The Global Maximum Principle for Optimal Control of Partially Observed Stochastic Systems Driven by Fractional Brownian Motion

In this paper we study the stochastic control problem of partially observed (multi-dimensional) stochastic system driven by both Brownian motions and fractional Brownian motions. In the absence of the powerful tool of Girsanov transformation, we introduce and study new stochastic processes which are used to transform the original problem to a "classical one". The adjoint backward stochastic differential equations and the necessary condition satisfied by the optimal control (maximum principle) are obtained.Comment: 30 page

HIV-1 genetic diversity a challenge for AIDS vaccine development: A retrospective bibliometric analysis

Background: Despite recent advances in human immunodeficiency virus-1 (HIV-1) prevention, a fast, safe, and effective vaccine will probably be necessary to end the HIV/AIDS pandemic. This study was conducted to evaluate global research trends and map the key bibliometric indices in HIV-1 genetic diversity from 1998 to 2021.Methods: A comprehensive online search was conducted in the Web of Science Core Collection database to retrieve published literature on HIV-1 genetic diversity. Key bibliometric indicators were calculated and evaluated using HistCiteTM, Bibliometrix: An R-tool, and VOSviewer software for windows.Results: A total of 2,060 documents written by 9,201 authors and published in 250 journals were included in the final analysis. Year 2012 was the most productive year with 121 (5.87%) publications. The most prolific author was Shao Yiming (n = 74, 3.59%) from Chinese Center for Disease Control and Prevention. The United States of America was the highly contributing and influential country (n = 681, 33.05%). AIDS Research and Human Retroviruses was the most productive journal (n = 562, 27.2%). Network visualization shows that HIV-1 was the most widely used author keyword.Conclusion: This study provides global research trends and detailed information on HIV-1 genetic diversity. The amount of scientific literature on HIV-1 genetic diversity research has rapidly increased in the last two decades. The maximum number of articles on HIV-1 genetic diversity was published in developed countries; therefore, a scientific research collaboration among researchers and institutes in low-income countries should be promoted and supported

Self-supervised pretraining improves the performance of classification of task functional magnetic resonance imaging

IntroductionDecoding brain activities is one of the most popular topics in neuroscience in recent years. And deep learning has shown high performance in fMRI data classification and regression, but its requirement for large amounts of data conflicts with the high cost of acquiring fMRI data.MethodsIn this study, we propose an end-to-end temporal contrastive self-supervised learning algorithm, which learns internal spatiotemporal patterns within fMRI and allows the model to transfer learning to datasets of small size. For a given fMRI signal, we segmented it into three sections: the beginning, middle, and end. We then utilized contrastive learning by taking the end-middle (i.e., neighboring) pair as the positive pair, and the beginning-end (i.e., distant) pair as the negative pair.ResultsWe pretrained the model on 5 out of 7 tasks from the Human Connectome Project (HCP) and applied it in a downstream classification of the remaining two tasks. The pretrained model converged on data from 12 subjects, while a randomly initialized model required 100 subjects. We then transferred the pretrained model to a dataset containing unpreprocessed whole-brain fMRI from 30 participants, achieving an accuracy of 80.2 ± 4.7%, while the randomly initialized model failed to converge. We further validated the model’s performance on the Multiple Domain Task Dataset (MDTB), which contains fMRI data of 26 tasks from 24 participants. Thirteen tasks of fMRI were selected as inputs, and the results showed that the pre-trained model succeeded in classifying 11 of the 13 tasks. When using the 7 brain networks as input, variations of the performance were observed, with the visual network performed as well as whole brain inputs, while the limbic network almost failed in all 13 tasks.DiscussionOur results demonstrated the potential of self-supervised learning for fMRI analysis with small datasets and unpreprocessed data, and for analysis of the correlation between regional fMRI activity and cognitive tasks

Ferroelectricity in layered bismuth oxide down to 1 nanometer

Atomic-scale ferroelectrics are of great interest for high-density electronics, particularly field-effect transistors, low-power logic, and nonvolatile memories. We devised a film with a layered structure of bismuth oxide that can stabilize the ferroelectric state down to 1 nanometer through samarium bondage. This film can be grown on a variety of substrates with a cost-effective chemical solution deposition. We observed a standard ferroelectric hysteresis loop down to a thickness of ~1 nanometer. The thin films with thicknesses that range from 1 to 4.56 nanometers possess a relatively large remanent polarization from 17 to 50 microcoulombs per square centimeter. We verified the structure with first-principles calculations, which also pointed to the material being a lone pair-driven ferroelectric material. The structure design of the ultrathin ferroelectric films has great potential for the manufacturing of atomic-scale electronic devices.This work was supported by the National Key Research and Development Program of China (2018YFA0703700, 2017YFE0119700, and 2020YFA0406202), the National Natural Science Foundation of China (21801013, 51774034, 51961135107, 62104140, 12175235, 22090042, 12074016, 11704041, and 12274009), the Fundamental Research Funds for the Central Universities (FRF-IDRY-19-007 and FRF-TP-19-055A2Z), the National Program for Support of Top-notch Young Professionals, the Young Elite Scientists Sponsorship Program by CAST (2019-2021QNRC), and Lingang Laboratory Open Research Fund (grant LG-QS-202202-11). Use of the Beijing Synchrotron Radiation Facility (1W1A beamlines, China) of the Chinese Academy of Sciences is acknowledged. Y.-W.F. acknowledges the support of Masaki Azuma’s group during his stay at the Tokyo Institute of Technology. Y.L. acknowledges the support of the Beijing Innovation Team Building Program (grant no. IDHT20190503), the Beijing Natural Science Foundation (Z210016), the Research and Development Project from the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering (2022SX-TD001), and the General Program of Science and Technology Development Project of Beijing Municipal Education Commission (KM202110005003).Peer reviewe

Concurrent Challenges: Military and Diplomatic Connections between the U.S Civil War and Taiping Rebellion

Despite the vast research done on the topic of U.S Civil War, and extensive studies on the Taiping Rebellion in China, little is known about the international connections between these two devastating conflicts. When the U.S Civil war was fought from 1861-1865, the calamitous Taiping Rebellion in China also entered its brutal final years. These two civil wars are both the result of severe internal divisions, are similar in military strategies, international engagements and diplomatic interactions. This study focuses on both the military and diplomatic history during wartime: the first part of military history will explore how the wars are fought from 1861-1865, through a few major battles and important figures in the wars; the second part will mainly focus on two Americans, Anson Burlingame and Ulysses Grant, who both actively engaged in the effort of improving Sino-U.S relations. Using primary accounts and government documents from both governments, the analysis and comparison of these two civil wars yield the conclusion that these wars were seen as concurrent challenges by both countries, and they became a shared experience of devastation between China and the U.S, while the viable diplomacies on both sides created a solidarity that helped America and China to establish cordial relations and closer ties

The Role of Vocational Education in the Integration of Culture and Tourism in the Information Age and Its Implementation Paths

This paper constructs the coupling logic of the two systems of vocational education and cultural tourism with the joint action of external and internal driving forces. It contributes to the coupling of the two systems through the synergistic relationship of same-frequency resonance and applies dimensionless processing to data checking and data cleaning of vocational education data. The coupling coordination development level of vocational education and the cultural tourism industry can be measured using the modified coupling coordination degree model. An empirical study of the coupling coordination degree of vocational education and cultural tourism industry in Province G is conducted using the entropy value method. The results show that the coupling and coordination degree of vocational education and cultural tourism system in province G shows a decreasing trend from 2013 to 2019, and the coupling and coordination degree between the development level of the cultural tourism industry and vocational education gradually rises to 0.658388 in 2022 after 2019, and the interaction between the two is gradually obvious. The integration of industry and vocational education in cultural tourism is promoted by this paper through valuable references and drawable ideas

Experimental and Numerical Study of a Rebar-Prestressed Cylinder Concrete Pipe (RPCCP) under Internal Load

In order to study the load-bearing failure characteristics of a RPCCP under internal load, a field prototype test was designed, and a finite element model was established. An internal load was applied up to 2.0 MPa step by step and the force variation law of each part was obtained. During the production of the RPCCP, by wrapping prestressed steel bars around the concrete core with a cylinder, the core was subjected to an initial precompression stress. In the loading process, the protective cover cracked first, from where the concrete core gradually changed from the initial compression state to a tension state, finally cracking from the inner and outer diameter. The stresses of the cylinder and steel bars increased steadily with the internal load and did not yield. The finite element calculation results were in good agreement with the test results, and the influence characteristics of the tension control stress of the steel bar and the concrete strength on the failure of the RPCCP under internal load were discussed. The results showed that the internal load of the protective cover was independent of the tension control stress, but decreases with a decrease in concrete strength, while the load corresponding to the concrete core entering plasticity is related to the tension control stress and the concrete strength, and the relationships were basically linear

OTNet: A Small Object Detection Algorithm for Video Inspired by Avian Visual System

Small object detection is one of the most challenging and non-negligible fields in computer vision. Inspired by the location–focus–identification process of the avian visual system, we present our location-focused small-object-detection algorithm for video or image sequence, OTNet. The model contains three modules corresponding to the forms of saliency, which drive the strongest response of OT to calculate the saliency map. The three modules are responsible for temporal–spatial feature extraction, spatial feature extraction and memory matching, respectively. We tested our model on the AU-AIR dataset and achieved up to 97.95% recall rate, 85.73% precision rate and 89.94 F1 score with a lower computational complexity. Our model is also able to work as a plugin module for other object detection models to improve their performance in bird-view images, especially for detecting smaller objects. We managed to improve the detection performance by up to 40.01%. The results show that our model performs well on the common metrics on detection, while simulating visual information processing for object localization of the avian brain

Numerical simulation of mechanism of high-pressure air injection (HPAI) in light oil reservoirs

Based on the research progress of the crude oil oxidation-combustion model proposed by predecessors, this paper established a new multi-reaction model for high-pressure air injection (HPAI) process to compare the HPAI performance in reservoirs without water injection and high water cut reservoirs by numerical simulation. Results show that gas override is universal in air injection in light oil reservoirs before and after waterflooding, and is more apparent in strongly heterogeneous reservoirs. However, the produced oxygen concentration is very low all the time. For reservoirs that haven't gone through water injection, at high air injection rate oil is very likely to auto-ignite and keep high peak temperature and long time stable combustion front. However, there exists a critical value for the influence of air injection rate on the combustion front moving speed, above the critical value, oil recover factor increment is not obvious with the increase of air injection rate. At the same air injection rate, high water cut reservoirs are 6.3% lower in recovery factor than reservoirs without water injection, With high increase in GOR and high water recovery degree during HPAI process. It is suggested that polymer gel/ and or foam assisted air injection be taken to reduce GOR/ and or water cut in production wells. Key words: air injection, light oil reservoirs, reservoirs without water injection, high water cut reservoir, gas override, numerical simulation, mechanism stud