An Efficient Resilient MPC Scheme via Constraint Tightening against Cyberattacks: Application to Vehicle Cruise Control

We propose a novel framework for designing a resilient Model Predictive Control (MPC) targeting uncertain linear systems under cyber attack. Assuming a periodic attack scenario, we model the system under Denial of Service (DoS) attack, also with measurement noise, as an uncertain linear system with parametric and additive uncertainty. To detect anomalies, we employ a Kalman filter-based approach. Then, through our observations of the intensity of the launched attack, we determine a range of possible values for the system matrices, as well as establish bounds of the additive uncertainty for the equivalent uncertain system. Leveraging a recent constraint tightening robust MPC method, we present an optimization-based resilient algorithm. Accordingly, we compute the uncertainty bounds and corresponding constraints offline for various attack magnitudes. Then, this data can be used efficiently in the MPC computations online. We demonstrate the effectiveness of the developed framework on the Adaptive Cruise Control (ACC) problem.Comment: To Appear in ICINCO 202

A new post-frac evaluation method for shale gas wells based on fracturing curves

AbstractPost-fracturing evaluation by using limited data is of great significance to continuous improvement of the fracturing programs. In this paper, a fracturing curve was divided into two stages (i.e., prepad fluid injection and main fracturing) so as to further understand the parameters of reservoirs and artificial fractures. The brittleness and plasticity of formations were qualitatively identified by use of the statistics of formation fracture frequency, and average pressure dropping range and rate during the prepad fluid injection. The composite brittleness index was quantitatively calculated by using the energy zones in the process of fracturing. It is shown from the large-scale true triaxial physical simulation results that the complexity of fractures is reflected by the pressure fluctuation frequency and amplitude in the main fracturing curve, and combined with the brittleness and plasticity of formations, the fracture morphology far away from the well can be diagnosed. Well P, a shale gas well in SE Chongqing, was taken as an example for post-fracturing evaluation. It is shown that the shale beds are of stronger heterogeneity along the extension directions of horizontal wells, and with GR 260 API as the dividing line between brittleness and plasticity in this area, complex fracture systems tend to form in brittleness-prone formations. In Well P, half of the fractures are single fractures, so it is necessary to carry out fine subsection and turnaround fracturing so as to improve development effects. This paper provides a theoretical basis for improving the fracturing well design and increasing the effective stimulated volume in this area

Assessing cognitive impairment in home-dwelling Chinese elders aged 80+: a detailed survey of 13,000 participants focusing on demographic factors, social engagement, and disease prevalence

IntroductionCognitive Impairment (CI) in the elderly, encompassing conditions ranging from Mild Cognitive Impairment (MCI) to dementia, represents a growing public health concern globally. This study aims to investigate the prevalence and correlates of CI among individuals aged 80 and above.MethodsThe study conducts 13,027 elderly individual’s door-to-door surveys, followed by the cross-tabulation of analysis data, logistic regression analysis, and health condition assessments to examine various determinants of CI.ResultsThe current study’s key findings demonstrate sub-statical correlations between CI and various factors, including educational attainment, marital status, and gender. Pronounced differences are evident between urban and rural demographics. Furthermore, aspects of social engagement, notably communication proficiency and sensory capabilities, exhibit a strong association with CI. Logistic regression analysis highlights that residing in rural areas (Odds Ratio [OR] = 0.637) and being female (OR = 0.71) are linked to a decreased risk of CI. In contrast, behavioral and health-related variables present a complex picture. Specifically, aggressive behavior (Adjusted OR = 1.881) and symptoms of depression (Adjusted OR = 0.549) contrast with conditions such as asthma (OR= 2.857) and cerebral infarction (OR=1.348), which elevate the risk of CI. Intriguingly, hyperlipidemia (OR= 0.671) appears to confer a protective effect against CI.ConclusionThe study highlights the complexity of factors affecting CI in the elderly, advocating for a comprehensive approach to understanding and managing cognitive health

Evaluating essential features of proppant transport at engineering scales combining field measurements with machine learning algorithms

The behaviours of the particle settlement, stratified flow and inception of settled particles are essential features that determine the proppant transport in low-viscosity fracturing fluids. Although great efforts have been made to characterize these features, limited research work is performed at field scales. To test the laboratory outcomes, we propose a machine-learning-based workflow to evaluate the essential features using the measurements obtained from shale gas fracturing wells. Over 430,000 groups of fracturing data (1 s time interval) are collected and pre-processed to extract the particle settlement, stratified flow and inception features during fracturing operations. The GRU and SVM algorithms, trained by these features, are applied to predict fracturing pressure. Error analysis (the root mean squared error, RMSE) is carried out to compare the contributions of different features to the pressure prediction, based on which the features and the corresponding calculations are evaluated. Our result shows that the stratified-flow feature (fracture-level) possesses better interpretations for the proppant transport, in which the Bi-power model helps to produce the best predictions. The settlement and inception features (particle-level) perform better in cases where the pressure fluctuates significantly. The features characterize the state of proppant transport, based on which the development of subsurface fracture is also analyzed. Moreover, our analyses of the remaining errors in the pressure-ascending cases suggest that (1) an introduction of the alternate-injection process, and (2) the improved calculation of proppant transport in highly-filled fractures will be beneficial to both experimental observations and field applications

Characterization of Neuraminidases from the Highly Pathogenic Avian H5N1 and 2009 Pandemic H1N1 Influenza A Viruses

To study the precise role of the neuraminidase (NA), and its stalk region in particular, in the assembly, release, and entry of influenza virus, we deleted the 20-aa stalk segment from 2009 pandemic H1N1 NA (09N1) and inserted this segment, now designated 09s60, into the stalk region of a highly pathogenic avian influenza (HPAI) virus H5N1 NA (AH N1). The biological characterization of these wild-type and mutant NAs was analyzed by pseudotyped particles (pseudoparticles) system. Compared with the wild-type AH N1, the wild-type 09N1 exhibited higher NA activity and released more pseudoparticles. Deletion/insertion of the 09s60 segment did not alter this relationship. The infectivity of pseudoparticles harboring NA in combination with the hemagglutinin from HPAI H5N1 (AH H5) was decreased by insertion of 09s60 into AH N1 and was increased by deletion of 09s60 from 09N1. When isolated from the wild-type 2009H1N1 virus, 09N1 existed in the forms (in order of abundance) dimer>>tetramer>monomer, but when isolated from pseudoparticles, 09N1 existed in the forms dimer>monomer>>>tetramer. After deletion of 09s60, 09N1 existed in the forms monomer>>>dimer. AH N1 from pseudoparticles existed in the forms monomer>>dimer, but after insertion of 09s60, it existed in the forms dimer>>monomer. Deletion/insertion of 09s60 did not alter the NA glycosylation pattern of 09N1 or AH N1. The 09N1 was more sensitive than the AH N1 to the NA inhibitor oseltamivir, suggesting that the infectivity-enhancing effect of oseltamivir correlates with robust NA activity

Breakthrough in staged fracturing technology for deep shale gas reservoirs in SE Sichuan Basin and its implications

In the Southeastern Sichuan Basin, the deep shale reservoirs (with vertical depth over 2800 m) are complicated and diverse in reservoir mineral compositions and pore structural characteristics, with the obvious rock plasticity and nonlinear fracturing features and the high absolute difference between maximum and minimum principal stresses, due to the effect of geological setting and diagenesis. Consequently, staged fracturing operations often suffer from high fracturing pressure and propagating pressure, small fracture width, low sand–fluid ratio and fracture conductivity and difficult formation of volume fractures, which seriously influence the post-fracturing shale gas productivity. In this paper, a new combined fracturing mode (pretreatment acid + gelled fluid + slickwater + gelled fluid) and its supporting technologies were developed after a series of analysis and studies on deep rocks in terms of mechanical property, earth stress characteristics, fracturing characteristics and fracture morphology characteristics. Field application shows that geologic breakthrough was realized in Longmaxi Fm of Lower Silurian in Well Dingye 2HF, with absolute open flow (AOF) of 10.5 × 104 m3/d after fracturing. And it was expected to reach commercial breakthrough in Qiongzhusi Fm of Lower Cambrian in Well Jinye 1HF, with AOF of 10.5 × 104 m3/d after fracturing. Finally, the following conclusions are reached. First, it is hard to form complex fractures in deep shale and the fracturing technologies applicable for it should be different from those used in mid–deep zones. Second, the established fracturing pressure model can provide an effective way for deep-zone fracturing pressure prediction. Third, reducing operation pressure is one of the key measures to ensure successful deep-zone fracturing. Fourth, besides good material basis, it is crucial to increase the complexity of induced fractures and generate high-conductivity fractures in order to guarantee successful fracturing in deep shale

Incipient motion behavior of the settled particles in supercritical CO2

The incipient motion process of settled particles in supercritical CO2 was studied through experimental measurements and force analyses. By referring to the theories of sand-wind and sediment restarting, the incipient motion state description and mechanism were optimized to fill the theoretical gaps in particle restarting research in the petroleum industry. Visualization experiments were carried out under various temperature, pressure, and particle conditions. The critical pump rates for the onset of grain motion in supercritical CO2 were measured. A critical pump rate empirical formula was obtained based on the experimental results and a derived Shields number expression. The average critical Shields number in supercritical CO2 was 0.0028. The cohesive force on particles is zero in supercritical CO2 based on its non-interfacial-tension characteristic. The measured spinning rate of the restarting particles in supercritical CO2 was 121 r/s on average. Therefore, the calculated value of the Magnus force was approximately 30% of the force of gravity on particle. Particle incipient motion in supercritical CO2 has a varying driving force (Magnus force) and simple resistant force (lack of cohesive force), which enhances the incipient motion of particles in supercritical CO2