scholarly journals OPERATING CONDITIONS OF SPACE CHIPS

2021 ◽  
Author(s):  
V. Zolnikov ◽  
N. Gamzatov ◽  
I. Strukov ◽  
M. Solodilov ◽  
Ekaterina Grosheva
Keyword(s):  
Radiation Resistance ◽  
Radiation Effects ◽  
Operating Conditions ◽  
New Models ◽  
Physical Effects ◽  
Physical Phenomena

The issues of creating modern microelectronics for special purposes and the conditions of its operation are considered. The trends in the development of space-purpose microcircuits and their influence on radiation resistance are determined. The paper presents the main physical phenomena that dominate among the radiation effects in recent years. Reducing the characteristic sizes of VLSI elements leads to the appearance of new physical effects, for which it is necessary to develop new models, or improve existing ones.

Physical Realization of Generic-Element Parameters in Model Updating

2002 ◽  
Vol 124 (4) ◽  
pp. 628-633 ◽  
Author(s):  
H. Ahmadian ◽  
J. E. Mottershead ◽  
M. I. Friswell
Keyword(s):  
Model Updating ◽  
Finite Element Models ◽  
Physical Realization ◽  
Governing Equations ◽  
Stiffness Matrices ◽  
Model Predictions ◽  
Physical Effects ◽  
Realization Process ◽  
Physical Phenomena ◽  
Selection Of

The selection of parameters is most important to successful updating of finite element models. When the parameters are chosen on the basis of engineering understanding the model predictions are brought into agreement with experimental observations, and the behavior of the structure, even when differently configured, can be determined with confidence. Physical phenomena may be misrepresented in the original model, or may be absent altogether. In any case the updated model should represent an improved physical understanding of the structure and not simply consist of unrepresentative numbers which happen to cause the results of the model to agree with particular test data. The present paper introduces a systematic approach for the selection and physical realization of updated terms. In the realization process, the discrete equilibrium equation formed by mass, and stiffness matrices is converted to a continuous form at each node. By comparing the resulting differential equation with governing equations known to represent physical phenomena, the updated terms and their physical effects can be recognized. The approach is demonstrated by an experimental example.

scholarly journals Designing radiation protection for the scientific equipment complex of the Earth’s remote sensing spacecraft

2019 ◽  
Author(s):  
T.Sh. Kombaev ◽  
M.E. Artemov ◽  
I.V. Zefirov
Keyword(s):  
Radiation Protection ◽  
Radiation Resistance ◽  
Outer Space ◽  
Electronic Component ◽  
Operating Conditions ◽  
Absorbed Doses ◽  
Equipment Complex ◽  
Scientific Equipment ◽  
Radiation Conditions ◽  
Onboard Equipment

In the course of operation spacecrafts are exposed to ionizing radiation from outer space. The electronic component base (ECB) used in creating onboard radio-electronic equipment of universal space platforms does not always correspond to the external operating conditions in terms of radiation resistance for some spacecraft orbits due to a number of technical and/or economic reasons. One method to increase the radiation resistance of onboard equipment is to install additional mass protection in the form of screens on the whole equipment or local screens on individual critical radio and electronic components. The article describes the design of additional radiation protection of the geostationary spacecraft scientific equipment complex for adaptation to the radiation conditions of operation in orbits of the “Molniya” type. The solution of the problem involves several preliminary steps, namely: determining the radiation conditions for the spacecraft operation in the target orbit, estimating the local absorbed doses at the locations of the onboard equipment, estimating absorbed doses directly in the electronic component base of the equipment and analyzing the radiation resistance. Designing the radiation complex of scientific equipment was based on the values of the radiation resistance of the equipment and its components, as well as the calculated values of the local absorbed doses in the components

scholarly journals Nanodiamonds as a state-of-the-art material for enhancing the gamma radiation resistance properties of polymeric membranes

2020 ◽  
Vol 2 (3) ◽  
pp. 1214-1227 ◽  
Author(s):  
Amita Bedar ◽  
Nitesh Goswami ◽  
Amit K. Singha ◽  
Virendra Kumar ◽  
Anil K. Debnath ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
Radiation Resistance ◽  
Radiation Effects ◽  
State Of The Art ◽  
Polymeric Membranes ◽  
Polysulfone Membranes

Radiation effects on polysulfone membranes without and with incorporating nanodiamonds into the polysulfone matrix.

Correlations Hidden in Compressor Maps

2011 ◽  
Author(s):  
Joachim Kurzke
Keyword(s):  
High Speed ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Operating Conditions ◽  
Specific Work ◽  
Gas Generator ◽  
High Pressure Ratio ◽  
Map Adaptation ◽  
Physical Phenomena ◽  
Corrected Flow

Realistic compressor maps are the key to high quality gas turbine performance calculations. When modeling the performance of an existing engine then these maps are usually not known and must be approximated by adapting maps from literature to either measured data or to other available information. There are many publications describing map adaptation processes, simple ones and more sophisticated physically based scaling rules. There are also reports about using statistics, genetic algorithms, neural networks and even morphing techniques for re-engineering compressor maps. This type of methods does not consider the laws of physics and consequently the generated maps are valid at best in the region in which they have been calibrated. This region is frequently very narrow, especially in case of gas generator compressors which run in steady state always on a single operating line. This paper describes which physical phenomena influence the shape of speed and efficiency lines in compressor maps. For machines operating at comparatively low speeds (so that the flow into each stage is subsonic), there is usually considerable range between choke and stall corrected flow. As the speed of the machine is increased the range narrows. For high-speed stages with supersonic relative flow into the rotor the efficiency maximum is where the speed line turns over from vertical to lower than maximum corrected flow. At this operating condition the shock is about to detach from the leading edge of the blades. The flow at a certain speed can also be limited by choking in the compressor exit guide vanes. For high pressure ratio single stage centrifugal compressors this is a normal case, but it can also happen with low pressure ratio multistage boosters of turbofan engines, for example. If the compressor chokes at the exit, then the specific work remains constant along the speed line while the overall pressure ratio varies and that generates a very specific shape of the efficiency contour lines in the map. Also in other parts of the map, the efficiency varies along speed lines in a systematic manner. Peculiar shapes of specific work and corrected torque lines can reveal physically impossibilities that are difficult to see in the standard compressor map pictures. Compressor maps generated without considering the inherent physical phenomena can easily result in misleading performance calculations if used at operating conditions outside of the region where they have been calibrated. Whatever map adaptation method is used: the maps created in such a way should be checked thoroughly for violations of the underlying laws of compressor physics.

The effect of nuclear radiation on explosives

1958 ◽  
Vol 246 (1245) ◽  
pp. 219-225 ◽  
Keyword(s):  
Thermal Stability ◽  
Radiation Resistance ◽  
Ignition Temperature ◽  
Radiation Effects ◽  
Low Energy ◽  
Nuclear Radiation ◽  
Mechanical Sensitivity ◽  
Relative Resistance ◽  
Chemical Structures ◽  
Resonance Properties

The results of a study to determine the relative resistance of a number of explosives to effeets of low-energy γ -rays will be presented. The data obtained from irradiating the materials at several temperatures by the 0.41 MeV γ -quantum emitted by 198 Au demonstrate that no obvious correlation exists between the radiation resistance of explosives and their thermal stability, mechanical sensitivity or ignition temperature. In view of their well-known explosive behaviour, the resistance of explosives to irradiation decomposition is surprising. In some cases chemical instability during irradiation is detectable with difficulty even at doses of 10 6 r. It is evident from the data as well, that the chemical structures in question exhibit a varied resistance to radiation effects and suggest that resonance properties of certain molecules contribute markedly to radiation resistance.

Pre Test Calculations on TOPFLOW PTS Experiment With NEPTUNE_CFD Code

2011 ◽  
Author(s):  
A. Martin ◽  
C. Raynaud ◽  
P. Pe´turaud ◽  
C. Heib ◽  
F. Dubois ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Test Procedure ◽  
Operating Conditions ◽  
Experimental Program ◽  
Phase Flow ◽  
Two Phase ◽  
Loss Of Coolant Accident ◽  
Flow Configurations ◽  
Definition Of ◽  
Physical Phenomena

Hypothetical Small Break Loss Of Coolant Accident is identified as one of the most severe transients leading to a potential huge Pressurized Thermal Shock on the Reactor Pressure Vessel (RPV). This may result in two-phase flow configurations in the cold legs, according to the operating conditions, and to reliably assess the RPV wall integrity, advanced two-phase flow simulations are required. Related needs in development and/or validation of these advanced models are important, and the ongoing TOPFLOW-PTS experimental program was designed to provide a well documented data base to meet these needs. This paper focuses on pre-test NEPTUNE_CFD simulations of TOPFLOW-PTS experiments; these simulations were performed to (i) help in the definition of the test matrix and test procedure, and (ii) check the presence of the different key physical phenomena at the mock-up scale.

scholarly journals 3D unsteady turbulent flow analysis in a Francis turbine runner at nominal and off-design operating conditions

2004 ◽  
Vol 26 (3) ◽  
pp. 148-156
Author(s):  
Pham Thi Kim Loan ◽  
Bui Van Ga
Keyword(s):  
Turbulent Flow ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Design Flow ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Medium Size ◽  
Turbine Runner ◽  
Design Values ◽  
Physical Phenomena

This paper presents the use of a commercial Navier-Stokes turbulent flow code (FLUENT) as a mean to evaluate the behavior of a Francis turbine runner for the design and off-design conditions. The flow in the runner is analyzed numerically at different operating points. The numerical results permit to observe physical phenomena in the runner that are important in the process of hydraulic turbo machinery design. Values of different velocity components in the flow, blade pressure distribution ... given by the model are compared with experimental data at nominal and off-design flow conditions. Computer resource involves in the flow analysis should be compatible with the need of design process of a runner. Therefore 12 hours of CPU time can be considered as acceptable for calculating at each operating point on a computer workstation of medium size power.

scholarly journals Analysis of numerical instability of centrifugal pumps operational characteristics

2021 ◽  
Vol 4 (4) ◽  
pp. 357-364
Author(s):  
Andrej Lipej
Keyword(s):  
Accurate Result ◽  
Operating Regime ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Operational Characteristics ◽  
Load Regime ◽  
Water Turbines ◽  
Physical Phenomena ◽  
Operating Regimes ◽  
Dynamic Phenomena

In recent years, computational fluid dynamics has been increasingly used in the development of various types of rotating machines. In the case of water turbines and pumps, a large number of researches have been published recently, related to the use of different numerical methods for prediction of efficiency, cavitation characteristics and different dynamic phenomena. For basic analysis an accurate result near the optimal operating regime is sufficient, but for detailed analysis the numerical analyses in the wider field of operating conditions are necessary. Thus, we encounter some otherwise known physical phenomena that occur in the part load and full load regime. In these areas, due to the nature of the flow, various non-stationary phenomena occur that are dominant for such operating regimes. In this paper, the problems that arises if we consider only stationary results and some recommendations to avoid later problems in the operation of centrifugal pumps are presented.

scholarly journals Comparing Alternative Jet Fuel Dependencies Between Combustors of Different Size and Mixing Approaches

2021 ◽  
Vol 9 ◽  
Author(s):  
Randall C. Boehm ◽  
Jennifer G. Colborn ◽  
Joshua S. Heyne
Keyword(s):  
Evaluation Process ◽  
Jet Fuel ◽  
Operating Conditions ◽  
Aviation Fuel ◽  
Practical Significance ◽  
Performance Trends ◽  
Feature Importance ◽  
Physical Phenomena ◽  
Alternative Jet Fuel ◽  
Comparable Size

Analyses used to reveal fuel dependencies on lean blow out and ignition at specific operating conditions in specific combustors show inconsistent trends with each other. Such variety is however consistent with the occurrence of transitions between the governing physical phenomena as the ratios between evaporation, mixing, or chemical time scales with their respective residence times also vary with specific operating conditions and combustor geometry. It is demonstrated here that the fuel dependencies on LBO in a large, single-cup, swirl-stabilized, rich-quench-lean combustor varies with operating conditions such that a feature importance match is attained to fuel dependencies observed in a much smaller combustor at one end of the tested range, while a qualitative match to fuel dependencies observed in a lean, premixed, swirler-stabilized combustor of comparable size at the other end of the tested range. The same reference combustor, when tested at cold conditions, is shown to exhibit similar fuel dependencies on ignition performance as the much smaller combustor, when tested at both cold and warm conditions. The practical significance of these findings is that a reference rig, such as the Referee Rig, can capture fuel performance trends of proprietary industry combustors by tailoring the inlet air and fuel temperatures of the tests. It is, therefore, a trustworthy surrogate for screening and evaluating sustainable aviation fuel candidates, reducing the dependency on proprietary industrial combustors for this purpose, thereby increasing transparency within the evaluation process while also expediting the process and reducing cost and fuel volume.

Modeling and Validation of a Pressure-Wave Supercharger Using a Finite Difference Method

2004 ◽  
Author(s):  
Peter Spring ◽  
Janusz Piechna ◽  
Christopher H. Onder
Keyword(s):  
Finite Difference ◽  
Pressure Wave ◽  
Degrees Of Freedom ◽  
Combustion Engine ◽  
Independent Set ◽  
Operating Conditions ◽  
Wave Rotor ◽  
General Applicability ◽  
Measurement Results ◽  
Physical Effects

Modern pressure-wave supercharging devices offer many degrees of freedom in operation with an internal combustion engine. Both the independent set of wave rotor speed and the offset between air and gas casing can guarantee optimum efficiency even under problematic operating conditions. However, these systems require very accurate models that can reproduce the physical effects occurring in the charger. In this paper, a finite difference tool is presented where a set of Euler-type partial differential equations is numerically solved to simulate the 1-dimensional unsteady gas dynamics in the cell wheel, taking into account such phenomena as leakage, heat transfer, and friction. In order to show its general applicability, the model was validated with measurement results from two different PWS-boosted engines on a test rig.

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