1,556 research outputs found
Boiling Heat Transfer of R-1234yf in Horizontal Circular Small Tubes
No full textAn experimental study for heat transfer coefficient and pressure drop with two-phase flow phase change was conducted with R-1234yf in horizontal circular small tubes. The experimental facilities have been used to take data under various flow conditions with intensive study. The test section is made of stainless steel tubes with inner tube diameters of 1.5 mm and 3.0 mm, the length of 1000 mm and 2000 mm each. The small tubes were uniformly heated by engaging an electric current directly to the single tubes; all components were well insulated to prevent heat losses. Local heat transfer coefficients and pressure drop were obtained for a heat flux of 5-40 kW m-2, a mass flux of 50-600 kg m-2 s-1, saturation temperatures of 0, 5, and 10℃ and quality of up to 1.0. The effects of mass flux, heat flux, saturation temperature, and inner tube diameter on heat transfer coefficient and pressure drop are reported. Nucleate boiling heat transfer contribution was predominant, especially at low quality region, and laminar flow appeared in the evaporative small tubes. A new boiling heat transfer coefficient correlation for R-1234yf was developed
Vapor Pressure of Hydrofluoroolefins: Critical Review of Experimental Data and Models
No full textThis paper critically reviews vapor pressure data and vapor pressure models for seventeen hydrofluoroolefins, including R1234yf and R1234ze(E), and presents Wagner-type vapor pressure correlations for the seventeen hydrofluoroolefins
Telegram, 1936 Aug. 25, Burbank Calif., to Edward C. Elliott
No full textTelegram from Amelia Earhart to Edward Elliott "Convocation Ok as far as now possible to foresee (STOP) do greet old friend of mine at Mark Hopkins Mrs. Ambrose Diehl (STOP) I planning leave for east day after tomorrow if can get few final details cleared up cheerio A E 235 P," August 25, 1936
Building On and Honoring Forty Years of PBL Scholarship from Howard Barrows: A Scientometric, Large-Scale Data, and Visualization-based Analysis
No full textOver the past forty years, Howard Barrows’ contributions to PBL research have influenced and guided educational research and practice in a diversity of domains. It is necessary to make visible to all PBL scholars what has been accomplished, what is perceived as significant, and what is the scope of applicability for Barrows’ groundbreaking findings. As more disciplines recognize Barrows’ efforts and adopt PBL in education, it becomes crucial but challenging to sustain community memory so that PBL scholars are kept well informed of research innovations in various domains. In this paper, we review Barrows’ scholarly efforts in PBL and reveal the impacts on subsequent studies in various domains. A bibliometrics analysis is conducted on Barrows’ PBL publications and the corresponding citations to quantitatively measure Barrows’ impact. Our findings demonstrate Barrows’ exceptional contributions to PBL and the disciplinary differences in conducting PBL studies based on Barrows’ work. It is also revealed that PBL scholars who share similar interests have rarely collaborated with each other. The PBL research community has a real opportunity to connect isolated research groups and reduce the fragmentation so that research innovations in one domain can be disseminated to inform other scholars
Librarian Roles in Institutional Repository Data Set Collecting: Outcomes of a Research Library Task Force
No full textThe collection development role of the academic librarian in the research university library is increasingly subject to significant change as opportunities to build new types of library collections proliferate, particularly with respect to research data. A Purdue Libraries task force was charged with building faculty-produced collections for a data repository prototype. One purpose of the project was to inventory and characterize the resources and skills required of the libraries and its data-collecting librarians. This paper examines the librarian roles and activities that were identified during the project and suggestsways the experience of the task force can inform the roles and activities of librarians who are similarly charged
Spaceborne Demonstration of P-Band Signals of Opportunity Remote Sensing: Instrument Modeling and Validation
No full textSignals of Opportunity (SoOp) reflectometry allows the reuse of existing communication signals as sources of illumination for remote sensing. The Signals of Opportunity P-band Investigation (SNOOPI) mission is a spaceborne technology demonstration of a P-Band SoOp receiver. P-Band frequencies allow for deeper penetration depths for soil moisture sensing than conventional L-Band radar instruments. P-Band also allows for higher precision in applications requiring phase unwrapping such as Snow Water Equivalent measurements. To support the SNOOPI instrument development and analysis, a bit-level simulator was developed to verify the microwave instrument and digital signal processor unit. A groundmonitoring station was developed to monitor the SoOp source’s Effective Isotropic Radiated Power (EIRP), background noise sky-map verification, and self-ambiguity function monitoring. An overview of tower based instruments implementing the SoOp receiver technique is also provided
Test and application of gravitational theories in astronomical systems
No full textThe motivation of our analysis is to put constraints, beyond making them unlikely, on a variety of Newtonian perturbations that could conspire to imitate the timing effects of the relativistic two-body model. This will provide an assessment on the quality of the evidence that the decay of the pulsar\u27s orbital period is caused by the energy loss of the binary pulsar system in the form of gravitational radiation. A timing model for the binary pulsar system PSR 1913+16 which includes both relativistic timing effects and the effects of conceivable rotational and tidal distortions of the pulsar\u27s companion star was developed. The deformation of the companion star would modify its Newtonian gravitational field which affects the orbit of the pulsar. In addition to secular perturbations discussed in previous work our analysis calculated the periodic perturbations that occur at harmonics of the pulsar\u27s orbital period. These characteristic periodic effects can generally indicate distinctively the presence of rotational and tidal distortions of the pulsar\u27s companion star. Our analysis shows that the timing effect of the gravitational red shift and second order Doppler shift and the effect of the Shapiro propagation delay of the pulse can be isolated from all these effects. They can be used to obtain a reliable estimate of the masses of the pulsar and its companion star whatever the nature of the companion. This new constraint can rule out any possibility that the pulsar\u27s companion is a helium star and it sharply constrains the rotational distortion of a conceivable white dwarf companion. Another subject of this thesis concerns with the deflection of star light by the gravitational field of the sun. The gravitational field generated by currents of matter within a body influences the deflection of light by the body. We show that in metric theories of gravity the Einstein equivalence principle implies a deeper connection than had been realized between this deflection and the Lense-Thirring dragging of inertial frames. (Abstract shortened with permission of author.
Digest of Proceedings: Farm Equipment Institute Industry Research Conference, May 27-29, 1959, Purdue University, Lafayette, Indiana
No full textDesign of a GaInP/GaAs tandem solar cell for maximum daily, monthly, and yearly energy output
No full textSolar concentrator cells are typically designed for maximum efficiency under the AM1.5d standard spectrum. While this methodology does allow for a direct comparison of cells produced by various laboratories, it does not guarantee maximum daily, monthly, or yearly energy production, as the relative distribution of spectral energy changes throughout the day and year. It has been suggested that achieving this goal requires designing under a nonstandard spectrum. In this work, a GaInP/GaAs tandem solar cell is designed for maximum energy production by optimizing for a set of geographically-dependent solar spectra using detailed numerical models. The optimization procedure focuses on finding the best combination of GaInP bandgap and GaInP and GaAs sub-cell absorber layer thicknesses. It is shown that optimizing for the AM1.5d standard spectrum produces nearly maximum yearly energy. This result simplifies the design of a dual-junction device considerably, is independent of the optical concentration up to at least 500 suns, and holds for a wide range of geographic locations. The simulation results are compared to those obtained using a more traditional, ideal-diode model. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI:10.1117/1.3633244
A defense of the ambiguity theory of \u27knows\u27
No full textIn recent years, questions regarding the truth conditions of knowledge ascriptions (sentences of the form ‘S knows that P’ where S is a subject and P a proposition) and knowledge denials (sentences of the form ‘S doesn’t know that P’) have been at the fore of a certain sector of analytic epistemology and philosophy of language. These questions include “How do we determine the truth conditions of a particular knowledge ascription or denial?”, “What sorts of factors are relevant in this determination?”, and “Is context among the relevant factors in a non-trivial way, and if so, how?” A variety of proposals have been generated in order to answer these questions—including proposals that offer a primarily semantic response. However, very little attention has been given to the possibility that part of the best answer to these questions about the truth conditions for knowledge ascriptions and denials is to posit that ‘knowledge’, ‘knows’, and their cognate terms are ambiguous. This dissertation offers a defense of a proposal along these lines. More specifically this dissertation is a defense of the ambiguity theory of ‘knows’. The ambiguity theory of ‘knows’ is the view ‘knows’ and its cognates have more than one propositional sense (i.e. a sense that can properly be used in ‘knows that’ constructions) and that which sense of ‘knows’ is being employed in a knowledge ascription or denial plays a role in fixing the truth conditions of a knowledge ascription (in virtue of contributing to the meaning of the claim). In this dissertation, this claim is defended first by making clear how the ambiguity theory differs from others proposals on offer, second, by comparing the ambiguity theory to other leading proposals and arguing that the ambiguity theory fares as well if not better, and third, by providing other independent arguments in favor of the view. My hope is that the work done here will give the ambiguity theory a more prominent presence in the relevant philosophical debates
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