelengths, the traditional method to calculate the optical path is less accurate than for shorter wavelengths. While unlikely to supplant more traditional methods for most aero-optics applications, the current method can be used to give a quantitative assessment of the other methods as well as being amenable to the addition of more physics.

White, Michael D., E-mail: Michael.White@wpafb.af.mi [Ohio Aerospace Institute, Wright-Patterson Air Force Base, OH 45433-7512 (United States)

2010-08-01

440

Piracetam and fish orientation during parabolic aircraft flight  

NASA Technical Reports Server (NTRS)

Goldfish were flown in parabolic Keplerian trajectories in a KC-135 aircraft to assay both the effectiveness of piracetam as an antimotion sickness drug and the effectiveness of state-dependent training during periods of oscillating gravity levels. Single-frame analyses of infrared films were performed for two classes of responses - role rates in hypogravity or hypogravity orienting responses (LGR) and climbing responses in hypergravity or hypergravity orienting responses (HGR). In Experiment I, preflight training with the vestibular stressor facilitated suppression of LGR by the 10th parabola. An inverse correlation was found between the magnitudes of LGR and HGR. Piracetam was not effective in a state-dependent design, but the drug did significantly increase HGR when injected into trained fish shortly before flight. In Experiment II, injections of saline, piracetam, and modifiers of gamma-aminobutyric acid - aminooxyacetic acid (AOAA) and isonicotinic acid did not modify LGR. AOAA did significantly increase HGR. Thus, the preflight training has a beneficial effect in reducing disorientation in the fish in weightlessness, but the drugs employed were ineffective.

Hoffman, R. B.; Salinas, G. A.; Homick, J. L.

1980-01-01

441

Motion sickness susceptibility in parabolic flight and velocity storage activity  

NASA Technical Reports Server (NTRS)

In parabolic flight experiments, postrotary nystagmus is as found to be differentially suppressed in free fall (G) and in a high gravitoinertial force (1.8 G) background relative to 1 G. In addition, the influence of postrotary head movements on nystagmus suppression was found to be contingent on G-dependency of the velocity storage and dumping mechanisms. Here, susceptibility to motion sickness during head movements in 0 G and 1.8 G was rank-correlated with the following: (1) the decay time constant of the slow phase velocity of postrotary nystagmus under 1 G, no head movement, baseline conditions, (2) the extent of time constant reduction elicited in 0 G and 1.8 G; (3) the extent of time constant reduction elicited by head tilts in 1 G; and (4) changes in the extent of time constants reduction in 0 G and 1.8 G over repeated tests. Susceptibility was significantly correlated with the extent to which a head movement reduced the time constant in 1 G, was weakly correlated with the baseline time constant, but was not correlated with the extent of reduction in 0 G or 1.8 G. This pattern suggests a link between mechanisms evoking symptoms of space motion sickness and the mechanisms of velocity storage and dumping. Experimental means of evaluating this link are described.

Dizio, Paul; Lackner, James R.

1991-01-01

442

Offset truss hex solar concentrator  

NASA Technical Reports Server (NTRS)

A solar energy concentrator system comprises an offset reflector structure made up of a plurality of solar energy reflector panel sections interconnected with one another to form a piecewise approximation of a portion of a (parabolic) surface of revolution rotated about a prescribed focal axis. Each panel section is comprised of a plurality of reflector facets whose reflective surfaces effectively focus reflected light to preselected surface portions of the interior sidewall of a cylindrically shaped solar energy receiver. The longitudinal axis of the receiver is tilted at an acute angle with respect to the optical axis such that the distribution of focussed solar energy over the interior surface of the solar engine is optimized for dynamic solar energy conversion. Each reflector panel section comprises a flat, hexagonally shaped truss support framework and a plurality of beam members interconnecting diametrically opposed corners of the hexagonal framework recessed within which a plurality of (spherically) contoured reflector facets is disposed. The depth of the framework and the beam members is greater than the thickness of a reflector facet such that a reflector facet may be tilted (for controlling the effective focus of its reflected light through the receiver aperture) without protruding from the panel section.

White, John E. (Inventor); Sturgis, James D. (Inventor); Erikson, Raymond J. (Inventor); Waligroski, Gregg A. (Inventor); Scott, Michael A. (Inventor)

1991-01-01

443

Solar astronomy  

NASA Technical Reports Server (NTRS)

An overview is given of modern solar physics. Topics covered include the solar interior, the solar surface, the solar atmosphere, the Large Earth-based Solar Telescope (LEST), the Orbiting Solar Laboratory, the High Energy Solar Physics mission, the Space Exploration Initiative, solar-terrestrial physics, and adaptive optics. Policy and related programmatic recommendations are given for university research and education, facilitating solar research, and integrated support for solar research.

Rosner, Robert; Noyes, Robert; Antiochos, Spiro K.; Canfield, Richard C.; Chupp, Edward L.; Deming, Drake; Doschek, George A.; Dulk, George A.; Foukal, Peter V.; Gilliland, Ronald L.

1991-01-01

444

Cluster eye camera using microlenses on parabolic surface  

NASA Astrophysics Data System (ADS)

There are two main types of imaging systems that exist in nature: the single aperture eye and the compound eye. Usually, cameras and most of artificial imaging systems are similar to the single aperture eye. But compound lenses can be more compact than single lenses. Our design is based on insect compound eyes, which also have a wide field of view (FOV). With the rise of micro-optical techniques, fabricating compound lenses has become easier. The simplest form of a curved microlens array is a parabolic surface. In this paper, we proposed a multi-channel imaging system, which combines the principles of the insect compound eye and the human eye. The optical system enables the reduction of track length of the imaging optics to achieve miniaturization. With the aid of optical engineering software ZEMAX, the multi-channel structure is simulated by a curved microlens array, and we use a Hypergon lens as the main lens to simulate the human eye, which can achieve the purpose of the wide FOV. With this architecture, each microlens of a microlens array transmits a segment of the overall FOV. The partial images that are separately recorded in different channels are stitched together to form the final image of the whole FOV by software processing. A 2.74 mm thin imaging system with 59 channels and 90° FOV is optimized using ZEMAX sequential ray tracing software on a 6.16 mm × 4.62 mm image plane. Finally, we will discuss the simulation results of this system and compare it with the optical cluster eye system and a mobile phone patent.

Shen, Hui-Kai; Su, Guo-Dung J.

2013-10-01

445

Parabolized Navier-Stokes Investigations of Hypersonic Intake Flows  

NASA Astrophysics Data System (ADS)

It is widely acknowledged that Parabolized Navier-Stokes (PNS) space marching is more efficient than time marching NS for the solution of supersonic and hypersonic viscous flow problems. The method, however, cannot deal with cases of strong upstream influence and subsequent streamwise flow separation without special treatment. This paper examines the applicabil- ity of the PNS equations to the prediction of flows associated with hypersonic propulsion and assesses the suitability of a multiple sweep algorithm to deal with the prediction of the flow in regions of strong streamwise adverse pressure gradient. Four experimental test cases of increasing complexity in terms of flow physics were chosen, each of which provided validation data for the type of flows which develop in the intakes of hypersonic propulsion systems such as the scramjet. A PNS solver has been shown to accurately predict these hypersonic flow fields including the complex shock-shock and shock-boundary layer interactions and associated flow separations and the resulting vortices which affect propulsion efficiency. A multiple sweep algorithm, applied to a manually defined region ahead of a compression ramp, has also been shown to deal with the accurate prediction of shock induced streamwise flow separation. The PNS space marching technique has been demonstrated to be significantly more efficient than a time marching solver, using the same computational grid, whilst providing results of comparable accuracy, even with the application of multiple sweeping. In addition the PNS solutions to these standard test cases have been shown to resolve small secondary flow features not seen in other studies such as corner vortices and embedded vortex shocks. This is because the PNS space marching approach, which stores only two or three 2-D grid planes at any one time, is able to employ computational grids of such a large size that memory requirements would be prohibitive for use with a 3D time marching code.

Prince, S. A.; Williams, M. J.

446

Heat engine development for solar thermal power systems  

NASA Technical Reports Server (NTRS)

The parabolic dish solar collector systems for converting sunlight to electrical power through a heat engine will, require a small heat engine of high performance long lifetime to be competitive with conventional power systems. The most promising engine candidates are Stirling, high temperature Brayton, and combined cycle. Engines available in the current market today do not meet these requirements. The development of Stirling and high temperature Brayton for automotive applications was studied which utilizes much of the technology developed in this automotive program for solar power engines. The technical status of the engine candidates is reviewed and the components that may additional development to meet solar thermal system requirements are identified.

Pham, H. Q.; Jaffe, L. D.

1981-01-01

447

Eigenmode structure in solar-wind Langmuir waves.  

PubMed

We show that observed spatial- and frequency-domain signatures of intense solar-wind Langmuir waves can be described as eigenmodes trapped in a parabolic density well. Measured solar-wind electric field spectra and waveforms are compared with 1D linear solutions and, in many cases, can be represented by 1-3 low-order eigenstates. To our knowledge, this report is the first observational confirmation of Langmuir eigenmodes in space. These results suggest that linear eigenmodes may be the starting point of the nonlinear evolution, critical for producing solar type II and type III radio bursts. PMID:18764383

Ergun, R E; Malaspina, D M; Cairns, Iver H; Goldman, M V; Newman, D L; Robinson, P A; Eriksson, S; Bougeret, J L; Briand, C; Bale, S D; Cattell, C A; Kellogg, P J; Kaiser, M L

2008-08-01

448

Technical and economical system comparison of photovoltaic and concentrating solar thermal power systems depending on annual global irradiation  

Microsoft Academic Search

Concentrating solar thermal power and photovoltaics are two major technologies for converting sunlight to electricity. Variations of the annual solar irradiation depending on the site influence their annual efficiency, specific output and electricity generation cost. Detailed technical and economical analyses performed with computer simulations point out differences of solar thermal parabolic trough power plants, non-tracked and two-axis-tracked PV systems. Therefore,

Volker Quaschning

2004-01-01

449

Ground-mounted thermal storage for the parabolic dish solar collector/Stirling engine system  

SciTech Connect

An initial evaluation is presented of the potential of centralized ground-mounted diurnal thermal storage for a dish-Stirling system. Several types of pumped-fluid thermal energy transport and phase-change thermal storage systems are considered. 5 refs.

Copeland, R.J.; Ullman, J.; Leach, J.W.

1981-01-01

450

High performance solar Stirling system  

NASA Technical Reports Server (NTRS)

A full-scale Dish-Stirling system experiment, at a power level of 25 kWe, has been tested during 1981 on the Test Bed Concentrator No. 2 at the Parabolic Dish Test Site, Edwards, CA. Test components, designed and developed primarily by industrial contractors for the Department of Energy, include an advanced Stirling engine driving an induction alternator, a directly-coupled solar receiver with a natural gas combustor for hybrid operation and a breadboard control system based on a programmable controller and standard utility substation components. The experiment demonstrated practicality of the solar Stirling application and high system performance into a utility grid. This paper describes the design and its functions, and the test results obtained.

Stearns, J. W.; Haglund, R.

1981-01-01

451

Optical collection efficiency and orientation of a solar trough medium-power plant installed in Italy  

Microsoft Academic Search

Parabolic trough collectors were investigated, applying the study results to a plant prototype installed in Florence (Italy) for residential supply. Ray tracing simulations examined optical characteristics and collection performance on the base of prototype geometry and functionality. The purpose was to control the realisation errors and overcome the difficulties arising in the development of the solar trough plant. The paper

P. Sansoni; D. Fontani; F. Francini; A. Giannuzzi; E. Sani; L. Mercatelli; D. Jafrancesco

2011-01-01

452

Performance of a low cost solar paraboloidal dish steam generating system  

Microsoft Academic Search

This paper presents the design, development and performance characteristics of a low cost solar steam generating system which incorporates recent design and materials innovations of parabolic dish technology. The concentrator is a deep dish of rather imperfect optics, made of silvered polymer reflectors fitted in the aluminum frame of a satellite communication dish. Conventional cavity receivers tend to be inadequate

N. D Kaushika; K. S Reddy

2000-01-01

453

A nonlinear steady-state characteristic performance curve for medium-temperature solar energy collectors  

Microsoft Academic Search

This paper reports on a numerical simulation model that was employed to investigate the effects of ambient temperature and insolation of the efficiency of compound parabolic concentrating solar energy collectors. The limitations of presently used collector performance characterization curves were investigated and a new approach proposed. The major advantage of the new procedure over those employed previously is that different

P. C. Eames; B. Norton

1991-01-01

454

Multi-criteria decision aid to assess concentrated solar thermal technologies  

Microsoft Academic Search

There are now several concentrated solar thermal technologies (CSP), such as parabolic troughs and central receivers using various heat transfer media, that have reached the phase of initial commercial deployment for large-scale power production. Information about cost, performance and impact on the environment of the systems being analyzed is currently affected by uncertainty. In many cases, traditional evaluation methods such

Fausto Cavallaro

2009-01-01

455

Carbon dioxide reforming of methane in a solar volume-TRIC receiver-reactor: The CAESAR (Catalytically Enhanced Solar Absorption Receiver) project  

NASA Astrophysics Data System (ADS)

Solar reforming of methane with CO2 was demonstrated successfully with a direct absorption receiver/reactor on a parabolic dish capable of 150 kW solar power. The reactor, a volumetric absorber, consisted of a reticulated porous alumina foam disk coated with rhodium catalyst. The system was operated during both steady-state and solar transient (cloud passage) conditions. The total solar power absorbed reached values up to 97 kW and the maximum methane conversion was almost 70 percent. Receiver efficiencies ranged up to 85 percent and chemical efficiencies peaked at 54 percent.

Buck, Reiner; Muir, James F.; Hogan, Roy E.; Skocypec, Russell D.

456

Passive nonlinear reshaping towards parabolic pulses in the steady-state regime in optical fibers  

NASA Astrophysics Data System (ADS)

The passive nonlinear reshaping in normally dispersive optical fibers in the steady-state regime is studied numerically. It is found that normal dispersion and self-phase modulation are able to provide pulse reshaping towards a parabolic pulse profile at the distances exceeding the optical wave breaking length. However, as compared to the similariton formation in active fibers the resulted pulse shape in passive fibers is strongly depended on the initial pulse parameters and nonlinear and dispersive fiber properties as well. The influence of initial pulse shape, initial chirp, third-order dispersion and loss on the parabolic pulse formation is studied consistently, and estimation of practical conditions which are needed for parabolic pulses formation in a passive fiber is provided.

Iakushev, Sergii O.; Shulika, Oleksiy V.; Sukhoivanov, Igor A.

2012-10-01

457

Heavy-ion fusion using a parabolic barrier with Coulomb interaction  

SciTech Connect

In this work, we describe the fusion mechanism between two heavy ions as penetration through a parabolic barrier in the presence of a proper Coulomb interaction with appropriate boundary conditions. The parabolic potential is matched to the Coulomb potential in order to avoid any discontinuity of the potential surface. The Schroedinger equation in the exterior and interior regions containing, respectively, the Coulomb and the parabolic potentials are solved and the penetrability function is calculated from the logarithmic derivative at the matching radius. The theory is then applied to calculate the fusion cross sections for the reactions /sup 16/O+ /sup 16/O, /sup 12/C+ /sup 28en-dash30/Si, /sup 16/O+ /sup 24,26/Mg, /sup 16/O+/sup 28en-dash30/Si, and /sup 40/Ca+ /sup 40/Ca and are found to reproduce the data quite well. The theory is valid for energies both below and above the barrier.

Haider, Q.; Malik, F.B.

1982-07-01

458

Wind load design methods for ground-based heliostats and parabolic dish collectors  

NASA Astrophysics Data System (ADS)

The purpose of this design method is to define wind loads on flat heliostat and parabolic dish collectors in a simplified form. Wind loads are defined for both mean and peak loads accounting for the protective influence of upwind collectors, wind protective fences, or other wind-blockage elements. The method used to define wind loads was to generalize wind load data obtained during tests on model collectors, heliostats or parabolic dishes, placed in a modeled atmospheric wind in a boundary-layer wind-tunnel at Colorado State University. For both heliostats and parabolic dishes, loads are reported for solitary collectors and for collectors as elements of a field. All collectors were solid with negligible porosity; thus the effects of porosity in the collectors is not addressed.

Peterka, J. A.; Derickson, R. G.

1992-09-01

459

Parabolic versus spherical partial cross sections for photoionization excitation of He near threshold  

SciTech Connect

Spherical and parabolic partial cross sections and asymmetry parameters, defined in the ejected electron frame, are presented for photoionization excitation of the helium atom at 0.1 eV above its double ionization threshold. A quantitative law giving the dominant spherical partial wave l{sub dom} for each excitation level n is obtained. The parabolic partial cross sections are shown to satisfy the same approximate selection rules as the related Rydberg series of doubly excited states (K,T){sub n}{sup A}. The analysis of radial and angular correlations reveals the close relationship between double excitation, ionization excitation, and double ionization. Opposite to a widespread belief, the observed value of the asymmetry parameter is shown to result from the interplay of radial correlations and symmetry constraints, irrespective of angular correlations. Finally, the measurement of parabolic partial cross sections is proposed as a challenge to experimentalists.

Bouri, C.; Selles, P.; Malegat, L.; Kwato Njock, M. G. [LIXAM et Federation LUMAT, CNRS et Universite Paris-Sud 11, 91405 Orsay (France); CEPAMOQ, Faculty of Science, University of Douala, P.O. Box 8580, Douala (Cameroon)

2006-09-15

460

Can industry afford solar energy  

NASA Astrophysics Data System (ADS)

Falling oil prices and conservation measures have reduced the economic impetus to develop new energy sources, thus decreasing the urgency for bringing solar conversion technologies to commercial readiness at an early date. However, the capability for solar to deliver thermal energy for industrial uses is proven. A year-round operation would be three times as effective as home heating, which is necessary only part of the year. Flat plate, parabolic trough, and solar tower power plant demonstration projects, though uneconomically operated, have revealed engineering factors necessary for successful use of solar-derived heat for industrial applications. Areas of concern have been categorized as technology comparisons, load temperatures, plant size, location, end-use, backup requirements, and storage costs. Tax incentives have, however, supported home heating and not industrial uses, and government subsidies have historically gone to conventional energy sources. Tax credit programs which could lead to a 20% market penetration by solar energy in the industrial sector by the year 2000 are presented.

Kreith, F.; Bezdek, R.

1983-03-01

461

Solar technology - A whether report  

NASA Astrophysics Data System (ADS)

Progress in the use of solar energy for producing large quantities of electrical power is assessed. The practicality of different applications of solar energy has been demonstrated, and present activity focuses on reducing production costs, enhancing efficiency, and improving reliability. Solar cell production reached 6 MW in 1982, but cuts in government research funding will delay the arrival of cost-competitive photovoltaics for commercial applications in developed countries. Research is expanding on amorphous Si cells, which are cheaper to produce while having lower efficiencies than single crystal cells. An estimated 60,000-80,000 passive solar houses have been constructed since 1978, and work is proceeding on better thermal control in the houses and more elegant storage techniques, such as long-lasting phase change materials. Industrially, a 114-unit array of parabolic concentrators producing 3 MW is providing steam for electricity and processing in a clothing factory. Tests of the 10 MWe Solar One heliostat array power plant in Barstow, CA have encouraged plans for a 100 MWe plant.

Finneran, K.

1983-03-01

462

Artificial neural networks for modelling the starting-up of a solar steam-generator  

Microsoft Academic Search

An experimental solar steam generator, consisting of a parabolic trough collector, a high-pressure steam circuit, and a suitable flash vessel has been constructed and tested in order to establish the thermodynamic performance during heat-up. The heat-up energy requirement has a marked effect on the system’s performance because solar energy collected during the heating-up period is lost at night due to

Soteris A. Kalogirou; Constantinos C. Neocleous; Christos N. Schizas

1998-01-01

463

Solar photo-Fenton degradation of Reactive Blue 4 in a CPC reactor  

Microsoft Academic Search

Solar photo-Fenton and solar photo-Fenton–ferrioxalate processes using a compound parabolic collector (CPC) were applied to the degradation of Reactive Blue 4 (RB4) solutions, proving to be an efficient method. Multivariate experimental design (including the following variables: pH and initial concentrations of Fe(II), oxalic acid, H2O2 and RB4) was used. The efficiency of photocatalytic degradation was determined from the analysis of

A. Durán; J. M. Monteagudo; E. Amores

2008-01-01

464

Principal Eigenvalues for Some Periodic-Parabolic Operators on RN and Related Topics  

NASA Astrophysics Data System (ADS)

We consider a periodic-parabolic eigenvalue problem with indefinite weight function m on RN ( N ? 3). Only under the assumption that the positive part of m has a certain decay we give necessary and sufficient conditions on m implying the existence of a unique positive principal eigenvalue. We prove that the zero solution of the corresponding parabolic equation looses stability at the principal eigenvalue. As a special case we obtain results on Schrodinger operators ? + ? m involving a coupling parameter ?, and on the stability properties of the corresponding Schrödinger semigroup et( ? + ? m) .

Daners, D.

465

Well-Posedness of Nonlocal Parabolic Differential Problems with Dependent Operators  

PubMed Central

The nonlocal boundary value problem for the parabolic differential equation v'(t) + A(t)v(t) = f(t)??(0 ? t ? T), v(0) = v(?) + ?, 0 < ? ? 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 C0?,?(E???) of all E???-valued continuous functions ?(t) on [0, T] satisfying a Hölder condition with a weight (t + ?)?. 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.

Ashyralyev, Allaberen; Hanalyev, Asker

2014-01-01

466

Parabolic replicator dynamics and the principle of minimum Tsallis information gain  

PubMed Central

Background Non-linear, parabolic (sub-exponential) and hyperbolic (super-exponential) models of prebiological evolution of molecular replicators have been proposed and extensively studied. The parabolic models appear to be the most realistic approximations of real-life replicator systems due primarily to product inhibition. Unlike the more traditional exponential models, the distribution of individual frequencies in an evolving parabolic population is not described by the Maximum Entropy (MaxEnt) Principle in its traditional form, whereby the distribution with the maximum Shannon entropy is chosen among all the distributions that are possible under the given constraints. We sought to identify a more general form of the MaxEnt principle that would be applicable to parabolic growth. Results We consider a model of a population that reproduces according to the parabolic growth law and show that the frequencies of individuals in the population minimize the Tsallis relative entropy (non-additive information gain) at each time moment. Next, we consider a model of a parabolically growing population that maintains a constant total size and provide an “implicit” solution for this system. We show that in this case, the frequencies of the individuals in the population also minimize the Tsallis information gain at each moment of the ‘internal time” of the population. Conclusions The results of this analysis show that the general MaxEnt principle is the underlying law for the evolution of a broad class of replicator systems including not only exponential but also parabolic and hyperbolic systems. The choice of the appropriate entropy (information) function depends on the growth dynamics of a particular class of systems. The Tsallis entropy is non-additive for independent subsystems, i.e. the information on the subsystems is insufficient to describe the system as a whole. In the context of prebiotic evolution, this “non-reductionist” nature of parabolic replicator systems might reflect the importance of group selection and competition between ensembles of cooperating replicators. Reviewers This article was reviewed by Viswanadham Sridhara (nominated by Claus Wilke), Puushottam Dixit (nominated by Sergei Maslov), and Nick Grishin. For the complete reviews, see the Reviewers’ Reports section.

2013-01-01

467

Parabolic sturmians approach to the three-body continuum Coulomb problem  

NASA Astrophysics Data System (ADS)

The three-body continuum Coulomb problem is treated in terms of the generalized parabolic coordinates. Approximate solutions are expressed in the form of a Lippmann-Schwinger-type equation, where the Green's function includes the leading term of the kinetic energy and the total potential energy, whereas the potential contains the non-orthogonal part of the kinetic energy operator. As a test of this approach, the integral equation for the ( e -, e -, He++) system has been solved numerically by using the parabolic Sturmian basis representation of the (approximate) potential. Convergence of the expansion coefficients of the solution has been obtained as the basis set used to describe the potential is enlarged.

Zaytsev, S. A.; Popov, Yu. V.; Piraux, B.

2013-03-01

468

Solar Power  

NSDL National Science Digital Library

Students learn about solar energy and how to calculate the amount of solar energy available at a given location and time of day on Earth. The importance of determining incoming solar energy for solar devices is discussed.

Integrated Teaching And Learning Program

469

Technology transfer: Solar power and distributed rural electrification  

Microsoft Academic Search

The objective of this paper is to assess and transfer a high efficiency multi-junction photovoltaic technology developed at the National Renewable Energy Lab to a startup venture. The multi-junction cell will be located at the focal point of a parabolic reflector integrated into a small solar tracking system. This technology is a rooftop satellite-dish-sized reflector that will track the sun,

Stephen W. Jordan; Tugrul Daim

2011-01-01

470

Evaluation of a Line-Concentrating Solar Collector  

NASA Technical Reports Server (NTRS)

45-page report contains results of performance evaluation of line-concentrating solar collector. Collector employs parabolic trough to direct Sunlight to line along its focal axis, along which lies a black-chrome plated receiver tube covered by a glass tube containing still air. Reflective trough has aluminum-mirror surface covered with metallized acrylic film. Array of four collectors, positioned end to end was used for evaluation. Array was driven by single drive mechanism which was controlled by electronic tracking device.

1982-01-01

471

Applied studies in solar photocatalytic detoxification: an overview  

Microsoft Academic Search

The technical feasibility and performance of photocatalytic degradation of four water-soluble pesticides (diuron, imidacloprid, formetanate and methomyl) have been studied at pilot scale in two well-defined systems which are of special interest because natural-solar UV light can be used for them: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. The pilot plant is made up of compound parabolic

Sixto Malato; Julián Blanco; Alfonso Vidal; Diego Alarcón; Manuel I. Maldonado; Julia Cáceres; Wolfgang Gernjak

2003-01-01

472

Exergy modeling of a new solar driven trigeneration system  

Microsoft Academic Search

In this paper, exergy modeling is used to assess the exergetic performance of a novel trigeneration system using parabolic trough solar collectors (PTSC) and an organic Rankine cycle (ORC). Four cases are considered: electrical-power, cooling-cogeneration, heating-cogeneration, and trigeneration. In this trigeneration system a single-effect absorption chiller is utilized to provide the necessary cooling energy and a heat exchanger is utilized

Fahad A. Al-Sulaiman; Ibrahim Dincer; Feridun Hamdullahpur

2011-01-01

473

Projected techno-economic improvements for advanced solar thermal power plants  

NASA Technical Reports Server (NTRS)

The projected characteristics of solar thermal power plants (with outputs up to 10 MWe) employing promising advanced technology subsystems/components are compared to current (or pre-1985) steam-Rankine systems. Improvements accruing to advanced technology development options are delineated. The improvements derived from advanced systems result primarily from achieving high efficiencies via solar collector systems which (1) capture a large portion of the available insolation and (2) concentrate this captured solar flux to attain high temperatures required for high heat engine/energy conversion performance. The most efficient solar collector systems employ two-axis tracking. Attractive systems include the central receiver/heliostat and the parabolic dish.

Fujita, T.; Manvi, R.; Roschke, E. J.

1979-01-01

474

Solar Thermoelectric Generator for Micropower Applications  

NASA Astrophysics Data System (ADS)

Solar thermoelectric generators (STG) using cheap parabolic concentrators with high- ZT modules can be a cost-effective alternative to solar photovoltaics for micropower generation. A thermodynamic analysis is presented for predicting the thermal-to-electrical conversion efficiency for the generator. With solar concentration of 66× suns, a system efficiency of 3% was measured for a commercial Bi2Te3 module with output power of 1.8 W. Using novel thermoelectric materials such as n-type ErAs:(InGaAs)1- x (InAlAs) x and p-type (AgSbTe) x (PbSnTe)1- x , a conversion efficiency of 5.6% can be achieved for a STG at 120× suns.

Amatya, R.; Ram, R. J.

2010-09-01

475

Cross-Polarization Cancellation in an Offset Parabolic Reflector Antenna Using a Corrugated Matched Feed  

Microsoft Academic Search

This letter presents the design of a dual-mode corrugated matched feed to cancel the unwanted high cross polarization and beam squinting in an offset parabolic reflector antenna. The matched feed concept has been implemented in a cylindrical corrugated structure by adding a higher order HE21 mode to the fundamental HE11 mode. The designed feed was then used to illuminate a

S. B. Sharma; Dhaval Pujara; S. B. Chakrabarty; Ranajit Dey

2009-01-01

476

Alternating Direction Implicit Methods for Parabolic Equations with a Mixed Derivative.  

National Technical Information Service (NTIS)

Alternating direction implicit (ADI) schemes for two-dimensional parabolic equations with a mixed derivative are constructed by using the class of all A sub 0-stable linear two-step methods in conjunction with the method of approximation factorization. Th...

R. M. Beam R. F. Warming

1979-01-01

477

On a singularly perturbed mixed problem for a linear parabolic equation with nonlinear boundary conditions  

NASA Astrophysics Data System (ADS)

A mixed problem for a linear parabolic equation with a small parameter multiplying the time derivative and with nonlinear boundary conditions is solved. Such boundary conditions arise in some heat and mass transfer problems, for example, in cooling thin spherical gas-filled shells or in the case of a gas filling such shells with gas-permeable walls.

Belolipetskii, A. A.; Ter-Krikorov, A. M.

2014-01-01

478

Simple Verification of the Parabolic Shape of a Rotating Liquid and a Boat on Its Surface  

ERIC Educational Resources Information Center

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.)

Sabatka, Z.; Dvorak, L.

2010-01-01

479

A posteriori finite element bounds for output functionals of discontinuous Galerkin discretizations of parabolic problems  

Microsoft Academic Search

We present a Neumann-subproblem a posteriori finite element procedure for the efficient calculation of constant-free, sharp lower and upper estimators for linear functional outputs of parabolic equations discretized by a discontinuous Galerkin method in time. In space, a global coarse mesh and a decoupled fine mesh are used to compute the estimators which are shown to converge to the value

L. Machiels

2001-01-01

480

A posteriori error estimates of mixed DG finite element methods for linear parabolic equations  

Microsoft Academic Search

In this article, we analyse a posteriori error estimates of mixed finite element discretizations for linear parabolic equations. The space discretization is done using the order ????1 Raviart–Thomas mixed finite elements, whereas the time discretization is based on discontinuous Galerkin (DG) methods (r???1). Using the duality argument, we derive a posteriori l (L ) error estimates for the scalar function,

Tianliang Hou

2012-01-01

481

Distribution of field sizes in a petroleum system: parabolic fractal, lognormal or stretched exponential?  

Microsoft Academic Search

Field size distributions in three Petroleum Systems have been analyzed using different approaches. The parabolic fractal model shows the Niger delta and the Gulf of Mexico (GOM) Outer Continental Shelf (OCS) have similar dispersed habitats, in contrast to the Saharan Triassic, which has a concentrated habitat. On a lognormal model, the Niger delta and the Saharan Triassic field size distributions

Jean Laherrere

2000-01-01

482

Improved Accuracy for Alternating Direction Methods for Parabolic Equations Based on Mixed Finite Element Procedures  

Microsoft Academic Search

Abstract Classical alternating direction(AD) method for parabolic equations, based on some standard implicit time stepping procedure such as Crank-Nisolson, can have errors associated with the AD perturbations that are much larger than the errors associated with the underlying time stepping procedure. We show that minor modifications in the AD procedure can virtually eliminate the perturbation errors at an minor additional

Song-ming Yang

483

Fast Computation of the Nonlocal Boundary Condition in Finite Difference Parabolic Equation Radiowave Propagation Simulations  

Microsoft Academic Search

Finite difference parabolic equation method (FD-PEM) codes using a nonlocal boundary condition to model radiowave propagation over electrically large domains, require the computation of time consuming spatial convolution integrals. For the first time, we propose the use of recursive convolution (RC) with vector fitting (VF) to reduce this computational burden. RC is based on the ability to express functions as

Christos Mias

2008-01-01

484

UMPE: The University of Miami Parabolic Equation Model. Version 1.0.  

National Technical Information Service (NTIS)

Solving the acoustic wave equation using the parabolic approximation is a popular approach of many available underwater acoustic models. Here we develop and present a version of the PE model developed at the University of Miami from 1989 to the present un...

K. B. Smith F. D. Tappert

1993-01-01

485

On stabilization of solutions to boundary value problems for quasilinear parabolic equations periodic in time  

Microsoft Academic Search

In the present article we study the behavior at large time of solutions to a boundary value problem for a quasilinear parabolic equation co-periodic in time. Denote by u(x, t; u0) a solution to the boundary value problem which assumes a value u0 at t = 0. Under some additional assumptions, we prove that any uniformly bounded (for t _

M. P. Vishnevskiî

1993-01-01

486

Boundary value problem for a first-order linear parabolic system  

NASA Astrophysics Data System (ADS)

A boundary value problem for a linear parabolic system is considered. Sufficient conditions for the well-posedness of the problem are found. The spline collocation method on a uniform grid is used to construct a high-order accurate implicit difference scheme, and its absolute stability is proved.

Gaidomak, S. V.

2014-04-01

487

Equivalence of physical optics and aperture field integration method for parabolic reflectors with offset feeds  

Microsoft Academic Search

This paper discusses the equivalence of physical optics (PO) and the aperture field integration method (AFIM) for the full pattern prediction of parabolic reflectors with offset feeds. In the calculation of the AFIM, there are two important procedures for obtaining the scattered fields. The first one is how to choose the surface of integration. The second one is how to

M. Oodo; K. Hara; M. Ando

1997-01-01

488

Gradient estimates for variable coefficient parabolic equations and singular perturbation problems  

Microsoft Academic Search

In this article we prove, via monotonicity formulas, interior and boundary gradient esti- mates for solutions to second order parabolic equations, in divergence form, with Dini top order coefficients. We then prove uniform Lipschitz estimates for solutions of singular perturbation prob- lems, using the previous results, and two phase monotonicity formulas. Introduction. The purpose of this paper is to study

L. Ca Arelli; Carlos E. Kenig

1998-01-01

489

Fast Time and Space Parallel Algorithms for Solution of Parabolic Partial Differential Equations  

NASA Technical Reports Server (NTRS)

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.

Fijany, Amir

1993-01-01