736 research outputs found
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Fabrication of PEM Fuel Cell Bipolar Plates by Indirect SLS
The paper presents a new manufacturing technique involving Selective Laser
Sintering (SLS) for proton exchange membrane fuel cell (PEMFC) bipolar plate
fabrication. A material system for bipolar plate fabrication was identified to satisfy both
the cell performance requirement and SLS operation restriction. Carbonization and liquid
epoxy infiltration are subsequently performed following the completion of SLS green
bipolar plate. The finished SLS bipolar plate showed impressive surface finish and
mechanical strength, and a single fuel cell was assembled with two SLS end plates and
membrane electrode assembly (MEA) in between. Various physical property tests were
performed with positive results. Fuel cell performance (voltage vs. current density,
voltage vs. time, etc.) will be assessed in the near future.Mechanical Engineerin
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Improvement of Electrical Conductivity of SLS PEM Fuel Cell Bipolar Plates
Previous work in this research demonstrated the feasibility of fabrication of proton
exchange membrane (PEM) fuel cell bipolar plates by an indirect selective laser sintering
(SLS) route. Properties of the SLS bipolar plate, such as flexural strength, corrosion
resistance and gas impermeability, etc. are quite promising and satisfactory. However,
initial results showed that there was still room for the improvement in electrical
conductivity. This paper summaries the strategies investigated in an effort to increase the
electrical conductivity, among which are: (1) infiltration of brown parts with conductive
polymer (2) addition of a liquid phenolic infiltration/re-curing step prior to final sealing
and (3) reduction of glassy carbon resistivity by curing process parameter control. Results
show that the electrical conductivity value may be improved from 80 S/cm to around 108
S/cm, which is equivalent to a 35% jump, when the phenolic infiltration/re-curing step is
applied before final epoxy sealing.Mechanical Engineerin
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Agile Product Testing with Constrained Prototypes
The means to acquire reliable functional information is a critical factor that differentiates product development time and cost. Thanks to advances in solid freeform
fabrication techniques, industries can produce geometrically complex parts within
dramatically reduced time and cost. Even though industries can save significant efforts by performing functional tests rapid prototypes, they still prefer full-scale product tests, especially in later design phases, due to inherent limitations in traditional
similarity methods (TSM). This paper describes a new method to perform reliable
functional tests with rapid prototypes that cannot be properly handled by the TSM.Mechanical Engineerin
The Stink Bugs (Hemiptera: Heteroptera: Pentatomidae) of Missouri
The stink bug (Hemiptera: Pentatomidae) fauna of Missouri was last treated more than 70 years ago. Since then, many more specimens have become available for study, substantial papers on regional faunas have been published, and many revisions and other taxonomic changes have taken place. As a consequence, 40% of the names from the previous Missouri state list have changed or the taxa have been removed. The fauna of stink bugs known from Missouri based on specimens from museums, other collections, and the literature is presented. Included for each species is a general overview of biological and ecological information, overall distribution, and local distribution among Missouri Natural Divisions. Also presented for Missouri specimens are biological label data and extreme dates of adult collection. All totaled, 57 species are now known from the state, eight of which represent new state records: Asopinae: Alcaeorrhynchus grandis (Dallas), Tylospilus acutissimus (Stål); Pentatominae: Banasa calva (Say), Banasa euchlora Stål, Cosmopepla intergressa (Uhler), Halyomorpha halys (Stål), Neottiglossa undata (Say); Podopinae: Amaurochrous brevitylus Barber and Sailer
Transforming Energy Networks via Peer to Peer Energy Trading: Potential of Game Theoretic Approaches
Peer-to-peer (P2P) energy trading has emerged as a next-generation energy
management mechanism for the smart grid that enables each prosumer of the
network to participate in energy trading with one another and the grid. This
poses a significant challenge in terms of modeling the decision-making process
of each participant with conflicting interest and motivating prosumers to
participate in energy trading and to cooperate, if necessary, for achieving
different energy management goals. Therefore, such decision-making process
needs to be built on solid mathematical and signal processing tools that can
ensure an efficient operation of the smart grid. This paper provides an
overview of the use of game theoretic approaches for P2P energy trading as a
feasible and effective means of energy management. As such, we discuss various
games and auction theoretic approaches by following a systematic classification
to provide information on the importance of game theory for smart energy
research. Then, the paper focuses on the P2P energy trading describing its key
features and giving an introduction to an existing P2P testbed. Further, the
paper zooms into the detail of some specific game and auction theoretic models
that have recently been used in P2P energy trading and discusses some important
finding of these schemes.Comment: 38 pages, single column, double spac
Policy Design for Controlling Set-Point Temperature of ACs in Shared Spaces of Buildings
Air conditioning systems are responsible for the major percentage of energy
consumption in buildings. Shared spaces constitute considerable office space
area, in which most office employees perform their meetings and daily tasks,
and therefore the ACs in these areas have significant impact on the energy
usage of the entire office building. The cost of this energy consumption,
however, is not paid by the shared space users, and the AC's temperature
set-point is not determined based on the users' preferences. This latter factor
is compounded by the fact that different people may have different choices of
temperature set-points and sensitivities to change of temperature. Therefore,
it is a challenging task to design an office policy to decide on a particular
set-point based on such a diverse preference set. As a result, users are not
aware of the energy consumption in shared spaces, which may potentially
increase the energy wastage and related cost of office buildings. In this
context, this paper proposes an energy policy for an office shared space by
exploiting an established temperature control mechanism. In particular, we
choose meeting rooms in an office building as the test case and design a policy
according to which each user of the room can give a preference on the
temperature set-point and is paid for felt discomfort if the set-point is not
fixed according to the given preference. On the other hand, users who enjoy the
thermal comfort compensate the other users of the room. Thus, the policy
enables the users to be cognizant and responsible for the payment on the energy
consumption of the office space they are sharing, and at the same time ensures
that the users are satisfied either via thermal comfort or through incentives.
The policy is also shown to be beneficial for building management. Through
experiment based case studies, we show the effectiveness of the proposed
policy.Comment: Journal paper accepted in Energy & Buildings (Elsevier
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Experimental Study of Selective Laser Sintering of Parmax
Selective Laser Sintering (SLS) has been used to successfully process crystalline
polymers, ceramics and metals. However, wide range of materials available and their
applications have acted as an impetus to expand the applications of SLS to different material
systems. This paper presents one such experimental study undertaken to explore the application
of SLS to process Parmax® polymers – a family of high performance amorphous poly pphenylenes. As a part of the collaborative study, various process parameters and material
formulations were tried out to ascertain the feasibility of the process and the initial results
obtained look promising. This paper lists the material formulations tested and process parameters
controlled. Also, analysis of the results of the experimental study and the outline of the next
phase of research to be undertaken have been described. This study was motivated by the
numerous applications of Parmax® in the electronics, defense and aerospace industries as well as
the goal to expand the applications and utility of SLS.Mechanical Engineerin
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