2,364 research outputs found
Thermal control systems for low-temperature heat rejection on a lunar base
One of the important issues in the lunar base architecture is the design of a Thermal Control System (TCS) to reject the low temperature heat from the base. The TCS ensures that the base and all components inside are maintained within the operating temperature range. A significant portion of the total mass of the TCS is due to the radiator. Shading the radiation from the sun and the hot lunar soil could decrease the radiator operating temperature significantly. Heat pumps have been in use for terrestrial applications. To optimize the mass of the heat pump augmented TCS, all promising options have to be evaluated and compared. Careful attention is given to optimizing system operating parameters, working fluids, and component masses. The systems are modeled for full load operation
Thermal control systems for low-temperature heat rejection on a lunar base
In this report, Rankine-cycle heat pumps and absorption heat pumps (ammonia-water and lithium bromide-water) have been analyzed and optimized for a lunar base cooling load of 100 kW. For the Rankine cycle, a search of several commonly used commercial refrigerants provided R11 and R717 as possible working fluids. Hence, the Rankine-cycle analysis has been performed for both R11 and R717. Two different configurations were considered for the system--one in which the heat pump is directly connected to the rejection loop and another in which a heat exchanger connects the heat pump to the rejection loop. For a marginal increase in mass, the decoupling of the rejection loop and the radiator from the heat pump provides greater reliability of the system and better control. Hence, the decoupled system is the configuration of choice. The optimal TCS mass for a 100 kW cooling load at 270 K was 5940 kg at a radiator temperature of 362 K. R11 was the working fluid in the heat pump, and R717 was the transport fluid in the rejection loop. Two TCS's based on an absorption-cycle heat pump were considered, one with an ammonia-water mixture and the other with a lithium bromide-water mixture as the working fluid. A complete cycle analysis was performed for these systems. The system components were approximated as heat exchangers with no internal pressure drop for the mass estimate. This simple approach underpredicts the mass of the systems, but is a good 'optimistic' first approximation to the TCS mass in the absence of reliable component mass data. The mass estimates of the two systems reveal that, in spite of this optimistic estimate, the absorption heat pumps are not competitive with the Rankine-cycle heat pumps. Future work at the systems level will involve similar analyses for the Brayton- and Stirling-cycle heat pumps. The analyses will also consider the operation of the pump under partial-load conditions. On the component level, a capillary evaporator will be designed, built, and tested in order to investigate its suitability in lunar base TCS and microgravity two-phase applications
Electrospinning and solution blow spinning productions methods of polymer scaffolds for tissue engineering
Application of image recognition theory in non-destructive radiation testing of materials quality used in extreme conditions
ΠΠ»Ρ ΠΎΠ±Π½Π°ΡΡΠΆΠ΅Π½ΠΈΡ Π΄Π΅ΡΠ΅ΠΊΡΠΎΠ² ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»ΠΎΠ² ΠΈ Π΄Π΅ΡΠ°Π»Π΅ΠΉ ΠΊΠΎΡΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
Π°ΠΏΠΏΠ°ΡΠ°ΡΠΎΠ² ΠΈΡΠΏΠΎΠ»ΡΠ·ΡΠ΅ΡΡΡΡΠ°Π΄ΠΈΠ°ΡΠΈΠΎΠ½Π½ΡΠΉ ΠΌΠ΅ΡΠΎΠ΄ Π½Π΅ΡΠ°Π·ΡΡΡΠ°ΡΡΠ΅Π³ΠΎ ΠΊΠΎΠ½ΡΡΠΎΠ»Ρ. ΠΠ±ΡΠ°Π±ΠΎΡΠΊΠ° ΠΈΠ·ΠΎΠ±ΡΠ°ΠΆΠ΅Π½ΠΈΠΉ, ΠΏΠΎΠ»ΡΡΠ°Π΅ΠΌΡΡ
ΡΡΠΈΠΌ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ, ΠΏΡΠΎΠ²ΠΎΠ΄ΠΈΡΡΡ Ρ ΠΏΠΎΠΌΠΎΡΡΡ ΡΠΏΠ΅ΡΠΈΠ°Π»ΡΠ½ΡΡ
Π°Π»Π³ΠΎΡΠΈΡΠΌΠΎΠ². Π ΡΠ°Π±ΠΎΡΠ΅ ΠΎΠ±ΠΎΡΠ½ΠΎΠ²Π°Π½Π° Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΡ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ Π½Π΅ΠΉΡΠΎΡΠ΅ΡΠ΅Π²ΠΎΠ³ΠΎ ΠΌΠ΅ΡΠΎΠ΄Π° ΠΈ ΠΏΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ Π°Π»Π³ΠΎΡΠΈΡΠΌ Π½Π° Π΅Π³ΠΎ ΠΎΡΠ½ΠΎΠ²Π΅ Π΄Π»Ρ ΡΠ°ΡΠΏΠΎΠ·Π½Π°Π²Π°Π½ΠΈΡ ΠΎΠ±ΡΠ°Π·ΠΎΠ².The radiation method of nondestructive testing is used for the detection of defects in materials and components of spacecraft. Processing of the images, obtained by this method, is carried out using specialized algorithms. In the paper the possibility of using neural networks method is considered and the algorithm for image recognition based on it is suggested
Thermal control systems for low-temperature heat rejection on a lunar base
One of the important issues in the design of a lunar base is the thermal control system (TCS) used to reject low-temperature heat from the base. The TCS ensures that the base and the components inside are maintained within an acceptable temperature range. The temperature of the lunar surface peaks at 400 K during the 336-hour lunar day. Under these circumstances, direct dissipation of waste heat from the lunar base using passive radiators would be impractical. Thermal control systems based on thermal storage, shaded radiators, and heat pumps have been proposed. Based on proven technology, innovation, realistic complexity, reliability, and near-term applicability, a heat pump-based TCS was selected as a candidate for early missions. In this report, Rankine-cycle heat pumps and absorption heat pumps (ammonia water and lithium bromide-water) have been analyzed and optimized for a lunar base cooling load of 100 kW
Π’Π΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΡΠ΅ ΡΠ΅ΠΆΠΈΠΌΡ ΡΠ°Π±ΠΎΡΡ ΡΠ²ΡΠ»ΠΎΠ² ΡΠ΅Π°ΠΊΡΠΎΡΠ° ΠΠ Π’-Π’
ΠΡΠΈΠ²Π΅Π΄Π΅Π½Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΡΠ΅ΠΏΠ»ΠΎΡΠΈΠ·ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ°ΡΡΠ΅ΡΠΎΠ² Π°ΠΊΡΠΈΠ²Π½ΠΎΠΉ Π·ΠΎΠ½Ρ ΡΠ΅Π°ΠΊΡΠΎΡΠ° ΠΠ Π’-Π’. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ ΠΏΡΠΈ Π½ΠΎΠΌΠΈΠ½Π°Π»ΡΠ½ΠΎΠΉ ΠΌΠΎΡΠ½ΠΎΡΡΠΈ ΡΠ΅Π°ΠΊΡΠΎΡΠ° ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΡΠ΅ ΡΠ΅ΠΆΠΈΠΌΡ ΡΠ²ΡΠ»ΠΎΠ² ΡΠΊΠ»Π°Π΄ΡΠ²Π°ΡΡΡΡ Π² ΠΏΡΠ΅Π΄Π΅Π»ΡΠ½ΡΠ΅ Π·Π½Π°ΡΠ΅Π½ΠΈΡ ΠΈ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΡΡ ΡΡΠ΅Π±ΠΎΠ²Π°Π½ΠΈΡΠΌ ΡΠ΅Ρ
Π½ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΠ±ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΈΡ Π±Π΅Π·ΠΎΠΏΠ°ΡΠ½ΠΎΡΡΠΈ
Neuroligins determine synapse maturation and function
Synaptogenesis, the generation and maturation of functional synapses between nerve cells, is an essential step in the development of neuronal networks in the brain. It is thought to be triggered by members of the neuroligin family of postsynaptic cell adhesion proteins, which may form transsynaptic contacts with presynaptic alpha- and beta-neurexins and have been implicated in the etiology of autism. We show that deletion mutant mice lacking neuroligin expression die shortly after birth due to respiratory failure. This respiratory failure is a consequence of reduced GABAergic/glycinergic and glutamatergic synaptic transmission and network activity in brainstem centers that control respiration. However, the density of synaptic contacts is not altered in neuroligin-deficient brains and cultured neurons. Our data show that neuroligins are required for proper synapse maturation and brain function, but not for the initial formation of synaptic contacts
The 2001 Mars In-Situ-Propellant-Production Precursor (MIP) Flight Demonstration
The successful performance of the five individual demonstrations of MARS IN-SITU-PROPELLANT-PRODUCTION PRECURSOR (MIP) will provide both knowledge of and confidence in the reliability of this technology. At the completion of this flight demonstration, the MIP Team will be able to: a) recommend preferred hardware configurations for the intake and adsorption of carbon dioxide from the Martian atmosphere; b) understand the performance characteristics of zirconia cells to generate propellant-grade oxygen; c) understand long-term performance characteristics of advanced solar cells/arrays operated in the actual Mars environment; d) evaluate the functionality of methods to mitigate the deposition of airborne dust onto solar arrays; and e) recommend preferred hardware designs for innovative thermal management including the radiation of heat to the outside environment
Π Π΅Π·ΡΠ»ΡΡΠ°ΡΠΈΠ²Π½ΠΎΡΡΡ ΡΠΈΠ»ΠΎΠ²ΠΎΠΉ ΠΏΠΎΠ΄Π³ΠΎΡΠΎΠ²ΠΊΠΈ ΡΠΏΠΎΡΡΡΠΌΠ΅Π½ΠΎΠ² Π² Π°ΡΠ»Π΅ΡΠΈΡΠ΅ΡΠΊΠΈΡ Π²ΠΈΠ΄Π°Ρ ΡΠΏΠΎΡΡΠ°
Ultrashort laser sources with pulse durations of around a few or below 1 picosecond and average powers above 1 KW enable a new domain in precision machining. They enable extreme-precision cutting, ablation and drilling of even weakly absorbing materials, multi-component and multilayer systems
The contours of a new urban world? Megacity population growth and density since 1975
The problems posed by rapid and large-scale urbanisation are manifold, and are recognised in the UNβs New Urban Agenda; a declaration of intent that aims to meet such challenges head-on facilitated by the systematic tracking and analysis of global urban growth and change. In this context, the release in 2016 of new small area Global Human Settlement Layer (GHSL) data was said to represent a unique opportunity to facilitate comparative
global analyses of urban change dynamics and, perhaps somewhat idealistically, move forward progressive planning agendas. We therefore focus on population growth and
density in 30 major urban agglomerations using the GHSL in order to shed light on the scale and extent of global urbanisation over the past four decades and to interrogate the
potential role of the GHSL in tracking urban change
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