Triggering Mechanism Research Articles

Distributed l2−l∞ filtering over wireless sensors based on adaptive event triggering

This paper investigates the design problem of a set of distributed filters. These adaptive event-triggered (AET) filters have the [Formula: see text] property and are suitable for sensor networks characterized by random measurement data loss and dynamic topology switching. In a distributed filtering network, each local filter estimates the system’s state not only relying on the node’s individual information but also using information from neighboring nodes in the network topology. The adaptive event triggering condition is determined by the combination of the latest release data of the filter itself, the estimated value of the current moment, and the latest release data of the neighboring nodes. The event triggering mechanism adopts a threshold adaptive adjustment scheme, which dynamically changes the threshold parameter according to the filtering error under the premise of guaranteeing the filter performance, thus maximally saving the network communication resources. Initially, we used a binary sequence to describe the random loss of sensor measurements, and a Markov chain is used to describe the switching of the filtering network topology. Secondly, a Lyapunov function is created to examine the [Formula: see text] performance index of the filtering error system and investigate its mean square exponential stability. Subsequently, the distributed filter is formulated, and its parameters are determined using the linear matrix inequality approach. Ultimately, the validity of the proposed method is substantiated through numerical illustrations.

Core needle biopsy for thyroid nodules assessment-a new horizon?

Ultrasound-guided fine-needle aspiration is the standard for evaluating thyroid nodules with a high safety profile and a relatively low number of non-diagnostic cytological findings. Nevertheless, this diagnostic method traditionally has its weak points. Several diagnostic categories such as Bethesda I, III and IV are not reliable for thyroid carcinoma risk assessment. Recent advancements in a core needle biopsy made it possible to use this tool as a new method for thyroid nodules evaluation. The main feature of this method is the use of thin needles (18-21G) and guns with an automatic trigger mechanism. The histological material collected with the use of a core needle biopsy is usually superior to cytological. Therefore, the core needle biopsy can be used as a complementary technique to a standard fine needle aspiration in difficult and dubious cases of thyroid neoplasia with uncertain malignant potential.

Precise dating of large flank collapses by single-grain 40Ar/39Ar on pyroclastic deposits from the example of Flores Island (Azores)

Large-scale flank collapses are one of the main hazards associated with the evolution of volcanic islands. Precisely dating such events is critical to evaluate the frequency of destabilization episodes and further assess the triggering mechanism(s) associated with internal and/or external factors, such as volcano dynamics, regional tectonics, and global paleoclimatic changes. Here, we constrain the age of a pumice-rich pyroclastic deposit exposed on the eastern flank of Flores Island (Azores), which we interpret as a co-blast deposit generated by a major flank collapse that destroyed the whole western flank of the former volcanic edifice. Twelve single-grain 40Ar/39Ar analyses, performed on 250–500 µm anorthoclase feldspars (mean K/Ca close to 5) with our high-sensitivity multi-collector NGX mass spectrometer, provide a robust weighted mean age of 1.32 ± 0.01 Ma for this eruption. This new age is consistent with previous K/Ar data bracketing the flank collapse between 1.30 ± 0.04 and 1.18 ± 0.09 Ma, and indicates that this event occurred at the end of the main construction phase of the volcano. The explosion produced pumice-rich layers preceded by a lahar as attested by a polygenetic mudflow deposit underlying the dated deposit. From the geochemistry of lavas erupted just before and after the collapse, we speculate upon the possible role of magmatic processes on flank destabilization. We propose a first hypothesis where differentiation in a shallow magma reservoir could have favored edifice inflation, ground shaking, and flank failure, triggering a decompression-induced violent eruption. Overall, our study shows that high-sensitivity mass spectrometers have now reached analytical performances allowing to measure precisely and accurately ages on relatively small and moderately K-rich single feldspars, which is of the utmost importance for dating heterogeneous blasts and tephra deposits that may have been induced by large-scale flank collapses during the late Quaternary.

Ultrafast energy quenching mechanism of LHCSR3-dependent photoprotection in Chlamydomonas

Photosynthetic organisms have evolved an essential energy-dependent quenching (qE) mechanism to avoid any lethal damages caused by high light. While the triggering mechanism of qE has been well addressed, candidates for quenchers are often debated. This lack of understanding is because of the tremendous difficulty in measuring intact cells using transient absorption techniques. Here, we have conducted femtosecond pump-probe measurements to characterize this photophysical reaction using micro-sized cell fractions of the green alga Chlamydomonas reinhardtii that retain physiological qE function. Combined with kinetic modeling, we have demonstrated the presence of an ultrafast excitation energy transfer (EET) pathway from Chlorophyll a (Chl a) Qy to a carotenoid (car) S1 state, therefore proposing that this carotenoid, likely lutein1, is the quencher. This work has provided an easy-to-prepare qE active thylakoid membrane system for advanced spectroscopic studies and demonstrated that the energy dissipation pathway of qE is evolutionarily conserved from green algae to land plants.

Adaptive event‐triggered control and observer design for discrete‐time nonlinear Markov jump systems with DoS attacks using policy iteration‐based adaptive dynamic programming

AbstractThis article addresses adaptive event‐triggered discrete‐time nonlinear Markov jump systems (MJs) with DoS attacks, where the introduced DoS attacks are considered as more general stochastic models with fixed trigger frequency and duration. To solve the optimal control problem, we use an adaptive dynamic programming (ADP) algorithm based on policy iteration (PI). The approximate process is as follows: the performance index function (PIF) is first updated by the iteration policy in advance, and the control policy is obtained from the PIF. Subsequently, an approximate estimation of the optimal PIF and the optimal control policy is made using the actor‐critic structure obtained through neural network techniques. In order to reduce the occupied communication resources required for control policy iteration, we introduce an adaptive event triggering mechanism with an adaptive triggering threshold, which reduces the conservatism of resource occupation by the PIF compared to the fixed‐threshold ETM. In addition, an observer identifying the unknown dynamics part of the system is designed. Finally, using the Lyapunov function, it is shown that the designed control policy ensures the stability and convergence of the MJS, and the designed observer is effective. Simulation examples are given to verify the feasibility of the controller and the observer.

Differences in the characteristics and triggering mechanisms of two successive AL index onsets on 21st January 2005

Differences in the characteristics and triggering mechanisms of two successive AL index onsets on 21st January 2005

Investigating the role of geochemistry and geotechnical properties in landslide characterization and triggering mechanisms: A case study from Dir Upper, Khyber Pakhtunkhwa Pakistan

The 83.5 km Chukyatan-Kumrat Upper Dir road plays a crucial role in transportation and tourism in North Pakistan. Despite its significance, the area faces frequent landslides due to hydrometeorological hazards, posing a threat to its stability. This study conducts the first extensive investigation of landslide susceptibility in the region, considering geological features, geotechnical properties, and rock weathering. The road traverses diverse rock formations, including meta-volcanics, andesites, meta-rhyolites, ignimbrites, volcanic ash, granodiorites, and spotted slates, overlain by residual soils. The presence of the Dir fault has led to significant accumulations of loose, weathered rock debris (>100 m deep). Exposed slopes exhibit polygonal stress fractures, joints, and fissures with steep inclinations (>40°), further enhancing instability. Geotechnical analysis reveals a low internal friction angle (28.5°–31.9°) and cohesion (4.1–5.9 kPa) of slope materials, indicating poor shear resistance compared to stable slopes. The unconfined compressive strength of bedrock (10.7–41.5 MPa) ranges from weak to moderate-strong, emphasizing the contribution of weaker rock formations to instability. Acidic soil pH (3.1–4.2) and clay minerals support the prevalence of weathering conditions promoting landslides. Thin section analysis and X-ray diffraction reveal hydrothermal alteration during low-grade metamorphism, leading to the formation of chlorite, smectite, montmorillonite, and zeolites. Additionally, physical weathering has increased quartz content, potentially impacting slope stability. The combined effect of factors such as steep slope geometry, low shear strength with strain-softening properties, rainfall, snowmelt, freeze-thaw activity, slope base cutting for road development, and massive loading from houses contributes to numerous landslides in the region. The study aids effective mitigation and preparedness in the Chukyatan-Kumrat area and offers insights for landslide susceptibility mapping in similar geological settings.

Fluorescent small molecule donors.

Small molecule donors (SMDs) play subtle roles in the signaling mechanism and disease treatments. While many excellent SMDs have been developed, dosage control, targeted delivery, spatiotemporal feedback, as well as the efficiency evaluation of small molecules are still key challenges. Accordingly, fluorescent small molecule donors (FSMDs) have emerged to meet these challenges. FSMDs enable controllable release and non-invasive real-time monitoring, providing significant advantages for drug development and clinical diagnosis. Integration of FSMDs with chemotherapeutic, photodynamic or photothermal properties can take full advantage of each mode to enhance therapeutic efficacy. Given the remarkable properties and the thriving development of FSMDs, we believe a review is needed to summarize the design, triggering strategies and tracking mechanisms of FSMDs. With this review, we compiled FSMDs for most small molecules (nitric oxide, carbon monoxide, hydrogen sulfide, sulfur dioxide, reactive oxygen species and formaldehyde), and discuss recent progress concerning their molecular design, structural classification, mechanisms of generation, triggered release, structure-activity relationships, and the fluorescence response mechanism. Firstly, from the large number of fluorescent small molecular donors available, we have organized the common structures for producing different types of small molecules, providing a general strategy for the development of FSMDs. Secondly, we have classified FSMDs in terms of the respective donor types and fluorophore structures. Thirdly, we discuss the mechanisms and factors associated with the controlled release of small molecules and the regulation of the fluorescence responses, from which universal guidelines for optical properties and structure rearrangement were established, mainly involving light-controlled, enzyme-activated, reactive oxygen species-triggered, biothiol-triggered, single-electron reduction, click chemistry, and other triggering mechanisms. Fourthly, representative applications of FSMDs for trackable release, and evaluation monitoring, as well as for visible in vivo treatment are outlined, to illustrate the potential of FSMDs in drug screening and precision medicine. Finally, we discuss the opportunities and remaining challenges for the development of FSMDs for practical and clinical applications, which we anticipate will stimulate the attention of researchers in the diverse fields of chemistry, pharmacology, chemical biology and clinical chemistry. With this review, we hope to impart new understanding thereby enabling the rapid development of the next generation of FSMDs.

Oxidative Stress in Breast Cancer: A Biochemical Map of Reactive Oxygen Species Production.

This review systematizes information about the metabolic features of breast cancer directly related to oxidative stress. It has been shown those redox changes occur at all levels and affect many regulatory systems in the human body. The features of the biochemical processes occurring in breast cancer are described, ranging from nonspecific, at first glance, and strictly biochemical to hormone-induced reactions, genetic and epigenetic regulation, which allows for a broader and deeper understanding of the principles of oncogenesis, as well as maintaining the viability of cancer cells in the mammary gland. Specific pathways of the activation of oxidative stress have been studied as a response to the overproduction of stress hormones and estrogens, and specific ways to reduce its negative impact have been described. The diversity of participants that trigger redox reactions from different sides is considered more fully: glycolytic activity in breast cancer, and the nature of consumption of amino acids and metals. The role of metals in oxidative stress is discussed in detail. They can act as both co-factors and direct participants in oxidative stress, since they are either a trigger mechanism for lipid peroxidation or capable of activating signaling pathways that affect tumorigenesis. Special attention has been paid to the genetic and epigenetic regulation of breast tumors. A complex cascade of mechanisms of epigenetic regulation is explained, which made it possible to reconsider the existing opinion about the triggers and pathways for launching the oncological process, the survival of cancer cells and their ability to localize.

Trigger mechanism centralized but discursive frame fragmented: China as a case for studying populism at the grassroots level in the social media age

ABSTRACT While most research focuses on top-down populism practiced by political actors in democratic countries, we paid attention to populist phenomena at the grassroots level in an authoritarian context. Specifically, we proposed a perspective of investigating populist discourse embedded in public opinion and adopted a fine-grained discursive frame approach to study Chinese online populism. Using large-scale social media data around trending events and employing cutting-edge computational semantic analysis methods, we discovered that economic anxiety is central to the trigger mechanism of Chinese online populism, and the specific populist discourse is fragmented in terms of ideological resources, cultural toolboxes, and semantic structure. This study not only provides a more comprehensive understanding of contemporary Chinese populism phenomena, but it also contributes to global populism research by providing valuable empirical evidence in authoritarian contexts and broadening the theoretical perspective of studying populism at the grassroots level.

Association of Uterine Tissue Innervation and Peripheral Nerve Density with Adenomyosis Related Pain. A Systematic Review.

Adenomyosis is associated with dysmenorrhea and chronic pelvic pain; however, the triggering mechanisms of painful stimuli and the role of uterine nerve fibers in the manifestation of pain remain poorly understood. The objective of this study was to systematically review the role of uterine nerve fibers' presence and density in the occurrence of pain in patients with adenomyosis. An electronic search was performed using the Embase, PubMed/Medline, and Cochrane databases. We included all studies from inception to November 2023. A total of ten studies that compared uterine biopsies samples of women with and without adenomyosis were included. The biomarker antiprotein gene product 9.5 was decreased or absent in the endometrium of most included women with adenomyosis. None of the included studies observed a difference in neurofilament (NF) staining between the adenomyosis and non-adenomyosis groups. Studies that assessed nerve growth factor (NGF) staining were heterogeneous in design. One study reported no difference in immunohistochemistry staining in any endometrial layer between the adenomyosis and non-adenomyosis groups, while another reported increased staining in the adenomyosis functional endometrial layer, and a third study reported overexpression of NGF, synaptophysin (SYN), and microtubule-associated protein 2 mRNA in focal adenomyosis alone. Preliminary data from poor-quality studies suggest an increase in the uterine density of nerve fibers in patients with adenomyosis. Well-designed studies are essential to assess the cause-and-effect relationship between uterine nerve fibers and pain in patients with adenomyosis.

BCM-7: Opioid-like Peptide with Potential Role in Disease Mechanisms.

Bovine milk is an essential supplement due to its rich energy- and nutrient-rich qualities. Caseins constitute the vast majority of the proteins in milk. Among these, β-casein comprises around 37% of all caseins, and it is an important type of casein with several different variants. The A1 and A2 variants of β-casein are the most researched genotypes due to the changes in their composition. It is accepted that the A2 variant is ancestral, while a point mutation in the 67th amino acid created the A1 variant. The digestion derived of both A1 and A2 milk is BCM-7. Digestion of A2 milk in the human intestine also forms BCM-9 peptide molecule. The opioid-like characteristics of BCM-7 are highlighted for their potential triggering effect on several diseases. Most research has been focused on gastrointestinal-related diseases; however other metabolic and nervous system-based diseases are also potentially triggered. By manipulating the mechanisms of these diseases, BCM-7 can induce certain situations, such as conformational changes, reduction in protein activity, and the creation of undesired activity in the biological system. Furthermore, the genotype of casein can also play a role in bone health, such as altering fracture rates, and calcium contents can change the characteristics of dietary products. The context between opioid molecules and BCM-7 points to a potential triggering mechanism for the central nervous system and other metabolic diseases discussed.

Abstract PO4-10-08: Building a standard methodology: Early Gynecologic Consultation and Bone Mass Density Examination in Breast Cancer Patients Receiving Endocrine Therapy

Abstract Purpose Hormone receptor-positive type of breast cancer is typically treated with hormone therapy (HT), including tamoxifen and aromatase inhibitors (AI). However, long-term use of HT may increase the risks of endometrial cancer, vaginal dryness, and osteoporosis. To minimize the risks, breast surgeons should schedule regular follow-up with gynecologists and arrange bone mass density (BMD) examination. Using the Plan-Do-Study-Act (PDSA) methodology, we aimed to increase cross-team care with gynecology department and to promote BMD examination for breast cancer patients receiving HT. Methods We formed a multidisciplinary team including breast surgery department and gynecologic department in our hospital that care for female patients with breast cancer and related side effects. We arranged a lecture for all collaborative doctors, introducing our aims, interventions, and measurement strategies to test in multiple PDSA cycles. The interventions with standardized criteria include: (1) a gynecologic consultation, triggered if a patient initially receive tamoxifen and (2) a BMD examination, triggered if a patient initially receive AI. The triggering mechanism is embedded in the ambulatory alarming system. Both the intervention rates were tracked during PDSA cycle 1 in 2023 and compared with baseline rates in 2020-2022. Adherence to the plan was maintained and measured using data analytic reports and chart audits. Results The gynecologic consultation rate during PDSA cycle 1 is significantly higher than the baseline, which is 40.4% and 22.4% (p = 0.006), respectively. In patients who received tamoxifen, 6-month-consultation rate during PDSA cycle 1 is also significantly higher than the baseline group, which is 77.77% and 42.9% (p = 0.005), respectively. The median time from HT therapy to first gynecologic consultation decreased from 51 days to 28 days. Furthermore, the baseline BMD testing rate before our intervention was 30.6%. This increased to 48.3% during PDSA cycle 1. Conclusion Standardized gynecologic consultation criteria led to earlier gynecologic consultation in breast cancer patients receiving tamoxifen and higher BMD test rates in patients receiving AI. Future PDSA cycles will focus on assessing the frequency of subsequent gynecologic encounters in patients who received a triggered gynecologic consult. Citation Format: Chiu Ching-Wen, Tam Ka-Wai, Su Chih-Ming, Wu Hsueh-Chi. Building a standard methodology: Early Gynecologic Consultation and Bone Mass Density Examination in Breast Cancer Patients Receiving Endocrine Therapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-10-08.

Experimental Study on the Self-Initiated Static-Dynamic State Transition Mechanism of Strain Rockburst

During the entire processes of rockburst catastrophe, the self-initiated static-dynamic state transition behaviour is a turning point in the development of strain rockburst from static deformation to dynamic failure. However, its dynamic process and triggering mechanism have not yet received sufficient attention and accurate revelation. This study focuses on the scientific issue, by designing experiment we have successfully achieved the physical simulation of rockburst under quasi-static displacement loading conditions. Then, the static-dynamic state transition process was studied on a millisecond time scale, and rockburst triggering mechanism was investigated from mechanical perspectives. Through experiment, the self-initiated elastic rebound dynamic behaviour of the surrounding rock is discovered and identified as the key to triggering rockburst. Mechanically, this behaviour directly causes an impact load on the burst rock, which can be considered the direct cause of rockburst.

The Fermi-LAT view of the changing-look blazar OQ 334

Context. Unusually, there are still certain characteristics of the changing-look (CL) active galactic nuclei (AGNs) that remain undetected. Consequently, the trigger mechanism behind the CL phenomenon observed in partial AGNs remains unknown. Aims. We explore the light curve and spectral energy distribution (SED) of the CL blazar OQ 334 as obtained by Fermi-LAT. Methods. By examining the variability of the equivalent width (EW), we categorise the Fermi-LAT light curves of OQ 334 during the epoch of MJD 54628−58677 into seven distinct epochs, including the flat spectrum radio quasar (FSRQ) state, the transition state, and the BL Lac state. We obtained both a Fermi-LAT SED and a multi-wavelength SED for each of these distinct epochs. Results. The source exhibits a transformation from a quiescent state to a highly active state, as evidenced by the variability of the EW. The multi-wavelength SEDs display a prominent external Compton characteristic, even though the Fermi-LAT SED reveals both a FSRQ and a BL Lac state across the seven different epochs. To gain further insights, we employed a leptonic model that takes into account the soft photon fields originating from both synchrotron radiation and the external environment. By simulating the multi-wavelength SEDs for each epoch, we uncover the following results. Firstly, the energy density of the external photon fields evolves in an oscillatory manner over the seven different epochs. Also, the energy density of the external photon fields in the BL Lac state is lower than that in the FSRQ state. Conclusions. These findings suggest that the CL blazar represents a unique phase in the blazar sequence. Considering that the energy density of the external photon fields is proportional to the accretion rate, we propose that evidence for the interconversion of advection-dominated accretion flow (ADAF) discs and standard Shakura–Sunyaev discs (SSDs), – as variations in accretion modes in the CL blazar – can be obtained through observations by Fermi-LAT.

Self-triggered formation attitude control for multiple spacecraft with disturbances

This paper studies the attitude consensus for nonlinear multi-spacecraft systems with disturbances and limited communication bandwidth and computing resources. A dynamic event-based attitude controller is developed to conserve communication resources, where a positive constant term is introduced to improve resource conservation efficiency. The developed event-driven controller is updated according to the constructed triggering mechanism, which greatly reduces the number of computations for the control algorithm. The triggering mechanism does not require continuous state information of neighboring spacecraft, which indicates that continuous communication is not needed for the operation of the formation system. Then, a self-triggered mechanism using the current triggering information is designed to further avoid continuous computation, and the avoidance of logarithmic functions enables the trigger interval to be close to that of the dynamic event-driven algorithm. The formation system is Zeno-free and uniformly ultimately bounded stable under the proposed event-based consensus control framework with the triggering strategies. Finally, simulations exhibit that the dynamic event-triggered protocol can reduce the communication frequency by 88%, and the self-triggered protocol can reduce the communication and computation frequency by 83% and have higher control accuracy than the dynamic event-triggered protocol.

BFTDiagnosis: An automated security testing framework with malicious behavior injection for BFT protocols

In peer-to-peer computing networks, Byzantine Fault Tolerance (BFT) protocols are a popular solution to ensure the consistency security in the presence of some malicious nodes, thus are widely employed in blockchain systems. However, BFT protocols still face various security threats in practice. Currently, testing the security of BFT protocols often requires manual operations. I.e., it lacks comprehensive automation testing techniques. This makes it difficult to cover various scenarios of malicious node behaviors. Therefore, it is an urgent requirement to design an automated testing framework that can comprehensively and efficiently evaluate the security of BFT protocols.This paper proposes BFTDiagnosis, an automated security testing framework with malicious behavior injection for BFT protocols. The framework can automatically configure and initiate protocol testing tasks, and construct consensus nodes to execute different BFT protocols. During testing, consensus nodes can inject malicious behaviors based on pattern matching strategies and malicious behavior triggering mechanisms to simulate various malicious scenarios. Through an Analyzer, BFTDiagnosis can collect protocol runtime data from consensus nodes and calculate four security quantification indicators to evaluate protocol performance.We conducted a load consumption evaluation of BFTDiagnosis. The results indicate its acceptable performance. Additionally, we tested PBFT, Basic-HotStuff, and Chained-HotStuff protocols using the BFTDiagnosis framework, validating the effectiveness of the framework and the rationality of security quantification indicators. Finally, we compared it with nine related technologies and found that BFTDiagnosis is good at testing scenario comprehensiveness and fault localization capability, and can intuitively evaluate the security of BFT protocols through four quantification indicators. The above results show that BFTDiagnosis is an effective and comprehensive security testing framework for BFT protocols.

The Great Dimming of Betelgeuse: The photosphere as revealed by tomography over the past 15 yr

Context. Betelgeuse, a red supergiant star of semi-regular variability, reached a historical minimum brightness in February 2020, known as the Great Dimming. Even though the brightness has returned to the values prior to the Great Dimming now, it continues to exhibit highly unusual behavior. Aims. Understanding the long-term atmospheric motions of Betelgeuse and its variability could be a clue to the nature of the Great Dimming and the mass-loss process in red supergiants. Our goal is to study long-term dynamics of the photosphere, including during the Great Dimming. Methods. We applied the tomographic method, which allows different layers in the stellar atmosphere to be probed in order to reconstruct depth-dependent velocity fields. The method is based on the construction of spectral masks by grouping spectral lines from specific optical depths. These masks are cross-correlated with the observed spectra to recover the velocity field inside each atmospheric layer. Results. We obtained about 2800 spectra over the past 15 yr that were observed with the STELLA robotic telescope in Tenerife. We analyzed the variability of five different layers of Betelgeuse’s photosphere. We found phase shift between the layers, as well as between the variability of velocity and photometry. The time variations of the widths of the cross-correlation function reveal propagation of two shockwaves during the Great Dimming. For about 2 yr after the dimming, the timescale of variability was different between the inner and outer photospheric layers. By 2022, all the layers seemingly started to follow a similar behavior as before the dimming, but pulsating with higher frequency corresponding with the first overtone. Conclusions. The combination of the extensive high-resolution spectroscopic data set with the tomographic method revealed the variable velocity fields in the photosphere of Betelgeuse, for the first time in such detail. We were also able to find new insights related to the Great Dimming event and its aftermath, namely the discovery of another shockwave and the subsequent rearrangement of the photosphere. Our results demonstrate that powerful shocks are the triggering mechanism for episodic mass-loss events, which may be the missing component to explain the mass-loss process in red supergiants.

Triggering and evolution of static liquefaction in submarine slopes with quasi-saturated sand

Liquefaction flow slides of submarine slopes with quasi-saturated sand have been frequently observed in engineering practice. That instability can be attributed to a decrease in resistant shear strength caused by static liquefaction. However, the triggering of static liquefaction in submarine slopes has received limited attention. To address this gap, a state-dependent constitutive model for quasi-saturated sand with entrapped air is employed that can represent the effects of compression and dissolution of gas accurately. Moreover, the soil model enables the evaluation of the triggering of static liquefaction based on second-order work. To study the triggering mechanism of static liquefaction, a submarine slope model is established using the material point method. The static liquefaction area is detected by the vanish of second-order work. Results indicate that static liquefaction initially arises at the slope surface and gradually expands towards the interior of the slope as the rapid loading at the top of the slope increases. Furthermore, the presence of entrapped gas within the slope can effectively enhance the resistance to slope instability caused by static liquefaction. It significantly alters both the location where static liquefaction is initially triggered and the subsequent evolution pattern, in comparison with saturated submarine slopes.

Impacts of Vertical Convective Mixing Schemes and Freshwater Forcing on the 2016–2017 Maud Rise Polynya Openings in a Regional Ocean Simulation

AbstractThe correct representation of the Maud Rise open‐ocean polynya in the Weddell Sea remains a challenge for ocean models. Here we reproduce the most recent polynya openings in 2016–2017 using a regional configuration, and assess their dependencies on vertical convective mixing schemes and freshwater forcing, both separately and in combination. We test three vertical convective mixing schemes: the enhanced vertical diffusion (EVD), the Eddy‐Diffusivity Mass‐Flux (EDMF) parameterization, and a modified version of EDMF accounting for thermobaric effects. Using simulations for the period 2007–2017, we find that the modified EDMF reproduces the observed climatological evolution of the mixed layer depth better than the original EDMF and the EVD, but a polynya fails to open due to excessive freshwater forcing. We thus use the modified EDMF to perform sensitivity experiments with reduced precipitation during 2012–2017. The imposed freshwater forcing strongly affects the number of years with polynyas. The simulation with the best representation of the 2016–2017 polynyas is analyzed to evaluate the triggering mechanisms. The 2016 polynya was induced by the action of thermobaric instabilities on a weak ambient stratification. This opening preconditioned the water column for 2017, which produced a stronger polynya. By examining the impacts of the different convective mixing schemes, we show that the modified EDMF generates more realistic patterns of deep convection. Our results highlight the importance of surface freshwater forcing and thermobaricity in governing deep convection around Maud Rise, and the need to represent thermobaric instabilities to realistically model Maud Rise polynyas.