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Wyszukujesz frazę "lifetime" wg kryterium: Temat


Tytuł:
Implementation of mathematical model of thermal behavior of electronic components for lifetime estimation based on multi-level simulation
Autorzy:
Frivaldsky, M.
Pridala, M.
Drgona, P.
Tematy:
electrolytic capacitor
lifetime model
lifetime estimation
system-level simulation
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/140808.pdf  Link otwiera się w nowym oknie
Opis:
The main purpose of the paper is the proposal of multi-level simulation, suited for the evaluation of the lifetime of critical electronic devices (electrolytic capacitors). The aim of this issue is to imagine about the expected operation of complex and expensive power electronic systems, when the failure of the most critical component occurs. For that reason, various operational conditions and various physical influences must be considered (e.g. mechanical, humidity, electrical, heat stress), where nonlinearities are naturally introduced. Verification of the proposal is given, whereby the life-time estimation of an electrolytic capacitor operated in a DC-DC converter during various operational conditions is shown. At this point electrical and heat stress is considered for lifetime influence. First, the current state in the field of mathematical modeling of the lifetime for electrolytic capacitors, considering main phenomena is introduced. Next, individual sub-models for multi-level simulation purposes are developed, including a thermal simulation model and electrical simulation model. Several complexities of individual models are mutually compared in order to evaluate their accuracy and suitability for further use. Proper simulation tools have been mutually linked and data transfer was secured, in order to have the possibility of investigation of a lifetime depend on the changes of various variables.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
SPLIT : statistical positronium lifetime image reconstruction via time-thresholding
Autorzy:
Qi, Jinyi
Shopa, Roman Y.
Stępień, Ewa
Huang, Bangyan
Moskal, Paweł
Ariño-Estrada, Gerard
Li, Tiantian
Dulski, Kamil
Opis:
Positron emission tomography (PET) is a widely utilized medical imaging modality that uses positron-emitting radiotracers to visualize biochemical processes in a living body. The spatiotemporal distribution of a radiotracer is estimated by detecting the coincidence photon pairs generated through positron annihilations. In human tissue, about 40% of the positrons form positroniums prior to the annihilation. The lifetime of these positroniums is influenced by the microenvironment in the tissue and could provide valuable information for better understanding of disease progression and treatment response. Currently, there are few methods available for reconstructing high-resolution lifetime images in practical applications. This paper presents an efficient statistical image reconstruction method for positronium lifetime imaging (PLI). We also analyze the random triple-coincidence events in PLI and propose a correction method for random events, which is essential for real applications. Both simulation and experimental studies demonstrate that the proposed method can produce lifetime images with high numerical accuracy, low variance, and resolution comparable to that of the activity images generated by a PET scanner with currently available time-of-flight resolution.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Multi-Method Analysis
Autorzy:
Tomczyk, Przemysław
Wydawca:
IGI Global
Cytata wydawnicza:
Tomczyk P. Multi-Method Analysis [in:] Ghorbani A, Takhar A, (Eds). Market Research Methodologies: Qualitative and Multi-Method Approaches, IGI Global, 2015, pp. 184-198
Opis:
Przemysław Tomczyk
Multi-Method Analysis (MMA) can be understood as an interdisciplinary approach to the triangulation of research results or deepening of knowledge gained as a result of classical hypotheses testing by means of statistical analysis. In this case, the synergy effect obtained by using MMA as a combination of the quantitative (survey research) and qualitative (In-Depth Interviews – IDI) analysis is presented. To achieve the empirical bases of the study, a theoretical model is used as a marketing management example. The model refers to firm performance as a result of customer lifetime value management. The essence of the case study is to present the whole research to illustrate the researcher’s way of thinking from conceptual model development through quantitative hypothesis testing and qualitative explanation. The research was conducted from 2012 – 2013 in the insurance industry in Poland.
Dostawca treści:
Repozytorium Centrum Otwartej Nauki
Inne
Tytuł:
Numerical investigation of creep behaviour of high-temperature steam turbine compone
Autorzy:
Banaszkiewicz, M.
Tematy:
creep
lifetime assessment
steam turbine
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Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/175375.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents a model for creep basing on the so-called characteristic creep strain. It illustrates its application in computations of old steam turbines components. The presented model is a modification of the Norton model which relates the stress exponent to the creep rupture strength and current stress. Creep strain is a function of the above two quantities, i.e., rupture strength and current stress, and acharacteristic creep strain which is material constant for a given time and temperature. Computational examples regard the rotating and pressure components analysed using the finite element method.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Methodology of threat autonomous assessment and forecasting the lifetime of the marine structure
Autorzy:
Murawski, L.
Tematy:
monitoring systems
non-destructive tests
ship structures lifetime prediction
damage identification
damage localization
lifetime forecasting
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/245864.pdf  Link otwiera się w nowym oknie
Opis:
Structural Health Monitoring (SHM) is a natural extension and supplement of Non-Distractive Tests (NDT). Structure assessment during periodical NDT tests is performed by highly trained human team. However, during long sea voyage, ship crew has no knowledge and possibility for detailed assessment and, what is more, has no knowledge lifetime predicting of ship structure. SHM systems should have good designed sensors types, distribution, and automatic recording unit. However, most important (and most difficult for designing) is autonomous and self-contained procedures for marine structures hazard assessment. In the paper, basic assumptions for numerical algorithms of signal processing, damage identification and localization, threat assessment and forecasting of structure lifetime are presented. SHM systems can be based on several different measurements techniques like: comparative vacuum monitoring, electromagnetic layer, Lamb waves, vibration based methods, acoustic emission, and fibre optics. Last three methods are most promising in the marine environment, according to the author experience. Global ship hull deformation should be monitored as quasi-continuous measurements. Optical Time-Domain Reflectometer method (OTDR) is planned by author for hull global deformation monitoring. Some local strain-stress concentration of hull structure and propulsion system bearings' reactions will be monitored by Fibre Bragg Grating (FBG) sensors. Both techniques (OTDR and FBG) have been shortly described in the paper.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The method of estimating lifetimes of aircraft devices operating under ageing-attributable wearing conditions
Autorzy:
Ważny, M.
Tematy:
reliability
lifetime
destructive processes
permissible condition
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Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:
https://bibliotekanauki.pl/articles/281271.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents a probabilistic method of assessing lifetimes of selected structural components or assemblies of devices/systems affected by destructive processes that occur during aircraft operation. Reliability status of the device is evaluated by means of diagnostic or operational parameters. It is assumed that these devices (systems, assemblies) operate reliably if effects of wear and tear processes described by diagnostic parameters do not exceed boundary conditions/regimes. From the mathematical aspect, the method has been based on difference equations from which, when rearranged, a partial differential equation of the Fokker-Planck type is derived. A density function of the component wearing is a particular solution to this equation. With the density function of the component wearing applied, after suitable rearrangements, one can determine a density function of time for the exceeding the boundary condition. Now, with the density function of time of reaching the boundary condition found, and after rearrangement of this function, one receives dependences that can be applied to determine lifetime of the device given consideration. An example at the end of the paper illustrates how this method can be applied to analyse an airborne sighting system.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonance production in heavy ion collisions
Autorzy:
Markert, Ch.
Tematy:
resonance
strangeness
baryon
freeze-out
lifetime
fireball
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Wydawca:
Instytut Chemii i Techniki Jądrowej
Powiązania:
https://bibliotekanauki.pl/articles/146392.pdf  Link otwiera się w nowym oknie
Opis:
Resonances and their decay products may interact strongly with the hadrons in the fireball medium from the time of chemical freeze-out until the system breaks up at kinetic freeze-out. In order to try to further our understanding of the evolution and expansion of this hot and dense medium we compare resonance particle yields and spectra from elementary p+p and heavy ion collisions.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A model for service life control of selected device systems
Autorzy:
Zieja, M.
Ważny, M.
Tematy:
reliability
unreliability
durability
service lifetime
destructive processes
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Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/259281.pdf  Link otwiera się w nowym oknie
Opis:
This paper presents a way of determining distribution of limit state exceedence time by a diagnostic parameter which determines accuracy of maintaining zero state. For calculations it was assumed that the diagnostic parameter is deviation from nominal value (zero state). Change of deviation value occurs as a result of destructive processes which occur during service. For estimation of deviation increasing rate in probabilistic sense, was used a difference equation from which, after transformation, Fokker-Planck differential equation was obtained [4, 11]. A particular solution of the equation is deviation increasing rate density function which was used for determining exceedance probability of limit state. The so-determined probability was then used to determine density function of limit state exceedance time, by increasing deviation. Having at disposal the density function of limit state exceedance time one determined service life of a system of maladjustment. In the end, a numerical example based on operational data of selected aircraft [weapon] sights was presented. The elaborated method can be also applied to determining residual life of shipboard devices whose technical state is determined on the basis of analysis of values of diagnostic parameters.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Survey of Multi-Objective Deployment in Wireless Sensor Networks
Autorzy:
Marks, M.
Tematy:
coverage
lifetime
placement
positioning
wireless sensor network
Pokaż więcej
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/308483.pdf  Link otwiera się w nowym oknie
Opis:
The major challenge in designing wireless sensor networks (WSNs) is to find tradeoff between the desired and contrary requirements for the lifetime, coverage or cost while coping with the computation, energy and communication constraints. This paper examines the optimal placement of nodes for a WSN. It is impossible to consider the deployment of the nodes separately from WSNs applications. We highlight the properties of WSNs applications that determine the placement problem. We identify and enumerate the various objectives that should be considered. The paper provides an overview and concentrates on multi-objective strategies, their assumptions, optimization problem formulation and results.
Dostawca treści:
Biblioteka Nauki
Artykuł

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