Autonomous Recovery from Spacecraft Plan Failures by Regulatory Repair While Retaining Operability

Pre-designed spacecraft plans suffer from failure due to the uncertain space environment. In this case, instead of spending a long time waiting for ground control to upload a feasible plan in order to achieve the mission goals, the spacecraft could repair the failed plan while executing another part of the plan. This paper proposes a method called Isolation and Repair Plan Failures (IRPF) for a spaceship with durable, concurrent, and resource-dependent actions. To enable the spacecraft to perform some actions when a plan fails, IRPF separates all defective actions from executable actions in the pre-designed plan according to causal analysis between the failure state and the established plan. Then, to address the competition between operation and repair during the partial execution of the plan, IRPF sets up several regulatory factors associated with the search process for a solution, and then repairs the broken plan within the limits of these factors. Experiments were carried out in simulations of a satellite and a multi-rover system. The results demonstrate that, compared with replanning and other plan-repair methods, IRPF creates an execution plan more quickly and searches for a recovery plan with fewer explored state nodes in a shorter period of time.

Benefit of Unsaturated Soil Mechanics Approach on the Modeling of Early-Age Behavior of Rammed Earth Building

Rammed earth has the potential to reduce the carbon footprint and limit the energy consumption in the building sector due to its sustainable characteristics. Still, its use is not generalized due to a lack of understanding of the material behavior, notably its sensitivity to water. The coupled hydro-mechanical behavior has been recently studied in the framework of unsaturated soil mechanics, using suction as the parameter to represent the hydric state. This dependency of the mechanical behavior on the hydric state leads to uncertainty of the drying period required to progress in the construction process. Notably, the drying period before building the next floor is unknown. To determine the drying period, thermo-hydro-mechanical coupled finite element method simulations were carried out on a single wall by using the unsaturated soil mechanics approach and safety criterion recommendations from the practical guide for rammed earth construction in France. It was determined that it takes significant time for the construction of additional floor both in ‘summer-like’ and ‘winter-like’ environmental conditions, whereas the walls were far away from the ultimate failure state. Thus the drying periods were overestimated. It was concluded that the safety criterion from the practical guide is very conservative and drying periods can be reduced without significantly compromising the safety factor.

Assessment of the asphalt mixtures properties subjected to a flexural strength

Fatigue cracking by loading is one of the main mechanisms of damage to asphalt mixtures in service. Several studies worldwide have been conducted to try to understand the response that hot-mix asphalt undergo under this mechanism of damage. Despite the above, the fatigue phenomenon in asphalt mixtures is still not fully understood. The current research hypothesizes that the response under repeated loading of asphalt mixtures in fatigue tests can be more clearly understood through the one obtained under monotonic loading. For this reason, this study presents the results of the first phase of the research in which beams of asphalt mixtures were subjected to flexion using monotonic loads. The above, to correlate the evaluated properties with those obtained in a second phase where the response of the beams under repeated load (fatigue) will be measured. Beams made of two hot-mix asphalt mixes, two asphalt contents, and two different thicknesses were subjected to flexural strength tests. From the tests, the modulus of rupture, the maximum monotonic load that supports the beams in the failure state, the displacement in the failure state, and the relation between load and displacement were obtained. As a general conclusion of the study, it was obtained that the response experienced by the beams subjected to monotonic load has a broad correlation with the reported in the reference literature.

Ultimate state criteria and strength characteristics of the rock massifs being undermined repeatedly

Methodological approaches to the selection of ultimate state criteria and strength characteristics of the repeatedly undermined rock massifs were developed. These approaches were designed to provide parametric support to the geomechanical modelling of the massif stress-strain state and the mining systems of the Starobin potash deposit mine fields planned for the additional mining of the mineral reserves left. It was established that a complex criterion must be used to study the massif ultimate state. Determination of such criterion can be carried out using the developed approaches. The first approach is to select several criteria that evaluate the massif ultimate state by certain types of the massif stress-strain state. These criteria are the following: the criterion of the maximum normal stresses, criterion of the maximum linear strains, the criterion of the maximum shear stresses and the Coulomb–Mohr failure criterion. The second approach is to construct an integrated failure state criterion for materials whose ultimate tensile and compressive stresses differ significantly. In this case, parameters characterizing the type of stress state and properties of the material are introduced. These parameters together determine the destruction character – tear or shear. To describe the rocks behavior in the extreme strength stage of deformation, it is proposed to apply deformation theory of strength using the developed strain failure criterion. When calculating the strength characteristics of the repeatedly undermined rock massif, it is recommended to use a structural attenuation coefficient as the product of several factors, taking into account various types of disturbances in the primary undermined massif and the time factor. The Coulomb–Mohr strength condition is recommended to be used taking into account the composite structural attenuation coefficient. Dependencies have been developed to describe the change in the strength characteristics of rocks in the undermined massif, considering the attenuation coefficient.

Hybrid method of intellectual diagnosis and forecasting of complex technical systems

Modern control and diagnostic systems (CDS) usually determine only the technical condition (TC) at the current time, ie the CDS answers the question: a complex technical system (CTS) should be considered operational or not, and may provide little information on performance CTS even in the near future. Therefore, the existing scenarios of CDS operation do not provide for the assessment of the possibility of gradual failures, ie there is no forecasting of the technical condition. The processes of parameter degradation and degradation prediction are stochastic processes, the “behavior” of which is influenced by a combination of external and internal factors, so the deg-radation process can be described as a function that depends on changes in the internal parameters of CTS. The hybrid method involves the following steps. The first is to determine the set of initial characteristics that characterize the CTS vehicle. The second is the establishment of precautionary tolerances of degradation values of the characteristics that characterize the pre-failure technical con-dition of the CTS. The third is to determine the rational composition of informative indicators, which maximally determine the "behavior" of the initial characteristics. The fourth — implementa-tion of multiparameter monitoring, fixation of values of the controlled characteristics, formation of an information array of values of characteristics. Fifth — the adoption of a general model of the process of changing the characteristics of the CTS. Sixth — the formation of a real model of the process of changing the characteristics of Y(t) on the basis of an information array of values of char-acteristics obtained by multi-parameter monitoring. Seventh — forecasting the time of possible oc-currence of the pre-failure state of the CTS, which is carried out by extrapolating the obtained real model of the process of changing the characteristics of Y(t). It is proposed to use two types of mod-els: for medium- and long-term forecasting - polynomial models, for short-term forecasting — a lin-ear extrapolation model. At the final stage, forecast errors are determined for all types of models of degradation of pa-rameters and characteristics. Based on the results of the forecast verification, the models are adjust-ed

Study on the Earth Pressure during Sinking Stage of Super Large Caisson Foundation

End resistance is a dominant variable in the sinking process of super-sized caisson foundation, which is of great importance to the safe sinking of the caisson foundation. Based on soil excavation process of super large caisson foundation of the main tower of Changtai Yangtze River Bridge, the distribution characteristics and variation of earth pressure under the foot blade was analyzed using 3D finite element method at the first stage of soil excavation. Furthermore, the earth pressure was monitored in real time during soil excavation in order to analyze the influence of soil excavation process on the distribution of earth pressure. The analysis results of engineering practice showed that in the process of soil excavation from inner area to outer area, the end resistance of inner bulkhead and inner partition walls decreased, while the end resistance of outer bulkhead and outer partition walls gradually increased till the soil reached the failure state in the outer bulkhead area. The distribution characteristics and variation of the earth pressure can really reflect overall stress state of caisson foundation, which helps guide the safe sinking by soil excavation.

Risk Analysis of Instability Failure of Earth–Rock Dams Based on the Fuzzy Set Theory

Determining the anti-sliding instability risk of earth–rock dams involves the analysis of complex uncertain factors, which are mostly regarded as random variables in traditional analysis methods. In fact, fuzziness and randomness are two inseparable uncertainty factors influencing the stability of earth–rock dams. Most previous research only focused on the randomness or the fuzziness of individual variables. Moreover, dam systems present a fuzzy transition from a stable state into a failure state. Therefore, both fuzziness and randomness of the influencing factors should be considered in the same framework, where the instability of an earth–rock dam is regarded as a mixed process. In this paper, a fuzzy risk model of instability of earth–rock dams is established by considering the randomness and fuzziness of parameters and the failure criteria comprehensively. We obtained the probability threshold of instability risk of earth–rock dams by Monte-Carlo simulation after the fuzzy parameters were transformed into interval numbers by cut set levels. By applying the proposed model to the instability analysis of the Longxingsi Reservoir, the calculation results showed that the lower limits of risk probability under different cut set levels exceeded the instability risk standard of grade C for earth–rock dams. Compared with the traditional risk determination value, the risk interval obtained with the proposed methods reflects different degrees of dam instability risk and can provide reference for dam structure safety assessment and management.

Lumped parameter model of the cardiovascular system with baroreflex

The patient’s activity directly affects the state of the cardiovascular system (CVS). One of the mechanisms contribute to the regulation of the arterial blood pressure is the baroreflex. It is maintains an optimal level of the arterial pressure as a response to changes in the patient’s activity. The model developed in this work simulates CVS at the different patient’s activity levels. The model of baroreflex reproduces changes that occur during an increasing level of patient’s activity. The correlation between heart rate (79 bpm –rest, 123 bpm – exercise) and cardiac output (5.1 l/min –rest, 8.2 l/min – exercise) was achieved. The developed model can be used for personal modelling of various states of the CVS. The model parameters possible to apply for individual patient characteristics. For further development, the model can be integrated with the ventricular assist device during the heart failure state in order to study interactions in the biotechnical system.

Mind–Body Interventions in Patients With Heart Failure: State of the Science

Complementary and alternative medicine are broadly considered mind–body interventions (MBIs) that support physical and mental wellness in patients with heart failure (HF). The aims of this review were to integrate and summarize current evidence from MBIs in patients with HF and to identify gaps for future research. We used PRISMA guideline and conducted a literature search through six databases. Fifteen publications met the criteria, published between 2013 and 2021. This review stipulated that MBIs included yoga, Tai Chi, meditation, reflexology, massage, relaxation, and breathing interventions. The findings emphasized that MBIs could reduce physical and psychological symptoms and improve health outcomes in patients with HF. MBIs had encouraging results for patients with HF on selected physiological and behavioral outcomes. Despite the early state of the evidence in this field, it seems that MBIs will play an essential role in the future for alleviating the symptoms of patients with HF.