Calculation of Nearly Singular Boundary Element Integrals in Thin Structures Using an Improved Exponential Transformation

In this work, an improved exponential transformation is presented for nearly singular boundary element integrals in problems of thin structures. Accurate evaluation of nearly singular integrals is an important issue in the implementation of boundary element method (BEM) for thin structures. In this paper, the exponential transformation, which was firstly developed to evaluate nearly singular integrals arising in 2D BEM, is extended into 3D BEM to deal with nearly singular integrals. Firstly, a novel (α,β) coordinate system is introduced. Then, the conventional distance function is modified into a new form in (α,β) coordinate system. Based on the refined distance function, finally, an improved exponential transformation is employed in the new coordinate system. Furthermore, to perform integrations on irregular elements, an adaptive integration scheme considering both the shape of element and the projection point associated with the improved transformation is proposed. Numerical examples are presented to verify the proposed method. Results demonstrate the accuracy and efficiency of our method. Moreover, the accuracy of our method is less sensitive to the position of the projection point than that of the traditional methods

HarmonyDream: Task Harmonization Inside World Models

Model-based reinforcement learning (MBRL) holds the promise of sample-efficient learning by utilizing a world model, which models how the environment works and typically encompasses components for two tasks: observation modeling and reward modeling. In this paper, through a dedicated empirical investigation, we gain a deeper understanding of the role each task plays in world models and uncover the overlooked potential of sample-efficient MBRL by mitigating the domination of either observation or reward modeling. Our key insight is that while prevalent approaches of explicit MBRL attempt to restore abundant details of the environment via observation models, it is difficult due to the environment's complexity and limited model capacity. On the other hand, reward models, while dominating implicit MBRL and adept at learning compact task-centric dynamics, are inadequate for sample-efficient learning without richer learning signals. Motivated by these insights and discoveries, we propose a simple yet effective approach, HarmonyDream, which automatically adjusts loss coefficients to maintain task harmonization, i.e. a dynamic equilibrium between the two tasks in world model learning. Our experiments show that the base MBRL method equipped with HarmonyDream gains 10%-69% absolute performance boosts on visual robotic tasks and sets a new state-of-the-art result on the Atari 100K benchmark. Code is available at https://github.com/thuml/HarmonyDream.Comment: ICML 2024. Code is available at https://github.com/thuml/HarmonyDrea

Research on bionic composite guidance law considering field of view angle

Due to the use of strapdown seeker in small missiles, a small field of view angle is required to ensure effective tracking and strike of the target during the final interception. Based on the tracking strategy of dragonfly chasing targets, a composite guidance law is studied. In the initial guidance section, the parallax angle is controlled by the sliding mode control law to adjust the missile to the tail following attitude. The final guidance section used the motion camouflage guidance law with the focus at infinity for target tracking,and between the initial guidance and the final guidance. The second-order smooth interface law is used for the transition. The simulation results show that compared with the traditional proportional guidance law, the required overload of the missile in the final guidance is small,and the target is closer to the center of the field of view, which can reduce the missile in the final guidance. The overload and the field of view of the seeker can be used to effectively improve the attack accuracy

Global trends in COVID-19 Alzheimer's related research: a bibliometric analysis

BackgroundThe COVID-19 pandemic has significantly impacted public health, putting people with Alzheimer's disease at significant risk. This study used bibliometric analysis method to conduct in-depth research on the relationship between COVID-19 and Alzheimer's disease, as well as to predict its development trends.MethodsThe Web of Science Core Collection was searched for relevant literature on Alzheimer's and Coronavirus-19 during 2019–2023. We used a search query string in our advanced search. Using Microsoft Excel 2021 and VOSviewer software, a statistical analysis of primary high-yield authors, research institutions, countries, and journals was performed. Knowledge networks, collaboration maps, hotspots, and regional trends were analyzed using VOSviewer and CiteSpace.ResultsDuring 2020–2023, 866 academic studies were published in international journals. United States, Italy, and the United Kingdom rank top three in the survey; in terms of productivity, the top three schools were Harvard Medical School, the University of Padua, and the University of Oxford; Bonanni, Laura, from Gabriele d'Annunzio University (Italy), Tedeschi, Gioacchino from the University of Campania Luigi Vanvitelli (Italy), Vanacore, Nicola from Natl Ctr Dis Prevent and Health Promot (Italy), Reddy, P. Hemachandra from Texas Tech University (USA), and El Haj, Mohamad from University of Nantes (France) were the authors who published the most articles; The Journal of Alzheimer's Disease is the journals with the most published articles; “COVID-19,” “Alzheimer's disease,” “neurodegenerative diseases,” “cognitive impairment,” “neuroinflammation,” “quality of life,” and “neurological complications” have been the focus of attention in the last 3 years.ConclusionThe disease caused by the COVID-19 virus infection related to Alzheimer's disease has attracted significant attention worldwide. The major hot topics in 2020 were: “Alzheimer' disease,” COVID-19,” risk factors,” care,” and “Parkinson's disease.” During the 2 years 2021 and 2022, researchers were also interested in “neurodegenerative diseases,” “cognitive impairment,” and “quality of life,” which require further investigation

Ethyl Pyruvate Attenuates CaCl2-Induced Tubular Epithelial Cell Injury by Inhibiting Autophagy and Inflammatory Responses

Background/Aims: Nephrolithiasis is one of the most prevalent diseases of the urinary system. Approximately 80% of human kidney stones are composed of calcium oxalate (CaOx), and hypercalciuria is one of the most common metabolic disorders. Emerging evidence indicates that autophagy and inflammatory responses are related to the formation of CaOx nephrolithiasis. However, the roles of autophagy and inflammation in patients with hypercalciuria remain unclear. Ethyl pyruvate (EP) displays protective effects in experimental models of many illnesses. In this study, we investigated the protective effects of EP in vitro through its inhibition of autophagy and inflammatory responses after CaCl2-induced tubular epithelial cell injury. Methods: First, we cultured human tubular epithelial (HK-2) cells in the presence of various concentrations of CaCl2 (0, 0.1, 0.25, 0.5, 1.0, 1.5, and 2.0 mg/ml) for 12 h and EP (0, 1.0, 2.5, 5.0, and 10.0 mM) for 2 h to select the optimum concentration using the Cell Counting Kit-8 assay and lactate dehydrogenase (LDH) assay. Cells in culture were stimulated with CaCl2 (1.0 mg/ml, 12 h) with or without EP pretreatment (2.5 mM, 2 h). After the exposure, we detected the expression of inflammation-related proteins using an enzyme-linked immunosorbent assay and Western blot analysis. Finally, the levels of autophagy-related proteins were determined through Western blot analysis, and the number of GFP-LC3 dots and autophagic vacuoles was detected under confocal microscopy. Results: With the use of the Cell Counting Kit-8 assay and the LDH assay, we identified the optimum concentration for CaCl2 (1.0 mg/ml) treatment and EP pretreatment (2.5 mM). Our research indicated that CaCl2 can induce autophagy and inflammatory responses in HK-2 cells. Furthermore, treatment with EP prior to CaCl2 stimulation attenuated HK-2 cell injury by inhibiting autophagy and inflammation. Conclusion: Our results provide evidence that EP attenuates CaCl2-induced injury of HK-2 cells by downregulating the expression of inflammation and autophagy proteins that may be associated with the inhibition of the high-mobility group box-1 (HMGB1)/toll-like receptor 4 (TLR4)/NF-κB pathway and the competitive interaction with Beclin-1 of HMGB1

EVALUATING A SOLID-PHASE EXTRACTION METHOD WITH NOVEL POROUS CYCLODEXTRIN POLYMERS

Organic micropollutants (MPs) occur ubiquitously in the aquatic environment at trace concentrations, which presents great challenges for environmental monitoring. Solid-phase extraction (SPE) is a widely-used sample preparation procedure that concentrates MPs in environmentally derived water samples. SPE relies on columns packed with an adsorbent material that captures MPs from water samples. Loaded SPE adsorbents can then be eluted with organic solvents to release the captured MPs. The conventional adsorbent used for SPE is a hydrophilic-lipophilic balanced material available from a variety of commercial vendors, often referred to as HLB. These HLB adsorbents feature stability at extreme pHs and high retention of polar and apolar organic MPs. The primary disadvantage of HLB adsorbent materials is price, which often makes sample preparation the most expensive step in an environmental monitoring workflow. In this research, novel porous β-cyclodextrin polymers (P-CDP) were evaluated as an alternative SPE adsorbent. Cyclodextrins are sustainably produced macrocycles of glucose, featuring a hydrophobic interior cavity that forms host-guest complexes with thousands of organic molecules. P-CDP is a polymer of cyclodextrin and is synthesized in one-step, making it relatively inexpensive to produce. The objective of this research was to develop an SPE procedure using P-CDP and compare its performance to a conventional SPE procedure using HLB. A set of 189 MPs were included in the study and the P-CDP method was optimized to maximize efficiency in MP capture and MP release. The optimized P-CDP method exhibits moderate absolute recovery (≥60%) for 135 (75%) MPs and high absolute recovery (≥80%) for 121 (67%) MPs. The conventional HLB method exhibits moderate absolute recovery for 130 (72%) MPs and high absolute recovery for 109 (61%) MPs. The results of this research demonstrate that P-CDP could be used as a cost-effective SPE adsorbent