1,078,670 research outputs found
Active cooling requirements for propellant storage
Recent NASA and DOD mission models have indicated future needs for orbital cryogenic storage and supply systems. Two thermal control systems which show the greatest promise for improving propellant storage life were evaluated. One system was an open cycle thermodynamic vent type with a refrigeration system for partial hydrogen reliquefaction located at the LH2 tank and a vapor cooled shield for integrated and non-integrated tank designs to reduce boiloff. The other was a closed system with direct refrigeration at the LH2 tank. A reversed Brayton cycle unit was baselined for the propellant processor. It is concluded that: (1) reliquefaction systems are not attractive for minimizing propellant boiloff; (2) open cycle systems may not be economically attractive for long term storage; (3) a number of refrigeration systems are available to assist in the long term storage of cryogenic propellants; and (4) shields can significantly improve the performance of mechanical coolers
Development of lithium-thionyl chloride batteries for Centaur
Lithium thionyl chloride (LiSOCl2) primary cells and batteries have received considerable attention over the last several years because of their high theoretical specific energy and energy density. The objective was to develop a 300 wh/kg cell capable of safe operation at C/2 rate and active storage life for 5 to 10 years. This technology would replace other primary cell technologies in NASA applications mainly the silver zinc (AgZn) batteries presently in use. The LiSOCl2 system exceeds the capabilities of the AgZn in terms of specific energy of 300 wh/kg (compared with 100 wh/kg for AgZn), active storage life of 10 to 20 times the 3 to 6 months active storage and has a significantly lower projected cost
Active repositioning of storage units in Robotic Mobile Fulfillment Systems
In our work we focus on Robotic Mobile Fulfillment Systems in e-commerce
distribution centers. These systems were designed to increase pick rates by
employing mobile robots bringing movable storage units (so-called pods) to pick
and replenishment stations as needed, and back to the storage area afterwards.
One advantage of this approach is that repositioning of inventory can be done
continuously, even during pick and replenishment operations. This is primarily
accomplished by bringing a pod to a storage location different than the one it
was fetched from, a process we call passive pod repositioning. Additionally,
this can be done by explicitly bringing a pod from one storage location to
another, a process we call active pod repositioning. In this work we introduce
first mechanisms for the latter technique and conduct a simulation-based
experiment to give first insights of their effect
Electroactive micro and nanowells for optofluidic storage
This paper reports an optofluidic architecture which enables reversible trapping, detection and long term storage of spectrally multiplexed semiconductor quantum dot cocktails in electrokinetically active wells ranging in size from 200nm to 5μm. Here we describe the microfluidic delivery of these cocktails, fabrication method and principal of operation for the wells, and characterize the readout capabilities, storage and erasure speeds, internal spatial signal uniformity and potential storage density of the devices. We report storage and erase speeds of less than 153ms and 30ms respectively and the ability to provide 6-bit storage in a single 200nm well through spectral and intensity multiplexing. Furthermore, we present a novel method for enabling passive long term storage of the quantum dots in the wells by transporting them through an agarose gel matrix. We envision that this technique could find eventual application in fluidic memory or display devices
Electrodes for sealed secondary batteries
Self-supporting membrane electrode structures, in which active ingredients and graphite are incorporated in a polymeric matrix, improve performance of electrodes in miniature, sealed, alkaline storage batteries
Electronic switching circuit uses complementary non-linear components
Inherent switching properties of saturable inductors and storage diodes are combined to perform large variety of electronic functions, such as pulse shaping, gating, and multiplexing. Passive elements replace active switching devices in generation of complex waveforms
Active heat exchange system development for latent heat thermal energy storage
Various active heat exchange concepts were identified from among three generic categories: scrapers, agitators/vibrators and slurries. The more practical ones were given a more detailed technical evaluation and an economic comparison with a passive tube-shell design for a reference application. Two concepts selected for hardware development are a direct contact heat exchanger in which molten salt droplets are injected into a cooler counterflowing stream of liquid metal carrier fluid, and a rotating drum scraper in which molten salt is sprayed onto the circumference of a rotating drum, which contains the fluid heat sink in an internal annulus near the surface. A fixed scraper blade removes the solidified salt from the surface which has been nickel plated to decrease adhesion forces. Suitable phase change material (PCM) storage media with melting points in the temperature range of interest (250 C to 400 C) were investigated. The specific salt recommended for laboratory tests was a chloride eutectic (20.5KCl-24/5 NaCl-55.0MgCl 2% by wt.), with a nominal melting point of 385 C
Electrochemical monitoring of the storage or stabilization of archaeological copper based artefacts in sodium sesquicarbonate solutions
Archaeological copper-based artifacts recovered from wet and salty environments are often stored or stabilized in sodium sesquicarbonate solutions. Modification of the natural patina and development of active corrosion can occur during these processes, which implies the need for monitoring storage/stabilization processes. The focus of the study consists of examining how corrosion potential (Ecorr) measurements and voltammetric curves can contribute in providing information on the effectiveness of storage and stabilization treatments. Particular attention is given to side effects such as the transformation of the corrosion layers
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