11,180 research outputs found
Computer program for a four-cylinder-Stirling-engine controls simulation
A four cylinder Stirling engine, transient engine simulation computer program is presented. The program is intended for controls analysis. The associated engine model was simplified to shorten computer calculation time. The model includes engine mechanical drive dynamics and vehicle load effects. The computer program also includes subroutines that allow: (1) acceleration of the engine by addition of hydrogen to the system, and (2) braking of the engine by short circuiting of the working spaces. Subroutines to calculate degraded engine performance (e.g., due to piston ring and piston rod leakage) are provided. Input data required to run the program are described and flow charts are provided. The program is modular to allow easy modification of individual routines. Examples of steady state and transient results are presented
Data Management Study, Volume 5. Appendix H - Contractor Data Package Logistics and Support /LS/ Final Report
Contractor data package for Voyager logistics and support in transportation, communications, supply, and maintenanc
Data management study, volume 5. Appendix F - Contractor data package test /TE/ and mission operations /MP/ Final report
Test and mission operations contractor data package for Voyager spacecraf
STI policy and governance in Sub-Saharan Africa: Fostering actors’ interactions in research and innovation
This study investigates science, technology, and innovation (STI) policy and governance in relation to research and innovation (R&I) ecosystems in Sub-Saharan Africa (SSA). To understand the implications of STI policy and governance on R&I, the authors focus on university, industry and government actors; using the Triple Helix and National Systems of Innovation approaches as analytical frameworks to guide the study. The authors identify a range of factors hindering R&I actors’ interactions, including gaps in STI governance responsibilities and accountabilities, policymaking and structural transitions, R&I management capacity and capability gaps. Based on the findings, they propose changes to policymaking and the governance of R&I in SSA, in addition to advancing innovative approaches such as ‘resource circulation’ in the context of knowledge, research and science infrastructure scarcity. The findings provide fresh insights into STI policy and governance frameworks, fostering actors’ interactions and supporting performance improvements in research, science and innovation systems across Africa
Study of the glass transition in the amorphous interlamellar phase of highly crystallized poly(ethylene terephthalate)
Poly(ethylene terephthalate) (PET) is a semi--crystalline polymer that can be
crystallized to different degrees heating from the amorphous state. Even when
primary crystallization has been completed, secondary crystallization can take
place with further annealing and modify the characteristics of the amorphous
interlamellar phase. In this work we study the glass transition of highly
crystallized PET and in which way it is modified by secondary crystallization.
Amorphous PET samples were annealed for 4 hours at temperatures between 140C
and 180C. The secondary crystallization process was monitored by differential
scanning calorimetry and the glass transition of the remaining interllamelar
amorphous phase was studied by Thermally Stimulated Depolarization Currents
measurements. Non--isothermal window polarization is employed to resolve the
relaxation in modes with a well--defined relaxation time that are subsequently
adjusted to several standard models. Analysis of experimental results, show
that cooperativity is reduced to a great extend in the interlamellar amorphous
regions. The evolution of the modes on crystallization temperature reveals that
large scale movements are progressively replaced by more localized ones, with
higher frequency, as crystallization takes place at higher temperatures. As a
consequence, the glass transition temperature of the amorphous interlamellar
phase tends to lower values for higher annealing temperatures. Evolution of
calorimetric scans of the glass transition are simulated from the obtained
results and show the same behaviour. The interpretation of these results in
terms of current views about secondary crystallization is discussed.Comment: 30 pages, 5 tables, 12 figures; figure 5 modifie
Supporting early career health investigators in Kenya: A qualitative study of HIV/AIDS research capacity building
Introduction: strategies to transfer international health research training programs to sub-Saharan African institutions focus on developing cadresof local investigators who will lead such programs. Using a critical leadership theory framework, we conducted a qualitative study of one program to understand how collaborative training and research can support early career investigators in Kenya toward the program transfer goal.Methods: We used purposive sampling methods and a semi-structured protocol to conduct in-depth interviews with US (N=5) and Kenyan (N=5)independent investigators. Transcripts were coded using a two-step process, and then compared with each other to identify major themes.Results: A limited local research environment, funding needs and research career mentorship were identified as major influences on early career researchers. Institutional demands on Kenyan faculty to teach rather than complete research restricted investigators' ability to develop research careers. This was coupled with lack of local funding to support research. Sustainable collaborations between Kenyan, US and other international investigators were perceived to mitigate these challenges and support early career investigators who would help build a robust local research environment for training. Conclusion: mutually beneficial collaborations between Kenyan and US investigators developed during training mitigate these challenges and build a supportive research environment for training. In these collaborations, early career investigators learn how to navigate the complex international research environment to build local HIV research capacity.Shared and mutually beneficial resources within international research collaborations are required to support early career investigators and plans to transfer health research training to African institutions
Stoichiometry control of sputtered CuCl thin films: Influence on ultraviolet emission properties
We demonstrate that the chemical composition of the sputtered CuCl thin films could be finely controlled by adjusting the bias to the substrate. The films deposited without any intentional bias were Cl rich (CuCl1+x), a bias of −22 V yielded stoichiometric CuCl, and a further increase in the negative bias resulted in Cl deficient films (CuCl1−x). The crystalline and optical properties were found to be associated with the chemical composition. Cl rich films showed a deep level green emission at around 515 nm in addition to ultraviolet (UV) excitonic emission. The stoichiometric films have higher optical quality, exhibiting a sharp UV emission at around 385 nm at room temperature, compared to nonstoichiometric samples. Visible luminescence related to deep level defects was not observed in the stoichiometric films. Changes in energy of the flux from the target and the subsequent ion bombardment on the substrate surface are correlated with the variations in chemical composition and their impact on the film microstructure and UV emission
Cloaked Facebook pages: Exploring fake Islamist propaganda in social media
This research analyses cloaked Facebook pages that are created to spread political propaganda by cloaking a user profile and imitating the identity of a political opponent in order to spark hateful and aggressive reactions. This inquiry is pursued through a multi-sited online ethnographic case study of Danish Facebook pages disguised as radical Islamist pages, which provoked racist and anti-Muslim reactions as well as negative sentiments towards refugees and immigrants in Denmark in general. Drawing on Jessie Daniels’ critical insights into cloaked websites, this research furthermore analyses the epistemological, methodological and conceptual challenges of online propaganda. It enhances our understanding of disinformation and propaganda in an increasingly interactive social media environment and contributes to a critical inquiry into social media and subversive politics
Finite Element Analysis of Elastomeric Seals for LIDS
Objective: Create a means of evaluating seals w/o prototypes. Motivation: Cost Prototype 54" seal approx.30k per year. Development time: 6 months lead time for a new seal design Many designs per day (solution time <1 minute) Understanding: Difficult to experimentally measure strains, contact pressure profile, stresses, displacement
Crossover Behavior in Burst Avalanches of Fiber Bundles: Signature of Imminent Failure
Bundles of many fibers, with statistically distributed thresholds for
breakdown of individual fibers and where the load carried by a bursting fiber
is equally distributed among the surviving members, are considered. During the
breakdown process, avalanches consisting of simultaneous rupture of several
fibers occur, with a distribution D(Delta) of the magnitude Delta of such
avalanches. We show that there is, for certain threshold distributions, a
crossover behavior of D(Delta) between two power laws D(Delta) proportional to
Delta^(-xi), with xi=3/2 or xi=5/2. The latter is known to be the generic
behavior, and we give the condition for which the D(Delta) proportional to
Delta^(-3/2) behavior is seen. This crossover is a signal of imminent
catastrophic failure in the fiber bundle. We find the same crossover behavior
in the fuse model.Comment: 4 pages, 4 figure
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