Asymptotic Lifetime Research Articles

Constraints on the initial mass, age and lifetime of Saturn’s rings from viscous evolutions that include pollution and transport due to micrometeoroid bombardment

The Cassini spacecraft provided key measurements during its more than twelve year mission that constrain the absolute age of Saturn’s rings. These include the extrinsic micrometeoroid flux at Saturn, the volume fraction of non-icy pollutants in the rings, and a measurement of the ring mass. These observations taken together limit the ring exposure age to be ≲ a few 100 Myr if the flux was persistent over that time (Kempf et al., 2022). In addition, Cassini observations during the Grand Finale further indicate the rings are losing mass (Hsu et al., 2018; Waite et al., 2018) suggesting the rings are ephemeral as well. In a companion paper (Durisen and Estrada, 2022), we show that the effects of micrometeoroid bombardment and ballistic transport of their impact ejecta can account for these loss rates for reasonable parameter choices. In this paper, we conduct numerical simulations of an evolving ring in a systematic way in order to determine initial conditions that are consistent with these observations.We begin by revisiting the ancient massive ring scenario of Salmon et al. (2010). Here, we model not just the viscous evolution, but we subject the ring to pollution by micrometeoroid bombardment over the age of the Solar System. We find that regardless of initial mass, the ring always ends up with more pollutant than is currently observed, because the ring spends the majority of its lifetime at relatively low mass where it is most susceptible to darkening. We then show that models with initial disk masses of ∼1–3 Mimas masses reach volume fractions of pollutant consistent with the observed volume fractions of non-icy material in the A and B rings within a time scale of ∼ a few 100 Myr.Finally, we use the analysis of Durisen and Estrada (2022) to add the dynamical effects of meteoroid bombardment into the evolution equations, namely, mass loading and ballistic transport. The treatment of mass loading is exact, while ballistic transport is handled in an approximate way. Simulations show that: (1) mass loading and ballistic transport applied to an initially high optical depth annulus inevitably produce a lower density C ring analog interior to the annulus; and (2) high density rings subject to persistent micrometeoroid bombardment do not have an asymptotic mass but instead have an asymptotic lifetime much shorter than the age of the Solar System. This is because micrometeoroid bombardment and ballistic transport drive the dynamical evolution of the ring once viscosity weakens, indicating that the exposure age of the rings and their dynamical age are connected.

Bluetooth Mesh Energy Consumption: A Model.

The recent publication of the Bluetooth Mesh standard is a remarkable milestone in the evolution of Bluetooth Low Energy (BLE). As a new technology in the Internet of Things (IoT) market, it is crucial to investigate the performance of Bluetooth Mesh. However, while a fundamental feature of Bluetooth Mesh is its suitability for energy-constrained devices, this aspect has not yet been properly considered in the literature. In this paper, we model the current consumption, lifetime and energy cost per delivered bit of a battery-operated Bluetooth Mesh sensor node. The model is based on measurements performed on a real hardware platform. Evaluation results quantify the impact of crucial Bluetooth Mesh parameters. Among others, we have found that a sensor device running on a simple 235 mAh battery, and sending a data message every 10 s, can achieve a lifetime of up to 15.6 months, whereas the asymptotic lifetime is 21.4 months.

A Sigfox Energy Consumption Model.

Sigfox has become one of the main Low-Power Wide Area Network (LPWAN) technologies, as it has attracted the attention of the industry, academy and standards development organizations in recent years. Sigfox devices, such as sensors or actuators, are expected to run on limited energy sources; therefore, it is crucial to investigate the energy consumption of Sigfox. However, the literature has only focused on this topic to a very limited extent. This paper presents an analytical model that characterizes device current consumption, device lifetime and energy cost of data delivery with Sigfox. In order to capture a realistic behavior, the model has been derived from measurements carried out on a real Sigfox hardware module. The model allows quantifying the impact of relevant Sigfox parameters and mechanisms, as well as frame losses, on Sigfox device energy performance. Among others, evaluation results show that the considered Sigfox device, powered by a 2400 mAh battery, can achieve a theoretical lifetime of 1.5 or 2.5 years while sending one message every 10 min at 100 bit/s or 600 bit/s, respectively, and an asymptotic lifetime of 14.6 years as the message transmission rate decreases.

Planning Optimal Degradation Tests in Consideration of Budget and Statistical Accuracy at Different Stress Levels

Degradation testing is a useful technique for demonstrating the process of failure over time. The challenge when planning a test is to determine how many test units should be examined and how long the test should run in order to get sufficient data and reach the predefined reliability targets within the provided and/or available test budget. In this paper, a novel strategic workflow for identifying the sample size and the number of measurements during each test run in consideration of the accuracy and budget will be proposed. The number of sample sizes and the testing time are constantly adapted until the predetermined requirements are met. The presented work results in a treatment of a mechanical failure mode, i.e., pitting of transmission gears. The tool covers the determination of resources in a novel procedure using existing methods. We apply this degradation model to degradation signals obtained through the relatively time-consuming and cost-intensive accelerated testing of gears on a test bench. The results contain the optimal sample size, the number of inspections for each sample and the asymptotic lifetime and its variance coefficients.

Self-organized nanoclusters of semiconductor compounds on vicinal Si surfaces and its influence on carrier recombination in Si

The self-organized nanocluster ensembles of ZnSe, CdSe and PbS were grown by laser ablation on vicinal Silicon (111) surfaces. The properties of the layers were investigated by XPS (X-rays photoelectron spectroscopy) and Auger spectroscopy. The properties of the semiconductor-clustered layer on single Si crystal structure were investigated by deep level transient spectroscopy (DLTS) and by microwave absorption induced by light pulse excitation. The clustered layer and multilayer structure modified the recombination at the Si surface and created additional carrier capture centres. Absolute values of surface recombination rate, s, were determined by the method of asymptotic lifetime amplitude. An increase of s is caused by formation of PbS clusters, while for CdSe clusters, this dependence was found to be weaker. Structures with barriers or flat conduction bands were grown on the silicon surface using different doping concentrations of layers.

Study of recombination properties of neutron transmutation doped silicon wafers

The asymptotic lifetime dependency on temperature, excitation depth and intensity, and on continuous-wave bias illumination have been investigated for the simultaneous determination of the recombination parameters to characterize neutron transmutation doped silicon by the microwave absorption transient technique. These experiments also reveal trapping effects. Defects, which are characterized by activation energies of , and , are controlling both bulk and surface recombination. The traps , and , which are revealed by deep-level transient spectroscopy, confirm the presence of these defects.

Investigation of recombination parameters in silicon structures by infrared and microwave transient absorption techniques

Contactless techniques of infrared and microwave absorption by free carriers for the monitoring of silicon structures are described. Theoretical principles of photoconductivity decay analysis and methodology for the determination of recombination parameters are given for both homogeneous and non-homogeneous excess carrier generation. Different approximations (the methods of decay amplitude - asymptotic lifetime analysis, the simulation of the whole decay curve, the variation of effective lifetime with wafer thickness and the asymptotic lifetime measurement for stepwise varying parameters in layered structure) corresponding to real experimental conditions for various structures and treatments of materials, which are important for microelectronics, are discussed. The determined recombination parameters in the range of bulk lifetime , velocity of surface recombination and diffusion coefficient are illustrated for Si wafers obtained by various doping and preparation processes. The necessity to consider carrier trapping effects and nonlinear recombination processes is demonstrated by the analysis of experimental results obtained at different excitation levels for carrier concentrations in the range . The possibility of extracting the parameters of the traps (with activation energy values , and ) from the temperature-dependent asymptotic carrier lifetime measurements is illustrated for neutron transmutation doped wafers.

Applications of the age distribution in age dependent branching processes

This paper considers asymptotic properties of increasing population age dependent branching processes which have a limiting age distribution. In Section I, the Bellman-Harris model [2] is altered in accord with a suggestion by Kendall [3]. The effect of this modification on the applicable results of [3] is indicated. An extension to the case where each cell passes through a sequence of states to mitosis or proceeds from state to state in accord with a semi-Markov process to mitosis is considered. Section 1.1 considers asymptotic moments for the total number of cells. Section 1.2 treats moments in a sequence-of-states model [4]. Section 1.3 extends the results of 1.2 to a semi-Markov model. Section 1.4 treats various asymptotic lifetime distributions and fraction of cells in a given state for both the sequence-of-states and semi-Markov models.

Applications of the age distribution in age dependent branching processes

This paper considers asymptotic properties of increasing population age dependent branching processes which have a limiting age distribution. In Section I, the Bellman-Harris model [2] is altered in accord with a suggestion by Kendall [3]. The effect of this modification on the applicable results of [3] is indicated. An extension to the case where each cell passes through a sequence of states to mitosis or proceeds from state to state in accord with a semi-Markov process to mitosis is considered. Section 1.1 considers asymptotic moments for the total number of cells. Section 1.2 treats moments in a sequence-of-states model [4]. Section 1.3 extends the results of 1.2 to a semi-Markov model. Section 1.4 treats various asymptotic lifetime distributions and fraction of cells in a given state for both the sequence-of-states and semi-Markov models.